Multi-Round Contention in Wireless LANs with Multipacket Reception

TL;DR

This paper introduces a multi-round contention protocol for MPR WLANs that optimizes channel utilization by using a threshold-based stopping rule, improving throughput especially at low to medium MPR capabilities.

Contribution

It proposes a novel multi-round contention scheme with an optimal stopping rule, enhancing channel utilization over traditional single-round methods in MPR WLANs.

Findings

Multi-round contention improves channel utilization at low to medium MPR levels.

Optimal stopping rule is a simple threshold-based strategy.

Scheme adapts to high MPR, reverting to single-round contention for efficiency.

Abstract

Multi-packet reception (MPR) has been recognized as a powerful capacity-enhancement technique for random-access wireless local area networks (WLANs). As is common with all random access protocols, the wireless channel is often under-utilized in MPR WLANs. In this paper, we propose a novel multi-round contention random-access protocol to address this problem. This work complements the existing random-access methods that are based on single-round contention. In the proposed scheme, stations are given multiple chances to contend for the channel until there are a sufficient number of ``winning" stations that can share the MPR channel for data packet transmission. The key issue here is the identification of the optimal time to stop the contention process and start data transmission. The solution corresponds to finding a desired tradeoff between channel utilization and contention overhead. In this paper, we conduct a rigorous analysis to characterize the optimal strategy using the theory of optimal stopping. An interesting result is that the optimal stopping strategy is a simple threshold-based rule, which stops the contention process as soon as the total number of winning stations exceeds a certain threshold. Compared with the conventional single-round contention protocol, the multi-round contention scheme significantly enhances channel utilization when the MPR capability of the channel is small to medium. Meanwhile, the scheme automatically falls back to single-round contention when the MPR capability is very large, in which case the throughput penalty due to random access is already small even with single-round contention.