How London cracked mobile phone coverage on the Underground

Summary

Dotted around London, there are a number of private hotels that aren’t the sort of hotel you might expect – they’re needed to make mobile phones work on the London Underground. They’re not for humans, but for huge racks of computer and electronics equipment – and each of the UK’s mobile networks is renting space inside them, as this was one of the innovations that allowed phones to work underground in the first place. While many newer underground railways have had mobile coverage in their tunnels for years, fitting it into the London Underground kept running into the same problem – it costs a lot of money and needs a lot more space in the stations than is available. Classically, each of the mobile networks would install its own kit in each station and manage it, but there simply wasn’t enough space for that in London’s old tube stations, many of which were built before the wireless telegraph was even invented. However, as radio equipment has become smaller and cleverer, it’s now possible for several networks to share the same equipment, and in 2021 Boldyn Networks (then BAI Communications) signed a deal to build a “neutral network” that can be leased to mobile networks. Bodyn has a 20-year concession with Transport for London (TfL) to build and operate the network, and, aside from internal staff time spent managing the project, it’s being delivered at no cost to TfL. The new network doesn’t just provide phone coverage for customers; it’s also part of the government’s Emergency Services Network and might, in the future, replace staff radios when they’re being upgraded. In fact, the customer-facing part of the network, while not insubstantial, is the smallest part of the whole project. Given the hundreds of millions it would cost to upgrade the emergency service network and staff back-of-house radio networks, it makes sense to provide a public service as well. So, for the past four years, hundreds of miles of cabling have been rolled out (literally) into the tunnels a...