UE can not attach to NR leg

5G NR
,
1

Hi all,

I’m deploying DSS (NSA) and I have a question related to NR leg setup.
The picture below, UE sent Measurement report to the network, but UE was still not attach to NR leg.
I don’t know why was that, does anyone have any suggestions/ideas for this case?
Thank you in advance!

image
image730×590 125 KB

1 Like
2

Which vendor?

3

Assuming this MR contains NR measurements, since you are seeing no RRC Reconfiguration trying to add the PSCELL, there is something wrong on the eNB/gNB side. Things like, missing or wrong gNB neighbor relationship, or even other parameters related to the NSA configuration. Verify your baseline.

2 Likes
4

Thank you for your help! I will do double check that!

5

maybe due to our relation 4G/5G

6

This is also common case when UE is 5G capable, but not DSS capable. Check UE capability information for rat-Type: nr and eutra-nr to see if device is DSS capable.

2 Likes
7

Try to search in MR message the B1 event like this:

…eventId
…event-B1-NR-r15
…b1-thresholdNR-r15
…nr-rsrp-r15 — 0x15 (51)

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8

Below is sample decoding of “RRC connection reconfiguration” for measurement configuration and DRB configuration:

{
measObjectId 2,
measObject measObjectNR-r15 :
{
carrierFreq-r15 643333,
rs-ConfigSSB-r15
{
measTimingConfig-r15
{
periodicityAndOffset-r15 sf20-r15 : 18,
ssb-Duration-r15 sf5
},
subcarrierSpacingSSB-r15 kHz30
},
quantityConfigSet-r15 1,
bandNR-r15 setup : 78
}
},
{
reportConfigId 3,
reportConfig reportConfigInterRAT :
{
triggerType event :
{
eventId eventB1-NR-r15 :
{
b1-ThresholdNR-r15 nr-RSRP-r15 : 46,
reportOnLeave-r15 FALSE
},
hysteresis 2,
timeToTrigger ms80
},
maxReportCells 4,
reportInterval ms120,
reportAmount infinity,
reportQuantityCellNR-r15
{
ss-rsrp TRUE,
ss-rsrq TRUE,
ss-sinr FALSE
1 Like
9

In theory, if it is not capable, no B1 should be configured… but that`s theory… eNB/gNB SW is not 100% yet, especially for DSS, so I agree with you, no harm on checking if the UE is in fact DSS capable :slight_smile:

2 Likes
10

Thank you everyone, I have some ideas to do now!!! :blush:

11

From traces, does the eNB send SgNB addition request to the gNB or not?

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12

Sorry Ibrahim, I did not get the traces :frowning_face: :frowning_face:

14

The problem here is after sending MR report, UE did not receive RRC conn recfg to obtain infornation about 5G cell. This failure happened at enb or gnb side in 5G SCG ADD procedure, so to analysis detail, it’s better to have X2 trace log.
I think the problem may be due to some of below cause:
1, enb not send sgnb add request
1.1, enb not configure corectly neighboring 5G cell
1.2, enb configure gnb not support NSA
1.3, X2 link between enb-gnb have problems
1.4, enb’s x2 links reach maximum as vendor specific, so enb not send req to target 5g site
1.5 X2-u ping failed

2, enb already send add req but gnb not response or reject
2.1, transmission network failure between gnb and sgw, such as gnb ping to sgw failure
2.2, some parameters in add request not supported by gnb
2.3 dedicated preambles failure by 5G gnb

1 Like
15

Many thanks for your support!!!

1 Like
16

I am also having the same problem as you.
Could you tell me how you solved this problem?
it helps me a lot.

17

Could you tell me how you solved this problem?

18

check below possible causes:

1.Neighboring LTE cell configuration is abnormal (missing or PCI conflict).
2.The X2 link to the target site is abnormal.