A MAC protocol to select optimal transmission mode in very high throughput WLAN: MU-MIMO vs. multiple SU-MIMO

During some cases, especially when the channel quality varies considerably between the receivers, MU-MIMO transmission may fail to utilize the available MIMO capacity to its full potential. A MAC protocol design that can switch between MU-MIMO and multiple SU-MIMO transmissions after taking into account the achievable performance could be one of the simple yet attractive solutions to address such issue. In this paper, by simply upgrading the WLAN default MAC protocol CSMA/CA, we propose a MAC protocol that is capable of performing such switching task in a forthcoming very high throughput WLAN. The detailed performance analysis demonstrates that the more benefits could be achieved from the proposed scheme in comparison to the conventional MU-MIMO transmission only scheme both in terms of throughput and delay.