基于网络编码的IEEE 802.15.4 MAC协议优化

针对应用网络编码的多信源节点双向中继网络,在IEEE 802.15.4 MAC传输协议的基础上进行了优化.IEEE802.15.4 MAC协议在整个超帧的竞争访问周期均处于收发状态,优化后的MAC协议,在超帧的竞争访问周期,当信源节点接收到确认帧后,就关闭收发机制,信源节点进入睡眠状态,大大的节约了能量消耗.仿真结果表明优化后的MAC协议在完成系统功能的同时更好的节约了能耗.     

一种新颖的无线传感器网络的MAC协议

通过对MAC协议运行原理、具有的优缺点、目前所存在的问题以及网络中信道接入机制和能效问题进行分析的基础上,给出一种侦听/睡眠和CDMA相结合的混合MAC协议,此协议采用周期性侦听/睡眠机制和CDMA技术来保证数据的流畅传输,从而实现能量的有效利用。最后,利用仿真软件NS2证明新方法的优越性和高效性。     

一种无线传感网络节能MAC协议

在无线传感网络中,传感节点是能量受限的,因此能耗在这种网络显得十分重要,关系到整个网络的生命周期与性能.而无线传感网络的MAC协议对节点的节能有着重要的作用.本文在已有研究的基础上加以改进形成一种更有效的感知流量信息进行节能的MAC协议.该协议同S-MAC协议一样也是采用睡眠的机制,但不同于S-MAC的是该协议中监听与...     

MANETs中智能天线和功率控制的应用

分析了MANETs中基于CDMA的MAC协议存在的问题,提出在协议中引入智能天线和功率控制技术来解决多址干扰和远-近效应等问题.对采用智能天线和功率控制技术的MAC协议的工作原理进行了阐述,并通过仿真评估了智能天线与功率控制技术结合后对网络吞吐量和节点耗能的影响.研究结果表明,在MANETs中使用智能天线和功率控制技术可以有效地提高网络的吞吐量,降低节点的能耗.     

一种改进型自适应A-MAC算法分析与仿真

无线传感器网络的MAC协议可以利用监听/睡眠周期节约能源。对监听/睡眠周期和网络性能的关系进行了分析,研究了自适应的MAC协议及改进算法,通过动态调整节点唤醒的周期和相位来适应网络的动态变化。仿真表明改进后的协议可以减少时延,提高吞吐量和能源效率。     

低占空比无线传感器网络中MAC协议研究进展

无线传感器网络(WSN)是一种多跳自组织网络,它由大量具有有限能力的节点组成,在工业、农业、交通、国防等领域具有广泛应用.为了减少节点的能量消耗,延长网络的生命周期,近年来逐渐出现了基于低占空比技术(Low-Duty-Cycle)的WSN,简称LDC-WSN.在LDC-WSN中,节点在一个工作周期内大部分时间处于睡眠状态,只有极少时间内处于工作状态.MAC协议是实现LDC-WSN中节点睡眠调度的关键,对LDC-WSN保持正常工作并获得理想的工作性能具有非常重要的意义.针对LDC-WSN中MAC协议的研究仍处于起步阶段,是目前研究的热点.对当前研究进行综述,详细介绍和分析LDC-WSN中最具代表性和较新的MAC协议.通过对比和总结当前工作的优缺点,明确了目前存在的问题和难点,为未来更深入的研究指明了方向.     

无线传感器网络MAC协议移动性支持问题的研究

在以往的无线传感器网络研究过程中,研究者通常假设网络中节点的位置不发生变化,忽略了移动性对网络的影响.近期研究表明,支持无线传感器节点移动性,研究移动无线传感器网络MAC协议是十分必要的.本文在研究移动性对MAC协议设计所带来的挑战基础上,分析和总结了移动性对现有MAC协议的影响,以及当前在支持节点移动性方而所作的工作.最后,文章重点探讨了未来移动传感器网络MAC协议研究过程中值得深入研究的内容.     

一种自适应侦听的异步无线传感器网络MAC协议

为了提升异步无线传感器网络MAC协议在动态网络负载下的性能,论文提出了一种流量自适应的异步协议AA-MAC.该协议基于短前导序列采样技术,当节点收稿数据后并不理解转入睡眠而自适应增加若干个最短侦听时间用以接收发送节点的可能其他数据,使得收发双方在网络负载较重时能实现一次配对多次收发数据.分析并对比了AA-MAC和X-M...     

无线Adhoc网络中一种基于网络编码的协同MAC协议

协同通信中,中继节点通常用来转发源节点的数据分组.但是从中继节点的角度出发,帮助其它节点转发数据会降低其自身的性能,导致中继低效率问题的出现.针对此问题,该文基于网络编码设计了一种适用于无线Ad hoc网络的协同MAC协议.该协议将网络编码和协同机制相结合,在需要协同传输时,利用网络编码让中继节点在发送源节点数据的同时也发送自身的数据,利用网络编码来解决协同传输中中继低效率问题,进一步提升协同传输的性能.该文还在2维Markov退避模型的基础上,加入了网络编码和协同机制,对所提协议在多跳网络中进行了吞吐量性能分析,并探讨了网络节点数、多跳和信道质量对吞吐量性能的影响.仿真结果表明,相比一般的协同MAC协议,采用网络编码的协同MAC协议可以显著的改善系统性能,是解决协同传输中的中继低效率问题的有效手段.     

无线传感器网络功耗控制分析与仿真

根据无线通信原理为三种MAC协议(IEEE802.11MAC、BASIC、PCM)建立了能耗分析模型,对功率控制给网络带来影响进行了数学分析.并对三种MAC协议在不同网络规模中的吞吐量、能量效率进行仿真比较.仿真结果表明:有效的控制节点的发射功率,在减少能耗的同时,可以提高网络性能.     

A Hybrid Token-CDMA MAC Protocol for Wireless Ad Hoc Networks

Token-passing medium access control (MAC) protocols are gaining interest among wireless ad hoc network researchers as they provide unrivaled advantages over the existing IEEE 802.11 standards. This paper introduces a hybrid token-code division multiple access (CDMA) MAC protocol that is based on a token-passing scheme with the incorporation of CDMA. With its unique CDMA feature, the proposed MAC is able to support multiple simultaneous transmissions. The proposed protocol provides both quality of service (QoS) and high network resource utilization while ensuring the stability of the network. This paper examines the performance of the proposed MAC scheme by simulation and compares its performance against that of other MAC protocols that have appeared in the literature. Simulation results demonstrate that our proposed MAC scheme is effective in decreasing the packet delay and significantly shortens the length of the queue. The input traffic model used in the simulation is a two-state Markov-Modulated Poisson Process (MMPP). The data rate QoS is enforced by implementing a modified leaky bucket mechanism in the proposed MAC scheme. The simulation also takes into account channel link errors caused by the wireless link by implementing a multilayered Gilbert-Elliot model.     

Providing Real-Time Service in CDMA Wireless Networks

Medium Access Control (MAC) protocol design plays a very important role in the design of wireless networks. In this paper, we propose a new MAC protocol to provide real-time service for a CDMA wireless network. This protocol has been designed based on the distributed queuing random access protocol for CDMA wireless networks (DQRAP/CDMA). As real-time scheduling schemes have been introduced into the protocol design, the new protocol has an ability to accommodate real-time traffic in the CDMA wireless networks. A series of simulation experiments have been carried out to evaluate the performance of the proposed protocol. The results reveal that the proposed protocol can efficiently provide real-time service to the traffic composed of time constrained messages in the CDMA wireless networks.     

An Integrated Cluster-Based Multi-Channel MAC Protocol for Mobile Ad Hoc Networks

This paper proposes a novel joint clustering and multi-channel medium access control (MAC) protocol for mobile ad hoc networks, based on a scalable two-phase coding scheme. It employs the first-phase codes for differentiating the clusters and the second-phase codes for distinguishing the nodes in a specific cluster. The proposed protocol effectively integrates the procedure of code assignment with dynamic clustering and henceforth substantially reduces the control overhead of code assignment in a code division multiple access (CDMA) based multi-channel MAC protocol while simultaneously combating the hidden terminal problem. Furthermore, the confliction detection and resolution mechanism for the allocation of the first-phase codes as well as the collision avoidance mechanism for the allocation of the second-phase codes in the control channel are also introduced. Analytical framework and extensive simulation results, in terms of control overhead and delay, are provided and compared to the traditional distributed CDMA based multichannel MAC algorithms with or without clustering.     

Location-Aware Two-Phase Coding Multi-Channel MAC Protocol (LA-TPCMMP) for MANETs

In classical code division multiple access (CDMA) based multi-channel medium access control (MAC) protocols for mobile ad hoc networks (MANETs), numerous exchanges of neighborhood information are required for code assignment such that nodes within a two-hop separation will adopt different transmission codes and therefore avoid the hidden terminal problem (HTP). However, such expensive communication overhead for code assignment is not desirable since it will cause an under-utilization of bandwidth, energy inefficiency and longer delays, which can significantly degrade the network performance. In this paper, a novel location-aware multi-channel MAC protocol is presented for a large-scale dense MANETs based on a scalable two-phase coding scheme, where the first-phase code is used for differentiating adjacent cells and the second-phase code is employed for distinguishing nodes in one specific cell. A node knows its first-phase code from its location information and requests its second-phase code from its cell leaden. This protocol eliminates the HTP during data transmission without the periodical exchange of neighborhood information. Furthermore, the mechanism of collision resolution in the control channel is described. The performance of the proposed protocol is analyzed in terms of the control overhead and delay. The theoretical results are confirmed by extensive simulations and it is shown that the new protocol significantly outperforms the classical CDMA-based multi-channel MAC protocols     

The design of a channel-access protocol for a wireless ad hoc network with sectored directional antennas

A packet scheduler and a medium access control (MAC) protocol are presented for a direct-sequence spread-spectrum, wireless ad hoc network that contains a mix of nodes with directional antennas and nodes with omnidirectional antennas. The scheduler and MAC protocol are designed to prevent the co-site interference problem that arises in some types of nodes employing directional antennas. It is shown that the presence of nodes with directional antennas exacerbates the vulnerability of the network to the receiver blocking problem. A modification of the MAC protocol is presented that mitigates the receiver blocking problem, and it is shown to improve the performance of a network that includes nodes with directional antennas.     

Spread spectrum multiple access for mobile meteor burstcommunications

The paper considers the application of a direct sequence code division multiple access (CDMA) scheme to a mobile meteor burst communication network. It is shown that a CDMA scheme solves the significant multiple-access problem caused by low channel diversity when remote station nodes are closely spaced. The CDMA scheme is shown to provide low waiting times and high throughput for networks of many thousands of nodes. A comparison of the CDMA scheme to a random frequency division multiple access scheme is provided where the offered traffic load, network size, system bandwidth, and interference levels are varied     

Performance Evaluation of a New MAC Protocol for the CDMA Interconnection Network

A CDMA mobile system consists of subsystems that transmit and receive call control messages and traffic messages through the CDMA Interconnection Network (CIN). To assure high throughput and short delay in the CIN, an efficient Medium Access Control (MAC) protocol should be provided.In this study, we propose a new MAC protocol for CDMA interconnection networks in order to provide real-time communications in CDMA mobile systems. Also, we evaluate the delay performance of the proposed MAC protocol and compare it with that of existing MAC protocol. Through numerical examples, we show that the proposed protocol provides better delay performance than the existing protocol.     

A detailed study of a CDMA based approach to enhance ad hoc network performance

Random access schemes operate typically on a contention based common channel, which brings problems with increasing traffic load. These problems are emphasized in a multi-hop wireless ad hoc network environment. Efficient collision avoidance methods are needed, but they also tend to decrease the spatial capacity of the network. With CDMA (Code Division Multiple Access), it is possible to make multiple simultaneous co-located successful transmissions and thus increase network capacity within the limits of multiple access interference (MAI). Bi-code channel access (BCCA) is a method to apply CDMA in ad hoc networking, providing also a common access channel for network connectivity maintenance and self-configuration. With BCCA, collisions are rare, and thus, more straightforward medium access control (MAC) methods can be used. A MAC solution designed especially for BCCA (BC-MAC) and ad hoc networking increases the efficiency of the channel usage. As BCCA is based on receiver code CDMA, the spreading code of the next hop node is needed. A novel network layer spreading code distribution (NSCD) method is proposed for this purpose. The spreading codes are distributed within routing protocol control packets at the route establishment phase.A detailed study on the performance behavior of different methods is provided. Also, interesting aspects considering the ad hoc network operation are discussed. Instead of the widely used unrealistic cut propagation model, a propagation model with realistic MAI calculation is used in this study. It is shown that the use of NSCD increases the network control load only slightly, and that the performance is practically the same as it is with the assumption of known spreading codes. BCCA with its dedicated MAC and NSCD clearly outperforms commonly used methods (like IEEE 802.11) and yet is easy to implement, robust for design parameters under different conditions while maintaining the original idea of ad hoc networking.     

UW‐MAC: An underwater sensor network MAC protocol

As over 70% of the earth's surface is covered by water, it is desirable to deploy underwater sensor networks (UWSNs) to support oceanic research. UWSNs use acoustic waves and are characterized by long and variable propagation delays, intermittent connectivity, limited bandwidth and low bit rates. Energy savings have always been the primary concern in wireless sensor network protocols; however, there are applications where the latency and throughput are prioritized over energy efficiency and are so significant that the application would not be able to satisfy its requirements without them. Although existing duty‐cycle MAC protocols are power efficient, they introduce significant end‐to‐end delivery latency, provide poor throughput and are not suitable for the challenging environment of a UWSN. In this paper, we utilize CDMA as the underlying multiple access technique, due to its resilience to multi‐path and Doppler's effects prevalent in underwater environments. We propose UW‐MAC, a CDMA‐based power‐controlled medium access protocol that uses both transmitter‐based and receiver‐based CDMA inside a formed cluster, and uses a TDMA schedule to make the cluster heads communicate with the base station. Our MAC algorithm targets the latency and throughput needs in addition to its ability to increase the overall network lifetime. We discuss the design of UW‐MAC, and provide a head‐to‐head comparison with other protocols through extensive simulations focusing on the performance in terms of latency, throughput, and energy consumption. Copyright © 2009 John Wiley & Sons, Ltd.