DCF/USDMA: Enhanced DCF for uplink SDMA transmissions in WLANs

The traditional IEEE 802.11 DCF allows only one node to access the channel each time. In order to take the benefit of multiple simultaneous uplink transmissions when the AP is equipped with multiple antennas, a new MAC protocol called DCF/USDMA is presented in this paper. DCF/USDMA extends the IEEE 802.11 Distributed Coordination Function (DCF) by introducing a second contention round, which is used to accommodate the multiple simultaneous transmissions from multiple stations. Results show that the DCF/USDMA protocol is able to achieve a significant performance gain compared to that of the conventional DCF, the analysis of which also provides some insights about how the different parameters that control the DCF/USDMA operation can be optimized.