UE in 2 different networks simultaneously

[scorpion]

Lets assume two operators are having national roaming agreement with each other.

Is it possible that a UE can be in 2 different networks simultaneously.

One in CS Network of Oper-A
One in PS Network of Oper-B

Can the UE make Voice Call and PDP Session at the same time ?
The observation says data session is failing...but UE is in ATTACHED condition

Any observations ?

What sotrt of handsets are aving this problem ?

[fon909]

Hi,

In my opinion UE can't be present in two different networks simultaneously for any service for following reasons;

1. Will create billing issues
2. UE able to latch to just one frequency (not sure if even advanced MIMO enabled UE's can do that)
3. HLR will not allow a single IMSI to be active in two different PLMNs simultaneously.


Roaming comes into effect when a sim of operator A is in a situation where signal condition exceeds all the roaming thresholds and now the only option is to latch on the frequency of operator B.

However, on the same network with the help of Multi-RAB services UE can make both CS and PS calls simultaneously.


Hope this helps.

[jan74]

Hi,

In my opinion UE can't be present in two different networks simultaneously for any service for following reasons;

1. Will create billing issues
2. UE able to latch to just one frequency (not sure if even advanced MIMO enabled UE's can do that)
3. HLR will not allow a single IMSI to be active in two different PLMNs simultaneously.


Roaming comes into effect when a sim of operator A is in a situation where signal condition exceeds all the roaming thresholds and now the only option is to latch on the frequency of operator B.

However, on the same network with the help of Multi-RAB services UE can make both CS and PS calls simultaneously.


Hope this helps.

Agreed. I cant see how you can be in 2 different HLRs simultaneously.

[wolverine]

It is not possible for the simple reason that the UE can only be camped on one cell at a time. One frequency, reading one BCCH etc.

[FrankPintor]

I assume this is a real case? Not just a thought experiment?

Not much point in looking at this from the network point of view, it's a UE error. From the OP's description it looks like when the UE roamed from network B onto A, it did the location update for the CS domain for A, but for whatever reason didn't attach to the PS domain on A. The UE is in the PS attached state, but of course "the observation says data session is failing", any attempted PS session will fail because of the invalid P-TMSI (which the UE got on network B).

If you can identify the failing UE brand (maybe by tracing and collecting IMSIs?) you'll have found your problem. Finding the solution might be a different matter.

[firstmaxim]

I assume this is a real case? Not just a thought experiment?

Not much point in looking at this from the network point of view, it's a UE error. From the OP's description it looks like when the UE roamed from network B onto A, it did the location update for the CS domain for A, but for whatever reason didn't attach to the PS domain on A. The UE is in the PS attached state, but of course "the observation says data session is failing", any attempted PS session will fail because of the invalid P-TMSI (which the UE got on network B).

If you can identify the failing UE brand (maybe by tracing and collecting IMSIs?) you'll have found your problem. Finding the solution might be a different matter.
Good Analysis! Agree there is no way a UE can be attached to two different networks simultaneously. The UE can camp only on a single cell at given time.

[D33T0X]

An UE can only be attached to one network at a given time... if anything else was seen in measurements then the logging software gave errors/UE blocked itself.

[scorpion]

Hi FrankPintor,

Your analysis is great.

Mainly the observation same as you have posted. Eventhough I havent put my deep analysis inside, my worry why the UE is not attaching in to the PS mode of Oper-B and keep remaining in Old SGSN Attached mode.

The queries are still open like...

The PS Mode is allowed in Oper-B. I am sure UE might have attempted there and still remaining in old SGSN.

Could be the new SGSN didnt accepted...
RAU Failure ?
Or the GPRS Attach itself not responded ?

Any other observations ... ?