基于认知无线电的次用户接收机OFDM解调方案设计及FPGA实现
摘要
认知无线电(Cognitive Radio, CR)具有感知周围无线电环境的能力,能提高频谱的利用率和通信系统的容量。正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术是一种被高度认可的、能够有效提高频谱资源利用率的通信技术。将OFDM调制解调技术应用到认知无线电的次用户通信中、并在FPGA下进行方案设计与实现,是当前认知无线电技术发展的必然选择。本论文在FPGA硬件平台下研究并实现了OFDM解调器的详细实现方案。
本文首先介绍了课题背景及认知无线电和OFDM技术的研究动态及应用现状,详细阐述了OFDM调制解调的基本原理及接收端解调系统中符号同步、载波同步及信道均衡等关键技术的原理。根据项目的实际要求对物理层主要参数、帧结构以及整个OFDM接收端解调方案进行了设计。
其次重点分析了ADC采样、正交解调、低通滤波、符号同步、载波同步、速率转换、FFT解调、信道均衡、剩余相位跟踪及解扰和QAM逆映射各模块在FPGA上实现的相关算法、结构框图及处理流程,并使用VHDL语言在Altera公司的FPGA开发板上实现了OFDM解调系统。通过对最终搭建好的认知无线电验证平台进行实际测试,结果表明：本文设计并实现的OFDM解调器能够很好的完成接收端的数据解调,其功能和指标均能满足项目要求。
论文最后主要介绍了本课题中遇到的几种FPGA常用设计思想,对课题开发中遇到的实际问题进行了说明,并给出了一些常用的解决方法。
Cognitive Radio has the ability of sensing the surrounding radio environment and improving the spectrum utilization and communication capacity. Orthogonal frequency division multiplexing is a highly recognized communications technology to improve the utilization of spectrum effectively. It is inevitable for the cognitive radio technology to use OFDM modulation and demodulation technology in secondary user communications, design and put it into practice with FPGA. This paper gives the design and implementation of OFDM demodulation with FPGA hardware platform.
First, this paper gives the background of the subject, research trends and application status of cognitive radio and OFDM technology. It elaborates the basic principle of OFDM modulation and demodulation, as well as the key technical principles, including symbol synchronization, carrier synchronization and channel equalization and so on, that used in demodulation system of receiver. The main parameters and frame structure of the physical layer, as well as the entire OFDM receiver demodulator program has been designed according to the actual requirements of the project.
Second, this paper emphasizes the algorithm, block diagram and processes of modules implemented on FPGA, including ADC sampling, quadrature demodulator, low pass filtering, frame synchronization, carrier synchronization, conversion rate, the FFT demodulation, channel equalization, the remaining phase tracking and descrambling, and QAM inverse mapping. The OFDM demodulation system was built in Altera FPGA board with VHDL language. The application project worked on the cognitive radio verification platform shows that the OFDM demodulation designed in this paper could accomplish the data demodulation in the receiver, while the functions and indicators are able to meet the project requirements.
Finally, this paper gives a introduction to several common FPGA design ideas that used in the subject, descrips the practical problems encountered in the development of this subject, and gives some commonly used methods to solve them.
本文首先介绍了课题背景及认知无线电和OFDM技术的研究动态及应用现状,详细阐述了OFDM调制解调的基本原理及接收端解调系统中符号同步、载波同步及信道均衡等关键技术的原理。根据项目的实际要求对物理层主要参数、帧结构以及整个OFDM接收端解调方案进行了设计。
其次重点分析了ADC采样、正交解调、低通滤波、符号同步、载波同步、速率转换、FFT解调、信道均衡、剩余相位跟踪及解扰和QAM逆映射各模块在FPGA上实现的相关算法、结构框图及处理流程,并使用VHDL语言在Altera公司的FPGA开发板上实现了OFDM解调系统。通过对最终搭建好的认知无线电验证平台进行实际测试,结果表明：本文设计并实现的OFDM解调器能够很好的完成接收端的数据解调,其功能和指标均能满足项目要求。
论文最后主要介绍了本课题中遇到的几种FPGA常用设计思想,对课题开发中遇到的实际问题进行了说明,并给出了一些常用的解决方法。
Cognitive Radio has the ability of sensing the surrounding radio environment and improving the spectrum utilization and communication capacity. Orthogonal frequency division multiplexing is a highly recognized communications technology to improve the utilization of spectrum effectively. It is inevitable for the cognitive radio technology to use OFDM modulation and demodulation technology in secondary user communications, design and put it into practice with FPGA. This paper gives the design and implementation of OFDM demodulation with FPGA hardware platform.
First, this paper gives the background of the subject, research trends and application status of cognitive radio and OFDM technology. It elaborates the basic principle of OFDM modulation and demodulation, as well as the key technical principles, including symbol synchronization, carrier synchronization and channel equalization and so on, that used in demodulation system of receiver. The main parameters and frame structure of the physical layer, as well as the entire OFDM receiver demodulator program has been designed according to the actual requirements of the project.
Second, this paper emphasizes the algorithm, block diagram and processes of modules implemented on FPGA, including ADC sampling, quadrature demodulator, low pass filtering, frame synchronization, carrier synchronization, conversion rate, the FFT demodulation, channel equalization, the remaining phase tracking and descrambling, and QAM inverse mapping. The OFDM demodulation system was built in Altera FPGA board with VHDL language. The application project worked on the cognitive radio verification platform shows that the OFDM demodulation designed in this paper could accomplish the data demodulation in the receiver, while the functions and indicators are able to meet the project requirements.
Finally, this paper gives a introduction to several common FPGA design ideas that used in the subject, descrips the practical problems encountered in the development of this subject, and gives some commonly used methods to solve them.
引文
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[2]N.K.Hoven.On the feasibility of cognitive radio.Master of Science. University of California, Berkeley, Spring 2005.
[3]J.Mitola Ⅲ.Cognitive radio for flexible mobile multimedia Communications.Sixth International Workshop on Mobile Multimedia Communications (MoMuC'99), San Diego, CA,1999:3-10.
[4]Joseph Mitola Ⅲand Gerald Q.Maguire, JR. Cognitive radio:making software radios more personal. IEEE Personal Communications, August 1999,6(4):3-18.
[5]Speth M, Fechtel S, Fock G, Meyr H.Broadband transmission using OFDM:system performance and receiver complexity. In InternationalZurich Seminar on broadband communications, Zurich, Switzerland, Feb1998,pp.99-104.
[6]Weiss T, Hillenbrand J, and Jondral F. Spectrum pooling:an innovative strategy for the enhance-ment of spectrum efficiency.IEEE, Communications Magazine, Mar 2004,42(3):S8-S14.
[7]P.Leaves, D.Grandblaise, D.Bourse, et al.Dynamic spectrum allocation in composite reconfigurable wireless networks, IEEE Communications Magzine, May 2004, pp.72-81.
[8]End-to-End Reconfigurability, E2R_WP5_D5.3_050727, Available: http://e2r.motlabs.com/Deliverables/E2R WP5 D5.3 050727.pdf
[9]Stevenson, Carlos Cordeiro, Eli Sofer and Gerald Chouinard.Functional Requirements for the 802.22 WRAN Standard, doc.:IEEE 802.22-05/0007r40, Sept.2005.
[10]IEEE 802.22 working group on wireless regional area networks, http://WWW.ieee802.org/22/
[11]Chang R W.Synthesis of Band-limited orthogonal Signals for ultichannel Data Transmission. Bell Sys.Tech.J.1966.
[12]Peled A, Ruiz A.Frequency Domain Data Transmission Using Reduced Computational Complexity Algorithms.IEEE International Conference on Acoustics, Speech, and Signal Processing,1980,5:964-967.
[13]Weinstein S, Ebert P.Data Transmission by frequency-Division multiplexing Using the Discrete Fourier Transform.IEEE Transactions on Communications,1971,19(5):628-634.
[14]U.Dettmar, J.Khun-Jush, P.Schramm, and et al.Modulation for HIPERLAN type 2.The 49th IEEE Vehicular Technology Conference,1999,2:1094-1100
[15]ETSI.Radio broadcasting systems:Digital audio Broadcasting (DAB) to mobile, portable and fixed receivers.Tech.Rep.ETS 300 401,ETSI,May 1997.
[16]H.Sari, Gkaram, and I.Jeanclaude.Transmission techniques for digital terrestrial TV Broadcasting. IEEE Communications Magazine,1995,33(2):100-109
[17]P.S.Chow, J.C.Tu and J.M.Cioffi.Performance evaluation of a multichannel transceiver system for ADSL and VHDSL services.IEEE Journal on Selected Areas in Communications, 1991,9(6):909-919
[18]W.Y.Chen.The development and standardization of asymmetrical digital subscriber line.IEEE Communication Magazine,1999,37(5):68-72
[19]B.P.Crow, I.Widjada, J.GKim, and P.T.Sakai.IEEE 802.11 Wireless Local Area Networks. IEEE Communications Magazine,1997,35(9):116-126
[20]R.van Nee, GAwater, M.Morikura, and et al.New high-rate wireless LAN standards.IEEE Communications Magazine,1999,37(12):82-88
[21]ETSI.Broadband Radio Access Networks (BRAN); High Performance Radio Local Area Network (HIPERLAN) Type 2; requirements and architectures for wireless broadband access. Tech.Rep.TR 101 031 v2.2.1, ETSI, Jan.1999.
[22]佟学俭,罗涛.OFDM移动通信技术原理与应用.北京：人民邮电出版社,2003.
[23]程佩清.数字信号处理教程.清华大学出版社,1995.
[24]张海滨.正交频分复用的基本原理与关键技术.北京：国防工业出版社,2006.
[25]王文博,郑侃.宽带无线通信技术.北京：人民邮电出版社,2006.
[26]Heiskala J,Terry J(杨晓春,何建吾等译).OFDM无线局域网.北京：电子工业出版社,2003.
[27]史治国,洪少华,陈抗生.基于XILINX FPGA的OFDM通信系统基带设计.浙江：浙江大学出版社,2009.
[28]王秉钧,孙学军,王少勇,田宝玉.现代通信系统原理,天津出版社,1999.
[29]J J van de Beek, M Sandell, P O Borjesson ML Estimation of Time and Frequency Offset in OFDM systems. July 1977.
[30]T. M. Schmidl and D. C. Cox, "Robust frequency and timing synchronization for OFDM," IEEE Trans. on commun., Vol.45, No.12, Dec.1994.
[31]祈玉生.移动通信系统,北京,人民邮电出版社,1995.
[32]J G Proakis. Digital Communications. McGraw-Hill, Boston,4ed.,1955.
[33]John G.Proakis,张力军,张宗橙,郑宝玉.数字通信,第四版,北京：电子工业出版社,2003年1月.
[34]周炯磐,庞沁华等.通信原理(合订本),北京：北京邮电大学出版社,2005.
[35]罗仁泽,成先涛,敬龙江等.一种新的低/零自相关边峰训练序列设计方法,2005.
[36]刘宝琴,张芳兰,田立生ALTERA可编程器件及其应用,北京：清华大学出版社,1995.
[37]Altera Corporation; Cyclone III Device Handbook; Volume 1; 2009.
[38]Altera data sheet; Cyclone Devices handbook volume 1; 2005.
[39]Altera data sheet; NCO Compiler Mega Core Function User Guide; 2006.
[40]Lakshmi S. Jyothi Chimakurthy, Malinky Ghosh; A Novel DDS Using Nonlinear ROM Addressing With Improved Compression Ratio and Quantization Noise; ieee transactions on ultrasonics, ferroelectrics, and frequency control; vol.53, no.2, february 2006.
[41]Uwe Meyer-Baese著,刘凌译,数字信号处理的FPGA实现(第2版),北京：清华大学出版社,2006.
[42]田耘,徐文波,张延伟.无线通信FPGA设计,北京：电子工业出版社,2008.
[43]于继洲.集成A/D和D/A转化器应用技术,北京：国防工业出版社,1989.
[44]Uwe Meyer-Baese; A Comparison of Pipelined RAG-n and DA FPGA-based Multiplierless Filters; Circuits and Systems; 2006 IEEE Asia Pacific Conference on; Singapore.
[45]夏宇闻Verilog数字系统设计教程,北京航空航天大学出版社,2003.7.
[46]谭泽富OFDM的关键技术及应用,西南交通大学出版社,2005.
[47]潘松等.EDA技术与VHDL,北京：清华大学出版社,2007.1.
[48]Altera data sheet; Quartus Ⅱ handbook volume 1; 2005.
[49]TI Corporation; 14-BITS,125/105/80/65 MSPS ADC WITH DDR LVDS/CMOS OUTPUTS; 2007. http://www.ti.com
[50]S He, M Torkelson. Designing pipeline FFT processor for OFDM (de)modulation. ISSE, pp.257-262, Setp.1998.
[51]Nuo Li, N.P. van der Meijs. A Radix 22 based parallel pipeline FFT processor for MB-OFDM UWB system. IEEE, July 11,2010.
[52]K.Harikrishna, T. Rama Rao. An Efficient FFT Architecture for OFDM Communication Systems. IEEE, August 17,2010.
[53]吴继华,王诚等ALTERA FPGA/CPLD设计(基础篇),北京：人民邮电出版社,2005.
[54]吴继华,王诚等ALTERA FPGA/CPLD设计(高级篇),北京：人民邮电出版社,2005.
[55]谢希仁.计算机网络教程.北京：人民邮电出版社,2005.3.
[56]T.M.Schmidl, D.C.Cox. Robust frequency and timing synchronization for OFDM.IEEE Transactions on Communications,1997,45(12):1613-1621
[57]Ch.Nanda Kishore, V.U.Reddy. A new Method of Frame Synchronization and Frequency Offset Estimation in OFDM System,International Conference on Signal Processing&communications,2004.
[58]Van de Beek J J,Sandell M,Borjesson P O. ML Estimation of Time and Frequency Offset in OFDM Systems,IEEE Transactions on Signal Processing,45(7),Jul.1997.
[59]M H Hsieh, C H Wei. a Low Complexity Frame Synchronization and Frequency Offset Compensation Scheme for OFDM Systems over Fading Channels[J].IEEE Trans. Vehicular Technology,1999,48(5):1596-1609
[60]Donghoon Lee, Kyungwhoon Cheun.Coarse Symbol Synchronization Algorithms for OFDM Systems in Multipath Channels[J]. IEEE Comm.Letters,2002,6(10):446-449
[61]Arto Palin, Jukka Rinne. Symbol synchronization in OFDM system for time selective channelconditions[C].IEEE Conference.1999
[2]N.K.Hoven.On the feasibility of cognitive radio.Master of Science. University of California, Berkeley, Spring 2005.
[3]J.Mitola Ⅲ.Cognitive radio for flexible mobile multimedia Communications.Sixth International Workshop on Mobile Multimedia Communications (MoMuC'99), San Diego, CA,1999:3-10.
[4]Joseph Mitola Ⅲand Gerald Q.Maguire, JR. Cognitive radio:making software radios more personal. IEEE Personal Communications, August 1999,6(4):3-18.
[5]Speth M, Fechtel S, Fock G, Meyr H.Broadband transmission using OFDM:system performance and receiver complexity. In InternationalZurich Seminar on broadband communications, Zurich, Switzerland, Feb1998,pp.99-104.
[6]Weiss T, Hillenbrand J, and Jondral F. Spectrum pooling:an innovative strategy for the enhance-ment of spectrum efficiency.IEEE, Communications Magazine, Mar 2004,42(3):S8-S14.
[7]P.Leaves, D.Grandblaise, D.Bourse, et al.Dynamic spectrum allocation in composite reconfigurable wireless networks, IEEE Communications Magzine, May 2004, pp.72-81.
[8]End-to-End Reconfigurability, E2R_WP5_D5.3_050727, Available: http://e2r.motlabs.com/Deliverables/E2R WP5 D5.3 050727.pdf
[9]Stevenson, Carlos Cordeiro, Eli Sofer and Gerald Chouinard.Functional Requirements for the 802.22 WRAN Standard, doc.:IEEE 802.22-05/0007r40, Sept.2005.
[10]IEEE 802.22 working group on wireless regional area networks, http://WWW.ieee802.org/22/
[11]Chang R W.Synthesis of Band-limited orthogonal Signals for ultichannel Data Transmission. Bell Sys.Tech.J.1966.
[12]Peled A, Ruiz A.Frequency Domain Data Transmission Using Reduced Computational Complexity Algorithms.IEEE International Conference on Acoustics, Speech, and Signal Processing,1980,5:964-967.
[13]Weinstein S, Ebert P.Data Transmission by frequency-Division multiplexing Using the Discrete Fourier Transform.IEEE Transactions on Communications,1971,19(5):628-634.
[14]U.Dettmar, J.Khun-Jush, P.Schramm, and et al.Modulation for HIPERLAN type 2.The 49th IEEE Vehicular Technology Conference,1999,2:1094-1100
[15]ETSI.Radio broadcasting systems:Digital audio Broadcasting (DAB) to mobile, portable and fixed receivers.Tech.Rep.ETS 300 401,ETSI,May 1997.
[16]H.Sari, Gkaram, and I.Jeanclaude.Transmission techniques for digital terrestrial TV Broadcasting. IEEE Communications Magazine,1995,33(2):100-109
[17]P.S.Chow, J.C.Tu and J.M.Cioffi.Performance evaluation of a multichannel transceiver system for ADSL and VHDSL services.IEEE Journal on Selected Areas in Communications, 1991,9(6):909-919
[18]W.Y.Chen.The development and standardization of asymmetrical digital subscriber line.IEEE Communication Magazine,1999,37(5):68-72
[19]B.P.Crow, I.Widjada, J.GKim, and P.T.Sakai.IEEE 802.11 Wireless Local Area Networks. IEEE Communications Magazine,1997,35(9):116-126
[20]R.van Nee, GAwater, M.Morikura, and et al.New high-rate wireless LAN standards.IEEE Communications Magazine,1999,37(12):82-88
[21]ETSI.Broadband Radio Access Networks (BRAN); High Performance Radio Local Area Network (HIPERLAN) Type 2; requirements and architectures for wireless broadband access. Tech.Rep.TR 101 031 v2.2.1, ETSI, Jan.1999.
[22]佟学俭,罗涛.OFDM移动通信技术原理与应用.北京：人民邮电出版社,2003.
[23]程佩清.数字信号处理教程.清华大学出版社,1995.
[24]张海滨.正交频分复用的基本原理与关键技术.北京：国防工业出版社,2006.
[25]王文博,郑侃.宽带无线通信技术.北京：人民邮电出版社,2006.
[26]Heiskala J,Terry J(杨晓春,何建吾等译).OFDM无线局域网.北京：电子工业出版社,2003.
[27]史治国,洪少华,陈抗生.基于XILINX FPGA的OFDM通信系统基带设计.浙江：浙江大学出版社,2009.
[28]王秉钧,孙学军,王少勇,田宝玉.现代通信系统原理,天津出版社,1999.
[29]J J van de Beek, M Sandell, P O Borjesson ML Estimation of Time and Frequency Offset in OFDM systems. July 1977.
[30]T. M. Schmidl and D. C. Cox, "Robust frequency and timing synchronization for OFDM," IEEE Trans. on commun., Vol.45, No.12, Dec.1994.
[31]祈玉生.移动通信系统,北京,人民邮电出版社,1995.
[32]J G Proakis. Digital Communications. McGraw-Hill, Boston,4ed.,1955.
[33]John G.Proakis,张力军,张宗橙,郑宝玉.数字通信,第四版,北京：电子工业出版社,2003年1月.
[34]周炯磐,庞沁华等.通信原理(合订本),北京：北京邮电大学出版社,2005.
[35]罗仁泽,成先涛,敬龙江等.一种新的低/零自相关边峰训练序列设计方法,2005.
[36]刘宝琴,张芳兰,田立生ALTERA可编程器件及其应用,北京：清华大学出版社,1995.
[37]Altera Corporation; Cyclone III Device Handbook; Volume 1; 2009.
[38]Altera data sheet; Cyclone Devices handbook volume 1; 2005.
[39]Altera data sheet; NCO Compiler Mega Core Function User Guide; 2006.
[40]Lakshmi S. Jyothi Chimakurthy, Malinky Ghosh; A Novel DDS Using Nonlinear ROM Addressing With Improved Compression Ratio and Quantization Noise; ieee transactions on ultrasonics, ferroelectrics, and frequency control; vol.53, no.2, february 2006.
[41]Uwe Meyer-Baese著,刘凌译,数字信号处理的FPGA实现(第2版),北京：清华大学出版社,2006.
[42]田耘,徐文波,张延伟.无线通信FPGA设计,北京：电子工业出版社,2008.
[43]于继洲.集成A/D和D/A转化器应用技术,北京：国防工业出版社,1989.
[44]Uwe Meyer-Baese; A Comparison of Pipelined RAG-n and DA FPGA-based Multiplierless Filters; Circuits and Systems; 2006 IEEE Asia Pacific Conference on; Singapore.
[45]夏宇闻Verilog数字系统设计教程,北京航空航天大学出版社,2003.7.
[46]谭泽富OFDM的关键技术及应用,西南交通大学出版社,2005.
[47]潘松等.EDA技术与VHDL,北京：清华大学出版社,2007.1.
[48]Altera data sheet; Quartus Ⅱ handbook volume 1; 2005.
[49]TI Corporation; 14-BITS,125/105/80/65 MSPS ADC WITH DDR LVDS/CMOS OUTPUTS; 2007. http://www.ti.com
[50]S He, M Torkelson. Designing pipeline FFT processor for OFDM (de)modulation. ISSE, pp.257-262, Setp.1998.
[51]Nuo Li, N.P. van der Meijs. A Radix 22 based parallel pipeline FFT processor for MB-OFDM UWB system. IEEE, July 11,2010.
[52]K.Harikrishna, T. Rama Rao. An Efficient FFT Architecture for OFDM Communication Systems. IEEE, August 17,2010.
[53]吴继华,王诚等ALTERA FPGA/CPLD设计(基础篇),北京：人民邮电出版社,2005.
[54]吴继华,王诚等ALTERA FPGA/CPLD设计(高级篇),北京：人民邮电出版社,2005.
[55]谢希仁.计算机网络教程.北京：人民邮电出版社,2005.3.
[56]T.M.Schmidl, D.C.Cox. Robust frequency and timing synchronization for OFDM.IEEE Transactions on Communications,1997,45(12):1613-1621
[57]Ch.Nanda Kishore, V.U.Reddy. A new Method of Frame Synchronization and Frequency Offset Estimation in OFDM System,International Conference on Signal Processing&communications,2004.
[58]Van de Beek J J,Sandell M,Borjesson P O. ML Estimation of Time and Frequency Offset in OFDM Systems,IEEE Transactions on Signal Processing,45(7),Jul.1997.
[59]M H Hsieh, C H Wei. a Low Complexity Frame Synchronization and Frequency Offset Compensation Scheme for OFDM Systems over Fading Channels[J].IEEE Trans. Vehicular Technology,1999,48(5):1596-1609
[60]Donghoon Lee, Kyungwhoon Cheun.Coarse Symbol Synchronization Algorithms for OFDM Systems in Multipath Channels[J]. IEEE Comm.Letters,2002,6(10):446-449
[61]Arto Palin, Jukka Rinne. Symbol synchronization in OFDM system for time selective channelconditions[C].IEEE Conference.1999