Two dozen operators and equipment providers are mounting a power-grab for a crucial portion of the 6GHz spectrum now dedicated to Wi-Fi...
One of the key themes in the mobile communications sector over the coming year will focus on whether cellular or Wi-Fi would — should — dominate access to the mid-band 6 GHz spectrum.
The issue has already been a long-running bone of contention between those who consider that 5G (or more specifically 5G New Radio) should be allocated the important frequencies so that users can gain the full benefits of the next generation of cellular, and those who have assumed that the issue had already been settled in favor of the providers of unlicensed Wi-Fi networks.
Late December, a group of 23 operators and cellular infrastructure providers, cheer-led by the GSMA, made what amounts to a power-grab for the crucial 5925 MHz to 7125 MHz portion of the 6GHz spectrum.
The group made their pre-emptive strike following a webinar dubbed “The 6 GHz IMT Opportunity for Society” that was organized by predominantly Latin-American companies. (IMT is the ITU nomenclature for all things cellular).
The group includes many of the usual suspects: Ericsson , Nokia , Huawei and ZTE on the equipment front , and operators such as Orange, Telefonica, Telia and most of the Chinese carriers.
Notable exceptions in the latter group are, for example, AT&T, Verizon and the UK’s BT, and, within the equipment providers’ front, companies such as Samsung and NEC, and less surprisingly so, any of the cheer-leaders for the Open RAN.
The group stressed that the spectrum already allocated for 5G would not be sufficient for future needs and pleaded that “more and larger contiguous channels in the mid-band range will be required by operators for cost-effective future IMT deployments.”
The majority of commercial 5G deployments to date work on the 3.3GHz-3.8GHz mid-bands, while some countries have also re-farmed sub-1GHz low-bands. In a few regions, notably the US and Japan, so far the emphasis has been on millimeter wave (mmWave). While this can offer broad 5G coverage, carriers will clearly need to move up into the higher radio frequency ranges to provide the high capacities and data speeds needed for some of the new use-cases being discussed.
Of course, the proponents of Wi-Fi have used similar arguments as regards their need for the higher frequencies. And they can also make their case for the societal benefits, which, arguably, is an even stronger case since they use and offer the scarce radio frequencies on an unlicensed basis.
Indeed they argue that the frequencies in question are regarded as classic indoor spectrum, which is generally unsuitable for penetrating walls.
Importantly, the group also stressed after the webinar that the ITU has already started preparations for the agenda to be debated at the next World Radiocommunications Conference (WRC), scheduled for 2023.
The post-webinar statement specifically called on regulators in the Latin American and Caribbean countries to consider their position as regards the 6425-7125 bands at the WRC-23.
Delegates are scheduled to debate the feasibility of using these frequencies for 5G, and preparatory work is already under way; for instance technical parameters and channel modelling are targeted to be completed by the middle of 2022.
The group also notes that regional approaches by regulators into the allocation of these important bands differ substantially at the moment, but maintains “all regions can benefit from IMT identification.”
Indeed regulators in Brazil and Argentina, as well as some other Latin American countries have already started consultations about the use of 6GHz for Wi-Fi.
In the US, earlier this year, the FCC proposed draft rules that would see parts of the 6GHz spectrum allocated for Wi-Fi use and in Europe the CEPT (European Conference of Postal and Telecommunications Administrations) has allocated the lower segment of the 6GHz –5925MHz to 6425MHz —for licence-exempt Wi-Fi as from late 2021.
The organization is currently considering its options for the upper 6425-7125MHz band.
All this begs the question of why this lobby group has been formed now. Is it not too little, too late?
Claus Hetting, CEO of Wi-Fi NOW, is certainly baffled by the timing. “This debate regarding the 6GHz frequencies has been ongoing for two to three years. So I must say the whole initiative did surprise me, and particularly the timing. If they (the cellular industry) wanted to make their case, they should have done something like this long ago, and certainly before the decisions of enlightened regulators such as the FCC and the UK’s Ofcom,” Hetting told EE Times. Ofcom proposed in January 2020 plans to make 500MHz of the 6GHz band available for Wi-Fi 6 and 6E.
“In fact I thought they already ditched their plans a while ago,” he added.
Hetting is also skeptical that the issue could be discussed at the WRC-23 conference. “I was under the impression the agenda for that has pretty much been settled. If I am right, are we really going to have to wait for a final decision until after WRC-27?”
More likely, he believes, the initiative’s aims are to delay the crucial unlicensed band allocations decisions. Such a strategy, if successful, could mean big swathes of the 6GHz spectrum not being used to their full potential for almost another decade, he suggested.
Not surprisingly, Hetting suggests that to achieve maximum efficiency, the upper bands should be allocated for unlicensed Wi-Fi use as soon as possible. “But unfortunately the decisions on this are still pending.”
Hetting is adamant that Wi-Fi is the perfect choice for extracting maximum value from the 6 GHz spectrum.
The opposing viewpoint is expertly argued in a recent blog by Brett Tarnutzer, Head of Spectrum at industry body the GSMA, that focuses on both the technical and user benefit issues.
Tarnutzer notes that 5G’s case for licensed 6 GHz spectrum is not just about the balance between forms of connectivity. “It is also about our certainty in predicting the future of how we use spectrum. Countries that allow unlicensed use throughout the 6 GHz will find it difficult to reverse the decision easily as devices proliferate, ubiquitously, throughout territories. In some countries — and certainly in Europe — 5G expansion opportunities do not exist elsewhere.”
He also argues that in certain regions, the lower part of the band (5925 MHz to 56425 MHz) may become available for technologies including 5G NR-U and Wi-Fi. But then, he maintains, the reach of the fiber footprint may dictate how far Wi-Fi is used.
Tarnutzer also stresses it will be important to consider the issue of backhaul as well when it comes to deciding how to maximize 6 GHz usage.
Perhaps the key that could unlock these opposing strands is finding and executing the optimum way for coexistence between the two. Hetting said there have been numerous studies into achieving this, in many regions, and a lot of the work is still on-going.
“What is clear now is that Wi-Fi services can peacefully coexist with incumbent satellite and point-to-point microwave links in the same band. Studies in the US and elsewhere have already shown that it can already work in this instance, so why not between Wi-Fi and 5G?”
In general, two techniques are used for non-interfering coexistence of multiple users within the same band. One focuses on keeping indoor power low enough so that unlicensed signals are unable to bleed to the outside where they could trigger interference.
The second relies on database-look-up type schemes that can be applied to avoid co-location where outdoor (standard power) Wi-Fi signals could seriously interfere with incumbent users.
“In the US, the method adopted by the FCC has been proven to work and is the right one,” said Hetting. The scheme is reliant on AFC (Automated Frequency Coordination), and is a sophisticated version of a database look-up scheme.
Fortunately for the 6 GHz band, and for Wi-Fi, incumbent 6 GHz users are generally fixed and very rarely change, so the technique is ideal for an AFC application targeting Wi-Fi 6-GHz interference issues.
The bottom line, according to Hetting, is that “Wi-Fi/5G coexistence simply works”.
And as previously reported, it will be even more relevant when Wi-Fi 6 and 6E begins to proliferate.
That is a consequence of the additional support from deploying OFDMA (Orthogonal Frequency Division Multiplexing) in the next generation of Wi-Fi. Unlike the previous iteration of OFDM, the latest version allows multiple clients with varying bandwidth requirements to be connected to a single Wi-Fi Access point simultaneously.
Irrespective of how all this plays out, the existing distinctions in emphasis between cellular and Wi-Fi will continue going forward, even as we get increasing coexistence between the two. The reality is 5G will offer large area coverage and super-fast mobility within the whole supported area; and not even Wi-Fi 6 or 6E will be able to match that. But hey were not designed to do so.
So what will change for the consumer? Wi-Fi will continue to work out cheaper for devices such as tablets and laptops, and smart TVs as well. And 5G will still be relying on SIM cards, with more sophisticated features that will likely work out to be more expensive to offset operators’ costs for providing an additional radio.
For that users, and perhaps more importantly enterprises, will enjoy the benefits of ubiquitous connectivity at much faster speeds.