Coping with out-of-cluster leakage in downlink coordinated multi-point

In classical cellular systems, the cell edge is a problem for the user performance. Coordinated-multi point transmission (CoMP) is able to deal with this problem, reducing interference at the cell edge. A set of cells cooperates in the so-called cooperation cluster. Practical CoMP systems have to cope with limited cluster sizes. With the cluster size limitation, the former cell edge problems are now re-appearing at the cluster edge. This paper, focusing on the downlink, shows that out-of-cluster leakage can be treated by appropriate simple precoding and receive combining strategies. With those leakage-aware spatial processing techniques, we are using spare degrees of freedom at the transmitter and/or receiver in order suppress out-of-cluster leakage. The precoders of each cluster are modified after the scheduling decisions have been made based on channel knowledge from cluster edge interference victims. Simulation results show that the performance gap at cluster edges can be reduced. We also take into account the presence of imperfect channel knowledge. In this case, the potential of leakage-aware spatial processing is reduced, but being still beneficial over ignoring cluster edge effects.