Coordinated multipoint in dense heterogeneous networks with overlapping microcell expanded regions and its effect on backhaul links

One of the goals of Heterogeneous Networks (HetNets) is to offload traffic from the macrocell BS to the microcell base stations (BSs). It has been proposed that in order for the microcell to acquire more users and offload increasing amounts of traffic, its region of coverage must be expanded. This however causes significant cross-tier interference, which can be remedied by utilizing coordinated multipoint (CoMP) within the microcell expanded region (ER). Our methodology considers the effect of overlapping ERs, and proposes the cooperation of concerned microcell BSs with the macrocell BS to further reduce the outage probability and improve throughput. Another important consideration in our analysis is the effect of having non-ideal backhaul on the system's performance. That is, CoMP increases the strain on the backhaul network, since additional data that is proportional to the number of cooperating BSs needs to travel on the backhaul links. Furthermore, the delay should be minimal and less than one subframe duration in order for reported channel state information to remain valid. With this in mind, our proposed system considers the effect of having non-ideal backhaul in a cellular network with CoMP, while taking into account overlaps in the microcell ERs.