Multi-Point Single-User MIMO Transmission Scheme for Communication Systems beyond LTE-Advanced

Downlink Coordinated Multi-Point (CoMP) transmission schemes are often considered as an effective means to minimize the impact of co-channel interference from neighboring transmission point(s) on the performance of cell-edge users. For Long-Term Evolution Advanced (LTE-A), CoMP was defined in Rel 11 and supports three types of transmission schemes: Coordinated Scheduling and Coordinated Beamforming (CS/CB), Joint Transmission (JT) and Dynamic Point Selection (DPS). For JT CoMP with single-user MIMO (SU-MIMO), it is generally assumed that the user equipment (UE) receives each MIMO layer from multiple transmission points which apply joint precoding. In practice, however, such joint precoding is not always desirable from the performance perspective and system constraints. Therefore, in this paper we propose an alternative approach of supporting JT CoMP for SU-MIMO. More specifically, it is shown that for spatial multiplexing SU-MIMO transmission schemes it is beneficial to transmit MIMO layers with per-point precoding independently from the neighboring (i.e., non-serving) point(s) in addition to the MIMO layer(s) transmitted by the serving point. For the proposed multi-point SU-MIMO transmission scheme, an original proportional fair scheduling algorithm is developed to achieve load balancing across the cooperating transmission points. Using system-level simulations it is demonstrated that the considered multi-point SU-MIMO transmission scheme can improve the system performance and, therefore, may be considered as a candidate enhancement for next generation (5G) cellular communication systems beyond LTE-Advanced.