LDPC编码辅助的判决反馈信道估计与均衡方法

doi:10.12382/bgxb.2022.1041

摘要/Abstract

摘要：

信道频率选择性衰落较强的环境下,传统正交频分复用非盲信道估计与均衡方法的系统误码性能较差,且需要在信号中增加导频符号的插入,降低系统吞吐量。针对上述问题,提出一种低密度奇偶校验(Low-Density Parity-Check,LDPC)编码辅助的判决反馈信道估计与均衡方法。将LDPC编码增益引入判决反馈回路中,以提升收敛性,在插入极少导频符号的条件下达到渐进非盲信道估计与均衡方法的性能。另外提出一种基于条件最大似然原则的信道估计改进算法,以恒虚警原则检测有效抽头信号以提高信道估计精度,并且能够与判决反馈信道估计与均衡方法相结合,进一步提升算法性能。仿真结果表明,在仿真所选用的信道环境下,LDPC编码辅助的判决反馈信道估计与均衡方法相比传统判决反馈方法具有11~13dB的误码性能提升,具有优秀的系统误码性能和鲁棒性。

关键词: 正交频分复用, 多径信道, 信道估计与均衡, 判决反馈, 条件最大似然估计

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

中图分类号:

TN911

李佳宣, 丁旭辉, 杨凯, 代计博, 卜祥元, 安建平. LDPC编码辅助的判决反馈信道估计与均衡方法[J]. 兵工学报, 2024, 45(4): 1168-1175.

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.

图/表 7

图1 OFDM系统数据帧结构

Fig.1 OFDM frame structure

图2 LDPC编码辅助的判决反馈信道估计与均衡方法处理流程

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

表1 仿真参数

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

图3 COST207RA信道下算法误码性能

Fig.3 BER performance of algorithms in COST207RA channel

图4 COST207TU信道下算法误码性能

Fig.4 BER performance of algorithms in COST207TU channel

图5 COST207RA信道下算法NMSE性能

Fig.5 NMSE performance of algorithms in COST207RA channel

图6 COST207TU信道下算法NMSE性能

Fig.6 NMSE performance of algorithms in COST207TU channel

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