Study on Code-Division Multiple Access Scheme for Multimedia Mobile Communications

针对直接序列扩频码分多址(DS-CDMA)系统性能受多址干扰(MAI)限制的问题，研究了如何在多媒体移动通信中实现可靠、高速、大容量的码分多址(DS-CDMA)系统。在各种类型的干扰消除器中，已知连续的MAI消除器具有良好的性能。它生成每个干扰信号的复制品，并从接收信号中减去它。因此，可以通过使再生信号更准确来提高连续MAI消除器的性能。在此基础上，提出了纠错码与多址干扰对消器相结合的方案和自适应阵列天线与多址干扰对消器相结合的方案。通过计算机仿真证实了这些方案的性能改善。在一些仿真中，我们假设在接近系统容量的情况下。针对这些情况，我们实现了适合于并行计算的仿真程序，并提出了两种改进DS-CDMA系统中语音和数据综合传输性能的方案。一种是结合了两个分组检测器的干扰消除器。另一种是避免语音信号质量下降的数据分组功率控制方案。通过计算机仿真验证了性能的提高，并在此基础上提出了一种认证密钥协商方案和一种身份和位置保密的双向认证方案。基于形式化的安全定义，证明了该方案对主动攻击是安全的。

The purpose of this study is to investigate the techniques that achieve reliable, high-speed and high-capacity CDMA systems for multimedia mobile communications.The performance of a DS-CDMA system is limited by multiple access interference (MAI). Among various types of interference cancellers, a successive MAI canceller is known to have good performance. It generates a replica of each interference signal and subtracts it from the received signal. Thus, the performance of a successive MAI canceller can be improved by making the regenerated signals more accurate. Based on this observation, we proposed a scheme that integrates an error correction code and an MAI canceller and a scheme that integrates an adaptive array antenna and an MAI canceller. The performance improvements are confirmed for these schemes by computer simulations. In some simulations, we assume the situation with near the system capacity. For these cases, we have implemented simulation programs suitable for parallel computation.We also proposed two schemes that improve the performance of integrated voice and data transmission in DS-CDMA systems. One is an interference canceller combined with two packet detectors. The other is a power control scheme for data packets that avoids the degradation of the voice signal quality. The performance improvements are confirmed at the cost of slight increase of transmission delay of data packets by computer simulations.Furthermore, we also proposed an authenticated key agreement scheme and a mutual authentication scheme with identity and location privacy. We proved that the schemes are secure against active attacks based on formal security definitions.