Adaptive coding for slotted DS-SSMA packet radio systems

In order to achieve adaptive coding, the type-II hybrid ARQ protocol is applied to a slotted direct-sequence spread-spectrum multiple-access (DS-SSMA) packet radio system with a finite number of users. Two-dimensional Markov chains are employed to model the system dynamics. Based on this model, the performance of the type-II hybrid ARQ protocol is upper and lower bounded by considering, respectively, a superior scheme and an inferior scheme. The steady state throughput and delay performance of the two bounding schemes are obtained. Moreover, the optimal retransmission policy is found for each fixed input load.