C-PRMA: a Centralized Packet Reservation Multiple Access for Local Wireless Communications

Packet switched technology has been demonstrated effective in cellular radio systems with short propagation delay, not only for data but also for voice transmission. In fact, packet voice can efficiently exploit speech on-off activity to improve bandwidth utilization over TDMA. Such an approach has been first suggested in the Packet Reservation Multiple Access (PRMA) technique, an adaptation of the Reservation ALOHA protocol to the cellular environment. However, being PRMA based on a fixed frame scheme, it cannot thoroughly take advantage of the very short propagation delays encountered in microcellular systems, that allow, for instance, the immediate retransmission of packets lost because of the interference noise from adjacent cells. In this paper, we present the Centralized PRMA, a natural enhancement of PRMA, in which the base station plays a central role in scheduling the transmissions of mobile stations. As a consequence, the transmission scheduling is very flexible and can account for the different traffic rate and delay constraints that emerge from voice and data integration. Packet retransmission policy to recover corrupted packets can be implemented and operated efficiently to provide an acceptable grade of service even in a very noisy environment. The simulation results presented in this paper show the quantitative improvements of the C-PRMA performance with respect to PRMA. Keywords—Multiple Access, Local Wireless Communications, Packet Voice.