A Dynamic Clustering Algorithm for Downlink CoMP Systems with Multiple Antenna UEs

Coordinated multi-point (CoMP) schemes have been widely studied in the recent years to limit the inter-cell interference and increase the rates achieved by the user equipments (UEs) at the cell edge. In practice, latency and throughput constraints on the backhaul allow the organization of only small clusters of base stations (BSs) where joint processing (JP) can be implemented. Differently from most of the works that assume single-antenna UEs, in this work we focus on downlink CoMP-JP with multiple antenna UEs and propose a novel dynamic clustering algorithm. The additional degrees of freedom at the UE can be used either to suppress the residual interference by using an interference rejection combiner (IRC) or to allow a multi-stream transmission. In our proposal we first define a set of candidate clusters depending on the long-term channel conditions. Then, in each time slot, we develop a two-step scheme where: a) a weighted sum rate is estimated within each candidate cluster and then b) a set of clusters is scheduled in order to maximize the system weighted sum rate. Numerical results show that much higher rates are achieved when UEs are equipped with multiple antennas. Moreover, as with CoMP part of the interference is managed at the transmitter side, the proposed scheme exploits more the multi-stream transmission than the baseline non-cooperative scheme. Finally, as most of the gain with multiple antenna UEs is due to the IRC, the gain achieved by the proposed approach with respect to the non-cooperative scheme decreases by increasing the number of UE antennas.