Advanced: Voice in 4G: CSFB, VoIP & VoLTE

[@kavya-1434]

very good training brother and very useful.. I really appreciate your presentation skills

[@3G4G5G]

Thank you.

[@saj561]

Really man. you did great job by putting information so simply.

[@3G4G5G]

Thanks Sanjay, comments like keep us motivated. Please help us by sharing and promoting the channel.

[@vigneshvicky1062]

Great work. Really worth watching it .

[@horizonbrave1533]

Thank you so much! Been watching your videos on repeat for the last week now! Also this idea that 4G didn't have the "voice part" now makes so much sense, when I used to make calls and I have attached to the LTE 4G network, the service would drop from "4G" and switch to HSPA+ or something lower. Now I know why! My question is, that at 10:00 you mention how CDMA and GSM each had their own methods of dealing with the CSFB. But is it fair to say that CDMA was always less popular and supported than GSM? If so, why did the SVLTE for CDMA do better than the SGLTE? Plus, CDMA had the advantage of SRLTE...So why was CDMA so much less popular than GSM?

[@3G4G5G]

CDMA was a closed ecosystem by Qualcomm, hence others just went around and invented other technologies. SRLTE is not good at all. It means while my call is ongoing, I cant access data. This would be an issue if you were driving with a SatNav app like Google maps or Waze and you start a call. You wont be able to get any traffic updates, etc. while the call was ongoing.

[@horizonbrave1533]

Ahh I see! THanks, I really appreciate you following up with answers to the questions here my friend!

[@horizonbrave1533]

Hey 3G4G, Anotherquestion, in my daily work, I noticed that some call traces in Wireshark show "SRVCC". I looked it up and it means "Single Radio Voice Call Continuity". Reading a little about it, is this the same as CSFB (call fall back) ?

[@3G4G5G]

SRVCC is continuation of VoLTE call on 2G/3G network (mainly 3G) after handover from 4G to 3G/2G. In CSFB, The Circuit Switched core is used whereas in SRVCC, Packed Switched core is used. See this: www.slideshare.net/eXplanoTech/an-introduction-to-voice-and-sms-in-lte-networks-70681388 - slide 50 onwards.

[@horizonbrave1533]

Hmm... so at 22:40, you say that 4G VoLTE, it uses Voice as data...and it has it's own separate signaling to the IMS core. So just to make this clear if the Voice (in red on the slide) were being sent over the default data bearer (in gold on the slide), then that is the method for OTT clients like Skype and Viber? BUT because the voice now has a separate 3rd bearer, than that is what makes it VoLTE? Does the signaling method remain the same for OTT usage like Skype and Viber, and with VoLTE calls?

[@3G4G5G]

Correct about OTT but VoLTE has signalling (Blue) and Data (Red) part. By Data I mean voice as its just IP packets.

[@suchandra252]

nice work

[@brahimbenhammou4867]

too much ads bro!

[@3G4G5G]

That's KZbin trying to convince you to become a premium member. Nothing to do with us.