Downlink SDMA for legacy IEEE 802.11a/g mobile stations: acknowledgement recovery and channel estimation

We address the problem of downlink throughput improvement for IEEE 802.11a/g systems by using a modified access point (AP) equipped with multiple antennas. The main restriction is that standard terminals should not be modified in any way. An alternating time-offset space division multiple access (SDMA) solution is proposed to overcome restrictions imposed by the legacy terminals requirement. Simulations based on the IEEE 802.11 channel models demonstrate that a near doubling of downlink capacity can be achieved in a conference room environment.