On Opportunistic Cooperative Medium Access Control Protocols for Single-hop and Multi-hop IEEE 802.11 Based Wireless Networks PDF Download

Author: Kumaran Vijayasankar
Publisher:
ISBN:
Category : Computer networks
Languages : en
Pages : 604

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Book Description
Cooperation is then applied to end-to-end multi-hop routes by using a relay if available for each hop along the end-to-end route. Performance improvements in terms of saturated throughput and end-to-end delay are evaluated for static predetermined routes. COBRA MAC is then combined with dynamic routing protocols like AODV and OLSR when a single transmission rate is used. Relay selection and performance improvements obtained under such conditions are then presented. Since, a typical IEEE 802.11 based network has multiple transmission rates, rate selection for the relay becomes important. Hence, heuristics to perform rate selection for relays are presented. Finally, a metric that jointly optimizes the end-to-end route and relay selection in a multi-hop network is proposed. Using analysis and simulations, it is shown that opportunistic cooperation provides noticeable performance improvements when applied to a multi-hop network.

Author: Lakshmi Narasimhan Kannan
Publisher:
ISBN:
Category : Ad hoc networks (Computer networks)
Languages : en
Pages : 468

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Book Description
Wireless transmission medium suffers from channel impairments like fading and path loss leading to performance degradations in terms of reduced throughput and increased latency. Medium access control protocols designed for wireless networking today provide multiple retransmissions as a way to account for frame losses caused by the channel. By retransmitting in the same channel, effectiveness of retransmissions can be reduced due to prolonged periods of channel impairments like obstacles in the line of sight of communication. Spatial diversity provides statistically different channels that can compensate for frame losses. Wireless medium being broadcast in nature paves way to achieve spatial diversity by asking neighboring nodes that can overhear transmissions to retransmit the frames. This procedure is termed cooperation. The nodes that help in successful communication between two other nodes are called relays. Medium access control protocols that are designed to account for cooperation are called cooperative medium access control protocols. This thesis presents one such cooperative protocol. The cooperative protocol presented in this thesis is unique in that the relays are opportunistic in nature. Relays here only help the source that is transmitting frames to a destination when a transmission failure occurs. A metric to find a suitable relay is presented and heurisitic algorithms to find transmission rate pairs for links in the cooperative setup are also presented. The thesis also shows that the cooperative protocol proposed can also be used in multi-hop networks. A cross layer routing metric to jointly perform route and relay selection in multi-hop networks is also presented. Simulation and analytical studies were carried out and results are presented in this thesis comparing the performance of the cooperative protocol presented here and the standard protocol it is based on. Performance improvements in terms of throughput and latency are brought about by using opportunistic cooperation. The performance improvements depend on careful selection of relays and transmission rates used for the links in the cooperative setup. The gains perceived in single hop networks were also seen in multi-hop networks but the magnitude of gains in multi-hop scenarios were dependent on network topology.

Author: Soufiene Djahel
Publisher: GRIN Verlag
ISBN: 3656041024
Category : Computers
Languages : en
Pages : 170

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Book Description
Doctoral Thesis / Dissertation from the year 2011 in the subject Computer Science - Internet, New Technologies, Lille 1 University (Laboratoire d'Informatique Fondamentale de Lille), course: Security in Wireless Multi-hop Networks, language: English, abstract: While the rapid proliferation of mobile devices along with the tremendous growth of various applications using wireless multi-hop networks have significantly facilitate our human life, securing and ensuring high quality services of these networks are still a primary concern. In particular, anomalous protocol operation in wireless multi-hop networks has recently received considerable attention in the research community. These relevant security issues are fundamentally different from those of wireline networks due to the special characteristics of wireless multi-hop networks, such as the limited energy resources and the lack of centralized control. These issues are extremely hard to cope with due to the absence of trust relationships between the nodes. To enhance security in wireless multi-hop networks, this dissertation addresses both MAC and routing layers misbehaviors issues, with main focuses on thwarting black hole attack in proactive routing protocols like OLSR, and greedy behavior in IEEE 802.11 MAC protocol. Our contributions are briefly summarized as follows. As for black hole attack, we analyze two types of attack scenarios: one is launched at routing layer, and the other is cross layer. We then provide comprehensive analysis on the consequences of this attack and propose effective countermeasures. As for MAC layer misbehavior, we particularly study the adaptive greedy behavior in the context of Wireless Mesh Networks (WMNs) and propose FLSAC (Fuzzy Logic based scheme to Struggle against Adaptive Cheaters) to cope with it. A new characterization of the greedy behavior in Mobile Ad Hoc Networks (MANETs) is also introduced. Finally, we design a new backoff scheme to quickly detect the greedy nodes that do not comply with IEEE 802.11 MAC protocol, together with a reaction scheme that encourages the greedy nodes to become honest rather than punishing them.

Author: Savo Glisic
Publisher: John Wiley & Sons
ISBN: 9780470745731
Category : Technology & Engineering
Languages : en
Pages : 892

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Book Description
With 40% new material the new edition of Advanced Wireless Networks provides a comprehensive representation of the key issues in 4G wireless networks. Focussing on cognitive, cooperative and opportunistic paradigms to provide further increase in network efficiency, the book explores and addresses issues in wireless internet, mobile cellular and WLAN, as well as sensor, ad hoc, bio-inspired, active and cognitive networks. It examines the problem of cross-layer optimisation and network information theory as well as adaptability and reconfigurability in wireless networks. This book is an integral description of future wireless networks and the interconnection between their elements. The information is presented in a logical order within each chapter making it ideal for all levels of reader including researchers involved in modelling and analysis of future networks as well as engineers working in the area. Each chapter starts with introductory material and gradually includes more sophisticated models and mathematical tools concluding with a comprehensive list of references. Fully updated throughout with five new chapters on Opportunistic Communications; Relaying and Mesh Networks; Topology Control; Network Optimization; and Cognitive Radio Resource Management Unifies the latest research on cognitive, cooperative and opportunistic paradigms in wireless communications Provides efficient analytical tools for network analysis Discusses security issues, an essential element of working with wireless networks Supports advanced university and training courses in the field Companion website containing extra appendix on Queuing theory

Author:
Publisher:
ISBN: 9781109249194
Category : Wireless communication systems
Languages : en
Pages :

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Book Description
Wireless networks differ from their wired counterparts in that communication between nodes takes place over a "link" using an RF, acoustic, optical, or other signal transmitted through the air or water instead of, as their name implies, a wire. This difference changes the frequency of transmission errors from extremely rare to almost constant, and introduces inter-node interference as a significant problem. Wireless networks are typically more limited than wired networks in terms of bandwidth, computational ability, power, and centralized management. Efficient handling of transmission errors and reducing interference are thus vital in maximizing network performance. This dissertation addresses two separate aspects of wireless networks with a common theme of low overhead, local coordination between nodes, and often using inferences or even informed guesses to make decisions. To address the problem of transmission errors, we study two medium access control (MAC) protocols that use minimal-overhead, local coordination schemes to allow cooperation between neighboring nodes: one with and one without a cooperation-enabled physical layer. To address the problem of interference, we study two closely related MAC protocols that use local coordination between neighboring nodes to build an interference-free transmission schedule, for (1) supporting latency-sensitive applications over long routes in mesh networks, and (2) increasing channel utilization and energy efficiency in underwater acoustic networks. Our first work focuses on mobile ad hoc networks where if any link in a route fails, multiple fruitless attempts are currently made by most of the existing MAC protocols to use the failed link before reporting failure to the routing layer and/or attempting local recovery. The high frequency of link errors between mobile nodes requires rapid recovery to provide acceptable performance. We design CIFLER, a cross-layer approach which uses enhanced channel reservation messages to allow alternate nodes to immediately elect themselves using only inferred neighbor information. This self-election avoids reliance on individual links, and uses diversity to minimize the impact frequent link errors have on delay, energy efficiency, and the functioning of upper layer protocols. We show via both analysis and simulation that CIFLER provides better performance in typical MANET scenarios. Unlike other local recovery schemes, CIFLER uses only a minor modification to IEEE 802.11 DCF, does not suffer from duplicated messages, allows neighboring nodes to almost immediately learn the information needed to assist in the recovery of existing routes, and does not require additional hardware, delays, or control messages. Our second work applies the same concept of inferred neighbor information to cooperative communications, where the signals of simultaneous transmissions by multiple nodes constructively combine in the wireless medium. Studies on the physical layer capabilities (via either information theory or numerical analysis) have shown the significant performance improvements of cooperative communications. However, these studies ignore both the overheads incurred in real implementations of the cooperative techniques at the physical layer and their interactions with higher layer protocols in a networking context. We implement a path-centric MAC protocol that uses minimal control messages to reserve a multi-hop path between source and destination nodes, and perform coordination between relay nodes. We then realistically study the performance of cooperation in networking scenarios by taking into account overheads incurred at the physical, MAC, and network layers. Simulations demonstrate that significant performance improvement can be achieved by employing cooperation. We also demonstrate the overheads which challenge the effectiveness of such schemes in real networks. Our third work deals with the issue of interference and transmission scheduling in mesh networks, where links are generally reliable if no interference is present. In current wireless networks, access to the shared wireless medium is controlled via either a TDMA- or a CSMA-based scheme. While usable in single-hop networks, these techniques are often far from optimal, and result in significant per-hop and per-packet delay and jitter, making multi-hop wireless mesh networks a particularly harsh environment for real-time, isochronous applications such as VoIP. We present a new time-based MAC protocol, FLASHR, for wireless mesh networks carrying delay-sensitive isochronous traffic. In our scheme, nodes use simple local coordination mechanisms to form adaptive transmission schedules which attain the desired quality of service. Simulations show that our scheme achieves near-optimal capacity, minimal jitter, and a weaker correlation between route length and end-to-end delay. Our final work adapts the FLASHR MAC protocol for use in underwater acoustic networks. A time-based MAC has potential advantages over FDMA and CDMA approaches in terms of hardware simplicity, energy efficiency, and delay. Unfortunately, the channel utilization of existing TDMA and CSMA acoustic MAC protocols is generally low due to the long propagation delays of acoustic signals. We argue that several ideas taken from RF protocols, including exclusive channel access, are either unnecessary in acoustic networks or must be redefined. We design UW-FLASHR, a modification to FLASHR which uses additional local control messages to create a time-based MAC protocol for acoustic networks which does not require centralized control, tight clock synchronization, or accurate propagation delay estimation. Our results show that UWFLASHR achieves higher channel utilization than the maximum utilization possible with existing time-based exclusive-access MAC protocols, particularly when the ratio of propagation delay to transmission delay is high, or data payloads are small.

Author: Kai Zeng
Publisher: John Wiley & Sons
ISBN: 1119974291
Category : Technology & Engineering
Languages : en
Pages : 211

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Book Description
This book provides an introduction to opportunistic routing an emerging technology designed to improve the packet forwarding reliability, network capacity and energy efficiency of multihop wireless networks This book presents a comprehensive background to the technological challenges lying behind opportunistic routing. The authors cover many fundamental research issues for this new concept, including the basic principles, performance limit and performance improvement of opportunistic routing compared to traditional routing, energy efficiency and distributed opportunistic routing protocol design, geographic opportunistic routing, opportunistic broadcasting, and security issues associated with opportunistic routing, etc. Furthermore, the authors discuss technologies such as multi-rate, multi-channel, multi-radio wireless communications, energy detection, channel measurement, etc. The book brings together all the new results on this topic in a systematic, coherent and unified presentation and provides a much needed comprehensive introduction to this topic. Key Features: Addresses opportunistic routing, an emerging technology designed to improve the packet forwarding reliability, network capacity and energy efficiency of multihop wireless networks Discusses the technological challenges lying behind this new technology, and covers a wide range of practical implementation issues Explores many fundamental research issues for this new concept, including the basic principles of opportunistic routing, performance limits and performance improvement, and compares them to traditional routing (e.g. energy efficiency and distributed opportunistic routing protocol design, broadcasting, and security issues) Covers technologies such as multi-rate, multi-channel, multi-radio wireless communications, energy detection, channel measurement, etc. This book provides an invaluable reference for researchers working in the field of wireless networks and wireless communications, and Wireless professionals. Graduate students will also find this book of interest.

Author: Divya ChanneGowda
Publisher:
ISBN:
Category : Computer science
Languages : en
Pages : 352

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Book Description
We investigate the use of cooperative communications in the context of ad hoc IEEE 802.11b to combat radio signal degradations. The performance gain of both an existing cooperative protocol and the newly proposed cooperative protocol is discussed. It is quantitatively shown how much the two cooperative protocols increase throughput, lower delivery latency, and extend transmission span, when compared to the conventional IEEE 802.11b protocol.

Author: Wei Song
Publisher: Springer
ISBN: 3319477269
Category : Technology & Engineering
Languages : en
Pages : 135

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Book Description
This book focuses on the design and analysis of protocols for cooperative wireless networks, especially at the medium access control (MAC) layer and for crosslayer design between the MAC layer and the physical layer. It highlights two main points that are often neglected in other books: energy-efficiency and spatial random distribution of wireless devices. Effective methods in stochastic geometry for the design and analysis of wireless networks are also explored. After providing a comprehensive review of existing studies in the literature, the authors point out the challenges that are worth further investigation. Then, they introduce several novel solutions for cooperative wireless network protocols that reduce energy consumption and address spatial random distribution of wireless nodes. For each solution, the book offers a clear system model and problem formulation, details of the proposed cooperative schemes, comprehensive performance analysis, and extensive numerical and simulation results that validate the analysis and examine the performance under various conditions. The last section of this book reveals several potential directions for the research on cooperative wireless networks that deserve future exploration. Researchers, professionals, engineers, and consultants in wireless communication and mobile networks will find this book valuable. It is also helpful for technical staff in mobile network operations, wireless equipment manufacturers, wireless communication standardization bodies, and governmental regulation agencies.

Author: Balvinder Kaur Thind
Publisher:
ISBN:
Category : Computer network protocols
Languages : en
Pages :

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Author: Yuhan Moon
Publisher:
ISBN:
Category : Ad hoc networks (Computer networks)
Languages : en
Pages : 151

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Book Description
Today, many wireless networks are single-channel systems. However, as the interest in wireless services increases, the contention by nodes to occupy the medium is more intense and interference worsens. One direction with the potential to increase system throughput is multi-channel systems. Multi-channel systems have been shown to reduce collisions and increase concurrency thus producing better bandwidth usage. However, the well-known hidden- and exposed-terminal problems inherited from single-channel systems remain, and a new channel selection problem is introduced. In this dissertation, Multi-channel medium access control (MAC) protocols are proposed for mobile ad hoc networks (MANETs) for nodes equipped with a single half-duplex transceiver, using more sophisticated physical layer technologies. These include code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), and diversity. CDMA increases channel reuse, while OFDMA enables communication by multiple users in parallel. There is a challenge to using each technology in MANETs, where there is no fixed infrastructure or centralized control. CDMA suffers from the near-far problem, while OFDMA requires channel synchronization to decode the signal. As a result CDMA and OFDMA are not yet widely used. Cooperative (diversity) mechanisms provide vital information to facilitate communication set-up between source-destination node pairs and help overcome limitations of physical layer technologies in MANETs. In this dissertation, the Cooperative CDMA-based Multi-channel MAC (CCM-MAC) protocol uses CDMA to enable concurrent transmissions on each channel. The Power-controlled CDMA-based Multi-channel MAC (PCC-MAC) protocol uses transmission power control at each node and mitigates collisions of control packets on the control channel by using different sizes of the spreading factor to have different processing gains for the control signals. The Cooperative Dual-access Multi-channel MAC (CDM-MAC) protocol combines the use of OFDMA and CDMA and minimizes channel interference by a resolvable balanced incomplete block design (BIBD). In each protocol, cooperating nodes help reduce the incidence of the multi-channel hidden- and exposed-terminal and help address the near-far problem of CDMA by supplying information. Simulation results show that each of the proposed protocols achieve significantly better system performance when compared to IEEE 802.11, other multi-channel protocols, and another protocol CDMA-based.