3G NPWG AP02/04 T_rlfl and T314 Rigo Helmchen Nokia Siemens Networks Company Confidential 1 © 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 2 © 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 3 © 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.