Location-Aided Umbrella-shaped Massive MIMO Beamforming Scheme with Transmit Diversity for High Speed Railway Communications

In this paper, we present a practical simple location-aided umbrella-shaped beamforming scheme with transmit diversity of massive Multiple-input Multiple-output (MIMO) system for high speed railway scenarios. Unlike conventional schemes which combines space-time block coding (STBC) with adaptive beamforming or orthogonal switched beamforming, our scheme needs neither uplink channel covariance matrix (UCCM) nor downlink CCM (DCCM) but precalculates the beamforming weights with the help of train location information, which can be completed through pure off-line calculation and therefore reduce system implementation complexity. A closed-form solution of power allocation optimization is derived and the performance of our scheme is verified with simulations from the perspectives of instantaneous received signal-to-noise ratio (SNR), bit error rate (BER) and handover success probability. It indicates that the performance of our scheme approaches to the combination scheme of STBC and adaptive beamforming (STBC-ABF) without introducing any on-line system complexities.