Optimum arrival-time distribution for delay capture in spread-spectrum packet radio networks

The optimum arrival-time distribution that maximizes the delay-capture probability in spread-spectrum packet radio networks is derived. It is shown that when the optimum arrival-time distribution is employed, the capture probability converges to a finite value as the number of contending packets increases. Normalized throughput and average number of packet retransmissions are computed for slotted ALOHA multipoint-to-point packet radio networks employing direct-sequence spread-spectrum modulation. It is shown that large performance improvement is obtained by optimizing the arrival-time distribution compared to the uniform arrival-time distribution assumed by Davis and Gronemeyer (1980), especially when error-correction coding is employed. Two practical modifications are derived which are shown to provide performance close to the optimum along with an adaptive network load control scheme.