To Five? Or Six To Fore?

Posted on Sunday, April 28, 2019

I am writing this while flying back from the 6th Brooklyn 5G Summit, with emphasis on the ‘5G’ even though the conference leaders wanted to talk about 6G.

If some of you have started rolling your eyes, I can fully understand. At the opening cocktail party, before the conference started, I said to someone “I am trying to avoid saying the phrase ‘6G’.” only to discover that was what he was working on. Sorry.

At the kickoff, Nokia Bell Labs President, Marcus Weldon, and NYU Wireless head, Ted Rappaport riffed off the concept that this was start of the 6G cycle, although Marcus estimated that the gap between “G’s” is normally 15 years. Ten is probably closer to the truth (especially in Latin America) but I (at least) appreciated his effort to calm our nerves over talking about 6G too soon.

The Brooklyn 5G Summit is, fundamentally, an academic conference. While Nokia is the lead sponsor and a key organizer, and Ericsson and Huawei participate, the summit is held on the NYU Tandon School of Engineering campus and Rappaport is clearly the leader of conference and its agenda.

Thus, the point of view that the academic / theoretical issues with 5G have been (largely) resolved. Researchers are turning their attention to what comes next.

Should have tried to do some more

One of the drivers of 6G talk is the recognition that there were things in the original design of 5G that not only did not make it into 3GPP Release 15 but will not be in Release 17, expected sometime in the first half of the next decade.

A panel discussion with the three major equipment vendors and members of the academic community admitted that, with the timelines fixed independently of the amount of work or the resources available, those setting standards simply ran out of time. Remember that Release 15 was brought forward so that the South Koreans would have something for last year’s Winter Olympics. Release 16 is somewhere between three months and six months late (depending on who you ask or how you measure the original commitment) so it is likely to leave some stuff behind in the interests of time as well.

We do not yet have 1 ms latency, nor it appears will we have it even in Release 17. I guess that was a ‘stretch target’ although it got lots of airplay when we started talking 5G. Both Release 16 and 17 are planning Network Slicing Advanced, Massive MIMO Advanced and Massive IoT Advanced, meaning that the Release 15 versions of these are (by implication) basic and not delivering the expectation.

However, to be fair to all concerned, one speaker admitted that the ‘deficiencies’ in Release 15 were less a matter of work not getting done as they were ‘victims’ of overly hyped expectations. 5G’s advocates promised everything that this generation will ever be. We all just (naively) thought that the stuff they were talking about would be in Release 15. That never happened in the past and it was foolish to think it would happen this time.

Searching for something to say

That said, the speakers found it difficult to be concrete about what the research program for 6G might include.

Remember the eMBB-URLLC-Massive IoT triangle we used to explain 5G? Marcus Weldon introduced a new “triangle of truth” positing that 6G would integrate Hardware, Software and “Wetware” or the biological sphere. Sounded vaguely like the Borg to me.

Ted Rappaport and his collaborator Gerhard Fettweis were sure that 6G would involve ‘Teraherz Communications’, that is, the band from 300 to 1,000 GHz. The capacity of such a system would be amazing obviously but either cell radii would be measured in meters (centimeters?) or the power would be so high that you could to cook your lunch by putting your phone next to it, so I think there are more that a few research problems to be worked on.

One solution is Even More Massive MIMO (EMMMIMOTM Mirador Communicaciones SAS) so maybe it is time to revive the ‘porcupine phone’ idea I posited a few years ago.

All agreed that there was a wide scope for further research and that 3GPP would continue to churn out new releases every few years. Somewhere in this sequence some marketing person will decide to label the release 6G (for AT&T 7GE) and we will be in a new generation. Maybe Marcus was indeed thinking of the Borg: resistance is futile.

Despite the emphasis on higher and higher frequency bands to achieve higher and higher bandwidth albeit in smaller and smaller cells or higher and higher cell density, no one I spoke to expected there to be a new air interface in 6G (there was not one in 5G after all) or even a new frame structure (the new one for 5G was thought to have all the flexibility needed).

Rather 6G (and 7G and 8G) were likely to be architectural improvements of the end-to-end system with innovations in edge computing, cloud etc.

Giving up I close my eyes

As I said in the cocktail party, my best strategy is to ignore 6G. If Marcus is right, it may not come for a decade or so, and I am so old already that I may never confront the upgrade decision.

There was lots of content at the summit that was purely 5G including the posters and demos. Release 16 may be well advanced but there is still much work to complete Release 17. The marketeers may decide Release 18 is 6G but I doubt those working on it would agree.

NYU Wireless may decide that next year’s conference is the first ‘Brooklyn 6G Summit’ but I will still attend (if invited). There will be a lot to learn and, I expect, most of the content will be 5G-related.

6G may be coming to the fore, but there is still much work to get to 5G.

Title Reference: “To Five or Six to Fore?” or in numerals “2 5 or 6 to 4?” or, getting rid of a space and the question mark, “25 or 6 to 4” Chicago’s enigmatic hit from 1969. It got to number 7 in the UK, number 4 in the US and number 2 in Canada. It is another song that I clearly recall when and where I heard it the first time: a hot July night at my aunt’s cottage on Lovesick Lake north of Peterborough, Ontario. It might have been on the local radio station, although that had a very weak signal and so more likely via WOWO, Fort Wayne, Indiana bouncing off the ionosphere, a phenomenon known (apparently) as “skywave radiation”. The lyrics, while not gibberish by any means, are hard to make coherent and the official explanation – it is about writing a song in the early morning, at 25 or 26 minutes before 4am – is frankly unconvincing even if that is what the songwriter himself says. For a long time, I thought the title was “25 or 6-2-4” which made no sense whatsoever.

25 or 6 to 4 Songwriter Robert Lamm © Spirit Music Group, BMG Rights Management

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