3G NPWG AP02/04
T_rlfl and T314
Rigo Helmchen
Nokia Siemens Networks
Company Confidential
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© Nokia Siemens Networks
3G NPWG AP02/04
Reason for setting of T_rlfl and T314
Reason for change:
• t_rlfl from 10sec to 3sec:
If a radio link has not improved in 3sec (+ 10 out of sync), then the chance is very low
that this link improves in 10sec. Therefore in order to reduce the interference for the
other links and to save NodeB power 3sec is recommended.
• t314 from 12sec to 6sec:
Most users, in case of CS, are not waiting 12sec on the phone and hoping that the call
will be re-established (most users are not aware of call re-establishment feature) -->
most users are waiting e.g. only 6sec. Therefore decision was to go for 6sec, to save
also resources for other users.
Additional Recommendation:
• t313 and t_rlf should have same value
–
t313 (UE timer Æ Radio Link Timeout: Within T313 N315 ‘IN_SYNC_IND’ are expected to be
received within the UE. Otherwise a Radio Link Failure is to be detected)
– t_rlfl (NodeB timer Æ The Radio Link Failure procedure shall be triggered after a period of time
T_RLFAILURE has elapsed with a persisting out-of sync indication)
•
In networks with a lot of UE’s which are not supporting RRC re-establishment, for t_rlfl
and t313 a value of 5 could be applied.
Company Confidential
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© Nokia Siemens Networks
3G NPWG AP02/04 / Rigo Helmchen / 30.04.2007
Setting of Synchronisation and RL Re-establishment
Timer for UE in DCH
Node B
UE
RNC
CPHY
OUT_of_SYNC_IND
n313 times
Out of Sync.
Start timer
T313
no_osync times
Start timer
t_rlfl
State
Timer
T313
expired
Timer
RRC: CellUpdate
(radioLinkFailure)
T314
Update
Procedure
Repeated N302
Times if sync. not
established
CPHY
OUT_of_SYNC_IND
RRC: RL Re-Establishment Complete
Under T302
control
Company Confidential
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© Nokia Siemens Networks
Timer
t_rlfl
expired
Release of Radio
Resources
3G NPWG AP02/04 / Rigo Helmchen / 30.04.2007
n313 = counts of successive out-ofsync messages indicated from
physical layer at the UE.
T313 expires Î UE release its
dedicated resource, starts T314
and start a cell selection procedure
in order to perform an RRC Reestablishment via
CellUpdate(radioLinkFailure).
T_RLFL Î timer for the NodeB to
wait for signallingless syncreestablishment, if timer expires the
RNC is notified about radio-link
failure, NBAP dedicated resources
are released and T314rnc is
started.
T314 Î At the expiration of T314,
the UE goes to idle or/and the RNC
releases the Iu connection and a
RRC connection re-establishment
becomes impossible, the call is
dropped.