Japanese telecom giant NTT, its DoCoMo wireless division, and vendor partners NEC and Fujitsu have developed a wireless device targeted at supporting the extremely high-band spectrum expected to power 6G networks and use cases.

The jointly developed wireless receiver and transmitter produced speeds as high as 100 Gb/s using the 100 GHz and 300 GHz sub-terahertz (THz) spectrum bands. Those speeds were transmitted at distances up to 100 meters.

NTT worked on developing the equipment used for the 300 GHz spectrum band test, while DoCoMo worked on the 100 GHz equipment. NEC developed a multi-element active phased array antenna that used more than 100 antenna elements in support of the 100 GHz equipment, with Fujitsu developing a high-output amplifier to support both spectrum bands used in the tests.

The work is geared toward overcoming immense challenges in using high frequency bands in support of bandwidth intensive applications expected to drive the development, deployment, use and monetization of 6G networks.

NTT has been at the forefront of this 6G work. It previously conducted trials with Nokia, NEC and Fujitsu on using artificial intelligence (AI)-native air interfaces, distributed multiple-input/multiple-output (MIMO) antenna technology and orbital angular momentum (OAM) multiplexing transmission technology. It more recently worked with Nokia to integrate AI and machine learning into the radio air interface to allow a 6G radio to work through signal degradation issues, which reduced signaling overhead and supported a 30% improvement in signal throughput.

NTT and Nokia as part of their work noted that the combination of smarter radio transmission capabilities and the THz spectrum are “well-suited for high-accuracy radio sensing, which will likely be another key feature of 6G.”

Sub-THz spectrum resides above 100 GHz and is viewed as a high-capacity band for 6G use cases due to the abundant amount of available spectrum. However, there is an abundance of that spectrum available because of the very limited propagation characteristics of that spectrum, highlighted by the 100-meter transmission distance noted by NTT’s latest efforts.

“Terahertz signals face severe limitations in how far they can travel due to substantial absorption in the air,” Yu-Han Chang, senior technology analyst at IDTechEx, wrote in a recent report. “This makes addressing signal decaying and establishing strong communication over reasonable distances a top priority for 6G. Likewise, the higher frequency nature of terahertz signals makes them highly sensitive to obstacles in their direct path, such as buildings, trees and other objects. Handling these two challenges is crucial, especially in busy urban areas, where ensuring consistent connectivity despite barriers is a significant undertaking.”

Jeff Wang, global 5G and networks lead at Accenture, noted in an interview with SDxCentral that those higher spectrum bands are also going to force a complete re-think of deployment models to take into account their more challenging propagation characteristics. He added that this level of innovation and creativity is going to be critical to squeeze value from high-band spectrum resources.

“If you put that much stress on any process you have to be able to build in a new level of automation, a new level of intelligence, a new level of rigor to this and if you even let your mind go toward sub-terahertz [spectrum], it’s very hard to imagine,” Wang said. “If we don’t figure this out now, how we bring intelligence in, how we automate this, how we self-heal this, it’s just an unmanageable, logistical nightmare.”