移动通信的基本技术 四、分组移动通信

1.前言以ARPA网*(美国远景研究计划局计算机网)为首的计算机网络取得了惊人的发展,其中占主流的交换方式是分组交换方式。这是由于这类系统一般是由若干分段的信息源组成,故相互间必须有效地共用通信资源。将这种分组通信的概念首先用于无线通信的是夏威夷大学的ALOHA系统。随后出现了多级中继分散型的正式的分组移动通信系统,如ARPA计算机网。无线分组通信系     

Analysis and study of a handoff scheme with multiple priority strategies

A handoff scheme with the combination of channel reservation and preemptive priority in integrated voice/data cellular mobile systems is proposed. In the scheme, calls are divided into three different classes: handoff voice calls, originating voice calls, and data calls. An access strategy with the combination of channel reservation and preemptive priority is provided to a handoff voice call. Furthermore, in order to improve the system capacity for the total voice traffic, preemptive priority is also given to partial originating voice calls. The system is modeled by a two-dimensional Markov chain. Both the iteration method and the approximate method are used to calculate and analyze some of the most important performance measures of the system. It is shown that our scheme can provide better quality of services for mobile subscribers.     

置信传播译码算法的性能测度

本文基于树和有限状态机系统地推导了低密度校验码(LDPC)置信传播译码算法中的消息修正公式,引入了连续消息空间的概率测度,推导了常见二元对称信道输出分布和迭代过程中消息密度进化的计算公式,讨论了算法性能的参数化估计.这种计算分析工具可以用于独立于信道的算法收敛性分析,有助于设计LDPC码,有助于分析LDPC码译码器的量化效应并实现快速译码方案,使其获得在实时通信系统中的应用.