Performance Analysis of Co-Channel LTE-Advanced Femto Deployments

User deployed femto cells are a means to cope with increasing traffic demands. From user perspective femto cells provide a good indoor coverage. From provider perspective they are a cheap possibility to offload traffic from the macro layer. In general, a femto cell will not be open for any mobile. Instead the femto cell might only used by a predefined set of mobiles, e.g. mobile devices which belong to the owner of the femto cell. This predefined set of mobiles is called closed-subscriber group (CSG). If a co-channel deployment of macro and femto cells is applied, i.e. macro and femto cells are using the same carrier, the usage of CSGs leads to a problem. Mobiles which are located close to a femto base station but which do not belong to the CSG of the corresponding femto cell are not allowed to perform a handover to the femto cells, although the received signal from the femto eNB is significantly higher than the received signal from the macro. Therefore these mobiles suffer from high femto interference and without additional mechanism they might not get any throughput. To overcome this problem LTE Advanced (LTE-A) introduces so-called enhanced Inter-Cell InterferenceCoordination (eICIC). eICIC is a time-domain ICIC scheme based on subframe blanking. In this paper we address different aspects of the CSG problem in co-channel deployments. Our performance analysis shows, that eICIC can be used to overcome the CSG problem.