Dual-band femtocell traffic balancing over licensed and unlicensed bands

Many cellular user equipments (UEs) today are able to access both the unlicensed band (e.g., via WiFi) and the cellular licensed band. However, in most regions of the world, they are not allowed to access both bands simultaneously for data communications - users can only choose either WiFi or cellular. In order to allow UEs to enjoy both bands at the same time, in our earlier work a framework for femtocells to simultaneously access both licensed and unlicensed bands was proposed. In this paper, the framework is extended to include strategies for femtocells to balance their traffic in licensed and unlicensed bands. The goal is to maximize the sum utility (i.e., user satisfaction) of femto and WiFi users while keeping the femto-to-macro interference below predefined thresholds. The optimal femto traffic balancing scheme is obtained and implemented in a network simulator which considers the activities and interactions of macro, femto and WiFi networks. Simulation results demonstrate that the proposed scheme significantly increases sum utility of all macro, femto and WiFi users, compared with the current practices where users can choose only one band (licensed or unlicensed).