Conventional beamforming methods for intelligent reflecting surfaces (IRSs) or reconfigurable intelligent surfaces (RISs) typically entail the full channel state information (CSI). However, the computational cost of channel acquisition soars exponentially with the number of IRSs. To bypass this difficulty, we propose a novel strategy called blind beamforming that coordinates multiple IRSs by means of statistics without knowing CSI. Blind beamforming only requires measuring the received signal power at the user terminal for a sequence of randomly generated phase shifts across all IRSs. The main idea is to extract the key statistical quantity for beamforming by exploring only a small portion of the whole solution space of phase shifts. We show that blind beamforming guarantees a signal-to-noise ratio (SNR) boost of Theta(N^{2L}) under certain conditions, where L is the number of IRSs and N is the number of reflecting elements per IRS. The above result significantly improves upon the state of the art in the area of multi-IRS assisted communication. Moreover, blind beamforming is justified via field tests and simulations.
翻译:智能反射表面(IRS)或可重新配置的智能表面(RIS)的常规光束成型方法通常需要完整的频道状态信息。然而,频道获取的计算成本随着IRS的数量而成倍上升。为了绕过这一困难,我们提议了一个叫“盲光光束”的新战略,它通过统计数据协调多种IRS。 盲人光束只要求测量用户终端接收的信号能量,以便在所有IRS中随机生成的相位移动的序列。主要想法是通过只探索整个相位移动的解决方案空间的一小部分来提取成形的关键统计数量。此外,我们表明,在一定条件下,盲光束保证了Theta(N ⁇ 2L})的信号-噪音率(SNRR)的提升,L是IRS的数量,N是每个IRS的反射元素的数量。以上是多IRS辅助通信领域艺术状态的显著改善。此外,通过实地测试和模拟,盲人成形是有道理的。