Zero-Forcing Beamforming for Non-Collaborative Space Division Multiple Access

In this paper we explore non-collaborative beamforming techniques for space division multiple access (SDMA) scenarios where the base station (BS) and subscriber stations (SS) are equipped with multiple antennas. In non-collaborative SDMA, the SS array weights are designed independent of the BS and of one another. We consider zero-forcing beamforming schemes where the BS ensures that the signal stream to one user does not interfere with others. We derive an expression for average SNR achieved per user in the system and show that the average receive SNR per user degraded linearly with increasing number of users in the system. Further, we show that the dominant right singular vector of the channel matrix is the optimal choice of SS beamforming vector. Simulation results are included to verify our theoretical results