Modified semi-orthogonal User Scheduling scheme with optimized user selection parameter

In the original Semi-orthogonal User Scheduling (SUS) scheme, there is a parameter that controls the degree of orthogonality of channel directions between co-scheduled users. However, choosing a good value for the parameter is known to be hard. In this paper, we consider optimizing the parameter in a slightly modified setup, where users are scheduled purely based on their channel directions. With the objective to maximize the system throughput, we demonstrate how to optimize the parameter in the case of perfect feedback (i.e. the base station has the perfect knowledge of users' channel directions) as well as in the case of limited feedback.