When Wi-Fi was first introduced on the London Underground ahead of the 2012 Olympics, it felt like a watershed moment. Although connectivity could sometimes be patchy and was confined to stations, it marked the beginnings of a 21st century makeover for the capital’s ageing metro, a digital bridge between the subterranean Victorian world and the data-saturated landscape above. Over a decade on, however, and that makeover doesn’t feel so fresh, struggling to keep pace with modern demands for 24/7 connectivity.
In response, Transport for London (TfL) is undertaking a major programme to deliver a new communications network for the London Underground, known as the Telecommunications Commercialisation Project (TCP). As well as providing a digital backbone for the railroad’s own operations, the vast array of new cellular and fibre optic infrastructure will provide customers with ‘always-on’ coverage throughout their Tube journeys for the first time.
“It’s all really about customers and the customer experience,” Matthew Griffin, head of Telecoms Commercialisation at TfL, told The Engineer. “The Holy Grail is obviously getting connectivity everywhere, all the time... fundamentally for the customer, it’s going to be a whole different experience.”
Working in partnership with telecoms specialist BAI Communications, TfL is currently in the process of fitting out 137 stations and 400kms of tunnel pairs with a host of new equipment. In the stations, commuters’ phones connect to radio frequency (RF) antennas – typically six per platform – which in turn connect to cabinets up to 90 metres away over structured cabling.
At the cabinets, the RF signals are converted to optical light, which then travels up to 11 kilometres to one of 10 data centres currently being built in partnership with the four main mobile network operators (MNOs): Three, EE, Vodafone and Virgin Media O2. The data centres convert the signals back to RF, joining the rest of the MNOs’ cellular traffic.
“Stations like Kings Cross have a massive amount of antennas,” explained Ken Ranger, chief operating officer at BAI Communications UK. “Smaller stations like Warwick Avenue, a lesser amount of antennas. As an example, there’s approximately 600 of these cabinet locations and approximately 8,000 antennas throughout all the stations.”
With Wi-Fi connectivity in most Tube stations old hat at this point, BAI and TfL shouldn’t expect much praise from blasé London commuters for enhancing those signals. The real showstopper of the TCP – the trick that will get tongues wagging, both literally and figuratively – will be the inter-station connectivity as trains careen through tunnels, comms blackspots now suddenly illuminated with cellular coverage and high-speed data. This is achieved by the presence of a linear antenna – known as a ‘leaky feeder’ - that runs the length of the tunnels, linking London’s depths to the information superhighway.
The Holy Grail is obviously getting connectivity everywhere, all the time... fundamentally for the customer, it’s going to be a whole different experience
“It’s about 175mm by-diameter cable that has to run at window height all throughout the underground, so we have to find space to put this cable against the wall,” said Ranger. “Your phone radio frequency goes through the window of the Tube, into the antenna. Every 500 metres or so, there’ll be a high-power radio and that’s where it converts it back to optical light, 11 kilometres to the data centre.”
Needless to say, the Tube was not originally designed to house advanced telecoms infrastructure. Rolling it out across the network is not just a major engineering challenge, it’s a project management task of labyrinthine complexity, requiring high levels of coordination between BAI, TfL and the various teams of workers needed to carry out the installations.
“It’s a lot of work,” said Ranger. “It’s time constricted. There’s not a lot of space. The antennas at the station, time constricted, not a lot of space. But finding where the cabinets go and these high-power radios, that’s the complex part, because you have to do the fire engineering, the electrical upgrades, the cooling of the equipment. Power, is there enough? Is the floor strong enough to take the structural loads imposed. So that’s all the works in the project, in a network that runs for 20 hours a day to the public and only closes four hours a day, but then it’s doing other maintenance activities at night.
“There’s no space in the stations to store equipment, so everything’s got to be brought in and brought out in spools. So you can start to think of the logistics, driving in central London...there’s a lot of moving pieces.”
Given the complexity of the TCP, it’s perhaps not surprising that there’s been a 10-year gap between the original Wi-Fi installation and the current programme. According to TfL’s Griffin, several plans were hatched in the interim, but most never made it off the drawing board. Where the new project has succeeded, he said, was in the tightknit coordination between TfL and BAI from the outset.
“We very much took this as a kind of partnership where TfL’s engineering team would make themselves available to BAI to help and support them,” said Griffin. “We’ve had over 100 TfL engineers work on this project so far. So there’s been a real sense of joint engineering effort to get this done…that partnership has really been the bedrock of the success of this, I would say.”
Having worked on the Wi-Fi install over a decade ago, Griffin was fully aware of the challenge of embedding telecoms into the Tube environment. London Underground is the oldest metro in the world, home to a dizzying variety of tunnels, trains and stations. While BAI had previously delivered cellular systems for metros in Toronto and Hong Kong, the Tube is an altogether different beast. Bringing full mobile connectivity to its intricate network is a mammoth endeavour, one which Griffin himself admitted can sometimes be further complicated by TfL’s own rigorous processes.
“TfL’s a nightmare and also great in that we’ve got lots and lots of well defined standards,” he said.
“Navigating through that minefield, once you’ve done it once, actually your life is a lot easier. But that navigation can be quite difficult if you’ve come from the outside. A lot of telecom companies don’t get it at all. They’re used to digging up a farmer’s field and putting up a mast. That’s a very different job than putting something in a Section 12 station underground, with very rigorous fire safety, the most rigorous in the world.”
Ranger, a veteran of some of BAI’s other metro projects, is all too aware of those rigours. But, like Griffin, he revels in the challenge of updating this beloved ageing railroad.
“The Tube network is 160 years old this year,” he said. “We’ve 11 different lines, you know, different signalling systems and different status of modernisation...the heritage features...it very much plays into everything we do.
“The history of this railroad...the stations we just put live, Archway and Kentish Town, they opened to the public in 1907. So it’s fascinating.”
TfL’s first trials for the TCP began several years ago, testing equipment on the Waterloo & City line during its weekend closures. Griffin and colleagues assessed different types of leaky feeders, measuring how much signal could penetrate through the carriage windows when trains travelled in tunnels, as well as the number and positioning of high-powered radios to keep the signal consistent. Once this early work had established the parameters for a working system, the first public trials kicked off on the east end of the Jubilee line.
The MNOs also came onboard at this stage, delivering some of the base stations that provide the core of the underground cellular connectivity. Being a public trial, TfL began getting feedback from commuters too, enabling them to see what was working and where improvements were needed. A bidding process then followed, with BAI subsequently awarded a 20-year concession in June 2021. Work has been creeping along steadily in the interim, different sections added piecemeal as the busy Tube network has allowed.
“We’ve chosen to not have it all done at once and have a big bang,” said Ranger. “So you’re going to be seeing just pieces of it come live. And there’s reasons for it, but it’s not always evident to the public.”
At the time of writing, some Zone 1 sections of the Central and Northern lines were almost ready to be switched on. However, the impending coronation on May 6 had stalled things slightly, with major works put on hold as the capital prepared for another big weekend of pomp and ceremony.
“We don’t really want to change much until after the coronation,” Griffin explained. “It’s surprising how much planning goes on in TfL for events like that. People don’t realise how disruptive it is for our general operations. We are very good at it but, you know, it takes a lot of work.”
Testing is also currently underway on central parts of the Victoria, Bakerloo and Piccadilly lines, meaning that by the end of 2023, a substantial part of the Tube’s pulsing Zone 1 heart should be fully connected. What’s more, 5G speeds should be the norm, as the initial 4G plans have been upgraded following 5G trials.
“It’s been hugely popular with the main customer, which is the MNOs,” said Griffin. “They have absolutely loved it and now they want 5G from the get-go for everything...so hundreds of Mb (speeds) on 5G are going to be quite common I think.”
“We specified it had to be 5G compatible, we called it ‘5G-ready’, from the beginning. So turning 5G on is mostly about the MNOs putting 5G base stations into the base station hotels. And obviously then connecting it up, doing integration testing and then making sure they’re happy with turning it on.”
While the customer experience is undoubtedly the biggest driver of the TCP, overall railroad connectivity is also a major incentive for TfL. The original Wi-Fi installation was justified purely on the basis of commuter and tourist utility ahead of the London Olympics. At the time, Griffin and colleagues didn’t realise just how much the connectivity would enhance the running of the railroad itself. With the TCP, they are fully aware of the benefits in store.
“Now it is a critical part of our operations,” said Griffin. “And it wasn’t part of the original business case (in 2012), but it is now. It’s changed the way that we operate our stations completely because we’ve got that connectivity. And I think we’ll find that same sort of uptake and innovation in the way that we operate the railroad will happen with cellular coverage as well.
“The trains will be connected all the time. We’ll be able to monitor them in real-time. With the Internet of Things, nearly all the signalling system, everything we put in the Tube these days, you can monitor in real-time. And we’ll be able to do that properly, because at the moment it’s more sporadic.”
Another major component of the TCP is the rollout of 200km of high-speed fibre optic cable throughout the Tube. This will allow TfL to offer fibre to businesses, public services and potentially residential properties above the network’s tunnels and stations. Naturally, this network correlates closely with business and population densities topside, presenting a strong commercial opportunity for TfL as it seeks to diversify revenue streams in the wake of Covid and its hit to passenger numbers.
“The trains will be connected all the time. We’ll be able to monitor them in real-time.
“Each tube station - certainly in the Section 12 ones which are the underground ones and will have cellular coverage - all of those are going to be points of presence for the fibre network,” said Griffin. “So potentially thousands of extra fibres through the Tube tunnels. And of course, they’re segregated from everything else, much less likely to be dug up by somebody doing some digging, so super reliable.”
An aspect of the TCP’s wider remit will also see the installation of London Underground’s segment of the new Emergency Services Network (ESN). Part of a wider national programme led by the Home Office, the ESN will replace the existing Airwave service currently used by blue light personnel across Great Britain. It is designed to deliver voice and data prioritisation for the emergency services, ensuring they have access to the communications and information they need wherever they are, including the Tube.
These multiple strands of the TCP – cellular, fibre, emergency networks – make it one of the most complex and ambitious projects ever attempted on a metro system. According to BAI’s Ranger, rollout should be “substantially complete” by the end of 2024, with the vast majority of stations and tunnels upgraded. It will be fascinating to see how Londoners adapt to this all-encompassing subterranean connectivity. Will phone calls, Zoom meetings and Instagram livestreams become standard practice, piercing the passenger omertà that has long been a central doctrine of Tube travel? For those horrified by the prospect: enjoy the silence. It may not be around much longer.
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