On Cooperative Medium Access Control Protocols for IEEE 802.11 Based Wireless Ad Hoc Networks PDF Download

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

View

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

View

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

View

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.

Author: Fatma Orsun
Publisher:
ISBN:
Category :
Languages : en
Pages : 122

View

Book Description
[Author's abstract] Short term fairness, low delay jitter and high throughput are required to provide differentiated Quality of Service (QoS) levels in wireless ad hoc networks and wireless Local Area Networks (LAN). This thesis presents a study of differentiated service mechanism via Cooperative Medium Access Protocol in wireless LANs. The IEEE 802.11 MAC can provide service differentiation via Point Coordination Function (PCF) by polling or Distributed Coordination Function (DCF) by Static Priority (SP) and Dynamic Priority (DP). The DP and PCF in highly loaded networks and SP in lightly loaded networks perform poorly and can not support QoS levels of wireless LANs efficiently. This thesis proposes a novel and efficient differentiated service mechanism via Cooperative Medium Access Control (C MAC). Proposed mechanism performs very well under both cases, highly loaded and lightly loaded. It protects high priority classes from greedy sources while providing short term fairness within the priority classes and high network goodput. However, it encounters a small amount of additional packet loss and goodput degradation and it requires additional counter, Backoff Increment Counter, and additional knowledge, priority level of the transmitted packet.

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

View

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: Yamen Nasrallah
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
The Intelligent Transportation System (ITS) is a cooperative system that relies on reliable and robust communication schemes among vehicles and between vehicles and their surroundings. The main objective of the ITS is to ensure the safety of vehicle drivers and pedestrians. It provides an efficient and reliable transportation system that enhances traffic management, reduces congestion time, enables smooth traffic re-routing, and avoids economic losses. An essential part of the ITS is the Vehicular Ad hoc Network (VANET). VANET enables the setup of Vehicle-to-Vehicle (V2V) as well as Vehicle-to-Infrastructure (V2I) communication platforms: the two key components in the ITS. The de-facto standard used in wireless V2V and V2I communication applications is the Dedicated Short Range Communication (DSRC). The protocol that defines the specifications for the Medium Access Control (MAC) layer and the physical layer in the DSRC is the IEEE 802.11p protocol. The IEEE 802.11p protocol and its Enhanced Distributed Channel Access (EDCA) mechanism are the main focus of this thesis. Our main objective is to develop new IEEE 802.11p-based protocol for V2V and V2I communication systems, to improve the performance of safety-related applications. These applications are of paramount importance in ITS, because their goal is to decrease the rate of vehicle collisions, and hence reduce the enormous costs associated with them. In fact, large percentage of vehicle collisions can be easily avoided with the exchange of relevant information between vehicles and the Road Side Units (RSUs) installed on the sides of the roads. In this thesis, we propose various enhancements to the IEEE 802.11p protocol to improve its performance by lowering the average end-to-end delay and increasing the average network throughput. We introduce multiple adaptive algorithms to promote the QoS support across all the Access Categories (AC) in IEEE 802.11p. We propose two adaptive backoff algorithms and two algorithms that adaptively change the values of the Arbitrary Inter-Frame Space (AIFS). Then we extend our model to be applied in a large-scale vehicular network. In this context, a multi-layer cluster-based architecture is adopted, and two new distributed time synchronization mechanisms are developed.

Author: Bernhard H. Walke
Publisher: John Wiley & Sons
ISBN: 9780470058794
Category : Technology & Engineering
Languages : en
Pages : 402

View

Book Description
Throughout the next decade, 802 wireless systems will become an integral part of fourth generation (4G) cellular communication systems, where the convergence of wireless and cellular networks will materialize through support of interworking and seamless roaming across dissimilar wireless and cellular radio access technologies. IEEE 802 Wireless Systems clearly describes the leading systems, covering IEEE 802.11 WLAN, IEEE 802.15 WPAN, IEEE 802.16 WMAN systems’ architecture, standards and protocols (including mesh) with an instructive approach allowing individuals unfamiliar with wireless systems to follow and understand these technologies. Ranging from digital radio transmission fundamentals, duplex, multiplexing and switching to medium access control, radio spectrum regulation, coexistence and spectrum sharing, this book also offers new solutions to broadband multi-hop networking for cellular and ad hoc operation. The book Gives a comprehensive overview and performance evaluation of IEEE 802.11, 802.15 and 802.16 Includes a tutorial like introduction to the basics of wireless communication Discusses challenges in mesh/multi-hop relaying networks and provides profound solutions for their realization with 802 Wireless Systems Covers spectrum sharing on different levels and provides solutions for coexistence, cooperation and interworking of 802 Wireless Systems that are following the same or different standards, but share the same spectrum Includes a detailed overview and introduction on cognitive radio and dynamic spectrum access Accompanying website contains simulation software and provides slides of the figures and tables from the book ready for course presentation This book is an essential text for advanced undergraduate students with a basic working knowledge of wireless communication, graduate students and engineers working in the field of wireless communications.

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

View

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: Ian F. Akyildiz
Publisher: Springer Science & Business Media
ISBN: 3540726055
Category : Computers
Languages : en
Pages : 1278

View

Book Description
This book constitutes the refereed proceedings of the 6th International IFIP-TC6 Networking Conference, NETWORKING 2007, held in Atlanta, GA, USA in May 2007. The 99 revised full papers and 30 poster papers were carefully reviewed and selected from 440 submissions. The papers are organized in topical sections on ad hoc and sensor networks: connectivity and coverage, scheduling and resource allocation, mobility and location awareness, routing, and key management; wireless networks: mesh networks, mobility, TCP, MAC performance, as well as scheduling and resource allocation; next generation inte.

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

View

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.