16QAM-OFDM系统的迭代信道估计

传统的OFDM信道估计器和译码器分开进行,信道估计的可靠性不高.针对16QAM高效调制的OFDM系统,提出了一种基于Turbo译码的迭代信道估计方案.在迭代过程中利用译码器产生的可靠信息来改善信道估计的精度;同时推导了16QAM软去映射、校验比特译码和符号重构算法的数学过程.为了防止由于译码器判决不准造成的误差传播,提出了一种基于门限控制的迭代估计算法.仿真结果表明,该算法可有效改善系统的整体性能.

Iterative channel estimation in 16QAM-OFDM systems

The channel estimation may not be more accurate due to the separation of the channel estimator and decoder in conventional OFDM system.To mitigate this situation,a scheme of iterative channel estimation based on Turbo decoder was presented focusing on OFDM system with efficient 16QAM modulation.During the iterative process,the channel estimation accuracy can be refined by Turbo decoder's soft information.Meanwhile,the algorithms of 16QAM Softdemapping parity bit decoding and symbol mapping were derived.In addition,the iterative estimation algorithm based on threshold controlling was proposed in order to avoid serious error propagation.Computer simulation shows the efficiency of the proposed algorithm.