Download or read book Multi channel Mac Protocols with Bandwidth Utilization Enhancement in Wireless Ad Hoc Networks written by Yun-Jung Lu and published by . This book was released on 2012 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Control channel Reuse based Multi channel MAC Protocol for Ad Hoc Networks written by Divya Sardana and published by . This book was released on 2009 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ad hoc networks have become a popular type of wireless network in the present world. In order to match with the increasing demand of ad hoc networks, a lot of research is being done towards solving the issues related to the design of ad hoc networks. The design of a Medium Access Control (MAC) protocol for ad hoc networks is one such issue. Traditional MAC protocols involve the use of a single channel as the wireless medium. However, throughput of a single channel MAC degrades as the node traffic in the system increases. One of the interesting approaches towards alleviating this problem is the use of more than one channel as the underlying medium. The use of multiple channels allows more than one communication to take place simultaneously thereby improving the throughput of the system. Multiple channels have been mostly used in the literature by assigning one of the channels as the control channel used only for control packet transfer and the rest of the channels as data channels used for Data packet transfer. Using such an approach towards designing a multi-channel MAC protocol leads to a poor utilization of the available bandwidth. In this thesis, we propose a multi-channel MAC protocol called as Control-channel Reuse based Multi-channel MAC (CRM-MAC) which aims at improving the overall bandwidth utilization. We illustrate the efficacy of our protocol through elaborate simulations.

Download or read book Throughput Analysis and Enhancement of Multi Channel MAC Protocol in Ad Hoc Networks written by 高譓翔 and published by . This book was released on 2006 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cooperative Multi channel MAC Protocols for Wireless Ad Hoc Networks written by Yuhan Moon and published by . This book was released on 2010 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Medium Access Protocol MAC Design for Wireless Multi hop Ad Hoc and Sensor Networks written by Afef Sayadi and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless multi-hop ad hoc and sensor networks provide a promising solution to ensure ubiquitous connectivity for the Future Internet. Good network connectivity requires designing a reliable Medium Access Control (MAC) protocol, which is a challenging task in the ad hoc and sensor environments. The broadcast and shared nature of the wireless channel renders the bandwidth resources limited and expose the transmissions to relatively high collisions and loss rates. The necessity to provide guaranteed Quality of Service (QoS) to the upper layers triggered the design of conflict-free MAC protocols. The TDMA synchronization constraint is basically behind the rush of MAC protocol design based on a fixed frame size. This design shows inflexibility towards network variations and creates a network dimensioning issue that leads to a famine risk in case the network is under-dimensioned, and to a waste of resources, otherwise. Moreover, the alternative dynamic protocols provide more adaptive solutions to network topology variations at the expense of a fair access to the channel. Alongside with the efficient channel usage and the fair medium access, reducing the energy consumption represents another challenge for ad hoc and sensor networks. Solutions like node activity scheduling tend to increase the network lifetime while fulfilling the application requirements in terms of throughput and delay, for instance. Our contributions, named OSTR and S-OSTR, address the shortcomings of the medium access control protocol design in the challenging environment of wireless multi-hop ad hoc and sensor networks, respectively. For OSTR the idea consists in adopting a dynamic TDMA frame size that increases slot-by-slot according to the nodes arrival/departure to/from the network, and aiming to achieve a minimum frame size. For this end, OSTR couples three major attributes: (1) performing slot-by-slot frame size increase, (2) providing a spatial reuse scheme that favors the reuse of the same slot if possible, (3) and ensuring an on-demand frame size increase only according to the node requirements in terms of throughput. To tackle different frame sizes co-existence in the network, OSTR brings a cooperative solution that consists in fixing an appointment, a date when the frame size in the network is increased. Concerning S-OSTR, it is an amendment of OSTR for wireless sensor networks. It brings the idea of a dynamic active period, since it deploys a dynamic frame size that is built slot-by-slot according to nodes arrival to the network. S-OSTR enforces the slot-by-slot frame size increase by a node activity scheduling to prolong the inactivity period in the network, and hence prolong the overall network lifetime for wireless sensor networks. Our contributions are both based on the new dynamic TDMA frame size increase that consists in increasing the frame size slot-by-slot aiming to achieve a shorter frame size, and hence improve the channel utilization, and reduce the energy consumption. The performance analysis of OSTR and S-OSTR shows that they present good potentials to support QoS requirements, to provide energy-efficiency, to ensure fair medium access, to accommodate network topology changes and finally, to enhance robustness against scalability. The impact of this new TDMA frame size increase technique on the medium access control protocol performance is highlighted through multiple simulations of OSTR and S-OSTR. Multiple comparative studies are also handled to point out the effectiveness of this new technique and the soundness of our contributions.

Download or read book An Enhanced Medium Access Control Protocol for Ad Hoc Networks written by Priyadarshini Sabut and published by LAP Lambert Academic Publishing. This book was released on 2013 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ad hoc Networks are the most popular networks and are useful in many application environments due to less cost and easy deployment at anytime anywhere. The efficiency of these networks depends on the performance and reliability of the medium access control (MAC) protocol applied in such networks. The IEEE 802.11 DCF MAC protocol for ad hoc networks suffers from the problem of bandwidth sharing due to presence of hidden and exposed nodes. This book discusses a MAC protocol that not only overcomes the problem of hidden and exposed nodes but also allows the hidden nodes to transmit and exposed nodes to receive without interfering with the ongoing transmission in their vicinity, thereby improving channel utilization. The proposed protocol outperforms IEEE 802.11 DCF MAC in terms of throughput and packet delivery ratio with a little cost of control overhead.

Download or read book MAC Protocol Design in Full Duplex Enabled Wireless Networks written by Liqun Fu and published by Springer Nature. This book was released on with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multichannel Medium Access Control Protocol with Cooperative Channel Selection for Ad Hoc Networks written by Jai Mondhe and published by . This book was released on 2003 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: A mobile ad hoc network is a collection of mobile terminals equipped with wireless transceivers that form an autonomous network without any pre-planned infrastructure or centralized administration. Wireless hosts in an ad hoc network typically share a single common channel for communication. The Medium Access Control (MAC) allows the hosts to resolve contention while randomly accessing the channel and plays a key role in determining the efficiency of channel usage in the network. Usage of multiple channels improves the throughput of the MAC protocol in ad hoc networks by allowing multiple nodes to transmit concurrently on different non-overlapping channels. Efficient channel selection schemes can reduce the contention in each channel leading to smaller number of collisions, backoffs, and retransmissions. This research explores a new channel selection scheme that is based on maximizing the signal to interference ratio at the receiver as well as minimizing the interference caused to all other active receivers in the vicinity of the sender. An implementation of this "cooperative" channel selection technique is proposed employing receiver-initiated busy-tones and signal power measurements at the sending and receiving nodes respectively. Simulation based performance results are presented.

Download or read book A New Multi channel MAC Protocol for Wireless Ad Hoc Networks with Single Transceiver written by Musa Aykut Canbolat and published by . This book was released on 2007 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although IEEE 802.11a/b/g standards allow use of multiple channels, only a single channel is popularly used, due to the lack of efficient protocols that enable use of Multiple Channels. There are some papers challenging this problem. Some of them have requirements that will increase the cost, like requirement of multiple transceivers. Some others address the problem with single transceivers, but are very hard to be employed in highly mobile Ad Hoc networks due to network-wide synchronization requirements. In this Thesis, multiple channel use in a wireless network with single transceiver nodes is addressed, and attempted to be solved with a new efficient Ad Hoc network MAC protocol, which intends to remove the requirement of network-wide synchronization.

Download or read book Medium Access Control Protocols for Multi hop Wireless Ad Hoc Networks written by Venkatesh Rajendran and published by . This book was released on 2006 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Performance Enhancements in Wireless Multihop Ad hoc Networks written by Ahmad Ali Abdullah and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving the performance of the wireless multihop ad hoc networks faces several challenges. In omni-directional antenna based solutions, the use of the RTS/CTS mechanism does not completely eliminate the hidden-terminal and exposed-terminal problems. Deafness is an additional challenge to the directional antenna based solutions. This dissertation, first develops analytical models for quantifying the throughput and delay in wireless multihop ad hoc networks. The models consider the impact of hidden terminals using the realistic signal to interference and noise ratio model and consider random node distribution. The proposed analysis is applicable to many wireless MAC protocols and applications. The analytical results reveal several important issues. The first issue is quantifying the impact of adjusting the transmission range on the throughput and delay in wireless multihop ad hoc networks. The other issue is the hidden terminal region is closely related to the distance between the transmitter and the receiver. Thus, it is possible to adjust the transmission range to optimize the whole network performance. These results provide important guidelines for network planning and protocol optimization in wireless multihop ad hoc networks. Second, it proposes a new Enhanced Busy-tone Multiple Access (EBTMA) medium access control (MAC) protocol for minimizing the negative impact of both the hidden-terminal and the exposed-terminal problems. The new protocol can also enhance the reliability of packet broadcasts and multicasts which are important for many network control functions such as routing. Different from other busy-tone assisted MAC protocols, the protocol uses a non-interfering busy-tone signal in ashort period of time, in order to notify all hidden terminals without blocking a large number of nodes for a long time. In addition, the proposed EBTMA protocol can co-exist with the existing 802.11 MAC protocol, so it can be incrementally deployed. Third, it investigates how to support the directional antennas in ad hoc multihop networks for achieving higher spatial multiplexing gain and thus higher network throughput. A new MAC protocol called Dual Sensing Directional MAC (DSDMAC) protocol for wireless ad hoc networks with directional antennas is proposed. The proposed protocol differs from the existing protocols by relying on a dual sensingstrategy to identify deafness, resolve the hidden-terminal problem and to avoid unnecessary blocking. Finally, this dissertation provides important results that help for network planning and protocol optimization in wireless multihop ad hoc networks in quantifying the impact of transmission range on the throughput and the delay. The accuracy of these results has been verified with extensive discrete event simulations.

Download or read book Composite Metric Based Multi channel MAC Protocol for Ad hoc Network written by Yogita Mehta and published by . This book was released on 2005 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: [Author's abstract] Recent technology advances have opened a new spectrum of communication networks called ad hoc networks. In an ad hoc network, the Media Access Control (MAC) protocol of IEEE 802.11 Distributed Coordination Function (DCF), designed to share a single channel between nodes. This thesis presents a protocol that facilitates use of more than one channel and analytical analysis for the throughput of the network. One of the functions of a MAC layer is to scan all channels. A composite metric (CM) has been proposed for each available channel. The CM depends on the signal to noise ratio, the battery power remaining and the mobility of each node with respect to other nodes in the network. The channels with three higher CMs are selected at each node and are used to build a Preferred Channel List (PCL). During Announcement Traffic Indication Message (ATIM), the PCL is sent by the node intended to communicate with another node. If the PCL of the receiver node has non interfering channels with the PCL of the sender node, it responds with an ATIM ACK with its PCL. If the PCL of both nodes have appropriate channels, then the sender node replies with an ATIM RES indicating that at the end of the ATIM window, the RTS/CTS/DATA/ACK handshake will begin. A mathematical model based on Markov chain process is designed to derive an expression for saturation throughput and evaluate the performance of Composite Metric (CM) based Multi channel MAC (MMAC) against IEEE 802.11 MAC Distributed Co ordination Function (DCF) and Dynamic Channel Allocation (DCA) protocol. IEEE 802.11 MAC, DCA and CM based MMAC protocol works better for large data packets than for small data packets. Simulation results show enhancement of 35 to 95 percent in the overall throughput of the network when the proposed CM based MMAC protocol used over IEEE 802.11 MAC and DCA protocols.

Download or read book A Receiver initiated MAC Protocol with Enhancements for Multi hop Wireless Networks written by Balvinder Kaur Thind and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Performance Medium Access Control Protocols for Decentralized Wireless Networks Using Local Coordination written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Secure Routing and Medium Access Protocols in Wireless Multi hop Networks written by Soufiene Djahel and published by GRIN Verlag. This book was released on 2011-12 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Wireless Communication with Artificial Intelligence written by Anuj Singal and published by CRC Press. This book was released on 2022-09-16 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: This reference text discusses advances in wireless communication, design challenges, and future research directions to design reliable wireless communication. The text discusses emerging technologies including wireless sensor networks, Internet of Things (IoT), cloud computing, mm-Wave, Massive MIMO, cognitive radios (CR), visible light communication (VLC), wireless optical communication, signal processing, and channel modeling. The text covers artificial intelligence-based applications in wireless communication, machine learning techniques and challenges in wireless sensor networks, and deep learning for channel and bandwidth estimation during optical wireless communication. The text will be useful for senior undergraduate, graduate students, and professionals in the fields of electrical engineering, and electronics and communication engineering.