[8fingerlouie]

> but I’m struggling to imagine what the source of uniqueness could be for a single cell tower.

GSM is/was a complex beast. Each base station can only handle 8 simultaneous phone calls (the old 2G/3G multiplexed ones, not modern VoIP), so in crowded areas they’re usually configured with a very short range. Some large conferences have had base stations with their range measured in single digit meters (<30 ft).

Furthermore, like WiFi, bandwidth is limited, so base stations are deployed in a “beehive like pattern”, like a triangle with a base station radiating out from each leg, and broadcasting at different frequencies to it’s neighbors.

That alone leaves a lot of room for configuration errors on each individual base stations, but when i say “a single cell tower”, i meant on that drive. The bug might be with a specific firmware version of that base station manufacturer, or that particular hardware revision, or simply a configuration error, or maybe it was a bug in our software and/or radio firmware. There are a lot of “moving parts” that needs to be investigated, but from a developer perspective, the error only occurred on one base station.

It could of course also turn out to be a “broken” base station, and often enough we would fail to find the error, and had to contact the network operator to get them to help trace down the error.

[k0k0]

> Each base station can only handle 8 simultaneous phone calls

Perhaps you are confusing that each GSM transceiver (TRX) provides 8 time-division channels with call capacity, but most cells and specifically the BTS in GSM parlance, especially any in a well populated area have/had way more than one transceiver. 30-40 was not unheard of in later equipment, though 10 or so was more typical. Late in GSM's life there was another technique to squeeze more channels, OSC.

Furthermore those 8 TDMA slots could be split in 1/2 or 1/4 with lower rate codecs, so it was more than 8 per TRX as well.

anything bigger than a picocell would carry way more than 8 simultaneous calls.

> Some large conferences have had base stations with their range measured in single digit meters (<30 ft)

Femtocells are still a thing today. Not so much to do with frequency capacity.

[8fingerlouie]

> Perhaps you are confusing that each GSM transceiver (TRX) provides 8 time-division channels with call capacity

I was talking 2G/3G. It has been 20 years since i wrote software for mobile phones :) But i should probably have been more specific and said you can have 8 active calls per channel. And i have no doubt today with 4G/5G and a shift to VoIP that you can have way more than that.

> Femtocells are still a thing today. Not so much to do with frequency capacity.

I was attempting to refer to the scalability/complexity of the network, which scales from 10s of kilometers to 10s of meters, or even more/less.

But as i said, i wrote software for the phones. My understanding of the network side of things was/is limited to the rudimentary knowledge needed to write that, and i'm happy to be corrected.