Reducing Signaling Overhead for Femtocell/Macrocell Networks

Femtocell technology has been proposed to offload user data traffic from the macrocell to the femtocell and extend the limited coverage of the macrocell in mobile communications networks. In existing commercial femtocell/macrocell networks, a widely accepted solution to configure the location areas (LAs) is to partition the femtocells overlapped with a macrocell into small groups and to assign each group with a unique LA ID different from that of the macrocell. Such configuration can reduce the paging cost in the mobility management, but increases registration signaling overhead due to discontinuous coverage of femtocells. To reduce signaling overhead in the femtocell/macrocell network, we propose a delay registration (DR) algorithm that postpones the registration until the delay timer expires when the mobile station (MS) moves into the overlapped femtocell. Analytical models and simulation experiments are proposed to investigate the performance of the DR algorithm. Our analytical models are generally enough to accommodate various MS mobility behaviors. Our study can provide guidelines for the operators to set up a delay timer to reduce signaling overhead while sustaining the traffic offloading capability of the femtocell.