一种适用于极低信噪比环境的迭代同步方案

卫星通信、深空通信等应用要求接收机在很低信噪比下工作。近年来研究热点基于码辅助同步算法能够利用编码间依赖关系提高参数估计性能，以实现正确解调。本文以码辅助同步算法为基础，综合分析同步各环节参数估计需求，设计较短帧头的帧格式，提出了一种完整的迭代接收机结构。同时精心选择预估计算法，将定时偏差、载波频偏压缩到很窄范围。最后对码辅助算法迭代复杂度高的问题进行了优化。仿真表明，在极低信噪比下，该结构同步性能良好，复杂度低，传输效率高。

An iterative synchronization scheme for very low SNR environment

Satellite communication and deep space communication require the receiver to operate at very low Signal to Noise Ratio(SNR). Code-aided synchronization algorithm which is a hot research area in recent years can improve estimation performance of parameters by using inter-coding dependencies so as to achieve correct demodulation. Based on the existing code-aided synchronization algorithms, the estimation requirements of parameters are analyzed synthetically, and a complete receiver structure with short frame header is designed. A predictive algorithm is carefully selected to compress the timing and carrier offset to a narrow range. The computation complexity of the iterative decoding algorithm is decreased. The simulation results show that the proposed scheme has good synchronization performance, low complexity and high transmission efficiency at very low SNR modes.