CoMP Joint Transmission for Gaussian Broadcast Channels in Delay-Limited Networks

The backhaul-linked cellular network architecture shows an intrinsic defect in its delay characteristic when coordinated multipoint (CoMP) joint transmission (JT) is operated. Channel state information (CSI) fed back to evolved Node B (eNB) is used to calculate joint beamforming (BF) matrices, and the results are delivered to helping eNBs, which participate in CoMP JT, through the backhaul link. The applied information, however, could be outdated before it reaches the helping eNBs due to the backhaul delay, thus resulting in JT performance degradation as the UE velocity increases. Based on this observation, we propose a novel solution for Gaussian broadcast channels, which efficiently exploits the latest channel information available in the CoMP JT architecture. The numerical results clearly demonstrate the spectral efficiency gain of the proposed scheme at the cell-edge region, particularly with high velocity and large backhaul delay.