近年來，整合感知與通訊(ISAC)這項技術成為無線通訊領域中頗具發展性的一項技術。但是在這項技術中需要去克服雷達與通訊信號相互干擾(mutual interference)的問題。然而，在此研究中，我們針對基站(BS)發射出的通訊訊號以及雷達波形進行調整，並且在基站(BS)以及接收端(receiver)各放置一片可重構智能反射面(RIS)，並藉由調整 RIS 的元件相位以及基站的波束成型(beamforming)來減少相互干擾，並且在達到雷達目標接收到的功率維持在一定的情況下最大化接收端接收到的訊號之訊號與干擾加雜訊比(SINR)。為了最佳化SINR 的品質，我們建構了一種基於 Dinkelbach 方法的 BCD 演算法以調整兩片RIS 的相位以及基站的波束成型。模擬結果中顯示，透過調整相位以及波束成型，可以大幅改善接收端的 SINR，且可以從數據中得知，放置兩片 RIS 的效能明顯比只放置單一 RIS 以及不放置 RIS 還要更好。

In recent years, Integrated Sensing and Communication (ISAC) has emerged as a highly promising technology in the field of wireless communications. However, a significant challenge in this technology is the mutual interference between radar and communication signals. In this study, we address this issue by adjusting the communication signals and radar waveforms transmitted from the base station (BS). We place two reconfigurable intelligent surfaces (RIS) at the base station (BS) and the receiver end, and by adjusting the phase of the RIS elements and the beamforming of the BS, we aim to reduce mutual interference. Our goal is to maximize the signal-to-interferenceplus-noise ratio (SINR) at the receiver while ensuring that the power received by the radar target remains at a certain level. To optimize SINR quality, we have developed a BCD algorithm based on the Dinkelbach method to adjust the phases of the two RISs and the beamforming of the BS. Simulation results show that by adjusting the phases and beamforming, the SINR at the receiver can be significantly improved. The data also indicate that the performance with two RISs is noticeably better than with a single RIS or without any RIS.

[1] Q. Wu, S. Zhang, B. Zheng, C. You, and R. Zhang, “Intelligent reflecting surfaceaided wireless communications: A tutorial,” IEEE Transactions on Communications, vol. 69, no. 5, pp. 3313–3351, 2021.
[2] Q. Wu and R. Zhang, “Intelligent reflecting surface enhanced wireless network: Joint active and passive beamforming design,” in 2018 IEEE Global Communications Conference (GLOBECOM), 2018, pp. 1–6.
[3] Y. He, Y. Cai, H. Mao, and G. Yu, “Ris-assisted communication radar coexistence: Joint beamforming design and analysis,” IEEE Journal on Selected Areas in Communications, vol. 40, no. 7, pp. 2131–2145, 2022.
[4] F. Liu, C. Masouros, A. P. Petropulu, H. Griffiths, and L. Hanzo, “Joint radar and communication design: Applications, state-of-the-art, and the road ahead,”IEEE Transactions on Communications, vol. 68, no. 6, pp. 3834–3862, 2020.
[5] A. Hassanien, M. G. Amin, E. Aboutanios, and B. Himed, “Dual-function radar communication systems: A solution to the spectrum congestion problem,” IEEE Signal Processing Magazine, vol. 36, no. 5, pp. 115–126, 2019.
[6] R. Liu, M. Li, Y. Liu, Q. Wu, and Q. Liu, “Joint transmit waveform and passive beamforming design for ris-aided dfrc systems,” IEEE Journal of Selected Topics in Signal Processing, vol. 16, no. 5, pp. 995–1010, 2022.
[7] F. Liu, Y. Cui, C. Masouros, J. Xu, T. X. Han, Y. C. Eldar, and S. Buzzi, “Integrated sensing and communications: Toward dual-functional wireless networks for 6g and beyond,” IEEE Journal on Selected Areas in Communications, vol. 40,no. 6, pp. 1728–1767, 2022.
[8] R. S. P. Sankar, S. P. Chepuri, and Y. C. Eldar, “Beamforming in integrated sensing and communication systems with reconfigurable intelligent surfaces,” IEEE Transactions on Wireless Communications, vol. 23, no. 5, pp. 4017–4031, 2024.
[9] Z. Liu, Y. Liu, S. Shen, Q. Wu, and Q. Shi, “Enhancing isac network throughput using beyond diagonal ris,” IEEE Wireless Communications Letters, vol. 13, no. 6, pp. 1670–1674, 2024.
[10] K. Zhong, J. Hu, C. Pan, M. Deng, and J. Fang, “Joint waveform and beamforming design for ris-aided isac systems,” IEEE Signal Processing Letters, vol. 30, pp.165–169, 2023.
[11] Z. Chen, J. Ye, and L. Huang, “A two-stage beamforming design for active ris aided dual functional radar and communication,” in 2023 IEEE Wireless Communications and Networking Conference (WCNC), 2023, pp. 1–6.
[12] J. Xiao, J. Tang, and J. Chen, “Efficient radar detection for ris-aided dualfunctional radar-communication system,” in 2023 IEEE 97th Vehicular Technology Conference (VTC2023-Spring), 2023, pp. 1–6.
[13] M. Rihan, A. Zappone, and S. Buzzi, “Robust ris-assisted mimo communicationradar coexistence: Joint beamforming and waveform design,” IEEE Transactions on Communications, vol. 71, no. 11, pp. 6647–6661, 2023.
[14] X. Wang, Z. Fei, Z. Zheng, and J. Guo, “Joint waveform design and passive beamforming for ris-assisted dual-functional radar-communication system,” IEEE Transactions on Vehicular Technology, vol. 70, no. 5, pp. 5131–5136, 2021.
[15] Q. Zhu, M. Li, R. Liu, and Q. Liu, “Joint transceiver beamforming and reflecting design for active ris-aided isac systems,” IEEE Transactions on Vehicular Technology, vol. 72, no. 7, pp. 9636–9640, 2023.
[16] Z. Yu, H. Ren, C. Pan, G. Zhou, B. Wang, M. Dong, and J. Wang, “Active ris-aided isac systems: Beamforming design and performance analysis,” IEEE Transactions on Communications, vol. 72, no. 3, pp. 1578–1595, 2024.
[17] H. Luo, R. Liu, M. Li, Y. Liu, and Q. Liu, “Joint beamforming design for risassisted integrated sensing and communication systems,” IEEE Transactions on Vehicular Technology, vol. 71, no. 12, pp. 13 393–13 397, 2022.
[18] M. Di Renzo, A. Zappone, M. Debbah, M.-S. Alouini, C. Yuen, J. de Rosny, and S. Tretyakov, “Smart radio environments empowered by reconfigurable intelligent surfaces: How it works, state of research, and the road ahead,” IEEE Journal on Selected Areas in Communications, vol. 38, no. 11, pp. 2450–2525, 2020.