Any sci-fi aficionado, over 40, and the many younger Trekkies, know the multitude of spun-off series’ and movies spawned from the immortal original Star Trek series. In particular, for this discussion, I am referring to the movie The Search for Spock, from a metaphorical perspective.
I have been writing about 6G for several years now. Many of my ruminations revolve around the hype that is common whenever new telecom, or other technology advances or bubbles up to the surface.
Fortunately, with 6G, so far the hype has not been too terrible. At first, it seemed like it would mushroom. But fortunately, it quieted down relatively quickly and did not reach anywhere near the insane level that was 5G. Maybe the industry has learned a bit, finally, from the 5G debacle. The hype of 5G was so exaggerated it was painful. And, so far, the early hype of 6G has passed. So maybe…
That is not to say that nothing is happening in the 6G space. Much is actually taking place in the labs and think tanks such as at NYU’s Tandon School of Engineering. Periodically, one hears of a lab test or experiment. But few are in what I like to call the serious 6G spectrum (mmWave and THz). They are just extensions of advancing 5G, really.
There are opinions that we will have 6G by 2030, but frankly, I am not convinced. That target comes mainly from those that have the most skin in the game (companies heavily investing, mostly). Of course, it depends on how you define 6G. But 5G is just now reaching critical mass, and it will be a few more years before it goes fully mainstream. So expecting 6G in five years is a reach, IMHO (even taking into account the accelerated pace of technology).
What About mmWave?
For the sub- and THz bands (300 GHz – 1 THz) the work on 6G is still nearly all experimental. There are still far too many issues at these frequencies that need to be conquered. At some point, of course, these challenges will be addressed, and we will have oodles of spectrum to play around with.
But for the next decade, the W band, 75 – 110 GHz, will be front and center because it offers an excellent compromise of available spectrum and can use current RF technologies. Next will be the D band, which spans 110 GHz – 170 GHz, through H band, which spans from 220 GHz – 330 GHz, as technology advances (see Figure 1).
However, even though this introduces much larger bandwidths, realizing radio transceivers across the entire bandwidth is a nearly impossible task. Especially if one wants to maintain sine qua non, or what is essential.
And the real 6G discussion is around the THz spectrum where we are barely scraping the surface. It will be the ultimate enabler for the ubiquitous communications network of tomorrow.
But moving on, 6G will actually have some new and advanced iterations of RF technology and platforms – enough to claim that 6G is truly a generational increment.
Why? The main reason is that 6G will not be a centralized and delineated platform, as were previous Gs. That has significant implications and breaks from all previous generations. Many not in the marketing segment have argued that 5G is really nothing more than the evolution and maturation of 4G platforms and technologies.
What is New?
Things like reconfigurable intelligent surfaces (RIS), are probably the most exciting thing about 6G, plus new extreme coding and transmission schemes – polar, turbo, fountain, spatial, multidimensional index modulation, Generalized Low Density Parity Check Codes, Mode Division Multiplexing, orthogonal time frequency and space, and various other advanced multiple access schemes, combinations of these and more (whew). Plus, new antenna configurations and every device being an access point will radically change the physical network infrastructure.
The base network where device-to-device communications happens will be fully decentralized. And, to fully realize 6G will require that much of it lives the mmWave bands and at low power. And not just up to 10 GHz. Millimeter wave and, ultimately, THz will be the go-to spectrum for near-distance communications.
Of course, current cellular-based communications will continue to exist, obviously, but will assume a more high-level management role.
Two major propositions will define 6G. The first is the network (everything will be an access point). The second is the implementation of new reflective surfaces, (RIS, primarily). We already have conductive paints and films. Similarly, other types of surfaces and coatings are being investigated as radiating media. The goal is to have RIS at scale across all types of surfaces, flexible and inflexible.
The frequencies are not a big deal, since the physics around RF will not change. Notable changes will be in the frequency bands and the related technologies and coding schemes. The sheer volume of every device being RF-enabled will necessitate that frequencies will have to be able to handle much more traffic than current schemes can offer.
Drilling Down on Tech
A while back, I was introduced to a company called Cohere, which developed a unique coding scheme called orthogonal time frequency and space. This was an avant guard technology at the time, but its time has come today. And they continue to impress me with their technologies.
Others are developing various new and advanced iterations of shift-keying, multiple access, and multi-dimensional coding, as well. In addition, there are many more Coheres coming onto the radar screen with coding schemes still in the labs or just being investigated.
Also, let us not forget that AI and software are the new golden children. 6G will be run on them. We still have a bit of a journey before the telecom industry can integrate and optimize these platforms. But make no mistake, advanced iterations of this will be the doctrine for 6G.
Ahh, the RAN
The RAN will have to catch up. Open and virtual RANs have surprised nearly everyone with their “failure to launch.” The great white hope that these would rapidly infuse the transmission infrastructure and accelerate the proliferation of 5G was overestimated. But it will soar once the industry figures out that proprietary RAN is passé in all but a few cases. Once the level of AI and software catches up to what this needs to scale and deploy, it will become prolific. All this is but a glimpse of what is coming down the pike.
When?
Today, 6G is still in the labs. Some like to point to platforms such as non-terrestrial networks (NTN) uncrewed aircraft systems (UAS), high altitude platforms (HAPs), various satellite platforms, adding light to the network as harbingers of what 6G will be. But glimpses of these will play out in 5G long before 6G is ubiquitous.
I just hope that we do not see a trumpet-sounding parade announcing 6G at some point, betting on the come. Rather, as we should have done with 5G is get the technology and base platform out there and working, then use it to build use cases with what it is, not what it can be.
The search for 6G goes on. A quiet environment does not mean a quiet segment. 6G is alive and well, and it is good that we are keeping a cooler head around it. The time will come when 6G will be all it can be. But it will be a few years yet.
