Terahertz Communications and Sensing for 6G and Beyond: A Comprehensive View

The next-generation wireless technologies, commonly referred to as the sixth generation (6G), are envisioned to support extreme communications capacity and in particular disruption in the network sensing capabilities. The terahertz (THz) band is one potential enabler for those due to the enormous unused frequency bands and the high spatial resolution enabled by both short wavelengths and bandwidths. Different from earlier surveys, this paper presents a comprehensive treatment and technology survey on THz communications and sensing in terms of the advantages, applications, propagation characterization, channel modeling, measurement campaigns, antennas, transceiver devices, beamforming, networking, the integration of communications and sensing, and experimental testbeds. Starting from the motivation and use cases, we survey the development and historical perspective of THz communications and sensing with the anticipated 6G requirements. We explore the radio propagation, channel modeling, and measurements for THz band. The transceiver requirements, architectures, technological challenges, and approaches together with means to compensate for the high propagation losses by appropriate antenna and beamforming solutions. We survey also several system technologies required by or beneficial for THz systems. The synergistic design of sensing and communications is explored with depth. Practical trials, demonstrations, and experiments are also summarized. The paper gives a holistic view of the current state of the art and highlights the issues and challenges that are open for further research towards 6G.Comment: 55 pages, 10 figures, 8 tables, submitted to IEEE Communications Surveys & Tutorial

A Prospective Look: Key Enabling Technologies, Applications and Open Research Topics in 6G Networks

The fifth generation (5G) mobile networks are envisaged to enable a plethora of breakthrough advancements in wireless technologies, providing support of a diverse set of services over a single platform. While the deployment of 5G systems is scaling up globally, it is time to look ahead for beyond 5G systems. This is driven by the emerging societal trends, calling for fully automated systems and intelligent services supported by extended reality and haptics communications. To accommodate the stringent requirements of their prospective applications, which are data-driven and defined by extremely low-latency, ultra-reliable, fast and seamless wireless connectivity, research initiatives are currently focusing on a progressive roadmap towards the sixth generation (6G) networks. In this article, we shed light on some of the major enabling technologies for 6G, which are expected to revolutionize the fundamental architectures of cellular networks and provide multiple homogeneous artificial intelligence-empowered services, including distributed communications, control, computing, sensing, and energy, from its core to its end nodes. Particularly, this paper aims to answer several 6G framework related questions: What are the driving forces for the development of 6G? How will the enabling technologies of 6G differ from those in 5G? What kind of applications and interactions will they support which would not be supported by 5G? We address these questions by presenting a profound study of the 6G vision and outlining five of its disruptive technologies, i.e., terahertz communications, programmable metasurfaces, drone-based communications, backscatter communications and tactile internet, as well as their potential applications. Then, by leveraging the state-of-the-art literature surveyed for each technology, we discuss their requirements, key challenges, and open research problems

A prospective look: key enabling technologies, applications and open research topics in 6G networks

The fifth generation (5G) mobile networks are envisaged to enable a plethora of breakthrough advancements in wireless technologies, providing support of a diverse set of services over a single platform. While the deployment of 5G systems is scaling up globally, it is time to look ahead for beyond 5G systems. This is mainly driven by the emerging societal trends, calling for fully automated systems and intelligent services supported by extended reality and haptics communications. To accommodate the stringent requirements of their prospective applications, which are data-driven and defined by extremely low-latency, ultra-reliable, fast and seamless wireless connectivity, research initiatives are currently focusing on a progressive roadmap towards the sixth generation (6G) networks, which are expected to bring transformative changes to this premise. In this article, we shed light on some of the major enabling technologies for 6G, which are expected to revolutionize the fundamental architectures of cellular networks and provide multiple homogeneous artificial intelligence-empowered services, including distributed communications, control, computing, sensing, and energy, from its core to its end nodes. In particular, the present paper aims to answer several 6G framework related questions: What are the driving forces for the development of 6G? How will the enabling technologies of 6G differ from those in 5G? What kind of applications and interactions will they support which would not be supported by 5G? We address these questions by presenting a comprehensive study of the 6G vision and outlining seven of its disruptive technologies, i.e., mmWave communications, terahertz communications, optical wireless communications, programmable metasurfaces, drone-based communications, backscatter communications and tactile internet, as well as their potential applications. Then, by leveraging the state-of-the-art literature surveyed for each technology, we discuss the associated requirements, key challenges, and open research problems. These discussions are thereafter used to open up the horizon for future research directions

THZ RF measurement techniques

Abstract. In this thesis, literature review on available methods, techniques and procedures for terahertz antenna measurement system and terahertz propagation measurement system are reported. The paper presented the terahertz frequency spectrum allocation by FCC, ITU, ETSI and its application in wireless communication system with advantage in obtaining terabits per second data rates. Terahertz antenna parameters are reported and measurement systems for measurement of these chapters are reviewed. Literature of three papers on terahertz antenna measurement system with their respective measurement setup, calibration techniques and measurement procedures are reviewed. An automated antenna measurement system is reviewed with stochastic and systematic measurements and has achieved terahertz antenna s-parameter measurements in far field region at frequency range of 220 GHz to 330 GHz. Another measurement system with single port short-open-load (SOL) calibration technique is reviewed. In this measurement of s-parameter of terahertz antenna is carried out, using receiver horn placed on 3 D positioner, which records the AUT 3D radiation pattern. The third paper reviewed, is a reconfigurable terahertz antenna measurement system, with capabilities of working on large bandwidths, with small change in work bench instrumentation. This setup contains the multiplexing stages for terahertz frequency generation. Beam pattern measurements are conducted at 1.37 THz supporting the simulations and the system stability for reconfigurations. In the later study, terahertz propagation parameters are studied and presented for review of available terahertz propagation measurement systems. Literature review of three papers describing different setup and procedures for terahertz propagation measurement system are reported. The first system with the setup to record path loss in LOS and NLOS links at 260 GHz to 400 GHz is presented. Propagation parameters containing reflections, shadowing is measured. LOS and NLOS channel capacity models are obtained based on data rates in terabits per second for using above 5G wireless communication systems. Another system with office architecture, indoor LOS link, viable for indoor wireless communication applications is reported. Propagation parameters containing power density profile (PDP) are measured and validated for 140 GHz to 220 GHz. A measurement system which reports effect of atmospheric pressure, temperature and humidity is reported in the last. The setup used short, offset-short, load and thru (SOLT) technique for calibration and PDP propagation parameter is measured for 0.5 THz to 0.75 THz. Terahertz antenna and wave propagation measurement system reviewed in the papers are vital for development of terahertz systems in wireless and mobile communication. Further the study can be extended for measurement of terahertz antennas and wave propagation parameters with models of use in wireless hand-held devices, connected devices, mobile backhaul system and more

Multiple Antenna Techniques for Terahertz Nano-Bio Communication

Using higher frequency bands becomes an essential demand resulting from the explosive wireless traffic needs and the spectrum shortage of the currently used bands. This paper presents an overview on the terahertz technology and its application in the area of multi-input multi-output antenna system and in-vivo nano-communication. In addition, it presents a preliminary study on applying multiple input-single output (MISO) antenna technique to investigate the signal propagation and antenna diversity techniques inside the human skin tissues, which is represented by three layers: stratum corneum (SC), epidermis, and dermis layers, in the terahertz (THz) frequency range (0.8-1.2) THz. The spatial antenna diversity is investigated in this study to understand MISO system performance for two different in-vivo channels resulting from the signal propagation between two transmitting antennas, located at the dermis layer, and one receiving antenna, located at epidermis layer. Three techniques are investigated: selection combining (SC), equal-gain combing (EGC), and maximum-ratio combining (MRC). The initial study indicates that using multiple antenna technique with THz might be not useful for in-vivo nano-communication