On Open versus Closed LTE-Advanced Femtocells and Dynamic Interference Coordination

Low-power home base stations, also known as femtocells, are one of the strong candidates for high data rate provisioning in indoor environments. Unfortunately, the benefits are not without new challenges in terms of interference management and efficient system operation. In this paper we take a closer look at several aspects associated with the deployment of LTE-Advanced home eNBs under two different access policies: closed subscriber group (CSG) and open subscriber group (OSG). Our results are derived from extensive downlink system level simulations. We limit our scope to dense-urban deployment of femtocells assuming dedicated carriers, i.e. no interference to/from the macro layer. Particularities of each access mode are discussed under different hard frequency re-use configurations. Our results indicate that an OSG deployment is indeed able to cut short the lower end of the SINR distribution when universal frequency re-use is employed. However, when other re-use configurations are considered, OSG no longer guarantees improved SINR conditions. In addition, we present additional results for the autonomous component carrier selection (ACCS) concept introduced in earlier contributions, providing strong suggestions that the scheme yields attractive performance benefits independently of the access policy selected by the operator. Finally, we point out that uplink results including realistic power control settings need to be considered before definitive conclusions can be safely drawn.