极低信噪比下的导频联合编码辅助载波同步算法  

Joint Assisted Carrier Synchronization Algorithm by Pilot and Code at Extremely Low SNR

作　　者：史治平[1] 唐发建[1] 晏辉[1] 龚万春[1] 

机构地区：[1]电子科技大学通信抗干扰国家级重点实验室,成都611731

出　　处：《电子与信息学报》2011年第10期2506-2510,共5页Journal of Electronics & Information Technology

基　　金：国家973计划项目(2007CB310604)资助课题

摘　　要：针对深空通信系统中编码辅助载波同步算法存在精度受限和同步范围小的问题,该文提出两种导频联合编码辅助载波同步算法。首先按照最大似然估计准则推导出编码辅助载波估计的对数似然函数;按麦克劳林级数将其展开并简化或将其导数展开并简化,得到两种具有解析表达式的编码辅助精同步算法。然后为扩大同步范围,设计了一种插入导频的帧结构,提出了基于导频的粗同步算法,推导出它的理论方差。最后将粗同步与精同步顺序地结合起来,同时利用导频来辅助精同步,得到两种大频偏大相偏情况下的载波同步算法,并采用码率为1/12的低码率LDPC-Hadamard码仿真验证。结果表明新算法能大幅提高同步参数的估计精度和范围,在一定的导频长度下可逼近理想同步。Considering that the Code-Aided （CA） carrier recovery algorithms perform small synchronization range and big inaccuracy in extremely low Signal to Noise Ratio （SNR） deep space communication systems, two joint assisted carrier synchronization algorithms by code and pilot are proposed. First the Log-Likelihood-Function （LLF） of CA carrier estimation is derived by Maximum-Likelihood （ML） criterion and two new CA fine synchronization algorithms which have closed-form expression are got by simplify the Maclaurin series of LLF and its derivative. And then, a coarse synchronization algorithm is proposed based on pilot symbols in order to handle larger parameter offsets and its Mean Squared Error （MSE） is also derived. Finally, two joint assisted carrier synchronization algorithms by code and pilot are got by orderly combining the coarse estimation algorithm and fine estimation algorithm. And the simulations by the LDPC-Hadamard code with rate 1/12 verify that the new algorithm can increase synchronization range and improve accuracy, achieving perfect synchronization with a certain amount of pilot symbols at extremely low SNR.

关 键 词：深空通信 载波同步 编码辅助 导频 LDPC—Hadamard码 

分 类 号：TN929.5[电子电信—通信与信息系统]