Just to add a piece of data to support this:

> It turns out the phone signal inside the station can be better than the one above ground

I was surprised when I noticed I had 5G in the tunnel, ran a speed test and hit 641Mbps down!

https://www.speedtest.net/result/i/6831252952

Definitely not. Try it in Tokyo, every single line, every single station has high speed coverage. I can’t recall signal ever dropping out for me.

I wonder if they considered using the existing metal tracks as antennae, or even https://en.wikipedia.org/wiki/Power_line_communication to feed base stations in the trains themselves.

So the ESN in the tunnels runs at 400 MHz, far lower than the 700 to 3,600 MHz range usually used by smartphones.

It's worth noting that 450MHz was listed as one of the GSM bands, but apparently was never used: https://en.wikipedia.org/wiki/GSM_frequency_bands#GSM-450

I use the underground frequently. It doesn't really feel like half of it is covered. Where it is available, it works amazingly. I might have been using the other half by sheer luck.

Pretty neat but as someone who commutes every day on the New York subway I hope it’s never “cracked” here. Phone usage without headphones is already annoying enough and I greatly appreciate the various people trying to take calls eventually lose service.

This is the new system for emergency communications? TfL just finished up an upgrade on that in 2021. That upgrade was built by Thales.[1] That system is purely for operational use, and is not cell phone compatible. It's compatible with the gear cops and fire brigades use. Is it being replaced?

As late as 2018, the classic century-old system, with two bare wires on insulators on the tunnel walls, was still maintained.[2] Clipping a telephone handset to the two wires would connect to a dispatcher, and the wires were placed so that reaching out of the driver's cab to do this was possible. In addition, squeezing the wires together by hand would trip a relay and cut traction power. Is that still operational? The 2011 replacement was ISDN.

[1] https://www.thalesgroup.com/en/news-centre/press-releases/th...

[2] https://www.railengineer.co.uk/communications-on-the-central...

I had assumed the delay was technical but it turns out it was mostly about finding a business model that worked for everyone. It is good they finally settled on a shared infrastructure approach so they do not have to crowd the tunnels with extra equipment.

I'm having a really hard reading this. Not only are the paragraphs are so short, they each feel like part of a uncompleted thought.

The content doesn't feel AI generated, but maybe it is? I read somewhere that short paragraphs is an AI signature!?

Interesting! I know Sweden was not first, but Stockholm has had 3g coverage in the subway since 2005 and 4g since 2016.

One of the frustrating things about international roaming in the UK is typically your plan does not include coverage on this neutral network on the underground

Anyone who lives in London knows that phone coverage on the Tube is anything but "cracked".

> There’s another distance limit at work here, and that is the speed of light. It takes milliseconds for the signal in your phone to reach the hotel above ground and be handed over to the mobile network.

It takes roughly 100us for light to travel 30km – Can you explain how the speed of light is relevant here?

From looking at the WiFi ssid’s broadcast at the New York subway stations, I believe Boldyn also does the phone coverage here too

As a resident with a phone problem I miss the underground not having any signal. Other people using TikTok doesn’t bother me so much because it’s relatively rare. My own tendencies with screen time bother me more. No internet actually forced me to read books more and I miss that.

But this is a lot better for tourists who need the internet to navigate underground. So I’m pleased for them.

How London enabled TikTok addicts to annoy other passengers

The Paris metro figured this out perfectly way back in 2021 - full bars, 5G.

>There’s another distance limit at work here, and that is the speed of light. It takes milliseconds for the signal in your phone to reach the hotel above ground and be handed over to the mobile network. But if it takes too long to get from phone to hotel, then your phone call s..a.rt..s..t o. br..e..ak up. As it happens, that distance is about 12km, so Boldyn needs nine hotels around London to cover the whole of the Underground

I find that interesting. Another fascinating rabbit hole the article has sent me down is that there is an unused station called north end. I've been down that stretch before and i had no idea. Does anyone know if passengers can see it?