Is RAB Exists in FACH/PCH State?

[jayk]

Hello Experts, Please share your views about existence of RAB in PCH/FACH state. All ideas are welcome.
Regards, Jack.

[boring]

In CELL_FACH there is a RB, RAB (=RB + Iu_bearer) and PDP context
In CELL_PCH & URA_PCH the RB is suspended and there is a RAB (the Iu part is still fully operational) & PDP context. the moment a user wants to exchange data with the network, the UE RRC_state moves to CELL_FACH and as a result an RB is reactivated.
thanks

[jayk]

In CELL_FACH there is a RB, RAB (=RB + Iu_bearer) and PDP context
In CELL_PCH & URA_PCH the RB is suspended and there is a RAB (the Iu part is still fully operational) & PDP context. the moment a user wants to exchange data with the network, the UE RRC_state moves to CELL_FACH and as a result an RB is reactivated.
thanks

Does bandwidth kept occupied at Iu part at IuPs interface? I am looking for detailed description on this topic. Can you share some document or link regarding the same?

[boring]

Actually, you never occupy bandwidth in IuPS, regardless of the RRC state.
Bear in mind that IuPS is essentially IP-based interface and different services follow the Diffserv paradigm which simply differentiate various services on the basis of priorities.

This means that when a IuPS signalling connection is established, one or more PDP contexts are activated (each with their own QoS profile and thus priorities), and whenever IP packets arrive at IuPS for trasmission (in either direction), the IP layer will schedule accordingly the transmission (there is a mapping between QoS profile and Diffserv priorities).

As a result, if for example one UE goes to CELL_PCH this means that there is no user-plane traffic (i.e. no IP packets) and simply IuPS does not take transmit anything for this UE because there is no packets at all.

[auto_art]

Hello Experts, Please share your views about existence of RAB in PCH/FACH state. All ideas are welcome.
Regards, Jack.

If the PDP context remains active, but it is detected that in active connection for a certain

time no data is transferred at all, it is also possible to sent the UE back to IDLE mode or to

CELL_PCH or URA_PCH mode. In all three modes there is no radio bearer/radio access

bearer assigned to the active PDP context – purely for resource usage optimisationreasons.

taken from ralf and kreher umts perf & meas.

[gprastomo]

Yes its still active for reservation, thats why when you activate the fach pch and prolong the inactivity timer , it is recommended to reduce the reservation on the IuB and IuPS since during the PCH or fach, the activity is low so its better to reserve <40% of reservation.

[ritgail]

Does bandwidth kept occupied at Iu part at IuPs interface? I am looking for detailed description on this topic. Can you share some document or link regarding the same?

Cell_FACH/URA_PCH/Cell_PCH are just UTRAN states, or rather Radio Resource Connection State.On RLC layer buffer size/for a particular time(Inactivity timer) RNC decides to what stage the UE should be pushed, these steps are purely to maximise Radio Resource.
For example interactive session like Gtalk, generally UE is pushed to cell_FACH/Cell_PCH when there is no data transfer, after a particular time. In that case you should be shown as logged in, how does that happen!. Because PDP session is alive from SGSN/GGSN and "Keep-Alive" message is sent by the UE as per application specific,(2sec or more normally). Can i make it clear! The RAB must be there.

Again as well said about lu-PS, so for lu-b is just the transport channel layer. So transition from DCH channel to FACH will remove DCH bandwidth as it is not required.

Correct me if i am wrong.
Push the repo button pls

[firstmaxim]

RAB will be established and maintained only for the RRC connected states-Cell_DCH and Cell_FACH. For the other RRC states-Cell_PCH and URA_PCH, the UE is listening to the paging channel and there will be no Radio Bearer.

[jayk]

The doubt aroused because there are counters in Huawei about RAB Release in Cell_PCH, URA_PCH state.

[ritgail]

The doubt aroused because there are counters in Huawei about RAB Release in Cell_PCH, URA_PCH state.

Okey, Huawei approach is always something different in case of 3G. can you provide the counter details.

Uplink:-If data has to be transmitted in Cell_PCH/URA_PCH, UE seeks for cell_FACH with cell_update message cause data transmission. RNC know the UE by x-RNTI (Radio Network Temporary identity), grants in cell_update confirm message. UE can now transmit data immediately through RACH as the RAB is still there. So the user perception is good without noticeable delay. If cell_FACH is not enough, UE trigger event 4a to move to Cell_DCH.
Identity
c-RNTI cell update-uplink data c-RNTI cell_update(event 4a) s-rnti
Cell_PCH<--------------------------->cell_FACH<------------------------------>Cell_DCH

Downlink:The RLC buffer in RNC will cross a defined threshold(A) for the said cell_PCH UE c-RNTI, then the PI in the PICH flag will be up for the SFN the UE is supposed to listen. Followed by 3 TS delay,the details will be sent with cause value paging type 1 in PCH/SCCPCH. UE reply in RACH/ immediately the data are sent through FACH/ or if the Data content is more UE can be commanded to move to cell_DCH.


Now the question come to RAB, which is again on Iu-PS intreface, there is active and inactive states. This should not be released, if released the UE should be in like IDLE mode. there is no point of keeping in radio resources. You know what i mean.

Again I would say, Huawei is different, so if you have document please provide. Thanks.

Or do a call tracing, see the call flow ,it will clear up our doubts. In your network, all the RRC states are enabled like Cell_PCH/URA_PCH both?