车载Ad Hoc网络MAC协议退避算法的研究
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摘要
随着无线通信技术以及汽车工业的迅速发展,车载无线自组织网络技术(Vehicular Ad Hoc Network, VANET)已经成为人们研究的一个热点,VANET是一种特殊的移动自组织网络技术,它是未来智能交通系统的基础之一。车载无线通信网络是由车与车以及车与路边的基础设施之间的相互通信来构成,这样能够为驾驶者提供一系列的服务,如：Internet的接入,实时导航以及车载娱乐等,另外还能提供事故告警等信息,使交通网络更高效、安全。本文在研究移动Ad Hoc网络(Mobile Ad Hoc Networks, MANET)的MAC协议基础上进一步研究了VANET的MAC层协议的关键技术,主要贡献如下：
第一,在二进制指数退避算法(Binary Exponential Backoff, BEB)的基础上,研究乘性增加线性减少退避算法(Multiple Increase Linear Decrease,指数增加指数减少退避算法(Exponential Increase Exponential Decrease, EIED),并在NS2软件平台上对上述三种算法进行仿真,比较其公平性,然后对后两种算法进行优化分别得到newMILD、newEIED退避算法,以提高网络的性能。并在newMILD算法的基础上进一步改进得到一种基于统计次数的退避算法,即当节点连续发送数据成功时,竞争窗口本应该减小,但是为了使竞争失败的节点接入信道,算法设定了一个门限值,当节点连续发送数据成功的次数超过此值时竞争窗口就变为最大,同理,当节点连续发送数据失败次数超过此值时,竞争窗口就降为最小。通过仿真分析,证明了此算法能够有效的降低隐藏节点的影响,提高了节点接入信道的公平性。
第二,根据节点运动的特性,提出一种可用于评估车载网络冲突概率的模型,并仿真验证车载网络节点冲突概率与节点移动速度以及网络节点数量有关。然后提出一种基于相对距离的退避算法,本算法是基于相对距离和节点接入信道优先级成比例的基础上提出的。即节点根据自己与一跳邻居节点距离平均值的相对变化比例来调整竞争窗口的值。并利用Vanetmobisim软件模拟城市车辆运动场景图,然后利用其生成的脚本文件和cbrgen工具编写脚本代码来生成在NS2下的对应的场景图以实现仿真,仿真结果表明此算法能够有效的改善网络的性能。
With the rapid development of wireless communication technology and the auto industry, Vehicular Ad Hoc Network has already become a hot topic of academic research, VANET is a particular kind of self-organizing network, which is the foundation of future intelligent transportation system. It communicates through Inter-vehicle (IVC) and Vehicle to Roadside (RVC). So that it can provide series of service for drivers. Such as Internet access, Real-time navigation and in-car entertainment, etc. In addition to that, it can provide the accident alarm information, so that it can make the traffic network more efficient and safer. This paper mainly researches the key technology of the VANET MAC layer protocol; the main contributions are as follows:
First, MILD and EIED are researched on the basis of BEB, then the three kinds of algorithm are simulated with NS2and the fairness is compared. In order to improve network performance the latter two algorithms are optimized. And on the basis of newMILD a backoff algorithm which based on the statistical number are proposed. That is when the node sends success, the window of contention should be reduced, But in order to make the competition failed node could access channel, the algorithm sets a threshold value. When the number of nodes succeeding to send continuously is greater than the value, the contention window becomes the largest. Similarly, when the numbers of nodes failing to send continuously is greater than this value, the contention window will reduce to the minimum. Through the analysis of simulation, it is proved that the algorithm is effective to reduce the influence of hidden nodes and it has improved the fairness of node to access channel.
Second, on the basis of the mobility characteristics of nodes, a model used to evaluate the VANET are proposed, and through simulating it has proved that the VANET node collision is based on the nodes speed and the number of the nodes. Then a backoff algorithm which is based on the relative distance is proposed. The algorithm is based on the relative distance and node access channel proportionally. It adjust the value of the contention window according to the average relative change of the distance that the node with it's neighbor node. And city vehicle motion scene graph has been simulated using VanetMobiSim software, then the paper used the script that have generated and script made by cbrgen to generate scene in NS2. The simulation results show that the algorithm is effective to improve the preferment of network.
第一,在二进制指数退避算法(Binary Exponential Backoff, BEB)的基础上,研究乘性增加线性减少退避算法(Multiple Increase Linear Decrease,指数增加指数减少退避算法(Exponential Increase Exponential Decrease, EIED),并在NS2软件平台上对上述三种算法进行仿真,比较其公平性,然后对后两种算法进行优化分别得到newMILD、newEIED退避算法,以提高网络的性能。并在newMILD算法的基础上进一步改进得到一种基于统计次数的退避算法,即当节点连续发送数据成功时,竞争窗口本应该减小,但是为了使竞争失败的节点接入信道,算法设定了一个门限值,当节点连续发送数据成功的次数超过此值时竞争窗口就变为最大,同理,当节点连续发送数据失败次数超过此值时,竞争窗口就降为最小。通过仿真分析,证明了此算法能够有效的降低隐藏节点的影响,提高了节点接入信道的公平性。
第二,根据节点运动的特性,提出一种可用于评估车载网络冲突概率的模型,并仿真验证车载网络节点冲突概率与节点移动速度以及网络节点数量有关。然后提出一种基于相对距离的退避算法,本算法是基于相对距离和节点接入信道优先级成比例的基础上提出的。即节点根据自己与一跳邻居节点距离平均值的相对变化比例来调整竞争窗口的值。并利用Vanetmobisim软件模拟城市车辆运动场景图,然后利用其生成的脚本文件和cbrgen工具编写脚本代码来生成在NS2下的对应的场景图以实现仿真,仿真结果表明此算法能够有效的改善网络的性能。
With the rapid development of wireless communication technology and the auto industry, Vehicular Ad Hoc Network has already become a hot topic of academic research, VANET is a particular kind of self-organizing network, which is the foundation of future intelligent transportation system. It communicates through Inter-vehicle (IVC) and Vehicle to Roadside (RVC). So that it can provide series of service for drivers. Such as Internet access, Real-time navigation and in-car entertainment, etc. In addition to that, it can provide the accident alarm information, so that it can make the traffic network more efficient and safer. This paper mainly researches the key technology of the VANET MAC layer protocol; the main contributions are as follows:
First, MILD and EIED are researched on the basis of BEB, then the three kinds of algorithm are simulated with NS2and the fairness is compared. In order to improve network performance the latter two algorithms are optimized. And on the basis of newMILD a backoff algorithm which based on the statistical number are proposed. That is when the node sends success, the window of contention should be reduced, But in order to make the competition failed node could access channel, the algorithm sets a threshold value. When the number of nodes succeeding to send continuously is greater than the value, the contention window becomes the largest. Similarly, when the numbers of nodes failing to send continuously is greater than this value, the contention window will reduce to the minimum. Through the analysis of simulation, it is proved that the algorithm is effective to reduce the influence of hidden nodes and it has improved the fairness of node to access channel.
Second, on the basis of the mobility characteristics of nodes, a model used to evaluate the VANET are proposed, and through simulating it has proved that the VANET node collision is based on the nodes speed and the number of the nodes. Then a backoff algorithm which is based on the relative distance is proposed. The algorithm is based on the relative distance and node access channel proportionally. It adjust the value of the contention window according to the average relative change of the distance that the node with it's neighbor node. And city vehicle motion scene graph has been simulated using VanetMobiSim software, then the paper used the script that have generated and script made by cbrgen to generate scene in NS2. The simulation results show that the algorithm is effective to improve the preferment of network.
引文
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[3]Reichardt D, Miglietta M, Moretti L, et al. CarTALK 2000:Safe and comfortable driving based upon inter-vehicle-communication[C]//Intelligent Vehicle Symposium,2002. IEEE. IEEE,2002,2:545-550.
[4]Festag A, FuBler H, Hartenstein H, et al. Fleetnet:Bringing car-to-car communication into the real world [J]. Computer,2004,4(L15):16.
[5]Hartenstein H, Laberteaux K P. A tutorial survey on vehicular ad hoc networks [J]. Communications Magazine, IEEE,2008,46(6):164-171.
[6]王金龙,王呈贵,吴启晖Ad Hoc移动无线网络[M].国防科技出版社.2004：16-20.
[7]郑少仁,王海涛,赵志峰,米志超,黎宁Ad Hoc网络技术[M],人民邮电出版社.1996：8-15.
[8]Andrew S.Tanenbaum著,潘爱民译.计算机网络(第4版)[M].清华大学出版社,2004：212-216
[9]刘军.无线白组网MAC协议及路由算法研究[D].电子科技大学硕士论文,2007.
[10]李云,隆克平,吴诗其,等IEEE 802.11 DCF性能分析及改进[J].电子学报,2003,31(10)：1446-1451.
[11]吴笑萍Ad hoc网络隐藏／暴露终端问题的研究[J].微计算机信息,2006,22(03)：35-37.
[12]Gerla M. Ad Hoc Networks [M]. Springer US,2005:1-22.
[13]王磊,张慧慧,李开生.信道接入协议的网络仿真技术研究[J].计算机应用,2006,26(8)：1782-1784.
[14]王勇,胡以华.时隙ALOHA系统稳定性分析[J].计算机应用研究,2008,25(4)：1175-1177.
[15]Ziouva E, Antonakopoulos T. CSMA/CA performance under high traffic conditions:throughput and delay analysis [J]. Computer Communications, 2002,25(3):313-321.
[16]盛敏.移动Ad Hoc网络关键技术研究[D].西安电子科技大学硕士论文,2003.
[17]罗志锋,徐洪刚,何山.车路互联网的底层协议-802.11 p标准[J].电子质量,2011(11)：45-50.
[18]Xu Q, Mak T, Ko J, et al. Vehicle-to-vehicle safety messaging in DSRC [C]// Proceedings of.the 1st ACM international workshop on Vehicular ad hoc networks. ACM,2004:19-28.
[19]Menouar H, Filali F, Lenardi M. A survey and qualitative analysis of MAC protocols for vehicular ad hoc networks [J]. Wireless Communications, IEEE, 2006,13(5):30-35.
[20]Yadumurthy R M, Sadashivaiah M, Makanaboyina R. Reliable MAC broad-cast protocol in directional and omni-directional transmissions for vehicular ad hoc networks[C]//Proceedings of the 2nd ACM international workshop on Vehicular ad hoc networks. ACM,2005:10-19.
[21]Chen X, Refai H H. SDMA:On the suitability for VANET[C]//Information and Communication Technologies:From Theory to Applications,2008. ICTTA 2008.3rd International Conference on. IEEE,2008:1-5.
[22]Wu J, Stojmenovic I. Ad hoc networks [J]. COMPUTER-IEEE COMPUTER SOCIETY-,2004,37(2):29-31.
[23]Korkmaz G, Ekici E, Ozgiiner F, et al. Urban multi-hop broadcast protocol for inter-vehicle communication systems[C]//Proceedings of the 1st ACM international workshop on Vehicular ad hoc networks. ACM,2004:76-85.
[24]Bianchi G. Performance Analysis of the IEEE802.11 Distributed Coordination Function. IEEEJSAC[J],2000,18(3):535-547
[25]Jung E S, Vaidya N H. A power control MAC protocol for ad hoc networks [J]. Wireless Networks,2005,11(1-2):55-66.
[26]Song N O, Kwak B J, Song J, et al. Enhancement of IEEE 802.11 distributed coordination function with exponential increase exponential decrease backoff algorithm[C]//Vehicular Technology Conference,2003. VTC 2003-Spring. The 57th IEEE Semiannual. IEEE,2003,4:2775-2778.
[27]Wu C, Feng J, Fan P. On a new queue backoff fair algorithm for ad hoc net-works[C]//Parallel and Distributed Computing, Applications and Technolo-gies,2003. PDCAT'2003. Proceedings of the Fourth International Conference on. IEEE,2003:335-339.
[28]网络论坛http://www.netforum.com.cn/
[29]方旭明.移动Ad Hoc网络研究与发展现状[J].数据通信,2003,4(17.20)：25.
[30]杨仁忠,侯紫峰.基于AP预先转发的802.11无线局域网切换机制研究[J].计算机研究与发展,2004,41(8)：1376-1381.
[31]Perkins C E. Ad hoc networking [M]. Reading:Addison-Wesley,2001.
[32]Alasmary W, Zhuang W. Mobility impact in IEEE 802.11 p infrastructureless vehicular networks [J]. Ad Hoc Networks,2012,10(2):222-230.
[33]吴传霞,范平志,冯军焕.一种Ad Hoc网络信道接入排队退避公平算法[J].系统仿真学报,2004,16(5)：1111-1114.
[34]吴华,张晓敏.无线Ad Hoc网的公平性问题[J].信息技术与信息化,2004,4：005.
[35]王春江,耿方萍,刘元安,等.一种应用于Ad hoc无线局域网的随机接入协议[J].电子学报,2005,33(1)：26-31.
[36]秦冀,姜雪松.移动IP技术与NS-2模拟[M].机械工业出版社,2006.
[37]Bilstrup K. A survey regarding wireless communication standards intended for a high-speed vehicle environment [J]. Pervasive Computing, IEEE,2007: 12-16.
[38]Eichler S. Performance evaluations of the IEEE 802.11 p WAVE communi-cation standard[C]//Vehicular Technology Conference,2007. VTC-2007 Fall. 2007 IEEE 66th. IEEE,2007:2199-2203.
[39]Choi N, Choi S, Seok Y, et al. A solicitation-based IEEE 802.11 p MAC protocol for roadside to vehicular networks[C]//2007 Mobile Networking for Vehicular Environments. IEEE,2007:91-96.
[40]Wang Y, Ahmed A, Krishnamachari B, et al. IEEE 802.11 p performance evaluation and protocol enhancement[C]//Vehicular Electronics and Safety, 2008. ICVES 2008. IEEE International Conference on. IEEE,2008:317-322.
[41]Cali F, Conti M, Gregori E. Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit[J]. Networking, IEEE/ACM Transac-tions on,2000,8(6):785-799.
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