一种动态利用码资源的CDMA系统性能研究

Performance Evaluation for Dynanic Code Allocation CDMA System

提出了一种基于随即预约ＡＬＯＨＡ 访问方式，能支持话音和数据业务的动态使用码资源的码分多址访问协议，在该协议中，话音终端采用预约请求排队访问方式。数据终端采用时隙ＡＬＯＨＡ 方式传输数据分组。理论分析和计算机仿真结果表明，该协议能有效地提高系统码资源的利用率。在系统处于重负载情况下该协议能优先保证话音业务服务质量，而处于轻负载下系统码资源能为数据业务充分使用。

A new dynamic code allocation CDMA(DCDMA) protocol, which can support voice and data services simultaneously, is investigated in this paper. In DCDMA protocol, a voice terminal will reserve a spreading code only in talkspurt. The base station assigns a code after successfully receiving a request packet through a special request channel at the beginning of each talksqurt. Unlike a voice terminal, a data terminal must contend a spreading code for each packet transmission. So the code utilization can be significantly improved in DCDMA system. An analytical model and computer simulation is performed for evaluating the performance of the DCDMA protocol. The results show that the DCDMA protocol is very effective in utilizing code resource, and the QOS requirement on voice calls is still satisfactory while the number of data terminal is increased.