Jinsong Chen

With integrated sensing and communications (ISAC) and reconfigurable intelligent surface (RIS) emerging as critical enablers for future mobile communications, their combination has attracted increasing attention lately. To effectively utilize RIS for improving ISAC, we propose two novel designs targeting different scenarios. The first design strikes for a spectral-efficient ISAC by seeking to maximize the weighted sum rate (WSR) of communications and minimize sensing radiation pattern approximation error. The second design aims to achieve an energy-efficient ISAC by optimizing the power allocation between communications and sensing subject to communication quality of service (QoS) constraints. Different optimization problems are formulated for the two designs, with practical constraints of RIS considered, including unit modulus and discrete phase shift. Efficient solutions are developed for the non-convex optimization problems by adeptly employing techniques including weighted minimum mean squared error (WMMSE), fractional programming (FP), second-order cone programming (SOCP), semi-definite relaxing (SDR), and feasibility check. Simulation results demonstrate the non-trivial improvements of WSR, communication energy efficiency and sensing radiation patterns achieved by the proposed designs, also highlighting their superiority over the conventional methods.

Intelligent reflective surface (IRS) assisted integrated sensing and communications (ISAC) is a promising technology for future mobile communications. However, high channel correlation, which may significantly degrade the performance of ISAC, has been overlooked. This letter addresses the issue by introducing user grouping to IRS-assisted ISAC. We design a novel user grouping scheme to minimize intra-group channel correlation. We also derive the asymptotically optimal number of user groups. Moreover, for any user group, we provide a joint base station and IRS beamforming design by applying the alternative optimization strategy, together with the weighted minimum mean squared error and discrete phase shift optimization techniques. Simulation results demonstrate substantial performance enhancement brought by user grouping to IRS-assisted ISAC.

This paper investigates joint beamforming in a secure integrated sensing and communications (ISAC) system assisted by reconfigurable intelligent surfaces (RIS). The system communicates with legitimate downlink users, detecting a potential target, which is a potential eavesdropper attempting to intercept the downlink communication information from the base station (BS) to legitimate users. To enhance the physical-layer secrecy of the system, we design and introduce interference signals at the BS to disrupt eavesdroppers’ attempts to intercept legitimate communication information. The BS simultaneously transmits communication and interference signals, both utilized for communication and sensing to guarantee the sensing and communication quality. By jointly optimizing the BS active beamformer and the RIS passive beamforming matrix, we aim to maximize the achievable secrecy rate and radiation power of the system. We develop an effective scheme to find the active beamforming matrix through fractional programming (FP) and semi-definite programming (SDP) techniques and obtain the RIS phase shift matrix via a local search technique. Simulation results validate the effectiveness of the proposed methods in enhancing communication and sensing performance. Additionally, the results demonstrate the effectiveness of introducing the interference signals and RIS in enhancing the physical-layer secrecy of the ISAC system.

The surface state of metallic materials significantly affect their physical, chemical, and corrosion behavior. In the present study, superhydrophobic coating with copper deposits fabricated using a jet-electrodeposition device on the pure copper substrates for reducing the corrosion rate of the copper substrates was studied. The effect of the micro-nano structured superhydrophobic coating on the improvement of corrosion resistance was investigated. Factors including the microstructures and wetting properties of coating were comprehensively analyzed using a scanning electron microscope, a Fourier transformed infrared and a surface contact angle meter. Results showed that the superhydrophobic coatings demonstrated a micro-nanostructure on the copper substrates. After modifying the copper deposits with stearic acid, a superhydrophobic surface was consequently obtained. The static contact angle (CA) and the sliding angle of the copper-based superhydrophobic surface were 151.6° and 5.7°, respectively. The samples covered with superhydrophobic coating exhibited relatively higher corrosion potential and lower corrosion current than the bared pure copper samples, indicating a notable enhancement of corrosion resistance characterized using polarization tests by an electrochemical workstation.