SNR估计误差对BICM-ID系统性能影响的研究

Study of the Performance Sensitivity to SNR Mismatch in BICM-ID System

在BICM-ID(Bit-Interleaved Coded Modulation with Iterative Decoding,BICM-ID)系统或其他级联码系统中实现迭代检测接收机需要对信道的信噪比(SNR)进行估计。该文研究信噪比估计误差对BICM-ID系统性能的影响,分析各种译码算法对信噪比估计误差的敏感程度。理论分析和仿真结果表明max-log-APP算法对信噪比估计具有最好的鲁棒性,log-APP及其他简化算法对SNR估计误差的鲁棒性在SNR过估计时比SNR欠估计时好,原因在于各个算法所采用的修正函数不同。满足算法性能没有大的损失的SNR估计误差精度范围随着信道条件的改善而增大,通常在-2dB到+6dB之间。因此在非理想的信道状态信息条件下,max-log-APP算法是BICM-ID系统的最佳译码算法。

The iterative decoding schemes such as BICM-ID and other concatenated coding systems require the knowledge of channel Signal-to-Noise Ratio （SNR）. The effect of SNR estimation errors is studied for BICMoID in the paper and the performance sensitivity of SNR mismatch for the log-APP decoding algorithm and its simplified implementations is analyzed. Analysis and simulation results show that the max, log-APP algorithm is robust against any SNR mismatch problem,while the log-APP algorithm and other simplified implementations are more tolerant of overestimation of SNR than underestimation, which is because they use different correction functions. The required SNR accuracy to prevent large performance degradation is increased with the increase of channel SNR, generally from -2dB to ＋6dB. Therefore, when there is no perfect channel state information, the max-log-APP algorithm is the optimum decoding algorithm for BICM-ID.