An adaptive dual-rate random access scheme

We propose a random access scheme with reduced rate retransmissions. The scheme is based on the standard slotted Aloha protocol; but if a collision happens, the colliding and thus corrupted packets is shrinked in size for retransmissions. The size shrinking can be achieved using the widely available multirate scalable source coding techniques. The channel slot splits into minislots and the shrinked packets are transmitted at one randomly chosen minislot. This dual-rate scheme allows significantly higher packet throughput while keeping a decent bit throughput, which is proved both analytically and numerically in this paper.