Constrained joint transmission for downlink CoMP

In this paper, we investigate downlink coordinated multi-point (CoMP) schemes for generic wireless communication systems. We propose a suboptimal joint transmission (JT) algorithm based on the alignment of signal vectors received from coordinating base stations. Signal alignment at the receive end of terminals imposes linear constraints between transmitted signals of cooperating cells. The capacity-achieving problem can then be simplified to beamforming for the anchor cell, for which an iterative approach is developed. It is shown that the convergence of the proposed algorithm is fast, which leads to low-complexity implementations. Numerical results demonstrate that the user throughput can be substantially improved by employing constrained joint transmission in the downlink.