On User Scheduling for Fixed Wireless Access via Channel Statistics

Conventional multi-user scheduling in cellular networks are required to make a decision every transmission time interval (TTI) of at most several milliseconds. Only quite simple schemes can be implemented under the stringent time constraint, resulting in far-from-optimum performance. In this paper, we focus on the case of scheduling multiple users in a fixed wireless access (FWA) network with stable channel characteristics. We propose a scheduling approach by which a high-quality scheduling decision based on statistical channel state information (CSI) is made across all TTIs instead of making simple TTI-level decisions. The proposed design is essentially a mixed-integer non-smooth non-convex stochastic problem. We first replace the indicator functions in the formulation by smooth sigmoid functions to tackle nonsmoothness. By leveraging deterministic equivalents (D.E.), we then convert the original stochastic problem into an approximated deterministic one, followed by linear relaxation of the integer constraints. However, the converted problem is still nonconvex due to implicit equation constraints formerly introduced by D.E. Therefore, we employ implicit optimization technique to compute the gradient explicitly, with which we further propose an algorithm design based on a modified version of Frank–Wolfe method. Numerical results verify the effectiveness of our proposed scheme.