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在上一期前沿文献中推荐中，介绍了通信新材料及相关技术领域的最新进展，包括：用于5G和6G的氧化物电子器件，一种基于大面积电子器件的工作频率位千兆赫的相控阵，5G基础设施的治理:介于路径依赖和基于风险的方法之间，以及基于可编程元曲面的5G移动通信波束控制。可重构智能表面（RIS），以及智能反射面（IRS）被认为可以应用于优化未来的无线网络。在本期的文献推荐中，关注点着眼于相关技术的研究进展，选取了：具有集成传感能力的可重构智能表面、智能反射面辅助无线通信的教程、多用户MISO无线通信中的信道估计，以及可抵御分布式窃听攻击的安全时空调制毫米波无线链路四篇文献，供相关领域的科研人员参考。领域一具有集成传感能力的可重构智能表面 A reconfigurable intelligent surface with integrated sensing capability Idban Alamzadeh, etc. Scientific Reports, 2021 Reconfigurable reflective surfaces can alter the propagation environment to improve wireless communication and power transfer. Paramount to this operation—which has attracted much attention recently—is the assumption that the reflective surface has prior knowledge of the propagation environment, for example, the direction/location of the transmitter and the intended receiver(s). To address this need, we propose a reconfigurable reflective metasurface with integrated sensing capabilities. By modifying the tunable meta-atoms constituting the metasurface, we couple small portions of the incident wave to an array of sensing waveguides. As an illustrative example, we demonstrate the ability to use the sampled incident wave to detect its angle of arrival. In addition, we propose and numerically demonstrate the possibility to reduce the required sensors, i.e., the number of radio frequency (RF) chains needed to acquire the sensed signals, by leveraging the inherent metasurface’s tunable multiplexing capability. A reconfigurable reflective metasurface with integrated sensing capabilities can benefit wireless communications, wireless power transfer, RF sensing, and smart sensors. https://www.nature.com/articles/s41598-021-99722-x Fig. Proposed hybrid RIS hardware design with integrated sensing capability. 领域二智能反射面辅助无线通信的教程 Intelligent Reflecting Surface-Aided Wireless Communications: A Tutorial Qingqing Wu, etc. IEEE Transactions on Communications, 2021, 69(5): 3313-3351 Intelligent reflecting surface (IRS) is an enabling technology to engineer the radio signal propagation in wireless networks. By smartly tuning the signal reflection via a large number of low-cost passive reflecting elements, IRS is capable of dynamically altering wireless channels to enhance the communication performance. It is thus expected that the new IRS-aided hybrid wireless network comprising both active and passive components will be highly promising to achieve a sustainable capacity growth cost-effectively in the future. Despite its great potential, IRS faces new challenges to be efficiently integrated into wireless networks, such as reflection optimization, channel estimation, and deployment from communication design perspectives. In this paper, we provide a tutorial overview of IRS-aided wireless communications to address the above issues, and elaborate its reflection and channel models, hardware architecture and practical constraints, as well as various appealing applications in wireless networks. Moreover, we highlight important directions worthy of further investigation in future work. https://ieeexplore.ieee.org/document/9326394 Fig. Potential paradigm shifts of wireless system/network designs with IRS. 领域三多用户MISO无线通信中的信道估计 Channel Estimation for RIS-Empowered Multi-User MISO Wireless Communications Li Wei, etc. IEEE Transactions on Communications, 2021, 69(6): 4144-4157 Reconfigurable Intelligent Surfaces (RISs) have been recently considered as an energy-efficient solution for future wireless networks due to their fast and low-power configuration, which has increased potential in enabling massive connectivity and low-latency communications. Accurate and low-overhead channel estimation in RIS-based systems is one of the most critical challenges due to the usually large number of RIS unit elements and their distinctive hardware constraints. In this paper, we focus on the uplink of a RIS-empowered multi-user Multiple Input Single Output (MISO) uplink communication systems and propose a channel estimation framework based on the parallel factor decomposition to unfold the resulting cascaded channel model. We present two iterative estimation algorithms for the channels between the base station and RIS, as well as the channels between RIS and users. One is based on alternating least squares (ALS), while the other uses vector approximate message passing to iteratively reconstruct two unknown channels from the estimated vectors. To theoretically assess the performance of the ALS-based algorithm, we derived its estimation Cramér-Rao Bound (CRB). We also discuss the downlink achievable sum rate computation with estimated channels and different precoding schemes for the base station. Our extensive simulation results show that our algorithms outperform benchmark schemes and that the ALS technique achieves the CRB. It is also demonstrated that the sum rate using the estimated channels always reach that of perfect channels under various settings, thus, verifying the effectiveness and robustness of the proposed estimation algorithms. https://ieeexplore.ieee.org/document/9366805 Fig. The considered RIS-empowered multi-user MISO communication system consisting of an K -antenna BS and M single-antenna mobile users. 领域四可抵御分布式窃听攻击的安全时空调制毫米波无线链路 Secure space–time-modulated millimetre-wave wireless links that are resilient to distributed eavesdropper attacks Suresh Venkatesh, etc. Nature Electronics, 2021 As wireless networks move to millimetre-wave (mm-wave) and terahertz (THz) frequencies for 5G communications and beyond, ensuring security and resilience to eavesdropper attacks has become increasingly important. Traditional encryption methods are challenging to scale for high-bandwidth, ultralow-latency applications. An alternative approach is to use physical-layer techniques that rely on the physics of signal propagation to incorporate security features without the need for an explicit key exchange. Ensuring security through the use of directional, narrow-beam-like features of mm-wave/THz signals has proven to be vulnerable to passive eavesdroppers. Here we report a space-time modulation approach that ensures security by enforcing loss of information through selective spectral aliasing towards the direction of eavesdroppers, even though the channel can be physically static. This is achieved by using custom-designed spatio-temporal transmitter arrays realized in silicon chips with packaged antennas operating in the 71–76 GHz range. We also analytically and experimentally demonstrate the resilience of our links against distributed and synchronized eavesdropper attacks in the mm-wave band. https://www.nature.com/articles/s41928-021-00664-z Fig. Measured resilience against a distributed and colluding eavesdropper attack with known channel (channel inversion attack) on the presented STMA in the 71–76 GHz range.

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