Are A3 & A5 events applicable to both intra/inter freq HO?

Specs & Protocol Testing
1

Hi Experts,
Whether A3 & A5 events used for intra freq HO only or for inter freq HO also same term can be used.
So are A3 & A5 events applicable to both intra/inter freq HO?
(Fundamental same for LTE & 5G both or diff?)

2

Usually, A3 for intrafreq and A5 for interfreq.

3

If 2 diff cell with same band but diff carrier freq, then can’t we say A3 for them?

4

In both LTE and 5G, A3/A5/A4 can be use for both intra freq and inter freq.
But sensibly:
A3 - used for Intra and Inter frequency both.
A4/A5 - used for inter ferquency.

We can surely use, rather its being use in some networks.

5

If earfcn is different, it should be interfrequency.
So for e.g. if we have 2 carriers in L18, so HO between them should be interfrequency HO.

6

We can use both but big concern for interFreq is interruption time during measurement gap.
By using A3 HO can be triggered at any rsrp level so will lead to more meas gap & may affect throughput.
But A5, we have certain threshold to start this measurement so we can control it.

7

Yes, understand but technically can we say A5 is also possible in intra-freq HO.

8

Not really.
Whether we use A3 or A5, m-gap is activated once A2 event is triggered.
Once UE enters m-gap it remain as long as A1 event is triggered or HO happens.
So throughput degradation is same in both A3 and A5 event for inter frequency.

Yes, as I said 3GPP do not have any guideline.
We can use any event at any HO.
But sensibly intra frequency should not be done with A5.

9

So one typical question is intra-freq HO what is correct?
(1) A3/A5 both
(2) None
(3) Only A3
(4) Only A5

So here answer is (1)?

10

(1) technically, (3) practically.

11

Only A3 cames in pictures were intra HO.

12

But how?
We discussed if 2 diff cell with same band but diff carrier freq, then can’t we say A3 as inter freq for them?

13

Sure it is possible.

I’m talking interFreq between A3 vs A5.
We can control A5 much better using the threshold.
For sure A2 is playing role here.

14

One cell L18 with xyz ARFCN & other cell L18 with abc ARFCN, then A3 can happen.
And it is called inter-freq HO.

Measurement gap comes in picture for only inter-freq HO & not intra-freq HO.
Simple understanding.

1 Like
15

Controling is better with A5, that’s true.
But throughput degradation due to m-gap, this is not true.

16

I believe same.

17

My understanding is that A5 is more safer and more conservative type handover (you need to be sure of target before you handover to it).
A3 is more aggressive handover where decision is made only source cell condition.
Both are applicable to Intra and Inter.
From L2600 to L1800 you can define A3 because L1800 will likely to be better than L2600.
Between same layers you can also define A3.
But from L1800 to L2600 you may want A5 to be sure that L2600 is really better condition.

18

Actually I second this idea this is the recommended approach by the vendors too.
Specially in the cases where you may have spectrum overlap (with different EARFCN) with the other operators on the target frequency.
A user in the handover region experiences increased interference.
Using A3 for InterF is more better.

19

Thanks, yes that is another benefit of using A3 less interference.