Cooperative Double-IRS Aided Communication: Beamforming Design and Power Scaling (2004.01846v1)

Abstract: 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 O(K^4), which greatly outperforms the case of deploying one traditional IRS with a power gain of order 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.

• The paper demonstrates that a cooperative double-IRS system achieves a power gain of order O(K^4), outperforming traditional single-IRS configurations.
• It introduces a joint passive beamforming design that optimizes signal transmission in scenarios with communication blockages.
• Simulations reveal a SNR improvement from approximately 6dB to 10dB when scaling element counts, validating the enhanced performance of the double-IRS approach.

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

The paper discusses an innovative approach in enhancing wireless communication using intelligent reflecting surfaces (IRS). Traditional single IRS deployments are limited, providing a power gain of order $\mathcal{O}(K^2)$, where $K$ is the number of reflecting elements. The authors propose a double-IRS setup, investigating its beamforming design and power scaling capabilities, ultimately offering a promising solution that can outperform traditional configurations. Specifically, their analysis suggests that a double-IRS system can achieve a power gain of order $\mathcal{O}(K^4)$, illustrating a significant performance enhancement.

Summary

The core idea presented involves integrating two cooperative IRSs for wireless communications where direct transmission paths are impeded by blockages. The dual IRS approach leverages a joint passive beamforming strategy, effectively coordinating the reflection between two surfaces to optimize signal transmission. The paper primarily assumes a line-of-sight (LoS) configuration between IRS 1 and IRS 2, facilitating efficient channel modeling and achieving the substantial power increase. The proposed design aligns with the geometric orientation of the reflecting elements to harness the maximum potential of the reflected wavelengths.

Numerical Results and Analysis

The authors provide extensive numerical simulations to substantiate their hypothesis, demonstrating the superior performance of a double-IRS system over a single IRS configuration, underlining conditions such as adequate element count and suitable placement. For practical deployment, they emphasize that at least 840 elements are required to offset the additional path loss due to the double reflection. The simulations reinforce the proposed power gain theory, consistently showing a 10\textsuperscript{dB} improvement in received signal-to-noise ratio (SNR) when doubling the total number of IRS elements, compared to a single IRS scenario which achieves approximately 6\textsuperscript{dB}.

Implications and Future Directions

The implications of such a system extend into real-world scenarios, potentially revolutionizing scenarios plagued with physical barriers impeding direct wireless communication paths. Practical applications could include urban environments with dense building structures or secluded locations requiring robust communication networks. On a theoretical level, the research opens inquiries into multi-antenna systems, broader multi-IRS deployments, and adapting beamforming techniques suitable for channels with varying propagation conditions beyond LoS, such as Rician fading models.

To conclude, this paper presents a compelling argument for dual-IRS systems, offering a viable way to significantly enhance power gain and, consequently, communication efficacy in obstructive scenarios. The future of intelligent reflecting surfaces in telecommunications is bolstered with approaches like these, set to explore beyond mere increase in elements, towards more sophisticated arrangements and beamforming methodologies that could redefine network deployments entirely.