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Observing my cellphone switch towers

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Re: Observing my cellphone switch towers

#101

Post by NaturalPhallacy »

rcarmo wrote: post #16

This is nicely done, and takes me back to when I worked in mobile network planning. Most people are blissfully unaware of how much radio chatter and constant adjustment is actually holding up their browsing session from second to second, with the UE negotiating the best possible terms (power, throughput, etc.) with adjacent cell towers before it decides (or is prompted) to hand-over to a new cell. Optimizing cell han…

>Most people are blissfully unaware of how much radio chatter and constant adjustment is actually holding up their browsing session from second to second, with the UE negotiating the best possible terms (power, throughput, etc.) with adjacent cell towers before it decides (or is prompted) to hand-over to a new cell.

My experience in my networking class in college and how complex even a TCP/IP connection is over a reliable wired connection was enough to make me run screaming from the field as a profession.

The fact that I can get 200/mbit on my phone today still astounds me.

It's an interesting, but even to me an intimidating field.

Re: Observing my cellphone switch towers

#102

Post by lukec11 »

ganafagol wrote: post #17

Would be great to have an app that shows a map with my position and the position of the current cell. And that could create such maps as in the article on-the-fly. Anybody knows of such an app?

CellMapper[0] is not real-time, but it collects data to make sector maps and estimates the position of the current eNB. Users who contribute enough data can "pin" these eNBs in the correct location.

Despite not being real-time, it's the best / most accurate app I've found of its kind and has a good community behind it.

[0] https://www.cellmapper.net/map

Re: Observing my cellphone switch towers

#103

Post by rtkwe »

ThrowawayR2 wrote: post #93
heelix wrote: post #45

Something like this would make it pretty easy to spot one of those stingray devices, I bet. Cell towers tend to stay put, so mapping out an area would go quick. Were a new 'tower' show up in an odd spot -- there may be shenanigans at hand.

> " Were a new 'tower' show up in an odd spot -- there may be shenanigans at hand. " Or maybe it's simply https://en.wikipedia.org/wiki/Mobile_cell_sites

Those will only really show up around large events or during disasters. There's little reason to just put one out there unless there's an event calling for the extra demand or a quick patch of the network coverage.

Re: Observing my cellphone switch towers

#104

Post by Rebelgecko »

kmonsen wrote: post #91
dTal wrote: post #82

Earlier quoted context omitted.

Could it possibly be because the time is being set from GPS, somewhere in the stack? The 19-and-a-half year offset is spot on. https://en.wikipedia.org/wiki/GPS_week_number_rollover

If so according to the link the phone needs to be from 2013 or older, or an iPhone from 2012 or before. That would give gp an award in no unnecessary upgrades :-)

It could be a cell tower that gets its time from GPS (incorrectly)

Re: Observing my cellphone switch towers

#105

Post by cesarb »

qb2021 wrote: post #53

At this one industrial customer I visit every week for a full day, my Verizon cell phone date/time time will suddenly change back by 19 years, six months, and some days (I don't have the exact value). This has been going on for almost a year. My pet theory was that law enforcement turned on a stingray nearby back in 2020, it came up with a default date of 1/1/2001, and has been running ever since. Steel building with…

Something similar has also happened to me. In my case, the symptom was that the TOTP 2FA to systems at work started to fail. It took me some time to find that the cause was an around 1 minute offset between my phone and the correct (NTP-synchronized) time as shown by my desktop. Setting the phone to not synchronize its date/time to the network (and correcting its time) fixed it, but it's annoying since without the network synchronization, the time slowly drifts. My theory is that there's one single tower that does not have its time correctly synchronized, and that annoyingly it's the "best" tower when I'm sitting at my desk.

Since then, I've not trusted that automatic network time adjustment, and I leave it disabled. Periodically, I check if it's drifted too much, and if it has, I quickly enable and then disable the network time adjustment (in a place far from the misconfigured tower).

Re: Observing my cellphone switch towers

#106

Post by hansor »

qb2021 wrote: post #53

At this one industrial customer I visit every week for a full day, my Verizon cell phone date/time time will suddenly change back by 19 years, six months, and some days (I don't have the exact value). This has been going on for almost a year. My pet theory was that law enforcement turned on a stingray nearby back in 2020, it came up with a default date of 1/1/2001, and has been running ever since. Steel building with…

It is not uncommon that entire towers or basebands have invalid time. Some of the reason that i encountered personally:

- Badly configured basebands (for example lack of summer/winter time change flag!)

- Broken PTP

- Stations that take time from NTP which does not exist or does not have route to.

- I don't know the name for it, but getting time from local Nodeb is an feature - and sometimes features are not active or licensed[1].

- Station setup with GPS instead PTP/NTP (let's say for 2G or some slower HDSPA modes) with broken GPS module itself

- Software error [basebands have multiple versions of software, same goes for APG's, SCU'S, RRU's and dozen other black boxes. Even cabinet itself have some software. This is big pain in the ass to keep them all updated in large network - as upgrade process can be disruptive and sometimes it is better to not upgrade [cases of some really wacky stations]...

- Problem with software in terms of PTP implemetation. For example there are some discrepancies between Huawei and Ericsson software when it comes to PTP.

[1]. This is big shocker for Open Source Software community:

- EVERY SINGLE FEATURE in base station is not only NOT free, but Telecoms needs to pay them every single month[all manufactures: Nokia, Ericsson, HUA do that]. We are talking here in about 100-200 licenses for various features per site alone. If you don't buy new license every 28 days - your base station will turn off and it's nothing you can do.

- Hardware provider can also refuse to give you new licenses in theory...

- This is real hell of SaS world that NO ONE is talking about.

Re: Observing my cellphone switch towers

#107

Post by sm4rk0 »

Useful pro-privacy tip from the article:

> According to the LTE specs, cell-towers don't have to perform UE hand-overs like in GSM/UMTS. The phone starts camping on the next tower while remaining in RCC_IDLE mode without emitting data. Not only does this save battery, it also means operators don't really know where the phone is as long as it remains in the same LAC.

And another tip: I wanted to know what "very expensive" means for LTE-related literature, so I searched DuckDuckGo for the first book mentioned (sold on Amazon for $105) and the second result was an OCR'd PDF at huaweicup.ru

Re: Observing my cellphone switch towers

#108

Post by grishka »

franga2000 wrote: post #52
masklinn wrote: post #24

Earlier quoted context omitted.

I believe iOS may not bother involving the GPS if the application requests (or is only granted in iOS 14) approximate location, and there are enough towers in-range to triangulate. Not having to enable the GPS subsystems and get a fix saves a fair amount of battery.

It's the same on Android - there's an "eco" mode of the location subsystem which will only use "passive" location indicators like WiFi and cell towers. In the "high accuracy" mode, GPS* will be activated, but until it lock onto enough satellites, passive location is used as a fallback/best guess.

Passive isn't that. My understanding is that it's piggybacking on other apps' location requests if there are any.

Re: Observing my cellphone switch towers

#109

Post by seraphsf »

callesgg wrote: post #76

”There are no open source LTE stack to learn from” That is not true, srsRAN is a opensource LTE project. That has both cell phone and tower versions. Runs on SDR boards like the limeSDR.

The Magma project is also an OSS LTE (and 5G) project: https://connectivity.fb.com/magma/

Re: Observing my cellphone switch towers

#110

Post by JadeNB »

Spooky23 wrote: post #98
qb2021 wrote: post #53

At this one industrial customer I visit every week for a full day, my Verizon cell phone date/time time will suddenly change back by 19 years, six months, and some days (I don't have the exact value). This has been going on for almost a year. My pet theory was that law enforcement turned on a stingray nearby back in 2020, it came up with a default date of 1/1/2001, and has been running ever since. Steel building with…

A guy on a team that I worked on detected one of those devices and called the university police (we were a tenant in a university building), who laughed, and then proceeded to methodically and politely walk the hierarchy of agencies with jurisdiction (sheriff, city police, state police, FBI field office, FCC, etc). I believe he called a member of Congress as well. Eventually somebody figured out that he wasn’t going…

> A guy on a team that I worked on detected one of those devices and called the university police (we were a tenant in a university building), who laughed, and then proceeded to methodically and politely walk the hierarchy of agencies with jurisdiction (sheriff, city police, state police, FBI field office, FCC, etc).

Since it took me a minute to parse: the guy on the team, not the university police, was the one who walked the hierarchy?

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