Existing works on IRS have mainly considered IRS being deployed in the environment to dynamically control the wireless channels between the BS and its served users. In contrast, we propose in this paper a new integrated IRS BS architecture by deploying IRSs inside the BS antenna radome. Since the distance between the integrated IRSs and BS antenna array is practically small, the path loss among them is significantly reduced and the real time control of the IRS reflection by the BS becomes easier to implement. However, the resultant near field channel model also becomes drastically different. Thus, we propose an element wise channel model for IRS to characterize the channel vector between each single antenna user and the antenna array of the BS, which includes the direct (without any IRS reflection) as well as the single and double IRS-reflection channel components. Then, we formulate a problem to optimize the reflection coefficients of all IRS reflecting elements for maximizing the uplink sum rate of the users. By considering two typical cases with/without perfect CSI at the BS, the formulated problem is solved efficiently by adopting the successive refinement method and iterative random phase algorithm (IRPA), respectively. Numerical results validate the substantial capacity gain of the integrated IRS BS architecture over the conventional multi antenna BS without integrated IRS. Moreover, the proposed algorithms significantly outperform other benchmark schemes in terms of sum rate, and the IRPA without CSI can approach the performance upper bound with perfect CSI as the training overhead increases.

翻译：摘要：现有关于智能反射面（IRS）的研究主要考虑将其部署在环境中，以动态控制基站（BS）与所服务用户之间的无线信道。与此不同，本文提出了一种新型集成IRS的基站架构，即将IRS部署在基站天线罩内部。由于集成IRS与基站天线阵列之间的距离实际上较小，它们之间的路径损耗显著降低，且基站对IRS反射的实时控制更易于实现。然而，由此产生的近场信道模型也发生了根本性变化。因此，我们提出了一种IRS的逐元素信道模型，以表征每个单天线用户与基站天线阵列之间的信道向量，该模型包括直视分量（不含任何IRS反射）以及单次和双次IRS反射信道分量。随后，我们构建了一个优化问题，以最大化用户上行和速率为目标，优化所有IRS反射单元的反射系数。通过考虑基站具有/不具有完美信道状态信息（CSI）的两种典型情形，所构建的问题分别采用逐步精化方法和迭代随机相位算法（IRPA）进行高效求解。数值结果验证了集成IRS的基站架构相较于未集成IRS的传统多天线基站在容量上的显著优势。此外，所提算法在和速率方面显著优于其他基准方案，且随着训练开销增加，无CSI的IRPA算法能够逼近具有完美CSI的性能上界。