LDPC-aided Decision Feedback Channel Estimation and Equalization Method

doi:10.12382/bgxb.2022.1041

Abstract

Abstract:

Under the environment of severely channel frequency selective fading, the traditional orthogonal frequency division multiplexing (OFDM) non-blind channel estimation and equalization method has poor system bit error rate performance, and needs to increase the insertion of pilot symbols in a signal, which reduces the system throughput. A low density parity check code (LDPC)- aided decision feedback channel estimation and equalization method is proposed for the above problems. The proposed method introduces the LDPC coding gain into the decision feedback loop, which improves the convergence. And it achieves the asymptotic performance of non-blind channel estimation and equalization methods under the condition of few pilot symbols inserted. Meanwhile, an improved channel estimation algorithm based on conditional maximum likelihood (CML) principle is proposed. This algorithm detects the effective tap signals based on the principle of constant false alarm to improve the channel estimation accuracy, and can be combined with the proposed decision feedback channel estimation and equalization method. The simulated results show that, under the channel environment selected in the simulation, the LDPC-aided decision feedback channel estimation and equalization method has 11-13dB improvement in bit error performance compared with the traditional decision feedback method, and has excellent system error performance and robustness.

Key words: orthogonal frequency division multiplexing, multipath channel, channel estimation and equalization, decision feedback, conditional maximum likelihood estimation

CLC Number:

TN911

LI Jiaxuan, DING Xuhui, YANG Kai, DAI Jibo, BU Xiangyuan, AN Jianping. LDPC-aided Decision Feedback Channel Estimation and Equalization Method[J]. Acta Armamentarii, 2024, 45(4): 1168-1175.

Figures/Tables 7

Fig.1 OFDM frame structure

Fig.2 Flowchart of LDPC-aided decision feedback channel estimation and equalization method

Table 1 Simulation parameters

参数	数值
前导符号数	1
数据段符号数	120
导频开销/%	0.83
子载波个数	960
子载波间隔/kHz	15
载波频率/GHz	1.43
调制方式	QPSK
LDPC码型	(480,960)
信道模型	远郊信道(COST207RA)/ 城区信道(COST207TU)
系统误码率要求	<10^-6

Fig.3 BER performance of algorithms in COST207RA channel

Fig.4 BER performance of algorithms in COST207TU channel

Fig.5 NMSE performance of algorithms in COST207RA channel

Fig.6 NMSE performance of algorithms in COST207TU channel

References 20

[1]	李有祥. 军事高技术与信息化战争[M]. 南京: 东南大学出版社, 2010.
	LI Y X. Military high technology and information warfare[M]. Nanjing: Southeast University Press, 2010. (in Chinese)
[2]	张玲. 无人机高速数据链路抗多径技术[J]. 通信技术, 2019, 52(5): 1049-1054.
	ZHANG L. Anti-multipath technology for UAV high-speed data link[J]. Communications Technology, 2019, 52(5): 1049-1054. (in Chinese)
[3]	PARK H R. A Low-complexity channel estimation for OFDM systems based on CIR length adaptation[J]. IEEE Access, 2022, 10: 85941-85951.
[4]	GAO J, LIU H P. Low-complexity MAP channel estimation for mobile MIMO-OFDM systems[J]. IEEE transactions on wireless communications, 2008, 7(3): 774-780.
[5]	ZHANG Y F, ZHU X, LIU Y J, et al. Hierarchical BEM based channel estimation with very low pilot overhead for high mobility MIMO-OFDM systems[J]. IEEE Transactions on Vehicular Technology, 2022, 71(10): 10543-10558.
[6]	EDFORS O, SANDELL M, van de BEEK J J, et al. OFDM channel estimation by singular value decomposition[J]. IEEE Transactions on communications, 1998, 46(7): 931-939.
[7]	COLERI S, ERGEN M, PURI A, et al. Channel estimation techniques based on pilot arrangement in OFDM systems[J]. IEEE Transactions on broadcasting, 2002, 48(3): 223-229.
[8]	CAI X D, AKANSU A N. A subspace method for blind channel identification in OFDM systems[C]// Proceedings of 2000 IEEE International Conference on Communications. New Orleans, LA, US: IEEE, 2000: 929-933.
[9]	LIU G H, ZHANG J L. ITD-DFE based channel estimation and equalization in TDS-OFDM receivers[J]. IEEE Transactions on Consumer Electronics, 2007, 53(2): 304-309.
[10]	李子, 蔡跃明, 阚春荣, 等. OFDM 系统中的盲信道估计[J]. 信号处理, 2005, 21(5): 508-514.
	LI Z, CAI Y M, KAN C R, et al. Blind channel estimation in OFDM systems[J]. Signal Processing, 2005, 21(5): 508-514. (in Chinese)
[11]	曹雪虹, 姚维坚. 基于正交空时编码的盲信道估计[J]. 电子学报, 2009, 37(6): 1237-1241.
	CAO X H, YAO W J. Blind channel estimation method based on OSTBCs[J]. Acta Electonica Sinica, 2009, 37(6): 1237-1241. (in Chinese)
[12]	周瑞, 郑建宏. 基于子空间分解的半盲信道估计[J]. 通信技术, 2008, 41(8): 84-86.
	ZHOU R, ZHENG J H. Semi-blind channel estimation based on subspace identification[J]. Communications Technology, 2008, 41(8): 84-86. (in Chinese)
[13]	ZHAO M, SHI Z N, REED M C. Iterative turbo channel estimation for OFDM system over rapid dispersive fading channel[J]. IEEE Transactions on Wireless Communications, 2008, 7(8): 3174-3184.
[14]	TOMASONI A, GATTI D, BELLINI S, et al. Efficient OFDM channel estimation via an information criterion[J]. IEEE transactions on wireless communications, 2013, 12(3): 1352-1362.
[15]	张晓瀛, 魏急波. OFDM系统中基于软信息处理的自适应双模半盲信道估计[J]. 电子学报, 2006, 34(10):1881-1883.
	ZHANG X Y, WEI J B. An adaptive dual mode semi-blind channel estimation based on soft information processing for OFDM systems[J]. Acta Electonica Sinica, 2006, 34(10): 1881-1883. (in Chinese)
[16]	张建康, 陈恩庆, 穆晓敏, 等. OFDM 系统中ー种最大似然信道估计算法[J]. 兵工学报, 2009, 30(9): 1206-1210.
	ZHANG J K, CHEN E Q, MU X M, et al. A novel maximum likelihood channel estimation for OFDM systems[J]. Acta Armamentarii, 2009, 30(9): 1206-1210. (in Chinese)
[17]	WU H, LIU Y, WANG K. Analysis of DFT-based channel estimation for uplink massive MIMO systems[J]. IEEE Communications Letters, 2017, 22(2): 328-331.
[18]	SEO J, JANG S, YANG J, et al. Analysis of pilot-aided channel estimation with optimal leakage suppression for OFDM systems[J]. IEEE Communications Letters, 2010, 14(9): 809-811.
[19]	DING X H, AN J P, ZHAO Z, et al. Low-density parity-check coded direct sequence spread spectrum receiver based on analog probabilistic processing[J]. IEEE Transactions on Vehicular Technology, 2021, 70(7): 6355-6370.
[20]	SONG W G, LIM J T. Pilot-symbol aided channel estimation for OFDM with fast fading channels[J]. IEEE Transactions on Broadcasting, 2003, 49(4): 398-402.