{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T15:04:12Z","timestamp":1784905452753,"version":"3.55.0"},"reference-count":21,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2021,11,28]],"date-time":"2021-11-28T00:00:00Z","timestamp":1638057600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the Open Project of Shandong Key Laboratory of Optical Communication Science and Technology, Liaocheng University","award":["SDOC201901"],"award-info":[{"award-number":["SDOC201901"]}]},{"name":"the open research fund of Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education","award":["JZNY202115"],"award-info":[{"award-number":["JZNY202115"]}]},{"name":"Postgraduate Research &amp; Practice Innovation Program of Jiangsu Province","award":["KYCX20_0711"],"award-info":[{"award-number":["KYCX20_0711"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>This paper focuses on an unmanned aerial vehicle (UAV) assisted hybrid free-space optical (FSO)\/radio frequency (RF) communication system. Considering the rate imbalance between the FSO and RF links, a buffer is employed at the UAV. Initially, theoretical models of energy consumption and throughput are obtained for the hybrid system. Based on these models, the theoretical expression of the energy efficiency is derived. Then, a nonconvex trajectory optimization problem is formulated by maximizing the energy efficiency of the hybrid system under the buffer constraint, velocity constraint, acceleration constraint, start\u2013end position constraint, and start\u2013end velocity constraint. By using the sequential convex optimization and first-order Taylor approximation, the nonconvex problem is transformed into a convex one. An iterative algorithm is proposed to solve the problem. Numerical results verify the efficiency of the proposed algorithm and also show the effects of buffer size on a UAV\u2019s trajectory.<\/jats:p>","DOI":"10.3390\/e23121596","type":"journal-article","created":{"date-parts":[[2021,11,29]],"date-time":"2021-11-29T05:23:02Z","timestamp":1638163382000},"page":"1596","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Energy-Efficient Trajectory Optimization for UAV-Based Hybrid FSO\/RF Communications with Buffer Constraints"],"prefix":"10.3390","volume":"23","author":[{"given":"Rong-Rong","family":"Lu","sequence":"first","affiliation":[{"name":"Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yang","family":"Ma","sequence":"additional","affiliation":[{"name":"National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sheng-Hong","family":"Lin","sequence":"additional","affiliation":[{"name":"Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China"},{"name":"Department of Automation Engineering, Nanjing Institute of Mechatronic Technology, Nanjing 211306, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bingyuan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Shandong Key Laboratory of Optical Communication Science and Technology, Liaocheng University, Liaocheng 252059, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9202-5656","authenticated-orcid":false,"given":"Qinglin","family":"Wang","sequence":"additional","affiliation":[{"name":"Shandong Key Laboratory of Optical Communication Science and Technology, Liaocheng University, Liaocheng 252059, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5745-4554","authenticated-orcid":false,"given":"Jin-Yuan","family":"Wang","sequence":"additional","affiliation":[{"name":"Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China"},{"name":"Shandong Key Laboratory of Optical Communication Science and Technology, Liaocheng University, Liaocheng 252059, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2946","DOI":"10.1109\/JSAC.2021.3088656","article-title":"Hovering UAV-based FSO communications: Channel modeling, performance analysis, and parameter optimization","volume":"39","author":"Wang","year":"2021","journal-title":"IEEE J. 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