Low-complexity downlink coordination scheme for multi-user CoMP in LTE-Advanced system

Coordinated multiple point transmission/reception (CoMP) has been investigated recently as a promising technology to fulfill the requirements of LTE-Advanced. This paper proposes a downlink coordination scheme applied in the CoMP cooperating set to provide best groups of CoMP transmission points and scheduled users for multi-user multi-input multi-output (MU-MIMO) operation with partial channel state information (CSI) and low complexity. First, based on the analysis of composite channel characteristics and feedback overhead, the large-scale channel matrix is proposed for MU-MIMO precoding by using long-term channel statistics. The benefits are easy to acquire and highly reduced feedback overhead. The throughput loss is demonstrated to be acceptable in contrast to using instantaneous CSI via linear precoding. Second, a downlink construction algorithm is developed based on the greedy process, in which a simple channel orthogonality metric is proposed to pre-select the links that are worthwhile for joint processing so as to reduce the scheduling complexity and avoid ill-conditioned channel matrix. About 20% throughput gain is achieved over non-coordination scheme using the same scheduling criterion. The proposed scheme is not limited to any structures of CoMP cooperating set or wireless environments.