IEEE Final Year Projects 2011-2012 :: Elysium Technologies Pvt Ltd::Mobilecomputingnew

Elysium Technologies Private Limited
ISO 9001:2008 A leading Research and Development Division
Madurai | Chennai | Trichy | Coimbatore | Kollam| Singapore
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Email: info@elysiumtechnologies.com

IEEE Final Year Project List 2011-2012

Abstract MOBILE COMPUTING 2011 - 2012

01 A Control-Theoretic Approach to Distributed Optimal Configuration of 802.11 WLANs

The optimal configuration of the contention parameters of a WLAN depends on the network conditions in terms of
number of stations and the traffic they generate. Following this observation, a considerable effort in the literature has
been devoted to the design of distributed algorithms that optimally configure the WLAN parameters based on current
conditions. In this paper, we propose a novel algorithm that, in contrast to previous proposals which are mostly
based on heuristics, is sustained by mathematical foundations from multivariable control theory. A key advantage of
the algorithm over existing approaches is that it is compliant with the 802.11 standard and can be implemented with
current wireless cards without introducing any changes into the hardware or firmware. We study the performance of
our proposal by means of theoretical analysis, simulations, and a real implementation. Results show that the
algorithm substantially outperforms previous approaches in terms of throughput and delay.

02 A Cooperative Clustering Protocol for Energy Saving of Mobile Devices with WLAN and Bluetooth Interfaces

One of the most widely used wireless communication standards is a Wireless Local Area Network (WLAN) (IEEE 802.11).
However, WLAN has a serious power consumption problem. In this paper, we propose a novel energy saving approach that
exploits the multiradio feature of recent mobile devices equipped with WLAN and Bluetooth interfaces. Unlike previous
approaches, our work is based on clustering. In our work, a cluster is a Bluetooth Personal Area Network (PAN), which
consists of one cluster head and several regular nodes. The cluster head acts as a gateway between the PAN and the
WLAN, enabling the regular nodes to access the WLAN infrastructure via low-power Bluetooth. We present a distributed
clustering protocol, Cooperative Networking protocol (CONET), which dynamically reforms clusters according to each
node’s bandwidth requirement, energy use, and application type. CONET does not require modifications of existing
wireless infrastructures because clustering is performed independently of WLAN access points. We implemented the
CONET prototype with four wearable computing devices to evaluate the performance on real hardware. We also simulated
CONET for large networks of more than 100 mobile nodes. Both results demonstrate that our approach is effective in
reducing the power consumption of WLAN.

03 A Distributed and Scalable Time Slot Allocation Protocol for Wireless Sensor Networks

There are performance deficiencies that hamper the deployment of Wireless Sensor Networks (WSNs) in critical
monitoring applications. Such applications are characterized by considerable network load generated as a result of
sensing some characteristics of the monitored system. Excessive packet collisions lead to packet losses and
retransmissions, resulting in significant overhead costs and latency. In order to address this issue, we introduce a
distributed and scalable scheduling access scheme that mitigates high data loss in data-intensive sensor networks
and can also handle some mobility. Our approach alleviates transmission collisions by employing virtual grids that

Madurai Trichy Kollam
Elysium Technologies Private Limited Elysium Technologies Private Limited Elysium Technologies Private Limited
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eMail: elysium.trichy@gmail.com

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adopt Latin Squares characteristics to time slot assignments. We show that our algorithm derives conflictfree time
slot allocation schedules without incurring global overhead in scheduling. Furthermore, we verify the effectiveness
of our protocol by simulation experiments. The results demonstrate that our technique can efficiently handle sensor
mobility with acceptable data loss, low packet delay, and low overhead.

04 A Medium Access Control Scheme for Wireless LANs with Constant-Time Contention

In today’s wireless networks, stations using the IEEE 802.11 Standard contend for the channel using the Distributed
Coordination Function (DCF). Research has shown that DCF’s performance degrades especially with the large number of
stations. This becomes more concerning due to the increasing proliferation of wireless devices. In this paper, we present a
Medium Access Control (MAC) scheme for wireless LANs and compare its performance to DCF and to other efficient
schemes. Our scheme, which attempts to resolve the contention in a constant number of slots (or constant time), is called
CONTI. The contention resolution happens over a predefined number of slots. In a slot, the stations probabilistically send a
jam signal on the channel. The stations listening retire if they hear a jam signal. The others continue to the next slot. Over
several slots, we aim to have one station remaining in the contention, which will then transmit its data. We find the optimal
parameters of CONTI and present an analysis on its performance. More comprehensive evaluation is presented in the
simulation results where we compare CONTI, DCF, and other efficient schemes from the literature. We consider the number
of slots used, the collision rate, the throughput, the delay, and the fairness. The highest throughput was achieved by
CONTI. Moreover, our results provide measurements from each of the schemes that we consider and provide the insight on
each scheme’s operation.

05 A Privacy-Preserving Location Monitoring System for Wireless Sensor Networks

Monitoring personal locations with a potentially untrusted server poses privacy threats to the monitored individuals.
To this end, we propose a privacy-preserving location monitoring system for wireless sensor networks. In our
system, we design two innetwork location anonymization algorithms, namely, resource and quality-aware algorithms,
that aim to enable the system to provide high-quality location monitoring services for system users, while preserving
personal location privacy. Both algorithms rely on the wellestablished k-anonymity privacy concept, that is, a person
is indistinguishable among k persons, to enable trusted sensor nodes to provide the aggregate location information
of monitored persons for our system. Each aggregate location is in a form of a monitored area A along with the
number of monitored persons residing in A, where A contains at least k persons. The resource-aware algorithm aims
to minimize communication and computational cost, while the quality-aware algorithm aims to maximize the
accuracy of the aggregate locations by minimizing their monitored areas. To utilize the aggregate location
information to provide location monitoring services, we use a spatial histogram approach that estimates the
distribution of the monitored persons based on the gathered aggregate location information. Then, the estimated
distribution is used to provide location monitoring services through answering range queries. We evaluate our
system through simulated experiments. The results show that our system provides high-quality location monitoring
services for system users and guarantees the location privacy of the monitored persons.


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06 A Spectrum Decision Framework for Cognitive Radio Networks

Cognitive radio networks have been proposed as a solution to both spectrum inefficiency and spectrum scarcity problems.
However, they face to a unique challenge based on the fluctuating nature of heterogeneous spectrum bands as well as the
diverse service requirements of various applications. In this paper, a spectrum decision framework is proposed to
determine a set of spectrum bands by considering the application requirements as well as the dynamic nature of spectrum
bands. To this end, first, each spectrum is characterized by jointly considering primary user activity and spectrum sensing
operations. Based on this, a minimum variancebased spectrum decision is proposed for real-time applications, which
minimizes the capacity variance of the decided spectrum bands subject to the capacity constraints. For best-effort
applications, a maximum capacity-based spectrum decision is proposed where spectrum bands are decided to maximize
the total network capacity. Moreover, a dynamic resource management scheme is developed to coordinate the spectrum
decision adaptively dependent on the time-varying cognitive radio network capacity. Simulation results show that the
proposed methods provide efficient bandwidth utilization while satisfying service requirements.

07 Adaptive Location-Oriented Content Delivery in Delay-Sensitive Pervasive Applications

In this paper, we introduce a delay-sensitive service that involves transmitting large amounts of location-based data
to nodes at multiple locations. Given a limited amount of access points (APs) and an abundance of service requests
that result from the nodes moving around, a typical content delivery service would inevitably introduce considerable
delay. To solve this problem, we analyze the movement pattern of mobile nodes and approximate it as a semi-Markov
process. Based on this model, we explore different components of the underlying service delay and propose that
APs should use a multicast strategy to minimize the queuing delay component. Furthermore, we demonstrate the
feasibility of employing nodes, which already have their own local copies of location-relevant data, to relay such data
to other nodes by employing one or multiple communication channels. Lastly, we examine the resulting algorithms
and study their performance relative to baseline content-delivery schemes through simulations.

08 An Improved Geocast for Mobile Ad Hoc Networks

Geographic addressing of packets within mobile ad hoc networks enables novel applications, including hard real-time
engagement simulation in military training systems, geographic command and control functions in training and emergency
communications, and commercial messaging applications as well. The most scalable implementation of geoaddressing is
via a geocast protocol, where nodes selectively retransmit packets based on local decision rules. Well-designed
retransmission heuristics yield scalable geographic flooding that outperforms alternative geoaddressing approaches.
However, previous geocast implementations, while effective, fall into two categories. Approaches based on flooding are
unscalable due to the high load they generate. Scalable approaches, on the other hand, have trouble in complex
environments, lacking sufficient intelligence about the necessary directionality of packet flow. The present paper defines a
novel geocast heuristic, the Center Distance with Priority (CD-P) Heuristic, which both significantly improves on reliability


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of existing scalable geocasts and yet also remains scalable as scenario complexity increases. This paper describes the new
technique as well as an evaluation study comparing it to previous approaches.

09 Analysis of Best Channel Feedback and Its Adaptive Algorithms for Multicarrier Wireless Data Systems

Multiuser diversity techniques are used in multicarrier data systems to enhance downlink cell throughput. This
requires downlink channel information from the users that is opportunistically used by a base station to send data to
the users with good channel condition. Channel feedback from the user to the base station incurs high overhead
especially when many users are in the cell and each user needs to report channel information over multiple
channels, as in OFDMA systems. To reduce the quantity of feedback information without significant throughput
degradation, a practical strategy is to deliver feedback on a partial set of channels with the best channel quality. We
call it best feedback, and this reporting scheme carried out for best four or five among 24 channels has been already
adopted in the IEEE 802.16e standard. Considering real feedback conditions, we investigate the performance of a
best feedback scheme and derive the optimal number of channels for which information needs to be fed back to keep
the throughput gap (compared to a full feedback scheme) within a target margin. From the optimal condition, we
propose an adaptive best feedback algorithm, where the number of reported channels is adjusted to adapt to the
number of users in the cell. We also propose an adjusted periodic feedback algorithm, where users are divided into
groups and scheduling is carried out group by group, so a user can report feedback information when his group is
scheduled, thereby reducing the frequency of feedback transmission. To support differentiated performance, we
further propose heterogeneous feedback algorithms where users are divided into heterogeneous groups, each with a
different group size or a different feedback period. Numerical results validate our analysis and provide meaningful
insights into the design of various channel feedback schemes.

10 Anticollision Protocols for Single-Reader RFID Systems: Temporal Analysis and Optimization

One of the major challenges in the use of Radio Frequency-based Identification (RFID) on a large scale is the ability to read
a large number of tags quickly. Central to solving this problem is resolving collisions that occur when multiple tags reply to
the query of a reader. To this purpose, several MAC protocols for passive RFID systems have been proposed. These
typically build on traditional MAC schemes, such as aloha and tree-based protocols. In this paper, we propose a new
performance metric by which to judge these anticollision protocols: time system efficiency. This metric provides a direct
measure of the time taken to read a group of tags. We then evaluate a set of well-known RFID MAC protocols in light of this
metric. Based on the insights gained, we propose a new anticollision protocol, and show that it significantly outperforms
previously proposed mechanisms.

11 Autonomous Deployment of Heterogeneous Mobile Sensors

In this paper, we address the problem of deploying heterogeneous mobile sensors over a target area. Traditional
approaches to mobile sensor deployment are specifically designed for homogeneous networks. Nevertheless,
network and device homogeneity is an unrealistic assumption in most practical scenarios, and previous approaches
fail when adopted in heterogeneous operative settings. For this reason, we introduce VorLag, a generalization of the
Voronoi-based approach which exploits the Laguerre geometry. We theoretically prove the appropriateness of our


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proposal to the management of heterogeneous networks. In addition, we demonstrate that VorLag can be extended
to deal with dynamically generated events or uneven energy depletion due to communications. Finally, by means of
simulations, we show that VorLag provides a very stable sensor behavior, with fast and guaranteed termination and
moderate energy consumption. We also show that VorLag performs better than its traditional counterpart and other
methods based on virtual forces.

12 Breath: An Adaptive Protocol for Industrial Control Applications Using Wireless Sensor Networks

An energy-efficient, reliable and timely data transmission is essential for Wireless Sensor Networks (WSNs) employed in
scenarios where plant information must be available for control applications. To reach a maximum efficiency, cross-layer
interaction is a major design paradigm to exploit the complex interaction among the layers of the protocol stack. This is
challenging because latency, reliability, and energy are at odds, and resource-constrained nodes support only simple
algorithms. In this paper, the novel protocol Breath is proposed for control applications. Breath is designed for WSNs
where nodes attached to plants must transmit information via multihop routing to a sink. Breath ensures a desired packet
delivery and delay probabilities while minimizing the energy consumption of the network. The protocol is based on
randomized routing, medium access control, and duty-cycling jointly optimized for energy efficiency. The design approach
relies on a constrained optimization problem, whereby the objective function is the energy consumption and the
constraints are the packet reliability and delay. The challenging part is the modeling of the interactions among the layers by
simple expressions of adequate accuracy, which are then used for the optimization by in-network processing. The optimal
working point of the protocol is achieved by a simple algorithm, which adapts to traffic variations and channel conditions
with negligible overhead. The protocol has been implemented and experimentally evaluated on a testbed with off-the-shelf
wireless sensor nodes, and it has been compared with a standard IEEE 802.15.4 solution. Analytical and experimental
results show that Breath is tunable and meets reliability and delay requirements. Breath exhibits a good distribution of the
working load, thus ensuring a long lifetime of the network. Therefore, Breath is a good candidate for efficient, reliable, and
timely data gathering for control applications.

13 Channel-Aware Routing in MANETs with Route Handoff

In wireless mobile ad hoc networks (MANETs), packet transmission is impaired by radio link fluctuations. This paper
proposes a novel channel adaptive routing protocol which extends the Ad hoc On-Demand Multipath Distance Vector
(AOMDV) routing protocol to accommodate channel fading. Specifically, the proposed Channel-Aware AOMDV (CA-
AOMDV) uses the channel average nonfading duration as a routing metric to select stable links for path discovery,
and applies a preemptive handoff strategy to maintain reliable connections by exploiting channel state information.
Using the same information, paths can be reused when they become available again, rather than being discarded. We
provide new theoretical results for the downtime and lifetime of a live-die-live multiple path system, as well as
detailed theoretical expressions for common network performance measures, providing useful insights into the
differences in performance between CA-AOMDV and AOMDV. Simulation and theoretical results show that CA-
AOMDV has greatly improved network performance over AOMDV.

14 Cognitive Medium Access: Exploration, Exploitation, and Competition


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This paper considers the design of efficient strategies that allow cognitive users to choose frequency bands to sense and
access among multiple bands with unknown parameters. First, the scenario in which a single cognitive user wishes to
opportunistically exploit the availability of frequency bands is considered. By adopting tools from the classical bandit
problem, optimal as well as low complexity asymptotically optimal solutions are developed. Next, the multiple cognitive
user scenario is considered. The situation in which the availability probability of each channel is known is first considered.
An optimal symmetric strategy that maximizes the total throughput of the cognitive users is developed. To avoid the
possible selfish behavior of the cognitive users, a game-theoretic model is then developed. The performance of both
models is characterized analytically. Then, the situation in which the availability probability of each channel is unknown a
priori is considered. Low-complexity medium access protocols, which strike an optimal balance between exploration and
exploitation in such competitive environments, are developed. The operating points of these low-complexity protocols are
shown to converge to those of the scenario in which the availability probabilities are known. Finally, numerical results are
provided to illustrate the impact of sensing errors and other practical considerations.

15 Compatibility between Three Well-Known Broadcast Tree Construction Algorithms and Various Metrics

Broadcast routing is a critical component in the routing design. While there are plenty of routing metrics and
broadcast routing schemes in current literature, it remains an unsolved problem as to which metrics are compatible
with a specific broadcast routing scheme. In particular, in the wireless broadcast routing context where transmission
has an inherent broadcast property, there is a potential danger of incompatible combination of broadcast routing
algorithms and metrics. This paper shows that different broadcast routing algorithms have different requirements on
the properties of broadcast routing metrics. The metric properties for broadcast routing algorithms in both
undirected network topologies and directed network topologies are developed and proved. They are successfully
used to verify the compatibility between broadcast routing metrics and broadcast routing algorithms.

16 Context-Based Network Estimation for Energy-Efficient Ubiquitous Wireless Connectivity

Context information brings new opportunities for efficient and effective system resource management of mobile devices. In
this work, we focus on the use of context information to achieve energy-efficient, ubiquitous wireless connectivity. Our
field-collected data show that the energy cost of network interfaces poses a great challenge to ubiquitous connectivity,
despite decent availability of cellular networks. We propose to leverage the complementary strengths of Wi-Fi and cellular
interfaces by automatically selecting the most efficient one based on context information. We formulate the selection of
wireless interfaces as a statistical decision problem. The challenge is to accurately estimate Wi-Fi network conditions
without powering up the network interface. We explore the use of different context information, including time, history,
cellular network conditions, and device motion, to statistically estimate Wi-Fi network conditions with negligible overhead.
We evaluate several context-based algorithms for the estimation and prediction of current and future network conditions.
Simulations using field-collected traces show that our network estimation algorithms can improve the average battery
lifetime of a commercial mobile phone for an ECG reporting application by 40 percent, very close to the estimated
theoretical upper bound of 42 percent. Furthermore, our most effective algorithm can predict Wi-Fi availability for one and
ten hours into the future with 95 and 90 percent accuracy, respectively.


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17 Cross-Layer Optimization for Multimedia Transport over Multicode CDMA Networks

Most previous work on code division multiple access (CDMA) considers the bit error ratio (BER) at the physical layer
and the frame drop ratio (FDR) at the medium access control layer separately. However, a better system
performance, e.g., in terms of a lower overall frame loss ratio (FLR), can be achieved if BER and FDR are jointly
optimized. In this paper, we propose a cross-layer optimization scheme called traffic-adaptive scheme for multicode
CDMA operating over a time division multiple access (TDMA) channel. Based on the traffic condition and buffer
status, this scheme employs a Markov Decision Process (MDP) to determine the optimal value of the maximum
number of simultaneous data frames that can be transmitted in each time slot of a TDMA frame so as to minimize the
overall FLR of the system. To facilitate implementation, we also propose an approximation scheme named the
rateadaptive scheme to reduce the computation cost. Simulation and analytical results show that both the traffic-
adaptive scheme and rate-adaptive scheme can significantly reduce FLR, increase the system throughput, and
optimize the packet access delay of the system. Furthermore, the rate-adaptive scheme can achieve a performance
close to the traffic-adaptive scheme when the traffic load in the system is high.

18 Data Delivery Properties of Human Contact Networks

Pocket Switched Networks take advantage of social contacts to opportunistically create data paths over time. This work
employs empirical traces to examine the effect of the human contact process on data delivery in such networks. The
contact occurrence distribution is found to be highly uneven: contacts between a few node pairs occur too frequently,
leading to inadequate mixing in the network, while the majority of contacts occur rarely, but are essential for global
connectivity. This distribution of contacts leads to a significant variation in the fraction of node pairs that can be connected
over time windows of similar duration. Good time windows tend to have a large clique of nodes that can all reach each
other. It is shown that the clustering coefficient of the contact graph over a time window is a good predictor of achievable
connectivity. We then examine all successful paths found by flooding and show that though delivery times vary widely,
randomly sampling a small number of paths between each source and destination is sufficient to yield a delivery time
distribution close to that of flooding over all paths. This result suggests that the rate at which the network can deliver data
is remarkably robust to path failures.

19 Design and Performance Analysis of Mobility Management Schemes Based on Pointer Forwarding for Wireless Mesh Networks

We propose efficient mobility management schemes based on pointer forwarding for wireless mesh networks
(WMNs) with the objective to reduce the overall network traffic incurred by mobility management and packet delivery.
The proposed schemes are per-user-based, i.e., the optimal threshold of the forwarding chain length that minimizes
the overall network traffic is dynamically determined for each individual mobile user, based on the user’s specific
mobility and service patterns. We develop analytical models based on stochastic Petri nets to evaluate the
performance of the proposed schemes. We demonstrate that there exists an optimal threshold of the forwarding
chain length, given a set of parameters characterizing the specific mobility and service patterns of a mobile user. We
also demonstrate that our schemes yield significantly better performance than schemes that apply a static threshold
to all mobile users. A comparative analysis shows that our pointer forwarding schemes outperform routing-based


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mobility management protocols for WMNs, especially for mobile Internet applications characterized by large traffic
asymmetry for which the downlink packet arrival rate is much higher than the uplink packet arrival rate.

20 Design and Performance of an Optimal Inertial Power Harvester for Human-Powered Devices

We present an empirical study of the long-term practicality of using human motion to generate operating power for
bodymounted consumer electronics and health sensors. We have collected a large continuous acceleration data set from
eight experimental subjects going about their normal daily routine for three days each. Each subject is instrumented with a
data collection apparatus that simultaneously logs 3-axis, 80 Hz acceleration data from six body locations. We use this data
set to optimize a firstprinciples physical model of the commonly used velocity damped resonant generator (VDRG) by
selecting physical parameters such as resonant frequency and damping coefficient to maximize the harvested power. Our
results show that with reasonable assumptions on size, mass, placement, and efficiency of VDRG harvesters, most body-
mounted wireless sensors and even some consumer electronics devices can be powered continuously and indefinitely
from everyday motion. We have optimized the power harvesters for each individual and for each body location. In addition,
we present the potential of designing a damping- and frequency-tunable power harvester that could mitigate the power
reduction of a generator generalized for “average” subjects. We present the full details on the collection of the acceleration
data sets, the development of the VDRG model, and a numerical simulator, and discuss some of the future challenges that
remain in this promising field of research.

21 Discriminant Minimization Search for Large-Scale RF-Based Localization Systems

In large-scale fingerprinting localization systems, fine-grained location estimation and quick location determination
are conflicting concerns. To achieve finer grained localization, we have to collect signal patterns at a larger number
of training locations. However, this will incur higher computation cost during the pattern-matching process. In this
paper, we propose a novel discriminant minimization search (DMS)-based localization methodology. Continuous and
differentiable discriminant functions are designed to extract the spatial correlation of signal patterns at training
locations. The advantages of the DMS-based methodology are threefold. First, with through slope of discriminant
functions, the exhaustive pattern-matching process can be replaced by an optimization search process, which could
be done by a few quick jumps. Second, the continuity of the discriminant functions helps predict signal patterns at
untrained locations so as to achieve finer grained localization. Third, the large amount of training data can be
compressed into some functions that can be represented by a few parameters. Therefore, the storage space required
for localization can be significantly reduced. To realize this methodology, two algorithms, namely, Newton-PL and
Newton-INT, are designed based on the concept of gradient descent search. Simulation and experiment studies show
that our algorithms do provide finer grained localization and incur less computation cost.


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22 Distributed Fault-Tolerant Quality of Wireless Networks

A mobile ad hoc network (MANET) consists of a group of communicating hosts that form an arbitrary network topology by
means of any of several wireless communication media. MANET communications represent a diversification in
communication technology necessary to solve the stringent end-to-end requirements of QoS-based communication
networks. Of the many challenges in this complex distributed system, the problem of routing based on a predefined set of
customer preferences, critical to guaranteeing quality-of-service, is the focus of this research. Specifically, this paper
modifies a cluster-based QoS routing algorithm for mobile ad hoc networks with the aim of providing fault tolerance, which
is a critical feature in providing QoS in the link failure-prone environment of mobile networks. Performance of this new
fault-tolerant cluster-based QoS wireless algorithm is evaluated according to failure recovery time, dropped packets,
throughput, and sustained flow bandwidth via simulations involving node failure scenarios along QoS paths.

23 Distributed Multi-Interface Multichannel Random Access Using Convex Optimization

The aggregate capacity of wireless ad hoc networks can be increased substantially if each node is equipped with
multiple network interface cards (NICs) and each NIC operates on a distinct frequency channel. Most of the recently
proposed channel assignment algorithms are based on combinatorial techniques. Combinatorial channel assignment
schemes may sometimes result in computationally complicated algorithms as well as inefficient utilization of the
available frequency spectrum. In this paper, we analytically model channel and interface assignment problems as
tractable continuous optimization problems within the framework of network utility maximization (NUM). In particular,
the link data rate models for both single-channel reception and multichannel reception scenarios are derived. The
assignment of both nonoverlapped and partially overlapped channels is also considered. We then propose two
distributed multi-interface multichannel random access (DMMRA) algorithms for single-channel reception and
multichannel reception scenarios. The DMMRA algorithms are fast, distributed, and easy to implement. Each
algorithm solves the formulated NUM problem for each scenario. DMMRA requires each node to only iteratively solve
a local, myopic, and convex optimization problem. Convergence and optimality properties of our algorithms are
studied analytically. Simulation results show that our proposed algorithms significantly outperform utility-optimal
combinatorial channel assignment algorithms in terms of both achieved network utility and throughput.

24 Dynamic Conflict-Free Transmission Scheduling for Sensor Network Queries

With the emergence of high data rate sensor network applications, there is an increasing demand for high-performance
query services. To meet this challenge, we propose Dynamic Conflict-free Query Scheduling (DCQS), a novel scheduling
technique for queries in wireless sensor networks. In contrast to earlier TDMA protocols designed for general-purpose
workloads, DCQS is specifically designed for query services in wireless sensor networks. DCQS has several unique
features. First, it optimizes the query performance through conflict-free transmission scheduling based on the temporal
properties of queries in wireless sensor networks. Second, it can adapt to workload changes without explicitly
reconstructing the transmission schedule. Furthermore, DCQS also provides predictable performance in terms of the
maximum achievable query rate. We provide an analytical capacity bound for DCQS that enables DCQS to handle overload


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through rate control. NS2 simulations demonstrate that DCQS significantly outperforms a representative TDMA protocol
(DRAND) and 802.11b in terms of query latency and throughput.

25 Dynamic Time Slot Partitioning for Multimedia Transmission in Two-Hop Cellular Networks

In recent years, there has been an exponential increase in the number of mobile phone users. In addition, a
significant growth in the demand for high-rate multimedia services over wireless networks, such as video
conferencing, multimedia streaming, etc., was noted. Different solutions were proposed to support high-quality high
data rate delivery to mobile users, including resource allocation techniques for packet-radio-based next generation
cellular networks. In this paper, an efficient time slot allocation method—Dynamic Time Slot Partitioning (DTSP)
algorithm based on statistical multiplexing is proposed for a two-hop cellular architecture. In DTSP, the available
bandwidth resources are increased by partitioning each time slot into several minislots wherein different numbers of
minislots are allocated to different users. The DTSP algorithm is based on asynchronous time-division multiplexing,
wherein users with variable number of packets in their buffers can transmit data sequentially without any loss in the
overall available resources. The key advantage of DTSP is that it can flexibly adapt to different quality of service
requirements, especially when combined with adaptive modulation. It has been observed that the system capacity
achieved by the DTSP algorithm in the downlink mode using adaptive modulation is up to 41 percent higher than
when existing solutions are employed. In addition, DTSP results in significantly lower time for data transmission than
the state-of-the-art region and time partitioning techniques.

26 Effective Scheduling in Infrastructure-Based Cognitive Radio Networks

In this paper, we investigate a joint scheduling and power control for an infrastructure-based cognitive radio network (CRN)
in coexistence with a cellular primary radio network (PRN). The PRN uses a set of licensed nonoverlapping orthogonal
frequency channels for transmission. This set of channels is also accessed in an opportunistic manner by a set of cognitive
radio base stations (CR-BSs) to support secondary users (SUs). The problem is formulated to maximize the spectrum
utilization of SUs without causing excessive interference to active primary users (PUs) of the PRN. In addition, all the
serviced SUs must meet a certain Quality of Service (QoS), such as satisfying a predefined signal to interference noise ratio
(SINR). A centralized solution for joint scheduling and power control is derived to make the global accessing decision for all
unserved SUs. With the assumption that the knowledge of all subscribers is available, a coordinator of the CRN can use the
joint scheduling and power control algorithm to maximize the spectrum utilization of serviced SUs by solving a mixed-
integer linear programming (MILP) with an NP-hard complexity. To avoid the NP-hard complexity, we propose a suboptimal
heuristic greedy algorithm that can be obtained at a much lower complexity based on the coloring interference graph
among unserved SUs effected by serviced SUs and active PUs. Its superior performance over the existing algorithms is
demonstrated through simulations.

27 Efficient Data Collection in Wireless Sensor Networks with Path-Constrained Mobile Sinks

Recent work has shown that sink mobility along a constrained path can improve the energy efficiency in wireless
sensor networks. However, due to the path constraint, a mobile sink with constant speed has limited communication
time to collect data from the sensor nodes deployed randomly. This poses significant challenges in jointly improving


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the amount of data collected and reducing the energy consumption. To address this issue, we propose a novel data
collection scheme, called the Maximum Amount Shortest Path (MASP), that increases network throughput as well as
conserves energy by optimizing the assignment of sensor nodes. MASP is formulated as an integer linear
programming problem and then solved with the help of a genetic algorithm. A two-phase communication protocol
based on zone partition is designed to implement the MASP scheme. We also develop a practical distributed
approximate algorithm to solve the MASP problem. In addition, the impact of different overlapping time partition
methods is studied. The proposed algorithms and protocols are validated through simulation experiments using
OMNET++.

28 Efficient Location Training Protocols for Heterogeneous Sensor and Actor Networks

In this work, we consider a large-scale geographic area populated by tiny sensors and some more powerful devices called
actors, authorized to organize the sensors in their vicinity into short-lived, actor-centric sensor networks. The tiny sensors
run on miniature nonrechargeable batteries, are anonymous, and are unaware of their location. The sensors differ in their
ability to dynamically alter their sleep times. Indeed, the periodic sensors have sleep periods of predefined lengths,
established at fabrication time; by contrast, the free sensors can dynamically alter their sleep periods, under program
control. The main contribution of this work is to propose an energy-efficient location training protocol for heterogeneous
actor-centric sensor networks where the sensors acquire coarse-grain location awareness with respect to the actor in their
vicinity. Our theoretical analysis, confirmed by experimental evaluation, shows that the proposed protocol outperforms the
best previously known location training protocols in terms of the number of sleep/awake transitions, overall sensor awake
time, and energy consumption.

29 Endpoint-Based Call Admission Control and Resource Management for VoWLAN

This paper examines two specific aspects of resource management in Wireless Local Area Networks (WLANs)—Call
Admission Control (CAC) and handling of Link Adaptation (LA) events. A self-consistent system to manage these for
Voice over Internet Protocol (VoIP) over an IEEE 802.11 WLAN is presented. The proposed CAC scheme is based on
the Endpoint Admission Control (EAC) paradigm, where the endpoints probe the network to determine if the call can
be supported with acceptable Quality of Service (QoS). The proposed scheme was evaluated on an experimental
testbed and test results show that correct admission decisions were made under various network configurations.
The scheme also determines if LA has resulted in the system becoming congested and, if so, the voice codec of the
handset which has undergone LA is adapted so as to restore the system to its earlier state, thereby alleviating the
congestion. The proposed scheme was evaluated on the experimental testbed and test results show that the codec
adaptation scheme was very effective at overcoming the effects of LA for VoIP over WLAN.


11



30 Expected Routing Overhead for Location Service in MANETs under Flat Geographic Routing

In this work, we consider a large-scale geographic area populated by tiny sensors and some more powerful devices called
actors, authorized to organize the sensors in their vicinity into short-lived, actor-centric sensor networks. The tiny sensors
run on miniature nonrechargeable batteries, are anonymous, and are unaware of their location. The sensors differ in their
ability to dynamically alter their sleep times. Indeed, the periodic sensors have sleep periods of predefined lengths,
established at fabrication time; by contrast, the free sensors can dynamically alter their sleep periods, under program
control. The main contribution of this work is to propose an energy-efficient location training protocol for heterogeneous
actor-centric sensor networks where the sensors acquire coarse-grain location awareness with respect to the actor in their
vicinity. Our theoretical analysis, confirmed by experimental evaluation, shows that the proposed protocol outperforms the
best previously known location training protocols in terms of the number of sleep/awake transitions, overall sensor awake
time, and energy consumption.

31 Explicit Congestion Control Algorithms for Time Varying Capacity Media

Explicit congestion control (XCC) is emerging as one potential solution for overcoming limitations inherent to the
current TCP algorithm, characterized by unstable throughput, high queuing delay, RTT-limited fairness, and a static
dynamic range that does not scale well to high bandwidth delay product networks. In XCC, routers provide multibit
feedback to sources, which, in turn, adapt throughput more accurately to the path bandwidth with potentially faster
convergence times. Such systems, however, require precise knowledge of link capacity for efficient operation. In the
presence of variable-capacity media, e.g., 802.11, such information is not entirely obvious or may be difficult to
extract. We explore three possible algorithms for XCC which retain efficiency under such conditions by inferring
available bandwidth from queue dynamics and test them through simulations with two relevant XCC protocols: XCP
and RCP. Additionally, preliminary results from an experimental implementation based on XCP are presented. Finally,
we compare our proposals with TCP and show how such algorithms outperform it in terms of efficiency, stability,
queuing delay, and flowrate fairness.

32 Fast Detection of Mobile Replica Node Attacks in Wireless Sensor Networks Using Sequential Hypothesis Testing Jun- Won

Due to the unattended nature of wireless sensor networks, an adversary can capture and compromise sensor nodes, make
replicas of them, and then mount a variety of attacks with these replicas. These replica node attacks are dangerous
because they allow the attacker to leverage the compromise of a few nodes to exert control over much of the network.
Several replica node detection schemes have been proposed in the literature to defend against such attacks in static
sensor networks. However, these schemes rely on fixed sensor locations and hence do not work in mobile sensor
networks, where sensors are expected to move. In this work, we propose a fast and effective mobile replica node detection
scheme using the Sequential Probability Ratio Test. To the best of our knowledge, this is the first work to tackle the
problem of replica node attacks in mobile sensor networks. We show analytically and through simulation experiments that
our scheme detects mobile replicas in an efficient and robust manner at the cost of reasonable overheads.


12



33 Flexible Broadcasting of Scalable Video Streams to Heterogeneous Mobile Devices

We study the scalable video broadcasting problem in mobile TV broadcast networks, where each TV channel is
encoded into a scalable video stream with multiple layers, and several TV channels are concurrently broadcast over
a shared air medium to many mobile devices with heterogeneous resources. Our goal is to encapsulate and
broadcast video streams encoded in scalable manner to enable heterogeneous mobile devices to render the most
appropriate video substreams while achieving high energy saving and low channel switching delay. The appropriate
streams depend on the device capability and the target energy consumption level. We propose two new broadcast
schemes, which are flexible in the sense that they allow diverse bit rates among layers of the same stream. Such
flexibility enables videos to be optimally encoded in terms of coding efficiency, and allows the coded video streams
to be better matched with the capability of mobile devices. We analyze the performance of the proposed broadcast
schemes. In addition, we have implemented the proposed schemes in a real mobile TV testbed to show their
practicality and efficiency. Our extensive experiments confirm that the proposed schemes enable energy saving
differentiation: between 75 and 95 percent were observed. Moreover, one of the schemes achieves low channel
switching delays: 200 msec is possible with typical system parameters.

34 Integration Gain of Heterogeneous WiFi/WiMAX Networks

We study the integrated WiFi/WiMAX networks, where users are equipped with dual-radio interfaces that can connect to
either a WiFi or a WiMAX network. Previous research on integrated heterogeneous networks (e.g., WiFi/cellular) usually
considers one network as the main and the other as the auxiliary. The performance of the integrated network is compared
with the “main” network. The gain is apparently due to the additional resources from the auxiliary network. In this study, we
are interested in integration gain that comes from the better utilization of the resource rather than the increase of the
resource. The heterogeneity of the two networks is the fundamental reason for the integration gain. To quantify it, we
design a generic framework that supports different performance objectives. We focus on the max-min throughput fairness
in this work and also briefly cover the proportional fairness metric. We first prove that it is NP-hard to achieve integral max-
min throughput fairness, then propose a heuristic algorithm, which provides twoapproximation to the optimal fractional
solution. Simulation results demonstrate significant integration gain from three sources, namely, spatial multiplexing,
multinetwork diversity, and multiuser diversity. For the proportional fairness metric, we derive the formulation and propose
a heuristic algorithm, which shows satisfactory performance when compared with the optimal solution.

35 Interference-Aware Routing in Wireless Multihop Networks

Interference is an inherent characteristic of wireless (multihop) communications. Adding interference-awareness to
important control functions, e.g., routing, could significantly enhance the overall network performance. Despite some
initial efforts, it is not yet clearly understood how to best capture the effects of interference in routing protocol
design. Most existing proposals aim at inferring its effect by actively probing the link. However, active probe
measurements impose an overhead and may often misrepresent the link quality due to their interaction with other
networking functions. Therefore, in this paper we follow a different approach and: 1) propose a simple yet accurate
analytical model for the effect of interference on data reception probability, based only on passive measurements


13



and information locally available at the node; 2) use this model to design an efficient interference-aware routing
protocol that performs as well as probing-based protocols, yet avoids all pitfalls related to active probe
measurements. To validate our proposal, we have performed experiments in a real testbed, setup in our indoor office
environment. We show that the analytical predictions of our interference model exhibit good match with both
experimental results as well as more complicated analytical models proposed in related literature. Furthermore, we
demonstrate that a simple probeless routing protocol based on our model performs at least as good as well-known
probe-based routing protocols in a large set of experiments including both intraflow and interflow.

36 Localization of Mobile Nodes in Wireless Networks with Correlated in Time Measurement Noise

Wireless sensor networks are an inherent part of decision making, object tracking, and location awareness systems. This
work is focused on simultaneous localization of mobile nodes based on received signal strength indicators (RSSIs) with
correlated in time measurement noises. Two approaches to deal with the correlated measurement noises are proposed in
the framework of auxiliary particle filtering: with a noise augmented state vector and the second approach implements
noise decorrelation. The performance of the two proposed multimodel auxiliary particle filters (MM AUX-PFs) is validated
over simulated and real RSSIs and high localization accuracy is demonstrated.

37 MAC Layer Throughput Estimation in Impulse-Radio UWB Networks

The inherent channel characteristics of impulse-based UWB networks affect the MAC layer performance significantly.
Most previous studies on evaluating MAC protocols are based on prolonged simulations and do not account for the
multiple access interference due to multipath delay spread. In this work, we develop CTU, an analytical framework for
Capturing the Throughput dependencies in UWB networks, while taking into account the PHY layer effects. The key
attributes of CTU are: 1) It is modular; it can be easily modified to provide a basis for evaluating a wide range of MAC
protocols for impulse-based UWB networks. The only requirements are that the MAC protocol under study be based
on time-hopping and the modulation scheme be pulse position modulation; these are common design decisions in
UWB networks. 2) It considers the channel characteristics in addition to MAC layer effects; CTU correlates
probabilistically the multipath delay profile of the channel with the packet error rate. We employ CTU to evaluate the
performance of different generic medium access procedure. We compare the results with those from extensive
simulations and show the high accuracy of CTU. We use CTU to assess the impact of various system parameters on
the MAC layer performance; we make several interesting observations that are discussed in depth.

38 MAP: Multiauctioneer Progressive Auction for Dynamic Spectrum Access

Cognitive radio (CR) is a promising paradigm to achieve efficient utilization of the limited spectrum resource by allowing
the unlicensed users to access the licensed spectrum, and dynamic spectrum access (DSA) is one of the fundamental
functions of CR networks. Market-driven spectrum auction has been recognized as an effective way to achieve DSA. In
spectrum auction, the primary spectrum owners (POs) act as auctioneers who are willing to sell idle spectrum bands for
additional revenue, and the secondary users (SUs) act as bidders who are willing to buy spectrum bands from POs for their
services. However, conventional spectrum auction designs are restricted within the scenario of single auctioneer. In this


14



paper, we study the spectrum auction with multiple auctioneers and multiple bidders, which is more realistic for practical
CR networks. We propose MAP, a Multiauctioneer Progressive auction mechanism, in which each auctioneer systematically
raises the trading price and each bidder subsequently chooses one auctioneer for bidding. The equilibrium is defined as
the state that no auctioneer and bidder would like to change his decision. We show analytically that MAP converges to the
equilibrium with maximum spectrum utilization of the whole system. We further analyze the incentive for POs and SUs
joining the auction and accepting the auction result. Simulation results show that MAP well converges to the equilibrium,
and the spectrum utilization is arbitrary closed to the global optimal solution according to the length of step.

39 Minimum Bandwidth Reservations for Periodic Streams in Wireless Real-Time Systems

Reservation-based (as opposed to contention-based) channel access in WLANs provides predictable and
deterministic transmission and is therefore able to provide timeliness guarantees for wireless and embedded real-
time applications. Also, reservation-based channel access is energy-efficient since a wireless adaptor is powered on
only during its exclusive channel access times. While scheduling for Quality of Service at the central authority (e.g.,
base station) has received extensive attention, the problem of determining the actual resource requirements of an
individual node in a wireless real-time system has been largely ignored. This work aims at finding the minimum
channel bandwidth reservation that meets the real-time constraints of all periodic streams of a given node. Keeping
the bandwidth reservation of a node to a minimum leads to reduced energy and resource requirements and leaves
more bandwidth for future reservations by other nodes. To obtain a solution to the minimum bandwidth reservation
problem, we transform it to a generic uniprocessor task schedulability problem, which is then addressed using a
generic algorithm. This algorithm works for a subclass of priority-driven packet scheduling policies, including three
common ones: fixed-priority, EDF, and FIFO. Moreover, we then specialize the generic algorithm to these three
policies according to their specific characteristics. Their computation complexities and bandwidth reservation
efficiencies are evaluated and guidelines for choosing scheduling policies and stream parameters are presented.

40 Mobile Sampling of Sensor Field Data Using Controlled Broadcast

Mobile objects can be used to gather samples from a sensor field. Civilian vehicles or even human beings equipped with
proper wireless communication devices can be used as mobile sinks that retrieve sensor-data from sampling points within
a large sensor field. A key challenge is how to gather the sensor data in a manner that is energy efficient with respect to the
sensor nodes that serve as sources of the sensor data. In this paper, an algorithmic technique called Band-based
Directional Broadcast is introduced to control the direction of broadcasts that originate from sensor nodes. The goal is to
direct each broadcast of sensor data toward the mobile sink, thus reducing costly forwarding of sensor data packets. The
technique is studied by simulations that consider energy consumption and data deliverability.

41 Mobility Tracking Based on Autoregressive Models

We propose an integrated scheme for tracking the mobility of a user based on autoregressive models that accurately
capture the characteristics of realistic user movements in wireless networks. The mobility parameters are obtained
from training data by computing Minimum Mean Squared Error (MMSE) estimates. Estimation of the mobility state,
which incorporates the position, velocity, and acceleration of the mobile station, is accomplished via an extended


15



Kalman filter using signal measurements from the wireless network. By combining mobility parameter and state
estimation in an integrated framework, we obtain an efficient and accurate real-time mobility tracking scheme that
can be applied in a variety of wireless networking applications. We consider two variants of an autoregressive
mobility model in our study and validate the proposed mobility tracking scheme using mobile trajectories collected
from drive test data. Our simulation results validate the accuracy of the proposed tracking scheme even when only a
small number of data samples is available for initial training.

42 Modeling and Improving TCP Performance over Cellular Link with Variable Bandwidth

To facilitate a viable evolution of cellular networks toward extensive packet data traffic, the High Speed Downlink Packet
Access (HSDPA) technology is introduced. The various link adaptation techniques employed by HSDPA augment the
bandwidth variation, which is identified as one of the most important factors resulting in the deterioration of TCP
performance. In this paper, we firstly build an analytical model of TCP throughput to explain why the bandwidth variation
degrades the TCP performance. Subsequently, a split-connection Window Adaptation TCP Proxy is proposed to improve
the TCP throughput in HSDPA networks. To use the precious cellular link resources sufficiently, the length of the queue in
Node-B is intentionally kept around the reference value through adaptively adjusting the sending window size of TCP proxy
based on the dynamic values of varying bandwidth. Since both the disturbance caused by bandwidth variation and the
feedback delay are prone to lead an unstable queue system, the robust sliding mode variable structure control theory is
employed to design the proper control law to weaken the impact of noise and delay on the stability of the queue system in
Node-B. The theoretical analysis and the enhanced scheme are verified through simulation experiments. The simulation
results show that our TCP proxy is able to resist against bandwidth oscillation and improve the cellular link utilization.

43 Multicast Throughput for Hybrid Wireless Networks under Gaussian Channel Model

We study the multicast capacity for hybrid wireless networks consisting of ordinary ad hoc nodes and base stations
under Gaussian Channel model, which generalizes both the unicast and broadcast capacities for hybrid wireless
networks. Assume that all ordinary ad hoc nodes transmit at a constant power P, and the power decays along the
path, with attenuation exponent alpha > 2. The data rate of a transmission is determined by the Signal to Interference
plus Noise Ratio (SINR) at the receiver as Blog(1+ SINR). The ordinary ad hoc nodes are placed in the square region
AðaÞ of area a according to a Poisson point process of intensity n=a. Then, m additional base stations (BSs) acting
as the relaying communication gateways are placed regularly in the region AðaÞ, and are connected by a high-
bandwidth wired network. Let a ¼ n and a ¼ 1, we construct the hybrid extended network (HEN) and hybrid dense
network (HDN), respectively. We choose randomly and independently ns ordinary ad hoc nodes to be the sources of
multicast sessions. We assume that each multicast session has nd randomly chosen terminals. Three broad
categories of multicast strategies are proposed. The first one is the hybrid strategy, i.e., the multihop scheme with
BS-supported, which further consists of two types of strategies called connectivity strategy and percolation strategy,
respectively. The second one is the ordinary ad hoc strategy, i.e., the multihop scheme without any BS-supported.
The third one is the classical BS-based strategy under which any communication between two ordinary ad hoc nodes
is relayed by some specific BSs. According to the different scenarios in terms of m, n, and nd, we select the optimal
scheme from the three categories of strategies, and derive the achievable multicast throughput based on the optimal
decision.


16



44 OFDM-Based Common Control Channel Design for Cognitive Radio Ad Hoc Networks

Cognitive radio (CR) technology allows devices to opportunistically use the vacant portions of the licensed wireless
spectrum. However, the available spectrum changes dynamically with the primary user (PU) activity, necessitating frequent
PU sensing coordination and exchanging network topology information in a multihop CR ad hoc network. To facilitate these
tasks, an always-on, out-of-band common control channel (CCC) design is proposed that uses noncontiguous OFDM
subcarriers placed within the guard bands separating the channels of the licensed spectrum. First, the task of choosing the
OFDM-specific parameters, including the number, power, and bandwidth of the subcarriers is formulated as a feasibility
problem to ensure that the CCC does not adversely interfere with the PU operation. Second, for unicast messaging between
a given pair of users, a subset of the guard bands may be chosen, which allows an additional measure of protection for the
adjacent PU spectrum. For this, the multiarm bandit algorithm is used that allows the guard band selection to evolve over
time based on the observed interference from the PU. Results reveal that our proposed CCC ensures connectivity and
improved PU protection with a limited trade-off in data rate when compared to frequencyhopping and cluster-based CCC
schemes.

45 On the Design of Opportunistic MAC Protocols for Multihop Wireless Networks with Beamforming Antennas

Beamforming antennas promise a significant increase in the spatial reuse of the wireless medium when deployed in
multihop wireless networks. However, existing directional Medium Access Control (MAC) protocols with the default
binary exponential backoff mechanism are not capable of fully exploiting the offered potential. In this paper, we
discuss various issues involved in the design of MAC protocols specific for beamforming antennas. Based on our
discussion, we argue that the traditional binary exponential backoff mechanism limits the possible spatial reuse and
aggravates some beamforming-related problems such as deafness and headof- line blocking. To grasp the
transmission opportunities offered by beamforming antennas, we design an Opportunistic Directional MAC
(OPDMAC) protocol for multihop wireless networks. The OPDMAC protocol employs a novel backoff mechanism in
which the node is not forced to undergo idle backoff after a transmission failure but can rather take the opportunity
of transmitting other outstanding packets in other directions. This mechanism minimizes the idle waiting time and
increases the channel utilization significantly and thereby enables OPDMAC to enhance the spatial reusability of the
wireless medium and reduce the impact of the deafness problem without additional overhead. Through extensive
simulations, we demonstrate that OPDMAC enhances the performance in terms of throughput, delay, packet delivery
ratio, and fairness. To further improve its performance, we discuss and evaluate the benefits of carefully choosing
some protocol parameters instead of using the default values commonly used by other directional MAC protocols.


17



46 On the Effectiveness of Monitoring for Intrusion Detection in Mobile Ad Hoc Networks

Several intrusion detection techniques (IDTs) proposed for mobile ad hoc networks rely on each node passively monitoring
the data forwarding by its next hop. This paper presents quantitative evaluations of false positives and their impact on
monitoringbased intrusion detection for ad hoc networks. Experimental results show that, even for a simple three-node
configuration, an actual ad hoc network suffers from high false positives; these results are validated by Markov and
probabilistic models. However, this false positive problem cannot be observed by simulating the same network using
popular ad hoc network simulators, such as ns-2, OPNET or Glomosim. To remedy this, a probabilistic noise generator
model is implemented in the Glomosim simulator. With this revised noise model, the simulated network exhibits the
aggregate false positive behavior similar to that of the experimental testbed. Simulations of larger (50-node) ad hoc
networks indicate that monitoring-based intrusion detection has very high false positives. These false positives can reduce
the network performance or increase the overhead. In a simple monitoring-based system where no secondary and more
accurate methods are used, the false positives impact the network performance in two ways: reduced throughput in normal
networks without attackers and inability to mitigate the effect of attacks in networks with attackers.

47 On the Information Flow Required for Tracking Control in Networks of Mobile Sensing Agents

We design controllers that permit mobile agents with distributed or networked sensing capabilities to track (follow)
desired trajectories, identify what trajectory information must be distributed to each agent for tracking, and develop
methods to minimize the communication needed for the trajectory information distribution.

48 Optimal and Efficient Graph-Based Resource Allocation Algorithms for Multiservice Frame-Based OFDMA Networks

This paper addresses the resource allocation problem in Orthogonal Frequency Division Multiple Access (OFDMA)-based
wireless networks. The resource allocation problem is posed as an optimization problem with individual user constraints.
This formulation provides a special structure that lends to efficient solution of the problem. We develop an optimal
algorithm based on standard graph theory and Lagrangian relaxation. Based on the special structure of the problem, the
proposed resource allocation algorithm attains the optimal solution at a much lower complexity compared to general-
purpose optimization algorithms used by previous OFDMA resource allocation approaches. Moreover, the resource
allocation problem solved by the proposed algorithm supports practical features such as discrete modulation set and
multiple OFDM symbols per resource allocation decision. Furthermore, by assuming even power allocation across the
OFDM subchannels, a suboptimal resource allocation algorithm with lower complexity is developed. The proposed
algorithms enable the system designer to control the tradeoffs among system performance, system complexity, and the
quality of service (QoS) experienced by the users. Extensive simulations are conducted to evaluate the performance and
complexity of the proposed algorithms under different system operating conditions..

49 Optimal Stochastic Location Updates in Mobile Ad Hoc Networks


18

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