This paper proposes a novel Medium Access Control (MAC) protocol for enabling multiple simultaneous communications in 802.11 networks where the nodes can use adaptive antenna arrays. The presented scheme is backward compatible with the 802.11 standard and is designed for heterogeneous scenarios, where legacy and non-legacy nodes equipped with different antenna systems can coexist. The access rules are based on a local but accurate Signal-to-Interference Ratio (SIR) estimation and on the adoption of Low Density Parity Check (LDPC) codes, which enable each node to reliably estimate the result of the transmission attempt of all active nodes. The proposed scheme is compared to a previously developed one in noisy and multipath-fading environments.
