Performance analysis of CSMA/CA adapted MIMO aware MAC for multi-user transmission in WLANs

Compared to the traditional SISO system, one of the major benefits of MIMO is to increase spectral efficiency employing spatial multiplexing. However, such an independently increased PHY layer capacity cannot be translated easily to MAC layer capacity gain unless special measures are taken in MAC protocols. For distributed WLANs with MIMO, subtle modifications in dominant MAC protocol CSMA/CA can give rise to a simple, yet practicable, MIMO aware MAC. When employing such MAC for single user spatial multiplexing, throughput is increased linearly with the antenna elements in use; leaving the delay constant. However, for multi-user multiplexing, requirement of more and extended control packets exchange leads higher overhead which ultimately decreases the performance compared to single user multiplexing. But nevertheless, during various network scenarios mutli-user multiplexing, multi-user transmission, is more preferable for its capability to transmit multiple streams of data destined to multiple receivers at one transmission opportunity. In this paper, based on the analytical modeling and derived expressions, we present the performance analysis of CSMA/CA adapted multi-user transmission supporting MIMO aware MAC in terms of average throughput and delay.