How does voice calls work in limesdr for lte

Projects LibreCellular
1

hello everyone

sorry if the question sounds basic ,but assuming that if you did a 4g setup with a limesdr and a opensource software for the core network its not going to be using volte for voice calls right?
so is it going to be using CS-fallback to 3G or 2G ? or is there something else

2

It’s no different to any other LTE network in that:

  1. It will use CSFB, if you also have a 2G or 3G network and have configured this;
  2. It will use VoLTE, if you also have an IMS and have configured this.

Both are possible. ISTR that Osmocom 2G has successfully been used for CSFB, with I think srsRAN 4G. For VoLTE with open source people typically use Kamailio, with Open5GS for the EPC. There is a Docker image which provides a shortcut to getting a development environment up and running:

3

hi Andrew

thanks for the response ,I’m new to this sdr stuff so pardon my basic questions

you mentioned 2 different open-source EPC software to do each ,is there no software that can do both so i can toggle between the to to test the voice quality in CSFB vs VoLTE using the same devices for example

4

It’s not that simple.

If you want CSFB you will need a 2nd SDR and to run the Osmocom 2G stack, then configure both this network and the 4G one so that fall-back works. You will have two separate stacks, complete with their own base stations and core networks.

If you want VoLTE you will need a 4G network and to configure an IMS. When doing this people tend to use Open5GS for the EPC and then Kamailio for the IMS. But there are some more details to take care of and you can find these online.

If you want to do both, you will need both of the above. In other words:

  1. A functioning 2G network with its own BTS/TRX, BSC and core network.
  2. A functioning 4G network with its own EPC/core plus IMS.

A 2G core is different to a 4G core. You need both and as far as I know you will need to provision subscribers in both.

This is nothing to do with SDR really and a question of mobile network architecture and the questions would be much the same if use COTS non-SDR equipment. The best place to ask questions is the Osmocom and srsRAN etc. communities. Once the SDR is providing network service it is no longer an SDR matter and rather instead one of RAN/Core/IMS configuration.

5

hello Andrew
will try to ask in other forum ,thanks for the help