Queue-aware dynamic on/off switching of small cells in dense heterogeneous networks

In this work we examine downlink discontinuous transmission (DTX) policies for co-channel small cells with mutual interference in a two-tier heterogeneous network. We propose binary on/off switching subject to probabilistic maximum queue-length constraints at the UEs, for two different objective functions: sum-rate maximization and transmit energy minimization. We then show how to transform these non-convex problems with probabilistic constraints into tractable forms via a series of relaxations. Notably, a difference-of-convex functions programming approach is adopted for the constrained sum rate maximization problem. Simulation results show that the proposed DTX schemes can be used to effectively mitigate inter-cell interference as well as energy consumption, while also minimizing the likelihood of user queue-length violations.