宏大区制CDMA系统中基于扩频ALOHA的快速随机接入

Spread ALOHA-based fast random access scheme for macro cell CDMA systems

针对码分多址(CDMA)宏大区制下,基于时隙ALOHA的随机接入吞吐量小、接入时延大等问题,提出了一种基于扩频ALOHA多址接入(SAMA)方案。在建模过程中,考虑了多径对冲突区间影响,以及业务信道引起的多址干扰(MAI)等因素,推导了吞吐量及分组平均传输时延的理论公式,并与时隙ALOHA进行了对比分析,给出了仿真和数值结果。结论表明:SAMA有相对较好的随机接入性能,可大大降低分组平均传输时延,在随机接入信道负载较重情况下尤为明显;多径及业务信道对扩频ALOHA接入性能有较大影响。

The slotted ALOHA-based random access scheme has low throughput and long access delays when used in macro cell Code Division Multiple Access （CDMA） systems. A Spread ALOHA- based Multiple Access （SAMA） scheme was developed to improve performance. A system model is presented which includes the impact of multiple paths on the conflict interval, and the Multiple Access Interference （MAI） from the traffic channels. Theoretical formulas are given for the throughput and average access delay of packets. Simulations show that the SAMA has much better access performance and significantly reduces the average access delay, especially when for heavy loads. Multiple paths and numerous traffic channels significantly impact the SAMA access performance.