MMSE Based Combining Robust to Beam Pointing Error for Uplink Multi-User SIMO Systems

Considering the situation of which the base station (BS) is placed on the flying platform such as unmanned aerial vehicle (UAV), the jittering of the BS may lead to unstable beam pointing. This paper investigates the minimum mean square error (MMSE) based combining applicable to multi-user single-input-multiple-output (SIMO) multiple-paths transmission system in the presence of the beam pointing error. The mean square error of the estimated signal after combining should be as small as possible within a range of angle-of-arrival (AoA) while minimizing the power of noise after combining. The alternating direction method of multipliers (ADMM) and augmented Lagrange method (ALM) methods are used jointly to solve the formulated optimization problem and get the robust MMSE combining (RMMSEC) algorithm. Simulation results show that the proposed design is more robust than traditional algorithms to the beam pointing error on the bit error ratio (BER) performance.