Learning the Lessons of 5G

December 2, 2020

Written by 6GWorld Contributor
A picture of teaching
CATEGORY: Exclusives

With thanks to author David Pringle, Director, Pringle Media

Industry experts say 6G should follow a very different path to its predecessor  

What can the architects of 6G learn from 5G’s lacklustre debut?  

One of the allegations levelled at 5G is that it is a solution in search of a problem. If that is true, perhaps the very first question that 6G visionaries should ask themselves is: What will 6G be for? 

Whereas 5G was initially defined in terms of its performance parameters, 6G could be defined by the societal problems it is intended to solve. “We are adopting a completely unique and new approach to 6G compared to previous generation systems and that has been decided in collaboration and discussion with our industry members,” Regius Professor Rahim Tafazolli, head of 5G Innovation Centre at the University of Surrey, told the What’s Next for Wireless Infrastructure Summit in November.  “And this unique approach is we start with a clear use case, with a clear business case. We will not set any target KPIs in terms of the speed, latency etc. That will come as the result of research.” Tafazolli is the director of the University of Surrey’s newly launched 6G Innovation Centre (6GIC). 

Indeed, 5G was designed to meet some ambitious performance requirements, such as a peak downlink speed of 20 Gbps (equating to a typical user experience of 100 Mbps), latency of just 1ms in the user plane and support for one million connections per square kilometre. But focusing on these targets may have resulted in 5G neglecting other key attributes, such as support for ubiquitous coverage indoors and in rural areas. 

The performance targets for 5G were designed to support three buckets of use cases – enhanced mobile broadband, ultra-reliable low latency connectivity and mass machine type communications. But in practice, the development of 5G technology is running ahead of the development of use cases beyond mobile broadband, according to Paul Crane, networks research director, applied research at BT, who spoke at the same summit as Tafazolli.  

In a presentation called Beyond 5G: The need for a different approach, Crane argued that it is very difficult for telecoms engineers to envisage today what the practical use cases for 6G will be in 2030. “I think it’s absolutely vital that we work with industry and businesses to really understand what they think they’re going to need in that timeframe,” he added, calling for an inter-disciplinary approach that brings together telecoms, social sciences, material science and industry. 

Enabling a kind of teleportation 

Indeed, the new 6GIC plans to engage with other scientific fields. Tafazolli noted that 6G could build on 5G’s support for 3D augmented reality and virtual reality services by enabling a form of teleportation. As well as delivering 3D images of an object or person, a 6G network could potentially deliver ambient information. “Part of this ambient information is human senses,” which could be simulated by integrating synthetic biology into the communications system, Tafazolli explained. “And if you transmit human senses […] we enable a kind of teleportation.” 

He noted that this kind of use case will depend on 6G supporting full synchronization of the physical and digital worlds – a step beyond the low latency capabilities of 5G. The introduction of synchronisation would need to be supplemented by a reduction in jitter (variations in the time it takes to transmit each packet), Tafazolli believes, noting that “time synchronisation and time jitter [have] never been part of the 5G specification.”  

In theory, at least, robust synchronisation and low jitter would together enable multiple robots to work collaboratively or vehicles to coordinate their movements, as well as enabling people in different locations to interact as smoothly in the virtual world as they do in the physical world. “Imagine that the doctor will be virtually present at your home and he can touch your hands, your forehead or [take your] temperature and provide that real human-like interactions with the patients,” Tafazolli explained. 

Precise synchronisation could also be employed to make far more efficient use of spectrum by enabling different wireless networks to coordinate the sharing of frequency bands in real-time, rather than relying on guard time and guard bands (the buffer zones between different chunks of spectrum). Tafazolli posited that it should be feasible to enable fast spectrum sharing right down to the packet level. 

Support for time synchronisation, ubiquitous coverage and dynamic and real-time geo-location determination could be the cornerstones of 6G, whereas 5G is focused on delivering speed, mass connectivity and reliability/low latency, Tafazolli concluded.   

Filling the gaps left by 5G 

Indeed, 6G could end up filling the gaps left by 5G, just as 2G addressed some of the flaws in 1G and 4G actually fulfilled 3G’s promise of providing mobile broadband. “There were no new services with 4G,” says William Webb, CEO of Webb Search. “It was: let’s sort out 3G by delivering a decent speed, low latency on a fast stable network.  And then 5G is a leap into the unknown again.” He contends that 5G has been developed “on a build it and they will come” premise, adding “maybe they will, maybe they won’t.” 

In his view, one of the biggest issues with the early deployments of 5G is that the technology is often being retrofitted onto existing macro-cells, whereas it was designed to be deployed in much smaller cells. As a result, many of today’s 5G networks are providing very patchy coverage, particularly inside buildings where walls can block radio signals transmitted at higher frequencies.  

“If I sat down with a blank sheet of paper and said what does the perfect communications network look like, I would design something that had in-building cells everywhere because that’s where we spend most of our time…cellular has completely failed to crack in-building,” Webb says. “Get 6G focused on delivering almost entirely superb in-building coverage, allowing people to self-deploy in the way they do Wi-Fi…I would say that was an area that was pretty badly neglected with 5G.” 

Despite the geopolitical pressures, Webb cautions against a rush to develop 6G. “It feels to me like what we are going to end up with is 5G on steroids delivered far too quickly and if 5G turns out to be exactly what we needed, then we will have hit the sweet-spot with 6G,” he says. “But if 5G turns out to be a bit of a miss and then actually we need a course correction, 6G will be too advanced by then to put the brakes on and do something different.” 

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