A signal separation based collision resolution scheme for random access systems

In ALOHA-type random multiple access schemes, colliding data packets are usually discarded, and collisions are resolved through random back-off and retransmissions. However, the paper suggests that retransmission should be practised in a deterministic fashion without random back-off. Thus, diversity of the colliding. data can be created through re-collision; and then collision resolution can be achieved by signal separation. Since a K-fold signal mixing problem needs K branches of diversity to be resolved in principle, only K-1 retransmissions are necessary for resolution of a K-fold collision. That means that no throughput penalty is incurred by the collision resolution procedure. Therefore, the proposed method can achieve much higher capacity than the ALOHA protocol. The paper presents a theoretical analysis of the performance of the proposed method in a noisy environment with ARQ mechanisms, using embedded Markov chain and M/G/1 queue model. The analytical results are justified by numerical simulations.