Introduction:

In July 2015, ITU-R published Report M-2376: Technical feasibility of IMT in bands above 6 GHz  Since then, there has been academic and industry research and development ongoing related to suitability of mobile broadband systems in frequency bands above 100GHz.  As a result, a new ITU-R Report ITU-R M.[IMT.ABOVE 100 GHz] was started at the August 2021 meeting of ITU-R WP5D (#38) to study the technical feasibility of IMT in bands above 100 GHz.  That report will be a complement to the previous studies documented in Report M-2376.

Discussion:

Compared with the 3GPP 5G NR FR2 frequency band (24250 MHz – 52600 MHz), the terahertz frequency band above 100 GHz can provide a larger usable bandwidth, but it also suffers from greater path loss/signal attenuation. Fortunately, it is possible to overcome certain path attenuation by improving the directivity and gain of the antenna and using beamforming technology to increase the coverage of the cell. IMT technologies adopted for bands above 100 GHz can be used in indoor/outdoor hotspot environments, integrated sensing and communication and ultra-short-range environments to provide ultra-high data rate services.

Some possible use cases for IMT above 100 GHZ are:

Indoor hotspot in an large meeting room – small cell base stations operating at bands above 100 GHz may solve the needs of applications with extremely high data rates, such as Holographic displays. Considering the large path attenuation of bands above 100GHz, high-gain directional antennas or large-scale antenna arrays that can provide higher gains could be used to flexibly establish wireless fronthaul /backhaul links with outdoor base stations or core networks.

Integrated sensing and communication – A typical use case is the use of sensing technology to assist communication, such as using sensing technology to predict the user’s trajectory to assist the base station in beam tracking of the user, or using sensing technology to sense the user’s location for rapid beamforming.  Using bands above 100 GHz can achieve better imaging and achieve higher positioning accuracy.

Secure Imaging and Infrared Thermal Cameras are other potential use cases depicted below:

In preparation for a contribution on this topic for the October 2021 WP5D meeting, the Republic of China conducted channel measurement campaigns in indoor scenarios at 140 GHz and 220 GHz. The measured indoor scenarios include a meeting room, and office area, and hallway in office room.  Pathloss models for the investigated bands were derived based on the channel measurement campaigns conducted in a meeting room and an office room and presented in their contribution.

Reference 4. notes recent regulatory and standard body rulings that are anticipating wireless products and services above 100 GHz and illustrates the viability of wireless cognition, hyper-accurate position location, sensing, and imaging. It also presents approaches and results that show how long distance mobile communications will be supported to above 800 GHz since the antenna gains are able to overcome air-induced attenuation, and present methods that reduce the computational complexity and simplify the signal processing used in adaptive antenna arrays, by exploiting the Special Theory of Relativity to create a cone of silence in over-sampled antenna arrays that improve performance for digital phased array antennas.

References:

1. W. Tong, P. Zhu, “6G: The Next Horizon, From Connected People and Things to Connected Intelligence”, Cambridge University Press, 2021.
2. 5GCM, “5G channel model for bands up to 100 GHz,” Tech. Rep., Sep. 2016, Available online at http://www.5gworkshops.com/5GCM.html.
3. 3GPP TR 38.901, “Study on channel model for frequencies from 0.5 to 100 GHz,” v. 16.1.0, Dec. 2019. [4]. ITU-R M.2412, “Guidelines for evaluation of radio interface technologies for IMT-2020,” Sep. 2017.
4. Wireless Communications and Applications Above 100 GHz: Opportunities and Challenges for 6G and Beyond.  IEEE Xplore