His research interests revolve around wireless propagation channels, wireless systems design, and their interaction. Recently, his main interests have been wireless channel measurement and modeling for 5G and beyond 5G systems, joint communication-caching-computation, hybrid beamforming, UWB/TOA based localization, and novel modulation/multiple access methods. Overall, he has published 5 books (among them the textbook “Wireless Communications”, third edition in 2023), 22 book chapters, 300 journal papers, and 400 conference papers. He is also the inventor of 70 granted (and more than 10 pending) patents, and co-author of some 70 standards contributions. His work has been cited more than 60,000 times, his h-index is >100, and he is a Clarivate Highly Cited Researcher.