带内数模同频广播系统的迭代接收技术研究
摘要
目前,数字化已经成为世界广播发展的必然趋势,CDRadio(China Digital Radio)是中国数字音频广播标准方案,专门针对中国调频广播而设计。此系统创新的在FM原有频段上同时播放数字信号,OFDM信号并不占用额外带宽,保持基础设施和频率划分不变,顺利实现了从模拟广播到数字广播的平滑过渡。
本文首先详细描述了CDRadio数字音频广播系统具体的系统架构,包括上位机、激励器和软接收机部分,并对各部分具体的模块实现进行原理以及算法编码设计说明。
针对CDRadio系统中最核心的带内同频数模分离部分,通过研究,创新地提出了前端预处理算法和卡尔曼联合测量模型滤波(Extended Combined Measurement Kalman filter,ECMKF)分离算法。其中前端预处理算法通过设计OFDM信号循环前缀,使同频数模分离转变为同频FM信号分离,有效减少了分离过程对OFDM信号造成的失真影响。ECMKF算法则是在传统的卡尔曼自适应滤波过程加入联合量测模型,有效克服了传统卡尔曼分离算法分离同频FM信号时所产生的交错分离现象。同时ECMKF算法会消除噪声等干扰信号,所以性能比维特比算法有很大提升。
同步算法也是接收技术的一个关键点,本文研究了该系统的同步算法,对三种现有算法——基于循环前缀的ML算法,基于训练序列的Schmidt&Cox算法和Park算法进行了仿真和改进,其中改进后的Park适用算法可以有效降低算法的复杂度,并且能够显著提高系统的性能,对于同步算法来说,是一个较好的选择。
文章最后研究了OFDM数字作为干扰信号对FM模拟信号的影响。利用三种常见的FM解调算法公式对混合信号进行FM解调,通过仿真及场测等手段评估了OFDM数字信号对FM信号的影响,评测指标为失真度和信噪比,这对发送端控制数模发射功率比有重要意义。
Digitization has become the inevitable trend of the development of world radio industry. China digital radio (CDRadio) broadcasting technology scheme is specifically targeted at Chinese FM radio design. China digital radio (CDRadio) system enables the existing FM radio stations to broadcast OFDM digital audio of CD-like quality (including data service) within conventional FM band simultaneously together with analog FM without any base installations or spectrum change.
At first, this paper gives the specific system architecture and coding design etc of the CDRadio digital audio broadcasting system.
Therefore, the separation of digital-analog mixed signals is of strategic importance to the system. A unique preprocessing structure is applied to convert digital-analog mixed signals into co-channel FM signals, and an innovative extended Combined Measurement Kalman filter (ECMKF) algorithm, namely predicting and estimating the original signals with more than one observation from the preprocessing structure, is put forward to avoid the crisscross separation effectively. Simulation results show that, compared with the Viterbi [2] algorithm,the innovative ECMKF algorithm gains much better performance for considering the noise.
In this paper, for kinds of synchronization algorithms of the system are investigated:ML, Schmidt&Cox, Park. By improving existing algorithms and simulation, the applied Park algorithm is a good choice with better performance and lower complexity.
Evaluating the impact of OFDM on FM demodulation gives the reference for selecting OFDM to FM power ratio. The details the most popular three FM demodulation algorithm is given, extensive simulation are then conducted to evaluate the OFDM impact on FM demodulation.
本文首先详细描述了CDRadio数字音频广播系统具体的系统架构,包括上位机、激励器和软接收机部分,并对各部分具体的模块实现进行原理以及算法编码设计说明。
针对CDRadio系统中最核心的带内同频数模分离部分,通过研究,创新地提出了前端预处理算法和卡尔曼联合测量模型滤波(Extended Combined Measurement Kalman filter,ECMKF)分离算法。其中前端预处理算法通过设计OFDM信号循环前缀,使同频数模分离转变为同频FM信号分离,有效减少了分离过程对OFDM信号造成的失真影响。ECMKF算法则是在传统的卡尔曼自适应滤波过程加入联合量测模型,有效克服了传统卡尔曼分离算法分离同频FM信号时所产生的交错分离现象。同时ECMKF算法会消除噪声等干扰信号,所以性能比维特比算法有很大提升。
同步算法也是接收技术的一个关键点,本文研究了该系统的同步算法,对三种现有算法——基于循环前缀的ML算法,基于训练序列的Schmidt&Cox算法和Park算法进行了仿真和改进,其中改进后的Park适用算法可以有效降低算法的复杂度,并且能够显著提高系统的性能,对于同步算法来说,是一个较好的选择。
文章最后研究了OFDM数字作为干扰信号对FM模拟信号的影响。利用三种常见的FM解调算法公式对混合信号进行FM解调,通过仿真及场测等手段评估了OFDM数字信号对FM信号的影响,评测指标为失真度和信噪比,这对发送端控制数模发射功率比有重要意义。
Digitization has become the inevitable trend of the development of world radio industry. China digital radio (CDRadio) broadcasting technology scheme is specifically targeted at Chinese FM radio design. China digital radio (CDRadio) system enables the existing FM radio stations to broadcast OFDM digital audio of CD-like quality (including data service) within conventional FM band simultaneously together with analog FM without any base installations or spectrum change.
At first, this paper gives the specific system architecture and coding design etc of the CDRadio digital audio broadcasting system.
Therefore, the separation of digital-analog mixed signals is of strategic importance to the system. A unique preprocessing structure is applied to convert digital-analog mixed signals into co-channel FM signals, and an innovative extended Combined Measurement Kalman filter (ECMKF) algorithm, namely predicting and estimating the original signals with more than one observation from the preprocessing structure, is put forward to avoid the crisscross separation effectively. Simulation results show that, compared with the Viterbi [2] algorithm,the innovative ECMKF algorithm gains much better performance for considering the noise.
In this paper, for kinds of synchronization algorithms of the system are investigated:ML, Schmidt&Cox, Park. By improving existing algorithms and simulation, the applied Park algorithm is a good choice with better performance and lower complexity.
Evaluating the impact of OFDM on FM demodulation gives the reference for selecting OFDM to FM power ratio. The details the most popular three FM demodulation algorithm is given, extensive simulation are then conducted to evaluate the OFDM impact on FM demodulation.
引文
[1]David P. Maxson. The IBOC Handbook:Understanding HD Radio (TM) Technology [M]. USA:Focal Press,2007.
[2]张光华,门爱东.创新的中国数字调频广播技术方案—-CDRadio与HD Radio的简介与比较.电声技术,2011,(9).
[3]ITU. ITU-T Recommendation G.729 Coding of speech at 8 kbit/s using conjugate-structure algebraic-codeexcited linear-prediction (CS-ACELP) [S]. Geneva:ITU,1996.
[4]杨俊杰,黎福海G.729 Annex B简介[J].电声技术,2002(9)：10-12.
[5]D.M.L.Witherow, et al. Digital Audio Broadcasting-the future of radio. International Broadcasting Convention,1995 Conf. Publication, IEE (413):57-61.
[6]A.Anderson, et al. Development of a compact DAB receiver design for the consumer market.International broadcasting Convention,1996 Conf. Publication, IEE(428):267-271.
[7]W.H.W.Tuttlebee, et al.Consumer digital radio:from concept to reality. Electronics &Comm. Engineering Journal,1998,10(4):263-276.
[8]B. W.Kroeger, et al. Compatibility of FM hybrid In-Band On-Channel (DBOC) system for digital audio broadcasting. IEEE Trans, on Broadcasting,1997,43(4):421-430.
[9]P. Scalart, et al. Performance analysis of a COFDM/FM In-band digital audio broadcasting system. IEEE Trans, on Broadcasting,1997,43(2):191-198.
[10]D. D.Kumar. In-Band On-Channel digital audio broadcasting method and system. US006246698B1, Jun.12,2001.
[11]B. W. Kroeger, et al. FM In-Band On-Channel digital audio broadcasting method and system. US006430227B1, Aug.6,2002.
[12]B. W.Kroeger, et al. Robust modem and coding techniques for FM hybrid IBOC DAB. IEEE Trans, on Broadcasting,1997,43(4):412-420
[13]A. K.Agarwal. Method and apparatus for adaptive control
[14]Jonathan N. Bradley.Suppression of adjacent-channel and cochannel FM interference via extended Kalman filtering.Proc. ICASSP-92, vol.IV1992, pp.693-696
[15]Jon Hamkins, "An Analytic Technique to Separate Cochannel FM Signals," IEEE TRANSACTIONS ON COMMUNICATIONS, VOL.48, NO.4, APRIL 2000.
[16]David P. Maxson. The IBOC Handbook:Understanding HD Radio (TM) Technology [M]. USA:Focal Press,2007.
[17]J. G. Lawton.Investigation of analog and digital communication systems-Final report.RADC-TDR-63-147, ASTIA Doc. AD 407343, May 1965.
[18]James V. Stone. Blind Source Separation Using Temporal Predictability. Neural Computation, 13(7),2001.
[19]Alan L. Mcbride. On Optimum Sampled-Data FM Demodulation,IEEE Transactions on Communications, Vol.21, No.1. (Jan 1973), pp.40-50.
[20]Schnyder, F. et al., Implementation of FM Demodulator Algorithms on a High Performance Digital Signal Processor.Diploma Thesis, Jan.11,2002, pp.77-102.
[21]A. Gelb. Applied optimal estimation. Cambridge,MA:MIT Press,1974.
[22]James S. Meditch. Stochastic optimal linear estimation and control. New York, McGraw-Hill [1969] xiv,394 p.23 cm.
[21]Jan-Jaap van de Beek, Magnus Sandell, and Per Ola Borjesson.ML Estimation of Time and Frequency Offset in OFDM Systems [J]. IEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL.45, NO.7, JULY 1997
[22]T. M. Schmidl and D. C. Cox.Robust frequency and timing synchronization for OFDM.IEEE Trans. Commun., VOL.45, pp 1613-1621, Dec.1997.
[23]Z. Zhang, M. Zhao, H. Zhou, Y. Liu, and J. Gao. Frequency offset estimation with fast acquisition in OFDM system. IEEE Commun. Lett., VOL.8, NO.3, pp 1-173, Mar.2004.
[24]H. Nogami and T. Nagashima, A frequency and timing period acquisition technique for OFDM system. Personal, Indoor and Mobile Radio Commun. (PIMRC), pp.1010-1015, Sep. 27-29,1995.
[25]G. Santella. A frequency and symbol synchronization system for OFDM signals:architecture and simulation results.IEEE Trans. Veh. Technol., VOL.49, pp.254-275, Jan.2000.
[26]Billie J. Hunsinger et al. In band on channel broadcasting[P].1998.10
[27]Franz Schnyder, Christoph Haller. Inmplementation of FM Demodulator Algorithms on a High Performance Digital Signal Processor [EB/OL],2011.12.
[28]N.Kehtarnavaz and B.Simsek, C6x-Based Digital Signal Processing[M]. New Jersey:Prentice Hall,2000.
[2]张光华,门爱东.创新的中国数字调频广播技术方案—-CDRadio与HD Radio的简介与比较.电声技术,2011,(9).
[3]ITU. ITU-T Recommendation G.729 Coding of speech at 8 kbit/s using conjugate-structure algebraic-codeexcited linear-prediction (CS-ACELP) [S]. Geneva:ITU,1996.
[4]杨俊杰,黎福海G.729 Annex B简介[J].电声技术,2002(9)：10-12.
[5]D.M.L.Witherow, et al. Digital Audio Broadcasting-the future of radio. International Broadcasting Convention,1995 Conf. Publication, IEE (413):57-61.
[6]A.Anderson, et al. Development of a compact DAB receiver design for the consumer market.International broadcasting Convention,1996 Conf. Publication, IEE(428):267-271.
[7]W.H.W.Tuttlebee, et al.Consumer digital radio:from concept to reality. Electronics &Comm. Engineering Journal,1998,10(4):263-276.
[8]B. W.Kroeger, et al. Compatibility of FM hybrid In-Band On-Channel (DBOC) system for digital audio broadcasting. IEEE Trans, on Broadcasting,1997,43(4):421-430.
[9]P. Scalart, et al. Performance analysis of a COFDM/FM In-band digital audio broadcasting system. IEEE Trans, on Broadcasting,1997,43(2):191-198.
[10]D. D.Kumar. In-Band On-Channel digital audio broadcasting method and system. US006246698B1, Jun.12,2001.
[11]B. W. Kroeger, et al. FM In-Band On-Channel digital audio broadcasting method and system. US006430227B1, Aug.6,2002.
[12]B. W.Kroeger, et al. Robust modem and coding techniques for FM hybrid IBOC DAB. IEEE Trans, on Broadcasting,1997,43(4):412-420
[13]A. K.Agarwal. Method and apparatus for adaptive control
[14]Jonathan N. Bradley.Suppression of adjacent-channel and cochannel FM interference via extended Kalman filtering.Proc. ICASSP-92, vol.IV1992, pp.693-696
[15]Jon Hamkins, "An Analytic Technique to Separate Cochannel FM Signals," IEEE TRANSACTIONS ON COMMUNICATIONS, VOL.48, NO.4, APRIL 2000.
[16]David P. Maxson. The IBOC Handbook:Understanding HD Radio (TM) Technology [M]. USA:Focal Press,2007.
[17]J. G. Lawton.Investigation of analog and digital communication systems-Final report.RADC-TDR-63-147, ASTIA Doc. AD 407343, May 1965.
[18]James V. Stone. Blind Source Separation Using Temporal Predictability. Neural Computation, 13(7),2001.
[19]Alan L. Mcbride. On Optimum Sampled-Data FM Demodulation,IEEE Transactions on Communications, Vol.21, No.1. (Jan 1973), pp.40-50.
[20]Schnyder, F. et al., Implementation of FM Demodulator Algorithms on a High Performance Digital Signal Processor.Diploma Thesis, Jan.11,2002, pp.77-102.
[21]A. Gelb. Applied optimal estimation. Cambridge,MA:MIT Press,1974.
[22]James S. Meditch. Stochastic optimal linear estimation and control. New York, McGraw-Hill [1969] xiv,394 p.23 cm.
[21]Jan-Jaap van de Beek, Magnus Sandell, and Per Ola Borjesson.ML Estimation of Time and Frequency Offset in OFDM Systems [J]. IEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL.45, NO.7, JULY 1997
[22]T. M. Schmidl and D. C. Cox.Robust frequency and timing synchronization for OFDM.IEEE Trans. Commun., VOL.45, pp 1613-1621, Dec.1997.
[23]Z. Zhang, M. Zhao, H. Zhou, Y. Liu, and J. Gao. Frequency offset estimation with fast acquisition in OFDM system. IEEE Commun. Lett., VOL.8, NO.3, pp 1-173, Mar.2004.
[24]H. Nogami and T. Nagashima, A frequency and timing period acquisition technique for OFDM system. Personal, Indoor and Mobile Radio Commun. (PIMRC), pp.1010-1015, Sep. 27-29,1995.
[25]G. Santella. A frequency and symbol synchronization system for OFDM signals:architecture and simulation results.IEEE Trans. Veh. Technol., VOL.49, pp.254-275, Jan.2000.
[26]Billie J. Hunsinger et al. In band on channel broadcasting[P].1998.10
[27]Franz Schnyder, Christoph Haller. Inmplementation of FM Demodulator Algorithms on a High Performance Digital Signal Processor [EB/OL],2011.12.
[28]N.Kehtarnavaz and B.Simsek, C6x-Based Digital Signal Processing[M]. New Jersey:Prentice Hall,2000.