非相干脉冲超宽带系统同步解调算法研究
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摘要
脉冲超宽带(UWB)无线电是一种新型的无载波方式的短距离通信技术,它能以频谱衬底方式与现有的窄带和宽带通信系统共存,实现频谱的重复使用。UWB技术具有诸多的优点,它的功耗小,系统复杂度低,能够提供高速的连接和精确的定位服务。虽然UWB系统具有种种优点,但UWB的实现却面临严峻的挑战,其中最主要的一项就是UWB的同步技术。本论文围绕非相干的脉冲超宽带系统展开,在有符号间干扰和帧间干扰条件下对同步和解调问题进行了深入研究,提出了三种对抗干扰的同步和同步解调联合算法。
首先,论文提出了一种有数据辅助的差分传输参考系统帧量级同步算法。结合帧间差分编码方式和设计的训练序列,该算法利用了m序列独特的循环移位相加特性,使同步信息和m序列循环移位的相位信息一一对应。利用m序列良好的自相关特性估计该循环移位的相位信息进而捕获同步。由于m序列的自相关特性,该算法能够在有帧间干扰的情况下正常工作。
然后,论文提出了一种无数据辅助非相干方式的同步解调联合算法,该算法突出的特点是能够对抗符号间干扰和帧间干扰。该算法采用了比特到正交码字的一一映射,然后将正交码字调制到符号各帧极性的调制方式。在搜索同步参数的过程中,进行了一系列的码字匹配、信号聚合的操作,以能量检测为手段挑选所需的聚合波形,再对聚合波形按一定规则进行平均操作,使同步时刻的波形聚集最大的能量,非同步时刻的波形相互抵消产生很小的能量,搜索能量的最大值便可获得同步参数。在这个过程中,码字匹配和平均操作能够有效地抑制符号间干扰和帧间干扰。同时,利用同步过程中得到的抑制了干扰和噪声的模板也能大大提高解调的性能。
最后,论文在前一种算法的基础上提出了一种改进算法。由于最强的符号间干扰和帧间干扰来自于邻近的前一帧,那么在一个符号内,最强的干扰绝大部分来自于自身。一般来说码字的自相关特性不是理想的,对于选定的码字,它自身的干扰会在码字匹配过程残留下来,这部分残留干扰不会随着平均操作而相互抵消。因此,误比特率性能曲线在高信噪比时会有较高的平台,并且这个平台不会随着符号数量的增加而降低。针对这个问题,本文提出了一种新的信号格式,将两个符号组成一个块,在块内交替发送两个符号的帧。这样,将邻近的最强干扰由确定的模式改造成独立的随机干扰,就能在平均操作中进一步抑制这部分干扰,得到更干净的解调模板,从而在不影响同步性能的前提下改进了高信噪比时的误比特率性能。
Ultra-wideband impulse radio (UWB-IR) is a kind of underlay communication technique which has tremendous bandwidth and is able to coexist with current narrow/broad band systems. It has been considered as a promising candidate for short range indoor communication on account of several attractive features, such as low power consumption, low implementation complexity, capabilities to support high data-rate connectivity as well as the high definition ranging. Although the UWB systems enjoy so many merits, there are plenty of challenges for implementation and synchronization remains the biggest one ahead. In this paper, we focus on the noncoherent UWB systems and propose three synchronization and demodulation schemes in presence of inter-symbol interference (ISI) and inter-frame interference (IFI).
Firstly, this paper proposes a data-aided synchronization algorithm in the differential transmitted reference (DTR) UWB systems. The aided data and the m-sequence are introduced into the differential coding. It results in that pulse polarities of the training sequence are still the cyclic m-sequence. Thus the synchronization information is involved in the shift phase of the m-sequence. The proposed algorithm aims at estimating the shift phase to acquire synchronization. Taking the advantage of the m-sequence autocorrelation function, the maximum is significantly different from other values. Consequently, the noise and IFI can be mitigated effectively.
Secondly, a blind synchronization and demodulation algorithm is proposed for noncoherent receiver that is robust to ISI and IFI. The proposal aggregates the observed signals into one frame-long segment by a series of code matching and signal aggregation (CMSA) and averaging operations. Exploiting judiciously designed direct sequence (DS) spreading code, the aggregated segment suppresses interference effectively and accumulates the maximum energy at the synchronization time. Because the proposed scheme utilizes the observed signals efficiently and eliminates randomness of the source data, synchronization can be acquired rapidly. Then the aggregated segment is reused as the demodulation template which significantly improves the BER performance.
Finally, the paper proposes an improved algorithm based on the previous blind synchronization and demodulation scheme. As the severest interferences come from the closest frame ahead, for the given symbol the most interferences of this kind come from itself. As soon as the codeword is chosen, the interference pattern is set. Furthermore, this pattern will not vanish as the times of averaging operations increase. To settle this problem, the paper proposes a particular block signaling. Block is the basic transmission unit that contains two symbols. Within the block, the frames of two symbols are sent alternately. The severest interference terms close to the given signals change to independent random variables due to particular signaling and these interferences can be further brought down by the subsequent average operations. Consequently, the proposed scheme can improve the BER performance at high SNR, in the mean time, the performance of synchronization will not degrade.
首先,论文提出了一种有数据辅助的差分传输参考系统帧量级同步算法。结合帧间差分编码方式和设计的训练序列,该算法利用了m序列独特的循环移位相加特性,使同步信息和m序列循环移位的相位信息一一对应。利用m序列良好的自相关特性估计该循环移位的相位信息进而捕获同步。由于m序列的自相关特性,该算法能够在有帧间干扰的情况下正常工作。
然后,论文提出了一种无数据辅助非相干方式的同步解调联合算法,该算法突出的特点是能够对抗符号间干扰和帧间干扰。该算法采用了比特到正交码字的一一映射,然后将正交码字调制到符号各帧极性的调制方式。在搜索同步参数的过程中,进行了一系列的码字匹配、信号聚合的操作,以能量检测为手段挑选所需的聚合波形,再对聚合波形按一定规则进行平均操作,使同步时刻的波形聚集最大的能量,非同步时刻的波形相互抵消产生很小的能量,搜索能量的最大值便可获得同步参数。在这个过程中,码字匹配和平均操作能够有效地抑制符号间干扰和帧间干扰。同时,利用同步过程中得到的抑制了干扰和噪声的模板也能大大提高解调的性能。
最后,论文在前一种算法的基础上提出了一种改进算法。由于最强的符号间干扰和帧间干扰来自于邻近的前一帧,那么在一个符号内,最强的干扰绝大部分来自于自身。一般来说码字的自相关特性不是理想的,对于选定的码字,它自身的干扰会在码字匹配过程残留下来,这部分残留干扰不会随着平均操作而相互抵消。因此,误比特率性能曲线在高信噪比时会有较高的平台,并且这个平台不会随着符号数量的增加而降低。针对这个问题,本文提出了一种新的信号格式,将两个符号组成一个块,在块内交替发送两个符号的帧。这样,将邻近的最强干扰由确定的模式改造成独立的随机干扰,就能在平均操作中进一步抑制这部分干扰,得到更干净的解调模板,从而在不影响同步性能的前提下改进了高信噪比时的误比特率性能。
Ultra-wideband impulse radio (UWB-IR) is a kind of underlay communication technique which has tremendous bandwidth and is able to coexist with current narrow/broad band systems. It has been considered as a promising candidate for short range indoor communication on account of several attractive features, such as low power consumption, low implementation complexity, capabilities to support high data-rate connectivity as well as the high definition ranging. Although the UWB systems enjoy so many merits, there are plenty of challenges for implementation and synchronization remains the biggest one ahead. In this paper, we focus on the noncoherent UWB systems and propose three synchronization and demodulation schemes in presence of inter-symbol interference (ISI) and inter-frame interference (IFI).
Firstly, this paper proposes a data-aided synchronization algorithm in the differential transmitted reference (DTR) UWB systems. The aided data and the m-sequence are introduced into the differential coding. It results in that pulse polarities of the training sequence are still the cyclic m-sequence. Thus the synchronization information is involved in the shift phase of the m-sequence. The proposed algorithm aims at estimating the shift phase to acquire synchronization. Taking the advantage of the m-sequence autocorrelation function, the maximum is significantly different from other values. Consequently, the noise and IFI can be mitigated effectively.
Secondly, a blind synchronization and demodulation algorithm is proposed for noncoherent receiver that is robust to ISI and IFI. The proposal aggregates the observed signals into one frame-long segment by a series of code matching and signal aggregation (CMSA) and averaging operations. Exploiting judiciously designed direct sequence (DS) spreading code, the aggregated segment suppresses interference effectively and accumulates the maximum energy at the synchronization time. Because the proposed scheme utilizes the observed signals efficiently and eliminates randomness of the source data, synchronization can be acquired rapidly. Then the aggregated segment is reused as the demodulation template which significantly improves the BER performance.
Finally, the paper proposes an improved algorithm based on the previous blind synchronization and demodulation scheme. As the severest interferences come from the closest frame ahead, for the given symbol the most interferences of this kind come from itself. As soon as the codeword is chosen, the interference pattern is set. Furthermore, this pattern will not vanish as the times of averaging operations increase. To settle this problem, the paper proposes a particular block signaling. Block is the basic transmission unit that contains two symbols. Within the block, the frames of two symbols are sent alternately. The severest interference terms close to the given signals change to independent random variables due to particular signaling and these interferences can be further brought down by the subsequent average operations. Consequently, the proposed scheme can improve the BER performance at high SNR, in the mean time, the performance of synchronization will not degrade.
引文
[1]M. Z. Win and R. A. Scholtz, "Impulse radio:How it works," IEEE Commun. Lett., vol.2, no.2, pp.36-38, Feb.1998.
[2]L. Yang and G. Giannakis, "Ultra-wideband communications:An idea whose time has come," IEEE Signal Process. Mag., vol.21, no.6, pp.26-54, Nov.2004.
[3]R. A. Scholtz, "Multiple access with time-hopping impulse modulation," in Proc. of MILCOM Conf., Boston, MA,USA,1993, pp.447-450.
[4]FCC First Report and Order:In the matter of Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems, FCC 02-48, April 2002.
[5]D. Geer, "UWB standardization effort ends in controversy," COMPUTER-IEEE COMPUTER SOCIETY-, vol.39, no.7, pp.13-16,2006.
[6]Z. Tian and G. B. Giannakis, "A GLRT approach to data-aided timing acquisition in UWB radios-Part Ⅰ and Ⅱ," IEEE Trans. Wireless Commun., vol.4, no.6, pp. 2956-2967 and 2994-3004, Nov.,2005.
[7]L. Yang, Z. Tian, and G. B. Giannakis, "Non-data aided timing acquisition of ultra-wideband transmissions using cyclostationarity," in Proc. Int. Conf. Acoust., Speech, Signal Process., Hong Kong, China, Apr.6-10,2003, pp.121-124.
[8]L. Yang and G. B. Giannakis, "Timing ultra-wideband signals with dirty templates," IEEE Trans. Commun., vol.53, no.11, pp.1952-1963, Nov.2005.
[9]C. Carbonelli and U. Mengali, "Synchronization algorithms for UWB signals," IEEE Trans. Commun., vol.54, no.2, pp.329-338, Feb.2006.
[10]D. H. Shin, Y. H. Cho and D. J. Park, "A new synchronization scheme exploiting mean energy profile in UWB non-coherent receiver," in Proc. IEEE ICC'06, vol. 12, Jun.2006, pp.5721-5725.
[11]Clabangh, D.J., Temple, M.A., Raines, R.A., Canadeo, C.M., " UWB multiple aeeess Performance using time hopped pulse position modulation with biorthogonal signaling," in 2003 IEEE Conference on Ultra Wideband Systems and Technologies, pp.330-333, Nov.2003.
[12]A. Saleh and R.Valenzuela, "A statistical model for indoor multipath propagation," IEEE Journal on Selected Areas of Communications, vol.5, no.2, Feb1987,pp.128-137.
[13]J. Foerster, "Channel Modeling Subcommittee Report Final (doc.: IEEE802-15-02/490rl-SG3a). IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs), Feb.2002."
[14]D. Cassioli, M. Win, F. Vatalaro, and A. Molisch, "Performance of low-complexity RAKE reception in a realistic UWB channel," in IEEE International Conference on Communications,2002. ICC 2002, vol.2,2002, pp. 763-767.
[15]K. Witrisal, G. Leus, G. Janssen, M. Pausini, F. Troesch, T. Zasowski, and J. Romme, "Noncoherent ultra-wideband systems," IEEE Signal Processing Mag, 2009.
[16]R. Hoctor, H. Tomlinson, G. Res, and N. Niskayuna, "Delay-hopped transmitted-reference RF communications," in 2002 IEEE Conference on Ultra Wideband Systems and Technologies,2002. Digest of Papers,2002, pp. 265-269.
[17]Zhang H. and Goeckel D. L., "Generalized transmitted-reference UWB systems," in IEEE Conference on Ultra Wideband Systems and Technologies, pp.147-151, Nov.2003.
[18]Y.-L. Chao and R. A. Scholtz, "Optimal and suboptimal receivers for ultra-wideband transmitted reference systems," in Proc. IEEE Global Telecommun. Conf., Dec.2003, pp.759-763.
[19]M. Ho, V. Somayazulu, J. Foerster, and S. Roy, "A differential detector for an ultra-wideband communications system," in IEEE 55th Vehicular Technology Conference,2002. VTC Spring 2002, vol.4,2002, pp.1896-1900.
[20]R. Zhang, X. Dong, "Synchronization and Integration Region Optimization for UWB Signals with Non-coherent Detection and Auto-correlation Detection," IEEE Transactions on Communications, vol.56, no.5, pp.790-798, May 2008.
[21]Liu Biao, Lv Tiejun and Qiao Yongwei, "A Novel Synchronization Algorithm in Ultra-wideband System," in 2009 IEEE International Conference on Ultra-Wideband, ICUWB 2009, pp.556-559.
[22]G. Tchere, P. Ubolkosold, S. Knedlik, O. Loffeld, and K. Witrisal, "Data-Aided Timing Acquisition in UWB Differential Transmitted Reference Systems," in 2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications,2006, pp.1-5.
[23]A. D'Amico, U. Mengali, and L. Taponecco, "Synchronization for Differential Transmitted Reference UWB Receivers," IEEE Transactions on Wireless Communications, vol.6, no.11, pp.4154-4163,2007.
[24]M. Di Renzo, F. Graziosi, and F. Santucci, "A modified Delay Locked Loop synchronizer for ranging-based fine timing acquisition of Differential Transmitted Reference UWB receivers," in Wireless Conference,2008. EW 2008. 14th European,2008, pp.1-6.
[25]L. Yang, H. Zhang, and F. Yu, "A Novel Timing Acquisition Algorithm for Differential Transmitted Reference UWB Receivers," in Computing, Communication, Control, and Management,2008. CCCM'08. ISECS International Colloquium on, vol.2,2008.
[26]F. Zeng and L. Ge, "An algorithm for cycle and add property of m sequence," in 2003 IEEE Information Theory Workshop,2003. Proceedings, pp.119-122.
[27]B. Liu, T. Lv and H. Gao, "Blind Synchronization and Demodulation for Noncoherent Ultra-Wideband System with Robustness against ISI and IFI", in 2010 IEEE International Conference on Communications, ICC 2010. (to appear)
[28]Y. Ying, M. Ghogho, and A. Swami, "Block-Coded Modulation and Noncoherent Detection for Impulse Radio UWB," IEEE Signal Processing Letters, vol.15, pp. 112-115,2008.
[29]V. Lottici, L. Wu, and Z. Tian, "Inter-symbol interference mitigation in high-data-rate uwb systems," in IEEE International Conference on Communications,2007. ICC'07,2007, pp.4299-4304.
[30]M. Sahin and H. Arslan, "Inter-symbol interference in high data rate UWB communications using energy detector receivers," in 2005 IEEE International Conference on Ultra-Wideband,2005. ICU 2005,2005, pp.176-179.
[31]M. Pausini, G. Janssen, and K. Witrisal, "Performance enhancement of differential UWB autocorrelation receivers under ISI," IEEE Journal on Selected Areas in Communications, vol.24, no.4 Part 1, pp.815-821,2006.
[32]X. Luo and G. Giannakis, "Low-complexity blind synchronization and demodulation for (ultra-) wideband multi-user ad hoc access," IEEE Transactions on Wireless Communications, vol.5, no.7, pp.1930-1941,2006.
[33]L. Yang, and G. B. Giannakis, "Optimal pilot waveform assisted modulation for ultrawideband communications," IEEE Trans. Wireless Commun., vol.3, no.4, pp.1236-1249, Jul.2004.
[34]K. Witrisal, M. Pausini, "Statistical Analysis of UWB Channel Correlation Functions," IEEE Trans. Vehicular Technology, vol.57, no.3, pp 1359-1373, May 2008.
[2]L. Yang and G. Giannakis, "Ultra-wideband communications:An idea whose time has come," IEEE Signal Process. Mag., vol.21, no.6, pp.26-54, Nov.2004.
[3]R. A. Scholtz, "Multiple access with time-hopping impulse modulation," in Proc. of MILCOM Conf., Boston, MA,USA,1993, pp.447-450.
[4]FCC First Report and Order:In the matter of Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems, FCC 02-48, April 2002.
[5]D. Geer, "UWB standardization effort ends in controversy," COMPUTER-IEEE COMPUTER SOCIETY-, vol.39, no.7, pp.13-16,2006.
[6]Z. Tian and G. B. Giannakis, "A GLRT approach to data-aided timing acquisition in UWB radios-Part Ⅰ and Ⅱ," IEEE Trans. Wireless Commun., vol.4, no.6, pp. 2956-2967 and 2994-3004, Nov.,2005.
[7]L. Yang, Z. Tian, and G. B. Giannakis, "Non-data aided timing acquisition of ultra-wideband transmissions using cyclostationarity," in Proc. Int. Conf. Acoust., Speech, Signal Process., Hong Kong, China, Apr.6-10,2003, pp.121-124.
[8]L. Yang and G. B. Giannakis, "Timing ultra-wideband signals with dirty templates," IEEE Trans. Commun., vol.53, no.11, pp.1952-1963, Nov.2005.
[9]C. Carbonelli and U. Mengali, "Synchronization algorithms for UWB signals," IEEE Trans. Commun., vol.54, no.2, pp.329-338, Feb.2006.
[10]D. H. Shin, Y. H. Cho and D. J. Park, "A new synchronization scheme exploiting mean energy profile in UWB non-coherent receiver," in Proc. IEEE ICC'06, vol. 12, Jun.2006, pp.5721-5725.
[11]Clabangh, D.J., Temple, M.A., Raines, R.A., Canadeo, C.M., " UWB multiple aeeess Performance using time hopped pulse position modulation with biorthogonal signaling," in 2003 IEEE Conference on Ultra Wideband Systems and Technologies, pp.330-333, Nov.2003.
[12]A. Saleh and R.Valenzuela, "A statistical model for indoor multipath propagation," IEEE Journal on Selected Areas of Communications, vol.5, no.2, Feb1987,pp.128-137.
[13]J. Foerster, "Channel Modeling Subcommittee Report Final (doc.: IEEE802-15-02/490rl-SG3a). IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs), Feb.2002."
[14]D. Cassioli, M. Win, F. Vatalaro, and A. Molisch, "Performance of low-complexity RAKE reception in a realistic UWB channel," in IEEE International Conference on Communications,2002. ICC 2002, vol.2,2002, pp. 763-767.
[15]K. Witrisal, G. Leus, G. Janssen, M. Pausini, F. Troesch, T. Zasowski, and J. Romme, "Noncoherent ultra-wideband systems," IEEE Signal Processing Mag, 2009.
[16]R. Hoctor, H. Tomlinson, G. Res, and N. Niskayuna, "Delay-hopped transmitted-reference RF communications," in 2002 IEEE Conference on Ultra Wideband Systems and Technologies,2002. Digest of Papers,2002, pp. 265-269.
[17]Zhang H. and Goeckel D. L., "Generalized transmitted-reference UWB systems," in IEEE Conference on Ultra Wideband Systems and Technologies, pp.147-151, Nov.2003.
[18]Y.-L. Chao and R. A. Scholtz, "Optimal and suboptimal receivers for ultra-wideband transmitted reference systems," in Proc. IEEE Global Telecommun. Conf., Dec.2003, pp.759-763.
[19]M. Ho, V. Somayazulu, J. Foerster, and S. Roy, "A differential detector for an ultra-wideband communications system," in IEEE 55th Vehicular Technology Conference,2002. VTC Spring 2002, vol.4,2002, pp.1896-1900.
[20]R. Zhang, X. Dong, "Synchronization and Integration Region Optimization for UWB Signals with Non-coherent Detection and Auto-correlation Detection," IEEE Transactions on Communications, vol.56, no.5, pp.790-798, May 2008.
[21]Liu Biao, Lv Tiejun and Qiao Yongwei, "A Novel Synchronization Algorithm in Ultra-wideband System," in 2009 IEEE International Conference on Ultra-Wideband, ICUWB 2009, pp.556-559.
[22]G. Tchere, P. Ubolkosold, S. Knedlik, O. Loffeld, and K. Witrisal, "Data-Aided Timing Acquisition in UWB Differential Transmitted Reference Systems," in 2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications,2006, pp.1-5.
[23]A. D'Amico, U. Mengali, and L. Taponecco, "Synchronization for Differential Transmitted Reference UWB Receivers," IEEE Transactions on Wireless Communications, vol.6, no.11, pp.4154-4163,2007.
[24]M. Di Renzo, F. Graziosi, and F. Santucci, "A modified Delay Locked Loop synchronizer for ranging-based fine timing acquisition of Differential Transmitted Reference UWB receivers," in Wireless Conference,2008. EW 2008. 14th European,2008, pp.1-6.
[25]L. Yang, H. Zhang, and F. Yu, "A Novel Timing Acquisition Algorithm for Differential Transmitted Reference UWB Receivers," in Computing, Communication, Control, and Management,2008. CCCM'08. ISECS International Colloquium on, vol.2,2008.
[26]F. Zeng and L. Ge, "An algorithm for cycle and add property of m sequence," in 2003 IEEE Information Theory Workshop,2003. Proceedings, pp.119-122.
[27]B. Liu, T. Lv and H. Gao, "Blind Synchronization and Demodulation for Noncoherent Ultra-Wideband System with Robustness against ISI and IFI", in 2010 IEEE International Conference on Communications, ICC 2010. (to appear)
[28]Y. Ying, M. Ghogho, and A. Swami, "Block-Coded Modulation and Noncoherent Detection for Impulse Radio UWB," IEEE Signal Processing Letters, vol.15, pp. 112-115,2008.
[29]V. Lottici, L. Wu, and Z. Tian, "Inter-symbol interference mitigation in high-data-rate uwb systems," in IEEE International Conference on Communications,2007. ICC'07,2007, pp.4299-4304.
[30]M. Sahin and H. Arslan, "Inter-symbol interference in high data rate UWB communications using energy detector receivers," in 2005 IEEE International Conference on Ultra-Wideband,2005. ICU 2005,2005, pp.176-179.
[31]M. Pausini, G. Janssen, and K. Witrisal, "Performance enhancement of differential UWB autocorrelation receivers under ISI," IEEE Journal on Selected Areas in Communications, vol.24, no.4 Part 1, pp.815-821,2006.
[32]X. Luo and G. Giannakis, "Low-complexity blind synchronization and demodulation for (ultra-) wideband multi-user ad hoc access," IEEE Transactions on Wireless Communications, vol.5, no.7, pp.1930-1941,2006.
[33]L. Yang, and G. B. Giannakis, "Optimal pilot waveform assisted modulation for ultrawideband communications," IEEE Trans. Wireless Commun., vol.3, no.4, pp.1236-1249, Jul.2004.
[34]K. Witrisal, M. Pausini, "Statistical Analysis of UWB Channel Correlation Functions," IEEE Trans. Vehicular Technology, vol.57, no.3, pp 1359-1373, May 2008.