Final Year IEEE Project 2013-2014  - Networking Project Title and Abstract
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Final Year IEEE Project 2013-2014 - Networking Project Title and Abstract



Final Year IEEE Project 2013-2014 - Networking Project Title and Abstract

Final Year IEEE Project 2013-2014 - Networking Project Title and Abstract



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Final Year IEEE Project 2013-2014  - Networking Project Title and Abstract Final Year IEEE Project 2013-2014 - Networking Project Title and Abstract Document Transcript

  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, 13 Years of Experience Automated Services 24/7 Help Desk Support Experience & Expertise Developers Advanced Technologies & Tools Legitimate Member of all Journals Having 1,50,000 Successive records in all Languages More than 12 Branches in Tamilnadu, Kerala & Karnataka. Ticketing & Appointment Systems. Individual Care for every Student. Around 250 Developers & 20 Researchers
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, 227-230 Church Road, Anna Nagar, Madurai – 625020. 0452-4390702, 4392702, + 91-9944793398., S.P.Towers, No.81 Valluvar Kottam High Road, Nungambakkam, Chennai - 600034. 044-42072702, +91-9600354638, 15, III Floor, SI Towers, Melapudur main Road, Trichy – 620001. 0431-4002234, + 91-9790464324. 577/4, DB Road, RS Puram, Opp to KFC, Coimbatore – 641002 0422- 4377758, +91-9677751577.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Plot No: 4, C Colony, P&T Extension, Perumal puram, Tirunelveli- 627007. 0462-2532104, +919677733255, 1st Floor, A.R.IT Park, Rasi Color Scan Building, Ramanathapuram - 623501. 04567-223225, 74, 2nd floor, K.V.K Complex,Upstairs Krishna Sweets, Mettur Road, Opp. Bus stand, Erode-638 011. 0424-4030055, +91- 9677748477 No: 88, First Floor, S.V.Patel Salai, Pondicherry – 605 001. 0413– 4200640 +91-9677704822 TNHB A-Block,, Opp: Hotel Ganesh Near Busstand. Salem – 636007, 0427-4042220, +91-9894444716.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, ETPL MC-001 Network-Assisted Mobile Computing with Optimal Uplink Query Processing Abstract: Many mobile applications retrieve content from remote servers via user generated queries. Processing these queries is often needed before the desired content can be identified. Processing the request on the mobile devices can quickly sap the limited battery resources. Conversely, processing user queries at remote servers can have slow response times due communication latency incurred during transmission of the potentially large query. We evaluate a network-assisted mobile computing scenario where mid-network nodes with “leasing” capabilities are deployed by a service provider. Leasing computation power can reduce battery usage on the mobile devices and improve response times. However, borrowing processing power from mid-network nodes comes at a leasing cost which must be accounted for when making the decision of where processing should occur. We study the tradeoff between battery usage, processing and transmission latency, and mid-network leasing. We use the dynamic programming framework to solve for the optimal processing policies that suggest the amount of processing to be done at each mid-network node in order to minimize the processing and communication latency and processing costs. Through numerical studies, we examine the properties of the optimal processing policy and the core tradeoffs in such systems. ETPL MC-002 Predicting Human Movement Based on Telecom's Handoff in Mobile Networks Abstract: Investigating human movement behavior is important for studying issues such as prediction of vehicle traffic and spread of contagious diseases. Since mobile telecom network can efficiently monitor the movement of mobile users, the telecom's mobility management is an ideal mechanism for studying human movement issues. The problem can be abstracted as follows: What is the probability that a person at location A will move to location B after T hours. The answer cannot be directly obtained because commercial telecom networks do not exactly trace the movement history of every mobile user. In this paper, we show how to use the standard outputs (handover rates, call arrival rates, call holding time, and call traffic) measured in a mobile telecom network to derive the answer for this problem. ETPL MC-003 Modeling and Restraining Mobile Virus Propagation Abstract: Viruses and malwares can spread from computer networks into mobile networks with the rapid growth of smart cellphone users. In a mobile network, viruses and malwares can cause privacy data leakage, extra charges, and remote listening. Furthermore, they can jam wireless servers by sending thousands of spam messages or track user positions through GPS. Because of the potential damages of mobile viruses, it is important for us to gain a deep understanding of the propagation mechanisms of mobile viruses. In this paper, we propose a two-layer network model for simulating virus propagation through both Bluetooth and SMS. Different from previous work, our work addresses the impacts of human behaviors, i.e., operational behavior and mobile behavior, on virus propagation. Our simulation results provide further insights into the determining factors of virus propagation in mobile networks. Moreover, we examine two strategies for restraining mobile virus propagation, i.e., preimmunization and adaptive dissemination strategies drawing on the methodology of autonomy-oriented computing (AOC). The experimental results show that our strategies can effectively protect large-scale and/or highly dynamic mobile networks. ETPL MC-004 Mobile Relay Configuration in Data-Intensive Wireless Sensor Networks
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: Wireless Sensor Networks (WSNs) are increasingly used in data-intensive applications such as microclimate monitoring, precision agriculture, and audio/video surveillance. A key challenge faced by data-intensive WSNs is to transmit all the data generated within an application's lifetime to the base station despite the fact that sensor nodes have limited power supplies. We propose using low-cost disposable mobile relays to reduce the energy consumption of data-intensive WSNs. Our approach differs from previous work in two main aspects. First, it does not require complex motion planning of mobile nodes, so it can be implemented on a number of low-cost mobile sensor platforms. Second, we integrate the energy consumption due to both mobility and wireless transmissions into a holistic optimization framework. Our framework consists of three main algorithms. The first algorithm computes an optimal routing tree assuming no nodes can move. The second algorithm improves the topology of the routing tree by greedily adding new nodes exploiting mobility of the newly added nodes. The third algorithm improves the routing tree by relocating its nodes without changing its topology. This iterative algorithm converges on the optimal position for each node given the constraint that the routing tree topology does not change. We present efficient distributed implementations for each algorithm that require only limited, localized synchronization. Because we do not necessarily compute an optimal topology, our final routing tree is not necessarily optimal. However, our simulation results show that our algorithms significantly outperform the best existing solutions. ETPL MC-005 Optimal Content Downloading in Vehicular Networks Abstract: We consider a system where users aboard communication-enabled vehicles are interested in downloading different contents from Internet-based servers. This scenario captures many of the infotainment services that vehicular communication is envisioned to enable, including news reporting, navigation maps, and software updating, or multimedia file downloading. In this paper, we outline the performance limits of such a vehicular content downloading system by modeling the downloading process as an optimization problem, and maximizing the overall system throughput. Our approach allows us to investigate the impact of different factors, such as the roadside infrastructure deployment, the vehicle-to-vehicle relaying, and the penetration rate of the communication technology, even in presence of large instances of the problem. Results highlight the existence of two operational regimes at different penetration rates and the importance of an efficient, yet 2-hop constrained, vehicle-to-vehicle relaying. ETPL MC-006 A Scalable Server Architecture for Mobile Presence Services in Social Network Applications Abstract: Social network applications are becoming increasingly popular on mobile devices. A mobile presence service is an essential component of a social network application because it maintains each mobile user's presence information, such as the current status (online/offline), GPS location and network address, and also updates the user's online friends with the information continually. If presence updates occur frequently, the enormous number of messages distributed by presence servers may lead to a scalability problem in a large-scale mobile presence service. To address the problem, we propose an efficient and scalable server architecture, called PresenceCloud, which enables mobile presence services to support large-scale social network applications. When a mobile user joins a network, PresenceCloud searches for the presence of his/her friends and notifies them of his/her arrival. PresenceCloud organizes presence servers into a quorum-based server-to-server architecture for efficient presence searching. It also leverages a directed search algorithm and a one-hop caching strategy to achieve small constant search latency. We analyze the performance of PresenceCloud in terms of the search cost and search satisfaction level. The search cost is defined as the total number of messages generated by the presence server when a user arrives; and search satisfaction level is defined as the time it takes to search for the arriving user's friend list. The results of simulations demonstrate that PresenceCloud achieves performance gains in the search cost without compromising search satisfaction.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, ETPL MC-007 Content Sharing over Smartphone-Based Delay-Tolerant Networks Abstract: With the growing number of smartphone users, peer-to-peer ad hoc content sharing is expected to occur more often. Thus, new content sharing mechanisms should be developed as traditional data delivery schemes are not efficient for content sharing due to the sporadic connectivity between smartphones. To accomplish data delivery in such challenging environments, researchers have proposed the use of store-carry-forward protocols, in which a node stores a message and carries it until a forwarding opportunity arises through an encounter with other nodes. Most previous works in this field have focused on the prediction of whether two nodes would encounter each other, without considering the place and time of the encounter. In this paper, we propose discover-predict-deliver as an efficient content sharing scheme for delay-tolerant smartphone networks. In our proposed scheme, contents are shared using the mobility information of individuals. Specifically, our approach employs a mobility learning algorithm to identify places indoors and outdoors. A hidden Markov model is used to predict an individual's future mobility information. Evaluation based on real traces indicates that with the proposed approach, 87 percent of contents can be correctly discovered and delivered within 2 hours when the content is available only in 30 percent of nodes in the network. We implement a sample application on commercial smartphones, and we validate its efficiency to analyze the practical feasibility of the content sharing application. Our system approximately results in a 2 percent CPU overhead and reduces the battery lifetime of a smartphone by 15 percent at most. ETPL MC-008 Efficient Spread Spectrum Communication without Preshared Secrets Abstract: Spread spectrum (SS) communication relies on the assumption that some secret is shared beforehand among communicating nodes to establish the spreading sequence for long-term wireless communication. Strasser et al. identified this as the circular dependency problem (CDP). This problem is exacerbated in large networks, where nodes join and leave the network frequently, and preconfiguration of secrets through physical contact is infeasible. In this work, we introduce an efficient and adversary- resilient secret sharing mechanism based on two novel paradigms (intractable forward decoding, efficient backward decoding) called Time Reversed Message Extraction and Key Scheduling (TREKS) that enables SS communication without preshared secrets. TREKS is four orders of magnitude faster than previous solutions to the CDP. Furthermore, our approach can be used to operate long-term SS communication without establishing any keys. The energy cost under TREKS is provably optimal with minimal storage overhead, and computation cost at most twice that of traditional SS. We evaluate TREKS through simulation and empirically using an experimental testbed consisting of USRP, GNU Radio, and GPU-equipped nodes. Using TREKS under a modest hardware setup, we can sustain a 1--Mbps long-term SS communication spread by a factor of 100 (i.e., 100 Megachips per second) over a 200-MHz bandwidth in real time. ETPL MC-009 VAPR: Void-Aware Pressure Routing for Underwater Sensor Networks Abstract: Underwater mobile sensor networks have recently been proposed as a way to explore and observe the ocean, providing 4D (space and time) monitoring of underwater environments. We consider a specialized geographic routing problem called pressure routing that directs a packet to any sonobuoy on the surface based on depth information available from on-board pressure gauges. The main challenge of pressure routing in sparse underwater networks has been the efficient handling of 3D voids. In this respect, it was recently proven that the greedy stateless perimeter routing method, very popular in 2D networks, cannot be extended to void recovery in 3D networks. Available heuristics for 3D void recovery require expensive flooding. In this paper, we propose a Void-Aware Pressure Routing (VAPR) protocol that uses sequence number, hop count and depth information embedded in periodic beacons to set up
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, next-hop direction and to build a directional trail to the closest sonobuoy. Using this trail, opportunistic directional forwarding can be efficiently performed even in the presence of voids. The contribution of this paper is twofold: 1) a robust soft-state routing protocol that supports opportunistic directional forwarding; and 2) a new framework to attain loop freedom in static and mobile underwater networks to guarantee packet delivery. Extensive simulation results show that VAPR outperforms existing solutions. ETPL MC-010 Underwater Localization with Time-Synchronization and Propagation Speed Uncertainties Abstract: Underwater acoustic localization (UWAL) is a key element in most underwater communication applications. The absence of GPS as well as the signal propagation environment makes UWAL similar to indoor localization. However, UWAL poses additional challenges. The propagation speed varies with depth, temperature, and salinity, anchor and unlocalized (UL) nodes cannot be assumed time- synchronized, and nodes are constantly moving due to ocean currents or self-motion. Taking these specific features of UWAL into account, in this paper, we describe a new sequential algorithm for joint time-synchronization and localization for underwater networks. The algorithm is based on packet exchanges between anchor and UL nodes, makes use of directional navigation systems employed in nodes to obtain accurate short-term motion estimates, and exploits the permanent motion of nodes. Our solution also allows self-evaluation of the localization accuracy. Using simulations, we compare our algorithm to two benchmark localization methods as well as to the Cramér -Rao bound (CBR). The results demonstrate that our algorithm achieves accurate localization using only two anchor nodes and outperforms the benchmark schemes when node synchronization and knowledge of propagation speed are not available. Moreover, we report results of a sea trial where we validated our algorithm in open sea. ETPL MC-011 Joint Optimal Sensor Selection and Scheduling in Dynamic Spectrum Access Networks Abstract: Spectrum sensing is key to the realization of dynamic spectrum access. To protect primary users' communications from the interference caused by secondary users, spectrum sensing must meet the strict detectability requirements set by regulatory bodies, such as the FCC. Such strict detection requirements, however, can hardly be achieved using PHY-layer sensing techniques alone with one-time sensing by only a single sensor. In this paper, we jointly exploit two MAC-layer sensing methods—cooperative sensing and sensing scheduling— to improve spectrum sensing performance, while incurring minimum sensing overhead. While these sensing methods have been studied individually, little has been done on their combinations and the resulting benefits. Specifically, we propose to construct a profile of the primary signal's RSSs and design a simple, yet near-optimal, incumbent detection rule. Based on this constructed RSS profile, we develop an algorithm to find 1) an optimal set of sensors; 2) an optimal point at which to stop scheduling additional sensing; and 3) an optimal sensing duration for one-time sensing, so as to make a tradeoff between detection performance and sensing overhead. Our evaluation results show that the proposed sensing algorithms reduce the sensing overhead by up to 65 percent, while meeting the requirements of both false-alarm and misdetection probabilities of less than 0.01. ETPL MC-012 Evaluating Implementation Strategies for Location-Based Multicast Addressing Abstract: Location-based multicast addressing (LMA) yields an important building block for context- aware applications in mobile ad hoc networks (MANETs). In LMA, messages are routed based on their content as well as on the location of the sending and the receiving nodes. The same dynamism that motivates locations as part of the addressing mechanism for multicast applications in MANETs, makes such a multicast challenging to implement both efficiently and reliably across application scenarios. Different implementation strategies have been proposed in literature for abstractions similar to LMA,
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, motivated and validated by specific applications. The goal of this paper is to devise specific implementation strategies for LMA and compare these strategies in the context of several application scenarios, in order to aid in the selection of a scheme for a given application. To that end, we first detail three algorithms for implementing LMA. The first, message-centric, strategy uses geographically scoped gossiping to propagate messages. The second, query-centric, strategy propagates queries of receivers to subsequently route messages. The third, hybrid, strategy strives for the best of both worlds through a restricted multicasting of both messages and queries. We compare these algorithms both analytically and empirically. We pinpoint differences and break-even points among the approaches based on communication patterns, contrasting our findings with common expectations and our analysis. Our evaluations show that the hybrid approach invariably outperforms at least one of the other approaches, making it a safe choice for settings with varying or unknown communication patterns. ETPL MC-013 Cooperative Packet Delivery in Hybrid Wireless Mobile Networks: A Coalitional Game Approach Abstract: We consider the problem of cooperative packet delivery to mobile nodes in a hybrid wireless mobile network, where both infrastructure-based and infrastructure-less (i.e., ad hoc mode or peer-to-peer mode) communications are used. We propose a solution based on a coalition formation among mobile nodes to cooperatively deliver packets among these mobile nodes in the same coalition. A coalitional game is developed to analyze the behavior of the rational mobile nodes for cooperative packet delivery. A group of mobile nodes makes a decision to join or to leave a coalition based on their individual payoffs. The individual payoff of each mobile node is a function of the average delivery delay for packets transmitted to the mobile node from a base station and the cost incurred by this mobile node for relaying packets to other mobile nodes. To find the payoff of each mobile node, a Markov chain model is formulated and the expected cost and packet delivery delay are obtained when the mobile node is in a coalition. Since both the expected cost and packet delivery delay depend on the probability that each mobile node will help other mobile nodes in the same coalition to forward packets to the destination mobile node in the same coalition, a bargaining game is used to find the optimal helping probabilities. After the payoff of each mobile node is obtained, we find the solutions of the coalitional game which are the stable coalitions. A distributed algorithm is presented to obtain the stable coalitions and a Markov- chain-based analysis is used to evaluate the stable coalitional structures obtained from the distributed algorithm. Performance evaluation results show that when the stable coalitions are formed, the mobile nodes achieve a nonzero payoff (i.e., utility is higher than the cost). With a coalition formation, the mobile nodes achieve higher payoff than that when each mobile node acts alone. ETPL MC-014 An Investigation on LTE Mobility Management Abstract: Mobility management in Long Term Evolution (LTE) is different from that in the third generation mobile telecom networks. In LTE, the Mobility Management Entity (MME) is responsible for the mobility management function. The MME is connected to a large number of evolved Node Bs (cells) that are grouped into the Tracking Areas (TAs). The TAs are further grouped into TA Lists (TALs). When a User Equipment (UE) moves out of the current TAL, it reports its new location to the MME. If the LTE network attempts to connect to the UE, the MME asks the cells in the TAL to page the UE. In LTE paging, the MME may sequentially page a cell, the TA of the cell, and/or the TAL of the cell. This paper investigates the performance of LTE paging, and provides the guidelines for the best paging sequence of cells. ETPL MC-015 Bounded-Hop Energy-Efficient Liveness of Flocking Swarms
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: In this paper, we consider a set of n mobile wireless nodes, which have no information about each other. The only information a single node holds is its current location and future mobility plan. We develop a two-phase distributed self-stabilizing scheme for producing a bounded hop-diameter communication graph. In the first phase, nodes construct a temporary underlying topology and disseminate their current location and mobility plans. This is followed by a second phase, in which nodes construct the desired topology under two modes: static and dynamic. The static mode provides a fixed topology which does not change in spite of node movements; the dynamic mode allows the topology to change; however, the hop-diameter remains the same. We provide an O(λ,λ2)-bicriteria approximation (in terms of total energy consumption and network lifetime, respectively) algorithm in the static mode: for an input parameter λ, we construct a static h-bounded hop communication graph, where h=n/λ + log λ. In the dynamic mode, given a parameter h, we construct an optimal (in terms of network lifetime) h-bounded hop communication graph when every node moves with constant speed in a single direction along a straight line during each time interval. Our results are validated through extensive simulations. ETPL MC-016 A General Performance Evaluation Framework for Network Selection Strategies in 3G-WLAN Interworking Networks Abstract: In this work, we investigate a general performance evaluation framework for network selection strategies (NSSs) that are used in 3G-WLAN interworking networks. Instead of simulation, this framework is based on models of NSSs and is constructed using a stochastic process algebra, named Performance Evaluation Process Algebra (PEPA). It captures the traffic and mobility characteristics of mobile nodes in 3G-WLAN interworking networks and has a good expression of the behavior of the mobile nodes using different NSSs. Commonly used NSSs are evaluated from the perspectives of average throughput, handover rate, and network blocking probability. Results of the evaluation explore the effect of these NSSs on both mobile nodes and networks, as well as their characteristics in different mobility and traffic scenarios. ETPL MC-017 Relay Selection for Geographical Forwarding in Sleep-Wake Cycling Wireless Sensor Networks Abstract: Our work is motivated by geographical forwarding of sporadic alarm packets to a base station in a wireless sensor network (WSN), where the nodes are sleep-wake cycling periodically and asynchronously. We seek to develop local forwarding algorithms that can be tuned so as to tradeoff the end-to-end delay against a total cost, such as the hop count or total energy. Our approach is to solve, at each forwarding node enroute to the sink, the local forwarding problem of minimizing one-hop waiting delay subject to a lower bound constraint on a suitable reward offered by the next-hop relay; the constraint serves to tune the tradeoff. The reward metric used for the local problem is based on the end-to- end total cost objective (for instance, when the total cost is hop count, we choose to use the progress toward sink made by a relay as the reward). The forwarding node, to begin with, is uncertain about the number of relays, their wake-up times, and the reward values, but knows the probability distributions of these quantities. At each relay wake-up instant, when a relay reveals its reward value, the forwarding node's problem is to forward the packet or to wait for further relays to wake-up. In terms of the operations research literature, our work can be considered as a variant of the asset selling problem. We formulate our local forwarding problem as a partially observable Markov decision process (POMDP) and obtain inner and outer bounds for the optimal policy. Motivated by the computational complexity involved in the policies derived out of these bounds, we formulate an alternate simplified model, the optimal policy for which is a simple threshold rule. We provide simulation results to compare the performance of the inner and outer bound policies against the simple policy, and also against the optimal policy when the source knows the exact number of relays. Observing the good performance and the ease of implementation of the simple policy, we apply it to our motivating prob- em, i.e., local geographical routing of sporadic alarm packets in a large WSN. We compare the end-to-end performance (i.e., average total delay and average
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, total cost) obtained by the simple policy, when used for local geographical forwarding, against that obtained by the globally optimal forwarding algorithm proposed by Kim et al. ETPL MC-018 A Progressive Approach to Reducing Data Collection Latency in Wireless Sensor Networks with Mobile Elements Abstract: The introduction of mobile elements has created a new dimension to reduce and balance the energy consumption in wireless sensor networks. However, data collection latency may become higher due to the relatively slow travel speed of mobile elements. Thus, the scheduling of mobile elements, i.e., how they traverse through the sensing field and when they collect data from which sensor, is of ultimate importance and has attracted increasing attention from the research community. Formulated as the traveling salesman problem with neighborhoods (TSPN) and due to its NP-hardness, so far only approximation and heuristic algorithms have appeared in the literature, but the former only have theoretical value now due to their large approximation factors. In this paper, following a progressive optimization approach, we first propose a combine-skip-substitute (CSS) scheme, which is shown to be able to obtain solutions within a small range of the lower bound of the optimal solution. We then take the realistic multirate features of wireless communications into account, which have been ignored by most existing work, to further reduce the data collection latency with the multirate CSS (MR-CSS) scheme. Besides the correctness proof and performance analysis of the proposed schemes, we also show their efficiency and potentials for further extensions through extensive simulation. ETPL MC-019 On Using Interference-Aware Spectrum Sensing for Dynamic Spectrum Access in Cognitive Radio Networks Abstract: Spectrum sensing is an important step toward enabling dynamic spectrum access in cognitive radio networks. To ensure that primary users are properly protected while maximizing the performance of secondary users, most related work considers the metrics of probabilities of missed detection and false alarm for determining optimal spectrum sensing parameters. In this paper, we argue that spectrum sensing based entirely on the two metrics is unable to maximize spectrum utilization for dynamic spectrum access. We show that, to meet the requirement of the probability of missed detection, conventional spectrum sensing techniques can unnecessarily increase the probability of false alarm in scenarios with good spectrum reuse opportunity, thus lowering the ability to leverage spectrum holes. To address this problem, we define the probability of interference and propose a new metric for spectrum sensing to consider both the probabilities of interference and missed detection. We first investigate the problem of optimal spectrum hole discovery for a single secondary user based on the proposed metric, and then extend to the problem of cooperative spectrum sensing among a group of secondary users. Compared against conventional sensing techniques presented in related work, we show through simulations that interference-aware spectrum sensing can potentially result in better utilization of the spectrum by allowing the secondary user to maximize its transmission opportunity without sacrificing the desired degree of protection for primary users. ETPL MC-020 Joint Physical-Layer and System-Level Power Management for Delay-Sensitive Wireless Communications Abstract: We consider the problem of energy-efficient point-to-point transmission of delay-sensitive data (e.g., multimedia data) over a fading channel. Existing research on this topic utilizes either physical-layer centric solutions, namely power-control and adaptive modulation and coding (AMC), or system-level solutions based on dynamic power management (DPM); however, there is currently no rigorous and unified framework for simultaneously utilizing both physical-layer centric and system-level techniques to achieve the minimum possible energy consumption, under delay constraints, in the presence of stochastic and a priori unknown traffic and channel conditions. In this paper, we propose such a framework. We formulate the stochastic optimization problem as a Markov decision process (MDP) and solve it online
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, using reinforcement learning (RL). The advantages of the proposed online method are that 1) it does not require a priori knowledge of the traffic arrival and channel statistics to determine the jointly optimal power-control, AMC, and DPM policies; 2) it exploits partial information about the system so that less information needs to be learned than when using conventional reinforcement learning algorithms; and 3) it obviates the need for action exploration, which severely limits the adaptation speed and runtime performance of conventional reinforcement learning algorithms. Our results show that the proposed learning algorithms can converge up to two orders of magnitude faster than a state-of-the-art learning algorithm for physical layer power-control and up to three orders of magnitude faster than conventional reinforcement learning algorithms. ETPL MC-021 A Neighbor Coverage-Based Probabilistic Rebroadcast for Reducing Routing Overhead in Mobile Ad Hoc Networks Abstract: Due to high mobility of nodes in mobile ad hoc networks (MANETs), there exist frequent link breakages which lead to frequent path failures and route discoveries. The overhead of a route discovery cannot be neglected. In a route discovery, broadcasting is a fundamental and effective data dissemination mechanism, where a mobile node blindly rebroadcasts the first received route request packets unless it has a route to the destination, and thus it causes the broadcast storm problem. In this paper, we propose a neighbor coverage-based probabilistic rebroadcast protocol for reducing routing overhead in MANETs. In order to effectively exploit the neighbor coverage knowledge, we propose a novel rebroadcast delay to determine the rebroadcast order, and then we can obtain the more accurate additional coverage ratio by sensing neighbor coverage knowledge. We also define a connectivity factor to provide the node density adaptation. By combining the additional coverage ratio and connectivity factor, we set a reasonable rebroadcast probability. Our approach combines the advantages of the neighbor coverage knowledge and the probabilistic mechanism, which can significantly decrease the number of retransmissions so as to reduce the routing overhead, and can also improve the routing performance. ETPL MC-022 Mutual Distance Bounding Protocols Abstract: A distance bounding protocol enables one entity to determine an upper bound on the physical distance to the other entity as well as to authenticate the other entity. It has been actively researched during the recent years as distance-based attacks like Mafia fraud attacks become a threat in wireless environment, especially in RFID systems. Almost all distance bounding protocols deal with unilateral authentication as they consider authentication of a passive RFID tag to a reader. Recently, a distance bounding protocol providing mutual authentication has been proposed by Yum et al. asserting that it provides a lower false acceptance rate under Mafia fraud attack. However, we show in two ways that their security margins have been overestimated. First, we show that their analysis is not correct. Second, we introduce a new attack that achieves a higher false acceptance rate. Furthermore, we introduce a method that can modify existing distance bounding protocols with unilateral authentication to ones providing mutual authentication. ETPL MC-023 Resource Allocation with Flexible Channel Cooperation in Cognitive Radio Networks Abstract: We study the resource allocation problem in an OFDMA-based cooperative cognitive radio network, where secondary users relay data for primary users in order to gain access to the spectrum. In light of user and channel diversity, we first propose FLEC, a novel flexible channel cooperation scheme. It allows secondary users to freely optimize the use of channels for transmitting primary data along with their own, in order to maximize performance. Further, we formulate a unifying optimization framework based on Nash bargaining solutions to fairly and efficiently allocate resources between primary and secondary networks, in both decentralized and centralized settings. We present an optimal distributed
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, algorithm and a suboptimal centralized heuristic, and verify their effectiveness via realistic simulations. Under the same framework, we also study conventional identical channel cooperation as the performance benchmark, and propose algorithms to solve the corresponding optimization problems. ETPL MC-024 Spatial Distribution and Channel Quality Adaptive Protocol for Multihop Wireless Broadcast Routing in VANET Abstract: Multihop wireless broadcast is an important component in vehicular networks. Many applications are built on broadcast communications, so efficient routing methods are critical for their success. Here, we develop the Distribution-Adaptive Distance with Channel Quality (DADCQ) protocol to address this need and show that it performs well compared to several existing multihop broadcast proposals. The DADCQ protocol utilizes the distance method to select forwarding nodes. The performance of this method depends heavily on the value of the decision threshold, but it is difficult to choose a value that results in good performance across all scenarios. Node density, spatial distribution pattern, and wireless channel quality all affect the optimal value. Broadcast protocols tailored to vehicular networking must be adaptive to variation in these factors. In this work, we address this design challenge by creating a decision threshold function that is simultaneously adaptive to the number of neighbors, the node clustering factor, and the Rician fading parameter. To calculate the clustering factor, we propose using the quadrat method of spatial analysis. The resulting DADCQ protocol is then verified with JiST/SWANS and shown to achieve high reachability and low bandwidth consumption in urban and highway scenarios with varying node density and fading intensity. ETPL MC-025 On the Forwarding Performance under Heterogeneous Contact Dynamics in Mobile Opportunistic Networks Abstract: In this paper, we focus on how the heterogeneous contact dynamics of mobile nodes impact the performance of forwarding algorithms in mobile opportunistic networks (MONs). To this end, we consider two representative heterogeneous network models, each of which captures heterogeneity among node pairs (individual) and heterogeneity in underlying environment (spatial), respectively, and examine the full extent of difference in delay performance they cause on forwarding algorithms through formal stochastic comparisons. We first show that these heterogeneous models correctly capture non-Poisson contact dynamics observed in real traces. We then rigorously establish stochastic/convex ordering relationships on the delay performance of direct forwarding and multicopy two-hop relay protocol under these heterogeneous models and the corresponding homogeneous model, all of which have the same average intercontact time of a random pair of nodes. In particular, we demonstrate that the heterogeneous models predict an entirely opposite ordering relationship in delay performance depending on which of the two heterogeneity structures is captured. We also provide simulation results including the delay performance of epidemic routing protocol to support the analytical findings. Our results thus suggest that the heterogeneity in mobile nodes' contact dynamics should be properly taken into account for the performance evaluation of forwarding algorithms. Our results will also be useful for better design of forwarding algorithms correctly exploiting the heterogeneity structure. ETPL MC-026 A MAC Sensing Protocol Design for Data Transmission with More Protection to Primary Users Abstract: MAC protocols to sense channels for data transmission have been widely investigated for the secondary users to efficiently utilize and share the spectrum licensed by the primary user. One important issue associated with MAC protocols design is how the secondary users determine when and which channel they should sense and access without causing harmful interference to the primary user. In this paper, we jointly consider the MAC-layer spectrum sensing and channel access. Normal Spectrum Sensing (NSS) is required to be carried out at the beginning of each frame to determine whether the channel is idle. On detecting the available transmission opportunity, the secondary users employ CSMA
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, for channel contention. The novelty is that, Fast Spectrum Sensing (FSS) is inserted after channel contention to promptly detect the return of the primary users. This is unlike most other MAC protocols which do not incorporate FSS. Having FSS, the primary user can benefit from more protection. A concrete protocol design is provided in this paper, and the throughput-collision tradeoff and utility- collision tradeoff problems are formulated to evaluate its performance. Simulation results demonstrate the efficiency of the proposed MAC protocol with FSS. ETPL MC-027 Autonomous Sensing Order Selection Strategies Exploiting Channel Access Information Abstract: We design an efficient sensing order selection strategy for a distributed cognitive radio (CR) network, where two or more autonomous CRs sense the channels sequentially (in some sensing order) for spectrum opportunities. We are particularly interested in the case where CRs with false alarms autonomously select the sensing orders in which they visit channels, without coordination from a centralized entity. We propose an adaptive persistent sensing order selection strategy and show that this strategy converges and reduces the likelihood of collisions among the autonomous CRs as compared to a random selection of sensing orders. We also show that, when the number of CRs is less than or equal to the number of channels, the proposed strategy enables the CRs to converge to collision-free channel sensing orders. The proposed adaptive persistent strategy also reduces the expected time of arrival at collision-free sensing orders as compared to the randomize after every collision strategy, in which a CR, upon colliding, randomly selects a new sensing order. ETPL MC-028 A Spectrum Switching Delay-Aware Scheduling Algorithm for Centralized Cognitive Radio Networks Abstract: We formulate a scheduling problem that takes into account different hardware delays experienced by the secondary users (SUs) in a centralized cognitive radio network (CRN) while switching to different frequency bands. We propose a polynomial-time suboptimal algorithm to address our formulated scheduling problem. We evaluate the impact of varying switching delay, number of frequencies, and number of SUs. Our simulation results indicate that our proposed algorithm is robust to changes in the hardware spectrum switching delay and its performance is very close to its upper bound. We also compare our proposed method with the corresponding constant switching delay-based algorithm and demonstrate that our suggestion of taking into account the different hardware delays while switching to different frequency bands is essential for scheduling in CRNs. ETPL MC-029 Efficient Objective Functions for Coordinated Learning in Large-Scale Distributed OSA Systems Abstract: In this paper, we derive and evaluate private objective functions for large-scale, distributed opportunistic spectrum access (OSA) systems. By means of any learning algorithms, these derived objective functions enable OSA users to assess, locate, and exploit unused spectrum opportunities effectively by maximizing the users' average received rewards. We consider the elastic traffic model, suitable for elastic applications such as file transfer and web browsing, and in which an SU's received reward increases proportionally to the amount of received service when the amount is higher than a certain threshold. But when this amount is below the threshold, the reward decreases exponentially with the amount of received service. In this model, SUs are assumed to be treated fairly in that the SUs using the same band will roughly receive an equal share of the total amount of service offered by the band. We show that the proposed objective functions are: near-optimal, as they achieve high performances in terms of average received rewards; highly scalable, as they perform well for small- as well as large-scale systems; highly learnable, as they reach up near-optimal values very quickly; and distributive, as they require information sharing only among OSA users belonging to the same band.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, ETPL MC-030 Minimum CDS in Multihop Wireless Networks with Disparate Communication Ranges Abstract: Connected dominating set (CDS) has a wide range of applications in multihop wireless networks. The Minimum CDS problem has been studied extensively in multihop wireless networks with uniform communication ranges. However, in practice, the nodes may have different communication ranges either because of the heterogeneity of the nodes, or due to interference mitigation, or due to a chosen range assignment for energy conservation. In this paper, we present a greedy approximation algorithm for computing a Minimum CDS in multihop wireless networks with disparate communications ranges and prove that its approximation ratio is better than the best one known in the literature. Our analysis utilizes a tighter relation between the independence number and the connected domination number. ETPL MC-031 DCIM: Distributed Cache Invalidation Method for Maintaining Cache Consistency in Wireless Mobile Networks Abstract: This paper proposes distributed cache invalidation mechanism (DCIM), a client-based cache consistency scheme that is implemented on top of a previously proposed architecture for caching data items in mobile ad hoc networks (MANETs), namely COACS, where special nodes cache the queries and the addresses of the nodes that store the responses to these queries. We have also previously proposed a server-based consistency scheme, named SSUM, whereas in this paper, we introduce DCIM that is totally client-based. DCIM is a pull-based algorithm that implements adaptive time to live (TTL), piggybacking, and prefetching, and provides near strong consistency capabilities. Cached data items are assigned adaptive TTL values that correspond to their update rates at the data source, where items with expired TTL values are grouped in validation requests to the data source to refresh them, whereas unexpired ones but with high request rates are prefetched from the server. In this paper, DCIM is analyzed to assess the delay and bandwidth gains (or costs) when compared to polling every time and push-based schemes. DCIM was also implemented using ns2, and compared against client-based and server-based schemes to assess its performance experimentally. The consistency ratio, delay, and overhead traffic are reported versus several variables, where DCIM showed to be superior when compared to the other systems. ETPL MC-032 Evolutionarily Stable Spectrum Access Abstract: In this paper, we design distributed spectrum access mechanisms with both complete and incomplete network information. We propose an evolutionary spectrum access mechanism with complete network information, and show that the mechanism achieves an equilibrium that is globally evolutionarily stable. With incomplete network information, we propose a distributed learning mechanism, where each user utilizes local observations to estimate the expected throughput and learns to adjust its spectrum access strategy adaptively over time. We show that the learning mechanism converges to the same evolutionary equilibrium on the time average. Numerical results show that the proposed mechanisms achieve up to 35 percent performance improvement over the distributed reinforcement learning mechanism in the literature, and are robust to the perturbations of users' channel selections. ETPL MC-033 Tula: Balancing Energy for Sensing and Communication in a Perpetual Mobile System
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: Due to advances in low power sensors, energy harvesting, and disruption tolerant networking, we can now build mobile systems that operate perpetually, sensing and streaming data directly to scientists. However, factors such as energy harvesting variability and unpredictable network connectivity make building robust and perpetual systems difficult. In this paper, we present a system, Tula, that balances sensing with data delivery, to allow perpetual and robust operation across highly dynamic and mobile networks. This balance is especially important in unpredictable environments; sensing more data than can be delivered by the network is not useful, while gathering less underutilizes the system's potential. Tula is decentralized, fair and automatically adapts across different mobility patterns. We evaluate Tula using mobility and energy traces from TurtleNet-a mobile sensor network we deployed to study Gopher tortoises-and publicly available traces from the UMass DieselNet testbed. Our evaluations show that Tula senses and delivers data at up to 85 percent of an optimal, oracular system that perfectly replicates data and has foreknowledge of future energy harvesting. We also demonstrate that Tula can be implemented on a small microcontroller with modest code, memory, and processing requirements. ETPL MC-034 UPL: Opportunistic Localization in Urban Districts Abstract: We propose an opportunistic ad hoc localization algorithm called Urban Pedestrians Localization (UPL), for estimating locations of mobile nodes in urban districts. The design principles of UPL are twofold. First, we assume that location landmarks are deployed sparsely due to deployment-cost constraints. Thus, most mobile nodes cannot expect to meet these location landmarks frequently. Each mobile node in UPL relies on location information received from its neighboring mobile nodes instead in order to estimate its area of presence in which the node is expected to exist. Although the area of presence of each mobile node becomes inexact as it moves, it can be used to reduce the areas of presence of the others. Second, we employ information about obstacles such as walls, and present an algorithm to calculate the movable areas of mobile nodes considering obstacles for predicting the area of presence of mobile nodes accurately under mobility. This also helps to reduce each node's area of presence. The experimental results have shown that UPL could be limited to $(0.7r)$ positioning error in average, where $(r)$ denotes the radio range by the above two ideas. ETPL MC-035 Cell Selection in 4G Cellular Networks Abstract: Cell selection is the process of determining the cell(s) that provide service to each mobile station. Optimizing these processes is an important step toward maximizing the utilization of current and future cellular networks. We study the potential benefit of global cell selection versus the current local mobile SNR-based decision protocol. In particular, we study the new possibility available in OFDMA- based systems, such as IEEE 802.16m and LTE-Advanced, of satisfying the minimal demand of a mobile station simultaneously by more than one base station. We formalize the problem as an optimization problem, and show that in the general case this problem is not only NP-hard but also cannot be approximated within any reasonable factor. In contrast, under the very practical assumption that the maximum required bandwidth of a single mobile station is at most an r-fraction of the capacity of a base station, we present two different algorithms for cell selection. The first algorithm produces a (1-r)- approximate solution, where a mobile station can be covered simultaneously by more than one base station. The second algorithm produces a 1-r/2-r-approximate solution, while every mobile station is covered by at most one base station. We complete our study by an extensive simulation study demonstrating the benefits of using our algorithms in high-loaded capacity-constrained future 4G networks, compared to currently used methods. Specifically, our algorithms obtain up to 20 percent better usage of the network's capacity, in comparison with the current cell selection algorithms.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, ETPL MC-036 ALERT: An Anonymous Location-Based Efficient Routing Protocol in MANETs Abstract: Mobile Ad Hoc Networks (MANETs) use anonymous routing protocols that hide node identities and/or routes from outside observers in order to provide anonymity protection. However, existing anonymous routing protocols relying on either hop-by-hop encryption or redundant traffic, either generate high cost or cannot provide full anonymity protection to data sources, destinations, and routes. The high cost exacerbates the inherent resource constraint problem in MANETs especially in multimedia wireless applications. To offer high anonymity protection at a low cost, we propose an Anonymous Location-based Efficient Routing proTocol (ALERT). ALERT dynamically partitions the network field into zones and randomly chooses nodes in zones as intermediate relay nodes, which form a nontraceable anonymous route. In addition, it hides the data initiator/receiver among many initiators/receivers to strengthen source and destination anonymity protection. Thus, ALERT offers anonymity protection to sources, destinations, and routes. It also has strategies to effectively counter intersection and timing attacks. We theoretically analyze ALERT in terms of anonymity and efficiency. Experimental results exhibit consistency with the theoretical analysis, and show that ALERT achieves better route anonymity protection and lower cost compared to other anonymous routing protocols. Also, ALERT achieves comparable routing efficiency to the GPSR geographical routing protocol. ETPL MC-037 Noninteractive Localization of Wireless Camera Sensors with Mobile Beacon Abstract: Recent advances in the application field increasingly demand the use of wireless camera sensor networks (WCSNs), for which localization is a crucial task to enable various location-based services. Most of the existing localization approaches for WCSNs are essentially interactive, i.e., require the interaction among the nodes throughout the localization process. As a result, they are costly to realize in practice, vulnerable to sniffer attacks, inefficient in energy consumption and computation. In this paper, we propose LISTEN, a noninteractive localization approach. Using LISTEN, every camera sensor node only needs to silently listen to the beacon signals from a mobile beacon node and capture a few images until determining its own location. We design the movement trajectory of the mobile beacon node, which guarantees to locate all the nodes successfully. We have implemented LISTEN and evaluated it through extensive experiments. Both the analytical and experimental results demonstrate that it is accurate, cost- efficient, and especially suitable for WCSNs that consist of low-end camera sensors. ETPL MC-038 Variable-Width Channel Allocation for Access Points: A Game-Theoretic Perspective Abstract: Channel allocation is a crucial concern in variable-width wireless local area networks. This work aims to obtain the stable and fair nonoverlapped variable-width channel allocation for selfish access points (APs). In the scenario of single collision domain, the channel allocation problem reduces to a channel-width allocation problem, which can be formulated as a noncooperative game. The Nash equilibrium (NE) of the game corresponds to a desired channel-width allocation. A distributed algorithm is developed to achieve the NE channel-width allocation that globally maximizes the network utility. A punishment-based cooperation self-enforcement mechanism is further proposed to ensure that the APs obey the proposed scheme. In the scenario of multiple collision domains, the channel allocation problem is formulated as a constrained game. Penalty functions are introduced to relax the constraints and the game is converted into a generalized ordinal potential game. Based on the best response and randomized escape, a distributed iterative algorithm is designed to achieve a desired NE channel allocation. Finally, computer simulations are conducted to validate the effectiveness and practicality of the proposed schemes.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, ETPL MC-039 Cross-Layer Minimum-Delay Scheduling and Maximum-Throughput Resource Allocation for Multiuser Cognitive Networks Abstract: A cognitive network is considered that consists of a base station (BS) communicating with multiple primary and secondary users. Each secondary user can access only one of the orthogonal primary channels. A model is considered in which the primary users can tolerate a certain average delay. A special case is also considered in which the primary users do not suffer from any delay. A novel cross-layer scheme is proposed in which the BS performs successive interference cancellation and thus a secondary user can coexist with an active primary user without adversely affecting its transmission. A scheduling algorithm is proposed that minimizes the average packet delay of the secondary user under constraints on the average power transmitted by the secondary user and the average packet delay of the primary user. A resource allocation algorithm is also proposed to assign the secondary users' channels such that the total throughput of the network is maximized. Our results indicate that the network throughput increases significantly by increasing the number of transmitted packets of the secondary users and/or by allowing a small delay for the primary user packets. ETPL MC-040 Target Tracking and Mobile Sensor Navigation in Wireless Sensor Networks Abstract: This work studies the problem of tracking signal-emitting mobile targets using navigated mobile sensors based on signal reception. Since the mobile target's maneuver is unknown, the mobile sensor controller utilizes the measurement collected by a wireless sensor network in terms of the mobile target signal's time of arrival (TOA). The mobile sensor controller acquires the TOA measurement information from both the mobile target and the mobile sensor for estimating their locations before directing the mobile sensor's movement to follow the target. We propose a min-max approximation approach to estimate the location for tracking which can be efficiently solved via semidefinite programming (SDP) relaxation, and apply a cubic function for mobile sensor navigation. We estimate the location of the mobile sensor and target jointly to improve the tracking accuracy. To further improve the system performance, we propose a weighted tracking algorithm by using the measurement information more efficiently. Our results demonstrate that the proposed algorithm provides good tracking performance and can quickly direct the mobile sensor to follow the mobile target. ETPL MC-041 EMAP: Expedite Message Authentication Protocol for Vehicular Ad Hoc Networks Abstract: Vehicular ad hoc networks (VANETs) adopt the Public Key Infrastructure (PKI) and Certificate Revocation Lists (CRLs) for their security. In any PKI system, the authentication of a received message is performed by checking if the certificate of the sender is included in the current CRL, and verifying the authenticity of the certificate and signature of the sender. In this paper, we propose an Expedite Message Authentication Protocol (EMAP) for VANETs, which replaces the time-consuming CRL checking process by an efficient revocation checking process. The revocation check process in EMAP uses a keyed Hash Message Authentication Code ({HMAC}), where the key used in calculating the {HMAC} is shared only between nonrevoked On-Board Units (OBUs). In addition, EMAP uses a novel probabilistic key distribution, which enables nonrevoked OBUs to securely share and update a secret key. EMAP can significantly decrease the message loss ratio due to the message verification delay compared with the conventional authentication methods employing CRL. By conducting security analysis and performance evaluation, EMAP is demonstrated to be secure and efficient. ETPL MC-042 Group-Based Medium Access Control for IEEE 802.11n Wireless LANs
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: The latest generation of Wireless Local Area Networks (WLANs) is based on IEEE 802.11n- 2009 Standard. The standard provides very high data rates at the physical layer and aims to achieve a throughput at the Medium Access Control (MAC) layer that is higher than 100 Mbps. To do that, the standard introduces several mechanisms to improve the MAC efficiency. The most notable ones are the use of frame aggregation and Block-ACK frames. The standard, however, does not introduce a mechanism to reduce the probability of collision. This issue is significant because, with a high data rate, an AP would be able to serve a large number of stations, which would result in a high collision rate. In this paper, we propose a Group-based MAC (GMAC) scheme that reduces the probability of collision and also uses frame aggregation to improve the efficiency. The contending stations are divided into groups. Each group has one station that is the group leader. Only the leader stations contend, hence, reducing the probability of a collision. We evaluate the performance of our scheme with analytic and simulation results. The results show that GMAC achieves a high throughput, high fairness, low delay and maintains a high performance with high data rates. ETPL MC-043 A Strategy-Proof Radio Spectrum Auction Mechanism in Noncooperative Wireless Networks Abstract: With the growing deployment of wireless communication technologies, radio spectrum is becoming a scarce resource. Thus, mechanisms to efficiently allocate the available spectrum are of interest. In this paper, we model the radio spectrum allocation problem as a sealed-bid reserve auction, and propose SMALL, which is a Strategy-proof Mechanism for radio spectrum ALLocation. Furthermore, we extend SMALL to adapt to multiradio spectrum buyers, which can bid for more than one radio. We evaluate SMALL with simulations. Simulation results show that SMALL has good performance in median to large scale spectrum auctions. ETPL MC-044 An Efficient Time-Bound Collision Prevention Scheme for RFID Re-Entering Tags Abstract: The efficiency of RFID applications is severely degraded when multiple tags transmit their IDs simultaneously. As a result, many anticollision algorithms have been proposed for reducing collisions at the reader. However, these algorithms focus only on the tags within communication range of the reader in the previous or current frames. That is, they ignore tags which move out of range of the reader in one frame, but then move back within range several frames later. As a result, the identification performance of the reader is seriously degraded. The present study analyzes the effect of re-entering tags on the performance of three common anticollision algorithms and proposes a new reblocking algorithm (RBA) to alleviate the problem. The lower and upper bounds of the collision probability for re-entering tags are derived using a multinomial coefficients approach. The performance evaluation results show that the proposed algorithm consumes fewer cycles and provides a more robust identification performance than existing blocking algorithms in real-world RFID systems characterized by re-entering tags. ETPL MC-045 Game-Based Broadcast over Reliable and Unreliable Wireless Links in Wireless Multihop Networks Abstract: This paper addresses the minimum transmission broadcast problem in wireless networks and presents efficient solutions, including an optimal broadcast scheme and a distributed game-based algorithm. Distinct from related work in the literature which typically assumes wireless links are reliable, we address the issue of broadcasting over both reliable wireless links and unreliable wireless links. Our main contributions are as follows: We first formulate the minimum transmission broadcast problems over reliable links and over unreliable links as two mixed integer linear programming (MILP) problems, respectively. This way, optimal broadcast schemes can be easily obtained using any existing MILP solver, for small-scale networks. For large-scale networks, we propose a distributed game-based algorithm and prove that the game-based algorithm achieves Nash Equilibrium. Using simulation, we confirm that
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, compared with existing algorithms in the literature and optimal solutions obtained by our MILP techniques, the proposed game-based algorithm performs very well in terms of delivery ratio, the number of transmissions, and convergence speed. ETPL MC-046 Understanding the Information Propagation Speed in Multihop Cognitive Radio Networks bstract: Information propagation speed (IPS) in a multihop cognitive radio network (CRN) is an important factor that affects the network's delay performance and needs to be considered in network planning and routing protocol design. The impact of primary user (PU) activities on IPS makes the problem of analyzing IPS in multihop CRNs very challenging and, hence, unsolved in existing literature. In this paper, we fill this technical void. We establish models of IPS in multihop CRNs and compute how to maximize IPS in two cases. The first case, named the maximum network IPS, maximizes IPS across a network topology over an infinite plane. The second case, named the maximum flow IPS, maximizes the IPS between a given pair of source and destination nodes separated by a fixed distance. We reveal that both maximum IPSs are determined by the PU activity level and the placement of secondary user (SU) relay nodes. We design optimal relay placement strategies in CRNs to maximize these two IPSs under different PU activity levels. The correctness of our analytical results is validated by simulations and numerical experiments ETPL MC-047 Coalition-Based Cooperative Packet Delivery under Uncertainty: A Dynamic Bayesian Coalitional Game Abstract: Cooperative packet delivery can improve the data delivery performance in wireless networks by exploiting the mobility of the nodes, especially in networks with intermittent connectivity, high delay and error rates such as wireless mobile delay-tolerant networks (DTNs). For such a network, we study the problem of rational coalition formation among mobile nodes to cooperatively deliver packets to other mobile nodes in a coalition. Such coalitions are formed by mobile nodes which can be either well behaved or misbehaving in the sense that the well-behaved nodes always help each other for packet delivery, while the misbehaving nodes act selfishly and may not help the other nodes. A Bayesian coalitional game model is developed to analyze the behavior of mobile nodes in coalition formation in presence of this uncertainty of node behavior (i.e., type). Given the beliefs about the other mobile nodes' types, each mobile node makes a decision to form a coalition, and thus the coalitions in the network vary dynamically. A solution concept called Nash-stability is considered to find a stable coalitional structure in this coalitional game with incomplete information. We present a distributed algorithm and a discrete-time Markov chain (DTMC) model to find the Nash-stable coalitional structures. We also consider another solution concept, namely, the Bayesian core, which guarantees that no mobile node has an incentive to leave the grand coalition. The Bayesian game model is extended to a dynamic game model for which we propose a method for each mobile node to update its beliefs about other mobile nodes' types when the coalitional game is played repeatedly. The performance evaluation results show that, for this dynamic Bayesian coalitional game, a Nash-stable coalitional structure is obtained in each subgame. Also, the actual payoff of each mobile node is close to that when all the information is completely known. In addition, the payoffs of the mobile nodes will be at least as h- gh as those when they act alone (i.e., the mobile nodes do not form coalitions). ETPL MC-048 Adaptive Position Update for Geographic Routing in Mobile Ad Hoc Networks Abstract: In geographic routing, nodes need to maintain up-to-date positions of their immediate neighbors for making effective forwarding decisions. Periodic broadcasting of beacon packets that contain the geographic location coordinates of the nodes is a popular method used by most geographic routing protocols to maintain neighbor positions. We contend and demonstrate that periodic beaconing regardless
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, of the node mobility and traffic patterns in the network is not attractive from both update cost and routing performance points of view. We propose the Adaptive Position Update (APU) strategy for geographic routing, which dynamically adjusts the frequency of position updates based on the mobility dynamics of the nodes and the forwarding patterns in the network. APU is based on two simple principles: 1) nodes whose movements are harder to predict update their positions more frequently (and vice versa), and (ii) nodes closer to forwarding paths update their positions more frequently (and vice versa). Our theoretical analysis, which is validated by NS2 simulations of a well-known geographic routing protocol, Greedy Perimeter Stateless Routing Protocol (GPSR), shows that APU can significantly reduce the update cost and improve the routing performance in terms of packet delivery ratio and average end-to-end delay in comparison with periodic beaconing and other recently proposed updating schemes. The benefits of APU are further confirmed by undertaking evaluations in realistic network scenarios, which account for localization error, realistic radio propagation, and sparse network. ETPL MC-049 Evaluating Temporal Robustness of Mobile Networks Abstract: The application of complex network models to communication systems has led to several important results: nonetheless, previous research has often neglected to take into account their temporal properties, which in many real scenarios play a pivotal role. At the same time, network robustness has come extensively under scrutiny. Understanding whether networked systems can undergo structural damage and yet perform efficiently is crucial to both their protection against failures and to the design of new applications. In spite of this, it is still unclear what type of resilience we may expect in a network which continuously changes over time. In this work, we present the first attempt to define the concept of temporal network robustness: we describe a measure of network robustness for time-varying networks and we show how it performs on different classes of random models by means of analytical and numerical evaluation. Finally, we report a case study on a real-world scenario, an opportunistic vehicular system of about 500 taxicabs, highlighting the importance of time in the evaluation of robustness. Particularly, we show how static approximation can wrongly indicate high robustness of fragile networks when adopted in mobile time-varying networks, while a temporal approach captures more accurately the system performance. ETPL MC-050 Predictable Mobile Routing for Spacecraft Networks Abstract: In predictable mobile networks, network nodes move in a predictable way and therefore have dynamically changing but predictable connectivity. We have developed a model that formalizes predictable dynamic topologies as sequences of static snapshots. We use this model to design and evaluate a predictable mobile-routing protocol based on link-state routing, whose performance is superior to its static and ad hoc counterparts. Our routing protocol accounts for occurrences of additional, unpredictable changes, as well as their interaction with predictable changes. We evaluate our protocol using simulations based on randomly generated topologies and spacecraft-network scenarios. In both cases, we show that our protocol outperforms traditional routing protocols and is well suited for routing in next-generation space networks. ETPL MC-051 Maximizing Rendezvous Diversity in Rendezvous Protocols for Decentralized Cognitive Radio Networks Abstract: In decentralized cognitive radio (CR) networks, establishing a link between a pair of communicating nodes requires that the radios "rendezvous” in a common channel-such a channel is called a rendezvous channel-to exchange control information. When unlicensed (secondary) users opportunistically share spectrum with licensed (primary or incumbent) users, a given rendezvous channel may become unavailable due to the appearance of licensed user signals. Ideally, every node pair should be
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, able to rendezvous in every available channel (i.e., maximize the rendezvous diversity) so that the possibility of rendezvous failures is minimized. Channel hopping (CH) protocols have been proposed previously for establishing pairwise rendezvous. Some of them enable pairwise rendezvous over all channels but require global clock synchronization, which may be very difficult to achieve in decentralized networks. Maximizing the pairwise rendezvous diversity in decentralized CR networks is a very challenging problem. In this paper, we present a systematic approach for designing CH protocols that maximize the rendezvous diversity of any node pair in decentralized CR networks. The resulting protocols are resistant to rendezvous failures caused by the appearance of primary user (PU) signals and do not require clock synchronization. The proposed approach, called asynchronous channel hopping (ACH), has two noteworthy features: 1) any pair of CH nodes are able to rendezvous on every channel so that the rendezvous process is robust to disruptions caused by the appearance of PU signals; and 2) an upper bounded time-to-rendezvous (TTR) is guaranteed between the two nodes even if their clocks are asynchronous. We propose two optimal ACH designs that maximize the rendezvous diversity between any pair of nodes and show their rendezvous performance via analytical and simulation results. ETPL MC-052 Discovery and Verification of Neighbor Positions in Mobile Ad Hoc Networks Abstract: A growing number of ad hoc networking protocols and location-aware services require that mobile nodes learn the position of their neighbors. However, such a process can be easily abused or disrupted by adversarial nodes. In absence of a priori trusted nodes, the discovery and verification of neighbor positions presents challenges that have been scarcely investigated in the literature. In this paper, we address this open issue by proposing a fully distributed cooperative solution that is robust against independent and colluding adversaries, and can be impaired only by an overwhelming presence of adversaries. Results show that our protocol can thwart more than 99 percent of the attacks under the best possible conditions for the adversaries, with minimal false positive rates. ETPL MC-053 Toward Accurate Mobile Sensor Network Localization in Noisy Environments Abstract: The node localization problem in mobile sensor networks has received significant attention. Recently, particle filters adapted from robotics have produced good localization accuracies in conventional settings. In spite of these successes, state-of-the-art solutions suffer significantly when used in challenging indoor and mobile environments characterized by a high degree of radio signal irregularity. New solutions are needed to address these challenges. We propose a fuzzy logic-based approach for mobile node localization in challenging environments. Localization is formulated as a fuzzy multilateration problem. For sparse networks with few available anchors, we propose a fuzzy grid- prediction scheme. The fuzzy logic-based localization scheme is implemented in a simulator and compared to state-of-the-art solutions. Extensive simulation results demonstrate improvements in the localization accuracy from 20 to 40 percent when the radio irregularity is high. A hardware implementation running on Epic motes and transported by iRobot mobile hosts confirms simulation results and extends them to the real world. ETPL MC-054 Reducing Signaling Overhead for Femtocell/Macrocell Networks Abstract: Femtocell technology has been proposed to offload user data traffic from the macrocell to the femtocell and extend the limited coverage of the macrocell in mobile communications networks. In existing commercial femtocell/macrocell networks, a widely accepted solution to configure the location areas (LAs) is to partition the femtocells overlapped with a macrocell into small groups and to assign each group with a unique LA ID different from that of the macrocell. Such configuration can reduce the paging cost in the mobility management, but increases registration signaling overhead due to discontinuous
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, coverage of femtocells. To reduce signaling overhead in the femtocell/macrocell network, we propose a delay registration (DR) algorithm that postpones the registration until the delay timer expires when the mobile station (MS) moves into the overlapped femtocell. Analytical models and simulation experiments are proposed to investigate the performance of the DR algorithm. Our analytical models are generally enough to accommodate various MS mobility behaviors. Our study can provide guidelines for the operators to set up a delay timer to reduce signaling overhead while sustaining the traffic offloading capability of the femtocell. ETPL MC-055 Contention-Based Estimation of Neighbor Cardinality Abstract: Several communication protocols and applications require a node to know how many neighboring nodes exhibiting a certain attribute it has. Conventionally, such neighbor information is obtained by explicit message exchange between nodes, which is reliable but inefficient in densely connected networks in terms of overhead and delay. An alternative approach is to perform an estimation of the neighbor cardinality using probabilistic methods. This paper pursues such an approach by proposing neighbor cardinality estimators that require no coordination among polled nodes but are based on a simple random access scheme with busy tones, where the number of empty slots is exploited to infer about the neighbor cardinality. We compare three estimators with different levels of adaptability and feedback from the query node and discuss their suitability for IEEE 802.11 and low power sensors. Performance is studied in terms of estimation accuracy and delay. ETPL MC-056 Capacity of Hybrid Wireless Mesh Networks with Random APs, Abstract: In conventional Wireless Mesh Networks (WMNs), multihop relays are performed in the backbone comprising of interconnected Mesh Routers (MRs) and this causes capacity degradation. This paper proposes a hybrid WMN architecture that the backbone is able to utilize random connections to Access Points (APs) of Wireless Local Area Network (WLAN). In such a proposed hierarchal architecture, capacity enhancement can be achieved by letting the traffic take advantage of the wired connections through APs. Theoretical analysis has been conducted for the asymptotic capacity of three- tier hybrid WMN, where per-MR capacity in the backbone is first derived and per-MC capacity is then obtained. Besides related to the number of MR cells as a conventional WMN, the analytical results reveal that the asymptotic capacity of a hybrid WMN is also strongly affected by the number of cells having AP connections, the ratio of access link bandwidth to backbone link bandwidth, etc. Appropriate configuration of the network can drastically improve the network capacity in our proposed network architecture. It also shows that the traffic balance among the MRs with AP access is very important to have a tighter asymptotic capacity bound. The results and conclusions justify the perspective of having such a hybrid WMN utilizing widely deployed WLANs. ETPL MC-057 SSD: A Robust RF Location Fingerprint Addressing Mobile Devices' Heterogeneity Abstract: Fingerprint-based methods are widely adopted for indoor localization purpose because of their cost-effectiveness compared to other infrastructure-based positioning systems. However, the popular location fingerprint, Received Signal Strength (RSS), is observed to differ significantly across different devices' hardware even under the same wireless conditions. We derive analytically a robust location fingerprint definition, the Signal Strength Difference (SSD), and verify its performance experimentally using a number of different mobile devices with heterogeneous hardware. Our experiments have also considered both Wi-Fi and Bluetooth devices, as well as both Access-Point(AP)-based localization and Mobile-Node (MN)-assisted localization. We present the results of two well-known localization algorithms (K Nearest Neighbor and Bayesian Inference) when our proposed fingerprint is used, and
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, demonstrate its robustness when the testing device differs from the training device. We also compare these SSD-based localization algorithms' performance against that of two other approaches in the literature that are designed to mitigate the effects of mobile node hardware variations, and show that SSD- based algorithms have better accuracy. ETPL MC-058 Toward Privacy Preserving and Collusion Resistance in a Location Proof Updating System Abstract: Today's location-sensitive service relies on user's mobile device to determine the current location. This allows malicious users to access a restricted resource or provide bogus alibis by cheating on their locations. To address this issue, we propose A Privacy-Preserving LocAtion proof Updating System (APPLAUS) in which colocated Bluetooth enabled mobile devices mutually generate location proofs and send updates to a location proof server. Periodically changed pseudonyms are used by the mobile devices to protect source location privacy from each other, and from the untrusted location proof server. We also develop user-centric location privacy model in which individual users evaluate their location privacy levels and decide whether and when to accept the location proof requests. In order to defend against colluding attacks, we also present betweenness ranking-based and correlation clustering-based approaches for outlier detection. APPLAUS can be implemented with existing network infrastructure, and can be easily deployed in Bluetooth enabled mobile devices with little computation or power cost. Extensive experimental results show that APPLAUS can effectively provide location proofs, significantly preserve the source location privacy, and effectively detect colluding attacks. ETPL MC-059 Distributed Cooperative Caching in Social Wireless Networks Abstract: This paper introduces cooperative caching policies for minimizing electronic content provisioning cost in Social Wireless Networks (SWNET). SWNETs are formed by mobile devices, such as data enabled phones, electronic book readers etc., sharing common interests in electronic content, and physically gathering together in public places. Electronic object caching in such SWNETs are shown to be able to reduce the content provisioning cost which depends heavily on the service and pricing dependences among various stakeholders including content providers (CP), network service providers, and End Consumers (EC). Drawing motivation from Amazon's Kindle electronic book delivery business, this paper develops practical network, service, and pricing models which are then used for creating two object caching strategies for minimizing content provisioning costs in networks with homogenous and heterogeneous object demands. The paper constructs analytical and simulation models for analyzing the proposed caching strategies in the presence of selfish users that deviate from network-wide cost-optimal policies. It also reports results from an Android phone-based prototype SWNET, validating the presented analytical and simulation results. ETPL MC-060 A Robust Indoor Pedestrian Tracking System with Sparse Infrastructure Support Abstract: Existing approaches to indoor tracking have various limitations. Location-fingerprinting approaches are labor intensive and vulnerable to environmental changes. Trilateration approaches require at least three line-of-sight beacons for coverage at any point in the service area, which results in heavy infrastructure cost. Dead reckoning (DR) approaches rely on knowledge of the initial location and suffer from tracking error accumulation. Despite this, we adopt DR for location tracking because of the recent emergence of affordable hand-held devices equipped with low-cost DR-enabling sensors. In this paper, we propose an indoor pedestrian tracking system that comprises of a DR subsystem implemented on a mobile phone and a ranging subsystem with a sparse infrastructure. A particle-filter-based fusion scheme is applied to bound the accumulated tracking error by fusing DR with sparse range measurements. Experimental results show that the proposed system is able to track users much better than DR alone. The
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, system is robust even when: 1) the initial user location is not available; 2) range updates are noisy; and 3) range updates are intermittent, both temporally and spatially. ETPL MC-061 Measurement-Based Design of Roadside Content Delivery Systems Abstract: With today's ubiquity of thin computing devices, mobile users are accustomed to having rich location-aware information at their fingertips, such as restaurant menus, shopping mall maps, movie showtimes, and trailers. However, delivering rich content is challenging, particularly for highly mobile users in vehicles. Technologies such as cellular-3G provide limited bandwidth at significant costs. In contrast, providers can cheaply and easily deploy a small number of WiFi infostations that quickly deliver large content to vehicles passing by for future offline browsing. While several projects have proposed systems for disseminating content via roadside infostations, most use simplified models and simulations to guide their design for scalability. Many suspect that scalability with increasing vehicle density is the major challenge for infostations, but few if any have studied the performance of these systems via real measurements. Intuitively, per-vehicle throughput for unicast infostations degrades with the number of vehicles near the infostation, while broadcast infostations are unreliable, and lack rate adaptation. In this work, we collect over 200 h of detailed highway measurements with a fleet of WiFi-enabled vehicles. We use analysis of these results to explore the design space of WiFi infostations, in order to determine whether unicast or broadcast should be used to build high-throughput infostations that scale with device density. Our measurement results demonstrate the limitations of both approaches. Our insights lead to Starfish, a high-bandwidth and scalable infostation system that incorporates device-to-device data scavenging, where nearby vehicles share data received from the infostation. Data scavenging increases dissemination throughput by a factor of 2-6, allowing both broadcast and unicast throughput to scale with device density. ETPL MC-062 Understanding the Scheduling Performance in Wireless Networks with Successive Interference Cancellation Abstract: Successive interference cancellation (SIC) is an effective way of multipacket reception to combat interference in wireless networks. We focus on link scheduling in wireless networks with SIC, and propose a layered protocol model and a layered physical model to characterize the impact of SIC. In both the interference models, we show that several existing scheduling schemes achieve the same order of approximation ratios, independent of whether or not SIC is available. Moreover, the capacity order in a network with SIC is the same as that without SIC. We then examine the impact of SIC from first principles. In both chain and cell topologies, SIC does improve the throughput with a gain between 20 and 100 percent. However, unless SIC is properly characterized, any scheduling scheme cannot effectively utilize the new transmission opportunities. The results indicate the challenge of designing an SIC-aware scheduling scheme, and suggest that the approximation ratio is insufficient to measure the scheduling performance when SIC is available. ETPL MC-063 Modeling Beacon Period Length of the UWB and 60-GHz mmWave WPANs Based on ECMA-368 and ECMA-387 Standards Abstract: To evaluate the performance of the distributed medium access control layer of the emerging ultrawideband and 60-GHz millimeter wave (mmWave) wireless personal area networks based on ECMA-368 and ECMA-387 standards, the first step is to determine the beacon period length (BPL) of the superframe in a given network. In this paper, we provide an analytical model for the probability mass function (PMF) of the BPL as a function of the network dimensions, number of beaconing devices, antenna beamwidth, and the transmission range of the devices. To enable devices with steerable directional antennas in the ECMA-387 standard to have simultaneous communications with neighbors in their different antenna sectors, we propose an improvement to the standard for which we computed the
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, PMF of the BPL in its worst case. The effect of beacon period (BP) contraction on the PMF is also considered and modeled. The proposed model for all cases is evaluated by simulating different scenarios in the network and the results show that on average, the model for the average BPL has an error of 1.2 and 2.5 percent in the current definition of the standard and in the proposed modification, respectively, without BP contraction and 0.9 and 1.5 percent, respectively, with BP contraction. ETPL MC-064 A Resource Allocation Scheme for Scalable Video Multicast in WiMAX Relay Networks Abstract: This paper proposes the first resource allocation scheme in the literature to support scalable- video multicast for WiMAX relay networks. We prove that when the available bandwidth is limited, the bandwidth allocation problems of 1) maximizing network throughput and 2) maximizing the number of satisfied users are NP-hard. To find the near-optimal solutions to this type of maximization problem in polynomial time, this study first proposes a greedy weighted algorithm, GWA, for bandwidth allocation. By incorporating table-consulting mechanisms, the proposed GWA can intelligently avoid redundant bandwidth allocation and thus accomplish high network performance (such as high network throughput or large number of satisfied users). To maintain the high performance gained by GWA and simultaneously improve its worst case performance, this study extends GWA to a bounded version, BGWA, which guarantees that its performance gains are lower bounded. This study shows that the computational complexity of BGWA is also in polynomial time and proves that BGWA can provide at least 1/ρ times the performance of the optimal solution, where rho is a finite value no less than one. Finally, simulation results show that the proposed BGWA bandwidth allocation scheme can effectively achieve different performance objectives with different parameter settings. ETPL MC-065 On Random Access Scheduling for Multimedia Traffic in Multihop Wireless Networks with Fading Channels Abstract: In this paper, we develop distributed random access scheduling schemes that exploit the time- varying nature of fading channels for multimedia traffic in multihop wireless networks. It should be noted that while centralized scheduling solutions can achieve optimal throughput under this setting, they incur high-computational complexity and require centralized coordination requiring global channel information. The proposed solution not only achieves provable performance guarantees under a wide range of interference models, but also can be implemented in a distributed fashion using local information. To the best of our knowledge, this is the first distributed scheduling mechanism for fading channels that achieves provable performance guarantees. We show through simulations that the proposed schemes achieve better empirical performance than other known distributed scheduling schemes. ETPL MC-066 Fine-Grained Location-Free Planarization in Wireless Sensor Networks Abstract: Extracting planar graph from network topologies is of great importance for efficient protocol design in wireless ad hoc and sensor networks. Previous techniques of planar topology extraction are often based on ideal assumptions, such as UDG communication model and accurate node location measurements. To make these protocols work effectively in practice, we need extract a planar topology in a location-free and distributed manner with small stretch factors. The planar topologies constructed by current location-free methods often have large stretch factors. In this paper, we present a fine-grained and location-free network planarization method under $(rho)$-quasi-UDG communication model with $(rho ge 1/sqrt{2})$. Compared with existing location-free planarization approaches, our method can extract a provably connected planar graph, called topological planar simplification (TPS), from the connectivity graph in a fine-grained manner using local connectivity information. We evaluate our design through extensive simulations and compare with the state-of-the-art approaches. The simulation results show that our method produces high-quality planar graphs with a small stretch factor in practical large-scale
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, networks. ETPL MC-067 ACE: Exploiting Correlation for Energy-Efficient and Continuous Context Sensing Abstract: We propose an acquisitional context engine (ACE), a middleware that supports continuous context-aware applications while mitigating sensing costs for inferring contexts. The ACE provides user's current context to applications running on it. In addition, it dynamically learns relationships among various context attributes (e.g., whenever the user is Driving, he is not AtHome). The ACE exploits these automatically learned relationships for two powerful optimizations. The first is inference caching that allows the ACE to opportunistically infer one context attribute (AtHome) from another already-known attribute (Driving), without acquiring any sensor data. The second optimization is speculative sensing that enables the ACE to occasionally infer the value of an expensive attribute (e.g., AtHome) by sensing cheaper attributes (e.g., Driving). Our experiments with two real context traces of 105 people and a Windows Phone prototype show that the ACE can reduce sensing costs of three context-aware applications by about 4.2 times, compared to a raw sensor data cache shared across applications, with a very small memory and processing overhead. ETPL MC-068 On Power and Throughput Tradeoffs of WiFi and Bluetooth in Smartphones Abstract: This paper describes a combined power and throughput performance study of WiFi and Bluetooth usage in smartphones. The work measures the obtained throughput in various settings while employing each of these technologies, and the power consumption level associated with them. In addition, the power requirements of Bluetooth and WiFi in their respective noncommunicating modes are also compared. The study reveals several interesting phenomena and tradeoffs. In particular, the paper identifies many situations in which WiFi is superior to Bluetooth, countering previous reports. The study also identifies a couple of scenarios that are better handled by Bluetooth. The conclusions from this study suggest preferred usage patterns, as well as operative suggestions for researchers and smartphone developers. This includes a cross-layer optimization for TCP/IP that could greatly improve the throughput to power ratio whenever the transmitter is more capable than the receiver. ETPL MC-069 Novel Design and Analysis of Aggregated ARQ Protocols for IEEE 802.11n Networks Abstract: The design of wireless local area networks (WLANs) with enhanced throughput performance have attracted significant amounts of attention in recent years. Based on the IEEE 802.11n standard, frame aggregation is considered one of the major factors to improve the system performance of WLANs from the medium access control (MAC) perspective. In order to fulfill the requirements of high throughput performance, feasible design of automatic repeat request (ARQ) mechanisms becomes important for providing reliable data transmission. In this paper, two MAC-defined ARQ protocols are proposed to consider the effect from frame aggregation for the enhancement of network throughput. An aggregated selective repeat ARQ (ASR-ARQ) scheme is proposed which incorporates the selective repeat ARQ scheme with the consideration of frame aggregation. On the other hand, for worse channel quality, the aggregated hybrid ARQ (AH-ARQ) mechanism is proposed to further enhance the throughput performance by adopting the Reed-Solomon (RS) block code as forward error correction (FEC) scheme. Novel analytical models for both the ASR-ARQ and AH-ARQ protocols are established with the consideration of interfering wireless stations. Simulations are conducted to validate and compare the proposed ARQ mechanisms based on the service time distribution and system throughput. Numerical evaluations show that the proposed AH-ARQ protocol can outperform the other schemes under worse channel condition; while the ASR-ARQ scheme is superior to the other mechanisms under better channel
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, condition. ETPL MC-070 United We Stand: Intrusion Resilience in Mobile Unattended WSNs Abstract: Wireless Sensor Networks (WSNs) are susceptible to a wide range of attacks due to their distributed nature, limited sensor resources, and lack of tamper resistance. Once a sensor is corrupted, the adversary learns all secrets. Thereafter, most security measures become ineffective. Recovering secrecy after compromise requires either help from a trusted third party or access to a source of high-quality cryptographic randomness. Neither is available in Unattended Wireless Sensor Networks (UWSNs), where the sink visits the network periodically. Prior results have shown that sensor collaboration is an effective but expensive means of obtaining probabilistic intrusion resilience in static UWSNs. In this paper, we focus on intrusion resilience in Mobile Unattended Wireless Sensor Networks (μUWSNs), where sensors move according to some mobility models. Note that such a mobility feature could be independent from security (e.g., sensors move to improve area coverage). We define novel security metrics to evaluate intrusion resilience protocols for sensor networks. We also propose a cooperative protocol that - by leveraging sensor mobility - allows compromised sensors to recover secure state after compromise. This is obtained with very low overhead and in a fully distributed fashion. Thorough analysis and extensive simulations support our findings. ETPL MC-071 Channel Assignment for Throughput Optimization in Multichannel Multiradio Wireless Mesh Networks Using Network Coding Abstract: Compared to single-hop networks such as WiFi, multihop infrastructure wireless mesh networks (WMNs) can potentially embrace the broadcast benefits of a wireless medium in a more flexible manner. Rather than being point-to-point, links in the WMNs may originate from a single node and reach more than one other node. Nodes located farther than a one-hop distance and overhearing such transmissions may opportunistically help relay packets for previous hops. This phenomenon is called opportunistic overhearing/listening. With multiple radios, a node can also improve its capacity by transmitting over multiple radios simultaneously using orthogonal channels. Capitalizing on these potential advantages requires effective routing and efficient mapping of channels to radios (channel assignment (CA)). While efficient channel assignment can greatly reduce interference from nearby transmitters, effective routing can potentially relieve congestion on paths to the infrastructure. Routing, however, requires that only packets pertaining to a particular connection be routed on a predetermined route. Random network coding (RNC) breaks this constraint by allowing nodes to randomly mix packets overheard so far before forwarding. A relay node thus only needs to know how many packets, and not which packets, it should send. We mathematically formulate the joint problem of random network coding, channel assignment, and broadcast link scheduling, taking into account opportunistic overhearing, the interference constraints, the coding constraints, the number of orthogonal channels, the number of radios per node, and fairness among unicast connections. Based on this formulation, we develop a suboptimal, auction-based solution for overall network throughput optimization. Performance evaluation results show that our algorithm can effectively exploit multiple radios and channels and can cope with fairness issues arising from auctions. Our algorithm also shows promising gains over traditional routing- solutions in which various channel assignment strategies are used. ETPL MC-072 Uplink Power Control via Adaptive Hidden-Markov-Model-Based Pathloss Estimation Abstract: Dynamic variations in channel behavior is considered in transmission power control design for cellular radio systems. It is well known that power control increases system capacity, improves Quality of Service (QoS), and reduces multiuser interference. In this paper, an adaptive power control design based
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, on the identification of the underlying pathloss dynamics of the fading channel is presented. Formulating power control decisions based on the measured received power levels allows modeling the fading channel pathloss dynamics in terms of a Hidden Markov Model (HMM). Applying the online HMM identification algorithm enables accurate estimation of the real pathloss ensuring efficient performance of the suggested power control scheme. ETPL MC-073 Bridging the Gap between Protocol and Physical Models for Wireless Networks Abstract: This paper tries to reconcile the tension between the physical model and the protocol model that have been used to characterize interference relationship in a multihop wireless network. The physical model (a.k.a. signal-to-interference-and-noise ratio model) is widely considered as a reference model for physical layer behavior but its application in multihop wireless networks is limited by its complexity. On the other hand, the protocol model (a.k.a. disk graph model) is simple but there have been doubts on its validity. This paper explores the following fundamental question: How to correctly use the protocol interference model? We show that, in general, solutions obtained under the protocol model may be infeasible and, thus, results based on blind use of protocol model can be misleading. We propose a new concept called "reality check” and present a method of using a protocol model with reality check for wireless networks. Subsequently, we show that by appropriate setting of the interference range in the protocol model, it is possible to narrow the solution gap between the two models. Our simulation results confirm that this gap is indeed small (or even negligible). Thus, our methodology of joint reality check and interference range setting retains the protocol model as a viable approach to analyze multihop wireless networks. ETPL MC-074 Effective Video Multicast Using SVC with Heterogeneous User Demands over TDMA- Based Wireless Mesh Networks Abstract: We provide an effective video multicast framework over time division multiple access (TDMA)-based wireless mesh networks (WMNs). Heterogeneous user demand is considered where each multicast receiver has its own video quality demand. In video multicasting, different relay nodes in the same multicast tree may have different transmission rates by utilizing scalable video coding (SVC). Considering this distinguishing characteristic of video multicasting, the proposed multicast framework provides effective multicast routing, scheduling, and rate allocation algorithms. The purpose of the multicast routing and scheduling is to obtain a minimum length schedule which satisfies given quality demands of receivers. If the schedule is not feasible even with its minimum length due to the limited number of time slots in the network, rate allocation algorithm adjusts the transmission rates of relay nodes to generate a feasible schedule. The algorithm is designed to maximize the minimum utility of multicast receivers. Simulation results show that the proposed multicast routing and scheduling algorithms outperform existing schemes in terms of schedule length. The minimum utility is improved up to 30 percent by the proposed rate allocation algorithm compared to the existing method. ETPL MC-075 Vampire Attacks: Draining Life from Wireless Ad Hoc Sensor Networks Abstract: Ad hoc low-power wireless networks are an exciting research direction in sensing and pervasive computing. Prior security work in this area has focused primarily on denial of communication at the routing or medium access control levels. This paper explores resource depletion attacks at the routing protocol layer, which permanently disable networks by quickly draining nodes' battery power. These "Vampire” attacks are not specific to any specific protocol, but rather rely on the properties of many popular classes of routing protocols. We find that all examined protocols are susceptible to Vampire attacks, which are devastating, difficult to detect, and are easy to carry out using as few as one malicious insider sending only protocol-compliant messages. In the worst case, a single Vampire can increase
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, network-wide energy usage by a factor of O(N), where N in the number of network nodes. We discuss methods to mitigate these types of attacks, including a new proof-of-concept protocol that provably bounds the damage caused by Vampires during the packet forwarding phase. ETPL MC-076 On the Real-Time Hardware Implementation Feasibility of Joint Radio Resource Management Policies for Heterogeneous Wireless Networks Abstract: The study and design of Joint Radio Resource Management (JRRM) techniques is a key and challenging aspect in future heterogeneous wireless systems where different Radio Access Technologies (RAT) will physically coexist. In these systems, the total available radio resources need to be used in a coordinated way to guarantee adequate satisfaction levels to all users, and maximize the system revenues. In addition to carry out an efficient use of the available radio resources, JRRM algorithms need to exhibit good computational performance to guarantee their future implementation viability. In this context, this paper proposes novel JRRM techniques based on linear programming techniques, and investigates their computational cost when implemented in DSP platforms commonly used in mobile-based stations. The obtained results demonstrate the feasibility to implement the proposed JRRM algorithms in future heterogeneous wireless systems. ETPL MC-077 Robust Distributed Power Control in Cognitive Radio Networks Abstract: We propose a robust distributed uplink power allocation algorithm for underlay cognitive radio networks (CRNs) with a view to maximizing the social utility of secondary users (SUs) when channel gains from SUs to primary base stations, and interference caused by primary users (PUs) to the SUs' base station are uncertain. In doing so, we utilize the worst case robust optimization to keep the interference caused by SUs to each primary base station below a given threshold, and satisfy each SU's quality of service in terms of its required SINR for all realizations of uncertain parameters. We model each uncertain parameter by a bounded distance between its estimated and exact values, and formulate the robust power allocation problem via protection values for constraints. We demonstrate that the convexity of our problem is preserved, and converts into a geometric programming problem, which we solve via a distributed algorithm by using Lagrange dual decomposition. To reduce the cost of robustness, defined as the reduction in the social utility of SUs and the increase in message passing, we utilize the D-norm approach to trade off between robustness and optimality, and propose a distributed power allocation algorithm with infrequent message passing. Simulation results validate the effectiveness of our proposed approach. ETPL MC-078 A Probabilistic Place Extraction Algorithm Based on a Superstate Model Abstract: Research on place extraction has been of interest for the detection of meaningful places that users visit. Because interpretations of meaningful places may be different according to location-based applications, a universal place extraction algorithm that is able to detect all kinds of meaningful places needs to be developed. Unfortunately, most previously proposed place extraction algorithms failed to show high place detection accuracy and also failed to perfectly detect meaningful places. In this work, we propose a new place extraction algorithm that can significantly enhance the accuracy of place extraction. The basic concept of the proposed algorithm is a superstate model, which is an extension of the Hidden Markov Model (HMM); we substituted superstates for the simple probabilistic distributions of the HMM. Our proposed algorithm shows remarkable detection accuracy in place extraction, significantly higher than any other previously proposed algorithms. Furthermore, the proposed algorithm can efficiently operate in mobile environments because its computations are simple. ETPL MC-079 Secret Key Extraction from Wireless Signal Strength in Real Environments
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: We evaluate the effectiveness of secret key extraction, for private communication between two wireless devices, from the received signal strength (RSS) variations on the wireless channel between the two devices. We use real world measurements of RSS in a variety of environments and settings. The results from our experiments with 802.11-based laptops show that 1) in certain environments, due to lack of variations in the wireless channel, the extracted bits have very low entropy making these bits unsuitable for a secret key, 2) an adversary can cause predictable key generation in these static environments, and 3) in dynamic scenarios where the two devices are mobile, and/or where there is a significant movement in the environment, high entropy bits are obtained fairly quickly. Building on the strengths of existing secret key extraction approaches, we develop an environment adaptive secret key generation scheme that uses an adaptive lossy quantizer in conjunction with Cascade-based information reconciliation and privacy amplification. Our measurements show that our scheme, in comparison to the existing ones that we evaluate, performs the best in terms of generating high entropy bits at a high bit rate. The secret key bit streams generated by our scheme also pass the randomness tests of the NIST test suite that we conduct. We also build and evaluate the performance of secret key extraction using small, low- power, hand-held devices—Google Nexus One phones—that are equipped 802.11 wireless network cards. Last, we evaluate secret key extraction in a multiple input multiple output (MIMO)-like sensor network testbed that we create using multiple TelosB sensor nodes. We find that our MIMO-like sensor environment produces prohibitively high bit mismatch, which we address using an iterative distillation stage that we add to the key extraction process. Ultimately, we show that the secret key generation rate is increased when multiple sensors are involved- in the key extraction process. ETPL MC-080 Toward a Statistical Framework for Source Anonymity in Sensor Networks Abstract: In certain applications, the locations of events reported by a sensor network need to remain anonymous. That is, unauthorized observers must be unable to detect the origin of such events by analyzing the network traffic. Known as the source anonymity problem, this problem has emerged as an important topic in the security of wireless sensor networks, with variety of techniques based on different adversarial assumptions being proposed. In this work, we present a new framework for modeling, analyzing, and evaluating anonymity in sensor networks. The novelty of the proposed framework is twofold: first, it introduces the notion of "interval indistinguishability” and provides a quantitative measure to model anonymity in wireless sensor networks; second, it maps source anonymity to the statistical problem of binary hypothesis testing with nuisance parameters. We then analyze existing solutions for designing anonymous sensor networks using the proposed model. We show how mapping source anonymity to binary hypothesis testing with nuisance parameters leads to converting the problem of exposing private source information into searching for an appropriate data transformation that removes or minimize the effect of the nuisance information. By doing so, we transform the problem from analyzing real-valued sample points to binary codes, which opens the door for coding theory to be incorporated into the study of anonymous sensor networks. Finally, we discuss how existing solutions can be modified to improve their anonymity ETPL MC-081 Successive Interference Cancellation: Carving Out MAC Layer Opportunities Abstract: Successive interference cancellation (SIC) is a PHY capability that allows a receiver to decode packets that arrive simultaneously. While the technique is well known in communications literature, emerging software radio platforms are making practical experimentation feasible. This motivates us to study the extent of throughput gains possible with SIC from a MAC layer perspective and scenarios where such gains are worth pursuing. We find that contrary to our initial expectation, the gains are not high when the bits of interfering signals are not known a priori to the receiver. Moreover, we observe that the scope for SIC gets squeezed by the advances in bitrate adaptation. In particular, our analysis shows
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, that interfering one-to-one transmissions benefit less from SIC than scenarios with many-to-one transmissions (such as when clients upload data to a common access point). In view of this, we develop an SIC-aware scheduling algorithm that employs client pairing and power reduction to extract the most gains from SIC. We believe that our findings will be useful guidelines for moving forward with SIC- aware protocol research. ETPL MC-082 Studying Smartphone Usage: Lessons from a Four-Month Field Study Abstract: Many emerging mobile applications and services are based on smartphones. We have performed a four-month field study of the adoption and usage of smartphone-based services by 14 novice teenage users. From the field study, we present the application usage and usage characteristics of our participants. We show that their usage is highly mobile, location-dependent, and serves multiple social purposes. Furthermore, we report qualitative lessons regarding the evaluation of smartphone-based services. In particular, we highlight the cases that an accurate evaluation would require a long-term and/or field study instead of a short or lab-based study, and the cases where studying a particular application independently is insufficient and a holistic study, i.e., involving the whole device, is necessary. We further present guidelines on effectively shortening the length of a study. These lessons are supported in part by five identified contributing factors to usage evolution. ETPL MC-083 Model-Based Analysis of Wireless System Architectures for Real-Time Applications Abstract: We propose a model-based description and analysis framework for the design of wireless system architectures. Its aim is to address the shortcomings of existing approaches to system verification and the tracking of anomalies in safety-critical wireless systems. We use Architecture Analysis and Description Language (AADL) to describe an analysis-oriented architecture model with highly modular components. We also develop the cooperative tool chains required to analyze the performance of a wireless system by simulation. We show how this framework can support a detailed and largely automated analysis of a complicated, networked wireless system using examples from wireless healthcare and video broadcasting. ETPL MC-084 On Centralized and Localized Approximation Algorithms for Interference-Aware Broadcast Scheduling Abstract: Broadcast scheduling in multihop Wireless Sensor Networks (WSNs) is an effective mechanism to perform interference-aware broadcasting. Existing works provide centralized solutions, which cannot be implemented locally. Additionally, they consider very elementary network and interference models, in which, either all sensor nodes have the same transmission range or their transmission ranges are equal to their interference ranges that are not very practical. Furthermore, they entirely ignore the existence of WSNs in 3D. In this paper, we study the broadcast scheduling in 2D and 3D WSNs. We consider that sensor nodes may have different transmission ranges and their interference ranges are α times of their transmission ranges (where α >; 1). We devise efficient coloring methods for coloring a hexagonal tiling in 2D plane and a truncated octahedron tiling in 3D space, based on which we propose O(1)-centralized approximation algorithms and O(1)-localized approximation algorithms for the broadcast scheduling problem in 2D and 3D WSNs, respectively. Our O(1)-centralized approximation algorithms for 3D WSNs and O(1)-localized approximation algorithms for 2D and 3D WSNs are the first approximation algorithms for the corresponding problems. Finally, we present an efficient greedy heuristic to study the effect of various priority metrics for greedily scheduling multiple interfering transmissions. Theoretical analysis and experimental results are provided to evaluate the performance of our algorithms. ETPL MC-085 Nuzzer: A Large-Scale Device-Free Passive Localization System for Wireless Environments
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: The widespread usage of WLANs and mobile devices has fostered the interest in localization systems for wireless environments. The majority of research in the context of wireless-based localization systems has focused on device-based active localization, in which devices are attached to tracked entities. Recently, device-free passive localization (DfP) has been proposed where the tracked entity is neither required to carry devices nor to participate actively in the localization process. Previous studies have focused on small areas and/or controlled environments. In this paper, we present the design, implementation, and analysis of Nuzzer, a large-scale DfP localization system, which tracks entities in real environments, rich in multipath. We first present probabilistic techniques for DfP localization of a single entity and evaluate their performance both analytically and in typical office buildings. Our results show that Nuzzer gives location estimates with less than 2-meters median distance error. We then give an algorithm for estimating the number of entities in an area of interest and localizing them into coarse- grained zones to enhance the scalability of the system. This indicates the suitability of Nuzzer to a large number of application domains. keywords: {mobile radio;probability;Nuzzer;WLAN;large scale device-free passive localization system;office building;probabilistic technique;wireless ETPL MC-086 Dynamic Control of Receiver Buffers in Mobile Video Streaming Systems Abstract: We propose a novel algorithm to efficiently transmit multiple Variable-Bit-Rate (VBR) video streams from a base station to mobile receivers in wide-area wireless networks. The algorithm multicasts video streams in bursts to save the energy of mobile devices. In addition, the algorithm adaptively controls the buffer levels of mobile devices receiving different video streams according to the bit rate of the video stream being received by each device. Compared to previous algorithms, the new algorithm enables dynamic control of the wireless channel and allows the base station to transmit more video data on time to mobile receivers. This is done by providing finer control over the bandwidth allocation of the wireless channel. The problem of optimizing energy saving has been shown to be NP-Complete. We prove that our algorithm finds a feasible schedule if one exists and always produces a correct schedule even when dropped frames are unavoidable. We analytically bound the gap between the energy saving resulting from our algorithm and the optimal energy saving and show that our results are close to optimal. We analyze the tradeoff between the fine control over bandwidth allocation and energy saving and demonstrate that in practical situations, flexible and finer control of bandwidth allocation will result in significantly lower frame loss rates while achieving higher energy saving. We have implemented the proposed algorithm as well as two other recent algorithms in a mobile video streaming testbed. Our extensive analysis and results demonstrate that the proposed algorithm outperforms the other two algorithms; it results in higher energy saving for mobile devices and fewer dropped video frames. ETPL MC-087 "Secure Communication Based on Ambient Audio Abstract: We propose to establish a secure communication channel among devices based on similar audio patterns. Features from ambient audio are used to generate a shared cryptographic key between devices without exchanging information about the ambient audio itself or the features utilized for the key generation process. We explore a common audio-fingerprinting approach and account for the noise in the derived fingerprints by employing error correcting codes. This fuzzy-cryptography scheme enables the adaptation of a specific value for the tolerated noise among fingerprints based on environmental conditions by altering the parameters of the error correction and the length of the audio samples utilized. In this paper, we experimentally verify the feasibility of the protocol in four different realistic settings and a laboratory experiment. The case studies include an office setting, a scenario where an attacker is capable of reproducing parts of the audio context, a setting near a traffic loaded road, and a crowded canteen environment. We apply statistical tests to show that the entropy of fingerprints based on ambient audio is
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, high. The proposed scheme constitutes a totally unobtrusive but cryptographically strong security mechanism based on contextual information. ETPL MC-088 Asymptotic Minimum Coverage Using Macroscopic Diversity Abstract: The optimal geometric configuration of the cells of a wireless network using multiple antennas for each base station and a macrodiversity technique is investigated. The simplest model of a cell of an existing wireless network is disk shaped, and the cell deployment is arranged in a honeycomb tiling pattern. This model has been used as the first-order approximation for designing and evaluating wireless networks. However, the cells of a network using multiple antennas and macrodiversity are no longer disk shaped. This study investigated a network with a cell-and-antenna deployment pattern that covers a given service area using the minimum number of cells. The objective of this paper is to offer a first-order approximation model for a cell-and-antenna deployment pattern of such a network. For this objective, first, by imposing practical conditions, cell-and-antenna deployment patterns are classified. Then, the asymptotic minimum coverage problem is formulated as an optimization problem with a constraint for a set of deployment patterns. To easily obtain the first-order approximation model, a simplified formulation and model are proposed. Numerical examples show that the proposed deployment pattern covers the service area with nearly half the cells required by the existing heuristic pattern. ETPL MC-089 Effective Carrier Sensing in CSMA Networks under Cumulative Interference Abstract: This paper proposes the concept of safe carrier-sensing range under the cumulative interference model that guarantees interference-safe (also known as hidden-node-free) transmissions in CSMA networks. Compared with a previous related concept of safe carrier-sensing range under the commonly assumed but less realistic pairwise interference model, we show that the safe carrier-sensing range under the cumulative interference model is larger by a constant multiplicative factor. For example, the factor is 1.4 if the SINR requirement is 10 dB and the path-loss exponent is 4 in a noiseless case. We further show that the concept of a safe carrier-sensing range, although amenable to elegant analytical results, is inherently not compatible with the conventional power-threshold carrier-sensing mechanism (e.g., that used in IEEE 802.11). Specifically, the absolute power sensed by a node in the conventional carrier- sensing mechanism does not contain enough information for the node to derive its distances from other concurrent transmitting nodes. We show that, fortunately, a new carrier-sensing mechanism called Incremental-Power Carrier-Sensing (IPCS) can realize the carrier-sensing range concept in a simple way. Instead of monitoring the absolute detected power, the IPCS mechanism monitors every increment in the detected power. This means that IPCS can separate the detected power of every concurrent transmitter, and map the power profile to the required distance information. Our extensive simulation results indicate that IPCS can boost spatial reuse and network throughput by up to 60 percent relative to the conventional carrier-sensing mechanism under the same carrier-sensing power thresholds. If we compare the maximum throughput in the interference-free regime, the throughput improvement of IPCS is still more than 15 percent. Last but not least, IPCS not only allows us to implement the safe carrier-sensing range, but also ties up a loose end in many other prior theoretical work- that implicitly used a carrier-sensing range (interference-safe or otherwise) without an explicit design to realize it. ETPL MC-090 HAPPE: Human and Application-Driven Frequency Scaling for Processor Power Efficiency Abstract: Conventional dynamic voltage and frequency scaling techniques use high CPU utilization as a predictor for user dissatisfaction, to which they react by increasing CPU frequency. In this paper, we demonstrate that for many interactive applications, perceived performance is highly dependent upon the particular user and application, and is not linearly related to CPU utilization. This observation reveals an
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, opportunity for reducing power consumption. We propose Human and Application driven frequency scaling for Processor Power Efficiency (HAPPE), an adaptive user-and-application-aware dynamic CPU frequency scaling technique. HAPPE continuously adapts processor frequency and voltage to the learned performance requirement of the current user and application. Adaptation to user requirements is quick and requires minimal effort from the user (typically a handful of key strokes). Once the system has adapted to the user's performance requirements, the user is not required to provide continued feedback but is permitted to provide additional feedback to adjust the control policy to changes in preferences. HAPPE was implemented on a Linux-based laptop and evaluated in 22 hours of controlled user studies. Compared to the default Linux CPU frequency controller, HAPPE reduces the measured system-wide power consumption of CPU-intensive interactive applications by 25 percent on average while maintaining user satisfaction. ETPL MC-091 Low-Complexity Class-Based Scheduling Algorithm for Scheduled Automatic Power- Save Delivery for Wireless LANs Abstract: Power saving is an important issue when integrating the wireless LAN technology into mobile devices. Besides Quality of Service (QoS) guarantee, the IEEE 802.11e introduces an architecture called Scheduled Automatic Power-Save Delivery (S-APSD) aiming at delivering buffered frames to power save stations. In S-APSD, the Access Point (AP) schedules the Service Period (SP) of stations. To increase power efficiency, SPs should be scheduled to minimize the chance of overlapping. In a recent paper, an algorithm named Overlapping Aware S-APSD (OAS-APSD) was proposed to find the wake-up time schedule for a new Traffic Stream (TS) to minimize the chance of SP overlapping. The combination of OAS-APSD and HCF Controlled Channel Access (HCCA) was proved to outperform 802.11 Power Save Mode (PSM) with Enhanced Distributed Channel Access (EDCA) in power saving efficiency and QoS support. However, the OAS-APSD algorithm requires high online computational complexity which could make it infeasible for real systems. Without harming the optimality, this paper presents an efficient algorithm with much less complexity by exploiting the periodicity of service schedule. Because of largely reduced online computational complexity, the proposed algorithm is much more feasible than OAS- APSD. ETPL MC-092 On Exploiting Transient Social Contact Patterns for Data Forwarding in Delay- Tolerant Networks Abstract: Unpredictable node mobility, low node density, and lack of global information make it challenging to achieve effective data forwarding in Delay-Tolerant Networks (DTNs). Most of the current data forwarding schemes choose the nodes with the best cumulative capability of contacting others as relays to carry and forward data, but these nodes may not be the best relay choices within a short time period due to the heterogeneity of transient node contact characteristics. In this paper, we propose a novel approach to improve the performance of data forwarding with a short time constraint in DTNs by exploiting the transient social contact patterns. These patterns represent the transient characteristics of contact distribution, network connectivity and social community structure in DTNs, and we provide analytical formulations on these patterns based on experimental studies of realistic DTN traces. We then propose appropriate forwarding metrics based on these patterns to improve the effectiveness of data forwarding. When applied to various data forwarding strategies, our proposed forwarding metrics achieve much better performance compared to existing schemes with similar forwarding cost. ETPL MC-093 Pulse Switching: Toward a Packet-Less Protocol Paradigm for Event Sensing Abstract: This paper presents a novel pulse switching protocol framework for ultra light-weight wireless network applications. The key idea is to abstract a single Ultra Wide Band (UWB) pulse as the information switching granularity. Pulse switching is shown to be sufficient for on-off style event
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, monitoring applications for which a monitored parameter can be modeled using a binary variable. Monitoring such events with conventional packet transport can be prohibitively energy-inefficient due to the communication, processing, and buffering overheads of the large number of bits within a packet's data, header, and preambles for synchronization. The paper presents a joint MAC-routing protocol architecture for pulse switching with a novel hop-angular event localization strategy. Through analytical modeling and simulation-based experiments it is shown that pulse switching can be an effective means for event networking, which can potentially replace the traditional packet transport when the information to be transported is binary in nature. ETPL MC-094 Topological Persistence for Medium Access Control Abstract: The primary function of the medium access control (MAC) protocol is managing access to the shared communication channel. From the viewpoint of the transmitters, the MAC protocol determines each transmitter's channel occupancy, the fraction of time that it spends transmitting over the channel. In this paper, we define a set of topological persistences that conform to both network topology and traffic load. We employ these persistences as target occupancies for the MAC layer protocol. A centralized algorithm is developed for calculating topological persistences and its correctness is established. A distributed algorithm and implementation are developed that can operate within scheduled and contention-based MAC protocols. In the distributed algorithm, network resources are allocated through auctions at each receiver in which transmitters participate as bidders to converge on the topological allocation. Very low overhead is achieved by piggybacking auction and bidder communication on existing data packets. The practicality of the distributed algorithm is demonstrated in a wireless network via simulation using the ns-2 network simulator. Simulation results show fast convergence to the topological solution and, once operating with topological persistences, improved performance compared to IEEE 802.11 in delay, throughput, and drop rate. ETPL MC-095 Estimation of Task Persistence Parameters from Pervasive Medical Systems with Censored Data Abstract: This paper compares two statistical models of location within a smart flat during the day. The location is then identified with a task executed normally or repeated pathologically, e.g., in case of Alzheimer disease (AD), whereas a task persistence parameter assesses tendency to perseverate . Compared with a Pólya 's urns derived approach, the Markovian one is more effective and offers up to 98 percent of good prediction using only the last known location but distinguishing days of week. To extend these results to a multisensor context, some difficulties must be overcome. An external knowledge is made from a set of observable random variables provided by body sensors and organized either in a Bayesian network or in a reference knowledge base system (KBS) containing the person's actimetric profile. When data missed or errors occurred, an estimate of the joint probabilities of these random variables and hence the probability of all events appearing in the network or the KBS was developed and corrects the bias of the Lancaster and Zentgraf classical approach which in certain circumstances provides negative estimates. Finally, we introduce a correction corresponding to a possible loss of the person's synchronization with the nycthemeral (day versus night) zeitgebers (synchronizers) to avoid false alarms. ETPL MC-096 Deployment of a Connected Reinforced Backbone Network with a Limited Number of Backbone Nodes Abstract: In recent years, we have witnessed a surge of interest in enabling communications over meshed wireless networks. Particularly, supporting peer-to-peer communications over a multihop wireless network has great potential in enabling ubiquitous computing. However, many wireless nodes have limited capabilities, for example, sensor nodes or small handheld devices. Also, the end-to-end capacity and delay degrade significantly as the path length increases with the number of network nodes. In these
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, scenarios, the deployment of a backbone network could potentially facilitate higher performance network communications. In this paper, we study the novel reinforced backbone network (RBN) deployment problem considering the practical limitation in the number of available backbone nodes and enforcing backbone network connectivity. We propose an iterative and adaptive (ITA) algorithm for efficient backbone network deployment. In addition, in order to provide the performance bound, we redefine and solve the problem by implementing the genetic algorithm. Finally, we present our simulation results under various settings and compare the performance of the proposed ITA algorithm and the genetic algorithm. Our study indicates that the proposed ITA algorithm is promising for deploying a connected RBN with a limited number of available backbone nodes. ETPL MC-097 Design and Analysis of Adaptive Receiver Transmission Protocols for Receiver Blocking Problem in Wireless Ad Hoc Networks Abstract: Due to the lack of a centralized coordinator for wireless resource allocation, the design of medium access control (MAC) protocols is considered crucial for throughput enhancement in the wireless ad hoc networks. The receiver blocking problem, which has not been studied in most of the MAC protocol design, can lead to severe degradation on the throughput performance. In this paper, the multiple receiver transmission (MRT) and the fast NAV truncation (FNT) mechanisms are proposed to alleviate the receiver blocking problem without the adoption of additional control channels. The adaptive receiver transmission (ART) scheme is proposed to further enhance the throughput performance with dynamic adjustment of the selected receivers. Analytical model is also derived to validate the effectiveness of the proposed ART protocol. Simulations are performed to evaluate and compare the proposed three protocols with existing MAC schemes. It can be observed that the proposed ART protocol outperforms the other schemes by both alleviating the receiver blocking problem and enhancing the throughput performance for the wireless multihop ad hoc networks. ETPL MC-098 Geometry-Assisted Localization Algorithms for Wireless Networks Abstract: Linear estimators have been extensively utilized for wireless location estimation for their simplicity and closed form property. In the paper, the class of linear estimator by introducing an additional variable, e.g., the well-adopted linear least squares (LLS) estimator, is discussed. There exists information loss from the linearization of location estimator to the nonlinear location estimation , which prevents the linear estimator from approaching the Cramér -Rao lower bound (CRLB). The linearized location estimation problem-based CRLB (L-CRLB) is derived in this paper to provide a portrayal that can fully characterize the behavior for this type of linearized location estimator. The relationships between the proposed L-CRLB and the conventional CRLB are obtained and theoretically proven in this paper. As suggested by the L-CRLB, higher estimation accuracy can be achieved if the mobile station (MS) is located inside the convex hull of the base stations (BSs) compared to the case that the MS is situated outside of the geometric layout. This result motivates the proposal of geometry-assisted localization (GAL) algorithm in order to consider the geometric effect associated with the linearization loss. Based on the initial estimation, the GAL algorithm fictitiously moves the BSs based on the L-CRLB criteria. Two different implementations, including the GAL with two-step least squares estimator (GAL- TSLS) and the GAL with Kalman filter (GAL-KF), are proposed to consider the situations with and without the adoption of MS's historical estimation. Simulation results show that the GAL-KF scheme can compensate the linearization loss and improve the performance of conventional location estimators. ETPL MC-099 Proteus: Multiflow Diversity Routing for Wireless Networks with Cooperative Transmissions Abstract: In this paper, we consider the use of cooperative transmissions in multihop wireless networks to achieve Virtual Multiple Input Single Output (VMISO) links. Specifically, we investigate how the
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, physical layer VMISO benefits translate into network level performance improvements. We show that the improvements are nontrivial (15 to 300 percent depending on the node density) but rely on two crucial algorithmic decisions: the number of cooperating transmitters for each link; and the cooperation strategy used by the transmitters. We explore the tradeoffs in making routing decisions using analytical models and derive the key routing considerations. Finally, we present Proteus, an adaptive diversity routing protocol that includes algorithmic solutions to the above two decision problems and leverages VMISO links in multihop wireless network to achieve performance improvements. We evaluate Proteus using NS2-based simulations with an enhanced physical layer model that accurately captures the effect of VMISO transmissions. ETPL MC-100 Passive Measurement of Interference in WiFi Networks with Application in Misbehavior Detection Abstract: We present a tool to estimate the interference between nodes and links in a live wireless network by passive monitoring of wireless traffic. This tool does not require any controlled experiments, injection of probe traffic in the network, or even access to the network nodes. Our approach requires deploying multiple sniffers across the network to capture wireless traffic traces. These traces are then analyzed using a machine learning approach to infer the carrier-sense relationship between network nodes. This coupled with an estimation of collision probabilities helps us to deduce the interference relationships. We also demonstrate an important application of this tool-detection of selfish carrier-sense behavior. This is based on identifying any asymmetry in carrier-sense behavior between node pairs and finding multiple witnesses to raise confidence. We evaluate the effectiveness of the tool for both the applications using extensive experiments and simulation. Experimental and simulation results demonstrate that the proposed approach of estimating interference relations is significantly more accurate than simpler heuristics and quite competitive with active measurements. We also validate the approach in a real Wireless LAN environment. Evaluations using a real testbed as well as ns2 simulation studies demonstrate excellent detection ability of the selfish behavior. On the other hand, the metric of selfishness used to estimate selfish behavior matches closely with actual degree of selfishness observed. ETPL MC-101 Toward History-Aware Robust 802.11 Rate Adaptation Abstract: Rate adaptation is a mechanism unspecified by the IEEE 802.11 standards, yet critical to the system performance by exploiting the multirate capability at the physical layer. In this paper, we conduct a systematic experimental study on rate adaptation over 802.11 wireless networks. Our key contributions are as follows: First, we present a critique on popular design guidelines adopted by many practical algorithms and we uncover their limitations. Our study reveals that these seemingly correct guidelines can be misleading in practice, thus incurring significant performance penalty in certain scenarios. Second, we study the short-term channel dynamics and explore how they guide rate adaptation. To this end, we design and implement a new History-Aware Robust Rate Adaptation Algorithm (HA-RRAA). HA-RRAA uses short-term loss ratio to opportunistically guide its rate change decisions, a cost-effective adaptive RTS filter to prevent collision losses from triggering rate decrease and an adaptive time window to limit transmissions at high loss rates. Our extensive experiments show that HA-RRAA outperforms popular algorithms in all tested scenarios, with goodput gains up to 51.9 percent in field trials. ETPL MC-102 Scheduling Partition for Order Optimal Capacity in Large-Scale Wireless Networks Abstract: The capacity scaling property specifies the change of network throughput when network size increases. It serves as an essential performance metric in large-scale wireless networks. Existing results have been obtained based on the assumption of using a globally planned link transmission schedule in the network, which is however not feasible in large wireless networks due to the scheduling complexity. The
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, gap between the well-known capacity results and the infeasible assumption on link scheduling potentially undermines our understanding of the achievable network capacity. In this paper, we propose the scheduling partition methodology that decomposes a large network into small autonomous scheduling zones and implements a localized scheduling algorithm independently in each partition. We prove the sufficient and the necessary conditions for the scheduling partition approach to achieve the same order of capacity as the widely assumed global scheduling strategy. In comparison to the network dimension √(n), scheduling partition size n Θ(r(n)) is sufficient to obtain the optimal capacity scaling, where r(n) is the node transmission radius and much smaller than √(n). We n finally propose a distributed partition protocol and a localized scheduling algorithm as our scheduling solution for maximum capacity in large wireless networks. ETPL MC-103 Probability-Based Prediction and Sleep Scheduling for Energy-Efficient Target Tracking in Sensor Networks Abstract: A surveillance system, which tracks mobile targets, is one of the most important applications of wireless sensor networks. When nodes operate in a duty cycling mode, tracking performance can be improved if the target motion can be predicted and nodes along the trajectory can be proactively awakened. However, this will negatively influence the energy efficiency and constrain the benefits of duty cycling. In this paper, we present a Probability-based Prediction and Sleep Scheduling protocol (PPSS) to improve energy efficiency of proactive wake up. We start with designing a target prediction method based on both kinematics and probability. Based on the prediction results, PPSS then precisely selects the nodes to awaken and reduces their active time, so as to enhance energy efficiency with limited tracking performance loss. We evaluated the efficiency of PPSS with both simulation-based and implementation-based experiments. The experimental results show that compared to MCTA algorithm, PPSS improves energy efficiency by 25-45 percent (simulation based) and 16.9 percent (implementation based), only at the expense of an increase of 5-15 percent on the detection delay (simulation based) and 4.1 percent on the escape distance percentage (implementation based), respectively. ETPL MC-104 A Unified Analysis of IEEE 802.11 DCF Networks: Stability, Throughput, and Delay Abstract: In this paper, a unified analytical framework is established to study the stability, throughput, and delay performance of homogeneous buffered IEEE 802.11 networks with Distributed Coordination Function (DCF). Two steady-state operating points are characterized using the limiting probability of successful transmission of Head-of-Line (HOL) packets $(p)$ given that the network is in unsaturated or saturated conditions. The analysis shows that a buffered IEEE 802.11 DCF network operates at the desired stable point $(p=p_{L})$ if it is unsaturated. $(p_{L})$ does not vary with backoff parameters, and a stable throughput can be always achieved at $(p_{L})$. If the network becomes saturated, in contrast, it operates at the undesired stable point $(p=p_{A})$, and a stable throughput can be achieved at $(p_A)$ if and only if the backoff parameters are properly selected. The stable regions of the backoff factor $(q)$ and the initial backoff window size $(W)$ are derived, and illustrated in cases of the basic access mechanism and the request-to-send/clear-to-send (RTS/CTS) mechanism. It is shown that the stable regions are significantly enlarged with the RTS/CTS mechanism, indicating that networks in the RTS/CTS mode are much more robust. Nevertheless, the delay analysis further reveals that lower access delay is incurred in the basic access mode for unsaturated networks. If the network becomes saturated, the delay performance deteriorates regardless of which mode is chosen. Both the first and the second moments of access delay at $(p_A)$ are sensitive to the backoff parameters, and shown to be effectively reduced by enlarging the initial backoff window size $(W)$. ETPL MC-105 DSS: Distributed SINR-Based Scheduling Algorithm for Multihop Wireless Networks
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: The problem of developing distributed scheduling algorithms for high throughput in multihop wireless networks has been extensively studied in recent years. The design of a distributed low- complexity scheduling algorithm becomes even more challenging when taking into account a physical interference model, which requires the SINR at a receiver to be checked when making scheduling decisions. To do so, we need to check whether a transmission failure is caused by interference due to simultaneous transmissions from distant nodes. In this paper, we propose a scheduling algorithm under a physical interference model, which is amenable to distributed implementation with 802.11 CSMA technologies. The proposed scheduling algorithm is shown to achieve throughput optimality. We present two variations of the algorithm to enhance the delay performance and to reduce the control overhead, respectively, while retaining throughput optimality. ETPL MC-106 Video On-Demand Streaming in Cognitive Wireless Mesh Networks Abstract: Cognitive radio (CR), which enables dynamic access of underutilized licensed spectrums, is a promising technology for more efficient spectrum utilization. Since cognitive radio enables the access of larger amount of spectrum, it can be used to build wireless mesh networks with higher network capacity, and thus provide better quality of services for high bit-rate applications. In this paper, we study the multisource video on-demand application in multi-interface cognitive wireless mesh networks. Given a video request, we find a joint multipath routing and spectrum allocation for the session to minimize its total bandwidth cost in the network, and therefore maximize the number of sessions the network can support. We propose both distributed and centralized routing and channel allocation algorithms to solve the problem. Simulation results show that our algorithms increase the maximum number of concurrent sessions that can be supported in the network, and also improve each session's performance with regard to spectrum mobility. ETPL MC-107 Localization of RFID Tags Using Stochastic Tunneling Abstract: This paper presents a novel localization scheme in the 3D wireless domain that employs cross correlation in backscattered signal power from a cluster of radio frequency identification (RFID) tags to estimate their location. Spatially co-located RFID tags, energized by a common tag reader, exhibit correlation in their received signal strength indicator (RSSI) values. Hence, for a cluster of RFID tags, the posterior distribution of their unknown radial separation is derived as a function of the measured RSSI correlations between them. The global maxima of this posterior distribution represent the actual radial separation between the RFID tags. The radial separations are then utilized to obtain location estimates of the tags. However, due to the nonconvex nature of the posterior distribution, deterministic optimization methods that are used to solve true radial separations between tags provide inaccurate results due to local maxima, unless the initial radial separation estimates are within the region of attraction of its global maximum. The proposed RFID localization algorithm called LOCalization Using Stochastic Tunneling (LOCUST) utilizes constrained simulated annealing with tunneling transformation to solve this nonconvex posterior distribution. The tunneling transformation allows the optimization search operation to circumvent or “tunnel” through ill-shaped regions in the posterior distribution resulting in faster convergence to the global maximum. Finally, simulation results of our localization method are presented to demonstrate the theoretical conclusions. ETPL MC-108 Channel Allocation and Routing in Hybrid Multichannel Multiradio Wireless Mesh Networks Abstract: Many efforts have been devoted to maximizing network throughput in a multichannel multiradio wireless mesh network. Most current solutions are based on either purely static or purely
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, dynamic channel allocation approaches. In this paper, we propose a hybrid multichannel multiradio wireless mesh networking architecture, where each mesh node has both static and dynamic interfaces. We first present an Adaptive Dynamic Channel Allocation protocol (ADCA), which considers optimization for both throughput and delay in the channel assignment. In addition, we also propose an Interference and Congestion Aware Routing protocol (ICAR) in the hybrid network with both static and dynamic links, which balances the channel usage in the network. Our simulation results show that compared to previous works, ADCA reduces the packet delay considerably without degrading the network throughput. The hybrid architecture shows much better adaptivity to changing traffic than purely static architecture without dramatic increase in overhead, and achieves lower delay than existing approaches for hybrid networks. ETPL MC-109 Delay-Optimal Broadcast for Multihop Wireless Networks Using Self-Interference Cancellation Abstract: Conventional wireless broadcast protocols rely heavily on the 802.11-based CSMA/CA model, which avoids interference and collision by conservative scheduling of transmissions. While CSMA/CA is amenable to multiple concurrent unicasts, it tends to degrade broadcast performance significantly, especially in lossy and large-scale networks. In this paper, we propose a new protocol called Chorus that improves the efficiency and scalability of broadcast service with a MAC/PHY layer that allows packet collisions. Chorus is built upon the observation that packets carrying the same data can be effectively detected and decoded, even when they overlap with each other and have comparable signal strengths. It resolves collision using symbol-level interference cancellation, and then combines the resolved symbols to restore the packet. Such a collision-tolerant mechanism significantly improves the transmission diversity and spatial reuse in wireless broadcast. Chorus' MAC-layer cognitive sensing and scheduling scheme further facilitates the realization of such an advantage, resulting in an asymptotic broadcast delay that is proportional to the network radius. We evaluate Chorus' PHY-layer collision resolution mechanism with symbol-level simulation, and validate its network-level performance via ns-2, in comparison with a typical CSMA/CA-based broadcast protocol. Our evaluation validates Chorus's superior performance with respect to scalability, reliability, delay, etc., under a broad range of network scenarios (e.g., single/multiple broadcast sessions, static/mobile topologies). ETPL MC-110 Path Selection under Budget Constraints in Multihop Cognitive Radio Networks Abstract: Cognitive radio (CR) technology opens the licensed spectrum bands for opportunistic usage and initiates spectrum trading to improve the spectrum utilization. In this paper, we investigate the path selection problem in multihop cognitive radio networks (CRNs) under constraints on flow routing, link scheduling and CR source's budget. We extend the per-user-based spectrum trading in prior work to CR session-based spectrum trading, and effectively develop the spectrum trading mechanisms based on the cross-layer optimization in multihop CRNs. We introduce a new service provider, called secondary service provider (SSP), to help CR sessions to select the paths for packet delivery. Considering the price of bands and the potential returning of primary services at different CR links, the SSP purchases the licensed spectrum and jointly conducts flow routing and link scheduling under the budget constraints. We also propose a 4D conflict graph to characterize the conflict relationship among CR links and mathematically formulate the path selection problem under multiple constraints into an optimization problem with the objective of maximizing the end-to-end throughput. Due to the NP-hardness of the
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, problem, we have also developed a heuristic algorithm to find the approximate solution. ETPL MC-111 Enhanced Least-Squares Positioning Algorithm for Indoor Positioning Abstract: This paper presents an enhanced least-squares positioning algorithm for locating and tracking within indoor environments where multipath and nonline-of-sight propagation conditions predominate. The ranging errors are modeled as a zero-mean random component plus a bias component that is assumed to be a linear function of the range. Through minimizing the mean-square error of the position estimation, an expression for the optimal estimate of the bias parameter is obtained. Both range and pseudo-range- based positioning are considered. Simulations and experimentation are conducted which show that a significant accuracy gain can be achieved for range-based positioning using the enhanced least-squares algorithm. It is also observed that the pseudo-range-based least-squares algorithm is little affected by the choice of the bias parameter. The results demonstrate that the experimental 5.8-GHz ISM band positioning system can achieve positional accuracy of around half a meter when using the proposed algorithm. ETPL MC-112 Cooperative Wireless-Based Obstacle/Object Mapping and See-Through Capabilities in Robotic Networks Abstract: In this paper, we develop a theoretical and experimental framework for the mapping of obstacles (including occluded ones), in a robotic cooperative network, based on a small number of wireless channel measurements. This would allow the robots to map an area before entering it. We consider three approaches based on coordinated space, random space, and frequency sampling, and show how the robots can exploit the sparse representation of the map in space, wavelet or spatial variations, in order to build it with minimal sensing. We then show the underlying tradeoffs of all the possible sampling, sparsity and reconstruction techniques. Our simulation and experimental results show the feasibility and performance of the proposed framework. More specifically, using our experimental robotic platform, we show preliminary results in successfully mapping a number of real obstacles and having see- through capabilities with real structures, despite the practical challenges presented by multipath fading. ETPL MC-113 Optimal Online Sensing Sequence in Multichannel Cognitive Radio Networks Abstract: We address the problem of rapidly discovering spectrum opportunities for seamless service provisioning in cognitive radio networks (CRNs). In particular, we focus on multichannel communications via channel-bonding with heterogeneous channel characteristics of ON/OFF patterns, sensing time, and channel capacity. Using dynamic programming (DP), we derive an optimal online sensing sequence incurring a minimal opportunity-discovery delay, and propose a suboptimal sequence that presents a near-optimal performance while incurring significantly less computational overhead than the DP algorithm. To facilitate fast opportunity discovery, we also propose a channel-management strategy that maintains a list of backup channels to be used at building the optimal sequence. A hybrid of maximum likelihood (ML) and Bayesian inference is introduced as well for flexible estimation of ON/OFF channel-usage patterns, which selectively chooses the better between the two according to the frequency of sensing and ON/OFF durations. The performance of the proposed schemes, in terms of the opportunity-discovery delay, is evaluated via in-depth simulation, and for the scenarios we considered,
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, the proposed suboptimal sequence achieves a near-optimal performance with only an average of 0.5 percent difference from the optimal delay, and outperforms the previously proposed probabilistic scheme by up to 50.1 percent. In addition, the backup channel update scheme outperforms the no-update case by up to 49.9 percent. ETPL MC-114 Quality-Differentiated Video Multicast in Multirate Wireless Networks Abstract: Adaptation of modulation and transmission bit-rates for video multicast in a multirate wireless network is a challenging problem because of network dynamics, variable video bit-rates, and heterogeneous clients who may expect differentiated video qualities. Prior work on the leader-based schemes selects the transmission bit-rate that provides reliable transmission for the node that experiences the worst channel condition. However, this may penalize other nodes that can achieve a higher throughput by receiving at a higher rate. In this work, we investigate a rate-adaptive video multicast scheme that can provide heterogeneous clients differentiated visual qualities matching their channel conditions. We first propose a rate scheduling model that selects the optimal transmission bit-rate for each video frame to maximize the total visual quality for a multicast group subject to the minimum-visual-quality-guaranteed constraint. We then present a practical and easy-to-implement protocol, called QDM, which constructs a cluster-based structure to characterize node heterogeneity and adapts the transmission bit-rate to network dynamics based on video quality perceived by the representative cluster heads. Since QDM selects the rate by a sample-based technique, it is suitable for real-time streaming even without any preprocess. We show that QDM can adapt to network dynamics and variable video-bit rates efficiently, and produce a gain of 2-5 dB in terms of the average video quality as compared to the leader-based approach. ETPL MC-115 Analytical Framework for WLAN-Cellular Voice Handover Evaluation Abstract: The development of handheld mobile terminals (MT) capable of operating over both Wireless Local Area Networks (WLAN) and the cellular media is an important step toward the evolution of next- generation integrated networks. For real-time applications like voice, efficient vertical handover (VH) algorithms are required in maintaining a seamless connectivity and an acceptable level of quality for mobile users in heterogeneous environments. This paper proposes an analytical method for evaluating the performance of a VH algorithm that relies on the Received Signal Strength Indicator (RSSI) samples. The system model is portrayed upon addressing relevant factors that affect the quality and continuity of a voice call, and a set of performance metrics is proposed. A rigorous signal strength time series is utilized in characterizing the instantaneous decision metrics, and a novel intermediary system model, namely the N-model, is proposed to capture the large-scale shadowing effects. The performance of a generic algorithm that relies on the RSSI, which itself is susceptible to estimation error, is evaluated for an MT roaming in and out of the WLAN coverage area. Results obtained using the analytical expressions are validated by comparing them to that obtained through Monte Carlo simulation. ETPL MC-116 A Traffic-Aware Channel and Rate Reassignment Algorithm for Wireless Mesh Networks Abstract: Channel assignment is among the most challenging issues for multiradio wireless mesh networks, given the variety of objectives that can be pursued and the computational complexity of the resulting problems. The channel assignment problem has been also shown to be interdependent with the
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, routing problem, i.e., the problem to determine the amount of traffic flow to be routed on every link. Such a relationship raises the need to recompute the channel assignment every time the traffic pattern changes. However, channel assignment algorithms designed to assign channels from scratch will likely return a completely different configuration of radios, which would disrupt the network operation for the time required to switch to using the links established on the new channels. As shown by the experiments that we conducted, such a time may not be negligible, due to the resistance of routing protocols designed for wireless ad hoc and mesh networks to rapidly flagging a link as established/lost. Such a consideration, along with the observation that channel assignment algorithms may be suboptimal, led us to the design of a channel reassignment algorithm that takes the current channel assignment into account and attempts to cope with the new traffic pattern in the best manner possible while modifying the channel on a limited number of radios. In this paper, we illustrate such a channel reassignment algorithm and evaluate its performance by means of both simulations and experiments with real hardware. ETPL MC-116 TCP CRAHN: A Transport Control Protocol for Cognitive Radio Ad Hoc Networks Abstract: Cognitive Radio (CR) networks allow users to opportunistically transmit in the licensed spectrum bands, as long as the performance of the Primary Users (PUs) of the band is not degraded. Consequently, variation in spectrum availability with time and periodic spectrum sensing undertaken by the CR users have a pronounced effect on the higher layer protocol performance, such as at the transport layer. This paper investigates the limitations of classical TCP newReno in a CR ad hoc network environment, and proposes TCP CRAHN, a window-based TCP-friendly protocol. Our approach incorporates spectrum awareness by a combination of explicit feedback from the intermediate nodes and the destination. This is achieved by adapting the classical TCP rate control algorithm running at the source to closely interact with the physical layer channel information, the link layer functions of spectrum sensing and buffer management, and a predictive mobility framework that is developed at the network layer. An analysis of the expected throughput in TCP CRAHN is provided, and simulation results reveal significant improvements by using our approach. To the best of our knowledge, our approach takes the first steps toward the design of a transport layer for CR ad hoc networks. ETPL MC-117 Hearing Is Believing: Detecting Wireless Microphone Emulation Attacks in White Space Abstract: In cognitive radio networks, an attacker transmits signals mimicking the characteristics of primary signals, in order to prevent secondary users from transmitting. Such an attack is called primary user emulation (PUE) attack. TV towers and wireless microphones are two main types of primary users in white space. Existing work on PUE attack detection only focused on the first category. For the latter category, primary users are mobile and their transmission power is low. These properties introduce great challenges on PUE detection and existing methods are not applicable. In this paper, we propose a novel method to detect the emulation attack of wireless microphones. We exploit the relationship between RF signals and acoustic information to verify the existence of wireless microphones. The effectiveness of our approach is validated through real-world implementation. Extensive experiments show that our method achieves both false positive rate and false negative rate lower than 0.1 even in a noisy environment. ETPL MC-118 UACAP: A Unified Auxiliary Channel Authentication Protocol
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, Abstract: Authenticating spontaneous interactions between devices and users is challenging for several reasons: the wireless (and therefore invisible) nature of device communication, the heterogeneous nature of devices, and lack of appropriate user interfaces in mobile devices, and the requirement for unobtrusive user interaction. The most promising approach that has been proposed in literature involves the exploitation of the so-called auxiliary channels for authentication to bridge the gap between usability and security. This concept has spawned the independent development of various authentication methods and research prototypes, that, unfortunately, remain hard to compare and interchange and are rarely available to potential application developers. We present a novel, unified cryptographic authentication protocol framework (UACAP) to unify these approaches on using auxiliary channels and analyze its security properties. This protocol and a selection of auxiliary channels aimed at authentication of mobile devices has been implemented and released in an open-source ubiquitous authentication toolkit (OpenUAT). We also present an initial user study evaluating four of these channels. ETPL MC-118 Adaptive Duty Cycle Control with Queue Management in Wireless Sensor Networks Abstract: This paper proposes a control-based approach to the duty cycle adaptation for wireless sensor networks. The proposed method controls the duty cycle through the queue management to achieve high- performance under variable traffic rates. To have energy efficiency while minimizing the delay, we design a feedback controller, which adapts the sleep time to the traffic change dynamically by constraining the queue length at a predetermined value. In addition, we propose an efficient synchronization scheme using an active pattern, which represents the active time slot schedule for synchronization among sensor nodes, without affecting neighboring schedules. Based on the control theory, we analyze the adaptation behavior of the proposed controller and demonstrate system stability. The simulation results show that the proposed method outperforms existing schemes by achieving more power savings while minimizing the delay. ETPL MC-118 Distributed MAC Protocol Supporting Physical-Layer Network Coding Abstract: Physical-layer network coding (PNC) is a promising approach for wireless networks. It allows nodes to transmit simultaneously. Due to the difficulties of scheduling simultaneous transmissions, existing works on PNC are based on simplified medium access control (MAC) protocols, which are not applicable to general multihop wireless networks, to the best of our knowledge. In this paper, we propose a distributed MAC protocol that supports PNC in multihop wireless networks. The proposed MAC protocol is based on the carrier sense multiple access (CSMA) strategy and can be regarded as an extension to the IEEE 802.11 MAC protocol. In the proposed protocol, each node collects information on the queue status of its neighboring nodes. When a node finds that there is an opportunity for some of its neighbors to perform PNC, it notifies its corresponding neighboring nodes and initiates the process of packet exchange using PNC, with the node itself as a relay. During the packet exchange process, the relay also works as a coordinator which coordinates the transmission of source nodes. Meanwhile, the proposed protocol is compatible with conventional network coding and conventional transmission schemes. Simulation results show that the proposed protocol is advantageous in various scenarios of wireless applications.
  • Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli, ETPL MC-118 Distributed Cooperation and Diversity for Hybrid Wireless Networks Abstract: In this paper, we propose a new Distributed Cooperation and Diversity Combining framework. Our focus is on heterogeneous networks with devices equipped with two types of radio frequency (RF) interfaces: short-range high-rate interface (e.g., IEEE802.11), and a long-range low-rate interface (e.g., cellular) communicating over urban Rayleigh fading channels. Within this framework, we propose and evaluate a set of distributed cooperation techniques operating at different hierarchical levels with resource constraints such as short-range RF bandwidth. We propose a Priority Maximum-Ratio Combining (PMRC) technique, and a Post Soft-Demodulation Combining (PSDC) technique. We show that the proposed techniques achieve significant improvements on Signal to Noise Ratio (SNR), Bit Error Rate (BER) and throughput through analysis, simulation, and experimentation on our software radio testbed. Our results also indicate that, under several communication scenarios, PMRC and PSDC can improve the throughput performance by over an order of magnitude.