Optimal quantization of BI-AWGN channel for turbo decoding
Zhenqu Zhao, Qijin Zhang, Qiuping Huang, Hongwen Yang · China-Ireland International Conference on Information and Communications Technologies (CIICT 2008) · 2008
In this paper, we investigate the optimal quantizer design for turbo decoding with binary input additive white Gaussian noise (BI-AWGN) channel. The optimal design under MMSE (minimum mean square error) and MMI (maximum mutual information) criteria is derived and the results are compared with the simulation searched quantizers that have best frame error rate performance. Our results show that the MMI quantizer outperforms the MMSE one if the quantizer is used for turbo decoding. The performance of MMI quantizers is very close to the simulation searched quantizers (within 0.05 dB) while the loss of MMSE quantizers is evident. To simplify the design, we also proposed a simple formula to approximate the MMI quantizer. The performance of this approximate quantizer is within 0.03 dB from MMI quantizer. Moreover, we suggest that the quantization interval should be a slightly larger than the designed optimal value if the implementation error is a concern.