The challenge of running mobile underground

Last month's news that London Underground is finally set to get 4G mobile connectivity was unsurprisingly greeted with joy around the capital. The Tube was the world’s mass transit underground and was a trailblazer for the systems that followed. It seems perverse then that London’s imitators have been quicker to implement mobile phone systems. Some cities – Tokyo and Seoul for example – have extensive cellular networks and others metropolitan areas – New York and Toronto – are catching up.

The update is long overdue - London is a premier business city and it’s no longer acceptable for travelling business people to be out of contact with their offices for long – the need to stay connected has given a boost to taxi drivers but it means that many visitors are not using the quickest and most efficient way to get across the capital.

But it’s London's antiquity that has proved to be the sticking point. Much of the TfL Underground network, which began in the Victorian era, still has infrastructure dating from that period, adding to the difficulty of implementing a mobile system. If you throw in the fact that the tunnels can be very narrow and some are especially deep, then there are a number of serious logistical difficulties to be overcome before installing a cutting-edge phone network.

How then will the mobile systems to be rolled out? Andy Conway, director of engineering at the BAI Group, is someone with extensive experience of the difficulties of rolling out mobile phone systems. BAI was responsible for the cellular networks installed in New York and Toronto, so it’s a company that is fully aware of the challenges that Transport for London (TfL) faces.

In many ways, now is almost the wrong time to be implementing such a network. The Underground used to shut down around midnight each day, but over the past few years, trains have been running later and, at weekends, run through the night. “One of the biggest constraints is that underground is increasingly 24/7. That makes it a real challenge to sort out logistics,” says Conway.

TfL did carry out a trial run for how the new system will work, testing a 4G system on the Waterloo and City line this summer with the assistance of all four major UK operators - although O2 and Vodafone conducted the trial itself.

While this would have given an indication of how mobile can work underground, it wouldn’t have given much guidance of how the logistical difficulties could be surmounted: the Waterloo and City line connects just two stations – Waterloo and Bank – and only operates in peak hours.

That will give no indication as to how the new system will be rolled out, BAI is watching the tender process with interest. This will begin in 2018.

For Conway, it’s only the technical challenge that can cause difficulties. “We were involved in the rollout of the New York subway, that’s 1.8 billion passenger trips annually – slightly more than London – but a comparable number. But what New York showed us is that it was less about the technology and more about the political will to get things done. That was there in New York, so much so, that we delivered the project, two years ahead of schedule.”

Political support

The initial signs, Conway says, is that the London project will benefit from the same amount of goodwill, with support already forthcoming from London's politicians and transport authorities alike.

However even with all this level of co-operation, the technical challenges to overcome are still considerable. “You have to rewrite the engineering rule book, you can’t put a series of masts underground: it’s damp, it’s hot and very cramped,” Conway notes. Then there’s the nature of environment. “The electronics are very fragile. It’s not just the damp, even brake dust can impact on the systems. We have to house those electronics in special cases or they just won't work.”

And the infrastructure itself has to be treated differently. “We have to run a system of base-station hotels – basically datacentres that are run several kilometres from the Underground and connected by fibre. “

Because the tendering process hasn’t started yet, Conway says that it’s hard to give an accurate idea of exactly how the system will be constructed but, again, going against the benchmark of New York, that will be about five or six of these base-station hotels.

For the same reason, he can’t go into extensive detail on how the Underground system will work. “The detailed models have yet to be decided but, if we win the tender, we’ll be creating a solution on behalf of the TfL and working closely with the network operators”

One element, however, that Conway is sure about is that the system will be future-proofed. “It will be 5G ready. My personal experience is that 5G is coming and it’s going to be big. At the moment, it’s being supplier-led but Ofcom has started to look at pioneer bands.”

So, although the system being implemented is 4G, Conway is sure that it will be ready to support the faster system. After all, it’s going to have to support millions of users, who not only will want voice connectivity, but also a strong data network.

It will have a profound effect on the way that commuters use the Tube but it’s not before time. “We think of not-spots, where you can’t get mobile connectivity, as being deep in the countryside, but really the biggest not-spots are underground,” adds Conway.