4G - 3G data connections issues

Hello Experts.

We are facing a data connection issues in Nokia 4G - ZTE 3G boundary area.

Whenever ZTE 3G network is reselected from Nokia 4G network, data services stop working even through it shows H+ symbol but no browsing.

Can anyone share possible reasons for this?

Admin note: this post was updated with image below.
4G - 3G data connections issues

Is this issue in a specific location?

Not specific to location.

Reported from several areas.

Ok, check if the cells are defined well in the Core.

Check LAC/TAC/SAC mappings.

Check if the issue is only from PS, and CS is working properly.

After confirming the above, now investigate if the issue is cell parameters related.

You can lock to 3G and check Data service at 3G ZTE end.

Check Alarms.

Also include RAC.

It must be the same as created on CORE PS NETWORK.

Actually TAC/LAC combination is there for CSFB to 2G.

And working OK.

You can make a trace or do DT on the site with issue.

Check the DSCP - MPLS - Core mapping.

DSCP is differentiated service code point among ran and higher element. If doesn’t much generally mentioned problem arises.

Picture is an example you must check between your element exact matching procedure.

4G - 3G data connections issues

Sure, this looks like the only option.

Actually data connection is OK after disabling and reenabling the data connection.

So I don’t think CoS is actually an issue here.

Can anyone confirm whether IP change occurs when a UE is redirected from LTE to 3G or 3G to LTE?