多载波CDMA系统的改进方案与序列应用研究
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摘要
在当今和未来的移动通信系统中，都需要高速的数据传输。而当数据在移动信道中以高速传输时，由于时延扩展现象会引起符号间干扰。多载波扩展频谱码分多址系统(MC／CDMA)是一种消除符号间干扰的有效技术，它是利用正交频分复用(OFDM)与码分多址(CDMA)技术相结合的一种调制方法。在准同步CDMA(QS-CDMA)系统中，LS码通过零相关区(ZCZ)，可以消除码间干扰(ISI)和多址接入干扰(MAI)。广义LS(GLS)码是对LS码的广义描述，它可以降低QS-CDMA系统的小区间干扰(ACI)。
本文首先提出了一种改进的多载波码分多址(MC／CDMA)系统。与传统的MC-CDMA系统相比，其主要区别是该方案同时在时域和频域进行扩频。这种系统能更有效地利用传输带宽，实现频率分集。由于该系统降低了每个子载波上的数据速率，扩频序列更容易同步。最后给出了在瑞利衰落信道下的性能分析。
其次本文用高斯近似的方法得出了应用GLS码的多小区QS-CDMA的系统的误码性能。并且与基于LS码的QS-CDMA系统，进行了仿真分析与比较。分析结果表明，与LS码相比，GLS码显著地改善了系统的性能。
最后本文把GLS码应用在MC-DS-CDMA中，并得出了系统的误码性能。该系统利用GLS所具有的零相关区特性克服了OFDM系统存在频偏时的多用户接入干扰(MAI)。结果表明，该系统比之使用Walsh序列的MC-DS-CDMA系统有更好的误码性能，并且有更高的频谱利用率。
High-rate data transmission becomes indispensable for nowadays and future mobile communication system. However, when the data is being transferred in mobile channel, there will be inter-symbol interference (ISI) because of delay spreading. Multi-carrier CDMA is one of effective techniques to mitigate the ISI. It is an integrated modulation method of Orthogonal Frequency Division Multiplexing (OFDM) and Code Division Multiple Access (CDMA) technologies. In a quasi-synchronous code-division multiple-access (QS-CDMA) system, loosely synchronous (LS) code can eliminate inter symbol interference (ISI) and multiple access interference (MAI) by using zero correlation zone (ZCZ). Generalized LS (GLS) code is a general description of LS code. Adjacent cell interference (ACI) can be minimized by applying GLS in QS-CDMA system.
First of all, an improved Multi-carrier CDMA system is proposed in this thesis. Compared with conventional MC-CDMA system, the main difference is that this scheme performs the spreading in the time and frequency domain simultaneously. This system can utilize the transmission bandwidth more efficiently and achieve frequency diversity. Furthermore, this system lowers the data rate of each carrier branch, so it is easier to make spreading sequence synchronized than the conventional system. Then the performance of the system is analyzed in a Rayleigh fading channel in this thesis.
Next, based on the Gaussian approximation method, the bit error rate of multiple cellular QS-CDMA system using a GLS code family and scrambled LS codes is estimated and their simulations and performance comparison are presented. It is shown that the GLS code improve the system performance greatly, much better than the LS code.
Finally, generalized loosely synchronous (GLS) codes are applied to the MC-DS-CDMA system and the bit error rate of the new system is obtained. The system overcomes MAI of OFDM when there is frequency offset because of the ZCZ characteristic of GLS code. The simulation result shows that the system using GLS code performs better than the MC-DS-CDMA using Walsh sequence, and has high frequency utilizing rate.
本文首先提出了一种改进的多载波码分多址(MC／CDMA)系统。与传统的MC-CDMA系统相比，其主要区别是该方案同时在时域和频域进行扩频。这种系统能更有效地利用传输带宽，实现频率分集。由于该系统降低了每个子载波上的数据速率，扩频序列更容易同步。最后给出了在瑞利衰落信道下的性能分析。
其次本文用高斯近似的方法得出了应用GLS码的多小区QS-CDMA的系统的误码性能。并且与基于LS码的QS-CDMA系统，进行了仿真分析与比较。分析结果表明，与LS码相比，GLS码显著地改善了系统的性能。
最后本文把GLS码应用在MC-DS-CDMA中，并得出了系统的误码性能。该系统利用GLS所具有的零相关区特性克服了OFDM系统存在频偏时的多用户接入干扰(MAI)。结果表明，该系统比之使用Walsh序列的MC-DS-CDMA系统有更好的误码性能，并且有更高的频谱利用率。
High-rate data transmission becomes indispensable for nowadays and future mobile communication system. However, when the data is being transferred in mobile channel, there will be inter-symbol interference (ISI) because of delay spreading. Multi-carrier CDMA is one of effective techniques to mitigate the ISI. It is an integrated modulation method of Orthogonal Frequency Division Multiplexing (OFDM) and Code Division Multiple Access (CDMA) technologies. In a quasi-synchronous code-division multiple-access (QS-CDMA) system, loosely synchronous (LS) code can eliminate inter symbol interference (ISI) and multiple access interference (MAI) by using zero correlation zone (ZCZ). Generalized LS (GLS) code is a general description of LS code. Adjacent cell interference (ACI) can be minimized by applying GLS in QS-CDMA system.
First of all, an improved Multi-carrier CDMA system is proposed in this thesis. Compared with conventional MC-CDMA system, the main difference is that this scheme performs the spreading in the time and frequency domain simultaneously. This system can utilize the transmission bandwidth more efficiently and achieve frequency diversity. Furthermore, this system lowers the data rate of each carrier branch, so it is easier to make spreading sequence synchronized than the conventional system. Then the performance of the system is analyzed in a Rayleigh fading channel in this thesis.
Next, based on the Gaussian approximation method, the bit error rate of multiple cellular QS-CDMA system using a GLS code family and scrambled LS codes is estimated and their simulations and performance comparison are presented. It is shown that the GLS code improve the system performance greatly, much better than the LS code.
Finally, generalized loosely synchronous (GLS) codes are applied to the MC-DS-CDMA system and the bit error rate of the new system is obtained. The system overcomes MAI of OFDM when there is frequency offset because of the ZCZ characteristic of GLS code. The simulation result shows that the system using GLS code performs better than the MC-DS-CDMA using Walsh sequence, and has high frequency utilizing rate.
引文
[1] John G. Proakis. Digital Communication (Fourth Edition), McGraw-Hill Publishing House
[2] 郭梯云，杨家玮，李建东编著．数字移动通信．第二版．北京：人民邮电出版社，2001
[3] 佟学俭，罗涛．OFDM移动通信技术原理与应用．人民邮电出版社，2003．
[4] 吴军，赵建平，吴伟陵．多载波CDMA在第三代移动通信中的应用，移动通信，1998．2：26-29．
[5] Bingham, John A.C. Multicarrier modulation for data transmission: an idea whose time has come. IEEE com mag, 1990;28(5): 5-14.
[6] Yee N.,Linnartz J.P. and Fettweis G. Multi-carrier CDMA in indoor wireless radio networks. Proc. of IEEE PIMRC'93, Yokohama, Japan, 1993:109-113.
[7] Fazel K. and Papke L. On the performance of convolutionally-coded CDMA/OFDM for mobile communication system. Proc.of IEEE PIMRC'93, Yokohama, Japan:468-472.
[8] Chouly A., Brajal A. and Jourdan S. Orthogonal multicarrier techniques applied to direct sequence spread spectrum CDMA systems, IEEE Global Telecommunications Conference, GLOBECOM'93, Houston, 1993;3:1723-1728.
[9] Stirling-Gallacher R.A. and Povey GJ.R. Comparison of MC-CDMA with DS-CDMA using frequency domain and time domain RAKE receivers. Wireless personal com, 1995, 2(1-2): 105-119.
[10] Chen Q,Sousa E.S. and Pasupathy S. Performance of a coded Multi-Carrier DS-CDMA system in multi-path fading channels. Wireless personal com, 1995, 2(1-2): 167-183.
[11] Fazel K., Kaiser S. and Robertson P.etc. A concept of digital terrestrial television broadcasting. Wireless personal com, 1995, 2(1-2):9-27.
[12] Fazel K., Kaiser S. and Schnell M. A flexible and high performance cellular mobile communication system based on orthogonal multi-carrier SSMA. Wireless personal com,1995,2(1-2):121-144.
[13] Sourour E.A. and Nakagawa M. Performance of orthogonal multicarrier CDMA in a multipath fading channel. IEEE tans com, 1996;44(3):356-367
[14] Kondo S. and Milstein L.B. Performance of multicarrier DS CDMA systems, IEEE tans com, 1996;44(2):238-246.
[15] Hara S. and Prasad R. Overview of multicarrier CDMA. IEEE com mag, 1997; 35(12): 126-133.
[16] Kun-Wah Yip and Tung-Sang Ng.Tight error bounds for asynchronous multicarrier CDMA and their application. IEEE com letters, 1998;2(11):295-297.
[17] Hara S, Prasad R. Design and Performance of multicarrier CDMA systems in frequency-selective Rayleigh fading channels. IEEE trans, veh. tech, 1999; 48(5): 1584-1595.
[18] The cdma2000 ITU-R RTT Candidate Submission(0.18).
[19] Lok T.M. and wong T.F. Transmitter and receiver optimization in multicarrier CDMA systems. IEEE trans com, 2000;48(7): 1197-1207.
[20] 吴伟陵，《移动通信中的关键技术》，北京邮电大学初本社，2000：233-255．
[21] Lie-Liang Yang and Hanzo L. Performance of generalized multicarrier DS-CDMA over Nakagami-m fading channels. IEEE trans com, 2002;50(6): 956-966.
[22] Fujii, T. and Nakagawa, M. Code selecting peak power reduction for MC-CDMA. IEEE Wireless communications and networking conference(WCNC)2002, 17th-21st, Mar 2002, Vol. 1:482-486.
[23] Kalofonos D.N., Stojanovic M. and Proakis J.G. Performance of adaptive MC-CDMA detectors in rapidly fading Rayleigh channels. IEEE trans wireless com, 2003;2(2): 229-239.
[24] You C.W. and Hong D.S. Multicarrier CDMA systems using time-domain and frequency-domain spreading codes. IEEE trans com, 2003;51(1): 17-21.
[25] Shannon C.E..Communication in the presence of Noise. Bell System Techmology Journal. Vol. 27, 1948.
[26] N.J.A. Sloane and A.D.Wyner. Shannon C.E.: Collected Papers. New York: IEEE. 1993
[27] 查光明等．扩频通信．西安，西安电子科技大学出版社．2001．1
[28] 沈允春著．扩谱技术．北京，国防工业出版社．1995．7
[29] 胡建栋，郑朝晖，龙必起等，码分多址与个人通信．人民邮电出版社，1996．
[30] 梅文华，杨义先，跳频通信编码地址理论．国防工业出版社，1996．
[31] A．J．维特比著，李世鹤，鲍刚，彭容译，CDMA扩频通信原理．人民邮电出版社，1997．
[32] 杨小勇．基于可视化仿真的MC-CDMA系统若干关键技术研究．北京工业大学硕士论文．2002．4
[33] 杨栋．MC-CDMA下行链路中的关键技术．西安电子科技大学硕士论文．2002．1
[34] Reimers U..DVB-T: the COFDM-based system for terrestrial television. Electronics and Communication Engineering Journal. Feb. 1997
[35] W.Y.zou, Y WU.COFDM: an overview IEEE transaction on Broadcasting. Mar 1995,vol.41,no. 1
[36] Y.Wu,et.al. OFDM for digital television terrestrial distribution over channel with multipath and non-linear distortions. Proceedings of IntL. Workshop on HDTV'94, Torino, ltaly,.Oct 1994
[37] 杨晓春，何建吾．OFDM无线局域网．北京：电子工业出版社．2003．3
[38] V.M.DaSilva and E.S.Sousa. Performance of orthogonal CDMA codes for quasisynchronous communication systems. in Proceedings IEEE ICUPC'93, pp.995-999, Ottawa, Canada.Oct.1993.
[39] L.Vandendorpe. Multitone direct sequence CDMA system in an indoor wireless environment. Proceedings IEEE First Symposium of Communications and Vehicular Technology, Delft, The Netherlands,.Oct. 1993. 41.1-4. 1. 8.
[40] Ramjee Prasad, Shinsuke Hara. An Overview of Multi-Carrier CDMA, Porc, of IEEE ISSSTA,1996,pp.107-114
[41] POPOVIC B M. Spreading sequences for multi-carrier CDMA systems. IEEE Transactions on Communications, 1999,47(6): 918-926.
[42] WONG C Y, CHENG R S, LETAIEF K B, et al. Multiuser OFDM with adaptive subcarrier bit and power allocation. IEEE J Select Areas Commun. 1999,17 (10): 1747-1757.
[43] Victor M. Dasilva, Elvino S. Sousa, Multicarrier orthogonal CDMA signals for quasi-synchronous communications systems, IEEE on J. on SAC, 1994, 12(5), 842-852.
[44] HARA S, MOURI M, OKADA M, ef ul. Transmission performance analysis of multicarrier modulation in frequency selective fast Rayleigh fading channel. Wireless Personal Commun, 1995, 2 (4): 335-356.
[45]李道本,一种具有零相关窗的扩频多址编码方法,国际专利,专利号00801970.3,2000.2.17
[46] Xiaohu Tang, Wai Ho Mow, Design of Spreading Codes for Quasi-Synchronous CDMA With Intercell Interference, IEEE Journal on Selected Areas in Commun., Jan.2006, 24(1):84-93.
[47] P. Z. Fan. Spreading sequence design and theoretical limits for quasisynchronous CDMA systems. EURASIP Journal on Wireless Communications and Networking, 2004,2004(1): 19-31.
[48] S. Sta'nczak, H. Boche and M. Haardt.Are LAS codes a miracle? IEEE GLOBECOM'01, San Antonio, Tx, USA, Nov. 2001:25-29.
[49] B. J. Choi and L. Hanzo.On the design of LAS spreading codes. IEEE Vehicular Technology Conference, Sept. 2002, 4: 2172-2176.
[50] C.-Y. Lai, et al. On LA code performance analysis for LAS-CDMA communications. IEEE 6th CAS Symp. on Emerging Tehcnologies: Mobile and Wireless Commun., Shanghai, China, May 31-June 2, 2004.
[51] D. B. Li. A method for spread spectrum multiple access coding with zero correlation window. European Patent, EP 1257077, Nov. 2002.
[52] B. Long, P. Zhang and J. Hu. A generalized QS-CDMA system and the design of new spreading codes. IEEE Trans. Veh. Technol, Nov. 1998, 47(4): 1268-1275.
[53] W. J. van Houtum. Quasi-synchronous code-division multiple access with high-order modulation. IEEE Trans. Commun, July. 2001, 49(7): 1240-1249.
[54] J. Wang and L. B. Milstein. CDMA overlay situations for microcellular mobile communications. IEEE Trans. Commun., Feb/Mar/Apr. 1995, 43,(2/3/4): 603-614.
[55] Pursley M B. Performance evaluation for phase-coded spread-spectrum multiple-access communication-Part Ⅰ: System analysis. IEEE Trans. Commu., 1977, 25 (8):795-799
[56] Dasilva V M and Sousa E S. Multi-carrier orthogonal CDMA signals for quasi-synchronous communication systems. IEEE. Selected Areas in Commu., 1994, 12 (5):842-852.
[2] 郭梯云，杨家玮，李建东编著．数字移动通信．第二版．北京：人民邮电出版社，2001
[3] 佟学俭，罗涛．OFDM移动通信技术原理与应用．人民邮电出版社，2003．
[4] 吴军，赵建平，吴伟陵．多载波CDMA在第三代移动通信中的应用，移动通信，1998．2：26-29．
[5] Bingham, John A.C. Multicarrier modulation for data transmission: an idea whose time has come. IEEE com mag, 1990;28(5): 5-14.
[6] Yee N.,Linnartz J.P. and Fettweis G. Multi-carrier CDMA in indoor wireless radio networks. Proc. of IEEE PIMRC'93, Yokohama, Japan, 1993:109-113.
[7] Fazel K. and Papke L. On the performance of convolutionally-coded CDMA/OFDM for mobile communication system. Proc.of IEEE PIMRC'93, Yokohama, Japan:468-472.
[8] Chouly A., Brajal A. and Jourdan S. Orthogonal multicarrier techniques applied to direct sequence spread spectrum CDMA systems, IEEE Global Telecommunications Conference, GLOBECOM'93, Houston, 1993;3:1723-1728.
[9] Stirling-Gallacher R.A. and Povey GJ.R. Comparison of MC-CDMA with DS-CDMA using frequency domain and time domain RAKE receivers. Wireless personal com, 1995, 2(1-2): 105-119.
[10] Chen Q,Sousa E.S. and Pasupathy S. Performance of a coded Multi-Carrier DS-CDMA system in multi-path fading channels. Wireless personal com, 1995, 2(1-2): 167-183.
[11] Fazel K., Kaiser S. and Robertson P.etc. A concept of digital terrestrial television broadcasting. Wireless personal com, 1995, 2(1-2):9-27.
[12] Fazel K., Kaiser S. and Schnell M. A flexible and high performance cellular mobile communication system based on orthogonal multi-carrier SSMA. Wireless personal com,1995,2(1-2):121-144.
[13] Sourour E.A. and Nakagawa M. Performance of orthogonal multicarrier CDMA in a multipath fading channel. IEEE tans com, 1996;44(3):356-367
[14] Kondo S. and Milstein L.B. Performance of multicarrier DS CDMA systems, IEEE tans com, 1996;44(2):238-246.
[15] Hara S. and Prasad R. Overview of multicarrier CDMA. IEEE com mag, 1997; 35(12): 126-133.
[16] Kun-Wah Yip and Tung-Sang Ng.Tight error bounds for asynchronous multicarrier CDMA and their application. IEEE com letters, 1998;2(11):295-297.
[17] Hara S, Prasad R. Design and Performance of multicarrier CDMA systems in frequency-selective Rayleigh fading channels. IEEE trans, veh. tech, 1999; 48(5): 1584-1595.
[18] The cdma2000 ITU-R RTT Candidate Submission(0.18).
[19] Lok T.M. and wong T.F. Transmitter and receiver optimization in multicarrier CDMA systems. IEEE trans com, 2000;48(7): 1197-1207.
[20] 吴伟陵，《移动通信中的关键技术》，北京邮电大学初本社，2000：233-255．
[21] Lie-Liang Yang and Hanzo L. Performance of generalized multicarrier DS-CDMA over Nakagami-m fading channels. IEEE trans com, 2002;50(6): 956-966.
[22] Fujii, T. and Nakagawa, M. Code selecting peak power reduction for MC-CDMA. IEEE Wireless communications and networking conference(WCNC)2002, 17th-21st, Mar 2002, Vol. 1:482-486.
[23] Kalofonos D.N., Stojanovic M. and Proakis J.G. Performance of adaptive MC-CDMA detectors in rapidly fading Rayleigh channels. IEEE trans wireless com, 2003;2(2): 229-239.
[24] You C.W. and Hong D.S. Multicarrier CDMA systems using time-domain and frequency-domain spreading codes. IEEE trans com, 2003;51(1): 17-21.
[25] Shannon C.E..Communication in the presence of Noise. Bell System Techmology Journal. Vol. 27, 1948.
[26] N.J.A. Sloane and A.D.Wyner. Shannon C.E.: Collected Papers. New York: IEEE. 1993
[27] 查光明等．扩频通信．西安，西安电子科技大学出版社．2001．1
[28] 沈允春著．扩谱技术．北京，国防工业出版社．1995．7
[29] 胡建栋，郑朝晖，龙必起等，码分多址与个人通信．人民邮电出版社，1996．
[30] 梅文华，杨义先，跳频通信编码地址理论．国防工业出版社，1996．
[31] A．J．维特比著，李世鹤，鲍刚，彭容译，CDMA扩频通信原理．人民邮电出版社，1997．
[32] 杨小勇．基于可视化仿真的MC-CDMA系统若干关键技术研究．北京工业大学硕士论文．2002．4
[33] 杨栋．MC-CDMA下行链路中的关键技术．西安电子科技大学硕士论文．2002．1
[34] Reimers U..DVB-T: the COFDM-based system for terrestrial television. Electronics and Communication Engineering Journal. Feb. 1997
[35] W.Y.zou, Y WU.COFDM: an overview IEEE transaction on Broadcasting. Mar 1995,vol.41,no. 1
[36] Y.Wu,et.al. OFDM for digital television terrestrial distribution over channel with multipath and non-linear distortions. Proceedings of IntL. Workshop on HDTV'94, Torino, ltaly,.Oct 1994
[37] 杨晓春，何建吾．OFDM无线局域网．北京：电子工业出版社．2003．3
[38] V.M.DaSilva and E.S.Sousa. Performance of orthogonal CDMA codes for quasisynchronous communication systems. in Proceedings IEEE ICUPC'93, pp.995-999, Ottawa, Canada.Oct.1993.
[39] L.Vandendorpe. Multitone direct sequence CDMA system in an indoor wireless environment. Proceedings IEEE First Symposium of Communications and Vehicular Technology, Delft, The Netherlands,.Oct. 1993. 41.1-4. 1. 8.
[40] Ramjee Prasad, Shinsuke Hara. An Overview of Multi-Carrier CDMA, Porc, of IEEE ISSSTA,1996,pp.107-114
[41] POPOVIC B M. Spreading sequences for multi-carrier CDMA systems. IEEE Transactions on Communications, 1999,47(6): 918-926.
[42] WONG C Y, CHENG R S, LETAIEF K B, et al. Multiuser OFDM with adaptive subcarrier bit and power allocation. IEEE J Select Areas Commun. 1999,17 (10): 1747-1757.
[43] Victor M. Dasilva, Elvino S. Sousa, Multicarrier orthogonal CDMA signals for quasi-synchronous communications systems, IEEE on J. on SAC, 1994, 12(5), 842-852.
[44] HARA S, MOURI M, OKADA M, ef ul. Transmission performance analysis of multicarrier modulation in frequency selective fast Rayleigh fading channel. Wireless Personal Commun, 1995, 2 (4): 335-356.
[45]李道本,一种具有零相关窗的扩频多址编码方法,国际专利,专利号00801970.3,2000.2.17
[46] Xiaohu Tang, Wai Ho Mow, Design of Spreading Codes for Quasi-Synchronous CDMA With Intercell Interference, IEEE Journal on Selected Areas in Commun., Jan.2006, 24(1):84-93.
[47] P. Z. Fan. Spreading sequence design and theoretical limits for quasisynchronous CDMA systems. EURASIP Journal on Wireless Communications and Networking, 2004,2004(1): 19-31.
[48] S. Sta'nczak, H. Boche and M. Haardt.Are LAS codes a miracle? IEEE GLOBECOM'01, San Antonio, Tx, USA, Nov. 2001:25-29.
[49] B. J. Choi and L. Hanzo.On the design of LAS spreading codes. IEEE Vehicular Technology Conference, Sept. 2002, 4: 2172-2176.
[50] C.-Y. Lai, et al. On LA code performance analysis for LAS-CDMA communications. IEEE 6th CAS Symp. on Emerging Tehcnologies: Mobile and Wireless Commun., Shanghai, China, May 31-June 2, 2004.
[51] D. B. Li. A method for spread spectrum multiple access coding with zero correlation window. European Patent, EP 1257077, Nov. 2002.
[52] B. Long, P. Zhang and J. Hu. A generalized QS-CDMA system and the design of new spreading codes. IEEE Trans. Veh. Technol, Nov. 1998, 47(4): 1268-1275.
[53] W. J. van Houtum. Quasi-synchronous code-division multiple access with high-order modulation. IEEE Trans. Commun, July. 2001, 49(7): 1240-1249.
[54] J. Wang and L. B. Milstein. CDMA overlay situations for microcellular mobile communications. IEEE Trans. Commun., Feb/Mar/Apr. 1995, 43,(2/3/4): 603-614.
[55] Pursley M B. Performance evaluation for phase-coded spread-spectrum multiple-access communication-Part Ⅰ: System analysis. IEEE Trans. Commu., 1977, 25 (8):795-799
[56] Dasilva V M and Sousa E S. Multi-carrier orthogonal CDMA signals for quasi-synchronous communication systems. IEEE. Selected Areas in Commu., 1994, 12 (5):842-852.