How Backhaul Networks Influence the Feasibility of Coordinated Multipoint in Cellular Networks

Interference is one of the most challenging problems in current cellular mobile access networks. Coordinated nultipoint transmission/reception, and in particular joint processing, has proven to be a beneficial solution for interference management. Most research so far has investigated the requirements and gains on the wireless side but only superficially showed the impact on and requirements for the backhaul network. We take a different approach by looking at different backhaul topologies and technologies, and analyzing how they can support CoMP cooperation schemes. We study, for different traffic scenarios and backhaul connectivity levels, which base station clusters are actually feasible compared to the ones desirable from the radio access network perspective. We found out that a significant mismatch exists between the desired wireless clusters, as defined by the RAN, and feasible ones, as allowed by the given backhaul characteristics. Based on these findings, we explain how RAN clustering and backhaul clustering have to cooperate to come to feasible solutions. As one possible solution, we present a backhaul network preclustering scheme, which is able to predict which BSs are actually eligible for cooperation during the runtime of the network. The gains of this approach are quantifiable in terms of reduced signaling and user data exchange, and reduced MIMO signal processing.