采用两种信道接入机制的认知无线电网络

时隙Aloha和CSMA是有效的随机接入协议,它们能组成更先进的媒体接入协议。研究了采用时隙Aloha和CSMA的认知无线电网络。其中,主用户比次用户有更高的优先权,次用户需检测信道,避免干扰主用户。因此,主用户采用时隙Aloha接入信道,次用户采用CSMA感知时隙Aloha的时隙,在空闲时隙传输数据包。     

无线传感网混合类MAC协议研究综述

在无线传感网( WSN)体系结构中,介质访问控制( MAC)协议负责调配网络中节点的信道接入,具有保障网络高效通信的重要作用。混合类MAC 协议综合了竞争类MAC 协议以及调度类MAC协议的特点,在融合两种机制的优点的同时克服其缺点,为无线信道资源的分配提供了更加灵活和全面的策略。首先概述了无线传感网MAC协议设计要点及分类,然后重点分析了无线传感网中经典的混合类MAC协议及国内外前沿的研究进展,并进一步归纳对比了各协议运行机制、性能及不足,得出混合类MAC协议的应用相关性及差异性的结论,最后总结了无线传感网混合类MAC协议研究现状并指出了未来的研究重点,以期为相关领域的研究人员提供参考。     

无线传感器网络MAC层协议的对比研究

无线传感器网络是二十一世纪新兴的网络技术，它的出现使网络的发展进入一个新的阶段。针对无线传感器网络MAC层协议的研究一直是人们普遍关注的问题。总结了近年来的研究成果并针对TDMA，IEEE802．15．4，S—MAC，T—MAC几种典型的MAC层协议进行了对比分析，根据其各自的优点提出将来工作的方向和建议。     

Improved channel‐aware MAC protocols for wireless local area networks

This paper studies the fading properties of the communication channel assumed in wireless local area networks (WLANs) and devises efficient channel‐aware protocols for the distributed coordination function (DCF) and the point coordination function (PCF), the two modes of communication defined in the IEEE standard for WLAN. Our simulations show that the proposed PCF protocol improves the channel capacity usage up to 14% and the proposed DCF protocol improves the channel capacity up to 90%, when compared with standard IEEE 802.11 implementations, depending on the loss rate and temporal characteristics of the wireless channel. The proposed protocols introduce minimum computational overhead. We also show that, compared with standard DCF protocol defined in IEEE 802.11, the proposed DCF protocol can lower the SNR requirements for a given packet error rate thus potentially extending the battery life of portable devices that use WLAN.. Copyright © 2004 John Wiley & Sons, Ltd.     

太赫兹无线局域网MAC协议优化设计

针对现有太赫兹无线网络MAC(Medium Access Control)协议中存在的无线局域网场景下原有波束赋形方案不适用、关联请求时段在新入网节点数量受限情况下时隙利用率低,以及网络流量较大时扇区号靠后的节点一直无法获得时隙导致时延陡增的情况,提出了一种适用于无线局域网的高效低时延太赫兹MAC协议(High Efficiency and Low Latency Terahertz MAC,HELL-MAC)。该协议利用中心控制节点与普通节点间的信息交互减少了不必要的波束赋形过程,采用机会性复用关联S-CAP(Sub-channel Access Period)机制提高了时隙利用率,采用公平时隙分配机制提高了时隙分配的公平性,从而减少了波束赋形时间,降低了平均端到端时延,提高了信道利用率。     

基于ALOHA的无线网络随机接入协议研究

针对无线网络中的随机接入问题,详细介绍了ALOHA,时隙ALOHA及相关改进协议的基本原理和方法,介绍并讨论了多种常用的冲突解决算法,同时结合数学推导,对基于ALOHA的多种随机接入协议的特点和性能进行了分析。     

QoS for wireless sensor networks: Enabling service differentiation at the MAC sub-layer using CoSenS

Providing service differentiation in wireless sensor networks while proposing simple and highly scalable solution is a challenging problem. We retain the use of CSMA/CA as access protocol because of its simplicity, versatility and good scalability properties. We developed CoSenS, a Collect then Send burst Scheme, on top of it to address its weaknesses while facilitating the implementation of scheduling policies. In this article, we propose a simple and scalable service differentiation solution; we implement fixed priority and earliest deadline first on top of CoSenS. The simulation analysis shows that our solution self-adapts to the traffic variation and greatly enhances end-to-end delay, reliability and deadline meet ratio for urgent traffic while not degrading best effort traffic compared to IEEE 802.15.4 original protocol and IEEE 802.15.4 implementing these scheduling policies. Additionally, CoSenS is implemented and tested on motes. The real experimentation results validated our simulation analysis.     

无线传感器网络及其MAC层协议

无线传感器网络（WSN）是当今信息领域的一大研究热点，在军事、环境、医疗护理和智能家居等方面有着广阔的应用前景，引起了世界各国的广泛关注。首先介绍了无线传感器网络的相关理论知识，然后对无线传感器网络目前所采用的典型的MAC协议按类型进行了介绍。     

无线传感器MAC层协议的研究

作为信号处理、通信和传感器三项技术结合的产物，无线传感器网络具有许多方面的应用，像在环境保护、领土安全和未来数字化战争等中。近年来对无线传感器的介质访问控制（Media Access Control，MAC）层协议研究也越来越多。在详细介绍了一些典型的协议基础上分析了协议的优缺点，以便无线传感器网络MAC层协议的近一步研究和改进。     

基于网络编码与空时编码的协作MAC协议

针对无线ad hoc网络中协作造成的中继效率低以及不同QoS需求难以满足等问题,提出了一种联合网络编码和空时编码的协作MAC协议(NSTCMAC)。NSTCMAC将网络编码与空时编码技术相结合,设计出区分业务类型的协作MAC协议传输机制,以满足不同业务类型的QoS需求;进一步通过马尔科夫链模型分析了区分业务类型的协作机制及性能。仿真结果表明,相比传统的DCF、COOPMAC以及CD-MAC协议,NSTCMAC协议能更好地保证不同的QoS需求,并能有效地解决协作造成的中继效率低的问题。     

I-MAC: an incorporation MAC for wireless sensor networks

This paper proposes an innovative MAC protocol called I-MAC. Protocol for wireless sensor networks, which combines the advantages of collision tolerance and collision cancellation. The protocol increases the number of antenna in wireless sensor nodes. The purpose is to monitor the occurrence of packet collisions by increasing the number of antenna in real time. The built-in identity structure is used in the frame structure in order to help the sending node to identify the location of the receiving node after a data packet collision is detected. Packets can be recovered from where the conflict occurred. In this way, we can monitor the conflict for a fixed period of time. It can improve the channel utilisation through changing the transmission probability of collision nodes and solve the problem of hidden terminal through collision feedback mechanism. We have evaluated our protocol. Our results show that the throughput of I-MAC is 5 percentage points higher than that of carrier sense multiple access/collision notification. The network utilisation of I-MAC is more than 92%.     

Enhanced cooperative MAC for wireless local area networks

A novel network protocol,enhanced cooperative medium access control(ECoop MAC),is present in this article.Its function is to guarantee the quality of service(QoS)in wireless local area networks.For the sake of supporting different application scenarios,two proposed schemes,namely E-scheme I for lower priority traffic and E-scheme II for higher priority traffic can be adopted independently or in combination.ECoop MAC takes into account request failure problems,and utilizes cooperative protocol information to boost the system performance as well as to effectively cut control packets overhead.Simulation results show that the proposed algorithm can not only improve network throughput,but also lead to reduced network delays for individual packets.     

RPCP‐MAC: Receiver preambling with channel polling MAC protocol for underwater wireless sensor networks

To design a reliable and energy efficient medium access control (MAC) protocol for underwater wireless sensor networks (UWSNs) is an active research area due to its variety of applications. There are many issues associated with underwater acoustic channels including long and variable propagation delay, attenuation, and limited bandwidth which pose significant challenges in the design of MAC protocol. The available sender‐initiated asynchronous preamble‐based MAC protocols for UWSNs are not reliable and energy‐efficient. This is due to the problems caused by transmission of preambles for longer duration and collision of preambles from hidden nodes in sender‐initiated preamble‐based MAC protocols. To resolve these issues, the paper proposed an asynchronous receiver‐initiated preamble‐based MAC protocol named Receiver Preambling with Channel Polling MAC (RPCP‐MAC) protocol for shallow underwater monitoring applications with high data rates. The protocol is proposed to resolve data packet collision and support reliability in an energy‐efficient way without using any transmission schedule. The proposed protocol is based on the following mechanisms. Firstly, receiver preambling mechanism is adopted to reduce idle listening. Secondly, channel polling mechanism is used to determine missing data frame during its sleeping period and to minimize the active time of node and reduces energy wastage. Finally, a back‐off mechanism is applied to resolve collision when preambles are received simultaneously. In addition, performance analysis through Markov chain together with its validation with simulation‐based studies is reported in the paper. Both the analytical and simulation results have demonstrated the reliability achievable with RPCP‐MAC while providing good energy efficiency.     

MAC protocols for wireless sensor networks: a survey

Wireless sensor networks are appealing to researchers due to their wide range of application potential in areas such as target detection and tracking, environmental monitoring, industrial process monitoring, and tactical systems. However, low sensing ranges result in dense networks and thus it becomes necessary to achieve an efficient medium-access protocol subject to power constraints. Various medium-access control (MAC) protocols with different objectives have been proposed for wireless sensor networks. In this article, we first outline the sensor network properties that are crucial for the design of MAC layer protocols. Then, we describe several MAC protocols proposed for sensor networks, emphasizing their strengths and weaknesses. Finally, we point out open research issues with regard to MAC layer design.     

The λMAC framework: redefining MAC protocols for wireless sensor networks

Most current WSN MAC protocol implementations have multiple tasks to perform—deciding on correct timing, sending of packets, sending of acknowledgements, etc. However, as much of this is common to all MAC protocols, there is duplication of functionality, which leads to larger MAC protocol code size and therefore increasing numbers of bugs. Additionally, extensions to the basic functionality must be separately implemented in each MAC protocol. In this paper, we look at a different way to design a MAC protocol, focusing on the providing of interfaces which can be used to implement the common functionality separately. This leaves the core of the MAC protocol, determining only when to send, which is substantially different for each protocol. We also look at some examples of MAC extensions that this approach enables. We demonstrate a working implementation of these principles as an implementation of B-MAC for TinyOS, and compare it with the standard TinyOS B-MAC implementation. We show a 35% smaller code size, with the same overall functionality but increased extensibility, and while maintaining similar performance. We also present results and experiences from using the same framework to implement T-MAC, LMAC, and Crankshaft. All are demonstrated with data from real-world experience using our 24 node testbed.     

一种基于预约的无线传感器网络MAC协议

无线传感器网络要求的能量高效,低延时,使得MAC协议的设计充满挑战。近来已经提出了很多基于簇的MAC协议,为减少冲突在簇内部采用TDMA方式来协调簇内各个节点的传输。提出了一种在采用簇结构的基础上,使用预约方式来发送数据的R-MAC（Reservation-MAC）协议。当争用节点少的时候,采用随机争用方式来预约数据的发送;在争用节点多的时候,采用时隙争用方式来预约数据的发送。分析表明,R-MAC能够有效地降低能耗和减少延迟。     

Novel MAC protocol for terahertz ultra-high data-rate wireless networks

Due to having a large bandwidth to support Gbps-level data rate, terahertz communication attracts more and more attention in recent years. However, there are few medium access control （MAC） protocols for terahertz ultra-high data-rate wireless networks, which affects the research and application of terahertz communications. To address this problem and to achieve ultra-high data-rate wireless access with terahertz communication, a novel MAC protocol, called medium access control for terahertz communication （MAC-TC）, is proposed. Through designing a new channel access scheme, a new superframe structure, and related key parameters, MAC-TC can support a maximum data rate up to 10 Gbit/s even higher. Theoretical analysis and simulation results show that our proposed MAC protocol realizes the function of medium access control and attains a maximum data rate of 18.3 Gbit/s, which is 2 times higher than 5.78 Gbit/s, the theoretical maximum data rate of IEEE 802.15.3c standard.     

一种适合无线多跳Mesh网络的MAC协议研究

提出了一种适合全分布方式无线多跳网络的MAC层协议,使用带外信号来调度媒体接入,以解决隐藏终端和暴露终端问题。仿真结果显示,网络吞吐量和端到端延迟都得到了明显改善。     

基于节能策略的无线传感器网络MAC协议

由于无线传感器网络的特殊性,针对其节能问题的媒体访问控制(MAC)协议研究越来越受到人们的关注.首先分析了无线传感器网络中能源损耗的原因,接着对近年来典型的基于节能策略的无线传感器网络MAC协议进行了分析总结,并综合其它性能指标比较了协议性能,最后提出了一些未来的研究方向.