说明：  In millimetre wave (mm-wave) communications, hybrid precoding is preferred which uses much less number of RF chains compared with the number of antenna elements. The conventional method selects the beamforming vectors at base station (BS) and the combining vectors at user equipments (UEs) to maximise the received signal power. However, in some specific scenarios, when UEs have strong and highly correlated paths, referred to as collided UEs, they might share the same beamforming vector at the BS leading to severe inter-user interference. An enhanced beam selection algorithm is proposed to eliminate the severe inter-user interference by reselecting the beamforming/ combining vector pairs for the collided UEs. Simulation results demonstrate that the proposed scheme could increase the achievable rates of the collided UEs under sparse mm-wave wireless channels.