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.

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11 days later

Hi GrandDixence First of all, a big thank you for the detailed description and the links to all pages.

It took me a while but I finally found time to read the whole thing in peace.

The solution with a private campus network seems to me to be the simplest. The costs for the hardware are certainly affordable. But if I understand this correctly, everything depends on the BAKOM license.

I also read through the Bakom license and was a bit shocked by the costs. The processing fees etc would still be affordable because they would be one-off costs. But as I understand it, the annual costs for the desired bandwidth can quickly shoot up because 1Mhz is charged at CHF 48 per year (min. 5 year contract). At 10Mhz that would be CHF 480 per year for wanting to preheat your car with the app. 🙂 And, I wouldn’t even know off the top of my head whether the 10Mhz bandwidth would be enough for our underground car park/area.

Or am I misunderstanding the calculation?

Here is an excerpt from the OFCOM guidelines and the link:

[https://www.bakom.admin.ch/dam/bakom/de/documents/Infomailing/nutzsbedingung-campusnetze.pdf.download.pdf/Nutzungsconditions%20für%20Campusnetze%20in%20der%20Schweiz.pdf] (https://www.bakom.admin.ch/dam/bakom/de/documents/Infomailing/nutzsbedingung-campusnetze.pdf.download.pdf/Nutzungsconditions%20für%20Campusnetze%20in%20der%20Schweiz.pdf)

IMG_0777.jpeg

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    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.

    Show original language (German)

    Ich bin ein als Privatkunde getarnter Swisscom-Mitarbeiter im Bereich Service Continuity.

    @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.

    Show original language (German)

    Installationen, Netzwerk, Internet, Computertechnik, OS Windows, Apple und Linux.

    @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/)

    Show original language (German)

    @GrandDixence You’re a genius! 🙂 Great thanks again for the explanation.

    Out of interest, have you ever implemented something like this for yourself/your settlement? You seem to have a lot of know-how. 🙂

    In any case, I will give feedback here on what Swisscom will say about my request.

    Wish everyone a happy Easter.

    Show original language (German)

    No, I haven’t realized it (yet). Is an ongoing craft project of mine:

    - Own mobile network with srsRAN_4G and LimeSDR-Mini on a Raspberry Pi 4 with Ubuntu 20.04 LTS

    Due to a lack of rain and (free) time, this craft project is not progressing.

    For this craft project, I holed up in the well-shielded civil defense cellar for testing purposes. And use the unassigned (green) frequency band in mobile radio frequency band 7.

    Downlink: 2685 to 2690 MHz

    Uplink: 2565 to 2570 MHz

    [https://de.wikipedia.org/wiki/Mobilfunkfrequencies\_in\_der\_Switzerland#2.6\_GHz\_[Band_7](https://de.wikipedia.org/wiki/Mobilfunkfrequencies_in_der_Schweiz#2 ,6_GHz_[Band_7)]

    Thanks to the thick walls and the low transmission power of the LimeSDR-Mini (maximum 13.5 dBm):

    https://wiki.batc.org.uk/LimeSDR_Mini_Output_Power_Levels

    13.5 dBm = 22.4 mW (milliwatts)

    It is highly unlikely that I will disrupt any radio application with this craft project.

    Show original language (German)

    NilsL

    My craft project “Own mobile network with srsRAN_4G and LimeSDR-Mini” has come to an abrupt stop. The LimeSDR Mini emits a decent 4G/LTE cellular signal at the upper end of Band 7:

    srsRAN in band 7 - radio spectrum analyzer.PNG

    The “manual mobile network search” from the (older) smartphone finds its own mobile network as “22899”:

    srsRAN in band 7 - select mobile phone manually.jpg

    But logging into this mobile network doesn’t work because I can’t find a way to allow all SIM cards in circulation to log into your own mobile network in the core network (EPC).

    The srsEPC program only allows the registration of SIM cards whose data is stored in the user database (srsEPC: user_db.csv). Self-issued SIM cards are required to store the SIM card data. SIM cards suitable for this purpose are available from Sysmocom, for example:

    https://www.sysmocom.de/products/sim/

    The srsEPC program is part of the open source product srsRAN and provides the core network (EPC) of a 4G/LTE mobile network. Other open source products for operating a core network (EPC) of a 4G/LTE cellular network suffer from the same SIM card problem. For example Open5GS:

    https://github.com/open5gs/open5gs/issues/611

    Show original language (German)

      My instructions for the craft project:

      - Own 4G/LTE mobile network with srsRAN_4G and LimeSDR-Mini on a Raspberry Pi 4 with Ubuntu 20.04 LTS

      can be found at:

      https://github.com/GrandDixence/CoverageMaps/blob/main/Own_Mobile Network/Installation-Guide_srsRAN_Ubuntu_20.04.m d

      My instructions for the craft project:

      - Own 2G/GSM mobile network with OsmoCOM and LimeSDR-Mini on a Raspberry Pi 4 with Ubuntu 20.04 LTS

      can be found at:

      https://github.com/GrandDixence/CoverageMaps/blob/main/Own_Mobile Network/Installation-Guide_OsmoCOM_Ubuntu_20.04.m d

      Maybe these instructions will help someone…

      Show original language (German)

      Hello everyone, I just received a call from Swisscom in response to my request, which I started with Swisscom via here:

      [https://www.swisscom.ch/de/business/enterprise/angebot/enterprise-mobile/inhouse-mobile-services.htm…](https://www.swisscom.ch/de/business/enterprise /angebot/enterprise-mobile/inhouse-mobile-services.html#tab=Inhouse)

      I spoke to a Mr. Heaven (I hope I got the name right) on the phone and explained to him my concern as described here in my very first post. He said that there is certainly a solution, but it would be expensive, i.e. it would cost several thousand francs if not ten thousand francs.

      However, he pointed me to the website https://www.myamplifiers.com/ which he had already recommended to other customers and this solution would have worked. This is a signal amplifier for 4G/5G/LTE.

      When I pointed out that active signal amplifiers were apparently not legal, which was already mentioned in this article, he said that it was the case with such small areas as e.g. Our underground car park of around 200m2 would be fine and will not be a problem.

      As I said, the gentleman was from Swisscom itself.

      I then inquired on the website https://www.myamplifiers.com/ and spoke to customer service. And I was offered this solution for our development: https://www.myamplifiers.com/de/repeater-257/.

      There is no assembly service, meaning you have to install the whole thing yourself. But all you have to do is assemble it, switch it on and you’re done. It doesn’t require an additional mobile phone contract or a SIM; it pulls the existing signal from outside into the garage and distributes it via the indoor antenna.

      What do you think about that? Are there any experiences?

      Show original language (German)

      I’m also surprised that this was recommended by Swisscom
      @Dolce83

      This repeater amplifies signals from all providers. Accordingly, you need permission from all providers.

      And for the sake of completeness, it should be mentioned that the responsibility ultimately lies with you. If disruptions occur, you are liable.

      The declarations of conformity are missing on the Myamplifiers site, perhaps I overlooked that (CE is not enough).

      Show original language (German)

      @WalterB
      The site is quite dubious, I doubt that it was created with the consent of the operators.

      There are also providers listed that do not have their own network.
      The business address is just a trading company with its headquarters in Gibraltar and a mailbox in Munich (86 companies in a small building)

      There are also the legal problems that I mentioned. Lack of declaration of conformity and the fact that you need permission from all providers.

      “If you import a mobile radio repeater from abroad, you are responsible for its conformity; importing non-conforming radio equipment is a punishable offense.”
      [https://www.bakom.admin.ch/bakom/de/home/geraete-anlagen/besondere-geraete/mobilfunk-verstaerker.html](https://www.bakom.admin.ch/bakom/de/ home/devices-systems/special-devices/mobile-radio-amplifiers.html)

      Show original language (German)

      @foobar

      I am of the opinion that you are not allowed to use the name “Swisscom” if it is dubious because Swisscom would certainly take legal action.

      There are also some users who use it with a Swisscom subscription.

      Of course I can’t check whether it’s fraud.

      Show original language (German)

      Installationen, Netzwerk, Internet, Computertechnik, OS Windows, Apple und Linux.

      You can ask Swisscom whether this is official. I doubt it.

      As for cheating… the amplifiers probably already work. It’s just clever marketing and the responsibility ultimately lies with the buyer.

      Show original language (German)

      @foobar As mentioned, this solution was offered to me by Swisscom itself.

      What I don’t understand is how such a small thing with such a short range can cause a disruption in the Swiss/cantonal/local mobile network (regardless of which provider). And how is OFCOM or Swisscom supposed to find out about this device?

      @GrandDixence how do you see the whole thing regarding myamplifiers.com?

      Show original language (German)