Alan Gatherer, Editor-in-Chief
Published: 29 Jun 2018
CTN Issue: June 2018
A note from the editor:
This newsfeed has spent a lot of virtual paper on the topic of 5G over the last year or so but now that the New Radio spec is released and we are beyond the trial stage and approaching deployment, we thought it was time to annoy all of you purists out there and start a discussion on 6G, or “what will 5G leave on the table?”. Before you write your angry letter, please read on, because we are far from the first to ask this question. Your comments, angry or otherwise are most welcome in the comment section below the article.
The Start of 6G: A Survey of Who Is Saying What
Despite the fact that some folks are saying 4G has lots of legs and 5G will only arrive gradually, no big deal, (for full disclosure, my own company Huawei has made such noises ), there are people looking forward to what 6G might hold and how to get there. So what trends are emerging?
Trend 1: More Bits, More Spectrum
Of course the first place people go is to claim that we will get to an order of magnitude more bit rate . The challenge of achieving tens of Gb/s, at least in an aggregated sense to a small region, will depend on finding yet more spectrum (or does it? Will we ever have a new G without a request for more spectrum?). In his 2017 keynote at WCNC  Gerhard Fettweis of TU Dresden pointed towards several bands between100 and 300GHz that showed some promise.
His department has done some testing at these frequencies and they are not alone in this. So maybe we will find the spectrum, but the challenges to achieve true mobility will be even greater than those currently facing mmW for 5G.
Trend 2: Increased Emphasis on Spatial Bandwidth
Several authors have pointed towards an increased integration of satellite communications to enhance bandwidth and also the spatial acuity of the 6G system . Indeed it would seem that going forward it will become critical to measure success in terms of the ability to deliver bits per second per m3 rather than simply bits per second. Of course 5G is already all over the spatial multiplexing angle (if you will pardon the pun) of the problem with massive MIMO technology allowing directing of beams with high accuracy to individual users. But the industry has yet to properly come to grips with how to measure the true benefit of this technology, in our humble opinion, which of course is measured in dollars not dB, leaving many great technologies circling around waiting to be properly motivated for productization. Presumably 6G will arrive with this all sorted out and there will be a new push for technologies that enhance the spatial density of b/s as well as a new appreciation for its value. Indeed there are some efforts to enhance massive MIMO beyond the current state of the art with 6G as their target . Anyway, we predict that there is much left to be done in spatial bandwidth enhancement beyond the current mMIMO offerings, which are, themselves, still struggling to really make an impact.
Trend 3: New Technologies
Antenna technology is seeing a lot of activity right now and there is a strong expectation that antennas in the mW and above will be embedded on chip in handsets and then later in small cell solutions. This made no sense when you have just a few antennas but as we move towards 100s it starts to make a lot of sense. Companies like Metawave  are productizing new materials to replace traditional antennas and give them properties that traditional antennas cannot achieve. Interesting work is also being done on using meta-materials to cloak antennas from each other in certain frequency bands, allowing them to be packed more tightly than would be traditionally possible .
Of course AI is predicted to play a big part in any new standard and one way may be that it allows us to specify even less of what is happening, and just let individual intelligent machines fill in the gaps in our standard. The idea of auto tuning the modem in the field is a new one that may well play a role in 6G . It would be expected that AI will be fully integrated into an intelligent network system in time for 6G, something the University of Oulu calls “distributed intelligent wireless computing” , so that the 6G network may also be defined with an expectation of deep learning. As part of my research for this article I discovered that the IEEE future directions group has already posted some comments on this topic  and that their emphasis is on self learning, autonomous networks that will negotiate the bandwidth they need as applications emerge.
Trend 4: New Applications
Of course the applications being proposed for 6G tend to be 5G proposed applications on steroids. IoT of one kind or another features heavily with one article promoting “telepathy” where your neural implant will talk to my neural implant allowing us to read each other’s thoughts! China, yes the country, recently announced it had started working on 6G using IoT as one of its main drivers . Generally people are betting on smart city and factory 4.0 to drive the bandwidth density. It is possible that 6G will be the first standard of cellular designed primarily for machine to machine communication and this will have a dramatic impact on the requirements for QoS and roaming. Other general application classes we have talked about in previous articles include the Tactile Internet, the Internet of Skills and autonomous vehicles. All of these classes may become first class citizens of the requirement process in 6G in a way that was never true for 5G. It is expected that Virtual Reality will become a must support application by the time 6G begins standardization and this will drive the higher individual data rates more than any other application we know of so far.
It seems clear that 6G is more than just a cocktail party topic now, with some universities finding funding to start to take on the challenge. Of course it looks a lot like an extension of 5G right now. But as new technologies continue to emerge, especially in AI, materials and antenna integration there is room for fundamental improvements that will have an impact on the radio and the network. IoT continues to build and put pressure on the network that may force it beyond 5G. So when will that all happen? Well conventional wisdom says by 2030 but maybe before. Also do not forget the old urban legend that all odd numbered Gs are not so good and need replacing by superior even numbered Gs. In that case 6G may be arriving even sooner!!
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