移动Ad Hoc网络MAC协议及QoS保障机制研究
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摘要
介质访问控制(Medium Access Control,MAC)协议是Ad Hoc网络协议体系结构中的重要组成部分,主要用于协调节点访问共享信道,MAC协议能否高效地利用有限的无线资源对Ad Hoc网络的性能起决定性作用。另外随着各类多媒体业务和实时业务的普及和推广,要求网络在带宽、时延等方面提供保证,Ad Hoc网络的QoS问题已经成为当前研究的一个新的热点。在Ad Hoc网络中MAC层的功能是控制节点的报文传输,对无线媒体的占用,保证网络的整体性能,MAC子层处在协议栈的下层,是所有数据报文和控制消息在无线信道上进行发送和接收的直接控制者,它能否高效地使用无线信道是上层各种协议和机制所提供的QoS能否得到最终保障的一个关键因素。
本文从Ad Hoc网络的MAC协议入手,分析各种不同的MAC协议在AdHoc网络上的表现,将双信道传输与改进的握手协议相结合,设计实现了一个适用于多跳Ad Hoc网络的双信道MAC协议(DCMAC)。节点根据收到的不同控制包,在控制信道和数据信道中采用三种不同的预留方法,不仅解决了隐藏接收终端在单信道网络中不能同时接收数据的问题,还解决了暴露发送终端不能同时发送数据的问题,实现了数据信道的同时传输。通过性能分析可以看出,DCMAC协议的吞吐量属性比基于RTS/CTS的协议明显提高。本文分析了现有的Ad Hoc网络MAC层的QoS保障机制,针对目前基于区分服务的方法,结合802.11e的EDCF机制和改进的退避方法,利用双信道解决QoS保障问题。仿真结果表明,该方案能有效提高吞吐量和实时业务的服务质量。
Medium Access Control (MAC) protocol is an important part in the network protocol stack of Ad Hoc network, and it is mainly used to coordinate nodes to access the shared wireless channel. Whether MAC protocol can utilize the limited wireless resource plays a crucial role in Ad Hoc network performance. With the development of various multimedia services and real-time business, the network bandwidth and delay are required to provide a guarantee, the QoS has become a current research question as a new hot spot. At Ad Hoc network, the functions of MAC layer are that controlling node packet transmission, occupying wireless media and ensuring the overall performance of the network. MAC layer locates on the lower layer of protocol stack, controls packets to be sent and received in the channel, efficiently using the wireless channel is a key factor for that the upper range of protocol and mechanisms get Final protection.
On the basis of the MAC protocol, the performance of a variety of MAC protocol is analyzed in this dissertation for Ad Hoc network, Dual-channel and improved handshakes are integrated, design a medium access control (MAC) protocol called DCMAC (dual-channel MAC) for ad hoc networks. Based on receiving control packets, nodes use 3 different network allocation vectors (NAV) in control channel or data channel. The hidden terminal can receive data simultaneously and the exposed terminal can also transmit data. As can be seen through the performance analysis, a comparison with a RTS/CTS based protocol is given. The results show that the DCMAC protocol can improve the throughput. A detailed analysis is proposed on how to guarantee the quality of service at MAC layer in Ad Hoc network. As the technique based on DiffServ, combined the EDCF mechanism of 802.11e and the improved backoff method, using dual-channel to solve the QoS guarantee problem. The result of simulation proves the scheme can improve the throughput of network and the quality of serve for real-time traffic.
本文从Ad Hoc网络的MAC协议入手,分析各种不同的MAC协议在AdHoc网络上的表现,将双信道传输与改进的握手协议相结合,设计实现了一个适用于多跳Ad Hoc网络的双信道MAC协议(DCMAC)。节点根据收到的不同控制包,在控制信道和数据信道中采用三种不同的预留方法,不仅解决了隐藏接收终端在单信道网络中不能同时接收数据的问题,还解决了暴露发送终端不能同时发送数据的问题,实现了数据信道的同时传输。通过性能分析可以看出,DCMAC协议的吞吐量属性比基于RTS/CTS的协议明显提高。本文分析了现有的Ad Hoc网络MAC层的QoS保障机制,针对目前基于区分服务的方法,结合802.11e的EDCF机制和改进的退避方法,利用双信道解决QoS保障问题。仿真结果表明,该方案能有效提高吞吐量和实时业务的服务质量。
Medium Access Control (MAC) protocol is an important part in the network protocol stack of Ad Hoc network, and it is mainly used to coordinate nodes to access the shared wireless channel. Whether MAC protocol can utilize the limited wireless resource plays a crucial role in Ad Hoc network performance. With the development of various multimedia services and real-time business, the network bandwidth and delay are required to provide a guarantee, the QoS has become a current research question as a new hot spot. At Ad Hoc network, the functions of MAC layer are that controlling node packet transmission, occupying wireless media and ensuring the overall performance of the network. MAC layer locates on the lower layer of protocol stack, controls packets to be sent and received in the channel, efficiently using the wireless channel is a key factor for that the upper range of protocol and mechanisms get Final protection.
On the basis of the MAC protocol, the performance of a variety of MAC protocol is analyzed in this dissertation for Ad Hoc network, Dual-channel and improved handshakes are integrated, design a medium access control (MAC) protocol called DCMAC (dual-channel MAC) for ad hoc networks. Based on receiving control packets, nodes use 3 different network allocation vectors (NAV) in control channel or data channel. The hidden terminal can receive data simultaneously and the exposed terminal can also transmit data. As can be seen through the performance analysis, a comparison with a RTS/CTS based protocol is given. The results show that the DCMAC protocol can improve the throughput. A detailed analysis is proposed on how to guarantee the quality of service at MAC layer in Ad Hoc network. As the technique based on DiffServ, combined the EDCF mechanism of 802.11e and the improved backoff method, using dual-channel to solve the QoS guarantee problem. The result of simulation proves the scheme can improve the throughput of network and the quality of serve for real-time traffic.
引文
[1]Leiner B M,Nielson D L,Tobagi F A.Issues in Packet Radio Network Design[J].Proceedings IEEE,1987,75(1):6-20.
[2]Jubin J,Tornow J D.The DARPA packet radio network protocol[J].Proceedings of the IEEE,1987,75(1):21-32.
[3]王金龙等.Ad Hoc移动无线网络[M].国防工业出版社,2004.5.
[4]郑少仁,王海涛,赵志峰等.Ad Hoc网络技术[M].北京:人民邮电出版社,2005.
[5]英春,史美林.自组网体系结构研究[J].通信学报,1999,20(9):47-54.
[6]杨盘龙,郑少仁.Ad Hoc 网络中的路由算法[J].无线电工程,2001,31(9):46-50.
[7]Tobagi F A and Kleinrock L.Packet Switching in Radio Channels:Part II-The Hidden Terminal Problem in Carrier Sense Multiple-Access and the Busy-Tone Solution[C].IEEE Trans Communications,Desember 1975,COM-23:1417-1433.
[8]Karn P.MACA-A new channel access methed for packet radio[A].ARRL/CRRL Amateur Radio 9th Computer Networking Conference.1990:134-140.
[9]J eng,Haas Z J.Dual Busy Tone Multiple Access(DBTMA):a new medium access control for packet radio networks[C].Universal Personal Communications.1998.ICUPC'98.IEEE 1998 International Conference on,Florence,Italy,1998,10(2):973-977.
[10]Haas Z J,Deng J.Dual Busy Tone Multiple Access(DBTMA)-performance evaluation[C].Vehicular Technology Conference,IEEE 49th,Houston,TX.USA,1999,7(1):314-319.
[11]S.-L.Wu,C.-Y.Lin,Y.-C.Tseng and J.-P.Sheu.A new multi-channel MAC protocol withon-demand channel assignment for multi-hop mobile Ad Hoc networks[J].International Symposiumon Parallel Architectures,Algorithms and Networks(I-SPAN),2000,12:232-237.
[12]Bharghavan V.Demers A,Shenker S,et al MACAW:a media access protocol for wireless LANs[C].Proceeding of ACM SIGCOMM,London,United Kingdom,1994,8:212-25.
[13]F.Talucci and M.Gerla.MACA-BI(MACA By Invitation)A Wireless MAC Protocol for High Speed Ad Hoc Networking[A].Universal Personal Communications Record.1997 IEEE 6th International Conference. 1997:913-917.
[14]Tzamallukas Asimakis and Garcia-Luna-Aceves J.Receiver-Initiated Channel-Hopping for Ad-Hoc Network[C].IEEE 2nd IEEE Wireless Communications and Networking Conference,Chicago,Sep.2000IEEE:1262-1267.
[15]Garcia-Luna-Aceves J,Asimakis Tzamaloukas.Reversing the Collision-Avoidance Handshake in Wireless Networks[C].International Conference on Mobile Computing and Networking Mobicom '99,1999:120-130.
[16]Wireless LAN Medium Access Control(MAC) and Physical Specifications[S].IEEE std.802.11,IEEE 1999.
[17]Garcia-Luna-Aceves J.and Fullmer C.Floor Acquisition Multiple Access(FAMA) in Single-Channel Wireless Networks[J].ACM Mobile Networks and Application Journal,Special Issue on Ad-Hoc Networks,1999.4:157-174
[18]Fullmer C and Garcia-Luna-Aceves J.Floor Acquisition Multiple Access for Packet-Radio Networks[C].Proc.ACM SIGCOMM 95,Cambridge,MA.1995,10(25):262-273.
[19]Bharghavan V.Performance Analysis of a Medium Access Protocol for Wireless Packet Networks[J].Wireless Networks,2004,9(1O):519-529.
[20]J eng,Haas Z J.Dual Busy Tone Multiple Access(DBTMA):a new medium access control for packet radio networks[C].Universal Personal Communications,1998.ICUPC'98.IEEE 1998 International Conference on.Florence,Italy,1998,10(2):973-977.
[21]Haas Z J,Deng J.Dual Busy Tone Multiple Access(DBTMA)-performance evaluation[C].Vehicular Technology Conference,1999 IEEE 49th,Houston,TX,USA,1999,7(1):314-319.
[22]Tang Z and Garcia-Luna-Aceves J Hop-Reservation Multiple Access(HRMA)for Ad-Hoc Networks.IEEE INFOCOM、1999.
[23]So J,Vaidya N.A Multi-channel MAC Protocol for Ad Hoc Wireless Networks[C].Dept of electrical and Computer Engineering,Univetsity of Illinois,USA,Technical Report,January 2003,1(2):211-217.
[24]李腊元,李春林.计算机网络技术[M].北京:国防工业出版社,2004.7
[25]谢希仁.计算机网络(第四版)[M].北京:电子工业出版社,2003.6
[26][美]William Stallings著,齐望东等译.高速网络与互联网—性能与服务质量[M].北京:电子工业出版社,2003.1
[27]林闯,单志广,任丰原.计算机网络的服务质量(QoS)[M].北京:清华大学出版社,2004.4
[28]E.Crawley,R.Nair,B.Rajagopalan and H.Sandick.A Framework for QoS-based Routing in the Internet RFC2386[S],1998,8
[29]A.Striegel and G.Manimaran.A Survey of QoS Multicasting Issues[J].IEEE Communications Magzine,2002,(6):82-87
[30]Ray Hunt,Senior Lecturer.A Review of Quality of Service Mechanisms in IP-based Networks-Intergrated and Differentiated Services[C],Multi-layer Switching,MPLS and Traffic Engineering.Computer Communication.2002.25(1):100-108
[31]S.Blake,D.Black,M.Carlson,E.Davies,Z.Wang and W.Weiss.An Architecture for Differentiated Services.RFC2475[S],1998,11
[32]R.Braden,L.Zhang,S.Berson et al.Resource Reservation Protocol(RSVP)(Versionl):Function Specification.JETF RFC2205[S].September 1997
[33]郑相全等.无线自组网实用教程[M].北京:清华大学出版社,2004.6
[34]于宏毅等.无线移动自组织网[M].北京:人民邮电出版社,2005.4
[35]王晓梅,于宏毅,冉崇森.移动自组织网络QoS研究[J].电信科学,2005,14(8):46-51
[36]王海涛,刘晓明.INSIGNIA带内信令机制及其改进措施[J],数据通信,2004,16(4):11-14
[37]王海涛,郑少仁,宋丽华.Ad Hoc网络中QoS保障机制的研究[J].通信学报,2002,23(10):114-120
[38]王海涛.Ad Hoc网络中的QoS路由算法[J].现代有线传输,2003,9(3):58-62
[39]乔艳涛,余松煜.移动Ad Hoc网的QoS保障[J].南京邮电学院学报,2005,25(5):35-39
[40]李云,赵为粮,隆克平,吴诗其.无线Ad Hoc网络支持QoS的研究进展与展望[J].软件学报,2004,15(12):1885-1892
[41]Hannan Xiao,W.Seah,A.Lo and K.C.Chua.A flexible quality of service model for mobile ad-hoc networks[C].Vehicular Technology Conference Proceedings,Tokyo,Juanary,2000,pp.445-449
[42]Lee S-B.INSIGNIA:An IP-based quality of service framework for mobile Ad hoc networks.Journal of Parallel and Dist[J].Comp.Special issue on Wireless and Mobile Computing and Communications,2000,60(4):374-406
[43]姚尹雄,王豪行.MAQF:一种新的移动Ad Hoc网络自适应QoS结构框架[J].电子学报,2002,30(5):727-730
[44]AAD I,CASTELLUCCIA C.Differentiation mechanisms for IEEE 802.11[A].Twentieth Annual Joint Conference of the IEEE Computer and Communications Societies Proceedings[C].Anchorage,Alaska,USA,2001.
[45]HE Da-Jiang,SHEN C Q.Simulation Study of IEEE 802.11e EDCF.57th IEEE Semiannual[C].2003:685-689.
[46]XIAO Yang.Enhanced DCF of IEEE 802.11e to support QoS[J].Wireless Communications and Networking,2003,12(2):1291-1296.
[47]XIAO Yang.IEEE 802.11e:QoS provisioning at the MAC layer[J].IEEE Personal Communications.2004,11(3):72-79.
[48]BANCHS A,PEREZ X.Providing throughput guarantees in IEEE 802.11 W irelessLAN[A].Pro.WCNC[C].2002.
[49]BANCHS A,PEREZ X.D istributed weighted fair queuing in 802.11 wireless LAN[A].Proc.IEEE ICC[C].2002.
[50]LAMIA Romdhani,Q IANG Ni,THIERRY Turletti Adaptive EDCF:enhanced service differentiation for IEEE 802.11 wireless ad hoc networks[J].W ireless Communications andNetworking,2003,(2):1373-1378.
[51]IEEE WG0-2002.802.11e Draft 3.1[S].
[52]IEEE standard for wireless LAN medium access control(MAC)and physical layer(PHY)specifications[S].IEEE Standard 802.11,1997.
[53]MUQATTASH A,KRUNZ M.Power controlled dual channel(PCDC)medium access protocol for wireless ad hoc networks.Proc INFOCOM[C].2003:470-480.
[54]ZHAO Z F,ZHENG S R.Dual channel based ad hoc network channel access protocol[C].IEEEConf Personal Mobile Communications.2003:32-36.
[55]TAKAGI H,KLEINROCKL.Optimal transmission range for randomly distributed Packet radio terminals[J].IEEE Trans on Commun,1984.3(32):246-257.
[56]WANG Y,GARCIA2LUNA2ACEVES J J.Performance of collision avoidarlce protocols in single2channel ad hoc networks[C]//Proc ICNP'02.2002:68-77.
[57]徐雷鸣,庞博,赵耀.NS与网络模拟[M].北京:人民邮电出版社,2003.
[2]Jubin J,Tornow J D.The DARPA packet radio network protocol[J].Proceedings of the IEEE,1987,75(1):21-32.
[3]王金龙等.Ad Hoc移动无线网络[M].国防工业出版社,2004.5.
[4]郑少仁,王海涛,赵志峰等.Ad Hoc网络技术[M].北京:人民邮电出版社,2005.
[5]英春,史美林.自组网体系结构研究[J].通信学报,1999,20(9):47-54.
[6]杨盘龙,郑少仁.Ad Hoc 网络中的路由算法[J].无线电工程,2001,31(9):46-50.
[7]Tobagi F A and Kleinrock L.Packet Switching in Radio Channels:Part II-The Hidden Terminal Problem in Carrier Sense Multiple-Access and the Busy-Tone Solution[C].IEEE Trans Communications,Desember 1975,COM-23:1417-1433.
[8]Karn P.MACA-A new channel access methed for packet radio[A].ARRL/CRRL Amateur Radio 9th Computer Networking Conference.1990:134-140.
[9]J eng,Haas Z J.Dual Busy Tone Multiple Access(DBTMA):a new medium access control for packet radio networks[C].Universal Personal Communications.1998.ICUPC'98.IEEE 1998 International Conference on,Florence,Italy,1998,10(2):973-977.
[10]Haas Z J,Deng J.Dual Busy Tone Multiple Access(DBTMA)-performance evaluation[C].Vehicular Technology Conference,IEEE 49th,Houston,TX.USA,1999,7(1):314-319.
[11]S.-L.Wu,C.-Y.Lin,Y.-C.Tseng and J.-P.Sheu.A new multi-channel MAC protocol withon-demand channel assignment for multi-hop mobile Ad Hoc networks[J].International Symposiumon Parallel Architectures,Algorithms and Networks(I-SPAN),2000,12:232-237.
[12]Bharghavan V.Demers A,Shenker S,et al MACAW:a media access protocol for wireless LANs[C].Proceeding of ACM SIGCOMM,London,United Kingdom,1994,8:212-25.
[13]F.Talucci and M.Gerla.MACA-BI(MACA By Invitation)A Wireless MAC Protocol for High Speed Ad Hoc Networking[A].Universal Personal Communications Record.1997 IEEE 6th International Conference. 1997:913-917.
[14]Tzamallukas Asimakis and Garcia-Luna-Aceves J.Receiver-Initiated Channel-Hopping for Ad-Hoc Network[C].IEEE 2nd IEEE Wireless Communications and Networking Conference,Chicago,Sep.2000IEEE:1262-1267.
[15]Garcia-Luna-Aceves J,Asimakis Tzamaloukas.Reversing the Collision-Avoidance Handshake in Wireless Networks[C].International Conference on Mobile Computing and Networking Mobicom '99,1999:120-130.
[16]Wireless LAN Medium Access Control(MAC) and Physical Specifications[S].IEEE std.802.11,IEEE 1999.
[17]Garcia-Luna-Aceves J.and Fullmer C.Floor Acquisition Multiple Access(FAMA) in Single-Channel Wireless Networks[J].ACM Mobile Networks and Application Journal,Special Issue on Ad-Hoc Networks,1999.4:157-174
[18]Fullmer C and Garcia-Luna-Aceves J.Floor Acquisition Multiple Access for Packet-Radio Networks[C].Proc.ACM SIGCOMM 95,Cambridge,MA.1995,10(25):262-273.
[19]Bharghavan V.Performance Analysis of a Medium Access Protocol for Wireless Packet Networks[J].Wireless Networks,2004,9(1O):519-529.
[20]J eng,Haas Z J.Dual Busy Tone Multiple Access(DBTMA):a new medium access control for packet radio networks[C].Universal Personal Communications,1998.ICUPC'98.IEEE 1998 International Conference on.Florence,Italy,1998,10(2):973-977.
[21]Haas Z J,Deng J.Dual Busy Tone Multiple Access(DBTMA)-performance evaluation[C].Vehicular Technology Conference,1999 IEEE 49th,Houston,TX,USA,1999,7(1):314-319.
[22]Tang Z and Garcia-Luna-Aceves J Hop-Reservation Multiple Access(HRMA)for Ad-Hoc Networks.IEEE INFOCOM、1999.
[23]So J,Vaidya N.A Multi-channel MAC Protocol for Ad Hoc Wireless Networks[C].Dept of electrical and Computer Engineering,Univetsity of Illinois,USA,Technical Report,January 2003,1(2):211-217.
[24]李腊元,李春林.计算机网络技术[M].北京:国防工业出版社,2004.7
[25]谢希仁.计算机网络(第四版)[M].北京:电子工业出版社,2003.6
[26][美]William Stallings著,齐望东等译.高速网络与互联网—性能与服务质量[M].北京:电子工业出版社,2003.1
[27]林闯,单志广,任丰原.计算机网络的服务质量(QoS)[M].北京:清华大学出版社,2004.4
[28]E.Crawley,R.Nair,B.Rajagopalan and H.Sandick.A Framework for QoS-based Routing in the Internet RFC2386[S],1998,8
[29]A.Striegel and G.Manimaran.A Survey of QoS Multicasting Issues[J].IEEE Communications Magzine,2002,(6):82-87
[30]Ray Hunt,Senior Lecturer.A Review of Quality of Service Mechanisms in IP-based Networks-Intergrated and Differentiated Services[C],Multi-layer Switching,MPLS and Traffic Engineering.Computer Communication.2002.25(1):100-108
[31]S.Blake,D.Black,M.Carlson,E.Davies,Z.Wang and W.Weiss.An Architecture for Differentiated Services.RFC2475[S],1998,11
[32]R.Braden,L.Zhang,S.Berson et al.Resource Reservation Protocol(RSVP)(Versionl):Function Specification.JETF RFC2205[S].September 1997
[33]郑相全等.无线自组网实用教程[M].北京:清华大学出版社,2004.6
[34]于宏毅等.无线移动自组织网[M].北京:人民邮电出版社,2005.4
[35]王晓梅,于宏毅,冉崇森.移动自组织网络QoS研究[J].电信科学,2005,14(8):46-51
[36]王海涛,刘晓明.INSIGNIA带内信令机制及其改进措施[J],数据通信,2004,16(4):11-14
[37]王海涛,郑少仁,宋丽华.Ad Hoc网络中QoS保障机制的研究[J].通信学报,2002,23(10):114-120
[38]王海涛.Ad Hoc网络中的QoS路由算法[J].现代有线传输,2003,9(3):58-62
[39]乔艳涛,余松煜.移动Ad Hoc网的QoS保障[J].南京邮电学院学报,2005,25(5):35-39
[40]李云,赵为粮,隆克平,吴诗其.无线Ad Hoc网络支持QoS的研究进展与展望[J].软件学报,2004,15(12):1885-1892
[41]Hannan Xiao,W.Seah,A.Lo and K.C.Chua.A flexible quality of service model for mobile ad-hoc networks[C].Vehicular Technology Conference Proceedings,Tokyo,Juanary,2000,pp.445-449
[42]Lee S-B.INSIGNIA:An IP-based quality of service framework for mobile Ad hoc networks.Journal of Parallel and Dist[J].Comp.Special issue on Wireless and Mobile Computing and Communications,2000,60(4):374-406
[43]姚尹雄,王豪行.MAQF:一种新的移动Ad Hoc网络自适应QoS结构框架[J].电子学报,2002,30(5):727-730
[44]AAD I,CASTELLUCCIA C.Differentiation mechanisms for IEEE 802.11[A].Twentieth Annual Joint Conference of the IEEE Computer and Communications Societies Proceedings[C].Anchorage,Alaska,USA,2001.
[45]HE Da-Jiang,SHEN C Q.Simulation Study of IEEE 802.11e EDCF.57th IEEE Semiannual[C].2003:685-689.
[46]XIAO Yang.Enhanced DCF of IEEE 802.11e to support QoS[J].Wireless Communications and Networking,2003,12(2):1291-1296.
[47]XIAO Yang.IEEE 802.11e:QoS provisioning at the MAC layer[J].IEEE Personal Communications.2004,11(3):72-79.
[48]BANCHS A,PEREZ X.Providing throughput guarantees in IEEE 802.11 W irelessLAN[A].Pro.WCNC[C].2002.
[49]BANCHS A,PEREZ X.D istributed weighted fair queuing in 802.11 wireless LAN[A].Proc.IEEE ICC[C].2002.
[50]LAMIA Romdhani,Q IANG Ni,THIERRY Turletti Adaptive EDCF:enhanced service differentiation for IEEE 802.11 wireless ad hoc networks[J].W ireless Communications andNetworking,2003,(2):1373-1378.
[51]IEEE WG0-2002.802.11e Draft 3.1[S].
[52]IEEE standard for wireless LAN medium access control(MAC)and physical layer(PHY)specifications[S].IEEE Standard 802.11,1997.
[53]MUQATTASH A,KRUNZ M.Power controlled dual channel(PCDC)medium access protocol for wireless ad hoc networks.Proc INFOCOM[C].2003:470-480.
[54]ZHAO Z F,ZHENG S R.Dual channel based ad hoc network channel access protocol[C].IEEEConf Personal Mobile Communications.2003:32-36.
[55]TAKAGI H,KLEINROCKL.Optimal transmission range for randomly distributed Packet radio terminals[J].IEEE Trans on Commun,1984.3(32):246-257.
[56]WANG Y,GARCIA2LUNA2ACEVES J J.Performance of collision avoidarlce protocols in single2channel ad hoc networks[C]//Proc ICNP'02.2002:68-77.
[57]徐雷鸣,庞博,赵耀.NS与网络模拟[M].北京:人民邮电出版社,2003.