A contention binary tree algorithm assisted by source separation

Abstract

Inspired by the network diversity multiple access (NDMA) protocols and by the successive interference cancelation tree algorithm (SICTA), we propose a modification to the conventional contention binary tree protocol by incorporating signal separation resources. At each step of the algorithm, the system attempts an optional source separation or a successive interference cancelation using the stored collided packets. The system generalizes all the previously formulated protocols according to either the available system complexity (related to the maximum number of colliding users) or to the system separation capability (related to the structure of the mixing matrix and the probability of successful separation under finite SNR environments). The protocol reduces to a conventional standard tree algorithm (STA) with maximum stable throughput (MST) of 0.346 packets/time-slot for systems with no signal processing capabilities. It also reduces to the SICTA algorithm with an MST of 0.693 for systems with perfect successive interference cancelation. Finally, by adapting the splitting probability according to the source separation capabilities of the system, the algorithm reduces to the NDMA protocol with an MST=1 for a system with perfect separation capabilities and simplified feedback. The tree algorithm is also recognized here as a decentralized networking solution that helps in reducing the system complexity (in terms of maximum number of collided users) and in resolving lost packets from the source separation attempted in previous slots.