Coordinated scheduling in MIMO heterogeneous wireless networks using submodular optimization

Multiple transmission point (TP) coordination is an effective tool for managing interference in heterogeneous networks. Using network-level MIMO coordination among TPs, multiple TPs can transmit independent data streams to a single user. We formulate our scheduling problem as a utility optimization problem over the set of user-TP pairs in each subframe, in which each user can be served by multiple TPs. We first prove that this optimization problem is NP-hard. Then, we propose a new scheme based on the difference-of-submodular-function optimization approach. We evaluate our scheme using detailed simulation and demonstrate that it performs on par with a more computationally demanding successive convex approximation optimization scheme. Moreover, the proposed scheme performs within a reasonable percentage of the optimal solution (Table IV). We also study its performance with varying network topology and parameters.