1. 可重构智能超表面（Reconfigurable Intelligent Surfaces）

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。

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.

2. 全息MIMO（Holographic MIMO）

研究方向介绍：全息MIMO（Holographic MIMO）是传统大规模MIMO的下一代形态，其本质是将电磁波辐射与接收面从有限天线拓展为连续的电磁阵面，实现通信信号的三维空间调控。全息MIMO具有极高的空间分辨率和波束塑造能力，特别适用于近场通信、毫米波/太赫兹通信和通信感知一体化等前沿应用。

本人研究内容：在全息MIMO系统建模、波束设计与性能分析方面开展了系统研究。提出了面向近场波束赋形的叠层全息超表面结构，并构建了硬件受限场景下的广义信道模型与能效分析框架。相关工作发表于IEEE TWC、TCOM等期刊，并获得EPSRC项目“Platform Driving the Ultimate Connectivity”海报一等奖，多项研究成果被国际同行广泛引用。

期刊论文：

[1]  Qingchao Li, Mohammed El-Hajjar, Yanshi Sun, Lajos Hanzo, “Performance Analysis of Reconfigurable Holographic Surfaces in the Near-Field Scenario of Cell-Free Networks Under Hardware Impairments” [J]. IEEE Transactions on Wireless Communications, 2024, 23(9): 11972-11984.

[2]  Qingchao Li, Mohammed El-Hajjar, Yanshi Sun, Ibrahim Hemadeh, Arman Shojaeifard, Lajos Hanzo, “Energy-Efficient Reconfigurable Holographic Surfaces Operating in the Presence of Realistic Hardware Impairments” [J]. IEEE Transactions on Communications, 2024, 72(8): 5226-5238.

[3]  Qingchao Li, Mohammed El-Hajjar, Chao Xu, Jiancheng An, Chau Yune, Lajos Hanzo, “Stacked Intelligent Metasurfaces for Holographic MIMO Aided Cell-Free Networks” [J]. IEEE Transactions on Communications, 2024.

[4]  Qingchao Li, Mohammed El-Hajjar, Chao Xu, Jiancheng An, Chau Yuen, Lajos Hanzo, “Stacked Intelligent Metasurface-Based Transceiver Design for Near-Field Wideband Systems” [J]. IEEE Transactions on Communications, 2025.

3. 无蜂窝通信网络（Cell-Free Networks）

研究方向介绍：无蜂窝通信网络是一种超越传统小区划分的网络架构，采用密集部署的大量接入点共同服务所有用户，实现空间资源的集中式或分布式调度，提升频谱效率、均衡用户体验，特别适用于高移动性、海量连接与边缘通信场景，是构建未来6G空天地一体网络的关键技术之一。

本人研究内容：深入研究了Cell-Free架构下的全息MIMO与智能超表面集成机制，提出了多种联合波束设计、用户关联与干扰抑制算法，在近场条件下构建了硬件受限场景下的系统性能下界模型，相关成果发表在IEEE TWC、IEEE TCOM、IEEE TVT等主流期刊。

期刊论文：

[1]  Qingchao Li, Mohammed El-Hajjar, Yanshi Sun, Lajos Hanzo, “Performance Analysis of Reconfigurable Holographic Surfaces in the Near-Field Scenario of Cell-Free Networks Under Hardware Impairments” [J]. IEEE Transactions on Wireless Communications, 2024, 23(9): 11972-11984.

[2] Qingchao Li, Mohammed El-Hajjar, Chao Xu, Jiancheng An, Chau Yune, Lajos Hanzo, “Stacked Intelligent Metasurfaces for Holographic MIMO Aided Cell-Free Networks” [J]. IEEE Transactions on Communications, 2024.

[3]   Qingchao Li, Mohammed El-Hajjar, Chao Xu, Chao Zhang, Lajos Hanzo, “Hierarchical Beamforming Design for XL-MIMO with Hardware Impairments in Cell-Free Networks” [J]. IEEE Transactions on Vehicular Technology, 2025.

[4]  Qingchao Li, Mohammed El-Hajjar, Chao Xu, Kunlun Li, Xinyu Feng, Lajos Hanzo, “Holographic MIMO Aided Integrated User-Centric Cell-Free Terrestrial and Non-Terrestrial Networks” [J], IEEE Network, 2025.

4. 低轨卫星通信网络（LEO Satellite Communication Networks）

研究方向介绍：低轨卫星通信网络（LEO）通过大规模部署低轨道卫星构建覆盖全球的宽带通信系统，具有低延迟、高吞吐、易部署等优势，是未来6G非地面网络（NTN）的重要组成部分。LEO网络面临快速移动、频繁切换、星地链路动态变化等挑战，需要在物理层、链路层与系统架构层进行全新设计。

本人研究内容：系统研究了LEO卫星网络中的多高度轨道组网机制、信道建模与波束赋形策略，并提出了基于全息超表面与星地协同波束设计的集成方案。代表性成果发表于IEEE TWC和IEEE Network，并针对LEO卫星在Cell-Free网络中的融合问题，提出了多轨道协同接入与广义协方差分析模型。

期刊论文：

[1]  Qingchao Li, Mohammed El-Hajjar, Kaijun Cao, Chao Xu, Harald Haas, Lajos Hanzo, “Holographic Metasurface-Based Beamforming for Multi-Altitude LEO Satellite Networks” [J]. IEEE Transactions on Wireless Communications, 2025, 24(4): 3103-3116.

[2] Qingchao Li, Mohammed El-Hajjar, Chao Xu, Kunlun Li, Xinyu Feng, Lajos Hanzo, “Holographic MIMO Aided Integrated User-Centric Cell-Free Terrestrial and Non-Terrestrial Networks” [J], IEEE Network, 2025.

[3]   Chao Zhang, Qingchao Li, Chao Xu, Lie-Liang Yang, Lajos Hanzo, “Space-Air-Ground Integrated Networks: Their Channel Model and Performance Analysis” [J]. IEEE Open Journal of Vehicular Technology, 2025.