Joint Time Allocation and Power Control in Multicell Networks With Load Coupling: Energy Saving and Rate Improvement

In this paper, we consider the problems of minimizing sum power and maximizing sum rate for multicell networks with load coupling, where coupling relation occurs among cells due to intercell interference. This coupling relation is characterized by the signal-to-interference-plus-noise ratio (SINR) coupling model with cell load vector and cell power vector as the variables. Due to the nonlinear SINR coupling model, the optimization problems for multicell networks with load coupling is nonconvex. To solve these nonconvex problems, we first consider the optimization problems for single-cell networks. Through variable transformations, the optimization problems can be equivalently transformed into convex problems. By solving the Karush-Kuhn-Tucker, the optimal solutions to power minimization and rate maximization problems can be obtained in closed form. Based on the theoretical findings of optimization problems for single-cell networks, we develop a distributed time allocation and power control algorithm with low complexity for the sum power minimization in multicell networks. This algorithm is proved to be convergent and globally optimal by using the properties of standard interference function. For sum rate optimization in multicell networks, we also provide a distributed algorithm that yields suboptimal solution. Besides, the convergence for this distributed algorithm is proved. Numerical results illustrate the theoretical findings, showing the superiority of our solutions compared to the conventional solution of allocating uniform power for users in the same cell.