A MAC Protocol with Multi-User MIMO Support for Ad-Hoc WLANs

Multiple Input-Multiple Output (MIMO) is a wide set of multiple antenna technologies, which significantly increase the capacity of wireless networks, without additional bandwidth or increased transmission power. They are widely recognized as methods that can meet the ever growing network capacity requirements. With a MIMO physical layer (PHY), the transmission channel gains a layered structure, which gives another degree of freedom in scheduling transmissions. Additionally, support from higher layers with a cross-layer approach that provides efficient management of the channel's spatial layers, can significantly increase the networks' performance on both link and system level. Single-User-DCF (SU-DCF), a Multiple Access Control (MAC) protocol with the support for Single-User (SU)-MIMO transmissions in Ad-Hoc WLANs, has been previously presented. In this paper we extend that protocol to support Multi-User (MU) transmissions. In the new protocol - Multi-User-DCF (MU-DCF), destination stations for the frames in a MIMO frame can be different stations. We have studied and compared different transmission strategies and schedulers including the IEEE 802.11n system, to explore the benefits of transmitting in MU mode.