OFDMA系统新型切换算法的研究
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摘要
随着移动通信技术的发展，人们对于宽带业务的需求日益增多，未来的移动通信系统(Beyond 3G、4G)必须能够提供更高的传输能力。在多种多址技术方案中，OFDMA具有最强的竞争力。OFDMA系统通过把高速串行的数据流变换到一组低速并行的子信道上发送，可以很好的解决宽带无线情况下出现的频率选择性衰落现象。能有效地对抗宽带无线接入系统中存在的符号间干扰，有效地利用信道的衰落特性和频率分集增益，提高系统容量。
本文首先介绍了OFDMA系统的原理、子载波分配及其无线资源管理技术；然后深入研究了基于OFDMA系统的切换技术，并分析总结了目前OFDMA系统中切换算法的不足之处：OFDMA系统硬切换、软切换都存在着子载波切换不及时或者滞后的问题，OFDMA软切换还存在同址干扰(CCI)过大的问题。同时也存在着切换用户信道质量不是最佳的问题。
在OFDMA系统的基础上，本文针对目前OFDMA切换算法的不足提出了新型的OFDMA切换算法：Level-up和子载波借用切换算法。Level-up算法旨在保证切换用户获得较好的信道质量，配合自适应调制技术从而获得系统吞吐量的提升。子载波借用算法除了具有上述优点，还可以充分利用OFDMA系统的信道资源，提高信道利用率，资源利用更加灵活。
本人设计实现了OFDMA系统的仿真平台，并在此系统级仿真平台的基础上，通过仿真分析对本文提出的Level-up切换算法和对比算法的性能进行了评估和比较。仿真结果表明，新型的切换算法能够保证移动用户的信道质量，并带来系统吞吐量的提高，优化了OFDMA系统性能。
With the development of mobile communications, people request more and more broad-band traffic. Mobile communication systems in future(such as Beyond 3G and 4G)must support higher transmitting ability. Among many division access technologies, OFDMA(Orthogonal Frequency Division Multiplex access) is best. OFDMA system transforms high-speed serial data streams to low-speed parallel data sub-channels and transmits them. It can well solve frequency-selective fading and effectively deal with ISI(inter symbol interference) in broad-band wireless condition, it can utilize channel fading characteristics and frequency diversity gain, and improve system's capability.
At first this text introduces OFDMA system theory sub-carrier allocation scheme and radio resource management(RRM) technologies; and then researches OFDMA system's handover technology deeply, analyses and concludes the disadvantages of present handover algorithms.
Based on OFDMA system, considering the disadvantages of present handover algorithms, this text puts forward new OFDMA handover algorithms: Level-up handover and sub-carrier borrowing handover. The former can ensure that handover user obtain better channel quality, cooperating with self-adaptive modulation technology, it can enhance OFDMA system's throughput. The latter not only has the advantages above but aslo makes full use of OFDMA channel resource, improves channel uslizing effectivity and flexibility.
After theoretic analysis, the author designs OFDMA system level simulating platform. By simulating, the author compares the Level-up handover algorithm with Proposed handover algorithm. Simulating result proves that new handover algorithm can guarantee the handover users' sub-carrier channel quality, and improve OFDMA system throughput and optimize system performance.
本文首先介绍了OFDMA系统的原理、子载波分配及其无线资源管理技术；然后深入研究了基于OFDMA系统的切换技术，并分析总结了目前OFDMA系统中切换算法的不足之处：OFDMA系统硬切换、软切换都存在着子载波切换不及时或者滞后的问题，OFDMA软切换还存在同址干扰(CCI)过大的问题。同时也存在着切换用户信道质量不是最佳的问题。
在OFDMA系统的基础上，本文针对目前OFDMA切换算法的不足提出了新型的OFDMA切换算法：Level-up和子载波借用切换算法。Level-up算法旨在保证切换用户获得较好的信道质量，配合自适应调制技术从而获得系统吞吐量的提升。子载波借用算法除了具有上述优点，还可以充分利用OFDMA系统的信道资源，提高信道利用率，资源利用更加灵活。
本人设计实现了OFDMA系统的仿真平台，并在此系统级仿真平台的基础上，通过仿真分析对本文提出的Level-up切换算法和对比算法的性能进行了评估和比较。仿真结果表明，新型的切换算法能够保证移动用户的信道质量，并带来系统吞吐量的提高，优化了OFDMA系统性能。
With the development of mobile communications, people request more and more broad-band traffic. Mobile communication systems in future(such as Beyond 3G and 4G)must support higher transmitting ability. Among many division access technologies, OFDMA(Orthogonal Frequency Division Multiplex access) is best. OFDMA system transforms high-speed serial data streams to low-speed parallel data sub-channels and transmits them. It can well solve frequency-selective fading and effectively deal with ISI(inter symbol interference) in broad-band wireless condition, it can utilize channel fading characteristics and frequency diversity gain, and improve system's capability.
At first this text introduces OFDMA system theory sub-carrier allocation scheme and radio resource management(RRM) technologies; and then researches OFDMA system's handover technology deeply, analyses and concludes the disadvantages of present handover algorithms.
Based on OFDMA system, considering the disadvantages of present handover algorithms, this text puts forward new OFDMA handover algorithms: Level-up handover and sub-carrier borrowing handover. The former can ensure that handover user obtain better channel quality, cooperating with self-adaptive modulation technology, it can enhance OFDMA system's throughput. The latter not only has the advantages above but aslo makes full use of OFDMA channel resource, improves channel uslizing effectivity and flexibility.
After theoretic analysis, the author designs OFDMA system level simulating platform. By simulating, the author compares the Level-up handover algorithm with Proposed handover algorithm. Simulating result proves that new handover algorithm can guarantee the handover users' sub-carrier channel quality, and improve OFDMA system throughput and optimize system performance.
引文
[1] Hano Wang, Choong Chae Woo and Daesik Hong, A New Subcarder Oriented Handover Scheme in Downlink OFDMA Cellular Systems, IEEE 2005, Page(s): 1618-1622
[2] 802. 16e-2005
[3] Doo Hwan Lee, Kyandoghere Kyamakya and Jean Paul Umondi, Fast Handover Algorithm for IEEE 802. 16e Broadband Wireless Access System
[4] LIU Guangyi, ZHANG Jianhua, ZHANG Ping, Further Vision on TD-SCDMA Evolution, IEEE2005, Page(s): 143-147
[5] Guangyi Liu, Jianhua Zhang, Ping Zhang, Ying Wang, Xiantao Liu, and Shuang Li, Evolution Map from TD-SCDMA to FUTURE B3G TDD, IEEE 2006, Page(s): 54～61
[6] Erik B. Dahlman、Yu-Chuen Jou, FURTHER EVOLUTION OF 3G RADIO ACCESS, IEEE2006, Page(s): 34～36
[7] Hannes Ekstrom, Anders Furuskar, Jonas Karlsson, Michael Meyer, Stefan Parkvall, Johan Torsner, and Mattias Wahlqvist, Technical Solutions for the 3G Long-Term Evolution, IEEE 2006, Page(s): 38～45
[8] Gholamreza Parsaee, Abdulrahman Yarali, OFDMA for the 4/sup th/generation cellular networks, IEEE 2004, Page(s): 2325～2330
[9] James Gross, Hans-Flodan Geerdes, Holger Karl and dam Wolisz, Performance Analysis of Dynamic OFDMA Systems With Inband Signaling, IEEE 2006, Page(s): 427-436
[10] Bang Chul Jung and Dan Keun Sung, Random FH-OFDMA System Based on Statistical Multiplexing, IEEE 2005
[11] 沈嘉，3GPP LTE核心技术及标准化进展，移动通信，2006．4页45～49
[12] Jianfeng Qiang, Ping Zhang, An Efficient Multiple Access Scheme for Dynami Subband Allocation in OFDMA System, IEEE 2005, Page(s): 1046～1049
[13] Sik Choi, Gyung-Ho Hwang, Taesoo Kwon, Ae-Ri Lim, and Dong-Ho Cho, Fast Handover Scheme for Real-Time Downlink Services in IEEE 802. 16e BWA System, IEEE 2005
[14] Hideo Kohayash、Tadayuki Fukuharal、Hao Yuant and Yoshio Takeuchi, Proposal of Single Carrier OFDM Technique with Adaptive Modulation Method, IEEE 2003, Page(s): 1915～1919
[15] 802. 16-2004
[16] Gabriele Lupo, Roberto Cautelier, Maria-Gabriella Di Benedetto, Francesco Malena, Dynamic Resource Allocation with a Soft Handover Procedure for Application in a Broadband System, IEEE1999, Page(s): 2111～2115
[17] Kin K. Leung, Sayandev Muldaerjee and George E. Rittenhouse, Mobility Support for IEEE 802. 16d Wireless Networks, IEEE 2005, Page(s): 1446～1452
[18] X. Cai, S. Zhou, and G. B. Giannakis, Group-Orthogonal Multicarrier CDMA, IEEE 2004, Page(s): 90-99
[19] Il-Hee Shin, Chae-Woo Lee, A QoS Guaranteed Fast Handoff Algorithm for Wireless LAN, IEEE 2004, Page(s): 3827～3832
[20] Guoqing Li and Hui Liu, On the Optimality of the OFDMA Network, IEEE 2005, Page(s): 438～440
[21] Kanghee Kim, Hongku Kang and Kiseon Kim, Providing Quality of Service in Adaptive Resource Allocation for OFDMA Systems, IEEE 2004, Page(s): 1612～1615
[22] Young-June Choi, Suho Park, and Saewoong Bahk, Multichannel Random Access in OFDMA Wireless Networks, IEEE 2006, Page(s): 603～613
[23] Gautam Kulkarni, Sachin Adlakha and Mani Srivastava, Subcarrier Allocation and Bit Loading Algorithms for OFDMA-Based Wireless Networks, IEEE 2005, Page(s): 652～662
[24] Luke T. H. Lee, Chung-Ju Chang, Yih-Shen Chen, and Scott Shen, A Utility-Approached Radio Resource Allocation Algorithm for Downlink in OFDMA Cellular Systems, IEEE 2005
[25] 3GPP, "Radio Resource Control (RRC)", TS 25. 331, June 2005
[26] 孙立新，尤肖虎，张萍等，第三代移动通信技术，人民邮电出版社，2001
[27] 吴违陵，牛凯，移动通信原理，电子工业出版社，2006
[28] 王文博，郑侃，宽带无线通信OFDM技术，人民邮电出版社，2003
[29] 王莹，张平，无线资源管理，北京邮电大学出版社，2005
[30] 杨大成等，移动传播环境理论基础·分析方法和建模技术，机械工业出版社，2003
[31] 张荣涛，谢显中，OFDM几种多址接入技术的分析，信息技术，2006年 第5期，页59～62
[32] 陈臣，马晓婷，刘乃安，OFDMA无线宽带接入系统简介及性能仿真分析，电力系统通信，第26卷第148期，页42～44
[33] 侯自强，从WiMAX到LTE不同宽带无线接入技术殊途同归，电信科学 2005年第10期，页18～21
[34] 张布战，陈臣，马晓婷，子载波交织分配的OFDMA系统，信息技术，2005年第6期，页21～23
[35] Yinglin Xu, J. Weng, and Tho Le-Ngoc, Adaptive Tone Diversity for OFDMA in Broadband Wireless Communications, IEEE 2004, Page(s): 1594～1597
[36] Y. Peng, A. Doufexi, S. Armour and J. McGeehan, An Investigation of Dynamic Sub-carder Allocation in OFDMA Systems, IEEE 2005
[37] Jung Hyoung Kwon, Duho Rhee, Mu Byun, Younghoon Whang, and Kwang Soon Kim, Adaptive Modulation Technique with Partial CQI for Multiuser OFDMA Systems, ICACT2006, Page(s): 1283～1286s
[38] Xing Zhang, En Zhou, Renshui Zhu, Shiming Liu, Wenbo Wang, Adaptive Multiuser Radio Resource Allocation for OFDMA Systems, IEEE 2005, Page(s): 3846～3850
[39] Eun Kyoung Paik and Yanghee Choi, Prediction-Based Fast Handoff for Mobile WLANS, IEEE 2003, Page(s): 748～753
[40] Alex Hills, Bob Friday, Radio Resource Management in Wireless LANs, IEEE 2004, Page(s): 9～14
[41] Seongkwan Kim and Sunghyun Choi, Se-kyu Park, Jaehwan Lee, Sungmann Kim, An Empirical Measurements-based Analysis of Public WLAN Handoff Operations, IEEE 2006
[42] Per Magnusson, Johan Lundsjo, Joachim Sachs, Pontus Wallentin, Radio Resource Management Distribution in a Beyond 3G Multi-Radio Access Architecture, IEEE2004, Page(s): 3472～3477
[2] 802. 16e-2005
[3] Doo Hwan Lee, Kyandoghere Kyamakya and Jean Paul Umondi, Fast Handover Algorithm for IEEE 802. 16e Broadband Wireless Access System
[4] LIU Guangyi, ZHANG Jianhua, ZHANG Ping, Further Vision on TD-SCDMA Evolution, IEEE2005, Page(s): 143-147
[5] Guangyi Liu, Jianhua Zhang, Ping Zhang, Ying Wang, Xiantao Liu, and Shuang Li, Evolution Map from TD-SCDMA to FUTURE B3G TDD, IEEE 2006, Page(s): 54～61
[6] Erik B. Dahlman、Yu-Chuen Jou, FURTHER EVOLUTION OF 3G RADIO ACCESS, IEEE2006, Page(s): 34～36
[7] Hannes Ekstrom, Anders Furuskar, Jonas Karlsson, Michael Meyer, Stefan Parkvall, Johan Torsner, and Mattias Wahlqvist, Technical Solutions for the 3G Long-Term Evolution, IEEE 2006, Page(s): 38～45
[8] Gholamreza Parsaee, Abdulrahman Yarali, OFDMA for the 4/sup th/generation cellular networks, IEEE 2004, Page(s): 2325～2330
[9] James Gross, Hans-Flodan Geerdes, Holger Karl and dam Wolisz, Performance Analysis of Dynamic OFDMA Systems With Inband Signaling, IEEE 2006, Page(s): 427-436
[10] Bang Chul Jung and Dan Keun Sung, Random FH-OFDMA System Based on Statistical Multiplexing, IEEE 2005
[11] 沈嘉，3GPP LTE核心技术及标准化进展，移动通信，2006．4页45～49
[12] Jianfeng Qiang, Ping Zhang, An Efficient Multiple Access Scheme for Dynami Subband Allocation in OFDMA System, IEEE 2005, Page(s): 1046～1049
[13] Sik Choi, Gyung-Ho Hwang, Taesoo Kwon, Ae-Ri Lim, and Dong-Ho Cho, Fast Handover Scheme for Real-Time Downlink Services in IEEE 802. 16e BWA System, IEEE 2005
[14] Hideo Kohayash、Tadayuki Fukuharal、Hao Yuant and Yoshio Takeuchi, Proposal of Single Carrier OFDM Technique with Adaptive Modulation Method, IEEE 2003, Page(s): 1915～1919
[15] 802. 16-2004
[16] Gabriele Lupo, Roberto Cautelier, Maria-Gabriella Di Benedetto, Francesco Malena, Dynamic Resource Allocation with a Soft Handover Procedure for Application in a Broadband System, IEEE1999, Page(s): 2111～2115
[17] Kin K. Leung, Sayandev Muldaerjee and George E. Rittenhouse, Mobility Support for IEEE 802. 16d Wireless Networks, IEEE 2005, Page(s): 1446～1452
[18] X. Cai, S. Zhou, and G. B. Giannakis, Group-Orthogonal Multicarrier CDMA, IEEE 2004, Page(s): 90-99
[19] Il-Hee Shin, Chae-Woo Lee, A QoS Guaranteed Fast Handoff Algorithm for Wireless LAN, IEEE 2004, Page(s): 3827～3832
[20] Guoqing Li and Hui Liu, On the Optimality of the OFDMA Network, IEEE 2005, Page(s): 438～440
[21] Kanghee Kim, Hongku Kang and Kiseon Kim, Providing Quality of Service in Adaptive Resource Allocation for OFDMA Systems, IEEE 2004, Page(s): 1612～1615
[22] Young-June Choi, Suho Park, and Saewoong Bahk, Multichannel Random Access in OFDMA Wireless Networks, IEEE 2006, Page(s): 603～613
[23] Gautam Kulkarni, Sachin Adlakha and Mani Srivastava, Subcarrier Allocation and Bit Loading Algorithms for OFDMA-Based Wireless Networks, IEEE 2005, Page(s): 652～662
[24] Luke T. H. Lee, Chung-Ju Chang, Yih-Shen Chen, and Scott Shen, A Utility-Approached Radio Resource Allocation Algorithm for Downlink in OFDMA Cellular Systems, IEEE 2005
[25] 3GPP, "Radio Resource Control (RRC)", TS 25. 331, June 2005
[26] 孙立新，尤肖虎，张萍等，第三代移动通信技术，人民邮电出版社，2001
[27] 吴违陵，牛凯，移动通信原理，电子工业出版社，2006
[28] 王文博，郑侃，宽带无线通信OFDM技术，人民邮电出版社，2003
[29] 王莹，张平，无线资源管理，北京邮电大学出版社，2005
[30] 杨大成等，移动传播环境理论基础·分析方法和建模技术，机械工业出版社，2003
[31] 张荣涛，谢显中，OFDM几种多址接入技术的分析，信息技术，2006年 第5期，页59～62
[32] 陈臣，马晓婷，刘乃安，OFDMA无线宽带接入系统简介及性能仿真分析，电力系统通信，第26卷第148期，页42～44
[33] 侯自强，从WiMAX到LTE不同宽带无线接入技术殊途同归，电信科学 2005年第10期，页18～21
[34] 张布战，陈臣，马晓婷，子载波交织分配的OFDMA系统，信息技术，2005年第6期，页21～23
[35] Yinglin Xu, J. Weng, and Tho Le-Ngoc, Adaptive Tone Diversity for OFDMA in Broadband Wireless Communications, IEEE 2004, Page(s): 1594～1597
[36] Y. Peng, A. Doufexi, S. Armour and J. McGeehan, An Investigation of Dynamic Sub-carder Allocation in OFDMA Systems, IEEE 2005
[37] Jung Hyoung Kwon, Duho Rhee, Mu Byun, Younghoon Whang, and Kwang Soon Kim, Adaptive Modulation Technique with Partial CQI for Multiuser OFDMA Systems, ICACT2006, Page(s): 1283～1286s
[38] Xing Zhang, En Zhou, Renshui Zhu, Shiming Liu, Wenbo Wang, Adaptive Multiuser Radio Resource Allocation for OFDMA Systems, IEEE 2005, Page(s): 3846～3850
[39] Eun Kyoung Paik and Yanghee Choi, Prediction-Based Fast Handoff for Mobile WLANS, IEEE 2003, Page(s): 748～753
[40] Alex Hills, Bob Friday, Radio Resource Management in Wireless LANs, IEEE 2004, Page(s): 9～14
[41] Seongkwan Kim and Sunghyun Choi, Se-kyu Park, Jaehwan Lee, Sungmann Kim, An Empirical Measurements-based Analysis of Public WLAN Handoff Operations, IEEE 2006
[42] Per Magnusson, Johan Lundsjo, Joachim Sachs, Pontus Wallentin, Radio Resource Management Distribution in a Beyond 3G Multi-Radio Access Architecture, IEEE2004, Page(s): 3472～3477