Move Voice Call from NR SA to LTE

Hi Experts,
For NR SA for A2 event is it used for sgnb release purpose only or used to trigger inter Freq/inter rat measurement as well like LTE?
For EPSFB is it by redirection or measurement based also possible for NR SA to move voice call to LTE?

In SA nothing called SgNB.
So A2 works exactly like in A2 in LTE.
That is for inter freq/rat measurements.

Mostly redirection…as there is no way to have voice call on NR.

I mean for SA is it used for rrc release as well when ue in poor radio condition like lte we have redirection on base of A2.

Ok mean b2/b1 based movement to LTE not possible for EPSFB.

Surely. A2 can be use for many purposes. Blind release and redirection is one of them.

It may be possible. But as we dont have option of voice call in NR…we have to latch to LTE…measerement is also possible but no one should use it. If B1 event not met then? we need voice call right?

Yes we need Voice call in LTE by EPSFB so thinking possible scenario for it.

  1. By measuring LTE dedicated by b1/b2
  2. Or by redirection

For VoNR once UE in poor coverage as of now

  1. UE move to LTE by psho
  2. UE move to 3G by SRVCC if LTE coverage not there

Hope so above understanding correct.

EPS Fallback can be:

  1. Measurement Based Redirection, which means, the UE will measure target LTE carriers in order to provide the gNB the best one. UE receives a release from NR and reconnects on LTE on the carrier indicated in the release. Measurements will increase the call setup time but may improve the call setup success ratio.
  2. Blind Redirection, which means, the will will be redirected by the gNB into a predetermined LTE carrier. UE receives a release from NR and reconnects on LTE on the carrier indicated in the release. The call setup time will be improved but the call setup success ratio may be reduced.
  3. Handover, which means, UE will measure the target LTE carriers and the IRAT handover will be commanded directly into the target LTE cell. The performance of this solutions relies on how good is your NR to LTE neighbor list.

Correct! If not mistaken, SRVCC has been introduced later in the R16 specs, so we may have to wait some time to see it available… well, the UMTS may be even extinguished by then :stuck_out_tongue: