{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,1]],"date-time":"2026-03-01T11:56:31Z","timestamp":1772366191709,"version":"3.50.1"},"reference-count":23,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2022,6,15]],"date-time":"2022-06-15T00:00:00Z","timestamp":1655251200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The hybrid combination between underwater optical wireless communication (UOWC) and radio frequency (RF) is a vital demand for enabling communication through the air\u2013water boundary. On the other hand, non-orthogonal multiple access (NOMA) is a key technology for enhancing system performance in terms of spectral efficiency. In this paper, we propose a downlink NOMA-based dual-hop hybrid RF-UOWC with decode and forward (DF) relaying. The UOWC channels are characterized by exponential-generalized Gamma (EGG) fading, while the RF channel is characterized by Rayleigh fading. Exact closed-form expressions of outage probabilities and approximated closed-form expressions of ergodic capacities are derived, for each NOMA individual user and the overall system as well, under the practical assumption of imperfect successive interference cancellation (SIC). These expressions are then verified via Monte-Carlo simulation for various underwater scenarios. To gain more insight into the system performance, we analyzed the asymptotic outage probabilities and the diversity order. Moreover, we formulated and solved a power allocation optimization problem to obtain an outage-optimal performance. For the sake of comparison and to highlight the achievable gain, the system performance is compared against a benchmark orthogonal multiple access (OMA)-based system.<\/jats:p>","DOI":"10.3390\/s22124521","type":"journal-article","created":{"date-parts":[[2022,6,16]],"date-time":"2022-06-16T03:01:22Z","timestamp":1655348482000},"page":"4521","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Performance Analysis of Dual-Hop Hybrid RF-UOWC NOMA Systems"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5117-7880","authenticated-orcid":false,"given":"Ahmed","family":"Samir","sequence":"first","affiliation":[{"name":"Faculty of Engineering at Shoubra, Benha University, Cairo 13511, Egypt"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5963-6001","authenticated-orcid":false,"given":"Mohamed","family":"Elsayed","sequence":"additional","affiliation":[{"name":"Faculty of Engineering at Shoubra, Benha University, Cairo 13511, Egypt"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7234-7642","authenticated-orcid":false,"given":"Ahmad A. Aziz","family":"El-Banna","sequence":"additional","affiliation":[{"name":"Faculty of Engineering at Shoubra, Benha University, Cairo 13511, Egypt"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8461-6547","authenticated-orcid":false,"given":"Imran","family":"Shafique Ansari","sequence":"additional","affiliation":[{"name":"James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9784-3703","authenticated-orcid":false,"given":"Khaled","family":"Rabie","sequence":"additional","affiliation":[{"name":"Department of Engineering, Manchester Metropolitan University, Manchester M1 5GF, UK"},{"name":"Department of Electrical and Electronic Engineering, University of Johannesburg, Johannesburg 2028, South Africa"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5900-6541","authenticated-orcid":false,"given":"Basem M.","family":"ElHalawany","sequence":"additional","affiliation":[{"name":"Faculty of Engineering at Shoubra, Benha University, Cairo 13511, Egypt"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"101935","DOI":"10.1016\/j.adhoc.2019.101935","article-title":"Underwater optical wireless communications, networking, and localization: A survey","volume":"94","author":"Saeed","year":"2019","journal-title":"Ad Hoc Netw."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2792","DOI":"10.1109\/JSEN.2019.2953277","article-title":"Opportunistic Cooperative Transmission for Underwater Communication Based on the Water\u2019s Key Physical Variables","volume":"20","author":"Wu","year":"2020","journal-title":"IEEE Sens. 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