基于iMPA的伪码快速捕获算法的性能分析和改进

摘要

针对迭代消息传递算法(iterative Message Passing Algorithm,iMPA),通过证明m序列是一种特殊的线性分组码,给出了该算法应用到伪码捕获的理论依据;分析了采用iMPA进行伪码快速捕获的性能,包括捕获概率和算法复杂度;用马尔科夫链分析了基于iMPA的捕获及判决流程,给出了平均捕获时间的解析表示.针对iMPA进行伪码捕获时收敛速度慢,检测性能较低的缺点,通过增加因子图的约束,提出了冗余iMPA算法,即R-iMPA(redun-daney iMPA).仿真结果表明,R-iMPA能有效的提高算法的收敛速度,检测性能平均提高约2dB.%The theoretic basis of rapid PN code acquisition based on iMPA (iterative message passing algorithm) was give by proving that m sequence is one kind of especial linear block code; and then the performance of acquisition based on iMPA was an-alyzed, which include the computational complexity and acquisition probability; and then, the Markov chain was used to analysis the process of the acquisition and the judgment, and the analytic expression of it was give. At the same time, in order to improve the convergence and the detection probability of acquisition based on iMPA, a new redundancy-iMPA (R-iMPA)was introduced which adds additional restriction to the factor graph. The simulation result showed that the redundancy- iMPA can speed up the convergence effectively and improve the detection performance about 2dB averagely.