Achieving coordination in random access networks without explicit message passing

We propose a class of medium access control (MAC) protocols that utilize users' own transmission decisions and feedback information from the past slots. We consider an idealized slotted Aloha system and formulate the problem of a protocol designer who cares about the total throughput, the short-term fairness, and the complexity of protocols. A solution to the protocol designer's problem is provided with two users, and an approximate solution with three or more users. We use numerical methods to obtain optimal protocols that solve the protocol designer's problem, compare the total throughput of optimal protocols with that of other protocols proposed in the literature, and analyze a trade-off between throughput and fairness. The results show that by utilizing information obtained in the previous slot, users can achieve some degree of coordination without explicit message passing, which leads to high total throughput.