同步单频蜂窝系统——理论分析与系统仿真研究
|
摘要
当前在世界范围内蜂窝移动通信仍在高速发展。移动用户的高速增长，主要是由于用户对移动服务的需求所促成的。除了当前移动通信所能提供的通话服务外，人们还要求更多的多媒体服务，不仅有新的应用，还要能满足无所不在的个性化服务。为了达到此目的，新一代移动通信(B3G／4G)的移动通信系统可以采用演进或革新的方式来实现。演进是指对已有系统(如IMT-2000)等加以改善，而革新则指的是完全新开发的系统。
由于新一代移动通信业务类型及采用的核心技术等方面与以往的移动通信系统有较大不同，因此无论是采用演进或者革新的方式，均需要在其中充分结合新一代移动通信的新特点，如核心技术的物理传输特性、系统上下行业务负荷不对称等。如何做到既能利用这些新特点，又同时能提高通信质量和系统资源利用率(系统容量)，保证一定的服务质量，是本文所做的一种探索。
本文围绕第四代移动通信(4G)及其核心技术OFDM(正交频分复用)的要求和特点，在传统的蜂窝系统结构和无线资源管理方法的基础上，独创地提出一种适用于4G的新型单频蜂窝系统(SFCN，Single Frequency Network Cellular Network)。该系统可以在保障通信质量的前提下同时提高系统的系统频谱效率和系统容量，本文在理论上分析并仿真了该系统的部分性能，并与传统的GSM系统进行了比较。
第一章介绍了移动通信在通信领域的重要位置及其发展过程，以及移动通信中无线资源管理涉及的各项技术在有限带宽条件下为尽可能多的用户提供业务质量保障的重要意义。
第二章介绍了蜂窝通信系统设计中的几个基本要素，并重点介绍了每个要素对系统容量、服务质量等系统性能参数的影响及解决办法。
第三章提出了一种适用于4G的同步单频蜂窝网络结构方案，它较好地利用了OFDM的物理传输特性并在一定程度上缓和了系统容量与用户通信质量之间的矛盾。通过单频网的优势在两者之间取得了折衷。还给出了它和现有蜂窝系统的理论分析比较。
第四章首先介绍了网络的仿真工具OPNET和仿真方法，接着主要描述了SFCN和GSM两个系统仿真的过程和仿真模型，并对一系列仿真性能进行了分析。
The commercial proliferation of cellular voice and limited data service has created a great demand for mobile communications. Current voice, fax, email and paging services will give way to data transfer, video conferencing, image transfer, and video delivery. Achieving such an advanced level of mobile multimedia service requires the development of mobile telecommunication technology. As a result, next-generation(4G) mobile communication systems are currently being researched worldwide. We can get the solution of 4G by evolving existed systems or propose a totally novel system.
In the research of 4G, it's one of the most important and challenging problems that the special characteristic of physical layer and specific demands of users in 4G should be considered first. So it's an important aspect that how to utilize the specific characteristic of technology used in 4G to improve system capacity without depressing the quality of service. In this paper we will do some efforts in this field.
In this thesis, we address this challenge in detail and design solutions to it and evaluate the performance of them by simulation. Based on the traditional structure of cellular network and methods of radio resource allocation, we propose a novel synchronous Single Frequency Cellular Network (SFCN) system, which is more proper for 4G. The ability of OFDM(Orthogonal Frequency Division Multiplexing) to restrain the negative effects of multi-path transmission is used in SFCN, which bring the system the simultaneous improvement of Carrier Interference Ratio and frequency efficiency. Our results comparing with GSM show that the solution improved the performance of system greatly.
Chapter 1 introduces the important role of mobile communication in communication field, and points out the significance for promoting the research work of guaranteeing QoS(Quality of Service) using modern radio resource management techniques with limited bandwidth.
Chapter 2 introduces the theory of cellular system design, including several elements usually used in design. At the same time Chapter 2 gives out the effects that these elements bring to the system performance.
Chapter 3 proposes a novel SFCN system. And we demonstrate its advantage to exist systems through theoretic analysis. Generally frequency efficiency and quality of communication can not be both ensured, which won't happen in SFCN because the full utilization of characteristic of OFDM and the specific structure of SFCN.
Chapter 4 gives a brief introduction of the enviroment, methodology of network simulation-OPNET. Also the model of GSM and SFCN are presented. The respective simulation results of two systems are given.
由于新一代移动通信业务类型及采用的核心技术等方面与以往的移动通信系统有较大不同，因此无论是采用演进或者革新的方式，均需要在其中充分结合新一代移动通信的新特点，如核心技术的物理传输特性、系统上下行业务负荷不对称等。如何做到既能利用这些新特点，又同时能提高通信质量和系统资源利用率(系统容量)，保证一定的服务质量，是本文所做的一种探索。
本文围绕第四代移动通信(4G)及其核心技术OFDM(正交频分复用)的要求和特点，在传统的蜂窝系统结构和无线资源管理方法的基础上，独创地提出一种适用于4G的新型单频蜂窝系统(SFCN，Single Frequency Network Cellular Network)。该系统可以在保障通信质量的前提下同时提高系统的系统频谱效率和系统容量，本文在理论上分析并仿真了该系统的部分性能，并与传统的GSM系统进行了比较。
第一章介绍了移动通信在通信领域的重要位置及其发展过程，以及移动通信中无线资源管理涉及的各项技术在有限带宽条件下为尽可能多的用户提供业务质量保障的重要意义。
第二章介绍了蜂窝通信系统设计中的几个基本要素，并重点介绍了每个要素对系统容量、服务质量等系统性能参数的影响及解决办法。
第三章提出了一种适用于4G的同步单频蜂窝网络结构方案，它较好地利用了OFDM的物理传输特性并在一定程度上缓和了系统容量与用户通信质量之间的矛盾。通过单频网的优势在两者之间取得了折衷。还给出了它和现有蜂窝系统的理论分析比较。
第四章首先介绍了网络的仿真工具OPNET和仿真方法，接着主要描述了SFCN和GSM两个系统仿真的过程和仿真模型，并对一系列仿真性能进行了分析。
The commercial proliferation of cellular voice and limited data service has created a great demand for mobile communications. Current voice, fax, email and paging services will give way to data transfer, video conferencing, image transfer, and video delivery. Achieving such an advanced level of mobile multimedia service requires the development of mobile telecommunication technology. As a result, next-generation(4G) mobile communication systems are currently being researched worldwide. We can get the solution of 4G by evolving existed systems or propose a totally novel system.
In the research of 4G, it's one of the most important and challenging problems that the special characteristic of physical layer and specific demands of users in 4G should be considered first. So it's an important aspect that how to utilize the specific characteristic of technology used in 4G to improve system capacity without depressing the quality of service. In this paper we will do some efforts in this field.
In this thesis, we address this challenge in detail and design solutions to it and evaluate the performance of them by simulation. Based on the traditional structure of cellular network and methods of radio resource allocation, we propose a novel synchronous Single Frequency Cellular Network (SFCN) system, which is more proper for 4G. The ability of OFDM(Orthogonal Frequency Division Multiplexing) to restrain the negative effects of multi-path transmission is used in SFCN, which bring the system the simultaneous improvement of Carrier Interference Ratio and frequency efficiency. Our results comparing with GSM show that the solution improved the performance of system greatly.
Chapter 1 introduces the important role of mobile communication in communication field, and points out the significance for promoting the research work of guaranteeing QoS(Quality of Service) using modern radio resource management techniques with limited bandwidth.
Chapter 2 introduces the theory of cellular system design, including several elements usually used in design. At the same time Chapter 2 gives out the effects that these elements bring to the system performance.
Chapter 3 proposes a novel SFCN system. And we demonstrate its advantage to exist systems through theoretic analysis. Generally frequency efficiency and quality of communication can not be both ensured, which won't happen in SFCN because the full utilization of characteristic of OFDM and the specific structure of SFCN.
Chapter 4 gives a brief introduction of the enviroment, methodology of network simulation-OPNET. Also the model of GSM and SFCN are presented. The respective simulation results of two systems are given.
引文
[1] Theodore S．Rappaport“无线通信原理与应用”，电子工业出版社，1999．11
[2] 移动通信在线 www．mc21 st．com
[3] Kaveh Pahlavan, Prashant Krishnamurthy“无线网络通信原理与应用”，清华大学出版2002．11
[4] William C．Y．Lee“移动蜂窝通信模拟和数字系统(第二版)”，电子工业出版社，1996．3
[5] Jhong Sam Lee, Leonard E.Miller “CDMA系统工程手册”，人民邮电出版社，2001．2
[6] 杨大成等“CDMA2000 1X移动通信系统”，机械工业出版社，2003．1
[7] 王文博等“时分双工CDMA移动通信技术”，北京邮电大学出版社，2001．3
[8] Lee, W. C. Y.; "Spectrum Efficiency in Cellular", Vehicular Technology, IEEE Transactions on, Volume: 38, Issue: 2, pp. 69-75, May 1989
[9] Samaras, K.; Demetrescu, C.; Luschi, C; Ran Yan; "Capacity Calculation of a Packet Switched Voice Cellular Network", Vehicular Technology Conference Proceedings, 2000. VTC 2000-Spring Tokyo. IEEE 51st, Volume: 1, 15-18, May 2000
[10] Eriksson, M.; "Dynamic Single Frequency Networks", Selected Areas in Communications, IEEE Journal on, Volume: 19, Issue: 10, pp. 1905-1914Oct. 2001
[11] Eriksson, M.; "Evaluation of Packet-by-packet Downlink Radio Resource Management Schemes", VTC IEEE VTS 53rd, vol. 2, pp. 967-971 2001
[12] 樊吕信，詹道庸等．通信原理 (第4版)．国防工业出版社，1996
[13] 曹千芊，张朝阳“蜂窝网中基于切换优先的预测性机制”，移动通信，录用待发表
[14] 佟学偷，罗涛“OFDM移动通信技术原理与应用”，人民邮电出版社，2003．6
[15] Lee, W. C. Y.; "Smaller Cells for Greater Performance", Communications Magazine, IEEE, Volume: 29, Issue: 11, pp: 19-23, Nov. 1991
[16] 网络仿真软件论坛，http://www.netfomm.com.cr/forum topics.asp?FID=4
[17] Daigle, J.; Langford, J.; "Models for Analysis of Packet Voice Communications Systems", Selected Areas in Communications, IEEE Joumal on, Volume: 4, Issue: 6, pp. 847-855 Sep 1986
[18] E. Lawrey, "Multiuser OFDM", Signal Processing and Its Applications, 1999. ISSPA '99. Proceedings of the Fifth International Symposium on, pp. 761-764 vol. 2, 1999
[19] 卢勇，“移动通信产业的现状与未来”，电信网技术，2003．1，pp41-44
[20] 赵新胜，尤新虎，“未来移动通信中的无线资源管理”，宽带世界，2003．1，pp63-65
[21] 彭林，“第三代移动通信技术”，电子工业出版社，2003．2
[22] 高风吉，“适用于地面数字电视广播的单频网”，广播与电视技术，2003．6．pp31-33
[23] 纪红，佟学俭等，“OFDM，适合于未来移动通信系统的解决方案”，无线电工程，2002．7，pp17-20
[24] Bear, D., "Principles of Telecommunication Traffic Engineeriing", revised 3rd ed., London: Peter Peregrinus Ltd. on behalf of the IEE, 1988
[25] Jakes, W. C., ed., "Microwave Mobile Communications", New York, IEEE press, 1994
[26] Beckmann, P., "Elementary Queuing Theory and Telephone Traffic", Geneva, Lee's ABC of the Telephone, 1977
[27] Lee, W. C. Y., "Elements of Cellular Mobile Radio Systems", IEEE Transaction on Vehicular
Technology. Vol. VT-35, No. 2, pp. 48-56, May 1986
[28] 孙立新 刑宁霞，“CDMA移动通信技术”，人民邮电出版社，1996．6
[29] A. Murase, I. C. Symington and E. Green, "Handover Criterion for Macro and Microcellular System", Proc. VTC'91, pp524-530, 1991
[30] Hyoung-Goo Jeon; Soo-Kun Kwon; Seong Rag Kim; Chang-Eon Kang; "A call control scheme for soft handoff in CDMA cellular systems", Communications, ICC 98. Conference Record. 1998 IEEE International Conference on, Vol. 2, pp999-1003, June 1998
[31] Ming-Hsing, Chiu, Bassiouni M. A., "Predictive Schemes for Handoff Prioritization in Cellular Networks Based on Mobile Positioning", Selected Areas in Communications, IEEE Journal on, March 2000
[32] Zhong Xu, Zhengqiang Ye, "A New Adaptive Channel Reservation Scheme for Handoff Calls in Wireless Celluar Networks", Proceedings of IFIP networking, 2002, Italy
[33] 潘武，刘序明，许希斌，姚彦，“正交频分复用技术在宽带通信中的应用”，移动通信，1997．3，pp．32-37
[34] Rebhan, R.; Zander, J.; "On the outage probability in single frequency networks for digital broadcasting", Broadcasting, IEEE Transactions on, Volume: 39, Issue: 4, pp395-401, Dec. 1993
[35] W. ZIRWAS; "Single Frequency Network Concepts for cellular OFDM Radio Systems", Int. OFDM Workshop Hamburg, Sep. 2000
[36] Zhaocheng Wang; Stirling-Gallacher, R. A.; "Frequency reuse scheme for cellular OFDM systems" Electronics Letters, Volume: 38, Issue: 8, 11, pp. 387-388, April 2002
[37] Rha, P. S.; "Frequency reuse scheme with reduced co-channel interference for fixed cellular systems", Electronics Letters, Vol. 34, Issue: 3, 5 pp. 237-238, Feb. 1998
[38] Akyildiz, I. F.; McNair, J.; "Mobility management in next-generation wireless systems", Proceedings of the IEEE, Volume: 87, Issue: 8, pp 1347-1384, Aug. 1999
[39] Krishnan, M.; Ismail, M.; Annuar, K.; "Radio resource and mobility management in GPRS network", Research and Development, Student Conference on, 16-17, pp. 132-135, July 2002
[40] Al-Akaidi, M.; A1Nsour, D.; Hammuda, H.; Urwin, P.; "Capacity Evaluation in Cellular System", 3G Mobile Communication Technologies, Second International Conference on, pp 175-179, March 2001
[41] H. Balakrishnan, "Challenges to Reliable Data Transport over Heterogeneous Wireless Networks", PhD Thesis, UC Berkeley, 1998
[42] 王文博，张金文 "Opnet Modeler 与网络仿真”，人民邮电出版社，2003.10
[43] W. Kellerer, E. Steinbach, P. Eisert, and B. Girod, "A Real-time Internet Streaming Media Testbed," International Conference on Multimedia and Expo, ICME 2002
[44] Giao T. Nguyen, Randy H. Katz, Brian Noble, Mahadev Satyanarayanan, "A trace-based approach for modeling wireless channel behavior", Proceedings of the 28th conference on Winter simulation, p. 597-604, December 08-11, 1996, Coronado, California, United States
[45] Inoue, M.; Nakagawa, M.; "Space Time Transmit Site Diversity for OFDM Multi Base Station System", Mobile and Wireless Communications Network, 4th International Workshop on, 9-11, pp. 30-34, Sept. 2002
[46] Martin-Escalona, I.; Barcelo, E; Casademont, J.; "Teletraffic Simulation of Cellular
Networks: Modeling the Handoff Arrivals and The Handoff Delay", Personal, Indoor and Mobile Radio Communications, vol. 5, pp. 2209-2213, 2002
[47] ETSI, "Radio broadcasting systems: Digital audio broadcasting (DAB) to mobile, portable and fixed receivers", ETS 300 401, May 1997.
[48] S. S. Saunders, "Antennas and Propagation for Wireless Communication Systems", John Wiley & Sons Ltd, New Jersey, 1999.
[49] Khan, F.; Zeghlache, D.; Hebuterne, G., "Distributed-queuing call admission control in wireless packet communications", Universal Personal Communications Record, IEEE 6th International Conference on, vol. 1, pp. 134-140, Oct. 1997
[50] Kokubo, T.; Yamasaki, S.; Nakagawa, M.; "Transmission Delay Control for Single Frequency OFDM Multi-Base-Station in a Cell Using Position Information", Vehicular Technology Conference, IEEE VTS-Fall VTC 2000. 52nd, vol. 2, pp. 524-529, Sept. 2000
[51] N. D. Tripathi, J. H. Reed, and H. F. VanLandingham, "Handoff in Cellular Systems",IEEE Personal Commun, Dec. 1998
[52] Sirin Tekinay and Bijan Jabbari, "Handover and Channel Assignment in Mobile Celluar Networks", IEEE Communications Magazine, Nov. 1991
[2] 移动通信在线 www．mc21 st．com
[3] Kaveh Pahlavan, Prashant Krishnamurthy“无线网络通信原理与应用”，清华大学出版2002．11
[4] William C．Y．Lee“移动蜂窝通信模拟和数字系统(第二版)”，电子工业出版社，1996．3
[5] Jhong Sam Lee, Leonard E.Miller “CDMA系统工程手册”，人民邮电出版社，2001．2
[6] 杨大成等“CDMA2000 1X移动通信系统”，机械工业出版社，2003．1
[7] 王文博等“时分双工CDMA移动通信技术”，北京邮电大学出版社，2001．3
[8] Lee, W. C. Y.; "Spectrum Efficiency in Cellular", Vehicular Technology, IEEE Transactions on, Volume: 38, Issue: 2, pp. 69-75, May 1989
[9] Samaras, K.; Demetrescu, C.; Luschi, C; Ran Yan; "Capacity Calculation of a Packet Switched Voice Cellular Network", Vehicular Technology Conference Proceedings, 2000. VTC 2000-Spring Tokyo. IEEE 51st, Volume: 1, 15-18, May 2000
[10] Eriksson, M.; "Dynamic Single Frequency Networks", Selected Areas in Communications, IEEE Journal on, Volume: 19, Issue: 10, pp. 1905-1914Oct. 2001
[11] Eriksson, M.; "Evaluation of Packet-by-packet Downlink Radio Resource Management Schemes", VTC IEEE VTS 53rd, vol. 2, pp. 967-971 2001
[12] 樊吕信，詹道庸等．通信原理 (第4版)．国防工业出版社，1996
[13] 曹千芊，张朝阳“蜂窝网中基于切换优先的预测性机制”，移动通信，录用待发表
[14] 佟学偷，罗涛“OFDM移动通信技术原理与应用”，人民邮电出版社，2003．6
[15] Lee, W. C. Y.; "Smaller Cells for Greater Performance", Communications Magazine, IEEE, Volume: 29, Issue: 11, pp: 19-23, Nov. 1991
[16] 网络仿真软件论坛，http://www.netfomm.com.cr/forum topics.asp?FID=4
[17] Daigle, J.; Langford, J.; "Models for Analysis of Packet Voice Communications Systems", Selected Areas in Communications, IEEE Joumal on, Volume: 4, Issue: 6, pp. 847-855 Sep 1986
[18] E. Lawrey, "Multiuser OFDM", Signal Processing and Its Applications, 1999. ISSPA '99. Proceedings of the Fifth International Symposium on, pp. 761-764 vol. 2, 1999
[19] 卢勇，“移动通信产业的现状与未来”，电信网技术，2003．1，pp41-44
[20] 赵新胜，尤新虎，“未来移动通信中的无线资源管理”，宽带世界，2003．1，pp63-65
[21] 彭林，“第三代移动通信技术”，电子工业出版社，2003．2
[22] 高风吉，“适用于地面数字电视广播的单频网”，广播与电视技术，2003．6．pp31-33
[23] 纪红，佟学俭等，“OFDM，适合于未来移动通信系统的解决方案”，无线电工程，2002．7，pp17-20
[24] Bear, D., "Principles of Telecommunication Traffic Engineeriing", revised 3rd ed., London: Peter Peregrinus Ltd. on behalf of the IEE, 1988
[25] Jakes, W. C., ed., "Microwave Mobile Communications", New York, IEEE press, 1994
[26] Beckmann, P., "Elementary Queuing Theory and Telephone Traffic", Geneva, Lee's ABC of the Telephone, 1977
[27] Lee, W. C. Y., "Elements of Cellular Mobile Radio Systems", IEEE Transaction on Vehicular
Technology. Vol. VT-35, No. 2, pp. 48-56, May 1986
[28] 孙立新 刑宁霞，“CDMA移动通信技术”，人民邮电出版社，1996．6
[29] A. Murase, I. C. Symington and E. Green, "Handover Criterion for Macro and Microcellular System", Proc. VTC'91, pp524-530, 1991
[30] Hyoung-Goo Jeon; Soo-Kun Kwon; Seong Rag Kim; Chang-Eon Kang; "A call control scheme for soft handoff in CDMA cellular systems", Communications, ICC 98. Conference Record. 1998 IEEE International Conference on, Vol. 2, pp999-1003, June 1998
[31] Ming-Hsing, Chiu, Bassiouni M. A., "Predictive Schemes for Handoff Prioritization in Cellular Networks Based on Mobile Positioning", Selected Areas in Communications, IEEE Journal on, March 2000
[32] Zhong Xu, Zhengqiang Ye, "A New Adaptive Channel Reservation Scheme for Handoff Calls in Wireless Celluar Networks", Proceedings of IFIP networking, 2002, Italy
[33] 潘武，刘序明，许希斌，姚彦，“正交频分复用技术在宽带通信中的应用”，移动通信，1997．3，pp．32-37
[34] Rebhan, R.; Zander, J.; "On the outage probability in single frequency networks for digital broadcasting", Broadcasting, IEEE Transactions on, Volume: 39, Issue: 4, pp395-401, Dec. 1993
[35] W. ZIRWAS; "Single Frequency Network Concepts for cellular OFDM Radio Systems", Int. OFDM Workshop Hamburg, Sep. 2000
[36] Zhaocheng Wang; Stirling-Gallacher, R. A.; "Frequency reuse scheme for cellular OFDM systems" Electronics Letters, Volume: 38, Issue: 8, 11, pp. 387-388, April 2002
[37] Rha, P. S.; "Frequency reuse scheme with reduced co-channel interference for fixed cellular systems", Electronics Letters, Vol. 34, Issue: 3, 5 pp. 237-238, Feb. 1998
[38] Akyildiz, I. F.; McNair, J.; "Mobility management in next-generation wireless systems", Proceedings of the IEEE, Volume: 87, Issue: 8, pp 1347-1384, Aug. 1999
[39] Krishnan, M.; Ismail, M.; Annuar, K.; "Radio resource and mobility management in GPRS network", Research and Development, Student Conference on, 16-17, pp. 132-135, July 2002
[40] Al-Akaidi, M.; A1Nsour, D.; Hammuda, H.; Urwin, P.; "Capacity Evaluation in Cellular System", 3G Mobile Communication Technologies, Second International Conference on, pp 175-179, March 2001
[41] H. Balakrishnan, "Challenges to Reliable Data Transport over Heterogeneous Wireless Networks", PhD Thesis, UC Berkeley, 1998
[42] 王文博，张金文 "Opnet Modeler 与网络仿真”，人民邮电出版社，2003.10
[43] W. Kellerer, E. Steinbach, P. Eisert, and B. Girod, "A Real-time Internet Streaming Media Testbed," International Conference on Multimedia and Expo, ICME 2002
[44] Giao T. Nguyen, Randy H. Katz, Brian Noble, Mahadev Satyanarayanan, "A trace-based approach for modeling wireless channel behavior", Proceedings of the 28th conference on Winter simulation, p. 597-604, December 08-11, 1996, Coronado, California, United States
[45] Inoue, M.; Nakagawa, M.; "Space Time Transmit Site Diversity for OFDM Multi Base Station System", Mobile and Wireless Communications Network, 4th International Workshop on, 9-11, pp. 30-34, Sept. 2002
[46] Martin-Escalona, I.; Barcelo, E; Casademont, J.; "Teletraffic Simulation of Cellular
Networks: Modeling the Handoff Arrivals and The Handoff Delay", Personal, Indoor and Mobile Radio Communications, vol. 5, pp. 2209-2213, 2002
[47] ETSI, "Radio broadcasting systems: Digital audio broadcasting (DAB) to mobile, portable and fixed receivers", ETS 300 401, May 1997.
[48] S. S. Saunders, "Antennas and Propagation for Wireless Communication Systems", John Wiley & Sons Ltd, New Jersey, 1999.
[49] Khan, F.; Zeghlache, D.; Hebuterne, G., "Distributed-queuing call admission control in wireless packet communications", Universal Personal Communications Record, IEEE 6th International Conference on, vol. 1, pp. 134-140, Oct. 1997
[50] Kokubo, T.; Yamasaki, S.; Nakagawa, M.; "Transmission Delay Control for Single Frequency OFDM Multi-Base-Station in a Cell Using Position Information", Vehicular Technology Conference, IEEE VTS-Fall VTC 2000. 52nd, vol. 2, pp. 524-529, Sept. 2000
[51] N. D. Tripathi, J. H. Reed, and H. F. VanLandingham, "Handoff in Cellular Systems",IEEE Personal Commun, Dec. 1998
[52] Sirin Tekinay and Bijan Jabbari, "Handover and Channel Assignment in Mobile Celluar Networks", IEEE Communications Magazine, Nov. 1991