DS/SS CDMA slotted access channel performance analysis

The performance analysis of the slotted access channel for DS/SS CDMA cellular systems with and without multipath combining is presented. Three major factors that affect access channel performance are collision, blocking, and frame erasure rate (FER). All three factors can cause retransmission which results in lower throughput and longer delay. An iterative method is presented to estimate the effective arrival rate in a system without combining. The access rate sequence generated by the iteration is monotone increasing and converges if the system is stable. Using this result, a stability condition is determined in terms of the arrival rate of new messages and the FER. We modify the standard slotted ALOHA analysis so that it applies to a system with combining. The study reveals the trade-off between the messages received per slot and the FER