C-PRMA: The centralized packet reservation multiple access for local wireless communications

Packet switched technology has been demonstrated attractive for use in cellular radio systems with short propagation delay, not only for data but also for voice. In fact, packet voice can efficiently exploit speech on-off activity to improve bandwidth use over TDMA. Such an approach has been first suggested by Goodman, Valenzuela, Gayliard and Ramaamurthi (1982), where packet reservation multiple access, an adaptation to the cellular environment of the reservation ALOHA protocol, has been introduced. However, R-ALOHA is based on a fixed frame scheme. For this reason, it cannot thoroughly exploit the natural advantages implied by the very short propagation delay encountered in microcellular systems, such as, for instance, the immediate retransmission of packets lost because of the interference noise from adjacent cells. We present the centralized PRMA, a natural enhancement of PRMA, that assigns to the base station a central role in scheduling the transmissions of terminals. As a consequence, packet retransmissions and the different delay constraints that emerge from voice and data integration, can easily be dealt with. We also propose a different reservation channel that avoids the bottleneck effect present in PRMA. Preliminary simulation results show a sensible gain, with respect to PRMA, in the maximum number of voice channels that can be accommodated and indicate the optimality of the approach