Media Access Control with Spatial Correlation for MIMO Ad Hoc Networks

MIMO (multiple input multiple output) is capable of offering several-fold increase in spectral efficiency over single-antenna systems through spatial processing. However, current IEEE 802.11 legacy MAC is designed without taking into consideration the interference cancellation capability of MIMO, thereby resulting in suboptimal use of bandwidth spectrum. In this paper, to fully exploit the spatial dimension of freedom offered by MIMO, we propose a methodology that takes into account the spatial correlation between the signal and interference in the design of MIMO ad hoc networks. Through analysis of the effect of spatial correlations on the system throughput, we conclude that it is a crucial factor that cannot be ignored when optimizing the transmission of the networks. Against this backdrop, we propose and investigate a specific MAC protocol for the transmission in a MIMO ad hoc network which 1) allows links to contend for the channel sequentially and transmit data packets simultaneously, yielding more than 35% throughput improvement compared to the system wherein only one link transmits at a time; 2) closely follows the 802.11 DCF (distributed coordination function), allowing simpler implementation as compared to previously proposed MAC protocols.