A decomposition method for optimal user assignment in cellular networks with orthogonal transmissions

Effective operation of next-generation communication networks requires the deployment of a high number of base stations (BSs) capable of adapting dynamically their available resources to the changing environment. The resources include link layer variables (user-channel allocation and user-BS assignment) that, due to their binary nature, render the design challenging. This work proposes algorithms for user-BS allocation in cellular networks where users access orthogonally and close-by BSs use non-interfering channels. The user-BS allocation algorithms are designed jointly with the power, rate, and user-channel allocation, and take into account the dynamic environment. Three different algorithms are designed, each of them updates (adapts) the user-BS allocation at a different speed. We show that although the linear relaxation of all the binary variables is not optimal, a Benders´ decomposition approach can be used to find the optimal solution. To accomplish this, we split the original problem so that the user-BS variables are isolated, relax the remaining binary variables, and solve the (sub-)problems iteratively.