{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,19]],"date-time":"2026-03-19T01:21:23Z","timestamp":1773883283312,"version":"3.50.1"},"reference-count":20,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2023,12,12]],"date-time":"2023-12-12T00:00:00Z","timestamp":1702339200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NNSF of the China","award":["62127802"],"award-info":[{"award-number":["62127802"]}]},{"name":"NNSF of the China","award":["61821001"],"award-info":[{"award-number":["61821001"]}]},{"name":"NNSF of the China","award":["XDA30010100"],"award-info":[{"award-number":["XDA30010100"]}]},{"name":"the Strategic Priority Research Program of Chinese Academy of Sciences","award":["62127802"],"award-info":[{"award-number":["62127802"]}]},{"name":"the Strategic Priority Research Program of Chinese Academy of Sciences","award":["61821001"],"award-info":[{"award-number":["61821001"]}]},{"name":"the Strategic Priority Research Program of Chinese Academy of Sciences","award":["XDA30010100"],"award-info":[{"award-number":["XDA30010100"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>D-band (110\u2013170 GHz) has been regarded as a potential candidate for the future 6G wireless network because of its large available bandwidth. At present, the lack of electrical amplifiers operating in the high frequency band and the strong nonlinear effect, i.e., the D-band, are still important problems. Therefore, effective methods to mitigate the nonlinear issue resulting from the ROF link are indispensable, among of which machine learning is considered the most effective paradigm to model the nonlinear behavior due to its nonlinear active function and structure. In order to reduce the computation amount and burden, a novel deep learning neural network equalizer connected with typical mathematical frequency offset estimation (FOE) and carrier phase recovery (CPR) algorithms is proposed. We implement D-band 45 Gbaud PAM-4 and 20 Gbaud PAM-8 ROF transmission simulations, and the simulation results show that the real value neural network (RVNN) equalizer connected with the Viterbi-Viterbi algorithm exhibits better compensation ability for nonlinear impairment, especially when dealing with serious inter-symbol interference and nonlinear effects. In our experiment, we employ coherent detection to further improve the receiver sensitivity, so a complex baseband signal after down conversion at the receiver is inherently produced. In this scenario, the complex value neural network (CVNN) and RVNN equalizer connected with the Viterbi-Viterbi algorithm have better BER performance with an error rate lower than the HD-FEC threshold of 3.8 \u00d7 10\u22123.<\/jats:p>","DOI":"10.3390\/s23249773","type":"journal-article","created":{"date-parts":[[2023,12,12]],"date-time":"2023-12-12T05:23:22Z","timestamp":1702358602000},"page":"9773","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Deep Learning Equalizer Connected with Viterbi-Viterbi Algorithm for PAM D-Band Radio over Fiber Link"],"prefix":"10.3390","volume":"23","author":[{"given":"Tangyao","family":"Xie","sequence":"first","affiliation":[{"name":"Beijing Key Laboratory of Work Safety Intelligent Monitoring, Beijing University of Posts and Telecommunications, Beijing 100876, China"}]},{"given":"Qiang","family":"Sheng","sequence":"additional","affiliation":[{"name":"Key Laboratory of Space Utilization, Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences, Beijing 100094, China"}]},{"given":"Jianguo","family":"Yu","sequence":"additional","affiliation":[{"name":"Beijing Key Laboratory of Work Safety Intelligent Monitoring, Beijing University of Posts and Telecommunications, Beijing 100876, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,12,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Dore, J.B., Belot, D., Mercier, E., Bicais, S., and Strinati, E.C. 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