• The Telecom Regulatory Authority of India (TRAI) has been looking at the potential use of Terahertz (THz) spectrum bands
• It is recommending that such spectrum should be made available now for ‘experimentation’ 
• The technology needed for THz transmission might be ready for the 6G era 

India might still only be in the initial throes of its love affair with 5G, but that isn’t stopping the country’s ambitious administration looking ahead at how the next generation of wireless services might be developed and delivered. 

Like many agencies around the world, the Telecom Regulatory Authority of India (TRAI) has decided it’s time to tackle the next spectrum frontier – the Teraherz (THz) block sitting above today’s telecom-usable 3 Hz–100 GHz band, but below the 3 THz point where radio spectrum turns into infrared light and lasers come out to play.

According to India’s regulator, this vast but currently relatively inaccessible chunk of spectral real estate may not be viable right now, but the supporting technology is in development, with India’s telecom regulator calculating that TeraHertz transmission may even be developed in time to play a role in the 6G era.

In a recent report on its prospects, the TRAI points out that talk of imminent Terahertz systems “is no longer far-fetched due to the advancements in optical, electronic, and plasmonic transceiver design”, and, unlike millimeter-wave (mmWave) communications, Terahertz-ready tech can enable short-range Tbit/s connectivity without using additional spectral efficiency enhancement techniques.

Also, due to shorter wavelengths, the systems could “support higher link directionality, be less susceptible to free-space diffraction and inter-antenna interference, operate on much smaller footprints, and possess a higher resilience to eavesdropping.”

But while the band offers much, it has its catches. Most of all, high propagation losses and power limitations mean signals only carry over very short distances.  

Even so, the TRAI reckons it’s likely to play a “pivotal role” in 6G transmission and it wants India’s fast emerging telecom ecosystem to be well positioned to take its share of the global market as and when technologies for high bandwidth connectivity, along with the imaging and sensing applications using the THz band, are developed. And let’s not forget that India is very keen to be at the forefront of 6G developments – see India eyes global leadership role in 6G.

To get the ball rolling it has recommended that India’s government should open up spectrum in the 95GHz to 3THz range for experimentation and R&D, providing there’s no interference to existing services and provide Tera Hertz Experimental Authorisation (THEA) to those wanting to engage in tests and trials. 

TRAI recommends that the “scope of THEA should be to conduct R&D, indoor and outdoor testing, technology trial, experimentation, and demonstration in the 95 GHz to 3 THz range; and to market experimental devices designed to operate in the 95 GHz to 3 THz range via direct sale.” It also suggests that “any Indian entity (Academic institute, R&D Laboratory, Central/ State Government, public sector unit, Union Territory, Technology Park, telecommunication service provider, incubator, original equipment manufacturer etc.) should be eligible to obtain THEA.” 

However, given the immensity of the research task and the now fast-approaching 6G timescale, it seems unlikely that THz technology will be on hand to meaningfully plump up transmission requirements for the first phase of 6G deployments. And even if it is, as things stand with an apparent plateauing of broadband access growth, leading/bleeding radio access network investments probably won’t be at the top of many telcos’ shopping lists.

– Ian Scales, Contributing Editor, TelecomTV