802.11MAC协议仿真性能分析

自组织网是随着无线通信技术的快速发展而出现的一种新型多跳对等网络。由于它自身的特殊性,使得媒体接入控制协议(MAC)与传统的有线局域网、无线局域网以及蜂窝网络有很大的区别。MAC协议是自组织网协议的基础,它控制着节点对无线媒体的占用,对自组织网整体性能的提高起着决定性的作用。     

无线传感器MAC层协议的分析和研究

无线传感器网络(Wireless Sensor Network,WSN)一般由部署在监测区域内大量廉价微型传感器节点组成,通过无线通信方式形成一个多跳(mutli hop)的自组织(self organizing)网络系统。MAC层协议设计是无线传感器网络设计中的一个重要研究方面,通过对当前众多MAC协议的研究,提出了一种无线传感器网络MAC层协议的分类方法,通过分析比较典型的MAC层协议,给出了MAC层协议设计的评价标准。     

IEEE 802.11移动自组织网络节点竞争窗口长度的概率分布

 在基于IEEE 802.11的移动自组织网络中,MAC(Medium Access Control)层提供了DCF(Distributed Coordinate Function)以控制节点对无线信道的争用.DCF包括了BEB (Binary Exponential Backoff)算法.该文对BEB的重要参数——竞争窗口CW(Contention Window)进行研究,通过随机建模,导出了竞争窗口长度的概率分布,并进行数值分析.研究结果可应用于IEEE 802.11移动自组织网络.     

无线自组织网络MAC帧传输技术研究

无线自组织网络是近年来科学研究的热点领域之一,具有很强的实际应用价值和广泛的应用前景。实现MAC帧传输是无线自组织网络要解决的关键问题之一。采用基于路由的传输方式,可以有效实现MAC帧传输。首先通过路由生成协议和路由维护协议建立起稳定的路由,然后MAC帧将源节点中的路由封装到MAC帧头作为传输路径,最后MAC帧沿路由预定的路径,以多跳中继的方式到达目的节点。     

无线传感器网络和移动自组织网络的MAC协议

首先对移动自组织网络与无线传感器网络进行介绍;接着指出了在多跳和自组织要求下．MAC需要解决的两个基本问题．即网络形成和公平有效地在节点之间共享通信资源;然后对现有的MAC协议进行了分类与回顾．阐述了MAC协议的最新进展;最后指出了MAC协议需要解决的问题。     

以太网技术基础(二):介质接入控制方法

以太网介质接入控制 MAC(Media AccessControl)方法是用于控制网上每个站点接入网中介质的方法。 MAC是以太网络与节点之间关键接口。从高层来的接收数据帧经 MAC控制被送到物理层器件 (PHY) ,由此帧被转换成包 ,然后将其发送到网上 ;反之 ,从网上介质来的包信息经 PHY变换为帧后 ,再经 MAC控制送入上层处理帧相适应的软件。这就是说 MAC控制每个网站信息的收发以及收发信息的时间 ,这是至关重要的。这里物理层器件(PHY)的主要功能是使 MAC层与局域以太网使用的介质无关 ,从而使上层的数据和协议与网络使用的介质无直接关系。关…     

无线自组织网中VoIP性能研究

目前,VoIP技术及其业务迅速发展,在无线自组织网络中有广泛的应用,有必要对于VoIP在无线自组网中的传输进行分析研究。利用NS-2作为仿真工具对G.711编码标准下多跳无线自组织网中VoIP的传输进行仿真,使用802.11MAC层协议和AODV路由层协议。实验结果表明,无线自组织网络环境下VoIP系统性能(包括丢包率、时延等)受到多跳影响。     

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.     

自组织网MAC协议节能机制的研究与分析

为了解决自组织网节点供电不足的问题，在MAC接入方式的算法上进行改进是有必要的。从功率控制和能量管理两个方面，讨论自组织网几种典型的MAC层节能协议，分析这些算法减少功耗的能力以及在这些协议下自组织网络的吞吐量、时延等网络性能，并指出他们的优势和局限性，最后给出了结论。     

车载自组织网络关键技术

车载自组织网络(VANET)是一种自组织、结构开放的车辆间通信网络,随着无线通信技术与交通业联系的日益密切,VANET得到了大力发展。本文从VANET的基本概念和发展进程出发,综述VANET的关键技术。首先介绍VANET的网络模型、主要特点及体系结构,然后对VANET的物理层、MAC层、路由协议及应用层的研究内容和研究现状进行了系统阐述,最后对VANET今后的研究方向和应用前景进行了展望。     

Flying Ad-Hoc Networks (FANETs): A survey

One of the most important design problems for multi-UAV (Unmanned Air Vehicle) systems is the communication which is crucial for cooperation and collaboration between the UAVs. If all UAVs are directly connected to an infrastructure, such as a ground base or a satellite, the communication between UAVs can be realized through the in-frastructure. However, this infrastructure based communication architecture restricts the capabilities of the multi-UAV systems. Ad-hoc networking between UAVs can solve the problems arising from a fully infrastructure based UAV networks. In this paper, Flying Ad-Hoc Networks (FANETs) are surveyed which is an ad hoc network connecting the UAVs. The differences between FANETs, MANETs (Mobile Ad-hoc Networks) and VANETs (Vehicle Ad-Hoc Networks) are clarified first, and then the main FANET design challenges are introduced. Along with the existing FANET protocols, open research issues are also discussed.     

智能车载自组织网络中匿名在线注册与安全认证协议

随着智能交通系统(ITS)的建立,车载自组织网络(VANETs)在提高交通安全和效率方面发挥着重要的作用。由于车载自组织网络具有开放性和脆弱性特点,容易遭受各种安全威胁与攻击,这将阻碍其广泛应用。针对当前车载自组织网络传输中数据的认证性与完整性,以及车辆身份的隐私保护需求,该文提出一种智能车载自组织网络中的匿名在线注册与安全认证协议。协议让智能车辆在公开信道以匿名的方式向交通系统可信中心(TA)在线注册。可信中心证实智能车辆的真实身份后,无需搭建安全信道,在开放网络中颁发用于安全认证的签名私钥。车辆可以匿名发送实时交通信息到附近路边基站单元(RSU),并得到有效认证与完整性检测。该协议使得可信中心可以有效追踪因发送伪造信息引起交通事故的匿名车辆。协议可以让路边基站单元同时对多个匿名车辆发送的交通信息进行批量认证。该协议做了详细的安全性分析和性能分析。性能比较结果表明,该协议在智能车辆端的计算开销以及在路边基站单元端的通信开销都具有明显优势,而且无需搭建安全信道就能够实现匿名在线注册,因此可以安全高效地部署在智能车载自组织网络环境。     

一种基于可靠最远转发的车载网广播协议

许多车载自组网应用依赖于可靠高效的广播,但车载自组网节点高速移动,网络连通性随场景和时间动态变化的特性给广播协议的设计带来巨大挑战。为了应对这种挑战,该文在分析和验证简单最远转发机制具有低可靠性的同时,提出一种基于广播方向的可靠最远转发策略,并结合捎带确认机制设计了一种新的自组网多跳广播协议。与简单最远转发相比,可靠最远转发能明显降低转发节点失效的概率,提高消息单跳传播的可靠性;捎带确认机制使得协议能够适应网络连通性较差的场景,提升了消息全网传播的可靠性。仿真结果表明,提出的协议能在各种场景中实现高可靠性、低冗余的广播。     

一种可证安全的车联网无证书聚合签名改进方案

车联网(VANETs)是组织车－X(X:车、路、行人及互联网等)之间的无线通信和信息交换的大型网络,是智慧城市重要组成部分。其消息认证算法的安全与效率对车联网至关重要。该文分析王大星等人的VANETs消息认证方案的安全不足,并提出一种改进的可证安全的无证书聚合签名方案。该文方案利用椭圆曲线密码构建了一个改进的安全无证书聚合认证方案。该方案降低了密码运算过程中的复杂性,同时实现条件隐私保护功能。严格安全分析证明该文方案满足VANETs的安全需求。性能分析表明该文方案相比王大星等人方案,较大幅度地降低了消息签名、单一验证以及聚合验证算法的计算开销,同时也减少了通信开销。     

An efficient voting based decentralized revocation protocol for vehicular ad hoc networks

Vehicular Ad-hoc NETworks (VANETs) enable cooperative behaviors in vehicular environments and are seen as an integral component of Intelligent Transportation Systems (ITSs). The security of VANETs is crucial for their successful deployment and widespread adoption. A critical aspect of preserving the security and privacy of VANETs is the efficient revocation of the ability of misbehaving or malicious vehicles to participate in the network. This is usually achieved by revoking the validity of the digital certificates of the offending nodes and by maintaining and distributing an accurate Certificate Revocation List (CRL). The immediate revocation of misbehaving vehicles is of prime importance for the safety of other vehicles and users. In this paper, we present a decentralized revocation approach based on Shamir’s secret sharing to revoke misbehaving vehicles with very low delays. Besides enhancing VANETs’ security, our proposed protocol limits the size of the revocation list to the number of the revoked vehicles. Consequently, the authentication process is more efficient, and the communication overhead is reduced. We experimentally evaluate our protocol to demonstrate that it provides a reliable solution to the scalability, efficiency and security of VANETs.     

A reliable,delay bounded and less complex communication protocol for multicluster FANETs

Recently, Flying Ad-hoc Networks (FANETs), enabling ad-hoc networking between Unmanned Aerial Vehicles (UAVs) is gaining importance in several military and civilian applications. The sensitivity of the applications requires adaptive; efficient; delay bounded and scalable communication network among UAVs for data transmission. Due to communication protocol complexity; rigidity; cost of commercial-off-the-shelf (COT) components; limited radio bandwidth; high mobility and computational resources; maintaining the desired level of Quality of Service (QoS) becomes a daunting task. For the first time in this research we propose multicluster FANETs for efficient network management; the proposed scheme considerably reduces communication cost and optimizes network performance as well as exploit low power; less complex and low cost IEEE 802.15.4 (MAC) protocol for intercluster and intracluster communication. In this research both beacon enabled mode and beaconless modes have been investigated with Guaranteed Time Slots (GTS) and virtual Time Division Multiple Access (TDMA) respectively. The methodology plays a key role towards reserving bandwidth for latency critical applications; eliminate collisions and medium access delays. Moreover analysis ad-hoc routing protocols including two proactive (OLSR, DSDV) and one reactive (AODV) is also presented. The results shows that the proposed scheme guarantees high packet delivery ratios while maintaining acceptable levels of latency requirements comparable with more complex and dedicatedly designed protocols in literature.     

基于交叉层设计的MIMO Ad—hoc网络的MAC层调度算法

在应用多入多出(MIMO)技术的无线Ad-hoc网络中,基于交叉层优化,设计了介质访问控制(MAC)层的优化调度算法。通过网络层、MAC层及物理层交换关键参数信息,在各无线节点分布式地进行优化调度,以选择发送节点以及在这些节点上进行流分配,选择用于发送数据的天线阵列子集,从而提高整体网络的性能。仿真结果显示,与简单单链路算法相比,交叉层设计优化算法可以显著提高MIMOAd-hoc网络的整体容量。     

An efficient TDMA-based variable interval multichannel MAC protocol for vehicular networks

Vehicular Adhoc NETworks (VANETs) are the key to the future of intelligent transportation systems. An efficient MAC protocol is of greater importance to meet the strict deadlines of safety related applications in VANETs. This work introduces a novel TDMA-based variable interval multichannel MAC protocol (TM-MAC) for VANETs. TM-MAC employs TDMA along with variable interval multichannel scheduling for providing a reliable and efficient broadcast service over a lossy wireless medium. TM-MAC reduces transmission collisions thus making Control CHannel (CCH) more reliable and provides high throughput over Service CHannel (SCH) via maximum channel utilization. The scheduling strategy ensures that vehicles are assigned a slot instantaneously. Moreover there is a reduction of almost 50 % in number of vehicles incurring merging collisions when compared with VeMAC (Omar et al. in IEEE Trans Mob Comput 12(9):1724–1736, 2013), an existing and recently proposed TDMA based MAC protocol. This reduction in merging collisions increased the packet delivery ratio by almost 25 % when compared with VeMAC. Extensive simulations which were done over a realistic city scenario connote the superiority of TM-MAC over existing schemes for a wide range of traffic conditions.     

Rate allocation strategies for energy-efficient multipath routing in Ad-hoc networks towards B3G

Wireless mobile Ad-hoc network is a special network that all nodes can self-organize and work together. It is flexible to form a network and extend the coverage area dynamically without infrastructure, so Ad-hoc network is envisioned as cornerstones of future generation networking technologies (B3G or 4G). However, the dynamic network topology makes the communication cost not only the energy of source/destination nodes, but also the relay nodes. Another problem of the Ad-hoc network is it is hard to provide a stable and persistent quality of service (QoS), which is strongly required by the beyond 3rd generation (B3G) system. In this article, the authors establish a scenario that contains B3G cellular base station and Ad-hoc mobile nodes, and propose two algorithms minimum incremental rate algorithm and power feed-back rate allocation algorithm in multipath routing. The algorithms can maintain a constant total transmission rate and bit error ratio (BER) to provide the QoS guarantee and reach the minimum power consumption of the relay nodes by adjusting the rate of each path in the multipath routing.     

移动自组网路由恢复算法的研究

移动自组网是由一组带有无线收发装置的移动终端组成的自治通信系统.煤矿井下移动自组网可应用于矿井的监控管理系统、数据采集系统或者应急通信系统.移动自组网的路由方案主要包括表驱动(Proactive)和按需驱动(Reactive)两种,AODV是一种代表性的按需驱动算法.文中介绍了利用辅助路径基于AODV的一种矿井移动自组网的路由恢复算法,给出了辅助路由算法的性能测评方案.