Maximizing delay-constrained throughput in multi-channel DS-CDMA ALOHA networks through power diversity and successive decoding

We study multi-channel ALOHA networks (e.g., satellite-based networks) for online transaction processing, striving to maximize attainable throughput while meeting a deadline with near certainty. This captures the service provider's fixed costs and per-transaction revenue, the user's delay consciousness and ALOHA's probabilistic nature. Specifically, we consider CDMA channels and successive-decoding receivers. Interestingly, judicious use of power diversity is shown to be extremely effective: with a single transmission, capacity is doubled relative to that with power equalization. With the deadline permitting as few as one or two retransmission attempts upon failure, the probability of not meeting it can be virtually diminished (10^-5 and 10^-8, respectively) while approaching the throughput attainable without delay constraints. This also holds for limited mean transmission power. Thus, the effect of power diversity in conjunction with CDMA depends strongly on the type of receiver and on the exact performance measure, and the proposed approach is worth considering for next-generation systems.