Terahertz Wireless Communications: Recent Developments Including a Prototype System for Short-Range Data Downloading

Abstract

"owadays, it is hard to imagine daily life without connecting to cellular communications or wireless local area networks. People are not just accessing digital information in real time but also watching movies and enjoying multimedia data streaming services even in vehicles traveling at high speeds. Technically, contemporary wireless communications systems rely primarily on massive signal processing for orthogonal frequency division multiplexing and channel estimation/calibration, which has resulted in dramatically enhanced spectral efficiency and channel reliability. As society evolves toward a more data- and network-oriented world, data consumers and providers are seeking more advanced communications systems that offer larger data capacity. Therefore, a top priority is to find ways to overcome the limits on capacity due to narrow bandwidths. It is not easy to define the target throughput that should be accommodated in the next decade, but considering the new radio 5G cellular system offering up to 10 Gb/s, the huge spectral resources provided by submillimeter or terahertz (THz) wavebands are attracting a great deal of attention from research communities for future wireless communications systems [1], [2]. THz waves (in which I include submillimeter-wave frequencies above 100 GHz in this article) have not yet been used in commercial communications applications [3]. This is because signal sources and receivers at these frequencies have not been available, and the huge spectral spaces have, therefore, remained out of consideration for communications system engineers. Recent progress in semiconductor device technologies [4], however, has finally enabled us to think about THz communications and terabit throughput. Though we are still obviously at an early stage, meaningful and important trials and efforts have been made worldwide, many of which have clarified the future research directions and the challenges of THz communications. This article first overviews several developments in THz communications and then takes a look inside the first THz communications prototype system for short-range, instant data downloading from a standard fiber-optic network to a compact handset. Finally, it discusses some of the technical questions that have arisen from prior studies. ? 2021 Institute of Electrical and Electronics Engineers Inc.. All rights reserved.