A multiaccess protocol assisted by retransmission diversity and multipacket reception

In this paper we propose a new multiaccess protocol that combines the concept of splitting tree algorithms for collision resolution with two of the most relevant cross-layer technologies for random access: retransmission diversity (e.g., NDMA-Network Diversity Multiple Access) and multipacket reception (MPR). The proposed protocol is shown to outperform all the existing algorithms based on either NDMA or MPR. Additionally, the protocol formulation provides an important generalization of the model used for the analysis of solutions in these three fields. Unlike conventional NDMA protocols, in which all the colliding users are requested to immediately retransmit in the next time-slot, our proposed algorithm calculates the optimum set of users allowed to retransmit at each one of the following time-slots. The optimization is based on the previous collected transmissions and on the MPR and source separation (SS) probabilities, thus maximizing throughput and minimizing access-delay. Two possible suboptimal algorithms with simplified feedback assumption and hence suitable for distributed resolution are further derived from the original algorithm: an enhanced version of NDMA assisted by MPR and a fair splitting tree algorithm assisted by MPR and SS. The capacity/stability region of the protocol for several system configurations with two active users is employed to assess the benefits of the proposed algorithms.