Coordinated multipoint in heterogeneous networks with overlap within microcell expanded regions -

Abstract

The Third Generation Partnership Program’s (3GPP) is developing further enhancements to Long Term Evolution Systems known as LTE Advanced (LTE-A). These modifications are aimed at fulfilling the requirements of a fourth generation (4G) technology mainly in terms of throughput and coverage. An improvement in throughput can be achieved by reducing the distance between the base station (BS) and user equipment (UE). Therefore, heterogeneous networks (HetNets) were introduced as a means to meet increasing traffic demands. A HetNet is a multi-tier cellular network that consists of a macrocell tier overlaid with a microcell tier. Macrocell BSs typically have a higher power than microcell BSs. Furthermore, there is a need to offload traffic from the macrocell to the microcell. This can be achieved by expanding the region of the microcell so more users will be associated with it. This causes significant cross-tier interference. One method to improve coverage is to deploy coordinated multipoint (CoMP) within the microcell expanded region (ER). In CoMP, multiple BSs transmit the UE’s data at the same time, mitigating interference and improving performance. Furthermore, a problem arises when considering microcells that are close to each other. In that case, there may be an overlap within the microcell ERs. Traditionally, CoMP would be performed by the serving microcell and macrocell. Within the overlapping region, however, significant interference would be seen from UEs associated with the nearby microcell. Therefore, it would make sense to have the microcell that shares an overlapping region to participate in CoMP with the macrocell and serving microcell. This approach should maximize gains by reducing interference. Our proposed methodology considers the effect of overlapping microcell ERs and uses tools from stochastic geometry to analyze performance metrics in terms of outage probability. Another important consideration in our analysis is the effect on having non-ideal backhaul on the system. A non-ideal