Secure Location Tracking of Femtocells in Heterogeneous Cellular Networks

To improve indoor coverage and network capacity, deploying low-power and small-coverage femtocells in the coverage of a macrocell as a two-tier heterogeneous network is regarded as the most promising approach. Since femtocells share the same licensed spectrum with a macrocell, severe cross-tier and intra-tier interference from concurrent transmissions is introduced, which causes performance degradation. Under the dense and massive deployment of femtocells, mitigating interference in dynamic and realtime fashions is challenging, particularly when macro-femto backhaul coordination is infeasible. One possible solution is that before the deployment, operator determines the static channels a femtocell at a particular location can exploit, which is regarded as network planning on femtocells. However, the owner of the femtocell might install or move it anywhere without the operator's awareness and permission for high-quality indoor transmission. Such misuse behaviors destruct the extensive planning and explicitly suggest the existence of femtocell positioning mechanism. This paper explores the recent innovations in user positioning, Observed Time Difference of Arrival and verifiable multilateration, to design a secure femtocell location tracking scheme with the aid of macrocells. Performance evaluations show that considerable performance improvement can be achieved, and thus demonstrate the necessity of applying location tracking on planned femtocells for interference control.