Wireless Communications and Applications Above 100 GHz: Opportunities and Challenges for 6G and Beyond

“For all mmWave frequencies where the urban cell sizes are on the order of 200 m, rain or snow attenuation can clearly be overcome with additional antenna gain (obtainable by switching in more antenna array elements) [2], [4], [6].”

“tion [24], personal health monitoring systems [48], precision time/frequency transfer, and wireless synchronization [10], [22], [59].”

“The measured path loss at 140 GHz agrees with Friis FSPL equation [141].”

“tion [24], personal health monitoring systems [48], precision time/frequency transfer, and wireless synchronization [10], [22], [59].”

“For all mmWave frequencies where the urban cell sizes are on the order of 200 m, rain or snow attenuation can clearly be overcome with additional antenna gain (obtainable by switching in more antenna array elements) [2], [4], [6].”

“Current experimental platforms for systems above 100 GHz are mostly channel sounders or physical layer test-beds that rely on off-line processing [3].”

“As customary in mmWave/sub-THz communications, the channel (3) exhibits a sparse scattering characteristic [3].”

“Rural Coverage Direct-to-(GEO/MEO) Satellite Multi-orbit/3D NTN for new features, such as joint communications and sensing [51].”

“After the integration of mmWave into 3GPP specifications, both industry and academia are pushing towards effective deployments, which will solve the sub-6GHz spectrum short-age and deliver multi-gigabit throughputs [1].”

“Communication system application such as autonomous driving, Internet of Things (IOT), health care (remote operation) and high data rate backhaul links, will require data rates which current systems and bandwidths are unable to achieve [2].”

“To avoid an exponential increase of cell costs, a more prevailing approach is needed to take advantage of additional antenna gains using multiple-antenna technology that increases the antenna elements with the carrier frequency while keeping the antenna area the same [10].”

“which humans participate in real time in a movie through brain input and wireless cognition [62] in which a drone or autonomous vehicle is controlled by a brain.”

“…issues, such as the constrained range for transmission due to atmospheric absorption damage, constrained output power due to inadequate power amplifier (PA) efficiency, and mechanisms influenced by the intense phase noise (PN) of high-frequency oscillators, need to be addressed [5], [6], [7].”

“Sub-terahertz (Sub-THz) frequency band is projected as a viable solution to meet the unceasing demand for increasing the data rate of wireless communication systems [1].”

“The mmW frequency band spans from 3 GHz to 300 GHz.”

“The inherent broad bandwidth is an essential resource for large channel capacity for high-speedcommunications [1, 2].”

“…terahertz band of electromagnetic waves demonstrates several attractive characteristics, including non-ionization, fingerprint spectrum, sensitivity to weak resonance, and strong penetration of nonpolar materials, which have promising applications in communication [1], sensing [2], and imaging [3].”

“Nevertheless, these millimeter-scale devices may not have the space or power budget to carry a battery or to conduct massive computations onboard [2].”

“For 6G and beyond for instance, peak data rates of 1 Tbit/s are foreseen [5].”

“I N MODERN communication systems, low-insertion-loss narrowband filters with a wide spurious-free high-rejection stopband are highly desired, especially in sub-THz and THz communication systems, where propagation losses and spectral efficiency play a critical role [1], [2], [3].”

“Restrictions apply. ofteninvolveshighcomputationalcomplexity,makingitimprac- ticalinmMIMO-supportedhigh-frequencyV2Icommunica-tion[12].”

“In particular, D -band (110–170 GHz) is expected to be a promising frequency spectrum for emerging applications due to the feasibility of hardware implementation, low atmospheric absorption, and the availability of wide unlicensed bands offering less congested environments [2].”

“A common approach represents the environment’s reflecting surface as a static virtual anchor (VA) reflecting the base station (BS)’s position [16], [17], [22].”

“The transition to 6G demands higher data rates and channel capacity, requiring the use of higher frequencies, including millimeter-wave (mmWave) and sub-terahertz communications [5], [6].”

“Extremely large aperture arrays (ELAAs) emerge as a promising technology poised to meet the escalating demands for communications and support new applications in 6G and beyond wireless systems [1], [2].”

“More-over, as the wavelength approaches the dimensions of dust and rain particles, the behavior of the sub-THz channel may deviate from what we have understood in conventional low-frequency bands [6].”

“Toaddress this issue, polar-domain representation for the extremely large-scale MIMO (XL-MIMO) channel has been proposed in [8], [9].”

“Therefore, along with the network densification, exploiting new spectrum beyond current sub-6 GHz bands such as Terahertz (THz) and Millimeter Wave(mmWave), the network capacity can be enhanced significantly [3].”

“Finally, it is widely recognized that a strong LOS path is necessary for reliable communication at mmWave and Terahertz frequencies [2], [40], [41].”

“As a result of such high gain antennas, very directional sensing applications become a viable solution to create high-definition images of the surroundings [2].”

“To this end, the next-generation wireless systems adopt communications over extremely high frequency (EHF) bands, such as millimeter-wave (mmWave) spectrum [2] that offers high capacity for short-range connectivity.”

“To sustain the explosively grown data traffic, the Terahertz (THz) band, ranging from 0.1 THz to 10 THz that offers abundant bandwidth resource, is envisioned as a key technology [2], [3].”

“With an important amount of unused spectrum, the subTeraHertz (sub-THz) frequencies between 90 and 300 GHz are contemplated to realize high-data rate wireless communications and hence to fulfill the requirements of the nextgeneration of wireless networks [1].”

“, 5G and 6G) utilize high bandwidths available at millimeter wave (mmWave) and terahertz (THz) frequencies to achieve multiGbps throughputs [1], [2].”

“LOCATION detection and tracking are expected to play more important roles in future wireless communications [1], [2].”

“Applications such as factory automation, gesture recognition, autonomous vehicles, and VR gaming require extremely precise position location on the order of centimeters [8].”

“However, a dedicated-spectrum model is inevitably spectrum-inefficient for the carrier—especially in regions where terrestrial coverage is already adequate—since, due to greater path loss, D2D has much lower spectral efficiency than the terrestrial network.”

“As a promising spectrum band for sixth-generation (6G) communications, the Terahertz (0.1-10 THz) band is anticipated to meet the demand of wireless systems for data rates to reach terabits per second (Tbps) [1]–[3].”

“T HE UTILIZATION of terahertz (THz) technology holds great promise for future wireless communication systems, enabling high-speed data transmission with ultra-high bandwidth and minimal latency [1], [2], [3], [4], [5], [6], [7].”

“Future networks envisage novel applications that extend from holographic communications and wireless cognition, up to real time sensing and precise localization [3], [4].”

“Moreover, bandwidth-intensive and high-data-rate applications, such as wireless cognition, extended reality, and wireless backhaul, all look to potentially use the sub-THz and THz frequencies with multi-GHz wide swaths of bandwidth [18].”

“To support the continued exponential growth of data traffic in wireless networks, the THz band (0.3-10 THz) has attracted considerable attention where untapped frequency resources exist with the prospect of massive data capacity and connectivity [1], [2], [3], [4], [5], [6].”

“…(up to 10 7 devices/km 2 ), persistent availability with high mobility (up to 1000 km/h), low latency (ranging from 25 µs to 1 ms), and enhanced hardware (HW) efficiency within wireless mobile networks, meeting the traffic demands and delivering a ubiquitous experience to the UEs [1,11,12].”

“T HE Terahertz (THz) bands, ranging from 0.1 THz to 10 THz, could provide an abundance of bandwidth and are promising for enabling wireless links with extreme capacity for six-generation (6G) communications and beyond [2], [3].”

“Consequently, in the last decade, the number of research efforts aimed to unleash the potential of the sub-terahertz and terahertz (THz) bands, or broadly, the frequencies between 100 GHz and 10 THz, has exponentially grown [2], [3].”

“Among these advances, millimeter-wave (mm-wave) and Terahertz (THz) frequency bands are key since they can provide abundant spectral resources for data transmission [1].”

“These frequency ranges provide higher bandwidths, enabling the communication systems to efficiently meet the higher data rate demands of emerging applications such as augmented/virtual reality, autonomous vehicles, and smart cities [1], [2], [3].”

“Different from conventional mmWave networks, THz arises potential issues in physical and medium access control layers, including high-frequency channel modeling [16], molecular absorption modeling [17], pencil-beam orientation [18], and power consumption [14].”

“To further increase spectral efficiency, future sixth-generation (6G) communication systems are expected to employ extremely large-scale MIMO (XL-MIMO) antenna arrays [3].”

“3121068 and more channel capacities based on the Shannon–Hartley theorem [1]–[2].”

“In comparison to the microwave spectrum, the THz spectrum is limited in sensing range due to higher atmospheric attenuation, free space path loss, and lower transmit power [9,10].”

“The sixth generation wireless systems will likely to adopt the millimeter-wave (mmWave) massive MIMO technique to provide high data rates through large available bandwidth and highly directional communication [1].”

“having significantly shorter channel coherence times, which require a higher control signaling overhead due to more frequent channel measurements [2].”

“The same integration strategy can also work well for 6G and beyond wireless networks [72].”

“These wireless data traffic demand huge bandwidths that are enabled by millimeter-wave (mm-wave) bands in 5G and beyond [2], [3].”

“Wideband transceivers for emerging 5G/6G wireless networks use large-scale arrays to provide high antenna gain, thus compensating for high path loss [32].”

“S UB-THz frequencies ( > 0.1 THz) are expected to play a critical role in the 6G cellular network, where massive amounts of compact cell arrays support extremely high data rates (up to 1 Tbps) [1].”

“The terahertz (THz) band (0.1 – 10 THz) has been widely researched as a promising spectral resource to augment the millimeter and microwave spectrum currently utilized in fifth-generation (5G) networks for meeting the communication needs of sixth-generation (6G) and beyond networks [1], [2].”

“These wireless communication systems face increasing requirements for higher data rates and more simultaneous users [1].”

“In contrast, millimeter-wave (mmWave) radar technology has gained prominence as a robust alternative, owing to its unique capabilities [12, 13].”

“current 5G wireless systems [1], [2], [3], [4].”

“The statistical properties investigated of channel model usually include PL [38], [39], scattering and reflection attenuation [38], STFC [40], and so on.”

“The Terahertz (THz) band, with frequencies ranging from 0.1 to 10 THz, is envisioned to realize multi-gigabit-per-second or even terabit-per-second data rates owing to the abundant bandwidth resource [1], [2], [3].”

“…GHz] systems present a good tradeoff between mi- crowave’sdeeppenetrationcapabilitiesthroughnonmetallicma-terials and the fine spatial and time resolution of the optical frequency range, resulting in millimeter positioning accuracy [7], [8], while enabling nonline of sight applications [9], [10].”

“Future wireless networks should evolve beyond human-centric wideband demand, to serve billions of devices simultaneously, while concurrently supporting high-throughput machine-to-machine communication applications like chip-to-chip ultra-high-speed communications [1].”

“T HE advent and widespread adoption of fifth-generation ( 5 G) communications have spurred an increased interest in developing next-generation communication technologies, often referred to as sixth-generation ( 6 G) communications [1], [2].”

“…information and channel data are captured from the physical world for environmental sensing and reconstruction, which involves channel measurement (Rappaport et al., 2019; Zhang JH et al., 2020, 2023), environment-channel dataset construction (Cheng et al., 2023; Shen et al., 2023), and…”

“I N ORDER to achieve higher data rates, future wireless communications systems are envisioned to utilize large available bandwidths in the millimeter-wave (mmWave) and sub terahertz regime [1].”

“On the other hand, the sub-THz spectrum offers a largely untapped resource, with significant portions of it allocated as unlicensed spectrum by the Federal Communications Commission (FCC), particularly in the 120 to 170 GHz range [1].”

“While the industry continues to enhance 5G technologies, researchers are shifting their focus toward the next generation of wireless communication, 6G, exploring higher spectrum bandwidths [2].”

“Future wireless systems are expected to utilize large-scale antennas [1], and explore high-frequency bands in the millimeter waves and sub-THz regimes [2].”

“I NTRODUCTION A CCURACY in sub-THz microelectronic measurements [1] becomes important in the development of new applications above 100 GHz [2], [3] as the semiconductor foundries demonstrate new devices and integrated circuits (ICs) with improved performance [4], [5] up to 300 GHz.”

“The THz band is defined as the frequency range from 0.1 to 10 THz [9], [10].”

“These factors necessitate careful consideration in system design and deployment [88].”

“More specifically, although the sub-6 GHz carrier frequencies mainly used for 4G and 5G low/mid bands do not produce significant absorption, reflection and scattering, in terms of their radio propagation characteristics [8], employing 5G high bands (> 20 GHz) and even THz bands (possibly used for 6G and beyond [9]) ca…”

“In this way, an efficient radio access—constructed by accurate channel modelling—combined with more spectrum availability is essential to achieve the ongoing demands faced by wireless carriers [2].”

“A variety of challenges occurred when there was an increasing demand for safer and faster data transmission [1,2].”