Joint User Association and Resource Allocation in Heterogeneous Cellular Networks: Comparison of Two Modeling Approaches The performance of different combinations of user association (UA) and resource allocation (RA) in heterogeneous cellular networks has been extensively studied using a classic modeling approach based on system snapshots. There have been also many studies focusing on the dynamics of the system using queueing models. These modeling approaches are rarely compared with each other though they each bring different insights to the design problem. In this paper, we consider a queueing modelbased approach to study the interplay of UA and RA, and compare the results to those obtained using snapshot models. Specifically, we formulate three different joint UA and RA optimization problems corresponding to the following three performance metrics: the maximum achievable arrival rate, the average system delay, and the maximum peruser delay. These problems are nonconvex integer programs. We have therefore developed numerical techniques to compute either their exact solutions or tight lower bounds. We obtain results for different combinations of RA and UA schemes, and compare the trends with those obtained via the snapshot approach. The trends on RA are very similar, which we take as a crossvalidation of the two modeling approaches for this kind of problem. The trends on user association are somewhat different which indicates a lack of robustness of the results and the need for a careful validation of UA models.

Queuebased model approximation for intercell coordination with service differentiation This paper presents a queuing model to evaluate the performances of cooperation mechanisms in 4G5G cellular networks. The main contribution is the proposal of an approximation model with a closed form formula allowing fast numerical evaluation of throughput and loss probabilities per service class, while considering traffic load, radio conditions and the available resources in each collaborating cell. The proposed queuing model is successfully applied to the enhanced InterCell Interference Coordination mechanism with service differentiation in the context of Heterogeneous Cloud based Radio Access Networks. Numerical results are compared to Matlab simulations with realistic radio conditions and user distributions. Through it, decisions on resource allocation among the cooperating cells to achieve the optimal capacity of the system become faster and adaptive. In conclusion, the proposed queuebased model can be used in order to tune the fronthaul links and the core network resources.