An optimal single/concurrent link MAC scheme for a single-hop MIMO network

Abstract

Concurrent link communications built on multi-antenna systems have been widely adopted for spatial resource exploitation. MIMA-MAC, a classical MIMO MAC protocol utilizing concurrent link scheme, is able to provide superior link throughput over conventional single link MAC (under certain isolated link topologies). However, when utilizing rich link adaptation functions in MIMO systems, there exists a non-ignorable probability that MIMA-MAC's throughput will be lower than that of single link scheme (such probability is dominated by the statistics of instantaneous link topology and channel response).Inspired by this critical observation, and for adapting to various link topologies, this paper will present a novel MAC design that can adaptively switch between single or concurrent link scheme. With the aim of absolutely outperforming the single link MAC, here our optimization criterion is to guarantee a throughput result that is either better than or at least equal to single link MAC's counterpart. To highlight the design rationale, we first present an idealized implementation having network information perfectly known in a non-causal way. Then for realistic applications, we further develop a practical MAC implementation dealing with realistic system impairments (distributed handshaking and imperfect channel estimation). Simulation results validate that link throughput in our MAC is higher than or equal to single link MAC's counterpart with minimized outage probabilities. And for ergodic link throughput, our proposed MAC can outperform the single link MAC and MIMA-MAC by around 20%-30%.

A MAC protocol based on dynamic time adjusting in wireless MIMO networks

“…When taking into account rich link adaptation capabilities in MIMO systems, MIMA-MAC's link throughput may be lower than that of single link MAC. So Zhao [8] presents a design that can adaptively switch between single link scheme and concurrent link scheme to improve the link throughput by simultaneously guaranteeing each link's throughput to be no less than its single link scheme's counterpart. The principle of the MAC protocol with Parallel RTS Processing (PRP-MAC) [9] is that the receiver receives up to two continuous RTS packets, then determines the maximum allowable number of data streams and responds with different CTS packets.…”