Selective reject ALOHA/FCFS with implicit reservation

An unslotted approach to developing a highly flexible hybrid random-access/reservation protocol, starting with selective reject (SREJ) ALOHA as the basis, is presented. High random-access channel-sharing efficiency is achieved by exploiting the subpacket feedback naturally embedded in an unslotted SREJ-ALOHA channel to develop an implicit conflict-free first come, first served (FCFS) ordering for locally synchronous retransmission. It is shown that in addition to the contention mode of operation, SREJ-ALOHA/FCFS transparently supports an implicit reservation mode which is expected to be useful for mixed interactive/file transfer traffic scenarios. It is demonstrated analytically that implicit reservation SREJ-ALOHA/FCFS typically achieves maximum throughput in the region of 0.6-0.7 along with excellent delay characteristics, and is thus competitive with more coordinated slotted time-division-multiple-access (TDMA)-based alternatives for the mixed traffic scenario