Interference aware massive SDMA with a large uniform rectangular antenna array

Time division duplex (TDD) systems where the channel state information (CSI) for downlink transmission is obtained at the base station (BS) are widely considered for large scale antenna systems. Given this situation, information about the inter cell interference (ICI) experienced at the receiver is unknown to the transmitter. We show that under the assumption of a [8,16] rectangular antenna array operating in the regime where the number of antennas N_t and served mobile stations (MSs) N_k is N_t ≈ N_k the system performance in terms of spectral efficiency is degrading compared to N_t ≫ N_k To compensate this effect, we propose a wideband low rate feedback containing information about the interference and provide the proof of concept by system-level simulations. The achieved gains in median sum spectral efficiency (SE) are 150 %. Furthermore, we demonstrate that the per antenna power constraint (PAPC) included in current systems can be changed into a pool power constraint with much lower requirements on power amplifiers compared to today. The gain of 20 to 30 % in sum SE and the impact on the power distribution at the antennas is also shown and obtained by system-level simulations in this work.