Low Complexity Beam Selection Scheme for High Speed Railway Communications

Abstract

Large-scale multiple input multiple output (MIMO) assisted beamforming based on millimeter waves for high speed railway (HSR) communication systems is employed to increase system capacity and data transmission rate. In order to reduce the number of handovers and improve system throughput, multistream beamforming with different beamwidths is used as the transmit beam at the base station (BS). However, when the train moves toward the cell edge, the inter-beam ambiguity (IBA) becomes larger and the performance of the system will decrease if the number of beams remains unchanged. In order to overcome such difficulty, a low complexity beam selection scheme based on multi-stream beamforming is proposed. With this methodology, in the vicinity of the BS, all beams are activated to serve all mobile relays (MRs) installed at the top of the train. At the cell edge, only one beam is activated due to the unacceptable IBA. Observing from the simulation results, the proposed scheme can achieve low complementation complexity with high throughput performance.