This book presents the modeling and transmission theory of RF OAM communications. The book features the UCA-based RF point-to-point OAM communication system, the UCA-based RF point-to-multipoint OAM wireless backhaul network, the HCCL structure for long-distance OAM transmissions, and the UCA-based joint OAM RadCom scheme. For the UCA-based RF point-to-point OAM communication system, a 2-D ESPRIT-based distance and AoA estimation method is first introduced, followed by an OAM reception scheme including the hybrid mechanical and electronic beam steering with the estimated AoA and the amplitude detection with the estimated distance. The proposed RF OAM communication scheme is extended to the RF OAM-MIMO system equipped with UCCAs. For the UCA-based RF point-to-multipoint OAM wireless backhaul network, an OAM-based multi-user distance and AoA estimation method is introduced, followed by a multi-user OAM preprocessing scheme. At last, the proposed methods are extended to the downlink multi-user OAM-MIMO wireless backhaul system equipped with UCCAs. Moreover, a novel HCCL structure is introduced to realize long-distance OAM transmission. For the UCA-based joint OAM RadCom scheme, an OAM-based 3-D super-resolution position estimation and rotation velocity detection method is introduced, and then the PCRB of the OAM-based estimates and the transmission rate of the integrated system are derived and analyzed. To achieve the best performance trade-off, the transmitted integrated OAM beams is optimized by means of an exhaustive search method. Finally, this book discusses future research directions to inspire further investigation in the field of RF OAM communications from different perspectives.
About the Author: Rui Chen received the B.S., M.S. and Ph.D. degrees in Communications and Information Systems from Xidian University, Xi'an, China, in 2005, 2007 and 2011, respectively. From 2014 to 2015, he was a visiting scholar at Columbia University in the City of New York. He is currently an associate professor and Ph.D. supervisor in the school of Telecommunications Engineering at Xidian University. He has published about 80 papers in international journals and conferences and held 40 patents. He is a member of the IMT-2030 6G Promotion Group, conduct OAM communication technology development. He is an Associate Editor for International Journal of Electronics, Communications, and Measurement Engineering (IGI Global). His research interests include broadband wireless communication systems, array signal processing and intelligent transportation systems.

Wen-Xuan Long received the B.S. degree (with Highest Hons.) in rail transit signal and control from Dalian Jiaotong University, Dalian, China, in 2017. She is currently pursuing the double Ph.D. degree in information and communication engineering at Xidian University, China, and the University of Pisa, Italy. Her expertise and general interests span the areas of wireless communications and signal processing, estimation and detection theory. Her research interests include the novel transmission dimension of wireless communication networks, including OAM wireless communications, and RIS-aided wireless communications.

Nan Cheng received the Ph.D. degree from the Department of Electrical and Computer Engineering, University of Waterloo in 2016, and B.E. degree and the M.S. degree from the Department of Electronics and Information Engineering, Tongji University, Shanghai, China, in 2009 and 2012, respectively. He worked as a Post-doctoral fellow with the Department of Electrical and Computer Engineering, University of Toronto, from 2017 to 2019. He is currently a professor with State Key Lab. of ISN and with School of Telecommunications Engineering, Xidian University, Shaanxi, China. He has published over 70 journal papers in IEEE Transactions and other top journals. He serves as associate editors for IEEE Transactions on Vehicular Technology, IEEE Open Journal of the Communications Society, and Peer-to-Peer Networking and Applications, and serves/served as guest editors for several journals. His current research focuses on B5G/6G, space-air-ground integrated network, big data in vehicular networks, and self-driving system. His research interests also include AI-driven future networks.