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BT’s obsession with energy efficiency sees its Networks division striving for flexibility

“We’re obsessed with something called bits per second per hertz per megawatt,” said Professor Tim Whitley, BT’s chief executive officer for applied research, during a recent BT Networks investor briefing.

Howard Watson, BT’s Chief Technology and Information Officer, echoed BT’s same energy efficiency metric: “This is the real challenge in the supply chain now. Not only is it good enough to give us better spectral efficiency — that efficiency measurement needs to include energy consumption as well.”

As a name, it’s a bit clumsy – but it’s the ultimate measure of “how much capacity you can get on the fuel of a cellular network.” And from the briefing, the entire BT Networks team is full of energy. While that’s true for almost everyone in the world right now, BT has more to worry about than most.

The BT Energy Efficiency Mountain

Tim Whitley turns to advanced technology to improve BT's energy efficiency
Tim Whitley, MD Applied Research, BT

BT uses 2.5 terawatt hours (TWh) of electricity per year (and a further 200 gigawatt hours (GWh) of oil and gas), or around 0.75% of the UK’s total electricity consumption in 2021. For a single organisation, that’s a significant achievement.

This is also why BT’s energy efficiency is a priority. According to Emily Clark, Chief Financial Officer at BT Networks, despite 84% of energy being hedged this fiscal year and 50% next fiscal year, energy costs are still up 80% within these hedging arrangements. According to Clark, BT intends to move towards longer-term power supply contracts, which currently account for about 17% of telecoms needs.

Energy consumption figures were readily available throughout the investor briefing: According to Watson, fiber-to-the-curb (FTTC) broadband consumes 2.4 watts per customer, while fiber-to-the-premises (FTTP) consumes just 0.3 watts. (In a shrewd argument with Virgin Media, BT’s main competitor for broadband networks, he suggested that its DOCSIS technology draws 5 watts per subscriber.)

“A statistic for you that I might not want to share, but I’ll do it now: if you walk into an exchange building, look at the electronics in an exchange, almost half of them are off,” because that’s no longer needed , Watson told analysts during the briefing. “What we need to do now is ensure that we responsibly remove all of this infrastructure.”

That’s BT’s next big challenge: closing 4,500 of its 5,600 or so telephone exchanges and shutting down the old network equipment inside. This alone will boost BT’s energy efficiency, saving 550GWh on electricity bills, according to Watson, freeing up valuable real estate and recycling a tremendous amount of old infrastructure, which BT estimates will yield around 200,000 tonnes of valuable copper.

BT's energy efficiency offensive will get a big boost with its stock market shutdown program.  Image courtesy of BT.
BT’s energy efficiency offensive will get a big boost with its stock market shutdown program. Image courtesy of BT.

The long way to market optimization

This is a long process, however, which suffered a setback when BT had to delay phase one – migrating customers to Digital Voice – in early 2022 due to customer complaints. Watson said BT is still on track to migrate to Digital Voice and PSTN shutdown by December 2025, with the long-term goal of closing most of its exchanges by 2035/36.

“We control the closure [by 2024] of five exchanges currently, one of which is here in London, to understand the implications of this and ensure we take clients with us on this journey,” said Neil McRae, BT’s chief architect.

“We actually picked about 100 that we think are some of the best buildings, ie those are the ones that the real estate team is saying to me, please get off these first, please get off these. And we intend to move past that 100 by the end of the decade,” Watson added.

CTIO Howard Watson strongly pushes BT drive for energy efficiency.
Howard Watson, BT CTIO

He also suggested that replacement buildings – as well as FTTC cabinets (those little green boxes now seen on most streets in the UK) – could find uses for edge computing applications. BT is still exploring how best to leverage edge computing – Whitley cited uses for applications like volumetric video.

One thing the telco will be doing at the edge is colocation to get closer to hyperscalers like AWS and Google Cloud, “bringing our network close to them, allowing us to market their services to our customers and partnering with the to work together in the public cloud”. to McRae.

The hyperscalers have also inspired BT’s ‘Network Cloud’, which aims to allow the telecom network to scale up and down as needed, creating the ‘Network-as-a-Service’ that Harmeen Mehta, Chief Digital and Innovation, believes in Officer of BT, during this period, strongly referenced a previous investor briefing.

According to McRae, Network Cloud currently has 12 locations with 2,000 servers: “It’s all software driven. We leverage the latest telemetry and API-based technology, as well as cloud-native technology to enable a platform that scales as needed. And then it also allows us to run applications under our control effectively under the demands that we have as a telecom company, as opposed to what the hyperscalers can offer us and most importantly allows us to scale up and down.

“The network itself becomes an object in programming, so you as a customer, as a developer or as a member, can write code within BT to create a piece of the network that could be a high-speed route from London to Glasgow, it could be an SMS service, it could be a voicemail service. But through APIs, you can set up a network feature, use it the way you want, and then and then stop using it,” he added.

While the flexibility of the Network Cloud promises to be very powerful, in the meantime BT needs to find ways to manage capacity and optimize the efficiency of its core network, which is handling 28 Tbps of data, 25 Tbps over broadband and 3 Tbps over Ethernet at peak times.

Reduce costs through caching

According to Watson. One of the key ways BT is reducing its load remains through caching: “We’ve been using Qwilt, which is a form of open cache, and we’ve worked with content partners there, which means we have a small percentage of the revenue that helps fund that too . It’s actually quite a large amount [of data]; I mean if we took away the caching the 28 Tbps we have now would be a lot higher.”

Neil McRae believes BT's energy efficiency can be improved with Network Cloud.
Neil McRae, BT Chief Architect

He also said that content providers, including video streamers and streaming gaming platforms, have recognized the value of working with network providers on launches: “Content people are realizing that it’s not just about throwing it on the network and hoping – they really want it to make sure that when they release their program, if you’re Disney and you’re launching Mandalorian season 4, you want it to be a phenomenal experience.

Watson noted that during the height of the pandemic lockdowns, McRae was able to convince Call of Duty and Fortnite “not to launch their products at the same time every night at 7pm and help by spreading that out throughout the day.” .

And as TV broadcasts migrate to IP-based networks, the challenge remains to convert a unicast IP stream that cannot be cached to multicast, which would significantly reduce the load on the core network.

Eyes on BT’s energy efficiency award

McRae is still pursuing BT’s energy efficiency targets and said the telecoms company is in the process of moving from 100 to 200 and 400 to 800 optical networks thanks to Nokia’s platform. Looking ahead, McRae hopes OpenRAN’s flexibility will help save power, while Whitley said the telco’s labs are working with universities on “hollow-core fiber” and also on Massive MIMO and Ultra MIMO, which can boost data rates factor 10

Ultimately, the priority for BT Networks remains simple (albeit a bite): bits per second per hertz per megawatt. That keeps falling – the challenge will be if it falls fast enough.

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