LTE Femtocells: System Design and Performance Analysis

In this paper we consider a heterogeneous LTE network where femto cells are randomly deployed in a macro network. Femto cells are modeled as closed cells, namely only group member UEs can be associated with the femto cells. We demonstrate that inter-cell interference may prevent reliable operations for non-member UEs that are in proximity of a closed cell, which thus experience outage. We show how some of the novel features introduced in the Rel-10 specifications of the LTE standard can be leveraged by a suitable inter-cell interference coordination scheme (ICIC), which relies upon resource partitioning among different nodes to reduce the inter-cell interference problem. Additional significant improvements can be achieved when the proposed ICIC scheme is associated to a simple yet effective autonomous power control algorithm, described in detail in the paper, and further gains are demonstrated for UEs employing interference cancellation of broadcast interfering signals. We finally propose an enhanced ICIC method, based on a tighter coordination between macro and femto nodes, whose significant performance improvements advocate for suitable updates to the future LTE specifications.