Cooperative Double-IRS Aided Communication: Beamforming Design and Power Scaling

Intelligent reflecting surface (iRS) Is a promising technology to support high performance wireless communication. By adaptively configuring the reflection amplitude and/or phase of each passive reflecting element on It, the IRS can reshape the electromagnetic environment In favour of signal transmission. This letter advances the existing research by proposing and analyzing a double-iRS aided wireless communication system. Under the reasonable assumption that the reflection channel from IRS 1 to IRS 2 Is of rank 1 (e.g., line-of-sight channel), we propose a joint passive beamforming design for the two IRSs. Based on this, we show that deploying two cooperative IRSs with In total {K} elements can yield a power gain of order \mathcal {O}(K^{4}) , which greatly outperforms the case of deploying one traditional IRS with a power gain of order \mathcal {O}(K^{2}). Our simulation results validate that the performance of deploying two cooperative IRSs Is significantly better than that of deploying one IRS given a sufficient total number of IRS elements. We also extend our line-of-sight channel model to show how different channel models affect the performance of the double-iRS aided wireless communication system.