Acknowledgement-aware MPR MAC protocol for distributed WLANs: Design and analysis

Abstract

Multi-packet reception (MPR), in which a receiver can decode multiple simultaneous transmissions, significantly improves the uplink throughput of wireless local area networks (WLANs). However, the medium access control (MAC) layer must be redesigned to encourage, and not avoid, simultaneous transmissions. Asynchronous MPR MAC protocols, in which nodes independently access the channel so long as the number of ongoing transmissions is less than a threshold, are promising solutions for enabling MPR in IEEE 802.11-based WLANs. In this paper, we highlight the problem of acknowledgment (ACK) delays that arises in asynchronous MPR when multiple nodes transmit in succession without the channel becoming idle. We propose a novel asynchronous MAC protocol that reduces the ACK delays, increases throughput, and retains the distributed nature of the 802.11 distributed coordination function (DCF). An accurate renewal theoretic fixed-point analysis that leads to general analytical expressions for the saturation throughput is also developed.