Phone systems change every ten years. 5G communications is now rolling out worldwide. It is time to plan 6G communications for 2030!

The race is on

In fact, work began in earnest on 6G communications in 2020 with over one billion dollars committed and a Chinese satellite sent up to experiment on the possibilities. Finland, Korea, and China are particularly active in researching the terahertz electronics that will be at the heart of 6G, but there is excellent work in India and elsewhere. Backing Finland and its partners are over $350 million of new European Union research grants, so this is serious. Although little is decided - not even the frequency - much can be said about the extremely ambitious 6G objectives and challenges. This article gives the IDTechEx appraisal of 6G communications 2021-2041.

Far better than 5G

5G serves far more than the needs of mobile phones or even personal electronics in general. This will be even more true of 6G, with thing-to-thing communication possibly being more important than human communication. There are more things than people in the world!

The future of everything?

At a minimum, the basic specifications will embrace the needs of sensing, positioning, edge computing, highest definition imaging, and yes, communication. To a human, the 6G response time will appear to be instant. For the first time, there will be no cell-to-cell handover for mobile devices. No more suffering the loss of service at cell-to-cell handover.

Massive improvements

To serve the very ambitious 6G objectives, six parameters are the main focus:

• First truly 3D coverage and ubiquity. 10k meters above, in space, underwater.
• Data rate over 100 Gbps, X100 capacity.
• Accommodates edge devices with no power, low power, low cost.
• Always low latency/ speed of response <1ms.
• Reliability 99.99999%. Secure, private, safe, resilient.
• Massive connectivity 10M devices/ sq. km.

Leaping into the "Terahertz Gap"

Key parameters of 6G will be at least ten times better than 5G, largely because the frequency will be at least ten times higher. That means in the unallotted terahertz band of 275GHz to 10THz, also known as far infrared. This is the Wild West cowboy territory of physics, where few components exist and signals generated are weak as yet. They call it the "Terahertz Gap".

For this reason, initial experiments are often taking place at the easier end - 100-300GHz. The FCC has proposed formalizing this "experimenter's play area" in some bands between 116 and 246GHz. 6G rollout may, like 5G, start at a relatively easy frequency (275GHz?) and later migrate to a challenging higher frequency (1THz) for most benefits. (5G started at a few GHz and is migrating to tens of GHz).

That upper, ultimate THz frequency is unlikely to be higher than 1THz because, just after that, atmospheric attenuation of the beam jumps up to severe levels, and components also become extremely challenging.

For very near and very far

In fact, the THz frequencies will be used at local level and between satellites, the rest being Free Space Optical (FSO) in most cases because laying fiber optics will be too expensive or impractical. There may be some C band GHz long-distance links as well.

Problems that are business opportunities

Problems that are opportunities include:

• Terahertz waves (THz) are located between microwaves and infrared in the light frequency spectrum, but due to their low energy, scientists have been unable to harness their potential.
• Front end and modem chips for the higher frequencies. In contention are GaAs, GaN, InP, SiGe, fully depleted silicon on insulator (FD-SOI) CMOS.
• Fronthaul/ backhaul: High-capacity connectivity and high-altitude solar drones aloft for 5 years on sunshine alone. China, Germany/ France, the UK, and the USA have experimental ones aloft already for weeks not 5 years. Some will be unmanned airships, the leading one ThalesAlenia Stratobus of France/Italy rolls to follow the sun with its topside solar fabric, launching in 2021. Also needed are the tens of thousands of low earth orbit LEO satellites being deployed by the Europeans and SpaceX in the USA. None of these aircraft and satellites are dedicated exclusively to 6G, but they are essential to 6G.
• Heterogeneous hardware restraints on the complex integration into a single platform
• Edge-of-network device capability to realize the benefits
• Complex resource management of 3D networks
• Spectrum and interference management
• THz atmospheric absorption
• THz beam management
• Physical layer security
• THz modeling
• Cost control

A bridge too far?

There are counter-arguments to all this 6G enthusiasm. Some say 5G is proving so expensive it may never be fully deployed. They suggest that those needing more will get it from a higher frequency version of 5G with no more standards needed. IDTechEx notes that 6G cannot happen without something that does not exist and may never be affordable. It is needed because THz beams are narrow, weak, and do not go round corners. Almost anything stops them, so you need smart surfaces even in your private house to provide access everywhere. There are many names for these smart surfaces. "Hypersurfaces", "Intelligent Reflective Surfaces IRS", "Software-programmable metasurfaces SPM". They consist of active THz components and metamaterials in arrays of separately-programmable "tiles". These must redirect, amplify, collimate, polarise, and otherwise manipulate those THz beams.

More criticism

The world tends to solve its problems with less infrastructure. For example, no more telephone exchanges or parking meters. 6G runs counter to this because it needs a huge amount of infrastructure.

They say 6G will at last permit billions of things-cooperating-with-things, all directly connected to the internet. This is the basic concept of the Internet of Things. Well maybe. They say 6G is the future of mixed and virtual reality, medical imaging, and robot vehicles but let us consider that last one. Tesla develops autonomous vehicles that work without mapping or connectivity. It does not need 6G for that.

Can we forecast anything yet?

So how do we forecast at this very early stage? IDTechEx suggests that, for mobile phones, you take the IDTechEx 5G forecast and move the dates forward by eleven years. The overlap of 5G and 6G functionality will be considerable - at least seven years.

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