Hi Experts.
What will happen if A3 is triggered & immediately A1 is also triggered?
Will HO happen?
If A3 is triggered & neighbour cell is unavailable in NRT, will it cause HO failure?
Reference (help) image sent later in discussion:
There are timetotrigger parameter to restrict ping pong handover…how it is possible immediately A1 triggered…after A3 ue will attempt for HO based on A3 measurements…
timetotrigger is for a specific event is not between events.
So it may happen that UE reports 2 events at the same time: A1 and A3.
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A3 means nbr is better than source.
It does not matter source it good or bad.
So if A3 triggered UE should attempt for HO.
Yes, true.
But hold on, what event was reported first? A3 or A1?
A1 for cancellation if it trigger and ue failed to send A3 MR for time to trigger expired.
Then it can possible.
A3 first and A1 then.
Ok, thanks.
A1 is used for cancellation of interfrequency or irat measurements, i.e. if A2 happens.
However if A3 measurements is there, A1 should not stop HO req message.
A3 is subject of admission control on target eNodeB.
This is one reason you may not see it happening, even if reported.
Complete Detail of Intra-LTE Handover procedure using X2 interface
If neighbor is unavailable in nrt, if UE MR based ANR is on then ANR will add that neighbor in nrt and make HO.
If for some reason, neighbor is not getting added in NRT then HO will fail.
So after A3, A1 normaly shall not report, if reported then A3 will cancel, is it?
In that case handover preparation will fail, with appropriate handover preparation fail msg.
In my opinion if A3 reported there will HO req msg and successive procedure, in any case if ho failed…then next action will be based on succesive measurements.
In general A1 is used to negate A2. So if A2 occurred, UE will start measuring other frequencies (say irat frequencies). Now in between if A1 occurred it stop measuring other frequencies.
However A3 is only check if nbr is better than source, if so it will try to handover unless handover is failed.
If you have see any other behaviour share the details layer 3 message snaps if possible.
Why we are linking A1 and A2 together?
You can use A1 without A2 as well no limitations in specs.
I am not linking, I am saying usage/purpose.
Obviously there can occur A1 without A2 or any other event.
But if A2 triggered and then A1 triggered it indicates it UE moved to good coverage again so stop measuring other frequencies.
If it is only A1…then UE will not do anything…just enjoy good coverage.
And obviously send A1 measurements reports to eNB.
It’s only vendor implementation.
What I am think as A3 occured & just after that A1 occured again, is it also possible than neighbour becomes offset better & once neighbour become unavailable due to some reason immediately A1 reported again.
But in generally as hys provided to avoid ping pong in network once A3 reported, UE does not report A1 then.
What happens if value of A1 = A2?
Race condition.
We have set A1/A2 = -43 dBm on small cell operating on 2300 band for GBR traffic to reduce mute call.
This small cell having good FDD (1800/850) overlapping.
But mute call increased on small cell post this setting.
Idea was to shift maximum gbr traffic on nearby macro site which is operating on TDD/FDD band.
Let’s say A3 event trigged & suddenly neighbour cell becomes unavailable due to any reason (extreme high speed mobility/ neighbour cell down sudden) then what event UE may get that time, it can be any or A1?