Throughput optimization in MU-MIMO systems via exploiting bs antenna tilt

In this paper, we propose a novel framework to enhance the throughput in a single-cell multiuser multiple-input multiple-output (MU-MIMO) system via adaptive base station (BS) antenna tilting. The key idea is to partition the cell into so-called vertical regions and to apply one out of a finite number of tilt and vertical half-power beamwidth (HPBW) pairs at the BS when serving each vertical region. This strategy results in an increased average received signal-to-noise ratio (SNR) over the coverage area. A scheduler is then employed to schedule the transmission to one of the vertical regions at each time-slot with the objective to maximize a suitable utility function of users´ achievable throughput. MU-MIMO zero-forcing beamforming in the horizontal plane is used at the BS to serve the users in each vertical region. Simulation results show that the proposed adaptive BS tilting scheme is a promising approach to provide a noticeable throughput gain compared to a conventional scheme employing a fixed tilt at the BS. The proposed framework also achieves a superior performance-complexity tradeoff compared to a conventional system in which the tilt can be adapted to the location of the served users at each time-slot.