交织多址接入系统信道容量证明

交织多址接入系统(IDMA)是使用低速率码并利用交织器区分用户的多址接入系统，被认为是码分多址(CDMA)的特例。IDMA省去专门的扩频序列，通过迭代检测提高系统性能，继承了CDMA抗多径衰落和抗多用户干扰等特性，但对于IDMA和CDMA在同样的信道条件下具有相同的信道容量这一基本问题没有给出严格的理论说明。该文在给出交织多址接入系统码定义的基础上，引入了信息论中的平均互信息量作为度量信道容限的标准，研究了K个用户的IDMA系统信道容限问题，得到了与CDMA系统相同的信道容限，并用随机编码和联合典型列的方法对结论进行了证明。由此从信息论的角度证明了IDMA是CDMA的特例，为IDMA的研究工作完成信息论方面的基础证明。

Study on the Channel Capacity for Interleave Division Multiple Access Systems

Interleave division multiple access (IDMA) is a multiple access system with low rate codes and random interleavers, which is the only method to separate different users. Compared with code division multiple access (CDMA) systems, IDMA systems can provide more efficient scheme for multiple user detection (MUD). And IDMA can achieve the optimal combination between coding gain and multipath gain. In research area, IDMA system is looked as a special case of CDMA system and has the same channel capacity with CDMA system. But this issue is not proved from the viewpoint of information theory. Based on the code definition of IDMA, we introduce the average mutual information to measure the channel capacity. The capacity region achieved by IDMA with K users is proved with random encoding and jointly typical sequences. We prove that IDMA has the same capacity limitation with CDMA. Thus, it is proved that IDMA is a special case of CDMA from the view of information theory.