On an Uplink Space Division Multiple Access Technique Based on the Doppler Effect

In this letter, an uplink space division multiple access scheme based on the Doppler effect is proposed for wireless multi-user communication systems. By rotating the receive antenna array or using a circular sampling method, different Doppler frequency shifts are introduced to the received signals from different directions, and then different user's signal can be separated in frequency domain. To maximize the inter-user interference (IUI)-free bandwidth, a max-min criterion is proposed for antenna switching control. The main advantage of the proposed scheme over the conventional space division multiple access (SDMA) schemes is that it needs less number of analog receive chain. Then simulations are carried out to evaluate the performance of the proposed scheme in terms of channel capacity. Simulation results show that the proposed scheme achieves a significant capacity gain, and its capacity is very close to that of a single user system without IUI.