Basic Study towards a Multi-media Microcellular Personal Communication System

面向下一代多媒体个人通信的基础研究已经展开。1.1992-1993年期间的主要研究成果摘要如下。在理论分析和计算机仿真的基础上，阐明了宽带蜂窝系统在多径衰落条件下，使单位小区分组传输吞吐量最大的最佳载频/同频干扰比(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。它试图分配一个可以最有效地应用后续功率控制的信道。通过合理选择功率控制范围，该算法在不牺牲其他性能的前提下，实现了很低的发射功率。开发了一种仿真系统，用于评估在多径衰落信道上传输的高度压缩的静止图像的重建图像质量。一种将更多的奇偶校验比特分配给更重要的信息用于纠错的不等差错保护方案已被应用于类JPEG类静止图像的传输，并被证明在总比特率固定的情况下对提高图像质量非常有效。已经提出了一种利用静止图像本身的冗余的自动重发请求(ARQ)差错控制协议，并且该协议被证明在衰落信道上传输时非常有效地改善图像质量。作为一种适用于大多径时延和同频干扰的移动无线信道的最佳接收机，我们提出了一种扩展的MLSE均衡器，该均衡器通过网格编码调制增强了同频抵消能力，并证实了它的优越性能。

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.