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

It is generally accepted that enabling concurrent links via the use of multi antenna techniques is an effective means of improving throughput in a MANET. Several MAC protocols (i.e. MIMA MAC, and SPACEMAC) have even been introduced in the literature specifically to increase the number of concurrent links. Recent work, however, has shown that this is not universally true. Given a MIMO enabled network, there are easily produced topologies where a single link MAC will outperform a concurrent MAC, which motivates the need for a MAC scheme that could choose between single link and concurrent link operation as the dynamics of the system changes. In this paper we present a novel MIMO MAC design that can adaptively switch between a single link scheme and a concurrent link scheme. Our design objective is to improve the link throughput by guaranteeing each link´s throughput to be no less than that achievable via a single link MAC protocol. To demonstrate our design principle, we first present an idealized derivation where all network information is perfectly known at all nodes. Then as a realistic implementation, we further present a practical MAC protocol that uses distributed handshaking and imperfect channel estimation to run the adaptive switching function. Simulation results validate that our design´s link throughput is greater than or equal to a single link MAC´s throughput with 2% - 12% outage probabilities. Moreover, the proposed MAC´s ergodic link throughput is 20%-30% higher than single link MAC and MIMA-MAC´s counterparts.