CDMA系统基于多业务的软切换优化技术研究
摘要
移动通信以其特有的灵活和便捷的优点符合了现代社会人们对通信技术的要求,在CDMA移动通信系统中,软切换技术已成为追求最大系统容量和提高通信质量的关键技术。软切换使得移动台进行越区切换时,在中断与旧基站的连接之前,采用先连后断策略,实现移动过程中的无缝通信,它具有降低通话中断率、获得分集增益、增加系统容量等优点。
本文重点研究CDMA系统软切换技术的优化。在以往对软切换技术的研究中,大多数针对参数设置和资源分配问题,而对于软切换的判决准则问题则研究得非常少,而且也只是针对单业务而言。
在传统软切换算法中,当链路质量变差需要切换时,由于相邻小区存在同频的情况,移动台可以通过多条无线链路与网络进行通信,通过比较,选取导频信号最强的一个作为目的小区。而导频信号最强的基站也就是路径损耗最小(即路径增益最大)的基站。传统软切换判决算法只是单纯考虑了路径损耗,没有考虑到现实情况中业务分布不均衡的情况。而在切换请求发生时,基站当前负载对于切换能否成功、系统资源的分配利用以及系统性能都非常重要。
未来无线通信系统要求能为不同的用户提供多种的通信业务,同时不同业务有着不同的服务质量要求。为了更好地利用无线网络特征,在充分利用无线系统有限带宽资源的基础上,尽可能的保证用户数据的传输质量,需要对无线系统各类资源进行合理的管理与分配。因此在选择移动台切换的目的小区时,应该将小区的负载也考虑进去,综合考虑路径损耗和小区负载两个因素。
本文在多业务的基础上,针对传统软切换算法的缺点,提出了基于多业务的软切换优化算法,并且将其应用到分层蜂窝系统。优化算法不是简单的将满足切换条件韵候选基站中导频信号强度最大的基站加入激活集,而是在考虑了业务的传播损耗下,兼顾小区负载平衡,达到各小区之间负载平衡和资源的合理利用的目的。在各小区负载相等的情况下,该准则就退化为传统的软切换算法。仿真结果表明,软切换优化算法显著降低了切换中断率,提高了系统性能,显示出较大的优越性,有一定的理论价值和工程实践意义。最后,对全文进行了总结。
Mobile communications satisfy the demand of human beings in the modern society on communication technology, due to their flexibility and convenience. In CDMA mobile communication systems, soft handoff technology has become the key technology which can pursue the largest system capacity and improve the quality of communications. When the mobile station makes soft handoff, it connects with the new base stations before breaking the connection of the old base station. Soft handoff could achieve seamless mobile communication, reduce call blocking rate, get gain of diversity, increase system capacity, and so on.
This thesis focuses on soft handoff algorithm optimization for CDMA system. In the past, the research on soft handoff algorithm focuses on parameter setting and resource allocation. The research on soft handoff criteria is little, and is only for single traffic.
In the traditional soft handoff algorithm, when the link quality deteriorates and needs to be handed off, the mobile station could communicate with networks with many wireless links and select the strongest signal pilot as a goal. The base station whose pilot signal is the strongest has the smallest path loss. The traditional soft handoff algorithm just considers path loss without considering the balance of realistic traffic. The load balance of the base stations, utilization of system resources and system performance are very important during handoff when the handoff request happens.
Future wireless communication system is required to provide many kinds of communication services for different users. Different services have different requirements of service quality. In order to make better use of wireless networking features, all kinds of resources of wireless systems need to be managed and distributed reasonably. We could guarantee data's transmission quality as far as possible while making full use of the limited bandwidth of wireless systems. So in the choice of the cell target to be handed off, path loss and load should both be considered.
In this thesis, optimized soft handoff algorithm for multi-traffic is proposed and used in hierarchical cellular systems. This algorithm could achieve load balance and reasonable use of resources, rather than adding the base station whose pilot signal is the strongest. When the load of each cell is same, this algorithm is just as the traditional algorithm. The simulation results indicate that the optimized algorithm could reduce the transition interruption and improve system performance significantly. The algorithm has some theoretical value and significance of engineering practice.
Finally, full thesis is summarized.
本文重点研究CDMA系统软切换技术的优化。在以往对软切换技术的研究中,大多数针对参数设置和资源分配问题,而对于软切换的判决准则问题则研究得非常少,而且也只是针对单业务而言。
在传统软切换算法中,当链路质量变差需要切换时,由于相邻小区存在同频的情况,移动台可以通过多条无线链路与网络进行通信,通过比较,选取导频信号最强的一个作为目的小区。而导频信号最强的基站也就是路径损耗最小(即路径增益最大)的基站。传统软切换判决算法只是单纯考虑了路径损耗,没有考虑到现实情况中业务分布不均衡的情况。而在切换请求发生时,基站当前负载对于切换能否成功、系统资源的分配利用以及系统性能都非常重要。
未来无线通信系统要求能为不同的用户提供多种的通信业务,同时不同业务有着不同的服务质量要求。为了更好地利用无线网络特征,在充分利用无线系统有限带宽资源的基础上,尽可能的保证用户数据的传输质量,需要对无线系统各类资源进行合理的管理与分配。因此在选择移动台切换的目的小区时,应该将小区的负载也考虑进去,综合考虑路径损耗和小区负载两个因素。
本文在多业务的基础上,针对传统软切换算法的缺点,提出了基于多业务的软切换优化算法,并且将其应用到分层蜂窝系统。优化算法不是简单的将满足切换条件韵候选基站中导频信号强度最大的基站加入激活集,而是在考虑了业务的传播损耗下,兼顾小区负载平衡,达到各小区之间负载平衡和资源的合理利用的目的。在各小区负载相等的情况下,该准则就退化为传统的软切换算法。仿真结果表明,软切换优化算法显著降低了切换中断率,提高了系统性能,显示出较大的优越性,有一定的理论价值和工程实践意义。最后,对全文进行了总结。
Mobile communications satisfy the demand of human beings in the modern society on communication technology, due to their flexibility and convenience. In CDMA mobile communication systems, soft handoff technology has become the key technology which can pursue the largest system capacity and improve the quality of communications. When the mobile station makes soft handoff, it connects with the new base stations before breaking the connection of the old base station. Soft handoff could achieve seamless mobile communication, reduce call blocking rate, get gain of diversity, increase system capacity, and so on.
This thesis focuses on soft handoff algorithm optimization for CDMA system. In the past, the research on soft handoff algorithm focuses on parameter setting and resource allocation. The research on soft handoff criteria is little, and is only for single traffic.
In the traditional soft handoff algorithm, when the link quality deteriorates and needs to be handed off, the mobile station could communicate with networks with many wireless links and select the strongest signal pilot as a goal. The base station whose pilot signal is the strongest has the smallest path loss. The traditional soft handoff algorithm just considers path loss without considering the balance of realistic traffic. The load balance of the base stations, utilization of system resources and system performance are very important during handoff when the handoff request happens.
Future wireless communication system is required to provide many kinds of communication services for different users. Different services have different requirements of service quality. In order to make better use of wireless networking features, all kinds of resources of wireless systems need to be managed and distributed reasonably. We could guarantee data's transmission quality as far as possible while making full use of the limited bandwidth of wireless systems. So in the choice of the cell target to be handed off, path loss and load should both be considered.
In this thesis, optimized soft handoff algorithm for multi-traffic is proposed and used in hierarchical cellular systems. This algorithm could achieve load balance and reasonable use of resources, rather than adding the base station whose pilot signal is the strongest. When the load of each cell is same, this algorithm is just as the traditional algorithm. The simulation results indicate that the optimized algorithm could reduce the transition interruption and improve system performance significantly. The algorithm has some theoretical value and significance of engineering practice.
Finally, full thesis is summarized.
引文
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[2]孙立新,尤肖虎,张萍等,第三代移动通信技术,北京:人民邮电出版社,2000
[3]周正,通信工程新技术实用手册—移动通信技术分册,北京:北京邮电大学出版社,2002
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[5]金荣洪,耿军平,范瑜.无线通信中的智能天线.北京:北京邮电大学出版社,2006
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[8]3GPP,.Technical Specification TS 25.214,UTRA(BS)FDD,Physical layer Procedures(FDD),V3.11.0(2002-12),R99
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[13]Chang J.W.,Sung D.K.Adaptive channel reservation scheme for soft handoff in DS-CDMA cellular systems.IEEE Trans.on VT.,2001,50(2):341-353
[14]Kim D.K.,Sung D.K.Characterization of soft handoff in CDMA systems.IEEE Trans.on VT.,1999,48(4):1195-1202
[15]Chi Wan Sung,Wing Sing Wong.Power Control and Rate Management for Wireless Multimedia CDMA Systems,IEEE Transaction on Communications,Vol.49,NO.7,July 2001,pp.1215-1225
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[22]Cooper R.B.Introduction to Queueing Theory,Second Edition,New York:Elsevier North Holland,2001.
[23]Tao Zhang;Chennikara,J.;Agrawal,P.;van den Berg,E.;Kodama,T.;Autonomous Predictive Resource Reservation for Handoff in Multimedia Wireless Networks,Computers and Cornmunications,2001.Proceedings,Sixth IEEE Symposium on 3-5 July 2001Page(s):230-236
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[2]孙立新,尤肖虎,张萍等,第三代移动通信技术,北京:人民邮电出版社,2000
[3]周正,通信工程新技术实用手册—移动通信技术分册,北京:北京邮电大学出版社,2002
[4]曾令青,移动通信中软切换算法的研究,数据通信,2003年第5期
[5]金荣洪,耿军平,范瑜.无线通信中的智能天线.北京:北京邮电大学出版社,2006
[6]刘鸣等.智能天线技术与应用.北京:机械工业出版社,2006
[7]A.J.Vitethi,A.M.Viterbl,K.S.Gilhousen.Soft Handoff Extends CDMA Cell Coverage and Increases Reverse-ink Capacity,IEEE JSAC,1994,12:1281-128
[8]3GPP,.Technical Specification TS 25.214,UTRA(BS)FDD,Physical layer Procedures(FDD),V3.11.0(2002-12),R99
[9]Y.B.Lin and A.C.Pang,Comparing soft and hard handoff,IEEE Trans.Veh.Technol.,vol.49,May 2000,pp:792-798.
[10]A.J.Vitcrbi,A.M.Vitcrbi,K.S.Gilhousen and E.Zehavi,Soft handoff extends CDMA cell coverage and increases reverse link capacity,IEEE J.Select.Areas Commun.,vol.12,pp.1281-1288,Oct.1994.
[11]Pollini G.P..Trends in handover design.Communication Magazine,1996:82-90
[12]Rave W.,Voigt J.,Fcttweis G.Evaluation of Load Control Strategies in an UTRA/FDD Network.IEEE VTC,2001:2710-2714
[13]Chang J.W.,Sung D.K.Adaptive channel reservation scheme for soft handoff in DS-CDMA cellular systems.IEEE Trans.on VT.,2001,50(2):341-353
[14]Kim D.K.,Sung D.K.Characterization of soft handoff in CDMA systems.IEEE Trans.on VT.,1999,48(4):1195-1202
[15]Chi Wan Sung,Wing Sing Wong.Power Control and Rate Management for Wireless Multimedia CDMA Systems,IEEE Transaction on Communications,Vol.49,NO.7,July 2001,pp.1215-1225
[16]V.O.K.Li and X.Qiu,Personal communication system(PCS),Proc.IEEE,vol.83,pp.1210-1243,Sept.1994.
[17]马丹.软切换比例与CE配置关系[J].移动通信,2004(1-2):100-101
[18]Ibrahim S.Nomay and James.G.Dunham.AVL Based Virtual Destination Hand Off Algorithm.IEEE VTC' 99,1999,pp.1599-1603
[19]Ramanathan,P.Sivalingam,K.M.Agrawal,P.Kishore,S.Resource Allocation during Handoff through Dynamic Schemes for Mobile Multimedia Wireless Networks.INFOCOM'99,Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies,Proceedings,IEEE,Volume 3,21-25 March 1999 Page(s):1204-1211 vol.3
[20]Yeong M,Jang and Byung G Kim.Approximation and Bound Approaches for Connection Control in Broadband Satellite Systems.IEEE ICC'99,1999,pp.770
[21]S.Boumerdassi.An efficient reservation-based dynamic channel assignment strategy,In:Proc of the first IEEE International Conference on 3G Mobile Communication Technologies.London,2000,352-355
[22]Cooper R.B.Introduction to Queueing Theory,Second Edition,New York:Elsevier North Holland,2001.
[23]Tao Zhang;Chennikara,J.;Agrawal,P.;van den Berg,E.;Kodama,T.;Autonomous Predictive Resource Reservation for Handoff in Multimedia Wireless Networks,Computers and Cornmunications,2001.Proceedings,Sixth IEEE Symposium on 3-5 July 2001Page(s):230-236
[24]Young Chon Kim,Dong Eun Lee,Bong Ju Lee,et al.Dynamic Channel Reservation Based on Mobility in Wireless ATM Networks,IEEE Communications Magazine,pp.47-51,Nov.1999
[25]Miquel Oliver,Joan Borras.Performance Evaluation of Variable Reservation Policies for Hand-off Prioritization in Mobile Networks,INFOCOM99.Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies,Proceedings,IEEE,Volume:3,21-25 March 1999 Page(s):1187-1194 vol.3
[26]Howard G.Ebersman and Ozan K.Tonguz,Handoff Ordering Using Signal Prediction Priority Queuing in Personal Communication Systems,IEEE Transactions on Vehicular technology,Vol.48,NO.1,January 1999,pp:20-35
[27]Ariton Xhafa,Ozan K.Tongnz.Dynamic Priority Queuing of Handoff Requests in PCS,IEEE Transaction on Vehicular technology,2001,Vol.50,No.3,pp.341-345
[28]Q.A.zeng,K.Mukumoto,and A.Fukuda,Performance Analysis of Mobile Cellular Radio System with Two-level Priority Reservation Handoff Procedure,IEEE Transactions on Communications,vol.E80-B,No4,April 1997
[29]G.Bolsch,S.Greiner,H.d.Meer,and K.S.Trivedi,Queueing Networks and Markov Chains,NewYork:Wiley,1998
[30]C.L.I.GD.pollini,L.Ozarow and R.D.Gitlin,Performance of Multi-code CDMA wireless Personal Communications Networks,in Proe.ICC,1995,pp.907-911
[31]O.A.zeng,K Mukumoto,and A.Fukuda,A Preemptive Priority Handoff Scheme in integrated Voice and Data Cellular Mobile Systems,Proceeding IEEE,VTC'94,vol.3,June 1994
[32]M.GUDMUNDSON,Correlation Model for Shadow Fading in Mobile Radio Systems,Radio Communication Systems,Royal Institute of Technology,Electrum-207,S-164 40 Kista,Swe.den 5~(th)September 1991
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