Optical Intelligent Reflecting Surface for Mixed Dual-Hop FSO and Beamforming-Based RF System in C-RAN

• Published in: IEEE transactions on wireless communications Vol. 21; no. 10; pp. 8489 - 8506
• Main Authors: Pang, Weina, Wang, Ping, Han, Maojie, Li, Shuang, Yang, Pengfei, Li, Ganggang, Guo, Lixin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive optics; Beamforming; Bit error rate; Closed form solutions; Cloud radio access network; dual-hop mixed FSO and RF system; Exact solutions; Fading; Fading channels; Free-space optical communication; Hypergeometric functions; Mathematical analysis; Misalignment; Multivariate analysis; Optical device fabrication; Optical fiber communication; optical intelligent reflecting surface; Optical scattering; Optical transmitters; performance analysis; polar codes; Radio frequency; Reconfigurable intelligent surfaces; Signal to noise ratio; Statistical analysis; Weibull distribution
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2022.3166756

Optical intelligent reflecting surface (IRS) is an emerging and low-cost technology that can establish a stable communication route in free space optical (FSO) transmission environment with obstacles. In this work, optical IRS-aided dual-hop mixed FSO and RF system is first proposed for cloud radio access network (C-RAN). Specifically, polar codes are introduced to combat turbulence and building sway induced fading in FSO link, and transmit beamforming (TBF) technique is designed to achieve optimal data-rate for RF link. Supposing that the IRS-aided FSO link is subject to exponentiated Weibull distribution with geometric and misalignment loss, whereas the RF link experiences the Fisher-Snedecor <inline-formula> <tex-math notation="LaTeX">\mathcal {F} </tex-math></inline-formula> composite fading, the analytical closed-form outage probability expression is derived in terms of Meijer G and Lauricella multivariate hypergeometric functions with decode-and-forward strategy. Exact closed-form average bit error rate expressions are obtained when the relay of C-RAN adopts single antenna and multiantenna beamforming techniques. On the basis of moment generating function of end-to-end signal-to-noise ratio, the ergodic capacity is obtained in terms of univariate and multivariate Fox H-functions over independent but not identically distributed Fisher-Snedecor <inline-formula> <tex-math notation="LaTeX">\mathcal {F} </tex-math></inline-formula> fading channels. The correctness of the analytical results is verified through Monte-Carlo simulations. We further provide an asymptotic analysis and discuss the achievable diversity orders.