Distributed framework of downlink CoMP MU-MIMO transmission with adaptive mode switch and power allocation

The multiuser multiple input multiple output (MU-MIMO) technique has been under active consideration in recent years to increase the capacity of modern wireless system. Mean-while, the coordinated multipoint (CoMP) transmission/reception technique is adopted to mitigate the inter-cell interference (ICI) and enhance the performance of cell edge users. Hence, the CoMP technique can be applied jointly with the MU-MIMO technique (called CoMP MU-MIMO). However, in previous works, only edge users are concerned in precoding design, which causes the severe interference between edge users and center users. In this paper, a novel framework of downlink CoMP MU-MIMO transmission is proposed, which considers the joint optimization for the performance of edge users and center users in a distributed manner. In this framework, to decouple this joint optimization problem, the signal-to-leakage-plus-noise ratio (SLNR) criterion is employed. Then a channel-adaptive CoMP mode switching mechanism is established for the edge user to provide the Quality of Service (QoS). Moreover, to balance the effects of Rayleigh fading on different users, a channel-adaptive power allocation mechanism is also framed. With the total transmission power restrained, this framework can achieve a better tradeoff between edge users and center users than conventional joint transmission (JT) and coordinated beamforming (CB) methods, and result in the higher channel capacity with less inter-cell interactions.