对VoWLAN技术的MAC研究与改进
摘要
WLAN，作为一种无线接入网络，在许多场合下正扮演着越来越重要的角色，在WLAN中传输语音，视频等实时业务的需求也日益增加，所以IEEE定义了802.11e协议，其通过对WLAN接入机制的改善，以至达到对业务的QoS的支持；对QoS支持对多媒体来说是至关重要的，比如视频和音频，他们需要非常好的带宽，延时和抖动。
802.11e的研究是本文的重点，在本文中，作者在原来的EDCA协议上的提出改进的EDCA(DEDCA)协议，DEDCA能根据网络的性能动态地接入，使MAC更适合Voice Over WLAN。并在OPNET没有EDCA模块的情况下，通过编写C语言程序，通过OPNET工具的仿真，理论上验证了DEDCA协议的改进的正确性。
首先，介绍了无线局域网标准和无线局域网QoS的相关情况；介绍了DCF机制，对DCF和PCF进行理论分析，并且对DCF进行了仿真，分析了影响节点的吞吐量和延时的参数，指出了DCF在高负载的情况下对业务没有QoS的保证；引入对业务的QoS有保证的802.11e协议，802.11e是对各种业务分配优先等级，在本文中对802.11e的EDCA接入机制进行了分析，就单个节点吞吐量进行了理论数值分析，得到了吞吐量和退避窗口的关系，对802.11e用OPNET对其仿真，并且比较了EDCA和DCF的性能，EDCA在“牺牲”数据的基础对视频和音频的QoS比DCF更有保证，指出了EDCA在保证QoS的基础上的不公平性；最后，提出了一种适合VoWLAN技术DEDCA接入机制，引入了信道状态CS因子，提出了基于信道状态的动态的退避窗口机制和一种新的退避方式。确立了退避窗户最大值和最小值的与信道关系的公式，确立了退避方式阀值的公式，最后通过进行了仿真，DEDCA不但对视频和音频有QoS保证，整个信道的性能都提商了，验证了DEDCA的正确性和适合在VoWLAN技术中的应用。
Wireless network, as an access technology, is playing a more and more important role in many occasions, the requirements to transmit real-time traffic such as voice, video is increasing in VoWLAN, and so IEEE developed 802.11e based on 802.11. The protocol can improve mechanism of WLAN access to supports quality of service of voice (QoS) and video real-time traffic. Real-time services such as audio and videoconferences mean requirment some specified bandwidth, delay and jitter guarantee.
This thesis pay attention to 802.11e mainly, According to access mechine of EDCA (Enhance DCF) in the protocol of 802.11e, author is putting forward improved DEDCA (Dynamic Enhance DCF) mechanism, the mechanism let net-nodes dynamic access based on performance of network in WLAN. There is not EDCA moduling in simulative softwar OPNET Modeler, author buildes modeling of EDCA using program c and proves validity of DEDCA theoretically by simulation experments.
At first, the standard of wireless LAN, the QoS of WLAN, and DCF are introduced, and DCF is simulated by OPNET, the parameter of throughput and delay are analyzed, which effect the network performance, anthor point out the shortcoming when it apply to real-time traffic, 802. 11e is imported,which set tup the priority ranks of traffics and can guarantee the QoS of Voice and Vedio. In the thesis, 802.11e and EDCA access mechanism is investigated, Analyses on throughput of any net-node theoretically, has attained the connection betwixt throughout and back-off windows, then, EDCA is simulated by OPNET, and the performance of EDCA and DCF are compared. EDCA can guarantee QoS of real-time traffics by impropriation the channel of Data.
Then, VoWLAN is presented simply, has brought forward DEDCA access mechanism, which adapt to VoWLAN technology, this mechanism has imported channel estate CS, dynamic back-off window and a new back-off way . The formula of back-off valve value and relation betwixt channel estate and the value of
back-off windows are found, then, proving the validity of DEDCA which adapt to VoWLAN technology by simulation.
802.11e的研究是本文的重点，在本文中，作者在原来的EDCA协议上的提出改进的EDCA(DEDCA)协议，DEDCA能根据网络的性能动态地接入，使MAC更适合Voice Over WLAN。并在OPNET没有EDCA模块的情况下，通过编写C语言程序，通过OPNET工具的仿真，理论上验证了DEDCA协议的改进的正确性。
首先，介绍了无线局域网标准和无线局域网QoS的相关情况；介绍了DCF机制，对DCF和PCF进行理论分析，并且对DCF进行了仿真，分析了影响节点的吞吐量和延时的参数，指出了DCF在高负载的情况下对业务没有QoS的保证；引入对业务的QoS有保证的802.11e协议，802.11e是对各种业务分配优先等级，在本文中对802.11e的EDCA接入机制进行了分析，就单个节点吞吐量进行了理论数值分析，得到了吞吐量和退避窗口的关系，对802.11e用OPNET对其仿真，并且比较了EDCA和DCF的性能，EDCA在“牺牲”数据的基础对视频和音频的QoS比DCF更有保证，指出了EDCA在保证QoS的基础上的不公平性；最后，提出了一种适合VoWLAN技术DEDCA接入机制，引入了信道状态CS因子，提出了基于信道状态的动态的退避窗口机制和一种新的退避方式。确立了退避窗户最大值和最小值的与信道关系的公式，确立了退避方式阀值的公式，最后通过进行了仿真，DEDCA不但对视频和音频有QoS保证，整个信道的性能都提商了，验证了DEDCA的正确性和适合在VoWLAN技术中的应用。
Wireless network, as an access technology, is playing a more and more important role in many occasions, the requirements to transmit real-time traffic such as voice, video is increasing in VoWLAN, and so IEEE developed 802.11e based on 802.11. The protocol can improve mechanism of WLAN access to supports quality of service of voice (QoS) and video real-time traffic. Real-time services such as audio and videoconferences mean requirment some specified bandwidth, delay and jitter guarantee.
This thesis pay attention to 802.11e mainly, According to access mechine of EDCA (Enhance DCF) in the protocol of 802.11e, author is putting forward improved DEDCA (Dynamic Enhance DCF) mechanism, the mechanism let net-nodes dynamic access based on performance of network in WLAN. There is not EDCA moduling in simulative softwar OPNET Modeler, author buildes modeling of EDCA using program c and proves validity of DEDCA theoretically by simulation experments.
At first, the standard of wireless LAN, the QoS of WLAN, and DCF are introduced, and DCF is simulated by OPNET, the parameter of throughput and delay are analyzed, which effect the network performance, anthor point out the shortcoming when it apply to real-time traffic, 802. 11e is imported,which set tup the priority ranks of traffics and can guarantee the QoS of Voice and Vedio. In the thesis, 802.11e and EDCA access mechanism is investigated, Analyses on throughput of any net-node theoretically, has attained the connection betwixt throughout and back-off windows, then, EDCA is simulated by OPNET, and the performance of EDCA and DCF are compared. EDCA can guarantee QoS of real-time traffics by impropriation the channel of Data.
Then, VoWLAN is presented simply, has brought forward DEDCA access mechanism, which adapt to VoWLAN technology, this mechanism has imported channel estate CS, dynamic back-off window and a new back-off way . The formula of back-off valve value and relation betwixt channel estate and the value of
back-off windows are found, then, proving the validity of DEDCA which adapt to VoWLAN technology by simulation.
引文
[1] Jim．Geiger，《无线局域网》[M]，人民邮电出版社，2001
[2] 朱立洁，李从容，陈慧剑．WLAN QoS支持机制-IEEE802.11e．通信技术2003年第1期
[3] IEEE P802.1 le/D7.0, "Medium Access Control (MAC) Quality of Service (QoS) Enhancements", January 2004.
[4] E. Ziouva and T. Antonakopoulos, "CSMA/CA performance under high traffic conditions: Throughput and delay analysis," Comp. Commune., vol. 25, pp. 313-321, 2002.
[5] Yang Xiao, "A Simple and Effective Priority Scheme for IEEE 802.11," IEEE Communications Letters, Vol. 7, No. 2, February 2003.
[6] P. Chatzimisios, V. Vistas and A. C. Boucouvalas, "Throughput and delay analysis of IEEE802.11 protocol," Tech Report, Bournemouth University, UK 2002.
[7] Liqiang Zhao and Changxin Fan, "Enhancement of QoS Differentiations Over IEEE802.11 WLAN," IEEE Communications Liters, Vol. 8, No. 8, August 2004
[8] Sunghyun Choi, Javier del Prude, Sai Shaker N and Stefan Mongol, "IEEE 802.11e Contention-Based Channel Access (EDCF) Performance Evaluation," in Proc. IEEE ICC'03,
[9] Technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific Requirements Part 11: Wireless LAN Medium Access Contro] (MAC) and Physical Layer (PHY) specifications, 1999: 155-168.
[10] Xin Wee, "Analysis of QoS NAN for IEEE802. 1le," Master thesis, Link6ping Institute of Technology. Feb, 2004
[11] Antonio Grilo, Mario Maceio, and Mario Nunez, " A Scheduling Algorithm for QoS Supporting IEEE802.11e Networks," iEEEWireless Communications. June 2003
[12] 唐作吟，何建华，杨宗凯．802.11无线局域网的媒体接入机制性能分析．华中科技大学学报(自然科学版)，2003年1月
[13] Andreas Almquist, Anders Lindgren, "Quality of Service Schemes for IEEE 802.11 Simulation Study," MASTER'S THESIS. Proceedings of the 9th international Workshop on Quality of Service, p.281-287, June 06-08, 2001.
[14] S. Mangold, S. Chui, P. May. IEEE 802.11e Wireless LAN for Quality of Service. In Proceedings of the European Wireless, volume l, Florence, Italy, February 2002: 32-39.
[15] IEEE 802.11 WG. Draft Supplement to Standard 802.11-1999: Medium Access Control (MAC) Enhancements for Quality of Service (QoS). IEEE 802.11e/D2.0a, November 2001:75-83.
[16] A. Grills, M. Maceio, M. Nudes. A Service Discipline for Support of IP QoS in IEEE802.11 networks, IFIP Personal Wireless Conference, Finland, August 2001:179-185
[17] N. H. Vaidya, P. Buhl and S. Gupta, "Distributed air scheduling in a wireless LAN," Proc. 6th Annual Int. Conf. On Mobile Computing and Networking, Boston, pp. 167-78, Aug. 2000.
[18] J. L. Sobrinho and A. S. Krishnakumar, "Realtimetraffic over the IEEE 802.11 medium access control layer," Bell Labs Tech. Journal, pp. 172-187, 1996.
[19] D. Gu and J. Zhang, "QoS enhancement in IEEE802.11 wireless local area networks," IEEE Commun. Mag., vol. 41, no. 6, June 2003, pp. 120-124.181GBianchi, "Performance analysis of the IEEE 802.11 distributed coordination function' -IEEE J. Select. Areas Commune, vol. 18, pp. 318-320, Mar. 2000.
[20] E. Ziouva and T. Antonakopoulos, "CSMA/CA performance under high traffic conditions: Throughput and delay analysis," Comp. Commune., vol. 25, pp. 313-321, 2002.
[22] Hua Zhu and smirch Champak, "An Analytical Model for IEEE 802.11e EDCF Differentials Services," in Proc. IEEE ICCCN 2003, Dallas, TX, October, 2003.
[23] 龙华《OPNET Modeler与计算机网络仿真》[M]，西安电子科技大学出版社，2006．
[24] Wen-Kuang Kuo and C.-C. Jay Kuo, "Enhanced Bakeoff Scheme in CSMA/CA for IEEE802.11," IEEE, 2003.
[25] Lassoed Gannon and Stephan Robert, "Dynamic Tuning of the Contention Window Minimum (CWmin) for Enhanced Service Differentiation in IEEE 802]1 Wireless Ad-Hoc," IEEE PIMRC'04, Barcelona, Spain, 5-8, September 2004.
[26] Daqing Go and Anyun Zhang, "QoS Enhancement in IEEE802.11 Wireless Local Area Networks", IEEE Communications Magazine. June 2003-11-9
[27] Y. C. Toy, K. C. Chua, "A capacity analysis for the IEEE 802.11 MAC protocol," Wireless Networks, Vol. 7, No. 2, pp" 159-171, March/April 2001.
[28] Yang Xiao, "Enhanced DCF of IEEE 802.1 le to Support QoS," Proceedings of IEEE Wireless Communications and Networking Conference 2003 (IEEE WCNC 2003), New Orleans Louisianan, USA, March 16-20, 2003.
[29] Antonio Crilo, Marie Nunes, "Performance Evaluation of IEEE 802.11 e," in Prec. TEEE PIMRC'02, Sept. 2002, pp. 511-517. Anchorage, Alaska, USA, May 2003
[30] 倪奕，苏宏，无线局域网上VoIP．通信技术，2003，pp．15-22
[31] 黄永峰，李显，《VoIP的语音质量分析与控制》[J]，控制与决策，2003(7)，第4期，Vol．18
[32] Stefan Mangold, Sunghyun Choi, Peter May, Ole Klein, Guido Hertz, Lothario Stibor, "IEEE 802.11 e Wireless LAN for Quality of Service," in Prec. Our. Wireless'02, vol. 1, Feb. 2002, pp. 32-39
[33] Anders Lindgren, Andreas Anguish, Olav Sheldon, "Quality of Service Schemes for enhance IEEE802.11e Wireless LANs an Evaluation" Mobile Networks and Applications, Vol. 8, No. 3, 2003
[34] Lamia Rodman, Kiang Ni, Thierry Turletti, "AEDCF: Enhanced Service Differentiation for IEEE 802.11 Wireless Ad-Hoc Networks," IEEE WCNC'03, New Orleans, Louisiana, USA, March 16-20, 2003.
[35] Jeffery W. Robinson, and Tdjinder S. Randhawa, "Saturation Throughput Analysis of IEEE 802.11 e Enhanced Distributed Coordination Function," IEEE Journal on Selected Areas in Communications. Vol. 22, No. 5, June 2004.
[36] Patara-Atikom, W. Krishnamurthy, P. Banerjee, S, "Distributed mechanisms for quality of service in wireless LANs, " IEEE Wireless Communications. Vol. 10, No.3. June 2003. pp: 26-34
[37] Kil-Woong Jang, Sung-Ho Hwang and Ki-Jun Han, "A Dynamic Back off Scheme to Guarantee QoS over IEEE 802.11 Wireless Local Area Networks," LNCS 2510, p. 624 f.
[38]Dennis Pong and Tim Moors, "Using Transmission Opportunities and Judicious Parameter Selection in Enhancing Real-time Applications over 802.11 WLAN," 2003
[39] M. Malli, Q. Ni, T. Turletti.and C. IMrakat. Adaptive fairchannel allocation for QoS enhancement in IEEE 802. 1 lwireless LANs r C ]. Paris, IEEE ICC 2004(InternationalConference on Communications), June 20-24, 2004
[40] Y. Kwon, Y. Fang, and H. Latehman. A Novel MAC Protocol with Fast Collision Resolution for Wireless LANs [M]. IEEE Infocom 2003
[41] S.Choi et al. IEEE 802.11e Contention-based Channel Access Performance Evaluation[C]. Anchorage AK, Proc. IEEE ICC, May 2003
[2] 朱立洁，李从容，陈慧剑．WLAN QoS支持机制-IEEE802.11e．通信技术2003年第1期
[3] IEEE P802.1 le/D7.0, "Medium Access Control (MAC) Quality of Service (QoS) Enhancements", January 2004.
[4] E. Ziouva and T. Antonakopoulos, "CSMA/CA performance under high traffic conditions: Throughput and delay analysis," Comp. Commune., vol. 25, pp. 313-321, 2002.
[5] Yang Xiao, "A Simple and Effective Priority Scheme for IEEE 802.11," IEEE Communications Letters, Vol. 7, No. 2, February 2003.
[6] P. Chatzimisios, V. Vistas and A. C. Boucouvalas, "Throughput and delay analysis of IEEE802.11 protocol," Tech Report, Bournemouth University, UK 2002.
[7] Liqiang Zhao and Changxin Fan, "Enhancement of QoS Differentiations Over IEEE802.11 WLAN," IEEE Communications Liters, Vol. 8, No. 8, August 2004
[8] Sunghyun Choi, Javier del Prude, Sai Shaker N and Stefan Mongol, "IEEE 802.11e Contention-Based Channel Access (EDCF) Performance Evaluation," in Proc. IEEE ICC'03,
[9] Technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific Requirements Part 11: Wireless LAN Medium Access Contro] (MAC) and Physical Layer (PHY) specifications, 1999: 155-168.
[10] Xin Wee, "Analysis of QoS NAN for IEEE802. 1le," Master thesis, Link6ping Institute of Technology. Feb, 2004
[11] Antonio Grilo, Mario Maceio, and Mario Nunez, " A Scheduling Algorithm for QoS Supporting IEEE802.11e Networks," iEEEWireless Communications. June 2003
[12] 唐作吟，何建华，杨宗凯．802.11无线局域网的媒体接入机制性能分析．华中科技大学学报(自然科学版)，2003年1月
[13] Andreas Almquist, Anders Lindgren, "Quality of Service Schemes for IEEE 802.11 Simulation Study," MASTER'S THESIS. Proceedings of the 9th international Workshop on Quality of Service, p.281-287, June 06-08, 2001.
[14] S. Mangold, S. Chui, P. May. IEEE 802.11e Wireless LAN for Quality of Service. In Proceedings of the European Wireless, volume l, Florence, Italy, February 2002: 32-39.
[15] IEEE 802.11 WG. Draft Supplement to Standard 802.11-1999: Medium Access Control (MAC) Enhancements for Quality of Service (QoS). IEEE 802.11e/D2.0a, November 2001:75-83.
[16] A. Grills, M. Maceio, M. Nudes. A Service Discipline for Support of IP QoS in IEEE802.11 networks, IFIP Personal Wireless Conference, Finland, August 2001:179-185
[17] N. H. Vaidya, P. Buhl and S. Gupta, "Distributed air scheduling in a wireless LAN," Proc. 6th Annual Int. Conf. On Mobile Computing and Networking, Boston, pp. 167-78, Aug. 2000.
[18] J. L. Sobrinho and A. S. Krishnakumar, "Realtimetraffic over the IEEE 802.11 medium access control layer," Bell Labs Tech. Journal, pp. 172-187, 1996.
[19] D. Gu and J. Zhang, "QoS enhancement in IEEE802.11 wireless local area networks," IEEE Commun. Mag., vol. 41, no. 6, June 2003, pp. 120-124.181GBianchi, "Performance analysis of the IEEE 802.11 distributed coordination function' -IEEE J. Select. Areas Commune, vol. 18, pp. 318-320, Mar. 2000.
[20] E. Ziouva and T. Antonakopoulos, "CSMA/CA performance under high traffic conditions: Throughput and delay analysis," Comp. Commune., vol. 25, pp. 313-321, 2002.
[22] Hua Zhu and smirch Champak, "An Analytical Model for IEEE 802.11e EDCF Differentials Services," in Proc. IEEE ICCCN 2003, Dallas, TX, October, 2003.
[23] 龙华《OPNET Modeler与计算机网络仿真》[M]，西安电子科技大学出版社，2006．
[24] Wen-Kuang Kuo and C.-C. Jay Kuo, "Enhanced Bakeoff Scheme in CSMA/CA for IEEE802.11," IEEE, 2003.
[25] Lassoed Gannon and Stephan Robert, "Dynamic Tuning of the Contention Window Minimum (CWmin) for Enhanced Service Differentiation in IEEE 802]1 Wireless Ad-Hoc," IEEE PIMRC'04, Barcelona, Spain, 5-8, September 2004.
[26] Daqing Go and Anyun Zhang, "QoS Enhancement in IEEE802.11 Wireless Local Area Networks", IEEE Communications Magazine. June 2003-11-9
[27] Y. C. Toy, K. C. Chua, "A capacity analysis for the IEEE 802.11 MAC protocol," Wireless Networks, Vol. 7, No. 2, pp" 159-171, March/April 2001.
[28] Yang Xiao, "Enhanced DCF of IEEE 802.1 le to Support QoS," Proceedings of IEEE Wireless Communications and Networking Conference 2003 (IEEE WCNC 2003), New Orleans Louisianan, USA, March 16-20, 2003.
[29] Antonio Crilo, Marie Nunes, "Performance Evaluation of IEEE 802.11 e," in Prec. TEEE PIMRC'02, Sept. 2002, pp. 511-517. Anchorage, Alaska, USA, May 2003
[30] 倪奕，苏宏，无线局域网上VoIP．通信技术，2003，pp．15-22
[31] 黄永峰，李显，《VoIP的语音质量分析与控制》[J]，控制与决策，2003(7)，第4期，Vol．18
[32] Stefan Mangold, Sunghyun Choi, Peter May, Ole Klein, Guido Hertz, Lothario Stibor, "IEEE 802.11 e Wireless LAN for Quality of Service," in Prec. Our. Wireless'02, vol. 1, Feb. 2002, pp. 32-39
[33] Anders Lindgren, Andreas Anguish, Olav Sheldon, "Quality of Service Schemes for enhance IEEE802.11e Wireless LANs an Evaluation" Mobile Networks and Applications, Vol. 8, No. 3, 2003
[34] Lamia Rodman, Kiang Ni, Thierry Turletti, "AEDCF: Enhanced Service Differentiation for IEEE 802.11 Wireless Ad-Hoc Networks," IEEE WCNC'03, New Orleans, Louisiana, USA, March 16-20, 2003.
[35] Jeffery W. Robinson, and Tdjinder S. Randhawa, "Saturation Throughput Analysis of IEEE 802.11 e Enhanced Distributed Coordination Function," IEEE Journal on Selected Areas in Communications. Vol. 22, No. 5, June 2004.
[36] Patara-Atikom, W. Krishnamurthy, P. Banerjee, S, "Distributed mechanisms for quality of service in wireless LANs, " IEEE Wireless Communications. Vol. 10, No.3. June 2003. pp: 26-34
[37] Kil-Woong Jang, Sung-Ho Hwang and Ki-Jun Han, "A Dynamic Back off Scheme to Guarantee QoS over IEEE 802.11 Wireless Local Area Networks," LNCS 2510, p. 624 f.
[38]Dennis Pong and Tim Moors, "Using Transmission Opportunities and Judicious Parameter Selection in Enhancing Real-time Applications over 802.11 WLAN," 2003
[39] M. Malli, Q. Ni, T. Turletti.and C. IMrakat. Adaptive fairchannel allocation for QoS enhancement in IEEE 802. 1 lwireless LANs r C ]. Paris, IEEE ICC 2004(InternationalConference on Communications), June 20-24, 2004
[40] Y. Kwon, Y. Fang, and H. Latehman. A Novel MAC Protocol with Fast Collision Resolution for Wireless LANs [M]. IEEE Infocom 2003
[41] S.Choi et al. IEEE 802.11e Contention-based Channel Access Performance Evaluation[C]. Anchorage AK, Proc. IEEE ICC, May 2003