Gradual beamforming and soft handover in high mobility cellular communication networks

A location based gradual beamforming and soft handover scheme for high speed train (HST) equipped with linearly distributed multi-antennas is presented in this paper. The simple and effective gradual beamforming is done based on the priori location information and achieves the array gain, statistical optimal beamforming and tapered beamforming are both analyzed here. The statistical inter-channel interference (ICI) caused by Doppler effect at high speed is taken into account. Along with the movement of HST, the power allocated to the service base station (SBS) is gradually decreased while that to the target base station (TBS) increased, aiming to optimize the outage probability or sum rate. In this way, without explicit connecting and disconnecting to the BSs, soft handover is achieved for the moving HST. Moreover, the beamforming and power allocation parameters are progressively and linearly adjusted by exploiting the linear mobility of HST within a small time interval, making the proposed algorithms very efficient.