This document summarizes a research paper that proposes a distributed flow-based access scheme for slotted-time protocols in ad-hoc wireless networks. The scheme aims to provide proportional fairness between end-to-end flows while constraining buffer overflow probabilities at each node. It formulates the problem as a nonlinear program and presents a distributed dual approach with low computational overhead. Simulation results support that the proposed scheme converges to the unique global optimum and satisfies fairness and quality of service objectives.
Fuzzy Optimized Metric for Adaptive Network RoutingCSCJournals
Network routing algorithms used today calculate least cost (shortest) paths between nodes. The cost of a path is the sum of the cost of all links on that path. The use of a single metric for adaptive routing is insufficient to reflect the actual state of the link. In general, there is a limitation on the accuracy of the link state information obtained by the routing protocol. Hence it becomes useful if two or more metrics can be associated to produce a single metric that can describe the state of the link more accurately. In this paper, a fuzzy inference rule base is implemented to generate the fuzzy cost of each candidate path to be used in routing the incoming calls. This fuzzy cost is based on the crisp values of the different metrics; a fuzzy membership function is defined. The parameters of these membership functions reflect dynamically the requirement of the incoming traffic service as well as the current state of the links in the path. And this paper investigates how three metrics, the mean link bandwidth, queue utilization and the mean link delay, can be related using a simple fuzzy logic algorithm to produce a optimized cost of the link for a certain interval that is more „precise‟ than either of the single metric, to solve routing problem .
A New Efficient Cache Replacement Strategy for Named Data NetworkingIJCNCJournal
The Information-Centric Network (ICN) is a future internet architecture with efficient content retrieval and distribution. Named Data Networking (NDN) is one of the proposed architectures for ICN. NDN’s innetwork caching improves data availability, reduce retrieval delays, network load, alleviate producer load, and limit data traffic. Despite the existence of several caching decision algorithms, the fetching and distribution of contents with minimum resource utilization remains a great challenge. In this paper, we introduce a new cache replacement strategy called Enhanced Time and Frequency Cache Replacement strategy (ETFCR) where both cache hit frequency and cache retrieval time are used to select evicted data chunks. ETFCR adds time cycles between the last two requests to adjust data chunk’s popularity and cache hits. We conducted extensive simulations using the ccnSim simulator to evaluate the performance of ETFCR and compare it to that of some well-known cache replacement strategies. Simulations results show that ETFCR outperforms the other cache replacement strategies in terms of cache hit ratio, and lower content retrieval delay.
For further details contact:
N.RAJASEKARAN B.E M.S 9841091117,9840103301.
IMPULSE TECHNOLOGIES,
Old No 251, New No 304,
2nd Floor,
Arcot road ,
Vadapalani ,
Chennai-26.
Stochastic analysis of random ad hoc networks with maximum entropy deploymentsijwmn
In this paper, we present the first stochastic analysis of the link performance of an ad hoc network modelled
by a single homogeneous Poisson point process (HPPP). According to the maximum entropy principle, the
single HPPP model is mathematically the best model for random deployments with a given node density.
However, previous works in the literature only consider a modified model which shows a discrepancy in the
interference distribution with the more suitable single HPPP model. The main contributions of this paper
are as follows. 1) It presents a new mathematical framework leading to closed form expressions of the
probability of success of both one-way transmissions and handshakes for a deployment modelled by a
single HPPP. Our approach, based on stochastic geometry, can be extended to complex protocols. 2) From
the obtained results, all confirmed by comparison to simulated data, optimal PHY and MAC layer
parameters are determined and the relations between them is described in details. 3) The influence of the
routing protocol on handshake performance is taken into account in a realistic manner, leading to the
confirmation of the intuitive result that the effect of imperfect feedback on the probability of success of a
handshake is only negligible for transmissions to the first neighbour node.
Congestion is said to occur in the network when the resource demands exceed the capacity and packets are lost due to too much queuing in the network. During congestion, the network throughput may drop to zero and the path delay may become very high. A congestion control scheme helps the network to recover from the congestion state. In fact, security plays a vital role in Wireless Ad hoc network. This paper presents a systematic literature review to provide comprehensive and unbiased information about various current model Congestion Control conceptions, proposals, problems and solutions in Ad hoc for safety transportation. For this purpose, a total of 33 articles related to the security model in Congestion Control published between 2008 and 2013 were extracted from the most relevant scientific sources (IEEE Computer Society, ACM Digital Library, Springer Link and Science Direct). However, 18 articles were eventually analyzed due to several reasons such as relevancy and comprehensiveness of discussion presented in the articles. Using the systematic method of review, this paper succeeds to reveal the main security threats and Error control, challenges for security, security requirement in Congestion Control in Wireless Ad hoc network (CCWAN) and future research within this scope.
SECTOR TREE-BASED CLUSTERING FOR ENERGY EFFICIENT ROUTING PROTOCOL IN HETEROG...IJCNCJournal
One of the main challenges for researchers to build routing protocols is how to use energy efficiently to extend the lifespan of the whole wireless sensor networks (WSN) because sensor nodes have limited battery power resources. In this work, we propose a Sector Tree-Based clustering routing protocol (STB-EE) for Energy Efficiency to cope with this problem, where the entire network area is partitioned into dynamic sectors (clusters), which balance the number of alive nodes. The nodes in each sector only communicate with their nearest neighbour by constructing a minimum tree based on the Kruskal algorithm and using mixed distance from candidate node to base station (BS) and remaining energy of candidate nodes to determine which node will become the cluster head (CH) in each cluster? By calculating the duration of time in each round for suitability, STB-EE increases the number of data packets sent to the BS. Our simulation results show that the network lifespan using STB-EE can be improved by about 16% and 10% in comparison to power-efficient gathering in sensor information system (PEGASIS) and energy-efficient PEGASIS-based protocol (IEEPB), respectively.
21 9149 simulation analysis for consistent path identification edit septianIAESIJEECS
As the demand for Mobile Ad hoc Network (MANET) applications grows, so does their use of many essential services where node consistent and stability of the communication paths are of great importance. In this scheme, we propose Simulation Analysis for Consistent Path Identification to Refine the Network Lifetime (CPIR). This technique offers more stable path and transmits the data through the consistent nodes. This article is focused on protecting the route from the inconsistent node in mobile communications to improve the network performance and reduce the energy consumption in the network. The simulation results demonstrate that CPIR provided reduce the energy utilization and improved both the longer lifetimes and increased number of packets delivered.
Fuzzy Optimized Metric for Adaptive Network RoutingCSCJournals
Network routing algorithms used today calculate least cost (shortest) paths between nodes. The cost of a path is the sum of the cost of all links on that path. The use of a single metric for adaptive routing is insufficient to reflect the actual state of the link. In general, there is a limitation on the accuracy of the link state information obtained by the routing protocol. Hence it becomes useful if two or more metrics can be associated to produce a single metric that can describe the state of the link more accurately. In this paper, a fuzzy inference rule base is implemented to generate the fuzzy cost of each candidate path to be used in routing the incoming calls. This fuzzy cost is based on the crisp values of the different metrics; a fuzzy membership function is defined. The parameters of these membership functions reflect dynamically the requirement of the incoming traffic service as well as the current state of the links in the path. And this paper investigates how three metrics, the mean link bandwidth, queue utilization and the mean link delay, can be related using a simple fuzzy logic algorithm to produce a optimized cost of the link for a certain interval that is more „precise‟ than either of the single metric, to solve routing problem .
A New Efficient Cache Replacement Strategy for Named Data NetworkingIJCNCJournal
The Information-Centric Network (ICN) is a future internet architecture with efficient content retrieval and distribution. Named Data Networking (NDN) is one of the proposed architectures for ICN. NDN’s innetwork caching improves data availability, reduce retrieval delays, network load, alleviate producer load, and limit data traffic. Despite the existence of several caching decision algorithms, the fetching and distribution of contents with minimum resource utilization remains a great challenge. In this paper, we introduce a new cache replacement strategy called Enhanced Time and Frequency Cache Replacement strategy (ETFCR) where both cache hit frequency and cache retrieval time are used to select evicted data chunks. ETFCR adds time cycles between the last two requests to adjust data chunk’s popularity and cache hits. We conducted extensive simulations using the ccnSim simulator to evaluate the performance of ETFCR and compare it to that of some well-known cache replacement strategies. Simulations results show that ETFCR outperforms the other cache replacement strategies in terms of cache hit ratio, and lower content retrieval delay.
For further details contact:
N.RAJASEKARAN B.E M.S 9841091117,9840103301.
IMPULSE TECHNOLOGIES,
Old No 251, New No 304,
2nd Floor,
Arcot road ,
Vadapalani ,
Chennai-26.
Stochastic analysis of random ad hoc networks with maximum entropy deploymentsijwmn
In this paper, we present the first stochastic analysis of the link performance of an ad hoc network modelled
by a single homogeneous Poisson point process (HPPP). According to the maximum entropy principle, the
single HPPP model is mathematically the best model for random deployments with a given node density.
However, previous works in the literature only consider a modified model which shows a discrepancy in the
interference distribution with the more suitable single HPPP model. The main contributions of this paper
are as follows. 1) It presents a new mathematical framework leading to closed form expressions of the
probability of success of both one-way transmissions and handshakes for a deployment modelled by a
single HPPP. Our approach, based on stochastic geometry, can be extended to complex protocols. 2) From
the obtained results, all confirmed by comparison to simulated data, optimal PHY and MAC layer
parameters are determined and the relations between them is described in details. 3) The influence of the
routing protocol on handshake performance is taken into account in a realistic manner, leading to the
confirmation of the intuitive result that the effect of imperfect feedback on the probability of success of a
handshake is only negligible for transmissions to the first neighbour node.
Congestion is said to occur in the network when the resource demands exceed the capacity and packets are lost due to too much queuing in the network. During congestion, the network throughput may drop to zero and the path delay may become very high. A congestion control scheme helps the network to recover from the congestion state. In fact, security plays a vital role in Wireless Ad hoc network. This paper presents a systematic literature review to provide comprehensive and unbiased information about various current model Congestion Control conceptions, proposals, problems and solutions in Ad hoc for safety transportation. For this purpose, a total of 33 articles related to the security model in Congestion Control published between 2008 and 2013 were extracted from the most relevant scientific sources (IEEE Computer Society, ACM Digital Library, Springer Link and Science Direct). However, 18 articles were eventually analyzed due to several reasons such as relevancy and comprehensiveness of discussion presented in the articles. Using the systematic method of review, this paper succeeds to reveal the main security threats and Error control, challenges for security, security requirement in Congestion Control in Wireless Ad hoc network (CCWAN) and future research within this scope.
SECTOR TREE-BASED CLUSTERING FOR ENERGY EFFICIENT ROUTING PROTOCOL IN HETEROG...IJCNCJournal
One of the main challenges for researchers to build routing protocols is how to use energy efficiently to extend the lifespan of the whole wireless sensor networks (WSN) because sensor nodes have limited battery power resources. In this work, we propose a Sector Tree-Based clustering routing protocol (STB-EE) for Energy Efficiency to cope with this problem, where the entire network area is partitioned into dynamic sectors (clusters), which balance the number of alive nodes. The nodes in each sector only communicate with their nearest neighbour by constructing a minimum tree based on the Kruskal algorithm and using mixed distance from candidate node to base station (BS) and remaining energy of candidate nodes to determine which node will become the cluster head (CH) in each cluster? By calculating the duration of time in each round for suitability, STB-EE increases the number of data packets sent to the BS. Our simulation results show that the network lifespan using STB-EE can be improved by about 16% and 10% in comparison to power-efficient gathering in sensor information system (PEGASIS) and energy-efficient PEGASIS-based protocol (IEEPB), respectively.
21 9149 simulation analysis for consistent path identification edit septianIAESIJEECS
As the demand for Mobile Ad hoc Network (MANET) applications grows, so does their use of many essential services where node consistent and stability of the communication paths are of great importance. In this scheme, we propose Simulation Analysis for Consistent Path Identification to Refine the Network Lifetime (CPIR). This technique offers more stable path and transmits the data through the consistent nodes. This article is focused on protecting the route from the inconsistent node in mobile communications to improve the network performance and reduce the energy consumption in the network. The simulation results demonstrate that CPIR provided reduce the energy utilization and improved both the longer lifetimes and increased number of packets delivered.
AN EFFECTIVE CONTROL OF HELLO PROCESS FOR ROUTING PROTOCOL IN MANETSIJCNCJournal
In the mobile ad hoc network (MANET) update of link connectivity is necessary to refresh the neighbor tables in data transfer. A existing hello process periodically exchanges the link connectivity information, which is not adequate for dynamic topology. Here, slow update of neighbour table entries causes link failures which affect performance parameter as packet drop, maximum delay, energy consumption, and reduced throughput. In the dynamic hello technique, new neighbour nodes and lost neighbour nodes are used to compute link change rate (LCR) and hello-interval/refresh rate (r). Exchange of link connectivity information at a fast rate consumes unnecessary bandwidth and energy. In MANET resource wastage can be controlled by avoiding the re-route discovery, frequent error notification, and local repair in the entire network. We are enhancing the existing hello process, which shows significant improvement in performance.
Authentication of Secure Data Transmission In Wireless RoutingIJERA Editor
The major objective of our work is to explore a security enhanced dynamic routing algorithm based on distributed routing information widely supported in existing wired and wireless networks. The message authentication is the main area to be considered in WSN’s. Most of the wireless networks are attacked for detecting the data’s that are transmitted in between the users. We aim at the randomization of delivery paths for data transmission to provide considerably small path similarity (i.e., the number of common links between two delivery paths) of two consecutive transmitted packets. The proposed algorithm should be easy to implement and compatible with popular routing protocols, such as the Routing Information Protocol (RIP) for wired networks and Destination-Sequenced Distance Vector (DSDV) protocol for wireless networks over existing infrastructures. These protocols shall not increase the number of control messages if the proposed algorithm is adopted. An analytic study will be presented for the proposed routing algorithm, and a series of simulation study will be conducted to verify the analytic results and to show the capability of the proposed algorithm.
IOSR Journal of Computer Engineering (IOSR-JCE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of computer engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in computer technology. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
A new clustering technique based on replication for MANET routing protocolsTELKOMNIKA JOURNAL
The cluster head nodes in most mobile ad hoc networks (MANET) clustering protocols take on an extraordinary role in managing routing information. The reliability, efficiency and scalability of the clustering in MANET will ultimately be dramatically impacted. In this work we establish a new approach to form the clusters in MANET called the square cluster-based routing protocol (SCBRP). That protocol is based on the theory of replication. The goal of the protocol is to achieve reliability, availability and scalability with in the MANET. The proposed protocol is evaluated by caring the performance analysis using the NS-3 simulator. The performance shows 50% improvementin data delivering ratio in large network size, also shows an improvement in network stability and availability which is reflected in energy consumption measurements and increase in the system lifetime to 20%.
OpenFlow is one of the most commonly used protocols for communication between the
controller and the forwarding element in a software defined network (SDN). A model based on
M/M/1 queues is proposed in [1] to capture the communication between the forwarding element
and the controller. Albeit the model provides useful insight, it is accurate only for the case when
the probability of expecting a new flow is small.
Secondly, it is not straight forward to extend the model in [1] to more than one forwarding
element in the data plane. In this work we propose a model which addresses both these
challenges. The model is based on Jackson assumption but with corrections tailored to the
OpenFlow based SDN network. Performance analysis using the proposed model indicates that
the model is accurate even for the case when the probability of new flow is quite large. Further
we show by a toy example that the model can be extended to more than one node in the data plane.
Impact of energy and link quality indicator with link quality estimators in w...graphhoc
The Link Quality Indicator (LQI) and Residual Energy have a fundamental impact on the network
performance in Wireless Sensor Networks (WSNs) and affects as well in the life time of nodes. This paper
will provide a comparative of Link Quality Estimator, the Link Quality Estimator with Link Quality
Indicator and Link Quality Estimator with Residual Energy. In this paper we develop a Collect Tree
Protocol (CTP) and compare the performance of LQI and Residual Energy, and show their effect on the
packet delivery ratio and throughput, covering the characteristics of low-power links, and their
performance to the best of our knowledge, we believe that our efforts would have implementations on
embedded application.
A New Analysis for Wavelength Translation in Regular WDM NetworksVishal Sharma, Ph.D.
We present a new analysis of wavelength translation in
regular, all-optical WDM networks, that is simple, computationally
inexpensive, and accurate for both low and high
network loads. In a network with
k
wavelengths per link,
we model the output link by an auxiliary
M/M/k/k
queueing
system. We then obtain a closed-form expression for
the probability
P succ
that a session arriving at a node at a
random time successfully establishes a connection from its
source node to its destination node. Unlike previous analyses,
which use the link independence blocking assumption,
we account for the dependence between the acquisition of
wavelengths on successive links of the session’s path. Based
on the success probability, we show that the throughput per
wavelength increases superlinearly (as expected) as we increase
the number of wavelengths per link; however, the
extent of this superlinear increase in throughput saturates
rather quickly. This suggests some interesting possibilities
for network provisioning in an all-optical network. We verify the accuracy of our analysis via simulations for the torus
and hypercube networks.
SCTP-MANET NEW EXTENSION OF SCTP PROTOCOL FOR THE OPTIMIZATION OF MANET PERFO...ijwmn
Ad Hoc mobile networks are constituted of nodes that move freely without a centralized administration.
These nodes contribute in the routing of data packets that are sent by a source. This happens when the
latter is not capable of reaching its destination. On the other hand, their mobility causes recurrent
breakdowns of the routing paths notably with sparse MANET. In order to optimize the performance of such
networks, we suggest a new extension of protocols: Stream Control Transmission Protocols (SCTP) named
SCTP-MANET. Their main function is therefore to improve the availability of the links in sparse MANET
protocols. This could be achieved by a better integration of Multihoming. With this aim in mind, this new
extension is based on a cross-layer interface between transport and routing layers as well as the use of
specific messages.
Efficient routing mechanism using cycle based network and k hop security in a...ijait
In a multi-domain network, Topology Aggregation (TA) may be adopted to provide limited information
regarding intra cluster connectivity without revealing detailed topology information. Nodes are grouped
into the cluster. Every cluster has border nodes, which is used for data transmission between source and
destination. The K-hop security can be used for the purpose of securing the data communication. The
topologies are spanning tree and balanced tree that can be used to reduce bandwidth overhead, delivery
delay and to increase throughput and packet delivery ratio. The shortest path can be found using
Bhandari’s algorithm and Cycle-Based Minimum-Cost Domain-Disjoint Paths (CMCDP) Algorithm for
establish the second path in the network . These topologies are compared to demonstrate the advantage of
finding shortest path using Bhandari’s algorithm.
On modeling controller switch interaction in openflow based sdnsIJCNCJournal
With an increase in number of software defined network (SDN) deployments,and OpenFlow consolidating as the protocol of choice for controller-switch interactions, a need to analytically model the system for performance analysis is increasing. An attempt has previously been made in [1] to model the syste considering both a controller and a switch as an M/M/1 queue. The method, although useful, lacks accuracy for higher probabilities of new flows entering the network. The approach is also deficient of
details on how it can be extended to more than one node in the data plane.These two short-comings are addressed in this paper where thecontroller and switch are modeled
collectively as Jackson’s network, with essential tuning to suit OpenFlow-based SDN. The consequent analysis shows the resilience of the model even for higher number of new flow entries. An example is also used
to illustrate the case of multiple nodes in the data plane.
Towards Seamless TCP Congestion Avoidance in Multiprotocol EnvironmentsIDES Editor
In this paper we explore the area of congestion
avoidance in computer networks. We provide a brief overview
of the current state of the art in congestion avoidance and also
list our extension to the TCP congestion avoidance mechanism.
This extension was previously published on an international
forum and in this paper we describe an improved version which
allows multiprotocol support. We list preliminary results
carried out in a simulation environment.
New introduced approach called Advanced Notification
Congestion System (ACNS) allows TCP flows prioritization
based on the TCP flow age and priority carried in the header
of the network layer protocol. The aim of this approach is to
provide more bandwidth for young and high prioritized TCP
flows by means of penalizing old greedy flows with a low
priority. Using ACNS, substantial network performance
increase can be achieved.
Analysis of data transmission in wireless lan for 802.11 e2 eteSAT Journals
Abstract The aim of this paper is to investigate the transmission of data between client and server through different IEEE 802.11 wireless LAN multi- HOP network. To improve this issue, the transmission opportunity (TXOP) mechanism is defined in the IEEE 802.11e standard, with which a wireless node can transmit multiple frames consecutively for a maximum channel occupancy time, called TXOP limit. This paper considers the performance of the TXOP mechanism for multi-hop wireless networks. Focusing on a three-node chain topology, we model it as a tandem queuing network with two nodes. The E2ET is derived and the analysis is validated by simulation. Numerical results show that the TXOP mechanism works well for multi-hop wireless networks. It is also shown that adjusting TXOP limit is significantly important in order to increase the overall throughput. In terms of multi-hop wireless networks, there is little analytical work with regard to the E2ET performance. One of the rationales for the analytical difficulty for multi-hop wireless networks is that IEEE 802.11 MAC protocol is too complex to model the behavior of multi-hop frame transmissions. Keywords: IEEE 802.11e, multi-hop wireless LAN, TXOP, E2ET
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Mitigating Link Failures & Implementing Security Mechanism in Multipath Flows...Eswar Publications
The transmission of a traffic flows with a certain bandwidth demand over a single network path is either not possible or not cost-effective. In these cases, it is veritably periodic usable to improve focus the network's bandwidth appliance by breaking the traffic flow upon multiple qualified paths. Using multiple paths for the equivalent traffic flow increases the certainty of the network, it absorbs deluxe forwarding resources from the
network nodes and also it overcomes link failure provide security. In this paper, we illustrate several problems related to splitting a traffic flow over multiple paths while minimizing the absorption of forwarding resources mitigates failures and implementing security.
Lightning Talk #9: How UX and Data Storytelling Can Shape Policy by Mika Aldabaux singapore
How can we take UX and Data Storytelling out of the tech context and use them to change the way government behaves?
Showcasing the truth is the highest goal of data storytelling. Because the design of a chart can affect the interpretation of data in a major way, one must wield visual tools with care and deliberation. Using quantitative facts to evoke an emotional response is best achieved with the combination of UX and data storytelling.
Succession “Losers”: What Happens to Executives Passed Over for the CEO Job?
By David F. Larcker, Stephen A. Miles, and Brian Tayan
Stanford Closer Look Series
Overview:
Shareholders pay considerable attention to the choice of executive selected as the new CEO whenever a change in leadership takes place. However, without an inside look at the leading candidates to assume the CEO role, it is difficult for shareholders to tell whether the board has made the correct choice. In this Closer Look, we examine CEO succession events among the largest 100 companies over a ten-year period to determine what happens to the executives who were not selected (i.e., the “succession losers”) and how they perform relative to those who were selected (the “succession winners”).
We ask:
• Are the executives selected for the CEO role really better than those passed over?
• What are the implications for understanding the labor market for executive talent?
• Are differences in performance due to operating conditions or quality of available talent?
• Are boards better at identifying CEO talent than other research generally suggests?
We’re all trying to find that idea or spark that will turn a good project into a great project. Creativity plays a huge role in the outcome of our work. Harnessing the power of collaboration and open source, we can make great strides towards excellence. Not just for designers, this talk can be applicable to many different roles – even development. In this talk, Seasoned Creative Director Sara Cannon is going to share some secrets about creative methodology, collaboration, and the strong role that open source can play in our work.
The impact of innovation on travel and tourism industries (World Travel Marke...Brian Solis
From the impact of Pokemon Go on Silicon Valley to artificial intelligence, futurist Brian Solis talks to Mathew Parsons of World Travel Market about the future of travel, tourism and hospitality.
The Six Highest Performing B2B Blog Post FormatsBarry Feldman
If your B2B blogging goals include earning social media shares and backlinks to boost your search rankings, this infographic lists the size best approaches.
AN EFFECTIVE CONTROL OF HELLO PROCESS FOR ROUTING PROTOCOL IN MANETSIJCNCJournal
In the mobile ad hoc network (MANET) update of link connectivity is necessary to refresh the neighbor tables in data transfer. A existing hello process periodically exchanges the link connectivity information, which is not adequate for dynamic topology. Here, slow update of neighbour table entries causes link failures which affect performance parameter as packet drop, maximum delay, energy consumption, and reduced throughput. In the dynamic hello technique, new neighbour nodes and lost neighbour nodes are used to compute link change rate (LCR) and hello-interval/refresh rate (r). Exchange of link connectivity information at a fast rate consumes unnecessary bandwidth and energy. In MANET resource wastage can be controlled by avoiding the re-route discovery, frequent error notification, and local repair in the entire network. We are enhancing the existing hello process, which shows significant improvement in performance.
Authentication of Secure Data Transmission In Wireless RoutingIJERA Editor
The major objective of our work is to explore a security enhanced dynamic routing algorithm based on distributed routing information widely supported in existing wired and wireless networks. The message authentication is the main area to be considered in WSN’s. Most of the wireless networks are attacked for detecting the data’s that are transmitted in between the users. We aim at the randomization of delivery paths for data transmission to provide considerably small path similarity (i.e., the number of common links between two delivery paths) of two consecutive transmitted packets. The proposed algorithm should be easy to implement and compatible with popular routing protocols, such as the Routing Information Protocol (RIP) for wired networks and Destination-Sequenced Distance Vector (DSDV) protocol for wireless networks over existing infrastructures. These protocols shall not increase the number of control messages if the proposed algorithm is adopted. An analytic study will be presented for the proposed routing algorithm, and a series of simulation study will be conducted to verify the analytic results and to show the capability of the proposed algorithm.
IOSR Journal of Computer Engineering (IOSR-JCE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of computer engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in computer technology. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
A new clustering technique based on replication for MANET routing protocolsTELKOMNIKA JOURNAL
The cluster head nodes in most mobile ad hoc networks (MANET) clustering protocols take on an extraordinary role in managing routing information. The reliability, efficiency and scalability of the clustering in MANET will ultimately be dramatically impacted. In this work we establish a new approach to form the clusters in MANET called the square cluster-based routing protocol (SCBRP). That protocol is based on the theory of replication. The goal of the protocol is to achieve reliability, availability and scalability with in the MANET. The proposed protocol is evaluated by caring the performance analysis using the NS-3 simulator. The performance shows 50% improvementin data delivering ratio in large network size, also shows an improvement in network stability and availability which is reflected in energy consumption measurements and increase in the system lifetime to 20%.
OpenFlow is one of the most commonly used protocols for communication between the
controller and the forwarding element in a software defined network (SDN). A model based on
M/M/1 queues is proposed in [1] to capture the communication between the forwarding element
and the controller. Albeit the model provides useful insight, it is accurate only for the case when
the probability of expecting a new flow is small.
Secondly, it is not straight forward to extend the model in [1] to more than one forwarding
element in the data plane. In this work we propose a model which addresses both these
challenges. The model is based on Jackson assumption but with corrections tailored to the
OpenFlow based SDN network. Performance analysis using the proposed model indicates that
the model is accurate even for the case when the probability of new flow is quite large. Further
we show by a toy example that the model can be extended to more than one node in the data plane.
Impact of energy and link quality indicator with link quality estimators in w...graphhoc
The Link Quality Indicator (LQI) and Residual Energy have a fundamental impact on the network
performance in Wireless Sensor Networks (WSNs) and affects as well in the life time of nodes. This paper
will provide a comparative of Link Quality Estimator, the Link Quality Estimator with Link Quality
Indicator and Link Quality Estimator with Residual Energy. In this paper we develop a Collect Tree
Protocol (CTP) and compare the performance of LQI and Residual Energy, and show their effect on the
packet delivery ratio and throughput, covering the characteristics of low-power links, and their
performance to the best of our knowledge, we believe that our efforts would have implementations on
embedded application.
A New Analysis for Wavelength Translation in Regular WDM NetworksVishal Sharma, Ph.D.
We present a new analysis of wavelength translation in
regular, all-optical WDM networks, that is simple, computationally
inexpensive, and accurate for both low and high
network loads. In a network with
k
wavelengths per link,
we model the output link by an auxiliary
M/M/k/k
queueing
system. We then obtain a closed-form expression for
the probability
P succ
that a session arriving at a node at a
random time successfully establishes a connection from its
source node to its destination node. Unlike previous analyses,
which use the link independence blocking assumption,
we account for the dependence between the acquisition of
wavelengths on successive links of the session’s path. Based
on the success probability, we show that the throughput per
wavelength increases superlinearly (as expected) as we increase
the number of wavelengths per link; however, the
extent of this superlinear increase in throughput saturates
rather quickly. This suggests some interesting possibilities
for network provisioning in an all-optical network. We verify the accuracy of our analysis via simulations for the torus
and hypercube networks.
SCTP-MANET NEW EXTENSION OF SCTP PROTOCOL FOR THE OPTIMIZATION OF MANET PERFO...ijwmn
Ad Hoc mobile networks are constituted of nodes that move freely without a centralized administration.
These nodes contribute in the routing of data packets that are sent by a source. This happens when the
latter is not capable of reaching its destination. On the other hand, their mobility causes recurrent
breakdowns of the routing paths notably with sparse MANET. In order to optimize the performance of such
networks, we suggest a new extension of protocols: Stream Control Transmission Protocols (SCTP) named
SCTP-MANET. Their main function is therefore to improve the availability of the links in sparse MANET
protocols. This could be achieved by a better integration of Multihoming. With this aim in mind, this new
extension is based on a cross-layer interface between transport and routing layers as well as the use of
specific messages.
Efficient routing mechanism using cycle based network and k hop security in a...ijait
In a multi-domain network, Topology Aggregation (TA) may be adopted to provide limited information
regarding intra cluster connectivity without revealing detailed topology information. Nodes are grouped
into the cluster. Every cluster has border nodes, which is used for data transmission between source and
destination. The K-hop security can be used for the purpose of securing the data communication. The
topologies are spanning tree and balanced tree that can be used to reduce bandwidth overhead, delivery
delay and to increase throughput and packet delivery ratio. The shortest path can be found using
Bhandari’s algorithm and Cycle-Based Minimum-Cost Domain-Disjoint Paths (CMCDP) Algorithm for
establish the second path in the network . These topologies are compared to demonstrate the advantage of
finding shortest path using Bhandari’s algorithm.
On modeling controller switch interaction in openflow based sdnsIJCNCJournal
With an increase in number of software defined network (SDN) deployments,and OpenFlow consolidating as the protocol of choice for controller-switch interactions, a need to analytically model the system for performance analysis is increasing. An attempt has previously been made in [1] to model the syste considering both a controller and a switch as an M/M/1 queue. The method, although useful, lacks accuracy for higher probabilities of new flows entering the network. The approach is also deficient of
details on how it can be extended to more than one node in the data plane.These two short-comings are addressed in this paper where thecontroller and switch are modeled
collectively as Jackson’s network, with essential tuning to suit OpenFlow-based SDN. The consequent analysis shows the resilience of the model even for higher number of new flow entries. An example is also used
to illustrate the case of multiple nodes in the data plane.
Towards Seamless TCP Congestion Avoidance in Multiprotocol EnvironmentsIDES Editor
In this paper we explore the area of congestion
avoidance in computer networks. We provide a brief overview
of the current state of the art in congestion avoidance and also
list our extension to the TCP congestion avoidance mechanism.
This extension was previously published on an international
forum and in this paper we describe an improved version which
allows multiprotocol support. We list preliminary results
carried out in a simulation environment.
New introduced approach called Advanced Notification
Congestion System (ACNS) allows TCP flows prioritization
based on the TCP flow age and priority carried in the header
of the network layer protocol. The aim of this approach is to
provide more bandwidth for young and high prioritized TCP
flows by means of penalizing old greedy flows with a low
priority. Using ACNS, substantial network performance
increase can be achieved.
Analysis of data transmission in wireless lan for 802.11 e2 eteSAT Journals
Abstract The aim of this paper is to investigate the transmission of data between client and server through different IEEE 802.11 wireless LAN multi- HOP network. To improve this issue, the transmission opportunity (TXOP) mechanism is defined in the IEEE 802.11e standard, with which a wireless node can transmit multiple frames consecutively for a maximum channel occupancy time, called TXOP limit. This paper considers the performance of the TXOP mechanism for multi-hop wireless networks. Focusing on a three-node chain topology, we model it as a tandem queuing network with two nodes. The E2ET is derived and the analysis is validated by simulation. Numerical results show that the TXOP mechanism works well for multi-hop wireless networks. It is also shown that adjusting TXOP limit is significantly important in order to increase the overall throughput. In terms of multi-hop wireless networks, there is little analytical work with regard to the E2ET performance. One of the rationales for the analytical difficulty for multi-hop wireless networks is that IEEE 802.11 MAC protocol is too complex to model the behavior of multi-hop frame transmissions. Keywords: IEEE 802.11e, multi-hop wireless LAN, TXOP, E2ET
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Mitigating Link Failures & Implementing Security Mechanism in Multipath Flows...Eswar Publications
The transmission of a traffic flows with a certain bandwidth demand over a single network path is either not possible or not cost-effective. In these cases, it is veritably periodic usable to improve focus the network's bandwidth appliance by breaking the traffic flow upon multiple qualified paths. Using multiple paths for the equivalent traffic flow increases the certainty of the network, it absorbs deluxe forwarding resources from the
network nodes and also it overcomes link failure provide security. In this paper, we illustrate several problems related to splitting a traffic flow over multiple paths while minimizing the absorption of forwarding resources mitigates failures and implementing security.
Lightning Talk #9: How UX and Data Storytelling Can Shape Policy by Mika Aldabaux singapore
How can we take UX and Data Storytelling out of the tech context and use them to change the way government behaves?
Showcasing the truth is the highest goal of data storytelling. Because the design of a chart can affect the interpretation of data in a major way, one must wield visual tools with care and deliberation. Using quantitative facts to evoke an emotional response is best achieved with the combination of UX and data storytelling.
Succession “Losers”: What Happens to Executives Passed Over for the CEO Job?
By David F. Larcker, Stephen A. Miles, and Brian Tayan
Stanford Closer Look Series
Overview:
Shareholders pay considerable attention to the choice of executive selected as the new CEO whenever a change in leadership takes place. However, without an inside look at the leading candidates to assume the CEO role, it is difficult for shareholders to tell whether the board has made the correct choice. In this Closer Look, we examine CEO succession events among the largest 100 companies over a ten-year period to determine what happens to the executives who were not selected (i.e., the “succession losers”) and how they perform relative to those who were selected (the “succession winners”).
We ask:
• Are the executives selected for the CEO role really better than those passed over?
• What are the implications for understanding the labor market for executive talent?
• Are differences in performance due to operating conditions or quality of available talent?
• Are boards better at identifying CEO talent than other research generally suggests?
We’re all trying to find that idea or spark that will turn a good project into a great project. Creativity plays a huge role in the outcome of our work. Harnessing the power of collaboration and open source, we can make great strides towards excellence. Not just for designers, this talk can be applicable to many different roles – even development. In this talk, Seasoned Creative Director Sara Cannon is going to share some secrets about creative methodology, collaboration, and the strong role that open source can play in our work.
The impact of innovation on travel and tourism industries (World Travel Marke...Brian Solis
From the impact of Pokemon Go on Silicon Valley to artificial intelligence, futurist Brian Solis talks to Mathew Parsons of World Travel Market about the future of travel, tourism and hospitality.
The Six Highest Performing B2B Blog Post FormatsBarry Feldman
If your B2B blogging goals include earning social media shares and backlinks to boost your search rankings, this infographic lists the size best approaches.
Each technological age has been marked by a shift in how the industrial platform enables companies to rethink their business processes and create wealth. In the talk I argue that we are limiting our view of what this next industrial/digital age can offer because of how we read, measure and through that perceive the world (how we cherry pick data). Companies are locked in metrics and quantitative measures, data that can fit into a spreadsheet. And by that they see the digital transformation merely as an efficiency tool to the fossil fuel age. But we need to stretch further…
Congestion Control in Manets Using Hybrid Routing ProtocolIOSR Journals
Abstract : As the network size increases the probability of congestion occurrence at nodes increases. This is because of the event driven nature of ad hoc networks that leads to unpredictable network load. As a result congestion may occur at the nodes which receive more data than that can be forwarded and cause packet losses. In this paper we propose a hybrid scheme that attempts to avoid packet loss due to congestion as well as reduce end to end delay in delivering data packets by combining two protocols- Destination sequenced distance vector routing (DSDV), which is a table driven or proactive protocol and Improved Ad-hoc on demand vector routing (IAODV) which is an on-demand or reactive protocol that reduces packet loss due to congestion. The strategy adopted is use DSDV for path selection and if congestion occurs than switch over to IAODV. The routing performance of this model is then compared with IAODV and DSDV in terms of end to end delay, throughput and packet delivery fraction. Keywords- DSDV, Hybrid protocol, AODV, IAODV, MANET
Congestion Control in Manets Using Hybrid Routing ProtocolIOSR Journals
As the network size increases the probability of congestion occurrence at nodes increases. This is
because of the event driven nature of ad hoc networks that leads to unpredictable network load. As a result
congestion may occur at the nodes which receive more data than that can be forwarded and cause packet losses.
In this paper we propose a hybrid scheme that attempts to avoid packet loss due to congestion as well as reduce
end to end delay in delivering data packets by combining two protocols- Destination sequenced distance vector
routing (DSDV), which is a table driven or proactive protocol and Improved Ad-hoc on demand vector routing
(IAODV) which is an on-demand or reactive protocol that reduces packet loss due to congestion. The strategy
adopted is use DSDV for path selection and if congestion occurs than switch over to IAODV. The routing
performance of this model is then compared with IAODV and DSDV in terms of end to end delay, throughput
and packet delivery fraction
A scalable and power efficient solution for routing in mobile ad hoc network ...ijmnct
Mobile Ad Hoc Network (MANET) is a very dynamic and infrastructure-less ad hoc network. The actual
network size depends on the application and the protocols developed for the routing for this kind of
networks should be scalable. MANET is a resource limited network and therefore the developed routing
algorithm for packet transmission should be power and bandwidth efficient. These kinds of dynamic
networks should operate with minimal management overhead. The management functionality of the
network increases with number of nodes and reduces the performance of the network. Here, in this paper,
we have designed all identical nodes in the cluster except the cluster head and this criterion reduces the
management burden on the network. Graph theoretic routing algorithm is used to develop route for packet
transmission by using the minimum resources. In this paper, we developed routing algorithm for cluster
based MANET and finds a path from source to destination using minimum cumulative degree path. Our
simulation results show that this routing algorithm provide efficient routing path with the increasing
number of nodes and uses multi-hop connectivity for intra-cluster to utilize minimum power for packet
transmission irrespective of number of nodes in the network.
Efficient and Fair Bandwidth Allocation AQM Scheme for Wireless NetworksCSCJournals
Heterogeneous Wireless Networks are considered nowadays as one of the potential areas in research and development. The traffic management’s schemes that have been used at the fusion points between the different wireless networks are classical and conventional. This paper is focused on developing a novel scheme to overcome the problem of traffic congestion in the fusion point router interconnected the heterogeneous wireless networks. The paper proposed an EF-AQM algorithm which provides an efficient and fair allocation of bandwidth among different established flows. Finally, the proposed scheme developed, tested and validated through a set of experiments to demonstrate the relative merits and capabilities of a proposed scheme
CONGESTION AWARE LINK COST ROUTING FOR MANETSIJCNCJournal
Due to the dynamic topology, self-configuration and decentralized nature of Mobile Ad hoc Network
(MANET), it provides many benefits in wireless networks and is easy to deploy. But the transmission of
data over ad hoc networks has elevated many technical issues for successful routing. Congestion is one of
the important issues which cause performance degradation of a network, due to long delay and high packet
loss. This paper proposes a Congestion aware Link Cost Routing for MANET where the protocol finds a
path with optimized linked cost based on SNR, Link delay, and the and remaining battery power. Along
with this optimization, in this protocol, every node finds its congestion status and participates in the route
discovery on the basis of its status. Data forwarding is also done based on the congestion status at the time
of forwarding. The protocol results in better performance in terms of packet delivery fraction, end to end
delay, throughput, and packet drop when compared to existing protocols.
Wireless Mesh Network rose as a promising innovation for providing quick and productive communication for which numerous algorithms have been proposed in networking infrastructure. For routing there are various performance parameters such as throughput, network congestion, resiliency, fairness, robustness, network jitter, delay, stability, optimality, simplicity, completeness etc. Robustness provides the capability to deal with all the failures that come across during the connection in the network to increase the network performance. In this paper we have studied and analyzed three algorithms namely on robustness parameter Resilient multicasting [2], Resilient Opportunistic Mesh Routing for Wireless Mesh Network (ROMER) [3], and Buffer Based Routing (BBR) [4], in Wireless Mesh Networks. Analysis through various parameters such as network congestion, network throughput and resiliency [5], shows network performance of BBR is better.
An Approach for Enhanced Performance of Packet Transmission over Packet Switc...ijceronline
With the increased use of real time applications, there is a need for improved network traffic and bandwidth management. Switches are being used by computer networks for enabling connection between those hosts which are not connected by a direct link. When two or more than two host attempt to transmit packet at the same time, collision in data packets occurred. In this paper an optimized performance of local area network in terms of collision count and some other parameter have been investigated using simulation model. Simulation results have been obtained in different network scenarios by varying the number of devices in the network.
A novel routing technique for mobile ad hoc networks (manet)ijngnjournal
Actual network size depends on the application and the protocols developed for the routing for this kind of
networks should be scalable and efficient. Each routing protocol should support small as well as large
scale networks very efficiently. As the number of node increase, it increases the management functionality
of the network. Graph theoretic approach traditionally was applied to networks where nodes are static or
fixed. In this paper, we have applied the graph theoretic routing to MANET where nodes are mobile. Here,
we designed all identical nodes in the cluster except the cluster head and this criterion reduces the
management burden on the network. Each cluster supports a few nodes with a cluster head. The intracluster
connectivity amongst the nodes within the cluster is supported by multi-hop connectivity to ensure
handling mobility in such a way that no service disruption can occur. The inter-cluster connectivity is also
achieved by multi-hop connectivity. However, for inter-cluster communications, only cluster heads are
connected. This paper demonstrates graph theoretic approach produces an optimum multi-hop connectivity
path based on cumulative minimum degree that minimizes the contention and scheduling delay end-toend.
It is applied to both intra-cluster communications as well as inter-cluster communications. The
performance shows that having a multi-hop connectivity for intra-cluster communications is more power
efficient compared to broadcast of information with maximum power coverage. We also showed the total
number of required intermediate nodes in the transmission from source to destination. However, dynamic
behavior of the nodes requires greater understanding of the node degree and mobility at each instance of
time in order to maintain end-to-end QoS for multi-service provisioning. Our simulation results show that
the proposed graph theoretic routing approach will reduce the overall delay and improves the physical
layer data frame transmission.
Quadrant Based DIR in CWin Adaptation Mechanism for Multihop Wireless NetworkIJCI JOURNAL
In Multihop Wireless Networks, traffic forwarding capability of each node varies according to its level of contention. Each node can yield its channel access opportunity to its neighbouring nodes, so that all the nodes can evenly share the channel and have similar forwarding capability. In this manner the wireless channel is utilized effectively, which is achieved using Contention Window Adaptation Mechanism (CWAM). This mechanism achieves a higher end-to-end throughout but consumes the network power to a higher level. So, a newly proposed algorithm Quadrant- Based Directional Routing Protocol (Q-DIR) is implemented as a cross-layer with CWAM, to reduce the total network power consumption through limited flooding and also reduce the routing overheads, which eventually increases overall network throughput. This algorithm limits the broadcast region to a quadrant where the source node and the destination nodes are located. Implementation of the algorithm is done in Linux based NS-2 simulator
An Adaptive Routing Algorithm for Communication Networks using Back Pressure...IJMER
The basic idea of backpressure techniques is to prioritize transmissions over links that have
the highest queue differentials. Backpressure method effectively makes packets flow through the network
as though pulled by gravity towards the destination end, which has the smallest queue size of zero. Under
high traffic conditions, this method works very well, and backpressure is able to fully utilize the available
network resources in a highly dynamic fashion. Under low traffic conditions, however, because many
other hosts may also have a small or zero queue size, there is inefficiency in terms of an increase in
delay, as packets may loop or take a long time to make their way to the destination end. In this paper we
use the concept of shadow queues. Each node has to maintain some counters, called as shadow queues,
per destination. This is very similar to the idea of maintaining a routing table (for routing purpose) per
destination. Using the concept of shadow queues, we partially decouple routing and the scheduling. A
shadow network is maintained to update a probabilistic routing table that packets use upon arrival at a
node. The same shadow network, with back-pressure technique, is used to activate transmissions between
nodes. The routing algorithm is designed to minimize the average number of hops used by the packets in
the network. This idea, along with the scheduling and routing decoupling, leads to delay reduction
compared with the traditional back-pressure algorithm
Congestion Control in Wireless Sensor Networks Using Genetic AlgorithmEditor IJCATR
Sensor network consists of a large number of small nods, strongly interacting with the physical environment, takes
environmental data through sensors, and reacts after processing on information. Wireless network technologies are widely used in most
applications. As wireless sensor networks have many activities in the field of information transmission, network congestion cannot be
thus avoided. So it seems necessary that some new methods can control congestion and use existing resources for providing better traffic
demands. Congestion increases packet loss and retransmission of removed packets and also wastes of energy. In this paper, a novel
method is presented for congestion control in wireless sensor networks using genetic algorithm. The results of simulation show that the
proposed method, in comparison with the algorithm LEACH, can significantly improve congestion control at high speeds.
Link Prediction And Link Establishment Based On Network Nodes Life Time In Mo...inventionjournals
In this paper we propose a new modified adhoc routing algorithm for adhoc network that locally repairs a link failure and also conflicts the noise and link modification simultaneously. Due to topology changes caused by nodes’ mobility in adhoc network, the link routes get disconnected frequently. Our proposed scheme does a local repair of link failure and also takes care of malicious nodes with the help of a reliability measure while performing route discovery using link-prediction routing algorithm(LPRA). These two performance metrics are integrated by Route link-prediction algorithm. This algorithm is carried out as follows, Select the least dynamic route link with the longest lifetime for persistent data forwarding. Node Lifetime and link lifetime prediction methods. The receiver can measure the signal strength when it receives the packets from sender in same power level and then it calculates the distance between two nodes by applying the radio propagation model in LPRA using adhoc network. Simulation results show that our proposed schemeperforms better in comparison to a popular existing technique
A comparative study in wireless sensor networksijwmn
Sensor networks consist of a large number of small, low-powered wireless nodes with limited computation,
communication, and sensing abilities, in a battery-powered sensor network, energy and communication
bandwidth are a precious resources. Thus, there is a need to adapt the networking process to match the
application in order to minimize the resources consumed and extend the life of the network. In this paper,
we introduce a comparative study in different routing algorithms that propose vital solutions to the most
important issues that should be taken into account when designing wireless network which are reliability,
lifetime, communication bandwidth, transmission rand, and finally the limited energy issue, so we will
introduce their algorithms and discuss how did they propose to solve such of these challenges and finally
we will do some evaluation to each approach.
Similar to Enforcing end to-end proportional fairness with bounded buffer overflow probabilities in ad-hoc wireless networks (20)
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
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Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Enforcing end to-end proportional fairness with bounded buffer overflow probabilities in ad-hoc wireless networks
1. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
ENFORCING END-TO-END
PROPORTIONAL FAIRNESS WITH
BOUNDED BUFFER OVERFLOW
PROBABILITIES IN AD-HOC WIRELESS
NETWORKS
Nikhil Singh1and Ramavarapu Sreenivas2
1
2
Yahoo! Labs, Champaign, IL 61820, USA
Coordinated Science Laboratory & Industrial and Enterprise Systems Engineering,
University of Illinois at Urbana-Champaign, Urbana, IL 61820
ABSTRACT
In this paper, we present a distributed flow-based access scheme for slotted-time protocols, that provides
proportional fairness in ad-hoc wireless networks under constraints on the buffer overflow probabilities at
each node. The proposed scheme requires local information exchange at the link-layer and end-to-end
information exchange at the transport-layer, and is cast as a nonlinear program. A medium access control
protocol is said to be proportionally fair with respect to individual end-to-end flows in a network, if the
product of the end-to-end flow rates is maximized. A key contribution of this work lies in the construction of
a distributed dual approach that comes with low computational overhead. We discuss the convergence
properties of the proposed scheme and present simulation results to support our conclusions.
KEYWORDS
Wireless LAN, Access protocols, Resource management.
1. INTRODUCTION
In this paper we consider an ad-hoc wireless network [1] that carries several flows between
various source-destination pairs under a slotted-time medium access control (MAC) protocol.
Specifically, we are interested in a distributed scheme for the assignment of the network’s
resources among flows, which is fair in terms of end-to-end flow rates. We assume that eachnode
in the network has a finite buffer assigned to each flow routed through it. In addition to the
objective of fairness, we are also interested in ensuring that the buffer overflow probability at
each node does not exceed a pre-determined value.
The literature contains several references to fairness and its impact on the network performance.
It has been observed by many researchers that the contention control mechanism used in 802.11MAC [2] can be inefficient [3]. In [4], [5] a list of modifications is presented, that eliminates the
unfairness commonly seen in the 802.11-MAC. The literature also contains a large volume of
references (cf. [6], [7], [8], for example) where it is assumed that each network flow/link is
associated with a concave utility function that could be maximized. In particular, for proportional
fairness, it is assumed that the utility function has the form of log x, where x denotes the flow rate
DOI : 10.5121/ijwmn.2013.5501
01
2. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
[6]. It is of interest to schedule individual transmissions on the links so as to maximize the sum of
the utilities of the consumers. To achieve fairness, the schemes outlined in the above-mentioned
references use a penalty function that is updated by some form of feedback from the network.
Using an appropriately defined cost that is implicitly dependent on the requested rates of each
node within a neighbourhood, the penalty is typically the total cost of all nodes in the network. A
node maximizes (its view of) a common performance function, given by the difference between
the total utility and the penalty. An overview of network resource allocation through utility
maximization is presented in [9].
In [10], the authors have addressed the problem of providing proportional fairness by considering
joint optimization at both transport and link layers. Two algorithms are proposed for solving the
problem in a distributed manner that converges to the globally optimal solutions. These results,
generalized in [11], are based on the dual and the primal algorithms in convex optimization and
need end-to-end feedback information to update variables maintained at the nodes. The
algorithms presented in [10], [11] are oblivious of the queue dynamics of the network, which may
increase delays and packet loss. Although our work is closely related to [10], [11], the problem
formulation and the proposed solution differ significantly.
In [12], the solution approach uses a class of queue backpressure random access algorithms
(QBRA), where the actual queue-lengths of the flows are used to determine any node’s channel
access probabilities. In this distributed algorithm, a node uses the queue-length information in a
close neighbourhood to determine its channel access probability to achieve proportionally fair
rates and queue stability. This scheme has the advantage that no optimization needs to be
performedand nodes can achieve proportional fairness just by exchanging the queue information
in the local neighbourhood. However, the frequency of exchange of this information plays a vital
role in determining the performance of this algorithm. In optimization-based schemes, once the
flow rates have converged to the optimum, the frequency of information exchange does not play a
significant role until the network topology, or the number of flows in the network, change.
In a different approach, several policies have recently been proposed for achieving rates close to
the maximum throughput region through dynamic link scheduling [13], [14], [15], [16]. These
scheduling algorithms use maximal matchings in every time slot using local contention
algorithms and achieve near maximal schedules. Some policies also guarantee fairness of rate
allocation among different sessions.
Quality of Service(QoS) is an important issue in ad-hoc wireless networks. Service guarantees can
be provided for delays, packet loss, jitter and throughput based on the application requirements.
Our approach in this work is to combine the QoS guarantee in addition to providing proportional
fairness. Our main contributions are as follows:
1. We derive an expression for the buffer overflow probabilities for discrete-time queues.
This derivation uses the fact that there cannot be simultaneous arrivals and departures
at a node within the same slot in Aloha-type networks that do not have packet capture
mechanisms.
2. Using the expression for buffer overflow probabilities mentioned above, we show that
an upper bound on the buffer overflow probability translates to an upper bound on the
utilization or load, which can then be used as constraints in an appropriately posed
convex minimization problem under convex constraints. This is a reformulation of the
proportionally fair end-to-end rate allocation problem. A distributed dual approach is
then used to solve this convex minimization problem using an appropriate
Lagrangianfunction. The dual problem is solved using a projected gradient method.
3. Finally, after making some observations about the distributed implementation of the
above-mentioned dual scheme, we present simulation results showing the satisfactory
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3. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
performance of our proposed algorithm in terms of fairness and QoS.
The rest of the paper is organized as follows. Section 2 presents the network model that is used in
the rest of the paper. We then formulate the rate control problem as a convex optimization
instance with bounds on the buffer overflow probabilities at each node. In section 3, we discuss
the dual-based solution approach and present a distributed implementation to achieve flow-based
proportional fairness. The convergence of this algorithm to the unique global optimum is
established. Section 4 contains the details of the experimental results verifying the optimality of
the proposed scheme. Conclusions are provided in section 5.
2. PROBLEM FORMULATION
2.1. Wireless Network Model
We assume the following:
1. Time is divided into slots of equal duration.
2. A successful transmission in a time-slot implies collision free data transmission in that slot.
3. The transmitting nodes always have data packets to transmit (i.e. we do not consider the
arrival rates of packets for different flows, and assume that all flows have packets to
transmit at all times).
4. Nodes cannot transmit and receive packets at the same time.
5. The receipt of more than one packet within the same time-slot will result in a collision.
6. Nodes in the network have a buffer of fixed size assigned to each flow that is routed
through it.
7. We also assume there is a unique route for each flow within the network (which would be
the case if we used DSDV [17] as the routing protocol, for example).
Additionally, we only consider unicast flows for our derivations.
An ad-hoc wireless network carrying a collection of flows, is represented as an undirected graph
G = (V, E) , where V represents the set of nodes, and E ⊆ V ×V is a symmetric relationship (i.e.
(i, j) ∈ E ⇔ ( j, i) ∈ E ), that represents the set of bidirectional links. We assume all links of the
network have the same capacity, which is normalized to unity. The 1-hop neighbourhood of node
i ∈ V is represented by the symbol N(i) . When a node icommunicates with a node j ∈ N(i) , we
can represent it as an appropriate orientation of the link (i, j) in E, where i is the origin and j is the
terminus. The context in which (i, j) ∈ E is used should indicate if it is to be interpreted as a
directed edge with i as origin and j as terminus. The set of flows, using a link (i, j) ∈ E with i( j)
as origin (terminus), is denoted by F (i, j).
When node i intends to transmit data to node j ∈ N(i) for the l-th flow ( l ∈ F (i, j) ), it
wouldtransmit data in the appropriate time-slot with probability pi,j,l. Pi,j =
theprobability that node i transmits data to node j, and Pi =
∑
j∈V
∑
l∈ F (i,j)
pi, j,l , denotes
Pi, j , denotes the probability that
node i will be transmitting to some node in its 1-hop neighbourhood for some flow. The
probabilities pi,j,l’s should be chosen such that Pi is not greater than unity for any node i ∈ V .
2.2. Link Success Probability Expression
The probability of successful data transmission over link (i, j)
E for flow l
F (i, j), denotedby
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4. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
Si,j,l, is given by the expression
po, p,q
Si, j,l = pi, j,l 1−
p j,m,n ∏ 1−
∑
∑
( j,m)∈E,n∈ F ( j,m)
o∈N ( j )−{i} (o, p)∈E,q∈ F (o, p)
(1)
This is also the rate or the attainable throughput of flow l over link (i, j).
2.3. Problem Statement
Consider an ad-hoc wireless network where there are r flows in the network. Each flow has a
utility function associated with it, whose value is determined by the logarithm of the flow rate.
The objective is to maximize the sum of the logarithms of the flow-rates under the operational
constraints outlined below. We denote the logarithm of the rate of the l-th flow as fl. The end-toend proportionally fair flow control problem can be stated as
max ∑ fl
pi, j,l
(2)
l
where(i, j) E and l {1, 2, . . . , r}, subject to additional constraints.
Let us assume that the l-th flow (1 ≤ l ≤ r) spans over kl links. We use the notation 〈l, q〉 ∈ E to
denote the l-th-flow’s q-th-link, where is
is indexed in ascending order starting
from the source and terminating at the destination. Thus, 〈l, q〉 = (i, j) implies the l-th-flow’s q-thlink from the source has i as the source node and j as the destination node. If 〈l, q〉 = (i, j) ∈ E
then we use the notation Sl,q to denote Si,j,l. The logarithm of the rate of l-th flow over link 〈l, q〉 is
represented as fl,q.
Let p = (pl,q ,1 ≤ l ≤ r,1 ≤ q ≤ kl , 〈l, q〉 ∈ E) bethevectorofaccessprobabilitiesofallthe
∧
(
)
flowsovereachlinkinthenetworkand f = fl,q ,1 ≤ l ≤ r,1 ≤ q ≤ kl , 〈l, q〉 ∈ E thevectorof
the
logarithm of link rates of all flows.
In the case of multi-hop wireless networks, the rate of any flow is the same as the rate of the
bottleneck link in that flow. The logarithm of the rate of the l-thflow is min{fl,q : 1 ≤ q ≤
kl}.Hence, the problem can be stated as max
pl,q
∑ min { f
l,q
,1 ≤ q ≤ kl } , subject to capacity
l
constraints,and additional constraints on the buffer overflow probabilities which is addressed in
the nextsubsection.
2.4. Buffer Overflow Probability of a Tandem of Discrete-Time Queues
The results in reference [18] can be paraphrased as follows – for a discrete-time queue of capacity
M, with a packet arrival probability pa, and a probability pd (pd>pa) of a packet departure from a
non-empty buffer, the probability of seeing i-many packets at any time-instant in the buffer in
steady state is given by the expression
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5. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
p
1− a
i
pd pa
M +1
pa pd
1−
pd
(3)
Using the time-reversibility of the underlying Markov-chain, and the mutual independence of the
simultaneous states of the buffers, reference [18] also establishes that the joint stationary state
probability of a tandem of discrete-time queues is the product of the distributions of each queue
taken independently with an arrival probability of pa, which is the probability of packet arrival
into the first queue. This is essentially the discrete-time analogue of Jackson’s result [19]
involving tandems of M/M/1 queues. The key points of divergence between reference [18] and
the present paper are presented below.
It should be noted that unlike the model assumed in reference [18], where arrival and departure
events are permitted to occur concurrently, interference constraints in wireless networks do not
permit the occurrence of certain simultaneous events. For instance, as a node cannot transmit and
receive information at the same time, the simultaneous occurrence of an arrival and a departure
from the discrete-time queue at the node cannot be permitted. Secondary interference constraints
place additional restrictions on the set of simultaneous events that can occur among neighbouring
nodes. Even when there are no restrictions on simultaneous events, reference [20] notes that it is
cumbersome to use balance equations to arrive at an appropriate expression for the joint
stationary probability for tandems of discrete-time queues. For situations where there are
restrictions on the nature of concurrent events that can occur in a tandem of queues, such as those
that model wireless networks, the joint stationary state probability of a tandem of discrete-time
queues is not guaranteed to have the product-form of reference [18]. This notwithstanding, it is
possible to characterize the marginal probability distribution of each queue in the tandem.
We first note that the analysis of reference [18] (cf. equations 1, 2 and the subsequent discussion
of time-reversibility) applies mutatis mutandis to the case when utmost one packet is permitted to
arrive, or depart from a single discrete-time queue of size M, along with the restriction that a
simultaneous arrival and departure of a packet from the queue is not permitted. The probability of
seeing i-many packets in the buffer at any time-instant in this restricted discrete-time queue is
also given by equation 3. The probability of the queue of size M is non-empty is given by the
expression
p
1− a
pd pa
M +1
pa pd
1−
pd
M
and since the probability of a packet departure from a non-empty queue is pd, the probability of a
packet-departure from the discrete-time queue is given by
p
1− a
pd pa
× pd < pa .
M +1
pa pd
1−
pd
M
It is not hard to see that if M = ∞, then the probability of a packet-departure from the discrete5
6. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
time queue is exactly equal to the probability of packet-arrival into the queue. For bounded
queues (M< ∞) the output process of the queue is geometrically distributed with a parameter that
is no greater than the input parameter pa. Additionally, there can be no more than M-many
consecutive departures, or, M-many consecutive arrivals to the discrete-time queue due to the
bound on the buffer-size. We assume packets that arrive into a full-queue get dropped. This
observation holds for a tandem of discrete-time queues. That is, the output process of each queue
is geometrically distributed with a parameter that is no greater than that of the input to the first
queue (i.e. pa). This observation is used in establishing a bound on the buffer-overflow
probabilities at each queue in a tandem of discrete-time queues in the following theorem.
Theorem 1.1: Consider a tandem of n discrete-time queues, each with buffer-size M, whereat any
discrete-time instant the probability of a packet-arrival into the first queue is pa, andthe
probability of a packet-departure from the i-th, non-empty queue is pdi, (i = 1, 2, …, n). If
pd j = min {pdi } , and
i=1, ,n
M
pa
<
, then, the probability of seeing M packets in the i-th queue (i=
pd j M +1
1, …,n) is no greater than
1− pa
M
pd j pa
M +1
pa pd j
1−
pd j
1− ρ M
pa
, we first note that the expression
ρ , increases
M +1
pd j
1− ρ
M
. Let pai be the probability of a packet arrival into the
monotonically with respect to ρ if ρ ≤
M +1
p
M
i-th queue, weknowpai≤pa.If ρi = ai ,sincepdi≥pdj,itfollowsthat ρi ≤ ρ <
. Theobservation
pd i
M +1
Proof:
Suppose ρ =
follows directly from the monotonicity property mentioned above.
A direct consequence of theorem 1.1 is that if we are able to pick a pa such that
pa β
<
pd j 1+ β
1/M
,
then the buffer overflow probability at the i-th queue in the tandem of discrete-time queues will
be no higher than β at all queues. In the next section, this observation is used in a convex
programming solution to the problem of enforcing proportional fairness in the presence of
constraints on the buffer overflow probabilities.
2.5. Problem Formulation with Buffer Overflow and Capacity Constraints
Let us assume the loss rate bounds for the l-thflow translates to each node along the
flowsustaining a traffic intensity (ratio of arrival probability and departure probability at a node)
p
nomore than ρl = a .
p
dj
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7. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
Also, each link-rate in the network cannot exceed the capacity of that link given by (1). Since the
logarithmic function is strictly increasing, each link constraint can be re-written as
fl,q ≤ log(S l,q )
(5)
Each link constraint (5) forms a convex set over (fl,q, p). We also assume that there is a minimum
achievable data-rate for each flow, i.e., ∃ε, s.t. ε ≤ fl,q , ∀l, q(1 ≤ l ≤ r,1 ≤ q ≤ kl ) . Also, we
assume that all the flows in the network have a maximum achievable data-rate i.e.,
∃δ, s.t. fl,q ≤ δ, ∀l, q (1 ≤ l ≤ r,1 ≤ q ≤ kl ),(toaccommodatenetworkcontrol trafficlike routing
messages, for example). We define the feasible set of access probabilities as,
P% = p :
pl,q ≤ 1, eε ≤ pl,q ≤ eδ , (i, j) ∈ E, l ∈ F (i, j).
{l:〈l,q〉=(i, j ), j∈N (i)}
∑
Also, we define the QoS region as a set of vectors as defined by
ˆ
G = {f : ε ≤ fl,1, fl,q ≤ δ, fl,1 ≤ fl,q + δl , 2 ≤ q ≤ kl },
whereδl = log ρl. The overall optimization problem can now be stated as:
V : max : ∑ min { fl,q :1 ≤ q ≤ kl },
(6)
l
fl,q ≤ log(Sl,q ), ∀〈l, q〉 ∈ E,
% ˆ
p ∈ P, f ∈ G.
From the constraint imposed by the QoS region, we observe that for any feasible solution to V,
the first link will always have the lowest rate and hence it will be the bottleneck. Therefore for
any feasible solution, the rate of any flow l, is same as fl,1. We replace fl,1 by fl, and define the
%
feasiblesetofflowratesas F = { f : ε ≤ fl ≤ δ, ∀l }, where,f=(fl, 1≤l≤r),wecanrewriteV as the
following convex optimization problem,
U : min ∑ − fl ,
(7)
l
fl ≤ log(Sl,1 ), ∀〈l,1〉 ∈ E,
fl ≤ log(Sl,q ) + δl , ∀〈l, q〉 ∈ E, 2 ≤ q ≤ kl ,
% ˆ
%
p ∈ P, f ∈ F.
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8. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
3. SOLUTION APPROACH
3.1. Dual-based Algorithm
We can write the Lagrangian function for the problem stated in (7) as,
L(f,p,λ ) = ∑ − fl + ∑ λl,1 ( fl − log(Sl,1 )) +
l
∑
λl,q ( fl − log(Sl,q ) − δl ).
(8)
l,q(2≤q≤kl )
l,1
Let us denote Λ = (λl,q : ∀l,1 ≤ q ≤ kl ) as a vector of Lagrange multipliers. As the Slater
constraint qualification is satisfied by the convex program given by (7), convex duality implies
that at the optimum Λ*, the corresponding f, p are the solutions to the primal problem [21]. The
dual problem can be solved using the gradient projection method similar to the scheme used in
[22]. Note that the Lagrangian is separable in terms of the probabilities p and the logarithm of the
rates f. The dual function can be stated as:
Q(Λ) = inf % L(f, p, Λ).
%
f∈ F,p∈P
(9)
The following proposition is significant for obtaining the distributed solution for the non-linear
program given by (7).
Proposition 2.1: For a given Λ(λl,q ≠ 0, ∀〈l, q〉 ∈ E), the solution to
by:
λl,q
pl,q = max min
∑ λy,z + ∑ λy,z + ∑
〈y,z〉=(k,i),k∈N (i)
v∈N (i)
〈y,z〉=(i,k),k∈N (i)
inf L( f, p, Λ) is given
%
%
f ∈ F,p∈P
,eδ ,eε , (10)
∑ λy,z
〈y,z〉=(k,v),k∈N (v)−{i}
and,
ε if ∑ λl,q ≥ 1
q
fl =
δl if ∑ λl,q < 1
q
(11)
Proof: Since the Lagrangian is convex with respect to p, the unconstrained value of p thatyields
the infimum of the Lagrangian is obtained by taking its derivative with respect to p and equating
it to zero. This results in the expression involving λ-terms in equation 10.
The denominator of this expression is essentially the sum of three terms. The first term is the sum
of the Lagrange multipliers associated with all outgoing flows from node i. The second is the sum
of the Lagrange multipliers associated with all incoming flows to node i. Finally, the third term is
the sum of the Lagrange multipliers associated with all incoming flows to nodes in the one-hop
neighborhood of node i (excluding the flows incoming from node i). It is not hard to show that
this expression satisfies the constraint 0 ≤ pl,q ≤ 1 and 0 ≤ Pi ≤ 1.
The remaining terms, and the structure of equation 10, are a direct consequence of the upper and
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9. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
lower-bounds on pl,q (eε ≤ pl,q ≤ eδ).
Also, for any l, the coefficient of fl in the Lagrangian, is given by (−1+
∑λ
l,q
). When
q
∑λ
l,q
≠ 1, the infimum of Lagrangian with respect to fl is either the lower or the upper bound of
q
fl, depending on the sign of its coefficient, which gives (11). When
∑λ
l,q
= 1, fl can take
q
anyvalue between [ε, δ].
The dual problem
maximize: Q(Λ)
(12)
subject to: Λ ∈ [η,∞) ×[η,∞) ×
× [η,∞)
whereη is a small number close (but not equal) to zero, can now be solved using the subgradient
projection method, where the Lagrange multipliers are adjusted in the direction of thesubgradient
+
n+1
l,q
λ
∂Q(Λ n )
n
= λl,q + α n
∂λl,q
+
where z〈l,q〉 = max{η, z〈l,q〉 } and
(13)
∂x
denotes the subgradient of x with respect to y. The
∂y
variableαn is the step size at the nthiteration that can either be a constant, or, diminishing step
sizethat satisfies the requirements
∞
lim α = 0, ∑α n = ∞,
n
n→∞
n=1
and the subgradient is given by,
∂Q(Λ n )
n
= ( fl n − log(Sl,1 )),
∂λl,1
(14)
∂Q(Λ n )
n
= ( fl n − log(Sl,q ) − δl ), 2 ≤ q ≤ kl ,
∂λl,q
(15)
wherefl and λl,q are obtained from equations (10) and (11).
3.2. Convergence of the Proposed Scheme
%
Since p ∈ P, the norm of subgradients of the dual function given by (9), is bounded. Let Λ*be
n
ˆ
the solution to (12) for η = 0. Also let Λη be the global maximum of (12) for η > 0.Let {Λη } be
the sequence generated by the subgradient method given by (13) for η > 0.
Lemma
2.2:
n
Let g(Q(Λη )) ≤ G, ∀n ≥ 0 .
2
For
every
η
>
0,
ˆ
∃Λ η ,
such
that
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10. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
ˆ
Q(Λ * ) − Q(Λη ) ≤ Gη .
2
The proof follows directly from the concavity of the dual function, and the property of the
subgradients [23].
Theorem 2.3: For every η > 0, every limit point of the sequence of
{Λη } obtained using the
n
diminishing step size, is the global maximum of (12).
Proof: Chapter 2 of reference [23], presents a proof of convergence of approaches that use
subgradient method involving diminishing step sizes, which can easily be extended to projected
subgradientmethod for maximization of concave function over a convex set.
Theorem 2.4: For every η > 0, using the constant step size αn = α, as n → ∞,
ˆ
Q(Λη ) − lim inf(Q(Λη )) ≤
n→∞
n
Gα 2
1
i
, where Λη =
∑ Λη .
2
n +1 i=0
The proof of convergence of projected subgradient method with constant step size,
underassumption of bounded subgradients, is presented in the appendix for completeness.
3.3. Implementation of the Dual-Based Algorithm
The dual-based algorithm for end-to-end proportionally fair rate allocation under buffer overflow
constraints in random access wireless networks can be summarized as follows:
1. Initialize the iteration count n to zero. If 〈l, q〉 = (i, j) for some flow l, node i chooses an
0
0
λl,q such that 0 < λl,q <1 .
n
2. Node ipasses the value of λl,q to the source of the l-thflow. The logarithm of the rates (fl)
initial value of
are then computed by sources using (11) in O(1) time.
3. Every node that the l-thflow is routed through, obtains the value of fl n from the source.
4. After obtaining the
n
λl,q -values from nodes within a 2-hop neighborhood, each node
computes the access probability values (pl,q) according to (10).
n+1
5. Each node increments the value of n and computes λl,q by the gradient projection
algorithmgiven by (13) in O(1) time.
6. Steps 2, 3, 4 and 5 are repeated till an appropriate stopping condition is satisfied (based
on heuristics or some other criteria, see discussion below).
When flows can arrive and depart in the network, constant step size is the preferred optionand in
this case there is no stopping criteria, i.e. the nodes continue to run the optimization algorithm
without termination. The access probabilities are updated periodically and the source of each flow
sets the flow rate as
{
}
min log(Sl,1 ), min (log(Sl,q ) − δl ) ,
2≤q≤kl
(16)
to maintain the flow rates in the QoS region.
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11. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
4. PERFORMANCE EVALUATION
For our simulation comparisons, we consider the example shown in figure 1, from references
[10], [12]. The nodes are labeled from 1 to 6. The interference model is that each node interferes
with the reception at its one-hop neighbors. For example nodes 1 and 3 cause interference at node
2; nodes 6, 5, 2 and 4 cause interference at node 3. Three end-to-end flows, namely,flow1, flow2,
and flow3 are setup in this network. The source, the sinks, and the path of three flows are shown in
table I.
We suppose each flow can tolerate a loss of 45 in every 100,000 packets. Additionally, we
suppose each node has a buffer that can store 50 packets for each flow that is routed through it.
Fig. 1.An ad-hoc wireless network.
TABLE I: Path of the flows and observed flow rates in a MATLAB simulation of the network
shown in figure 1.
This translates to a value of ρ = 0.86. For ρ1 = ρ2 = ρ3 = 0.86, the globally optimal solutions to the
problem defined in (7) was computed using the fmincon function in MATLAB. This solution and
the solutions given by the dual-based algorithm are presented in table II. More detailed
experimentation results can be found in [24], which has been excluded from this paper due to
page limitations.
We have used two approaches to the dual-based algorithm outlined earlier. In the first approach
we use a constant step size αn = 5 × 10−4 (cf. (13)), and the logarithm of the minimal achievable
rate, ε was set to be -10. Figure 2(a) shows how the flow rates (cf. (16)), converge when the dualbased algorithm with fixed step size is used.
The second approach involves the use diminishing step size. In this case the step size at the nth
iteration αn = 1/n. The value of ε is set to be -10. Figure 2(b) illustrates the convergence ofthe
flow rates (cf. (16)), when the dual-based algorithm with diminishing step sizes is used.
If ρ1 = ρ2 = ρ3 = 1, we get the optimal solution of U* = −7.4897 using MATLAB’s fmincon
function. This is higher than when ρ1 = ρ2 = ρ3 = 0.86, but the buffer overflow will be
significantly higher. To demonstrate this, we simulated the network in figure 1 in
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12. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
MATLAB,using access probabilities obtained for ρ1 = ρ2 = ρ3 = 1 and ρ1 = ρ2 = ρ3 = 0.86, and
ran the simulation for a duration of 5×104 time slots, where each node in the network has infinite
length buffers (i.e. no packets are dropped in the simulation). For a random instance of the
simulation, we plot the queue-lengths as a function of time, for flow 1 at node 5. In the plots, unit
of time is a single time-slot of fixed duration. The flow rates observed for ρ1 = ρ2 = ρ3 = 0.86are
presented in table I.
Figure 3 demonstrates the queueing performance of our algorithm at node 5. Case I is the plot of
queue-length as a function of time when we use the optimal access probabilities without
considering buffer overflow constraints i.e. ρ1 = ρ2 = ρ3 = 1. Case II shows how the queue- length
varies as a function of time, when the optimal access probabilities obtained by setting ρ1 = ρ2 = ρ3
= 0.86is used. We can observe from the plots that in case I, the queue is unstable, whereas, case II
shows the queue at node 5 is stable. If a buffer size of 50 was used, then the fraction of packets
transmitted that are lost, in case I will be much higher than as compared to case II.
TABLE II:
The Optimal Results and the Solution given by the Distributed Algorithm
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13. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
Fig. 2. The convergence of flow rates when dual-based algorithm is used.
Fig. 3. The queue-length at Node 5.
5. CONCLUSION
In this paper, we proposed a distributed scheme for providing end-to-end proportionally fair flow
rates in a slotted-time, multi-hop, random access network with a general network topology, with
bounds on the buffer overflow probabilities at each node. After noting that each flow in the
network can be viewed as a tandem of discrete-time queues, we converted the constraints on
buffer overflow probabilities into appropriate constraints on the link rates, which permitted the
reformulation of the original problem into an appropriately posed convex minimization problem
under convex constraints. We solved this problem using an appropriately constructed Lagrange
function, and discuss its convergence properties. After presenting aspects of distributed
implementation of this dual-based approach, we verified the correctness of the approach using an
example from the literature.
13
14. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
APPENDIX A: PROOF OF CONVERGENCE OF PROJECTED SUBGRADIENT
METHODS WITH CONSTANT STEP SIZE
Suppose
is a concave function defined over a convex set C, having a non-emptyset
of maximum points M*. To maximize f, the projected subgradient method uses the iterationxk+1 =
[xk + hk+1g(xk)]+, where xk is the k-th iterate, g(xk)is the subgradient of f at xk andhk+1is the step
size, and for constant step size we have hk = h, ∀k . We assume that norm ofsubgradients of f is
k
bounded and therefore, g(xk ) 2 ≤ G, ∀k . Also, we define at the k-thiterate, x =
Theorem A.1: For any x*
1
∑ xi .
k +1 i=0
ˆ
ˆ
M*, as k → ∞ one can find a x , such that either f ( x) = lim f (xk ) or
k→∞
ˆ
ˆ
ˆ
f ( x) = lim inf( f ( x)) and f (x * ) − f ( x) ≤ G 2 h / 2 .
k→∞
ˆ
Proof: If g(xk* ) = 0 for some k*, then f (xk ) = f (x * ), ∀k ≥ k * and we may take x = x * . If
+
g(xk ) ≠ 0, ∀k , then xk+1 = [ xk + hg(xk )] . Let zk+1 = xk + hk+1g(xk ) (without projection).Observe
that
xk+1 − x * ≤ zk+1 − x * .
2
(17)
2
This is true as when we project a point onto C, we move closer to every point in C. Now,
2
2
2
2
2
2
2
zk+1 − x * = xk + hg(xk ) − x * = xk − x * + 2hg(xk )T (xk − x * ) + h 2 g(xk ) 2 .
From (17), we have
2
2
2
2
2
2
xk+1 − x * ≤ xk − x * + 2hg(xk )T (xk − x * ) + h 2 g(xk )
(18)
From the definition of the subgradients for concave functions we have,
f (x * ) ≤ f (xk ) + g(xk )T (x * − xk ).
(19)
From (18) and (19), we get the following inequality
2
2
2
2
2
xk+1 − x * ≤ xk − x * + 2h( f (xk ) − f (x * )) + h 2 g(xk ) 2 .
(20)
Recursively from (20), we get
xk+1 − x
* 2
2
≤ x0 − x
* 2
2
k
+ 2h∑ ( f (xi ) − f (x )) + h
*
i=0
Using xk+1 − x *
2
2
k
2
∑ g(x )
i
2
2
.
(21)
i=0
≥ 0 , we have,
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15. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 5, October 2013
k
2h∑ ( f (x ) − f (xi )) ≤ x0 − x
*
* 2
2
k
+h
i=0
2
∑ g(x )
i
2
2
.
(22)
i=0
By property of concave functions, we have,
k
∑ f (x )
i
i=0
k +1
≤ f (x ),
(23)
k
where, x =
1
∑ xi. Thus we have,
k +1 i=0
k
∑( f (x ) − f (x )) ≥ (k +1)( f (x ) − f (x )).
*
*
i
i=0
Combining this with (22), we get the inequality
*
2h(k +1)( f (x ) − f (x )) ≤ x0 − x
* 2
2
k
+h
2
∑ g(x )
2
.
i
i=0
(24)
2
Given that ||g(xi)|| ≤ G, for all i, we have,
2
*
f (x ) − f (x ) ≤
x0 − x * + h 2 (k +1)G 2
2
2h(k +1)
.
(25)
Taking the limit as k → ∞, we get,
f (x * ) − lim inf( f (x )) ≤ G 2 h / 2.
(26)
k→∞
Hence the result.
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