OFDM系统动态资源分配算法研究
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摘要
随着移动通信系统的发展，人们对移动业务的需求已经从纯语音业务扩展到数据业务，现在又出现了多媒体业务和Internet业务的需求，导致频谱资源日趋紧张。因此，开发频谱利用率更高的移动通信技术，已成为现阶段移动通信领域一个重要课题。
OFDM技术将无线信道划分为若干个相互正交的子信道，把高速的数据流通过串并转换，分配到这些传输速率相对较低的子信道中传输。它具有支持高速数据传输、抗多径干扰以及频谱效率高等优点，可以大幅提高频谱利用率。同时，OFDM系统能够根据各个子信道的衰落和多径时延特性，对系统资源(比特与功率等)进行动态分配，并且各个子载波可以进行自适应调制，具有很强的灵活性，既能进一步提高系统资源的利用效率，又可满足用户不同的容量需求。
OFDM系统的动态资源分配主要根据实时的信道状态信息，对发送功率、子载波和比特数进行自适应调配。本文首先介绍了OFDM的发展及其基本原理；紧接着介绍了动态资源分配的思想，研究了单用户OFDM系统几种功率比特分配算法，并设计了一种简化的功率比特分配算法；然后，对多用户系统的资源分配算法进行了深入的研究，主要分析和研究了几种次优算法，提出了具有比例公平的分配算法。最后，针对B3G TDD系统中结合OFDM技术的动态资源分配算法做了试探性研究。本文的主要成果有：1．针对现有算法复杂度高的缺点，设计了一种简化的单用户功率比特分配算法，对其用Matlab进行了仿真，作了性能分析；2．针对现有的多用户分配算法在分配子载波时没有考虑用户优先权的问题，提出了具有比例公平的分配算法，仿真分析结果表明，算法在性能上接近于联合的多用户注水分配算法，而同时复杂度却降低了，可以在实际系统中得到运用。3．针对采用OFDM动态资源分配技术的B3G TDD系统MAC层性能进行了探讨性研究，并用Matlab进行仿真，对结果做了性能分析。
With the development of modem mobile communication, the spectral resource is being scare because of the service's expanding from traditional voice to data, multimedia, and interconnection with Internet. So it has been an urgent task to pursue new wireless technology with higher spectral efficiency.
Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique with high spectral efficiency. It divides wireless channel into N orthogonal subchannels, then converts high speed serial bits stream to parallel and transmit through lower speed subchannels. So it can support high speed data service, and has strong capacity of combating with multipath interference. Simultaneously, OFDM can dynamically allocate system resources (such as bit, power, etc.) according to subchannel's fading and multipath delay characteristics, and every subcarrier can carry on self-adaptation modulation. Thus, it has much strong flexibility, and can not only improve the utilization efficiency of system resources, but also meet user's different capacity demands.
The methods of dynamic resource allocation are researched in this paper. First, the development, advantages and disadvantages, basic principle of OFDM are given. Second, the idea and superiority of dynamic resource allocation is introduced. Then much more researches are made on the power and bit allocation algorithms for single-user OFDM systems and a simplifying algorithm is presented. Finally, the dynamic resource allocation in multi-user OFDM systems is discussed greatly. Several sub-optimal algorithms are researched. Then, an improved allocation algorithm which has proportion-equity is introduced. The main results of this thesis are: 1．A simplifying algorithm is presented for power and bit allocation in single-user OFDM systems. Simulations and the problem analysis are done. 2．An improved allocation algorithm possessing proportion-equity is introduced because of the disadvantage of existing algorithm. Simulation has done to prove that our algorithm has the performance close to the multi-user waterfilling algorithm which is a joint allocation algorithm and has the lower computational complexity than it. Our algorithm also can be used in actual systems.
OFDM技术将无线信道划分为若干个相互正交的子信道，把高速的数据流通过串并转换，分配到这些传输速率相对较低的子信道中传输。它具有支持高速数据传输、抗多径干扰以及频谱效率高等优点，可以大幅提高频谱利用率。同时，OFDM系统能够根据各个子信道的衰落和多径时延特性，对系统资源(比特与功率等)进行动态分配，并且各个子载波可以进行自适应调制，具有很强的灵活性，既能进一步提高系统资源的利用效率，又可满足用户不同的容量需求。
OFDM系统的动态资源分配主要根据实时的信道状态信息，对发送功率、子载波和比特数进行自适应调配。本文首先介绍了OFDM的发展及其基本原理；紧接着介绍了动态资源分配的思想，研究了单用户OFDM系统几种功率比特分配算法，并设计了一种简化的功率比特分配算法；然后，对多用户系统的资源分配算法进行了深入的研究，主要分析和研究了几种次优算法，提出了具有比例公平的分配算法。最后，针对B3G TDD系统中结合OFDM技术的动态资源分配算法做了试探性研究。本文的主要成果有：1．针对现有算法复杂度高的缺点，设计了一种简化的单用户功率比特分配算法，对其用Matlab进行了仿真，作了性能分析；2．针对现有的多用户分配算法在分配子载波时没有考虑用户优先权的问题，提出了具有比例公平的分配算法，仿真分析结果表明，算法在性能上接近于联合的多用户注水分配算法，而同时复杂度却降低了，可以在实际系统中得到运用。3．针对采用OFDM动态资源分配技术的B3G TDD系统MAC层性能进行了探讨性研究，并用Matlab进行仿真，对结果做了性能分析。
With the development of modem mobile communication, the spectral resource is being scare because of the service's expanding from traditional voice to data, multimedia, and interconnection with Internet. So it has been an urgent task to pursue new wireless technology with higher spectral efficiency.
Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique with high spectral efficiency. It divides wireless channel into N orthogonal subchannels, then converts high speed serial bits stream to parallel and transmit through lower speed subchannels. So it can support high speed data service, and has strong capacity of combating with multipath interference. Simultaneously, OFDM can dynamically allocate system resources (such as bit, power, etc.) according to subchannel's fading and multipath delay characteristics, and every subcarrier can carry on self-adaptation modulation. Thus, it has much strong flexibility, and can not only improve the utilization efficiency of system resources, but also meet user's different capacity demands.
The methods of dynamic resource allocation are researched in this paper. First, the development, advantages and disadvantages, basic principle of OFDM are given. Second, the idea and superiority of dynamic resource allocation is introduced. Then much more researches are made on the power and bit allocation algorithms for single-user OFDM systems and a simplifying algorithm is presented. Finally, the dynamic resource allocation in multi-user OFDM systems is discussed greatly. Several sub-optimal algorithms are researched. Then, an improved allocation algorithm which has proportion-equity is introduced. The main results of this thesis are: 1．A simplifying algorithm is presented for power and bit allocation in single-user OFDM systems. Simulations and the problem analysis are done. 2．An improved allocation algorithm possessing proportion-equity is introduced because of the disadvantage of existing algorithm. Simulation has done to prove that our algorithm has the performance close to the multi-user waterfilling algorithm which is a joint allocation algorithm and has the lower computational complexity than it. Our algorithm also can be used in actual systems.
引文
[1] John G Proakis，“Digital Communications",Third Edition，电子工业出版社，北京，1998．
[2] 佟学检，罗涛，《OFDM 移动通信技术原理与应用》，人民邮电出版社，2003年6月
[3] 尹长川，罗涛，乐光新，《多载波宽带无线通信技术》，北京邮电大学出版社，2004年
[4] 王育民，梁传甲，《信息与编码理论》，西安电子科技大学出版社，1986．
[5] 郭梯云，杨家玮，李建东，《数字移动通信》(修订本)，人民邮电出版社，2001．
[6] 魏克军，益晓新，《一种基于 OFDM 系统的自适应加载算法》，数字电视与数字视频，2002年第12期，总第246期
[7] 刘培，葛建华，刘刚，《多用户自适应调制 OFDM 系统的高效子载波分配方案》，电子与信息学报，2004年6月第26卷第6期
[8] 余官定，张朝阳，仇佩亮，《一种自适应正交频分复用系统的子载波分配算法》，浙江大学学报(工学版)，第38卷第9期，2004年9月
[9] 余官定，张朝阳，仇佩亮《信道粒度可变的分块自适应 OFDM 传输系统》，电路与系统学报，第9卷第五期，2004年10月
[10] R.G Gallager, "Information theory and reliable communications", John Wiley and Sons Inc.NewYork, 1968.
[11] S B Weinstein, PM.Ebert. "Data Transmission by Frequency-Division Multiplexing Using the Discrete Fourier Transform", IEEE trans. Commun. Technol.5( COM-19): 628～634.
[12] Louise Min Chuin Hoo, "Multiuser transmit optimization for multicarrier modulation systems", California in United States: Stanford University, 2000.
[13] I. Kalet, "The multitone channel", IEEE Trans, On Communication, vol. 37, pp.119～124, Feb., 1989.
[14] Gunnar Wetzker, "Multicarrier Modulation Schemes for Frequency Selective Fading Channels", 0-7803-5106-1/98 1998 IEEE.
[15] J. A.C. Bingham, "Mulicarrier modulation for data transmission: an idea whose time has come", IEEE Communication Magazine, 1990,3(28): 17～25.
[16] C.YWong, R.S.Cheng, K.B.Letaief, and R.D.Murch. "Mulituser OFDM with adaptive subcarrier, bit, and power allocation", IEEE Selected Areas in Communications. Nov.Oct.1999.17 (10): 1747-1758.
[17] Richard Van Nee, Ramjee Prasad, "OFDM wireless Multimedia Communicaitons", Artech House, Boston, London, 2000.
[18] A .Leke and J.M.Ciofi, "A maximum rate loading algorithm for discrete multitone modulation systems", Global Telecommu Conference, 1997. GLOBECOM '97, IEEE Vol.3, Nov.1997 Page(s):1514-1518
[19] Ciofi,J.M. , "Lecture Notes for Advanced Digital Communications", Stanford, Fall 1997.
[20] Wonjong Rhee and J.M.Ciofif, "Increase in capacity of multiuser OFDM system using dynamic subchannel allocation", in proc.IEEE Vehicular Technology Conference Proceedings, VTC 2000, page(s): 1085-1089
[21] Bo Engstrom and Christer Ostberg, "A system for Test of Multiaccess Methods based on OFDM", Methods based on OFDM", 0-7803-1927-3/94 1994 IEEE.
[22] Slawomir Pietrzyk,"Multiuser Subcarrier Allocation for QOS Provision in the OFDM systems[DB/OL]", http://www.google.com/www.ubicom.t udeltf.nl/docs/PID 11821.pdf
[23] Jorge Campello, John M. Ciof, "Optimal discrete bit loading for multicarrier modulation systems", Information Theory, 1998. Proceedings. 1998 IEEE International Symposium on Publication Date: 16-21 Aug 1998.
[24] A.Czylwik, "Adaptive OFDM for Wideband Radio Channels", Globe Com'96,pp713～718.
[25] B.S.Krongold, K. Ramchandran, and D.L.Jones, "Computationally Eficient Optimal Power Allocation Algorithm for Multicarrier Communication Systems", IEEE Trans on Communications, 2000, 48 (1): 23-27.
[26] G. Munz, S. Piletschinger, J. Speidel, "An efficient waterfilling algorithm for multiple access OFDM", IEEE Global Telecommunications Conf. Volume 1,17-21 Nov.2002:681-685.
[27] D. Hughes-Hartogs, "Ensemble modem structure for imperfect transmission media", US Patents No.4,679,227(July 1987), 4,731,816(March 1988) and 4,833,706(May 1989).
[28] Didem Kivanc and Hui Liu, "Subcarrier allocation and power control for OFDMA", Conference Record of the Thirty-Fourth Asilomar Conference on Volume 1, 29 Oct-1 Nov.2000:147-151
[29] P.S.Chow, J.M.Ciofi, and J.A.C.Bingham, "A practical discrete multitone transceiver loading algorithm for data transmission over spectrally shaped channels", Communications, IEEE Transactions on, 1995: 3(2):773～775.
[30] Robert FH. Fisher and Johannes B.Huber, "A New Loading Algorithm for Discrete Multitone Transmission", Proceedings of Globecom, 1996, 1: 724-728.
[31] L J Cimini, Jr, "Analysis and Simulation of a Digital Mobile Channel Using OFDM ", IEEE trans. Commun, 5(COM-19):628～634.
[32] C.Y.Wong, C.Y.Tsui, R.S.Cheng, and K.B.Letaief, "A real-time sub-carrier allocation scheme for multiple access downlink OFDM transmission," IEEE VCT'99.
[33] I.Kim, Hae Leem Lee.B.Kim, and Yong H.Lee, "On the use of linear progr amming for dynamic subchannel and bit allocation in multiuser OFDM," Global Telecommu.Conference, 2001.GLGOBECOM'01.IEEE vol.6, 25-29 Nov.2001page(s):3648～3652
[34] S.Pflet, Gerhard M. and J.Speidel, "Efficient subcarrier allocation for multiple access in OFDM systems", 7~(th) international OFDM-workshop 2002, Hamburg
[35] Guodong Zhang,"Subcarrier and bit allocation for real-time services in multiuser OFDM systems", IEEE International Conference, Nov-June 2004, Vol. 5:2985-2989
[36] W.Mohr, W.Konhuser, "Access Network Evolution Beyond Third Generation Mobile Communications", IEEE Commun. Mag. vol.38. no. 12, Dec.2000, pp. 122-133
[37] Lev Goldfeld, Vladimir Lyandres, and Dov Wulich, "Minimum Ber Power Loading for OFDM in Fading Channel", IEEE Transactions on communications, Vol.50, No.11, November, 2002:pp1729～1734
[38] Beeta Tarokh and Hamid R.Sadijadpour, "Construction of OFDM-QAM Sequences With Low Peak-to-Average Power Ratio", IEEE Transactions on communications, Vol.50, No.1, January, 2003:pp25～28
[39] S .Ohmori, Y.Yamao, and N.Nakajima, "The Future Generations of Mobile Communications Based on Broadband Access Technologies", IEEE Commun. Mag., vol. 38. no.12, Dec.2000, pp.134-142
[40] J.Chuang and N.Sollenberger, "Beyond3G: Wideband wireless data access based on OFDM and dynamic packet assignment", IEEE Common. Mag, vol. 38, no.7, July 2000, pp.78～87
[41] J.Chuang, Jr L.J.Cimini, G.Y.Li, B.McNair, N.Sollenberger, H.Zhao, L.Lin, and M.Suzuki, "High speed wireless data access based on combing EDGE with wideband OFDM", IEEE Common. Mag, vol.37, no.11, Nov.1999, pp.92 -98
[42] Teng Y, Nagaosa T, Mori K, et al, "Proposal of adaptive subchannel and bit allocation method for OFDM access wireless LAN systems[A]. Proceeding IEEE, VTC'03, Volume2[C].Jeju:IEEE, 2003:910-914
[43] Teng Y, Nagaosa T, Mori K, "Proposal of grouping adaptive modulation method for burst mode OFDM transmission system [J]. IEEE Transactions on Communications, 2003, E86-B(1):257～265
[2] 佟学检，罗涛，《OFDM 移动通信技术原理与应用》，人民邮电出版社，2003年6月
[3] 尹长川，罗涛，乐光新，《多载波宽带无线通信技术》，北京邮电大学出版社，2004年
[4] 王育民，梁传甲，《信息与编码理论》，西安电子科技大学出版社，1986．
[5] 郭梯云，杨家玮，李建东，《数字移动通信》(修订本)，人民邮电出版社，2001．
[6] 魏克军，益晓新，《一种基于 OFDM 系统的自适应加载算法》，数字电视与数字视频，2002年第12期，总第246期
[7] 刘培，葛建华，刘刚，《多用户自适应调制 OFDM 系统的高效子载波分配方案》，电子与信息学报，2004年6月第26卷第6期
[8] 余官定，张朝阳，仇佩亮，《一种自适应正交频分复用系统的子载波分配算法》，浙江大学学报(工学版)，第38卷第9期，2004年9月
[9] 余官定，张朝阳，仇佩亮《信道粒度可变的分块自适应 OFDM 传输系统》，电路与系统学报，第9卷第五期，2004年10月
[10] R.G Gallager, "Information theory and reliable communications", John Wiley and Sons Inc.NewYork, 1968.
[11] S B Weinstein, PM.Ebert. "Data Transmission by Frequency-Division Multiplexing Using the Discrete Fourier Transform", IEEE trans. Commun. Technol.5( COM-19): 628～634.
[12] Louise Min Chuin Hoo, "Multiuser transmit optimization for multicarrier modulation systems", California in United States: Stanford University, 2000.
[13] I. Kalet, "The multitone channel", IEEE Trans, On Communication, vol. 37, pp.119～124, Feb., 1989.
[14] Gunnar Wetzker, "Multicarrier Modulation Schemes for Frequency Selective Fading Channels", 0-7803-5106-1/98 1998 IEEE.
[15] J. A.C. Bingham, "Mulicarrier modulation for data transmission: an idea whose time has come", IEEE Communication Magazine, 1990,3(28): 17～25.
[16] C.YWong, R.S.Cheng, K.B.Letaief, and R.D.Murch. "Mulituser OFDM with adaptive subcarrier, bit, and power allocation", IEEE Selected Areas in Communications. Nov.Oct.1999.17 (10): 1747-1758.
[17] Richard Van Nee, Ramjee Prasad, "OFDM wireless Multimedia Communicaitons", Artech House, Boston, London, 2000.
[18] A .Leke and J.M.Ciofi, "A maximum rate loading algorithm for discrete multitone modulation systems", Global Telecommu Conference, 1997. GLOBECOM '97, IEEE Vol.3, Nov.1997 Page(s):1514-1518
[19] Ciofi,J.M. , "Lecture Notes for Advanced Digital Communications", Stanford, Fall 1997.
[20] Wonjong Rhee and J.M.Ciofif, "Increase in capacity of multiuser OFDM system using dynamic subchannel allocation", in proc.IEEE Vehicular Technology Conference Proceedings, VTC 2000, page(s): 1085-1089
[21] Bo Engstrom and Christer Ostberg, "A system for Test of Multiaccess Methods based on OFDM", Methods based on OFDM", 0-7803-1927-3/94 1994 IEEE.
[22] Slawomir Pietrzyk,"Multiuser Subcarrier Allocation for QOS Provision in the OFDM systems[DB/OL]", http://www.google.com/www.ubicom.t udeltf.nl/docs/PID 11821.pdf
[23] Jorge Campello, John M. Ciof, "Optimal discrete bit loading for multicarrier modulation systems", Information Theory, 1998. Proceedings. 1998 IEEE International Symposium on Publication Date: 16-21 Aug 1998.
[24] A.Czylwik, "Adaptive OFDM for Wideband Radio Channels", Globe Com'96,pp713～718.
[25] B.S.Krongold, K. Ramchandran, and D.L.Jones, "Computationally Eficient Optimal Power Allocation Algorithm for Multicarrier Communication Systems", IEEE Trans on Communications, 2000, 48 (1): 23-27.
[26] G. Munz, S. Piletschinger, J. Speidel, "An efficient waterfilling algorithm for multiple access OFDM", IEEE Global Telecommunications Conf. Volume 1,17-21 Nov.2002:681-685.
[27] D. Hughes-Hartogs, "Ensemble modem structure for imperfect transmission media", US Patents No.4,679,227(July 1987), 4,731,816(March 1988) and 4,833,706(May 1989).
[28] Didem Kivanc and Hui Liu, "Subcarrier allocation and power control for OFDMA", Conference Record of the Thirty-Fourth Asilomar Conference on Volume 1, 29 Oct-1 Nov.2000:147-151
[29] P.S.Chow, J.M.Ciofi, and J.A.C.Bingham, "A practical discrete multitone transceiver loading algorithm for data transmission over spectrally shaped channels", Communications, IEEE Transactions on, 1995: 3(2):773～775.
[30] Robert FH. Fisher and Johannes B.Huber, "A New Loading Algorithm for Discrete Multitone Transmission", Proceedings of Globecom, 1996, 1: 724-728.
[31] L J Cimini, Jr, "Analysis and Simulation of a Digital Mobile Channel Using OFDM ", IEEE trans. Commun, 5(COM-19):628～634.
[32] C.Y.Wong, C.Y.Tsui, R.S.Cheng, and K.B.Letaief, "A real-time sub-carrier allocation scheme for multiple access downlink OFDM transmission," IEEE VCT'99.
[33] I.Kim, Hae Leem Lee.B.Kim, and Yong H.Lee, "On the use of linear progr amming for dynamic subchannel and bit allocation in multiuser OFDM," Global Telecommu.Conference, 2001.GLGOBECOM'01.IEEE vol.6, 25-29 Nov.2001page(s):3648～3652
[34] S.Pflet, Gerhard M. and J.Speidel, "Efficient subcarrier allocation for multiple access in OFDM systems", 7~(th) international OFDM-workshop 2002, Hamburg
[35] Guodong Zhang,"Subcarrier and bit allocation for real-time services in multiuser OFDM systems", IEEE International Conference, Nov-June 2004, Vol. 5:2985-2989
[36] W.Mohr, W.Konhuser, "Access Network Evolution Beyond Third Generation Mobile Communications", IEEE Commun. Mag. vol.38. no. 12, Dec.2000, pp. 122-133
[37] Lev Goldfeld, Vladimir Lyandres, and Dov Wulich, "Minimum Ber Power Loading for OFDM in Fading Channel", IEEE Transactions on communications, Vol.50, No.11, November, 2002:pp1729～1734
[38] Beeta Tarokh and Hamid R.Sadijadpour, "Construction of OFDM-QAM Sequences With Low Peak-to-Average Power Ratio", IEEE Transactions on communications, Vol.50, No.1, January, 2003:pp25～28
[39] S .Ohmori, Y.Yamao, and N.Nakajima, "The Future Generations of Mobile Communications Based on Broadband Access Technologies", IEEE Commun. Mag., vol. 38. no.12, Dec.2000, pp.134-142
[40] J.Chuang and N.Sollenberger, "Beyond3G: Wideband wireless data access based on OFDM and dynamic packet assignment", IEEE Common. Mag, vol. 38, no.7, July 2000, pp.78～87
[41] J.Chuang, Jr L.J.Cimini, G.Y.Li, B.McNair, N.Sollenberger, H.Zhao, L.Lin, and M.Suzuki, "High speed wireless data access based on combing EDGE with wideband OFDM", IEEE Common. Mag, vol.37, no.11, Nov.1999, pp.92 -98
[42] Teng Y, Nagaosa T, Mori K, et al, "Proposal of adaptive subchannel and bit allocation method for OFDM access wireless LAN systems[A]. Proceeding IEEE, VTC'03, Volume2[C].Jeju:IEEE, 2003:910-914
[43] Teng Y, Nagaosa T, Mori K, "Proposal of grouping adaptive modulation method for burst mode OFDM transmission system [J]. IEEE Transactions on Communications, 2003, E86-B(1):257～265