open RAN

DT says open RAN is not good enough for wide-area use

It has not been a good few months for open RAN and the mood will just have darkened within O-RAN Town, the Deutsche Telekom testbed at Neubrandenburg. Amid vendor rumblings that brownfield operators had grown too cautious about open RAN, the German telco incumbent has just published a status update on the technology concept and its readiness for commercial deployment. The short summary is that open RAN is still not good enough.

This is a major blow to open RAN vendors that have had to make do with less than a handful of "greenfield" rollouts worldwide. Of course, Deutsche Telekom is only one service provider and others may think differently. But a separate update also published this week is similarly downbeat, and that one bears the logos of Orange, Telecom Italia, Telefónica and Vodafone, besides Deutsche Telekom. Rollouts in Europe are being delayed by "existing contractual obligations" and the "challenging financial situation that operators and service providers are suffering from," it says.

Deutsche Telekom top execs Claudia Nemat (head of tech and innovation), Srini Gopalan (head of Germany) and CEO Timotheus Hottges pose for the camera. (Source: Deutsche Telekom)
Deutsche Telekom top execs Claudia Nemat (head of tech and innovation), Srini Gopalan (head of Germany) and CEO Timotheus Höttges pose for the camera.
(Source: Deutsche Telekom)

Without saying as much, Deutsche Telekom has now scrapped any plans for a wide-scale deployment of open RAN this year, as communicated to Light Reading at last year's Mobile World Congress. "We are talking about covering-city deployments," said Abdu Mudesir, Deutsche Telekom's chief technology officer, back then.

The whole project had run into delays, Light Reading was able to reveal in December, with Deutsche Telekom saying it was "still in the process of qualifying vendors for a commercial rollout from 2023/24." The best that can be hoped for now? In the report out this week, the operator says that "a smaller scale multivendor open fronthaul-based deployment capable of supporting all Deutsche Telekom services is realistic by the end of 2023."

Multivendor nightmare

One of the main problems is Deutsche Telekom's apparent insistence on open RAN being multivendor. That is not altogether surprising. The concept is, after all, about marrying different suppliers at the same mobile site, and not buying all the various parts and software from one big vendor. Yet brownfield open RAN enthusiasts in the US and UK (specifically Vodafone, in the latter case) seem happier to keep purchasing most products from a single supplier, provided they are compatible with open RAN specs.

Multivendor is complicated, as Deutsche Telekom makes clear in its white paper. It's been using massive MIMO radio units from Japan's NEC, and less advanced radios from Fujitsu (another Japanese vendor), with baseband software supplied by Mavenir, a US company. If one reads between the lines, this mash-up did not deliver the necessary performance and power efficiency (both of which Deutsche Telekom said are now focus areas).

Integrating these various bits is a massive headache (effort was "quite high" is how Deutsche Telekom puts it). Ideally, in future, it wants to rely on "pre-integrated equipment combinations that leverage certification and badging frameworks." Essentially, that means having lots of different suppliers join up with one another like a giant swingers' party before they are allowed anywhere near a commercial rollout. But many of these suppliers now boast end-to-end offerings. Does this much collaboration between supposed rivals not stoke competition concerns?

Intel monopoly

One of the other big problems is more to do with virtualization – the separation of hardware from software – than it is with open RAN per se. As Deutsche Telekom notes, "commercially available open RAN solutions remain highly dependent on the chosen hardware." Introducing hardware accelerators to address some of the performance shortcomings of general-purpose processors unsurprisingly makes this problem worse (basically, you are putting hardware dedicated to a specific task back into the mix).

It's more troubling than many assume, as well. That's partly because the whole virtualized RAN sector is still heavily dependent on Intel, the dominant force in the market for general-purpose chips. A telco source very involved in all this (who wanted to remain anonymous) acknowledges there are no virtual RAN deployments today that don't feature Intel's central processing units.

And FlexRAN, Intel's own reference architecture, does not tick the open and virtualized boxes, according to some industry figures. "Even if you use FlexRAN, you have to design your software in a particular way using the instruction set FlexRAN gives you," said Yago Tenorio, Vodafone's network architecture director, in November. "Once coded for FlexRAN, it is not portable for another accelerator – you can only use Intel from that point on."

Franck Spinelli of Amarisoft, a software startup that has a relationship with Vodafone, is equally scathing. "FlexRAN is not vRAN," he told Light Reading via LinkedIn. "The PHY [shorthand for physical layer of the network] is hardware accelerated by an Intel card that you can't plug into an AMD or ARM PC. So you're back to specific hardware."

Fiber shortage

Another issue is centralization. One of the main benefits of vRAN (arguably the only benefit) is that it would more easily allow operators to pool baseband resources (the open distributed units, or O-DUs) in data centers or other facilities, where RAN software could sit on shared general-purpose equipment. The trouble is that any operator doing this would need to run a lot of fiber between these facilities and its newly baseband-less radio sites. "As redesigning the fiber infrastructure is hugely costly, O-DU aggregation will not be possible on many sites in Germany," said Deutsche Telekom.

Deutsche Telekom and Europe's other telcos certainly aren't giving up on open RAN, but the countdown to 6G has already started and its window of 5G opportunity is slowly closing. It's arguably a bigger problem for the German incumbent than it is for many others. It has grown heavily reliant on Huawei, a Chinese vendor disliked by many German politicians, and previously abandoned Nokia in Germany, replacing it with Ericsson.

Despite a recent Nokia resurgence, and Tenorio's view that Nokia now has a "fully compliant open RAN system," the Finnish vendor warrants not a single mention in Deutsche Telekom's latest white paper, replete with the names of Asian and US suppliers. So much for a European ecosystem.

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— Iain Morris, International Editor, Light Reading

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