Scheduling for Downlink OFDMA With IRS Reconfiguration Constraints

The technical limitations of the intelligent reflecting surface (IRS) (re)configurations in terms of both communication overhead and energy efficiency must be considered when IRSs are used in cellular networks. In this paper, we investigate the downlink time-frequency scheduling of an IRSs-assisted multi-user system in the IRSs framework wherein both the set of possible IRSs configurations and the number of IRSs reconfigurations within a time frame are limited. We formulate the sum rate maximization problem as a non-polynomial (NP)-complete generalized multi-knapsack problem. A heuristic greedy algorithm for the joint IRSs configuration and time-frequency scheduling is also proposed. Numerical simulations prove the effectiveness of our greedy solution.