Performance of a type-II hybrid ARQ protocol in slotted DS-SSMA packet radio systems

In this paper, the application of a type-II hybrid ARQ protocol in a slotte d direct-sequence spread-spectrum multiple-access (DS-SSMA) packet radio sy stem is investigated. Both the static performance and the dynamic performan ce of such a system are analyzed. In the physical layer, packet error and p acket success probabilities are computed using the improved Gaussian approx imation technique, which accounts for the bit-to-bit error dependence withi n a packet, In the data-link layer, two-dimensional Markov chains are emplo yed to model the system dynamic. Based on this model, the performance of th e type-II hybrid ARQ protocol is upper and lower bounded by considering, re spectively, a superior scheme acid an inferior scheme. Steady stale through put and delay performances of the two bounding schemes are obtained. Moreov er, it is shown that for each fixed input load, there is an optimal retrans mission probability under the finite user population assumption. Bounds on this optimal retransmission probability are also given.