Signal redirection to the underground car park

Interesting question that I would also be interested in solving. My Tesla Model Y is “woken up” via mobile communications, probably via SMS and only then connects via WLAN. Our MFH is built like a nuclear bunker and the first 3 floors including the parking garage are completely underground in the rock. For the load management of the Zaptec Pros, we of course have several WLAN APs in the underground car park, whose network I also have access to. So if I want the Tesla to always stay connected to WiFi, I have to activate Sentry Mode (environmental monitoring with cameras and sensors), which in turn uses unnecessary power. Due to this “limitation”, intelligent charging, for example via the CKW Smart Charging app, is not possible at all, as the car goes to sleep after around 30 minutes and can no longer be woken up without mobile communications. If we move towards load management, smart charging and variable tariffs in the future, we will need a corresponding solution. At Tesla this would simply be to leave Sentry Mode active, which is not an ideal solution for data protection reasons etc. When someone approaches the car, it also starts to light up etc.

Hello @Dolce83 @millernet

Maybe this could be the solution 😉

Tschamic

There was recently a discussion about this problem. Not a solution yet, but at least a place to start. It probably wouldn’t hurt if everyone affected reported it.

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@Tschamic wrote:

Hello @Dolce83 @millernet

Maybe this could be the solution 😉

Tschamic

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Possibly But Bakom or their representatives suddenly come to the door, confiscate the repeater and present an expensive bill.

I would go the safe route that @HP linked.

Yes, the car wakes up briefly about every 4 hours and connects to the network via WiFi or cell phone, but then goes back to sleep mode. In order to keep the car permanently connected to the WLAN, Sentry Mode must be active and with it practically all of the car’s electronics. In sleep mode it somehow still maintains a connection via LTE and is woken up via SMS or something similar, which takes about 20 seconds. The car can then be controlled via the app. A persistent WLAN connection is not provided in sleep mode.

Of course, you can “put together” a passive mobile phone repeater for the underground car park using the existing 4G antenna. The only question is whether the cell phone signal received by the cars via passive cell phone repeaters is strong enough. That’s why you have to do some calculations beforehand, as described in article no. 22 under:

[https://community.swisscom.ch/t5/Archiv-telefonie/Passive-Signalumlenkung/m-p/668182#M61945](https://community.swisscom.ch/t5/Archiv-telefonie/Passive-Signalumlenkung/m-p/ 668182#M61945)

has been described in detail.

Has the “official” route already been tried?
[https://www.swisscom.ch/de/business/enterprise/angebot/enterprise-mobile/inhouse-mobile-services.html#tab=Inhouse](https://www.swisscom.ch/de/business/ enterprise/offer/enterprise-mobile/inhouse-mobile-services.html#tab=Inhouse)

There are different sized solutions, I think it should be possible.

Especially when it affects multiple parties.

Under no circumstances should you use any funny internet femto cells or mobile repeaters.
If it leads to errors and the whole thing is discovered OFCOM is very sensitive.

@StefanSch

It was mentioned above that there is no WiFi in the cars, only mobile communications?

Then your link would be the optimal solution.

However, the electric cars cannot access WiFi because the electric cars do not have a WiFi module installed (brands: Genesis GV70, Mercedes EQC, VW Tiguan). The cars only have a GSM module (hope that’s the right term), meaning they can only access the Internet via a mobile phone network.

Please let me know, things like this are always good to know!

@Dolce83 wrote:

And, off the top of my head, I wouldn’t even know whether the 10Mhz bandwidth would be enough for our underground car park/area.

Due to a lack of computing power, the Raspberry Pi 4 only supports a maximum bandwidth of 5 MHz. Quote:

« Limited cell bandwidth (currently 5 MHz) »

Source:

[https://docs.srsran.com/projects/4g/en/latest/app\_notes/source/hw\_packs/source/index.html#package-1](https://docs.srsran.com/ projects/4g/en/latest/app_notes/source/hw_packs/source/index.html#package-1)

The maximum data transfer rates that can be achieved with a 5 MHz bandwidth can be calculated here:

https://www.cellmapper.net/4G-speed

\=> Bandwidth: 5 MHz (25 resource blocks)

\=> Downlink modulation: 64 QAM (realistic with good reception)

\=> Uplink modulation: 16 QA (realistic with good reception)

\=> MIMO 1×1 SiSO (only 1x transmit antenna and 1x receive antenna)

Whether that’s enough for the vehicle fleet needs to be tested. I guess: Yes, it’s enough.

The Raspberry Pi 5 has significantly more computing power than the Raspberry Pi 4. More computing power = more bandwidth in mobile communications. With the “EDATEC Raspberry Pi 5” housing, the Raspberry Pi 5 should be properly passively cooled. I can only advise against active cooling with a fan.

[https://www.martinrowan.co.uk/2024/02/edatec-raspberry-pi-5-fanless-enclosures/](https://www.martinrowan.co.uk/2024/02/edatec-raspberry -pi-5-fanless-enclosures/)