Millimeter-wave and Terahertz Spectrum for 6G Wireless

Abstract

With the standardization of 5G, commercial millimeter wave (mmWave) communications has become a reality despite all the concerns about the unfavorable propagation characteristics of these frequencies. Even though the 5G systems are still being rolled out, it is argued that their gigabits per second rates may fall short in supporting many emerging applications, such as 3D gaming and extended reality. Such applications will require several hundreds of gigabits per second to several terabits per second data rates with low latency and high reliability, which are expected to be the design goals of the next generation 6G communications systems. Given the potential of terahertz (THz) communications systems to provide such data rates over short distances, they are widely regarded to be the next frontier for the wireless communications research. The primary goal of this chapter is to equip readers with sufficient background about the mmWave and THz bands so that they are able to both appreciate the necessity of using these bands for commercial communications in the current wireless landscape and to reason the key design considerations for the communications systems operating in these bands. Towards this goal, this chapter provides a unified treatment of these bands with particular emphasis on their propagation characteristics, channel models, design and implementation considerations, and potential applications to 6G wireless. A brief summary of the current standardization activities related to the use of these bands for commercial communications applications is also provided.

Conformal Metasurfaces: a Novel Solution for Vehicular Communications

“…where ϑ denotes any of the angles in (7). The reflection matrix Φ at the C-IRS in ( 4) is diagonal with entries defined as…”

“…In recent years, 3GPP has proposed the use of millimeter-wave (mmWave) frequencies (30−100 GHz) in the next release 17 [4], [5] for V2X communications, while sub-THz frequencies (> 100 GHz) are being considered for the upcoming 6G systems [6], [7]. The propagation at these frequencies presents several technological challenges.…”

Multi-UE Multi-AP Beam Alignment in User-Centric Cell-Free Massive MIMO Systems Operating at mmWave

“…One way of achieving this is through the use of non-overlapping subcarriers for the parallel data-streams. Denoting by Q the number of subcarriers assigned to each AP RF chain 2…”

“…. , √ βe ı φ (S) T , and 2 Letting Q > 1 permits sounding the channel at multiple frequency locations, and is expected to lead to improved BA capability. fulfills the relation φ H φ = Sβδ( − ), with β > 0 the power transmitted by the APs in each beacon-slot and on each subcarrier.…”

“…The use of millimeter wave (mmWave) carrier frequencies is one of the main pillars of current and future cellular wireless system [1], [2]. Indeed, the large bandwidths available at mmWave can greatly contribute to provide the huge data rates that are requested to implement current and future ultrabroadband mobile services.…”