Communications Systems Sotirios K. Goudos and Mohammad Abdul Matin 10.1 Introduction The future 6G wireless communication will expand the 5G capabilities even further. Specifically, 6G is expected to have higher bitrates (up to Tbps) and lower latency (less than 1ms) [26]. Such capabilities will enable the introduction of new services and applications. These services may include ultra-massive machine-type commu- nications, holographic telepresence, wellness and e-health applications, pervasive connectivity in smart environments, pervasive edge intelligence, extremely reliable low-latency communications, augmented reality (AR), and virtual reality (VR) [7]. These services will need more efficient and effective wireless communications than ever before. Thus, 6G wireless communication systems should deliver broadband, near-instant, and dependable communication to enable huge data transmission at many frequencies, as well as a wide range of technologies. Such increased data rates demand and the fact that the spectral efficiency of the 5G wireless links is approaching its fundamental limits motivate researchers to explore and exploit higher-frequency bands. Hence, wireless communications in the terahertz (THz) band is considered to be an attractive candidate for 6G wireless networks. THz communications have the potential to provide an order of magnitude capacity improvements [2]. These 6G networks will outperform 5G in terms of latency and speed, and they will satisfy the above described emerging applications and services. S. K. Goudos ELEDIA@AUTH, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece e-mail: sgoudo@physics.auth.gr M. A. Matin (X) Department of Electrical and Computer Engineering, North South University, Dhaka, Bangladesh e-mail: mohammad.matin@northsouth.edu © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 M. A. Matin (ed.), A Glimpse Beyond 5G in Wireless Networks, Signals and Communication Technology, https://doi.org/10.1007/978-3-031-13786