Beamforming and Alamouti STBC combined downlink transmission schemes in communication systems for high-speed railway

In this paper, we propose a reliable downlink (DL) transmission scheme exploiting both location- and speed- related information in a high-speed railway scenario, which relies on a multi-functional antenna array (MFAA) combining space-time block coding (STBC) with adaptive receive beamforming techniques. Firstly, the state-of-the-art STBC and adaptive beamforming techniques are reviewed and analyzed in the context of both block-fading and time-varying channels. Then we propose to employ an antenna array on board of a high-speed train to form two beams for receiving the STBC signals from the DL transmit antennas in order to improve the reliability of the system. It is demonstrated that in the context of combined schemes, receive beamforming is more beneficial than transmit beamforming under high-speed railway linear topology to achieve low bit error rate (BER). Hence it is more attractive to employ receive beamforming antennas on the top of the train.