MAP译码算法对信道估计偏差敏感度分析

Sensitivity analysis of the channel estimation deviation to the MAP decoding algorithm

作为MAP译码算法的必要参数,信噪比通常通过信道估计单元得到。相关研究表明,信噪比估计值偏差对Turbo译码器输出性能将造成较大的影响。通过对MAP算法的求解,从理论上解释了MAP译码性能下降的主要因素,并通过理论分析和仿真验证,论证了当估计值较真实值小时译码性能明显降低的原因,同时证明了长帧Turbo码对信噪比参数更为敏感。

As a necessary input parameter for MAP decoding algorithm, SNR was normally obtained from the channel estimation unit. Corresponding research indicated that SNR estimation deviation degraded significantly the performance of Turbo decoding. MAP decoding algorithm with SNR estimation deviation was investigated in details, and the degradation mechanism of Turbo decoding was explained analytically. The theoretical analysis and computer simulation have disclosed the specific reasons for the performance degradation when SNR estimation is less than the actual value, and for the higher sensitivity of SNR estimation to long frame Turbo codes.