Joint optimization of frequency allocation and user association with differentiated service in hyper-cellular networks

The existing architecture of heterogeneous networks is not energy and spectrum efficient as many lightly loaded base stations (BS) can not be turned off for coverage guarantee. To further improve energy and spectrum efficiency, a new architecture called 'hyper-cellular' network has been proposed in our previous work. Under this architecture, the function of different types of BSs may not be the same, and the mechanism of user association should consider many factors, such as user mobility, traffic load distribution, and differentiated service demands, which are usually ignored in the existing studies. In addition, the spectrum allocation strategy also has great influence on the network performance. As a starting point, we explore the user association mechanism based on the differentiated service demands of the network users, and jointly optimize it with spectrum allocation, in order to maximize the network capacity with quality of service constraints. Although closed-form expression of the optimal solution can not be derived, numerical results are obtained. Our approach is shown to improve the network capacity more than four times over the baseline strategy, where the conventional user association method is adopted and all BSs use all available spectrum.