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）正被广泛研究作为有源中继的潜在低成本、高能效替代方案，用于提升下一代蜂窝网络的覆盖能力。然而，在调度方案设计及其性能评估中，必须考虑IRS配置的技术约束。为此，我们研究了一个IRS辅助的时分多址（TDMA）蜂窝网络，其中IRS的重构会产生通信开销，因此我们致力于限制随时间推移的重构次数。沿着这一思路，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（联合波束赋形与最优IRS配置）。接着，基于距离和容量算法，我们提出不同的聚类技术，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。我们针对不同传播场景、IRS尺寸和移相器量化约束提供了大量数值结果，验证了所提方法在支持具有实际约束的多用户IRS系统中的有效性。