A low-latency and energy efficient forward handover scheme for LTE-femtocell networks

Femtocells are small, inexpensive, low power cell sites, which are used to improve indoor capacity and coverage. They are generally consumer deployed and are connected to their own wired broadband backhaul connections. A large number of femtocell deployments in long term evolution (LTE) networks are highly anticipated. One of the main technical challenges of LTE-femtocell networks is the handover between a femtocell and the macrocell due to non availability of direct communication links between femto eNBs and macro eNBs. Due to small femtocell coverage areas, frequent handovers between femtocells and macrocells take place. Therefore, a fast handover scheme using small signaling overhead is required for LTE-femtocell networks to support fast and seamless handovers. The S1-based handover scheme specified in the LTE standards for handover between eNBs, which are not directly connected through X2 interface, can also be used for handover between a femtocell and a macrocell. However, the latency of a S1-based handover increases significantly with the Internet delay as HeNBs are connected to eNBs through public Internet. In this paper, we propose a fast and efficient handover scheme to facilitate handovers between femtocells and macrocells. We also introduce a novel concept of the Temporary Area Partners (TAP) network, which consists of the mobile user equipment connected through device-to-device communication. Due to aforesaid TAP network, the proposed handover scheme will be more robust than the forward and S1-based handover schemes. Our delay performance analysis shows that the proposed scheme has much lower latency than the existing S1-based and forward handover schemes.