瑞利衰落多重分集后LDPC的性能分析

Analysis on LDPC Performance in Rayleigh Channel with Diversity

针对瑞利信道条件下多个收发通道分集合并后LDPC的纠错性能问题,提出了一种通用的计算方法。该方法根据合并方式如最大比值合并、等增益合并、选择合并与各分集通道的平均输入信噪比计算合并后信噪比的概率密度函数,用多项式拟合的方法得到LDPC在AWGN信道中的纠错性能公式,对该式按合并信噪比的概率密度积分得到瑞利信道下LDPC的纠错能力表达式。以一种有限几何LDPC码为例计算其编码增益,分析了在最大比值合并条件下分集重数与LDPC编码增益的关系。

A general algorithm is presented to evaluate the performance of LDPC with multi-transmit and multi-receive channels inthe rayleigh channel.In this algorithm, the probability density function （PDF） of the combined signal-noise-ratio （SNR） is achievedwith input parameters such as the average SNR of each channel and the diversity ways （ maximum ratio diversity,equal gain diversity orselection diversity）. The exact error-correcting performance （ECP） curve of LDPC in the AWGN channel is evaluated with thepolynomial fitting method.The error-correcting performance of LDPC in the rayleigh channel can be achieved by integrating the productof the PDF of combined SNR and the ECT in AWGN. As an example, the coding gain of a special LDPC is studied, in which therelationship of the number of diversity channel and gains is analyzed.