{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:58:26Z","timestamp":1760147906092,"version":"build-2065373602"},"reference-count":29,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2023,3,10]],"date-time":"2023-03-10T00:00:00Z","timestamp":1678406400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China","award":["61971032","F2022402001","A2020402013","D2021337"],"award-info":[{"award-number":["61971032","F2022402001","A2020402013","D2021337"]}]},{"name":"Hebei Natural Science Foundation","award":["61971032","F2022402001","A2020402013","D2021337"],"award-info":[{"award-number":["61971032","F2022402001","A2020402013","D2021337"]}]},{"name":"Open Fund of Chongqing Engineering Research Center of Intelligent Sensing Technology and Microsystem","award":["61971032","F2022402001","A2020402013","D2021337"],"award-info":[{"award-number":["61971032","F2022402001","A2020402013","D2021337"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Sixth generation (6G) wireless networks require very low latency and an ultra-high data rate, which have become the main challenges for future wireless communications. To effectively balance the requirements of 6G and the extreme shortage of capacity within the existing wireless networks, sensing-assisted communications in the terahertz (THz) band with unmanned aerial vehicles (UAVs) is proposed. In this scenario, the THz-UAV acts as an aerial base station to provide information on users and sensing signals and detect the THz channel to assist UAV communication. However, communication and sensing signals that use the same resources can cause interference with each other. Therefore, we research a cooperative method of co-existence between sensing and communication signals in the same frequency and time allocation to reduce the interference. We then formulate an optimization problem to minimize the total delay by jointly optimizing the UAV trajectory, frequency association, and transmission power of each user. The resulting problem is a non-convex and mixed integer optimization problem, which is challenging to solve. By resorting to the Lagrange multiplier and proximal policy optimization (PPO) method, we propose an overall alternating optimization algorithm to solve this problem in an iterative way. Specifically, given the UAV location and frequency, the sub-problem of the sensing and communication transmission powers is transformed into a convex problem, which is solved by the Lagrange multiplier method. Second, in each iteration, for given sensing and communication transmission powers, we relax the discrete variable to a continuous variable and use the PPO algorithm to tackle the sub-problem of joint optimization of the UAV location and frequency. The results show that the proposed algorithm reduces the delay and improves the transmission rate when compared with the conventional greedy algorithm.<\/jats:p>","DOI":"10.3390\/s23063005","type":"journal-article","created":{"date-parts":[[2023,3,10]],"date-time":"2023-03-10T03:35:42Z","timestamp":1678419342000},"page":"3005","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["UAV Trajectory Design and Power Optimization for Terahertz Band-Integrated Sensing and Communications"],"prefix":"10.3390","volume":"23","author":[{"given":"Ying","family":"Gao","sequence":"first","affiliation":[{"name":"School of Information and Electrical Engineering, Hebei University of Engineering, Handan 056038, China"}]},{"given":"Hongmei","family":"Xue","sequence":"additional","affiliation":[{"name":"School of Information and Electrical Engineering, Hebei University of Engineering, Handan 056038, China"},{"name":"Chongqing Engineering Research Center of Intelligent Sensing Technology and Microsystem, Chongqing 400065, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5607-3271","authenticated-orcid":false,"given":"Long","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Information and Electrical Engineering, Hebei University of Engineering, Handan 056038, China"}]},{"given":"Enchang","family":"Sun","sequence":"additional","affiliation":[{"name":"Beijing Advanced Innovation Center for Future Internet Technology, Beijing University of Technology, Beijing 100124, China"},{"name":"Faculty of Information Technology, Beijing University of Technology, Beijing 100124, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,3,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"117460","DOI":"10.1109\/ACCESS.2019.2929241","article-title":"A Survey on 5G Millimeter Wave Communications for UAV-Assisted Wireless Networks","volume":"7","author":"Zhang","year":"2019","journal-title":"IEEE Access"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1109\/JSAC.2014.2328098","article-title":"What will 5G be?","volume":"32","author":"Andrews","year":"2014","journal-title":"IEEE J. Sel. Area in Comm."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1109\/MCOM.001.1900698","article-title":"Next generation terahertz communications: A rendezvous of sensing, imaging, and localization","volume":"58","author":"Sarieddeen","year":"2020","journal-title":"IEEE Commun. Mag."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1109\/MVT.2019.2921208","article-title":"6G wireless networks: Vision, requirements, architecture, and key technologies","volume":"14","author":"Zhang","year":"2019","journal-title":"IEEE Veh. Technol. Mag."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"994","DOI":"10.1109\/COMST.2022.3149272","article-title":"A Survey on Fundamental Limits of Integrated Sensing and Communication","volume":"24","author":"Liu","year":"2022","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1728","DOI":"10.1109\/JSAC.2022.3156632","article-title":"Integrated Sensing and Communications: Toward Dual-Functional Wireless Networks for 6G and Beyond","volume":"40","author":"Liu","year":"2022","journal-title":"IEEE J. Sel. Areas Commun."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2103","DOI":"10.1109\/JSAC.2022.3157366","article-title":"Integrated Scheduling of Sensing, Communication, and Control for mmWave\/THz Communications in Cellular Connected UAV Networks","volume":"40","author":"Zhang","year":"2022","journal-title":"IEEE J. Sel. Areas Comm."},{"key":"ref_8","first-page":"2327","article-title":"Privacy-Aware Laser Wireless Power Transfer for Aerial Multi-Access Edge Computing: A Colonel Blotto Game Approach","volume":"15","author":"Zhang","year":"2022","journal-title":"IEEE Internet Things"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"16330","DOI":"10.1109\/TVT.2020.3035831","article-title":"Performance Analysis of Terahertz Unmanned Aerial Vehicular Networks","volume":"69","author":"Wang","year":"2020","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1109\/JPROC.2014.2365517","article-title":"Radar spectrum engineering and management: Technical and regulatory issues","volume":"103","author":"Griffiths","year":"2015","journal-title":"Proc. IEEE"},{"key":"ref_11","first-page":"611","article-title":"Integrated radar and communications based on chirped spread-spectrum techniques","volume":"1","author":"Roberton","year":"2013","journal-title":"IEEE MTT-S Int. Microw. Symp. Dig."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"11123","DOI":"10.1109\/JIOT.2021.3051603","article-title":"Supporting IoT With Rate-Splitting Multiple Access in Satellite and Aerial-Integrated Networks","volume":"8","author":"Lin","year":"2021","journal-title":"IEEE Internet Things J."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Yuan, Z., Yang, Y., Wang, D., and Ma, X. (2022). Energy-Efficient Trajectory Optimization for UAV-Enabled Cellular Communications Based on Physical-Layer Security. Aerospace, 9.","DOI":"10.3390\/aerospace9020050"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Lan, T., Qin, D., and Sun, G. (2021). Joint Optimization on Trajectory, Cache Placement, and Transmission Power for Minimum Mission Time in UAV-Aided Wireless Networks. ISPRS Int. J. Geo-Inf., 10.","DOI":"10.3390\/ijgi10070426"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Ko, Y., Kim, J., Duguma, D.G., Astillo, P.V., You, I., and Pau, G. (2021). Drone Secure Communication Protocol for Future Sensitive Applications in Military Zone. Sensors, 21.","DOI":"10.3390\/s21062057"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Krichen, M., Adoni, W.Y.H., Mihoub, A., Alzahrani, M.Y., and Nahhal, T. (2022). Security Challenges for Drone Communications: Possible Threats, Attacks and Countermeasures, SMARTTECH.","DOI":"10.1109\/SMARTTECH54121.2022.00048"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Li, Q., Nayak, A., Zhang, Y., and Yu, F.R. (2022). A Cooperative Recharging-Transmission Strategy In Powered UAV-Aided Terahertz Downlink Networks. IEEE Trans. Veh. Technol., 1939\u20139359.","DOI":"10.1109\/TVT.2022.3227989"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1984","DOI":"10.1109\/LCOMM.2021.3064067","article-title":"Joint Location, Bandwidth and Power Optimization for THz-enabled UAV Communications","volume":"25","author":"Xu","year":"2021","journal-title":"IEEE Commun. Lett."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"858","DOI":"10.1002\/mop.33185","article-title":"Intelligent reflecting surface-assisted terahertz communication towards B5G and 6G: State-of-the-art","volume":"64","author":"Raza","year":"2022","journal-title":"Microw. Opt. Technol. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/TCCN.2017.2666266","article-title":"Radar-Communications Convergence: Coexistence, Cooperation, and Co-Design","volume":"3","author":"Chiriyath","year":"2017","journal-title":"IEEE Trans. Cogn. Commun. Netw."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1109\/TSP.2017.2755603","article-title":"Joint Design of Overlaid Communication Systems and Pulsed Radars","volume":"66","author":"Zheng","year":"2018","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"464","DOI":"10.1109\/TSP.2015.2483485","article-title":"Inner Bounds on Performance of Radar and Communications Co-Existence","volume":"64","author":"Chiriyath","year":"2015","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3717","DOI":"10.1109\/TAES.2022.3155711","article-title":"Refracting RIS-Aided Hybrid Satellite-Terrestrial Relay Networks: Joint Beamforming Design and Optimization","volume":"58","author":"Lin","year":"2022","journal-title":"IEEE Trans. Aerosp. Electron. Syst."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Lin, Z., An, K., Niu, H., Hum, Y., Hu, Y., Chatzinotas, S., Zheng, G., and Wang, J. SLNR-based Secure Energy Efficient Beamforming in Multibeam Satellite Systems. IEEE Trans. Aerosp. Electron. Syst., 2022. in press.","DOI":"10.1109\/TAES.2022.3190238"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"11214","DOI":"10.1109\/JIOT.2021.3126329","article-title":"Joint Optimization of UAV Trajectory and Sensor Uploading Powers for UAV-Assisted Data Collection in Wireless Sensor Networks","volume":"9","author":"Wang","year":"2022","journal-title":"IEEE Interent Things"},{"key":"ref_26","first-page":"657","article-title":"Joint Beamforming and Power Allocation for Satellite-Terrestrial Integrated Networks With Non-Orthogonal Multiple Access","volume":"13","author":"Lin","year":"2019","journal-title":"IEEE J.-STSP"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Zhang, L., Ma, X., Zhuang, Z., Xu, H., Sharma, V., and Han, Z. (2022). Q-Learning Aided Intelligent Routing with Maximum Utility in Cognitive UAV Swarm for Emergency Communications. IEEE Trans. Veh. Technol., in press.","DOI":"10.36227\/techrxiv.19365389"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2402","DOI":"10.1109\/TWC.2014.2386335","article-title":"Multi-Ray Channel Modeling and Wideband Characterization for Wireless Communications in the Terahertz Band","volume":"14","author":"Han","year":"2015","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Zhang, L., Zhang, H., Guo, C., Xu, H., Song, L., and Han, Z. (2020, January 7\u201311). Satellite-Aerial Integrated Computing in Disasters: User Association and Offloading Decision. Proceedings of the 2020 IEEE International Conference on Communications (ICC), Dublin, Ireland.","DOI":"10.1109\/ICC40277.2020.9148796"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/6\/3005\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:51:52Z","timestamp":1760122312000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/6\/3005"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,3,10]]},"references-count":29,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2023,3]]}},"alternative-id":["s23063005"],"URL":"https:\/\/doi.org\/10.3390\/s23063005","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2023,3,10]]}}}