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 IRS-assisted multi-user system in the orthogonal frequency-division multiple access (OFDMA) framework wherein both the set of possible IRS configurations and the number of IRS 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 IRS configuration and time-frequency scheduling is also proposed. Numerical simulations prove the effectiveness of our greedy solution.

翻译：在蜂窝网络中应用智能反射面（IRS）时，必须考虑其（重）配置在通信开销和能效方面的技术限制。本文研究了正交频分多址（OFDMA）框架下IRS辅助多用户系统的下行时频调度问题，其中IRS的可能配置集合及在一个时间帧内的重配置次数均受限。我们将和速率最大化问题形式化为非多项式（NP）完全的广义多背包问题，并提出了联合IRS配置与时频调度的启发式贪婪算法。数值仿真验证了贪婪解的有效性。