基于CMMB的信道估计算法研究
摘要
正交频分复用(OFDM)技术在宽带无线通信领域具有显著优势,因此在移动数字电视地面广播中得以广泛应用。OFDM系统中接收端通过信道估计获得对信道状态信息的估计。信道估计是接收端均衡由无线信道引起的各种衰落的必需条件。基于OFDM技术的CMMB标准,是国家广播电影电视总局颁布的具有自主知识产权的移动多媒体广播技术行业标准。本文研究基于CMMB标准的OFDM系统信道估计方案。
本文首先阐述了移动多媒体广播业务的定义和发展。本文对目前的主要移动多媒体广播标准进行了分析和比较,讨论了其中主要的物理层技术特点,指出了移动多媒体广播面临的主要挑战,论证了信道估计对移动多媒体广播传输的重要性。
本文分析了CMMB标准应用的无线移动广播信道特点,指出了信道频率选择性衰落和快衰落对无线接收信号的影响,讨论了目前广泛应用的几种无线广播信道模型。本文探讨了OFDM技术的基本原理,分析了CMMB标准的物理层主要技术和帧结构,为设计针对CMMB标准的信道估计算法奠定基础。
本文阐述了CMMB的信道估计主要算法,即基于带限频域PN序列相关估计方法、基于离散导频的信道估计方法和信道估计均方误差(MSE)的抑制方法。这些方法充分利用了CMMB标准中的信标和离散导频的接收端先验信息,具有较好的估计性能。针对CMMB物理层帧结构特点,本文设计了基于捕获-跟踪的CMMB信道估计系统方案。该方案通过对基于信标、基于离散导频信道估计及估计值的MSE抑制方法的有机结合,增强了系统抵抗频率选择性衰落和快衰落的能力。
本文搭建了无线移动广播信道仿真模型和CMMB基带传输链路平台。本文对设计的主要算法进行了仿真验证,通过MSE和误比特率(BER)对算法性能进行评估。仿真结果验证了基于带限频域PN序列相关估计算法和基于离散导频信道估计算法的可行性,讨论了不同的设计方案的性能差异。仿真结果同时显示了各种抑制估计MSE算法所带来的估计性能提升。仿真结果验证了基于捕获-跟踪的CMMB信道估计系统方案适应各种不同的广播信道环境,在同等条件下和常规算法相比获得了性能提升。
本文最后对全文工作进行了总结,并对今后工作进行了展望。
Because of significant advantages in the field of broadband wireless communications, Orthogonal Frequency Division Multiplexing (OFDM) technology has been widely applied in mobile digital TV terrestrial broadcasting systems. Channel state information can be extracted based on channel estimation methods for OFDM system receiver. Channel estimation is necessary for equalization in the wireless receiver. CMMB was issued as a mobile multimedia broadcasting technology industry standards by the State Administration of Radio, Film and Television with independent intellectual property rights. Channel estimation solution for CMMB is indicated in the thesis.
The definition and development of mobile multimedia broadcasting services are indicated. In this thesis, current major mobile multimedia broadcasting standards were analyzed and compared. Technical characteristics of PHY, importance and major challenges of channel estimation in the mobile multimedia broadcasting systems were analyzed.
Characteristics of wireless mobile radio channel for CMMB standard were analyzed. Impactions of channel frequency selective fading and fast fading were pointed out. Several widely used wireless broadcasting channel models were discussed. Basic principles of OFDM technology, PHY technology and the main frame structure of CMMB were indicated for channel estimation algorithms design.
Main CMMB channel estimation methods were indicated in the thesis. They are limited band frequency correlation PN sequence estimation methods, scatter pilots estimation methods and channel estimation Mean Square Error (MSE) suppression methods. These methods make full use of the CMMB standard of training sequences and pilots, and they have good performance. Based on CMMB PHY frame structure characteristics, Capture-Tracking CMMB Channel Estimation System Solution was proposed in the thesis. This solution makes combinations of training sequences, pilots and MSE suppression methods.
Wireless mobile radio channel simulation model and base-band transmission link CMMB simulation platform were constructed. Simulations and verifications of main channel estimation methods were performed. MSE and Bit Error Rate (BER) performance evaluation were achieved. The simulation results show feasibility of limited band frequency correlation PN sequence estimation methods and scatter pilots estimation methods. Simulation results also show performance improvements based on several channel estimation MSE suppression methods. Verification and simulation results show adaption ability of diversity broadcasting channel environments of Capture-Tracking CMMB Channel Estimation System Solution. Simulation results also show performance improvements of the solution.
Finally, the work of this thesis is summarized and some notions for the future research are given.
本文首先阐述了移动多媒体广播业务的定义和发展。本文对目前的主要移动多媒体广播标准进行了分析和比较,讨论了其中主要的物理层技术特点,指出了移动多媒体广播面临的主要挑战,论证了信道估计对移动多媒体广播传输的重要性。
本文分析了CMMB标准应用的无线移动广播信道特点,指出了信道频率选择性衰落和快衰落对无线接收信号的影响,讨论了目前广泛应用的几种无线广播信道模型。本文探讨了OFDM技术的基本原理,分析了CMMB标准的物理层主要技术和帧结构,为设计针对CMMB标准的信道估计算法奠定基础。
本文阐述了CMMB的信道估计主要算法,即基于带限频域PN序列相关估计方法、基于离散导频的信道估计方法和信道估计均方误差(MSE)的抑制方法。这些方法充分利用了CMMB标准中的信标和离散导频的接收端先验信息,具有较好的估计性能。针对CMMB物理层帧结构特点,本文设计了基于捕获-跟踪的CMMB信道估计系统方案。该方案通过对基于信标、基于离散导频信道估计及估计值的MSE抑制方法的有机结合,增强了系统抵抗频率选择性衰落和快衰落的能力。
本文搭建了无线移动广播信道仿真模型和CMMB基带传输链路平台。本文对设计的主要算法进行了仿真验证,通过MSE和误比特率(BER)对算法性能进行评估。仿真结果验证了基于带限频域PN序列相关估计算法和基于离散导频信道估计算法的可行性,讨论了不同的设计方案的性能差异。仿真结果同时显示了各种抑制估计MSE算法所带来的估计性能提升。仿真结果验证了基于捕获-跟踪的CMMB信道估计系统方案适应各种不同的广播信道环境,在同等条件下和常规算法相比获得了性能提升。
本文最后对全文工作进行了总结,并对今后工作进行了展望。
Because of significant advantages in the field of broadband wireless communications, Orthogonal Frequency Division Multiplexing (OFDM) technology has been widely applied in mobile digital TV terrestrial broadcasting systems. Channel state information can be extracted based on channel estimation methods for OFDM system receiver. Channel estimation is necessary for equalization in the wireless receiver. CMMB was issued as a mobile multimedia broadcasting technology industry standards by the State Administration of Radio, Film and Television with independent intellectual property rights. Channel estimation solution for CMMB is indicated in the thesis.
The definition and development of mobile multimedia broadcasting services are indicated. In this thesis, current major mobile multimedia broadcasting standards were analyzed and compared. Technical characteristics of PHY, importance and major challenges of channel estimation in the mobile multimedia broadcasting systems were analyzed.
Characteristics of wireless mobile radio channel for CMMB standard were analyzed. Impactions of channel frequency selective fading and fast fading were pointed out. Several widely used wireless broadcasting channel models were discussed. Basic principles of OFDM technology, PHY technology and the main frame structure of CMMB were indicated for channel estimation algorithms design.
Main CMMB channel estimation methods were indicated in the thesis. They are limited band frequency correlation PN sequence estimation methods, scatter pilots estimation methods and channel estimation Mean Square Error (MSE) suppression methods. These methods make full use of the CMMB standard of training sequences and pilots, and they have good performance. Based on CMMB PHY frame structure characteristics, Capture-Tracking CMMB Channel Estimation System Solution was proposed in the thesis. This solution makes combinations of training sequences, pilots and MSE suppression methods.
Wireless mobile radio channel simulation model and base-band transmission link CMMB simulation platform were constructed. Simulations and verifications of main channel estimation methods were performed. MSE and Bit Error Rate (BER) performance evaluation were achieved. The simulation results show feasibility of limited band frequency correlation PN sequence estimation methods and scatter pilots estimation methods. Simulation results also show performance improvements based on several channel estimation MSE suppression methods. Verification and simulation results show adaption ability of diversity broadcasting channel environments of Capture-Tracking CMMB Channel Estimation System Solution. Simulation results also show performance improvements of the solution.
Finally, the work of this thesis is summarized and some notions for the future research are given.
引文
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[3]GY/T 220.1-2006,移动多媒体广播 第1部分:广播信道帧结构、信道编码和调制[S],国家广播电影电视总局广播电视规划院,2006.
[4]TSE D,VISWANATH P.Fundamentals of Wireless Communication[M].Cambridge,UK:Cambridge Univ.Press,2005.
[5]GOLDSMITH,A.Wireless Communications[M].Cambridge,UK:Cambridge Univ.Press,2005.
[6]EN 302-304 V1.1.1,Digital Video Broadcasting(DVB);Transmission system for handheld terminals[S].European Telecommunications Standards Institute,2004.
[7]EN 300-744 V1.5.1,Digital Video Broadcasting(DVB);Framing structure,channel coding and modulation for digital terrestrial television[S].European Telecommunications Standards Institute,2004.
[8]TTA Radio Broadcasting Systems;VHF Digital Multimedia Broadcasting(DMB)to Mobile,Portable and Fixed Receivers[S],2005.
[9]ARIB STD-B31 V1.6,Transmission System for Digital Terrestrial Television Broadcasting[S],Association of Radio and Industries and Business,2005.
[10]FCL-1005,FLO~(TM)Technology Overview[M],QUALCOMM Incorporated,2007.
[11]http://www.ist-modis.org/.
[12]GB20600-2006,数字电视地面广播传输系统帧结构、信道编码和调制[S],中国国家标准化管理委员会,2006.
[13]汪云.CMMB:移动多媒体广播之路[J].中国数字电视,2006,11:22-29.
[14]李继龙.移动多媒体广播STiMi传输信道分析[J].广播与电视技术,2007,7:34-37.
[15]胡朝晖,周晓民.移动多媒体广播CMMB与T-MMB技术特点介绍[J].广播电视信息,2007,7:48-53.
[16]PARSONS D.The Mobile Radio Propagation Channel[M],New York:Wiley,1994.
[17]AMITAY N,Modeling and computer simulation of wave propagation in lineal line-of-sight microcells[J],IEEE Trans on Vehicular Technology,1992,41(4),337-342.
[18]OKUMURA Y,OHMORI E,and FUKUDA K,Field strength and its variability in VHF and UHF land mobile service[J],Review Electrical Communication Laboratory,1968,16(9-10),825-873.
[19]HATA M,Empirical formula for propagation loss in land mobile radio services[J],IEEE Trans on Vehicular Technology,1980,29(3),317-325.
[20]European Cooperative in the Field of Science and Technical Research EURO-COST 231,urban transmission loss models for mobile radio in the 900 and 1800 MHz bands,Revision 2,The Hague[R],1991,9.
[21]GUDMUNDSON M,Correlation model for shadow fading in mobile radio systems, Electronic Letters,1991,27(7),2145-2146.
[22]ALGANS A,PEDERSEN K,and MOGENSEN P,Experimental analysis of the joint statistical properties of azimuth spread,delay spread,and shadow fading[J],IEEE Journal Selected Areas Communications,2002,4,523-531.
[23]WEITZEN J and LOWE T,Measurement of angular and distance correlation properties of log-normal shadowing at 1900 MHz and its application to design of PCS systems[J],IEEE Transactions on Vehicular Technology,2002,51(2),265-273.
[24]樊昌信.通信原理(第5版)[M],国防工业出版社,2001.
[25]RICE S,Statistical properties of a sine wave plus random noise[J],Bell System Technical Journal,1947,27,109-157.
[26]ABRAMOWITZ M and STEGUN I,Handbook of Mathematical Functions[S],National Bureau of Standards,Washington,DC,1965.
[27]STUEBER G.Principles of Mobile Communication[M],Kluwer,1996.
[28]JAKES W,COX D.Mierowace Mobile Communications[M],IEEE Press,1974.
[29]PENG X,SONG J,WANG K,Counter-Set Based PCR Jitter Correction Method for DVB-T System[C],IEEE International Conference on Wireless Networking and Mobile Computing,2007,4,2940-2943.
[30]SKLAR B.Digital Communications:Fundamentals and Applications,Second Edition[M],Prentice Hall,2001.
[31]Brazilian Association of Radio and Television Broadcasters.Digital television broadcasting systems testing report in Brazil[R].2000,11.
[32]吴松炎.数字电视地面广播系统中信道估计与均衡的研究与实现.上海交通大学硕士学位论文,2006,12.
[33]唐世刚,潘长勇,龚克,杨知行.数字电视地面广播的测量与建模[J].电视技术,2005,5:8-1.
[34]Communication Research Lab Canada.Results of the laboratory evaluation of an 8MHz ADTB-T television system for terrestrial broadcasting,V3.0[R].2003,3.
[35]CHANG R,Synthesis of band-limited orthogonal signals for multichannel data transmission,Bell Systems Technical Journal[J],1966,46,1775-1796.
[36]BINGHAM J,Multicarrier modulation for data transmission:An idea whose time has come,IEEE Communication Magazine[J],1990,5,5-14.
[37]PROAKIS J.Digital Communications,Fourth edition[M].McGraw-Hill Companies,Inc,2001.
[38]CHARI M,LING F,MANTRAVADI A.FLO physical layer:an overview[J].IEEE Trans on Broadcasting,2007,53(1):145-160.
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