Download or read book Collision Avoidance in Multi Hop Ad Hoc Networks written by and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Collision avoidance is very important in contention-based medium access control protocols for multi-hop ad hoc networks due to the adverse effects of hidden terminals. Four-way sender-initiated schemes are the most popular collision-avoidance schemes to date. Although there has been considerable work on the performance evaluation of these schemes, most analytical work is confined to single-hop ad hoc networks or networks with very few hidden terminals. In this paper, the authors use a simple analytical model to derive the saturation throughput of collision avoidance protocols in multi-hop ad hoc networks with nodes randomly placed according to a two-dimensional Poisson distribution. They show that the sender-initiated collision-avoidance scheme achieves much higher throughput than the idealized carrier sense multiple access (CSMA) scheme with an ideal separate channel for acknowledgments. More importantly, they show that the collision avoidance scheme can accommodate much fewer competing nodes within a region in a network infested with hidden terminals than in a fully-connected network, if reasonable throughput is to be maintained. This shows that the scalability problem of contention-based collision-avoidance protocols looms much earlier than people might expect. Simulation experiments of the popular IEEE 802.11 MAC protocol validate the predictions made in the analysis.
Download or read book Modeling of Collision Avoidance Protocols in Single Channel Multihop Wireless Networks written by and published by . This book was released on 2003 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although there has been considerable work on the performance evaluation of collision avoidance schemes, most analytical work is confined to single-hop ad hoc networks or networks with very few hidden terminals. We present the first analytical model to derive the saturation throughput of collision avoidance protocols in multi-hop ad hoc networks with nodes randomly placed according to a two-dimensional Poisson distribution. We show that the sender-initiated collision-avoidance scheme achieves much higher throughput than the ideal carrier sense multiple access scheme with a separate channel for acknowledgments. More importantly, we show that the collision-avoidance scheme can accommodate much fewer competing nodes within a region in a network infested with hidden terminals than in a fully-connected network, if reasonable throughput is to be maintained. Simulations of the IEEE 802.11 MAC protocol and one of its variants validate the predictions made in the analysis. It is also shown that the IEEE 802.11 MAC protocol cannot ensure collision-free transmission of data packets and thus throughput can degrade well below what is predicted by the analysis of a correct collision avoidance protocol. Based on these results, a number of improvements are proposed for the IEEE 802.11 MAC protocol.
Download or read book Throughput and Fairness of Collision Avoidance Protocols in Ad Hoc Networks written by and published by . This book was released on 2004 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless ad hoc networks have received increasing interest in recent years because of their potential to be used in a variety of applications without the aid of any pre-existing network infrastructure. Due to the scarce channel bandwidth available in ad hoc networks, the design of efficient and effective medium access control (MAC) protocols that regulate nodes' access to a shared channel has become the subject of active research in recent years. Many MAC protocols have been proposed to mitigate the adverse effects of hidden terminals through collision avoidance. In Section 1, The authors present an analytical modeling to derive the saturation throughput of these sender-initiated collision avoidance protocols in multi-hop ad hoc networks with nodes randomly placed according to a two-dimensional Poisson distribution. They show that the sender-initiated collision-avoidance scheme achieves much higher throughput than the ideal CSMA scheme with a separate channel for acknowledgments. They also show that the collision-avoidance scheme can accommodate far fewer competing nodes within a region in a network infested with hidden terminals than in a fully connected network, if reasonable throughput is to be maintained. Simulations of the IEEE 802.11 MAC protocol and one of its variants validate the predictions made in the analysis. The simulation results also reveal the fairness problem in IEEE 802.11, which refers to the severe throughput degradation of some nodes due to their unfavorable locations in the network and the commonly used binary exponential backoff (BEB) algorithm that always favors the node that last succeeds. Section 2 introduce a framework to address the fairness problem and propose a topology-aware fair access (TAFA) scheme to realize the framework. Simulation results show that TAFA can solve the fairness problem in UDP-based applications with negligible degradation in throughput. Section 3 concludes this chapter with directions for future work.
Download or read book Performance of Collision Avoidance Protocols in Single Channel Ad Hoc Networks written by and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents the first analytical model to derive the saturation throughput of collision avoidance protocols in multi-hop ad hoc networks with nodes randomly placed according to a two-dimensional Poisson distribution. The authors show that the sender-initiated collision-avoidance scheme performs much better than the ideal Carrier Sense Multiple Access (CSMA) scheme with a separate channel for acknowledgments. But they also show that the collision-avoidance scheme can accommodate far fewer competing nodes within a region in a network infested with hidden terminals than in fully connected networks or those with just a few hidden terminals, if reasonable throughput is to be maintained. Simulations of the popular IEEE 802.11 MAC protocol show that it cannot ensure collision-free transmission of data packets and, thus, throughput can degrade well below what is predicted by the analysis of a correct collision avoidance protocol. Based on these results, a number of improvements are proposed for the IEEE 802.11 MAC protocol.
Download or read book AD HOC NETWORKS written by Prasant Mohapatra and published by Springer Science & Business Media. This book was released on 2006-01-16 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: AD HOC NETWORKS: Technologies and Protocols is a concise in-depth treatment of various constituent components of ad hoc network protocols. It reviews issues related to medium access control, scalable routing, group communications, use of directional/smart antennas, network security, and power management among other topics. The authors examine various technologies that may aid ad hoc networking including the presence of an ability to tune transmission power levels or the deployment of sophisticated smart antennae. Contributors to this volume include experts that have been active in ad hoc network research and have published in the premier conferences and journals in this subject area. AD HOC NETWORKS: Protocols and Technologies will be immensely useful as a reference work to engineers and researchers as well as to advanced level students in the areas of wireless networks, and computer networks.
Download or read book Real time Communication Protocols for Multi hop Ad hoc Networks written by Reinhard Gotzhein and published by Springer Nature. This book was released on 2020-01-01 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on core functionalities for wireless real-time multi-hop networking with TDMA (time-division multiple access) and their integration into a flexible, versatile, fully operational, self-contained communication system. The use of wireless real-time communication technologies for the flexible networking of sensors, actuators, and controllers is a crucial building block for future production and control systems. WirelessHART and ISA 100.11a, two technologies that have been developed predominantly for industrial use, are currently available. However, a closer analysis of these approaches reveals certain deficits. Current research on wireless real-time communication systems shows potential to remove these limitations, resulting in flexible, versatile, and robust solutions that can be implemented on today’s low-cost and resource-constrained hardware platforms. Unlike other books on wireless communication, this book presents protocols located on MAC layer and above, and build on the physical (PHY) layer of standard wireless communication technologies.
Download or read book Spatial Reuse and Collision Avoidance in Ad Hoc Networks with Directional Antennas written by and published by . This book was released on 2002 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The quest for efficient medium access control (MAC) protocols for multi-hop ad hoc networks has aroused great interest in using directional antennas. Some MAC protocols using directional antennas have been proposed in the past, which trade off spatial reuse and collision avoidance via a combination of omni-directional and directional transmission modes. In this paper, the authors argue that the benefit of spatial reuse achieved by a MAC protocol that uses directional mode in all transmissions can outweigh the benefit of a conservative collision avoidance MAC protocol that sends some omni-directional control packets to silence potential interfering nodes. Detailed simulation experiments of the popular IEEE 802.11 MAC protocol and its variants that make use of directional transmission mode in sufficiently random networks are presented. It is concluded that, in contention-based MAC protocols for multi-hop networks infested with hidden terminals, the aggressive channel access scheme featured by all-directional transmissions indeed outperforms other conservative schemes in terms of enhanced throughput and reduced delay.
Download or read book Medium Access Control in Ad Hoc Networks with Omni directional and Directional Antennas written by Yu Wang and published by . This book was released on 2004 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: An ad hoc network is a dynamic network formed on demand by a group of nodes without the aid of any pre-existing network infrastructure. An efficient and effective medium access control (MAC) protocol which regulates nodes access to the shared channel(s) is essential in an ad hoc network. Our work is focused on the throughput and fairness properties of existing omni-directional MAC protocols as well as enhancement of their performance with directional antennas via both analytical and simulation approaches. In the first part, we present the first analytical modeling of collision avoidance MAC protocols including the popular IEEE 802.11 MAC protocol in multi-hop ad hoc networks. We show that in ad hoc networks with a lot of hidden terminals, collision avoidance even if done correctly, can still limit achievable throughput significantly because of the much reduced spatial reuse. Then we advance the analytical modeling to evaluate those MAC protocols which use directional antennas and can achieve much higher throughput through directing transmissions and receptions to desired directions only. We show that the gain in spatial reuse outweighs that of collision avoidance and hence an aggressive all-directional scheme is more advantageous than other hybrid schemes that take conservative (or unnecessary) tradeoff between collision avoidance and spatial reuse. All the analytical work has provided very useful insight on the interaction between spatial reuse, interference reduction and collision avoidance that previous work lacked.
Download or read book Advances in Information Technology and Industry Applications written by Dehuai Zeng and published by Springer Science & Business Media. This book was released on 2012-01-15 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt: With success of ICEEE 2010 in Wuhan, China, and December 4 to 5, 2010, the second International Conference of Electrical and Electronics Engineering (ICEEE 2011) will be held in Macau, China, and December 1 to 2, 2011. ICEEE is an annual conference to call together researchers, engineers, academicians as well as industrial professionals from all over the world to present their research results and development activities in Electrical and Electronics Engineering along with Computer Science and Technology, Communication Technology, Artificial Intelligence, Information Technology, etc. This year ICEEE is sponsored by International Industrial Electronics Center, Hong Kong. And based on the deserved reputation, more than 750 papers have been submitted to ICEEE 2011, from which about 94 high quality original papers have been selected for the conference presentation and inclusion in the “Advanced Computer, Communication, and Control” book based on the referees’ comments from peer-refereed. All the papers will be published by Lecture Notes in Electrical Engineering (ISSN: 1876-1100), and will be included in Springer Link. We expect that the Advanced Computer, Communication, and Control book will be a trigger for further related research and technology improvements in the importance subject including Signal Processing, Retrieval and Multimedia, Artificial Intelligence, Computing and Intelligent Systems, Machine Learning, Biometric and Biomedical Applications, Neural Networks, Knowledge Discovery and Data Mining, Knowledge-based Systems, Control Systems, Modeling and Simulation Techniques, Wireless Communications, Advances in Wireless Video, etc.
Download or read book Sender and Receiver initiated Multiple Access Protocols for Ad hoc Networks written by Asimakis E. Tzamaloukas and published by . This book was released on 2000 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the medium access control (MAC) layer. Many MAC protocols for wireless networks proposed or implemented to date are based on collision-avoidance handshakes between sender and receiver. The key objective of collision-avoidance handshakes is reducing or eliminating the collision of data packets from a source at any given receiver due to interference from packets from other sources. In the vast majority of these protocols, including the IEEE 802.11 standard, the handshake is sender-initiated, in that the sender asks the receiver for permission to transmit using a short control packet, and transmits only after the receiver sends a short clear-to-send notification. There are two main objectives in this work: analyze the effect of reversing the collision-avoidance handshake as a way to improve the performance of MAC protocols under any conditions in the network, and design MAC protocols that provide correct floor acquisition without carrier sensing or code pre-assignment. We show that receiver-initiated collision-avoidance MAC protocols not only outperform any sender-initiated ones, but also guarantee collision-free data transmission and seamless support for mobility by using simple, low-cost wireless radios. We study the effect of persistent carrier sensing in receiver- as well as sender-initiated MAC protocols. We extend our work to multi-channel radios and introduce novel collision-avoidance MAC protocols that eliminate the need for carrier sensing and code pre-assignment, and improve the utilization of the medium in the presence of unicast, multicast and broadcast traffic.
Download or read book Collision Avoidance in Single Channel Ad Hoc Networks Using Directional Antennas written by and published by . This book was released on 2003 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Three collision-avoidance protocols are analyzed that use omni-directional packet reception together with omni-directional transmissions, directional transmissions, or a combination of both. A simple model is introduced to analyze the performance of these collision avoidance protocols in multi-hop networks with arbitrary topologies. The numerical results of this analysis show that collision avoidance using a narrow antenna beamwidth for the transmission of all control and data packets achieves the highest throughput among the three collision avoidance schemes considered. Simulation experiments of the popular IEEE 802.11 MAC protocol and its variants based on directional transmissions and omni-directional packet reception validate the results predicted in the analysis. The results further show that narrow-beamwidth transmissions also can reduce the average delay experienced by nodes. It is concluded that the advantage of spatial reuse achieved by narrow-beamwidth transmissions outweighs that of conservative collision avoidance schemes featured by the omni-directional transmission of some control packets. This is because the latter requires far more stringent coordination of nodes with their neighbors and hidden terminals, which can lead to much more channel resource wasted due to nodes' excessive waiting time.
Download or read book Broadcast Design in Cognitive Radio Ad Hoc Networks written by Yi Song and published by Springer. This book was released on 2014-12-04 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: This SpringerBrief investigates the special challenges of broadcast design in cognitive radio (CR) ad hoc networks. It introduces two broadcast protocols in CR ad hoc networks: a quality-of-service based broadcast protocol under blind information and a fully-distributed broadcast protocol with collision avoidance. A novel unified analytical model is also presented to analyze the performance of the broadcast protocols. This is the first book dedicated to the unique broadcast design challenges in CR ad hoc networks. The authors also discuss the recent research on the performance analysis of broadcast protocols. Broadcast Design In Cognitive Radio Ad Hoc Networks is designed for professionals and researchers working in the wireless networks industry. Advanced-level students in electrical engineering and computer science, especially those focused on wireless networks will find this information very valuable.
Download or read book Ad Hoc Networks written by Shiwen Mao and published by Springer Science & Business Media. This book was released on 2010-02-17 with total page 927 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ad hoc networks refer to the wireless networking paradigm that covers a variety of network forms for specific purposes, such as mobile ad hoc networks, sensor n- works, vehicular networks, underwater networks, underground networks, personal area networks, and home networks. The various forms of ad hoc networks promise a broad scope of applications in civilian, commercial, and military areas, which have led to significant new research problems and challenges, and have attracted great efforts from academia, industry, and government. This unique networking paradigm neces- tates re-examination of many established wireless networking concepts and protocols, and calls for developing new fundamental understanding of problems such as interf- ence, mobility, connectivity, capacity, and security, among others. While it is ess- tial to advance theoretical research on fundamentals and practical research on efficient algorithms and protocols, it is also critical to develop useful applications, experim- tal prototypes, and real-world deployments to achieve a practical impact on our so- ety for the success of this networking paradigm. The annual International Conference on Ad Hoc Networks (AdHocNets) is a new event that aims at providing a forum to bring together researchers from academia as well as practitioners from industry and government to meet and exchange ideas and recent research work on all aspects of ad hoc networks. As the first edition of this event, AdHocNets 2009 was successfully held in Niagara Falls, Ontario, Canada, during September 22–25, 2009.
Download or read book A Receiver Initiated Collision Avoidance Protocol for Multi Channel Networks written by and published by . This book was released on 2001 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The medium-access control (MAC) protocols for wireless networks proposed or implemented to date based on collision-avoidance handshakes between sender and receiver either require carrier sensing or the assignment of unique codes to nodes to ensure that intended receivers hear data packets without interference from hidden sources. We present and analyze a new collision-avoidance MAC protocol that we call receiver-initiated channel-hopping with dual polling (RICH-DP). RICH-DP is the first MAC protocol based on a receiver-initiated collision-avoidance handshake that does not require carrier sensing or the assignment of unique codes to nodes in order to ensure collision-free reception of data at the intended receivers in the presence of hidden terminals. The throughput and delay characteristics of RICH-DP is studied analytically, and extensive simulations are presented to verify the analysis and to present a more accurate prediction of how RICH-DP would operate in realistic scenarios. RICH-DP is applicable to ad-hoc networks based on commercial off-the-shelf frequency hopping radios operating in unlicensed frequency bands.
Download or read book Throughput and Fairness in A Hybrid Channel Access Scheme for Ad Hoc Networks written by and published by . This book was released on 2003 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel hybrid channel access scheme that combines sender-initiated and receiver-initiated collision-avoidance handshakes is proposed for multi-hop ad hoc networks. The scheme is based on the observation that a receiver-initiated scheme is more appropriate when receivers are more knowledgeable of the contention around themselves and can compete for the channel more effectively. By adaptively sharing the burden of initiating the collision-avoidance handshake between the nodes that experience different levels of contention, better fairness may be achieved with almost no degradation in throughput. An attractive feature of the new scheme is that it is a simple extension to the existing IEEE 802.11 MAC protocol, and it maintains compatibility with the standard. The new scheme involves adding very simple queue management and book-keeping work mechanisms. Simulation experiments of the IEEE 802.11 MAC protocol and the new scheme show that, although the proposed hybrid scheme does not solve the fairness problem conclusively, it does alleviate the fairness problem in some cases without sacrificing much throughput and simplicity. The difficulty of improving fairness for TCP-based flows is demonstrated. A promising topic for future work consists of combining the new hybrid scheme with some proposed mechanisms that try to approximate fair queueing for ad hoc networks to achieve some QoS assurances. Without explicit information exchange among nodes, the fairness problem cannot be solved conclusively.
Download or read book New Topics in Theoretical Computer Science written by Oleg N. Terikhovsky and published by Nova Publishers. This book was released on 2008 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical computer science focuses on the more abstract, logical and mathematical aspects of computing, such as the theory of computation, analysis of algorithms and semantics of programming languages. This new book presents the latest research in the field from around the globe.
