# TTT for inter Freq measurement

Hi Experts,
I have one question regarding TTT for inter Freq measurement.
For e.g. if TTT is 320 ms, MGL= 6 ms, MGRP is 40 ms , then in 320 ms UE has to collect 320 / 6= 54 measurements and total time taken will be 54*40 ms.
Is my understanding correct?

No its not like that.
TTT 320ms means once event trigger condition is met, that condition should hold true till next 320ms. It consist of 320/40 measurements of 6ms each.

That means the UE will get 8 opportunities to measure interfere neighbours if TTT is 320 ms. But the question is In one opportunity, the UE will get 6 ms of time to measure inter Freq neighbours. So total time UE will in all the 8 opportunities = 6* 8 = 48 ms. But our TTT is 320 ms.

TTT is not only measuring time. Its total time starting from event trigger condition is met.

Ok, I get the concept.
That means in all the 8 opportunities if the Inter Freq Nbr RSRP > Threshold (say A3 with offset), that means trigger condition is satisfied (since 8 × 40 = 320 ms).
If any of the 8 opportunities, if inter Freq Nbr RSRP < Threshold (say A3 including offset), the event will not be triggered.
Is it correct?

6ms Gap time, but actual measurement time is only 5ms.
Pss/Sss periodicity is 5ms transmission.
Inter-freq measurement, UE will measure neighboring cell’s PSS/SSS, not CRS.

Good point.
Then how UE measures RSRP of nbr cell?

Yes, correct.

UE measure both pss/sss as well as CRS.
UE has to report PCI as well as measurement RSRP/RSRQ which comes from CRS measurement.

So it calculates PCI from PSS and SSS in 5 ms (in worst case) and in next TTI it measures CRS of that PCI.
That’s why I think measurement gap is 6 ms.

UE can measure CRS in all 6 TTIs.
Logic behind 6 ms MGL can be.
UE should get PSS/SSS both which are 5ms apart, within MGL.

Ok. I’m saying about worst case scenario.
Support there is only one inter Freq Nbr and measurement gap started at sf 1.
So in that case UE will read PSS/SSS at SF 5 and read CRS at SF6.