Intelligent reflecting surfaces (IRSs) are being widely investigated as a potential low-cost and energy-efficient alternative to active relays for improving coverage in next-generation cellular networks. However, technical constraints in the configuration of IRSs should be taken into account in the design of scheduling solutions and the assessment of their performance. To this end, we examine an IRS-assisted time division multiple access (TDMA) cellular network where the reconfiguration of the IRS incurs a communication cost; thus, we aim at limiting the number of reconfigurations over time. Along these lines, we propose a clustering-based heuristic scheduling scheme that maximizes the cell sum capacity, subject to a fixed number of reconfigurations within a TDMA frame. First, the best configuration of each user equipment (UE), in terms of joint beamforming and optimal IRS configuration, is determined using an iterative algorithm. Then, we propose different clustering techniques to divide the UEs into subsets sharing the same sub-optimal IRS configuration, derived through distance- and capacity-based algorithms. Finally, UEs within the same cluster are scheduled accordingly. We provide extensive numerical results for different propagation scenarios, IRS sizes, and phase shifters quantization constraints, showing the effectiveness of our approach in supporting multi-user IRS systems with practical constraints.

翻译：智能反射面（IRS）正被广泛研究，作为下一代蜂窝网络中提升覆盖范围的低成本、高能效有源中继替代方案。然而，在调度方案的设计及其性能评估中，需考虑IRS配置的技术约束。为此，我们研究了一种IRS辅助的时分多址（TDMA）蜂窝网络，其中IRS的重构会带来通信开销；因此，我们旨在限制随时间推移的重构次数。基于此，我们提出一种基于聚类的启发式调度方案，在TDMA帧内固定重构次数约束下最大化小区总容量。首先，通过迭代算法确定每个用户设备（UE）的最优配置（联合波束赋形与IRS最佳配置）；其次，提出不同的聚类技术，基于距离与容量算法将UE划分为共享相同次优IRS配置的子集；最后，对同一聚类内的UE进行相应调度。针对不同传播场景、IRS尺寸及移相器量化约束，我们提供了大量数值结果，证明了该方法在支持具有实际约束的多用户IRS系统中的有效性。