nano3g ip.access femtocells and transcoding

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Mykola Shchetinin mykola at kingmuffin.com
Fri Dec 14 09:51:18 UTC 2018


Dear Osmocom community,

Did somebody try to use nano3g ip.access femtocells and Osmocom system with
external call handling? What I am trying to do is to make calls work between
VoIP phones connected to PBX and UEs connected to Osmocom system. I've tried two
PBXs: Kamailio with rtpengine and Asterisk. Signalling worked good between VoIP
phone and UE with both PBXs; calls between two UEs registered on Osmocom system
worked good also... But I fail to do transcoding (calls between VoIP phone and
UE). The problem is that it is unknown which codec is used by nano3g ip.access
femtocell.

So, the question is: Do you know what codecs were used for speech in your setup
with nano3g ip.access femtocells? Or do you know how to find out that
information? (It was stated by ip.access that they use AMR but I failed to match
AMR specs with RTP payload that was sent by femtocell...).

I would be very grateful for any ideas.

Kind regards, Mykola



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