How to check which event is actually taking place in case of intra-LTE and inter-LTE handover?

Hello All

How to check which event is actually taking place in case of intra-LTE and inter-LTE handover?

I have some confusion with A3 & A5 Event in LTE.

Admin note: this post was updated with image below.

Hi, for Ericsson case, you can check by parameters if A3 or A5 event is configured for InterFreq HO, and From what I know, IntraFreqHO is always condigured with A3. The default case is as I comment below, and you can check or modify it with interFreqMeasType parameter (only for InterFreq case in Ericsson 4G network)

The most common case is that:

  • A3 event is setting for IntraFreq HO: because it triggers when one neighbor cell level is above the serving cell level.
  • A5 event is setting for InterFreqHO: because it triggers when best server level is below threshold 1 and neighbor cell level is above threshold 2.

Some years ago we made a trial setting A3 for InterFreqHO (and other related parameters), only for special urban cases where we expected traffic increment for LTE low bands load, reducing congestion on high bands.

Finally, I’m almost sure that you can check if A3 or A5 is taking place by reviewing Drive Test logs too.

Actually all threshold parameters are configured in the site.

The case is Nokia.

Can anyone from Nokia please comment, exactly which parameter distinguish A3 / A5 Event?

I understand that in case of Intra-freq, there is no requirement of A1 & A2 event to trigger A3 event.

Yes, that is the most common case: IntraFreq by A3 without A1/A2 requirement.

Check mobility slides for Nokia Algorithm.

I went through the Nokia document.

It says A3 is used for Better Cell and A5 is used for Better Coverage.
And I check in the site both are actually enabled.
Is it required both to be enabled? If not, which one is better?

I think if we enable better cell only, it covers the cases of better coverage as well but no of handover attempts will increase.
Can anyone please comment further?

You always need to measure for Intra or Inter-Freq.

With A1 event you start measures for Intra-LTE measurements.

A3 and A5 can be used for both cases (Intra & Inter Freq HO), according to your mobility strategy you can use them as required.

Isn’t A1/A2 applicable only in case of Inter-RAT or Inter-Freq cases?

Mobility is done through a sequence of thresholds & hyst values.

When a UE is degrading it RSRP / RSRQ levels, the first step to trigger Intra-LTE Measurements.

Yes, but I understand intra cells are always measured by UE, so no event required to trigger it.


Neighbors are only measured when A2 is reached.

A1 is used if the radio conditions are improved, so the UE stops measurements.

Measuring neighbors requires resources from UEs, that will consume more energy from it.

So less battery life.

Additionaly when InterFreq measurements are triggered, you increase noise on your network and reduce Scheduling allocation to that UE.


Threshold1a is for triggering intra freq meas.

Intra freq use A3 offset plus hys.

For If, use A5, that’s it.

For A5 there are 2 thresholds, thresh1 for serving cell and thresh2 for target cell rsrp.

Of course UE should not enter meas gap all the time.

Therefore you need to set A1 / A2 for start stop measure.

You can’t enable a3 and a5 for either intra or inter at yhe same time.

Didn’t get threshold1a but threshold1 is there.

Actually everything is enabled in our network… Not sure whether working or not.

:relieved: there are multiple a3 and a5 events in Nokia.

You can have A3 & A5 events for Intra or Inter Freq at the same time.

For A3 there are Intra and Inter Freq parameters.

Also for A5 mobility you can use it on Intra and/or Inter-Freq.

Yep, for Nokia is threshold1 (LNCEL).

And there are many features for mobility Intra & Inter Freq where you should enable the proper switchs, thresholds, hysteresis, Time To Triggers, timers etc.

Yes exactly.

But at the same time for INTRA FREQ handover you can enable A3 or A5, setting thresholds does not mean they are enabled.

You need to enable switch in the correct MO.

Do UE need to enter measurement gap for intra-freq as well?

No in LTE, could be YES in NR if target freq is out of active BWP.

For Ericsson case, start of IntraFreq measurements depends on “sMeasure” parameter configuration.

I’m not sure if for Nokia case “threshold1a” has some relation with “Event 1”, remembering that in general “Event 1” is used to stop interfreq-inter RAT measurements.

threshold1 is related to sMeasure.

tthreshold2a is used to stop interfreq / RAT measurement in case of Nokia.