Femtocell Access Strategies in Heterogeneous Networks using a Game Theoretical Framework

In recent years, femtocell plays an important role in wireless networks not only for its spectrum reuse but also for its low power consumption. However, there exist several critical issues that need to be investigated, especially for the interferences between the macrocell BSs (mBSs) and femtocell BSs (fBSs). The level of interference mainly depends on the access strategies of fBSs. Two major access policies are considered in femtocell network, including the closed access mode and open access mode. The closed access mode only permits authorized subscribers to utilize the fBS; while all users are allowed to connect to the fBS by adopting the open access mode. Closed access will intuitively be advantageous to the femtocell subscribers, however, interference from the fBS to mBS's users can become severe in the closed access mode than in open access mode. System performance of the entire heterogeneous network (HetNet) can be improved if fBS is operated in the open access mode. In order to relax the inflexible access strategies, hybrid access policy is considered in this paper which allows nonsubscribers to possess limited connections to the fBS. Two cell selection games for distinct scenarios are theoretically modeled to formulate the behaviors of nonsubscribers, and the existences of pure strategy Nash equilibria are also proven under feasible utility functions. From the perspectives of subscribers, HetNet system, and operator, numerical results suggest the adoption of hybrid access mode to provide higher flexibility for the performance enhancement.