what is the difference between T314 and T315 in 3G?

[tareq1010]

Dear 3G Experts,
can any one tell me what is the difference between T314 and T315 in 3G?

[hari_2208]

T314 & T315 are guard timers during which the UE keeps the RABs following radio link failure until they expire or the cell update procedure has been completed. During this time, the RNC can try to re-establish the UE so that the user traffic can resume. When T314 and / or T315 expire, the UE releases the associated RABs.

From specs....

t302

: Starts at the transmission of CELL/URA UPDATE, and stops at the

reception of CELL/URA UPDATE CONFIRM.

T314 expiry
Upon expiry of timer T314 the UE shall:
1> if timer T302 is running:
2> continue awaiting response message from UTRAN.
1> if timer T302 is not running and timer T315 is running:
2> set IE "T314 expired" in variable RB_TIMER_INDICATOR to TRUE;
2> release locally all radio bearers which are associated with any radio access bearers for which in the variable
ESTABLISHED_RABS the value of the IE "Re-establishment timer" is set to "useT314";
2> indicate release of those radio access bearers to upper layers;
2> delete all information about those radio access bearers from the variable ESTABLISHED_RABS;
2> if all radio access bearers associated with a CN domain are released:
3> release the signalling connection for that CN domain;
3> remove the signalling connection for that CN domain from the variable
ESTABLISHED_SIGNALLING_CONNECTIONS;
3> indicate release (abort) of the signalling connection to upper layers.
1> if timers T302 and T315 are not running:
2> clear the variable RB_UPLINK_CIPHERING_ACTIVATION_TIME_INFO;
2> clear the variable INTEGRITY_PROTECTION_ACTIVATION_INFO;
2> clear the variable PDCP_SN_INFO;
2> clear the entry for the CELL UPDATE CONFIRM message in the table "Rejected transactions" in the
variable TRANSACTIONS;
2> release all its radio resources;
2> indicate release (abort) of the established signalling connections (as stored in the variable
ESTABLISHED_SIGNALLING_CONNECTIONS) and established radio access bearers (as stored in the
variable ESTABLISHED_RABS) to upper layers;
2> clear the variable ESTABLISHED_SIGNALLING_CONNECTIONS;
2> clear the variable ESTABLISHED_RABS;
2> set the variable CELL_UPDATE_STARTED to FALSE;
2> enter idle mode;
2> other actions the UE shall perform when entering idle mode from connected mode are specified in subclause
8.5.2;
2> and the procedure ends.


T315 expiry
Upon expiry of timer T315 the UE shall:
1> if timer T302 is running:
2> continue awaiting response message from UTRAN.
1> if timer T302 is not running and timer T314 is running:
2> set IE "T315 expired" in variable RB_TIMER_INDICATOR to TRUE;
2> release locally all radio bearers which are associated with any radio access bearers for which in the variable
ESTABLISHED_RABS the value of the IE "Re-establishment timer" is set to "use T315";
2> indicate release of those radio access bearers to upper layers;
2> delete all information about those radio access bearers from the variable ESTABLISHED_RABS;
2> if all radio access bearers associated with a CN domain are released:
3> release the signalling connection for that CN domain;
3> remove the signalling connection for that CN domain from the variable
ESTABLISHED_SIGNALLING_CONNECTIONS;
3> indicate release (abort) of the signalling connection to upper layers.
1> if timers T302 and T314 are not running:
2> clear the variable RB_UPLINK_CIPHERING_ACTIVATION_TIME_INFO;
2> clear the variable INTEGRITY_PROTECTION_ACTIVATION_INFO;
2> clear the variable PDCP_SN_INFO;
2> clear the entry for the CELL UPDATE CONFIRM message in the table "Rejected transactions" in the
variable TRANSACTIONS;
2> release all its radio resources;
2> indicate release (abort) of the established signalling connections (as stored in the variable
ESTABLISHED_SIGNALLING_CONNECTIONS) and established radio access bearers (as stored in the
variable ESTABLISHED_RABS) to upper layers;
2> clear the variable ESTABLISHED_SIGNALLING_CONNECTIONS;
2> clear the variable ESTABLISHED_RABS;
2> set the variable CELL_UPDATE_STARTED to FALSE;
2> enter idle mode;
2> other actions the UE shall perform when entering idle mode from connected mode are specified in subclause
8.5.2;
2> and the procedure ends.

[zhanglw268]

T314 is used for CS radio link failure, T315 is used for PS radio link failure.

[idxtor]

here is quote from the following document:http://www.scribd.com/doc/79118694/O...ity-NSN-Draft1

In 3G a new mechanism is available to rescue some dropped calls (both CS and PS) due to RL Failure: Call Reestablishment by Cell Update procedure. Refer to ANNEX I for further details.

If timer T314 is set higher than 0, Voice calls that suffer from a RL Failure are not considered “dropped” till timer T314 expires and the call could not be reestablished by the Cell Update Procedure.

Similarly, if timer T315 is set higher than 0, PS calls that suffer from a RL Failure are not considered “dropped” till timer T315 expires and the call could not be reestablished by the Cell Update Procedure.

We could say that in both cases, CS and PS, those RL Failures that can be rescued are just system-perceived drops, but not user-perceived drops, as the user does not have to perform any additional manual operations like for example manual re-activation of the PDP context. In reality, during the Cell Update procedure (T314 or T315 seconds), Voice calls will be perceived as “silent” by the user, and PS data sessions may suffer from delays and lower throughputs, but the fact is that the call does not drop, and it is not counted by the RAB releases counters (and therefore, neither as a drop).

In NSN infrastructure, T314=0 is hardcoded, and T315=30 sec (changeable), i.e., this Cell Update mechanism is only available for PS data calls (not for Voice calls).

• In terms of Voice Calls, this means that all RL Failures in DL will finally lead to a drop (user and system perceived, and RAB release counters –and drops- increased).
• In terms of PS Calls, those RL Failures that are rescued will be system but not user-perceived, and the abnormal RAB release counter (=drops) will not be increased.

As some other vendors may have the Cell Update mechanism de-activated for PS, the optimization team should keep in mind these considerations when comparing PS DCR (%) in different vendors: usually worst in those ones with this functionality disabled. Nevertheless, this worst behavior in the KPI usually does not match the user perception (that is typically good) thanks to additional implicit re-establishment mechanisms (Paging/Service Request).

[phuvuong_uk]

Can we set it with NodeB level?

[narula.pawan@gmail.com]

Dear 3G Experts,
can any one tell me what is the difference between T314 and T315 in 3G?

Dear,

These are the UE Timers used during the Cell Update

T314: RRC Connection Re-Establishment Timer used for CS-RAB services.UE starts this timer where there is RL failure and exists till the UE completes the cell update procedure. Once this timer expired then it releases the CS-RAB.

T315: RRC Connection Re-Establishment Timer used for PS-RAB services.UE starts this timer where there is RL failure and exists till the UE completes the cell update procedure. Once this timer expired then it releases the PS-RAB.

Br..
Pawan

[nkboy9]

t314 for cs domain (or CS RAB)
t315 for ps domain (ps rab)