DYNAMIC CONTROL OF TIME-SLOT ASSIGNMENT IN MULTIACCESS RESERVATION PROTOCOLS

The authors consider the dynamic control of time slot assignment in re servation protocols for multiaccess channels employing frame structure s similar to those investigated by Roberts and others. Such protocols are particularly suitable for channels with long propagation delays, s uch as satellite channels. Fixed length frames are dynamically divided on a frame by frame basis into reservation subframes with minislots f or reservation requests transmitted by slotted Aloha random access, an d data subframes with reserved time slots for data packet transmission s. Formulating the problem as a Markov decision process, the authors d erive the optimal time slot assignment policy, which makes use of comp lete state information of the finite user population, and obtain the d elay-throughput performance. Results show that the optimal policy prov ides substantial performance improvements over fixed assignment polici es. Furthermore, a heuristic dynamic assignment policy called the MF p olicy is proposed that is much easier to derive and implement, particu larly for large networks, while maintaining performance very close to the optimal. Both of these dynamic policies depend on system state inf ormation, which the authors propose to estimate using a generalised ps eudo-Bayesian estimator. The use of this estimator results in only a s mall reduction in performance.