Impact of Carrier Configuration and Allocation Scheme on 3G Femtocell Offload Effect

The Macro offload of closed mode 3G Femtocells is studied; i.e. how much of downlink macrocellular traffic can be moved to a Femtocell layer. Taking the 3GPP dense urban reference model as our starting point we show that the combination of adaptive Femtocell power calibration together with a Macro-user frequency allocation method that considers the SINR difference between the mixed and a Macro-only carrier, improves offload. Additionally, the total number of carriers available to the operator is important for the offload potential. It is confirmed that a macro-only carrier is a desirable deployment strategy. At a 25% HNB penetration rate in apartments, 7% of the network traffic can be offloaded in the two-carrier case. This improves to 15% when three carriers are available. With Femto-aware macro-user carrier allocation, the offload performance improves further to 20% with 2 carriers.