一种高效节能的无线传感器网络 MAC 协议

针对无线传感器网络 MAC 协议的作用与要求,给出一种基于 CDMA 的 MAC 协议改进方案.根据网络负载变化采用周期性的侦听/睡眠机制,使大多数节点处于睡眠状态,节省能耗;同时结合 CDMA 技术给节点分配网内唯一的具有正交性的高速伪随机码(PN)来调制数据信号,使之在时域和频域重叠,实现数据的大规模实时传送.仿真结果表明,协议在保证系统低延时和高吞吐量的同时,能明显减少能量消耗.     

无线传感器网络S-MAC协议的能耗改进

无线传感器节点由于能量的耗尽而失效或者废弃,造成相应监测区域的空白,能耗问题一直是传感器网络介质访问控制（MAC）协议研究的重点问题之一。在S-MAC协议采用周期性侦听和睡眠机制、自适应侦听机制等方式改善网络能耗的基础上提出选择性睡眠、动态调整占空比、发送功率控制三种改进方法。通过NS2仿真实验,改进后S-MAC协议的能耗明显得到优化。     

无线传感器网络S-MAC协议研究

传感器节点能量受限,节能是传感器网络中媒体访问控制（MAC）协议设计的首要问题。采用周期性睡眠机制、自适应侦听机制、串音避免机制和消息传递机制可使得传感器媒体访问控制（S-MAC）协议在网络能耗和时延方面得到改进。对S-MAC协议的改进主要有两种方式：动态调整、区别控制包与数据包的发送条件进行发送。对无线传感器网络,要想设计出一种满足各方面要求的MAC协议是不现实的,可针对不同应用的要求,灵活采用不同的方式,设计出相应的协议。     

一种无线传感器网络MAC协议的优化方法

依据无线传感器网络生存期主要取决于节点MAC协议低能耗的特点,在S—MAC协议基础上,提出了一种MAC协议优化方法。优化后的协议侦听周期和休眠周期变化是随着网络数据流量而动态变化,这种变化并不是立即生效,而是设定侦听周期次数阈值,如果相邻侦听周期次数阈值内无激活事件,则减小侦听周期,如果相邻侦听周期次数阈值内有激活事件,则延长侦听周期。优化方法仿真显示,节能效果比原有协议有了提高。市场应用趋势,试图把握联通4G在为未来中国通信市场的发展前景,为中国联通4G市场战略决策提供理论参考。     

基于规则与感知的水声网络MAC协议

针对水声网络(UAN)媒体访问控制(MAC)协议采用RTS/CTS握手机制,导致信道利用率和网络吞吐量较低的问题,提出一套信道访问规则,基于该规则设计了节点状态感知的水声网络MAC(RP-MAC)协议.当接收节点不在收发状态,并且其他邻居节点也都不在接收状态时,发送节点才会尝试发送一到多个报文给接收节点.节点通过侦听和...     

基于GAF的无线传感器网络MAC协议

节能是无线传感器网络介质访问控制(MAC)协议的首要目标,综合近年来MAC协议的研究成果,针对S-MAC、T-MAC等几种典型协议进行分析,研究出将拓扑结构控制机制引入MAC协议,可进一步降低能耗。给出了一种基于GAF拓扑控制思想的MAC协议、GS-MAC协议。GS-MAC协议可以降低处于空闲侦听状态的节点数量,是一种高效节能的协议。仿真表明,引入拓扑控制后可以达到进一步节约能耗的目的。     

利用HFC接入Internet的MAC层协议设计与分析

分析了HFC网络实现双向数据传输的结构,分析比较了802.14/DOCSIS规范,提出使用扩频技术可以获得稳固的传输特性,就S＿CDMA多址接入方式和M＿ary CDMA方式分别设计了Internet接入的MAC层协议-竞争/冲突解决和轮询机制,分析表明该协议简单有效,易于实现。     

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。     

基于链路预测和网络编码的MAC机制

提出了基于链路预测和网络编码的MAC协议,在EasiLQE的基础上给出了基于窗口自适应的改进EF滤波器的链路质量预测方法,采用自适应周期的主动探测,增加网络环境稳定时的估计准确性,采用了瞬时主动探测模块,在保证估计稳定性的前提下提高了突发状况下的反应速度。在改进链路质量估计方法的基础上,给出了一种新的MAC协议。在协议中合理地利用了无线网络中已经存在的广播特性,在路由算法确定的路由周围增加高阶辅助节点,从而明显增加了网络编码机会,同时又不会引发由流量集中带来的诸多问题。最后讨论了MAC机制中最优的阶数,在编码机会和能量效率上寻求到一个较为合适的平衡点。实验证明,所提MAC协议能够在不集中流量的前提下合理利用节点的过度侦听提高编码机会,增加网络的吞吐量。     

无线传感器网络中一种动态节能的MAC协议

媒体访问控制(MAC)协议是无线传感器网络的关键协议之一,它对无线传感网络的运行和性能具有重要的影响.针对基于簇的TDMA机制存在问题,文中提出了一个动态节能的DE-MAC协议,该协议能够根据簇成员节点数目和通信负载动态地分配成员节点的时隙,减少节点的空闲侦听时间.仿真结果表明,DE-MAC协议能够有效地提高信道的利用率和网络能量有效性.     

Medium reservation based sensor MAC protocol for low latency and high energy efficiency

In this paper, we present a new MAC protocol satisfying with both high energy efficiency and low transmission latency at the same time over wireless sensor network, named as medium reservation preamble based MAC (MRPM). Unlike other synchronized duty cycle MACs, MRPM does not have separate time frames for SYNC and data traffics. Both traffics are integrated in a short listen period. Also, the channel contention is excluded from listen period and transferred to new period called contention period. The contention period precedes the listen period, and only transmitters wake up in this contention period and contend for medium reservation, whereas non-transmitters bypass it. These approaches enable MRPM to achieve adaptive duty cycle and quite short listen period. Moreover, MRPM uses carrier sensing information for advanced adaptive listening which makes packets to travel multiple hops away in a single sleep/listen cycle. The simulation results verify that MRPM has features of high energy efficiency and low latency.     

SW-MAC: A Low-Latency MAC Protocol with Adaptive Sleeping for Wireless Sensor Networks

A low duty-cycle operation medium access control (MAC) protocol is very important to conserve energy for resource-constrained wireless sensor networks. Traditional sleep-wake scheduling mechanisms of MAC protocols either require periodic synchronization beacons or bring high end-to-end delivery latency due to the lack of any synchronization. In this paper, we propose a low latency MAC protocol by adjusting the sleep window (SW-MAC) considering traffic patterns. Nodes in SW-MAC transmit a sequence of scout packets to wake up the next hop and estimate the traffic arrival time from upstream nodes to sleep adaptively. For the large variance traffic, we adjust the sleep window using additive increase/multiplicative decrease mechanism. And then we design a scout-based scheduling mechanism with the above algorithms to shorten the delivery latency. Simulation results indicate that SW-MAC could significantly reduce the end-to-end packet delivery latency without sacrificing energy efficiency.     

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.     

An adaptive quorum-based energy conserving protocol for IEEE 802.11 ad hoc networks

The lifetime of a mobile ad hoc network (MANET) depends on the durability of the mobile hosts' battery resources. In the IEEE 802.11 Power Saving Mode, a host must wake up at every beacon interval, to check if it should remain awake. Such a scheme fails to adjust a host's sleep duration according to its traffic, thereby reducing its power efficiency. This paper presents new MAC protocols for power saving in a single hop MANET. The essence of these protocols is a quorum-based sleep/wake-up mechanism, which conserves energy by allowing the host to sleep for more than one beacon interval, if few transmissions are involved. The proposed protocols are simple and energy-efficiency. Simulation results showed that our protocols conserved more energy and extended the lifetime of a MANET.     

无线局域网中的预约CDMA接入技术

在传统的无线ＭＡＣ接入协议（如ＡＬＯＨＡ,ＣＳＭＡ／ＣＡ,ＴＤＭＡ和ＣＤＭＡ）的基础上,重点探讨了基于码分多址的预约ＣＤＭＡ无线多址接入协议。该协议的在无线局域网接入时,无论在时间延迟还是吞吐量特性方面均比传统的无线接入协议有很大的改善。     

Analysis and optimization of duty-cycle in preamble-based random access networks

Duty-cycling has been proposed as an effective mechanism for reducing the energy consumption in wireless sensor networks (WSNs). Asynchronous duty-cycle protocols where the receiver wakes up periodically to check whether there is a transmission and the sender transmits preambles to check if the receiver is awake are widely used in WSNs due to the elimination of complex control mechanisms for topology discovery and synchronization. However, the intrinsic simplicity of the asynchronous mechanism has the drawback of smaller energy saving potential that requires the optimization of the duty cycle parameters. In this paper, we propose a novel method for the optimization of the duty-cycle parameters in preamble-based random access networks based on the accurate modeling of delay, reliability and energy consumption as a function of listen time, sleep time, traffic rate and medium access control (MAC) protocol parameters. The challenges for modeling are the random access MAC and the sleep policy of the receivers, which make it impossible to determine the exact time of data packet transmissions, and thus difficult to investigate the performance indicators given by the delay, reliability and energy consumption to successfully receive packets. An analysis of these indicators is developed as a function of the relevant parameters of the network and it is used in the minimization of the energy consumption subject to delay and reliability requirements. The optimization provides significant reduction of the energy consumption compared to the previously proposed protocols in the literature.     

Design and analysis of cellular mobile communications system basedon DQRAP/CDMA MAC protocol

Future third-generation mobile communication systems will need multi-access control (MAC) protocols suitable for multimedia code division multiple access (CDMA) radio communications. Distributed queueing random access protocol (DQRAP)/CDMA is a general purpose MAC protocol oriented to the CDMA environment. Analytical model expressions and computer simulations have shown its capacity to achieve near-optimum performance under heterogeneous traffic scenarios in a unicellular environment. A cellular environment has been designed to verify that DQPAP/CDMA maintains its near-optimum performance in a packet switched mobile communication system. A new handover technique based on the protocol is proposed to further improve the system performance