研究方向介绍：可重构智能超表面（RIS）是一种新型人工电磁结构，能够以极低能耗对入射电磁波进行动态调控，实现对无线信道的“智能重构”。该技术通过在传播环境中部署具备相位、振幅控制能力的单元阵列，实现波束赋形、信道增强、干扰抑制等功能，为6G通信系统提供高能效、低复杂度的传输解决方案，近年来成为物理层通信的研究热点。

本人研究内容：长期聚焦于RIS系统在多用户、多小区、硬件受限等复杂场景下的建模与优化问题。提出了非对角结构的RIS波束赋形方法，并首次系统性分析了硬件失配和相移噪声对RIS系统性能的影响，相关成果发表在IEEE TCOM、IEEE TVT等期刊。还参与了多项关于RIS设计的美国发明专利，并在RIS辅助系统的信道估计与调制联合设计方面开展了系列工作。

图1：基于可重构智能超表面的无线通信系统

期刊论文：

[1]  Qingchao Li, Mohammed El-Hajjar, Yanshi Sun, Ibrahim Hemadeh, Arman Shojaeifard, Yuanwei Liu, Lajos Hanzo, “Achievable Rate Analysis of the STAR-RIS Aided NOMA Uplink in the Face of Imperfect CSI and Hardware Impairments” [J]. IEEE Transactions on Communications, 2023, 71(10): 6100-6114.

[2]  Qingchao Li, Mohammed El-Hajjar, Lajos Hanzo, “Ergodic Spectral Efficiency Analysis of Intelligent Omni-Surface Aided Systems Suffering From Imperfect CSI and Hardware Impairments” [J]. IEEE Transactions on Communications, 2024, 72(8): 5073-5086.

[3]  Qingchao Li, Mohammed El-Hajjar, Ibrahim Hemadeh, Arman Shojaeifard, Alain A. M. Mourad, Bruno Clerckx, Lajos Hanzo. “Reconfigurable Intelligent Surfaces Relying on Non-Diagonal Phase Shift Matrices” [J]. IEEE Transactions on Vehicular Technology, 2022, 71(6): 6367-6383.

[4]  Qingchao Li, Mohammed El-Hajjar, Ibrahim Hemadeh, Deepa Jagyasi, Arman Shojaeifard, Lajos Hanzo, “Performance Analysis of Active RIS-aided Systems in the Face of Imperfect CSI and Phase Shift Noise” [J]. IEEE Transactions on Vehicular Technology, 2023, 72(6): 8140-8145.

[5]   Qingchao Li, Mohammed El-Hajjar, Ibrahim Hemadeh, Arman Shojaeifard, Alain A. M. Mourad, Lajos Hanzo, “Reconfigurable Intelligent Surface Aided Amplitude- and Phase-Modulated Downlink Transmission” [J]. IEEE Transactions on Vehicular Technology, 2023, 72(6): 8146-8151.

[6]   Qingchao Li, Mohammed El-Hajjar, Ibrahim Hemadeh, Arman Shojaeifard, Lajos Hanzo, “Low-Overhead Channel Estimation for RIS-Aided Multi-Cell Networks in the Presence of Phase Quantization Errors” [J]. IEEE Transactions on Vehicular Technology, 2024, 73(5): 6626-6641.

[7]   Qingchao Li, Mohammed El-Hajjar, Yanshi Sun, Ibrahim Hemadeh, Arman Shojaeifard, Lajos Hanzo, “Achievable Rate Analysis for Intelligent Omni-Surfaces Assisted NOMA Holographic MIMO Systems” [J]. IEEE Transactions on Vehicular Technology, 2024, 73(5): 7400 -7405.

[8]   Qingchao Li, Mohammed El-Hajjar, Ibrahim Hemadeh, Arman Shojaeifard, Lajos Hanzo, “Coordinated Reconfigurable Intelligent Surfaces: Non-Diagonal Group-Connected Design” [J]. IEEE Transactions on Vehicular Technology, 2024, 73(7): 10811-10816.

[9]   Qingchao Li, Mohammed El-Hajjar, Ibrahim Hemadeh, Deepa Jagyasi, Arman Shojaeifard, Ertugrul Basar, and Lajos Hanzo, “The Reconfigurable Intelligent Surface-Aided Multi-Node IoT Downlink: Beamforming Design and Performance Analysis” [J], IEEE Internet of Things Journal, 2023, 10(7): 6400-6414.

[10]   Yinuo Dong, Qingchao Li, Soon Xin Ng, Mohammed El-Hajjar, “Reconfigurable Intelligent Surface Relying on Low-complexity Joint Sector Non-diagonal Structure” [J]. IEEE Open Journal of Vehicular Technology, 2024, 5: 1106-1123.