Measurement Gap Length (MGL) in 5G

I think that, if your network don’t have FR2 then 12-23 gap pattern ids won’t be configured by network.
Not sure, maybe otherwise possible.

Yes agree, but UE must report its capability for all supported IE.

I checked in detail for gap 12 to 23 usage:

  1. Serving cell to be FR2 mandatory.
  2. Measurement purpose to be FR1, FR2, non NR RAT .

Then only 12 to 23 gap pattern used. It’s concluded these gap not used for addition of SCG by B1 event.
But used for inter Freq HO between NR cell or from NR cell to non NR RAT.

There might happen that NW shouldn’t set gaps that aren’t compatible with # of SSBs?
It’s not mandatory to use all 64 SSBs, as per SSB mitmask config options.

Ok, however if it’s not mandatory to measure all 64 SSBs, then how UE will be able to know that which is the best beam?

What he’s saying is that for some NW not all 64 SSB are transmitted, so less will be configured for meas gap too.

Network doesn’t need to send or configure all 64 beams.
It can set 8 as an example.
Beam refinement will probably happen later based on CSI-RS.

Ok, that may be possible.

The node that giving the measurement configuration should give the suitable gap for the required SSB beams to be measured. For case of 1.5 ms, it should be used if total number if beams is less than 64 or beams to measured could be limited by configuration (SSB to measure)

Not configuring all 64 is true.
But UE doesn’t know which 8 are configured, so it would need to sweep all.
It would need more than 1 ms provided in mgl to scan this, right?

UE knows which Beams to monitor based on SSBConfigMask.

Details of SSB bitmask are in RRC Conn Reconfig sent by anchor cell BEFORE measurements fo NR.

Details here of how bitmask looks like:

http://sharetechnote.com/html/5G/5G_SS_Block.html

I have doubt with 2nd requirement (Measurement purpose to be FR1, FR2, non NR RAT).

I think 12-23 are just for inter freq HO between NR cells belongs to FR2 only, as FR1 support 3/4/6 ms MGL and non NR RAT(E-UTRAN) support MGL of 4/6 ms only.

This does make sense!
If we are already providing SSB indexes, UE won’t need a high MGL value.

I checked in specs table where purpose mentioned for measurement as well from there I taken.
But at least 1 think clear, gap 12 to 23 not mean for SCG Addition.
Now for inter Freq HO if required between FR 2 cell, then we have option of absolute SSB measurement to average out RSRP of all SSB and then take decision for Handover.

So you mean to say MGL not required for HO between FR2 Cell?

It depends how network configured it.
I mean your question how UE will measure 64 SSB beam in 1.5 ms can be taken care by average value of SSB per cell by a3 or a5 event.

Let’s assume cell A with 64 SSB beam and cell b with 64 SSB beam.
UE latch on cell A with SSB beam index 30 then radio condition of cell start degrading then UE will report MR to network as average SSB value and if target cell satisfy configured threshold value, i.e. A3 or A5 then HO will happen and UE context transfer to target cell.

Yes that’s possible if both Cell A and Cell B belongs to same FR2 frequency, but what if cell A and B belongs to different FR2 carriers?
Will the above condition be valid in this condition as well?

Yes basically for inter Freq HO as well valid.

Others can give there view. As per my understanding Measurement gap required for inter Freq/ inter RAT Measurements only.

This is right.
Gap 12-23 only used when serving is FR2.
Neighbor can be FR1/FR2/Non NR RAT.

I am just following the legacy concept from 4G where measurement gap was required to measure inter freq and inter RAT.
So based on same concept in 5G, measurement gap required for inter freq and inter rat as well.
So for example there is FR2 band 257 with two carriers F1 and F2 which belongs to two different cells namely A and B.
Now when UE is on F1 and wants to measure F2, then what i believe, UE required measurement gaps.