3 ms·
I wonder if they considered using the existing metal tracks as antennae, or even https://en.wikipedia.org/wiki/Power_line_communication https://en.wikipedia.org
by userbinator 10mo ago
I wonder if they considered using the existing metal tracks as antennae, or even https://en.wikipedia.org/wiki/Power_line_communication 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 https://en.wikipedia.org/wiki/GSM_frequency_bands#GSM-450
- wolvoleo 10mo agoWeird because very few phones have that band. Requires much larger antennas. Twice as long as for 800Mhz. Edit: ah I see why, this is exclusively about the Emergency Services network, not for regular phones. In that sense it seems a bit similar to GSM-R used by the railways here.
- fundatus 10mo ago> It's worth noting that 450MHz was listed as one of the GSM bands, but apparently was never used It's specified for 4G/LTE (Band 31, 72 & 73) and 5G (Band n31 & n72) as well! The bandwidth is pretty low though at just 5 MHz, but it's used for special purpose stuff like electricity meters. I'm not aware of any consumer devices that use this frequency.
- celsoazevedo 10mo agoI think that part of the article is wrong. The old radio system apparently uses ~400 MHz, but ESN seems to use the same/similar bands as mobile services (700 MHz and above).