Single Radio Voice Call Continuity (SRVCC)
HTML-код
- Опубликовано: 4 сен 2016
- A brief overview explanation of how SRVCC works. This specific example assumes that SRVCC procedure will make sure LTE (PS + Voice) call is seamlessly transferred to UMTS successfully.
What a good communication skill & LTE knowledge you have sir !! I also want to speak such a fluent English.
Great explanation
Hi, what happen to the RAB assignment flow. Is it done during relocation flow or after SRVCC HO a new RAB setup assignment will take place? (for both CS & PS sessions in the RNC)
Hi Azar,
few questions:
1. will the P-GW continue to root both the ps and cs data to to the umts network while the call is still in session, i.e. are both sessions still anchored to the P-Gw for the remainder of the ps and cs calls?
2. why does the p-gw not talk directly to the msc to ensure the Voip call is reformatted to now work on the cs umts network, or does the IMS complete this?
3. when the ue sends the required event to highlight srvcc is required does the ue not complete any measurements (measurement gap) to inform the lte network that there is indeed umts coverage in the area to hand into or is the handover blind just like with csfb?
best regards and thanks.
Dave
Hi David,
Below are the answers to your questions.
1. will the P-GW continue to root both the ps and cs data to to the umts network while the call is still in session, i.e. are both sessions still anchored to the P-Gw for the remainder of the ps and cs calls?
Ans: PGW will not continue to send data to UMTS network. You are right in bringing up this question. There is a shortcoming in the last slide. I have updated the last portion of the picture and it looks like this now. See blow
www.techtrained.com/srvccfinal/
Thank you for pointing that out.
2. why does the p-gw not talk directly to the msc to ensure the Voip call is reformatted to now work on the cs umts network, or does the IMS complete this?
Ans: Voice Call is being controlled by IMS, so IMS completes it. IMS updates its leg from previous network which was LTE to UMTS network in this case.
3. when the ue sends the required event to highlight srvcc is required does the ue not complete any measurements (measurement gap) to inform the lte network that there is indeed umts coverage in the area to hand into or is the handover blind just like with csfb?
Ans: That is a great question.
The simple answer is. No UE will not do measurements on UMTS itself right away. Before UMTS measurements, UE always has to go through event A2. If you need details, keep reading below.
DETAILS:
When UE is getting connected to eNodeB, UE will just inform about its ability to the eNodeB during intial attach procedure if it can support SRVCC or not ( by indicating FGI bit 27 ). as shown in UE support for SRVCC picture in the blog here . www.techtrained.com/srvcc/
Now that being said. UE will send event A2 measurement ( event measurement which is send only when UE is in bad coverage of the serving cell of LTE) when serving eNodeB coverage is going bad.
Its up to the serving eNodeB after receivivng A2 measurement report to tell the UE , if it needs to do measurement on UMTS or not.
Remember in LTE , UE cannot do measurements on any different frequencies or different technologies without serving eNodeB's approval.
If serving eNodeB thinks based event A2 measurement that handover to UMTS is needed (because bad LTE coverage is detected) , then it will inform UE to start doing measurements on other UMTS neighboring cells. In that case, UE will start to do measurement for event B2 . Once measurements are send by the UE for event B2 . Then SRVCC procedure will take place.
Hope that helps, Thanks for the question.
Do you have a call flow for srvcc with CS HO type only?
Hey , In Phase 2 , Forward relocation complete message is sent by SGSN to MME not the other way round as you have explained .
Thank you for the correction Avinash
Is there any timer, will start from begining to complete the task In IRAT HANDOVER where Mobile resources should be deleted of Lte.
Hi Azhar,
It was very nicely covered .Thanks for the effort that you took time and delivered.
I had request can you please share on IMS side which component and node would take care and how the call flow would be.
Mg-w is a part of legacy network
There is no use of prcf?
Hi Azar
The First contact for the IMS server is P-SCSF which is available in LTE net Work. In case of SRVCC how SGSN contact to p-CSCF.?
Thanks
Nayak
Nayak, If you take a look at 3G architecture. SGSN has ability contact the External network via another node. IMS is placed where you see External network, so SGSN will have access to P-CSCF. Hope that helps
Brother need your more videos ....
i think you mean MGW-CF not MGW