Basic Study towards a Multi-media Microcellular Personal Communication System

对下一代多媒体个人通信进行了基础研究。1992-1993年期间的主要研究成果概述如下。通过理论分析和计算机仿真，得到了在多径衰落条件下宽带蜂窝系统中使每个小区的分组传输吞吐量最大的最佳载波干扰比（C/I）和最佳簇大小.提出了一种新的具有发射功率控制的动态信道分配算法。它试图分配一个信道，随后的功率控制可以最有效地应用于该信道。通过合理选择功率控制范围，该算法与传统算法相比，在不牺牲其它性能的前提下，实现了极低的发射功率.本文介绍了一个用于评价高压缩静止图像在多径衰落信道中传输时的重建图像质量的仿真系统。一种不等差错保护方案，即对较重要的信息分配更多的奇偶校验位用于纠错，已被应用于类JPEG静止图像传输中，并且在总比特率固定的情况下，被证明对提高图像质量是非常有效的.提出了一种利用静止图像自身冗余的自动重传请求（ARQ）差错控制协议，该协议在衰落信道上传输时对提高图像质量非常有效.针对移动的无线信道具有较大的多径时延和同频干扰的情况，提出了一种基于网格编码调制的增强同频抵消能力的扩展MLSE均衡器，并验证了其上级性能。

Basic research towards the next generation multi-media personal communications has been performed. Major research results during 1992-1993 are summarized below.1. Based on the theoretical analysis and computer simurations, optimum carrier to co-channel interference ratio (C/I) maximizing the packet transmission throughput per unit cell and also an optimum cluster size have been clarified for a broadband cellular system subjected to multiupath fading.2. A new dynamic channel allocation algorithm with transmitter power control is proposed. It tries to allocate a channel to which subsequent power control can be applied most effectively. By properly selecting the power control range, this alogorithm has been confirmed to realize very low transmitter power, without sacrificing other perfomance compared to conventional algorithms.3. A simulation system to evaluate the reconstructed picture quality of the highly compressed still image when transmitted over a multipath fading channel has been developed. An unequal error protection scheme, which assigns more parity check bits for error correction to the more important infomation, has been applied to the JPEG-like still picture transmission, and shown to be very effective to improve the picture quality when the total bit rate is fixed.4. An automatic repeat request (ARQ) error control protocol which utilizes the redundancy of the still picture itself has been proposed and shown to be very effctive to improve the picture quality when transmitted over a fading channel.5. As an optimum receiver for the mobile radio channel with large multipath delay and co-channel interference, we proposed an extended MLSE equalizer with an enhanced co-channel cancelling capability by trellis coded modulation, and confirmed its superior performance.