Efficient backward compatible allocation mechanism for multi-user CSMA/CA schemes

With the increase of the number of Wireless Local Area Network devices (laptop PC, PDA, cellphones and set-top boxes) multi-user communication get a great interest for future versions of IEEE 802.11 standard. However, current CSMA/CA WLAN protocols do not support multiple transmissions on the same time frequency resource. This hinders these systems from taking a potential increase of the available throughput in dense deployments. In this contribution we propose a new RTS/CTS mechanism destined for WLAN SDMA/OFDMA access. We provide a capacity based analytical framework to assess the performance of these PHY layer techniques from MAC perspective in a multi-user context. Taking into account the MAC overhead it is shown that SDMA provides a substantial gain for multi-user throughput.