Cell Update This document is a reference to Cell update procedure. Reason for which MS can initiate Cell Update Procedure:
-Cell_DCH State: Cause: Reason: Cause: Reason:
Radio Link failure Loss of L1 synchronization RLC unrecoverable error. To no notify RL RLC un unrecoverable er error.
-Cell_FACH or Cell_PCH State: Cause: Cell reselection Reason: UE has entered in to a new cell. Cause: Reas Reason on::
Periodic Cell Update Per Periodi iodicc Cell Cell Upda Update te bas based on SIB SIB infor nform matio ation. n.
Cause: Reas Reason on::
Re-entering Service area Acce Access ssiing ser servi vice cess aft after er an out out of cove coverrage age si situat tuatio ion. n.
-Cell_PCH State: Cause: Reason:
UL data request To in indicat cate th that MS wa wants to se send UL UL data.
Cause: Reas Reason on::
Paging Response To ans answe werr to the the RRC RRC:: Pag Pagin ing g typ typee 1 mes message sage rece receiv ived ed from RNC
Points to Consider: 1.RRC: Cell Update message is always send on CCCH channel. 2. RRC: Cell Update message contains U-RNTI and Cell Update Cause. 3.If the MS is in Cell_PCH State, first make the transition to Cell_FACH State. 4. MS may send consecutive Cell Update messages when a different criterion is met 5. All cause values (except the ‘ RLC RLC unrecoverable error ’) ’) are interpreted as a valid paging response for the UTRAN originated paging.
Handing of Cell Update request based on Cell Update Cause:
A. Cell update due to cell reselection: If the cell update cause in RRC: CELL UPDATE message is ‘cell reselection’ then the RRC entity updates the MS location information and (re) starts Cell_FACH or Cell_PCH state supervision timer, PeriodicCellURAupdWait timer, PeriodicCellURAupdWait . Point to Consider: When a cell update is received from the MS, the RRC entity shall first check the status of the ‘MSActivitySupervision’ ‘MSActivitySupervision’ timer. timer. If the ‘MSActivitySupervision’ ‘MSActivitySupervision’ has has expired the release of the resources of this MS (Iu Release Request procedure due to user inactivity) is initiated. After the new C-RNTI is allocated, the RRC entity informs it to the MAC-c entity of a new cell and also requests the MAC-c entity of the previous cell (if existing) to release the old C-RNTI. Also the U-RNTI is informed by RRC entity to MAC-c entity. It is also indicated that the MAC-c must use U-RNTI while sending RRC:CELL UPDATE CONFIRM message. As a response to RRC:CELL UPDATE message the RRC entity sends an RRC:CELL UPDATE CONFIRM message on DCCH to the MS. If the MS has been in Cell_FACH state and/or it shall remain in this state, the RRC:CELL UPDATE CONFIRM message shall contain a new C-RNTI. In this case the MS configures layer 2 to use the new identities and returns an RRC:UTRAN MOBILITY INFORMATION CONFIRM message as a response. MS
BTS
RNC
MS is in CELL_FACH or CELL_PCH state RRC:CELL UPDATE [Cause: Cell Reselection]
RRC:CELL UPDATE CONFIRM S kept in Cell_FACH: [RRC state: Cell_FACH; New C-RNTI] S moved from Cell_FACH: [RRC state: Cell/URA_PCH]
RRC:UTRAN MOBILITY INFORMATION CONFIRM If updating of the UL traffic volume measurement threshold is needed RC:MEASUREMENT CONTROL [Traf.Vol.Meas.]
Cell Update due to cell reselection
B. Cell update due to periodical cell update Periodic Cell Update in Cell_PCH state: If the cell update cause in RRC:CELL UPDATE message is ‘periodic cell update’ , the RRC entity updates the MS location information and if the MS is in Cell_PCH state, resets the Cell_PCH state supervision timer, PeriodicCellURAupdateWait (see Error: Reference source not found). found). If the timer ‘MSActivitySupervision ‘ MSActivitySupervision ’ has expired when the Cell Update messa message ge is recei received ved from the the MS, MS, the RRC entit entity y initia initiates tes the the Iu release request procedure towards the PS-CN (CN is informed about the user inactivity). The CN may ignore the initiated Iu release without send sendin ing g a resp respon onse se to the the RNC. RNC. In this this case case the the Iu conn connec ecti tion on remains, a state transition from Cell_FACH state to Cell_PCH state is initiated and the timer ‘ MSActivitySupervision ’ shall be restarted If a response to the Iu release request is received from the CN, the Iu connection is released and a RRC Connection Release procedure is initiated. After this the MS transfers to the Idle Mode.
Periodic Cell Update in Cell_FACH state: In practice the time, which an inactive MS is allowed to stay in Cell_FACH state will be much shorter than the interval for periodic updates, and thus the reception of the periodic Cell Update in Cell_FACH state can be considered as a failure situation or an exception case. If however, a periodic Cell Update in Cell_FACH state is received, the MS is immediately moved to the Cell_PCH state if allowed. MS
BTS
RNC
MS is in CELL_FACH or CELL_PCH state
RRC:CELL UPDATE [Cause: Periodical Cell Update]
RRC:CELL UPDATE CONFIRM [RRC state: Cell/URA_PCH]
C. Cell update due to radio link failure If the cell update cause in RRC: CELL UPDATE message is ‘Radio link failure’ , the RRC entity updates the MS location and state information (from Cell_DCH to Cell_DCH to Cell_FACH ). ).
D. Cell update due to UL data transmission If the the cell cell upda update te caus causee in RRC: RRC: CELL CELL UPDA UPDATE TE mess messag agee is ‘UL ‘UL data data transmission’ , the RRC entity forwards this information to the PS. As a response to RRC: CELL UPDATE message the RRC entity sends an RRC: CELL UPDATE CONFIRM message on DCCH to the MS. The RRC: CELL UPDATE CONFIRM message may include a new C-RNTI (and/o (and/orr U-RNTI U-RNTI after the SRNS SRNS reloca relocatio tion n procedu procedure) re).. In this this case case the MS conf config igur ures es laye layerr 2 to use use the the new new iden identi titi ties es and and retu return rnss an RRC: RRC: UTRA UTRAN N MOBILITY INFORMATION CONFIRM message as a response. The MS shall remain in Cell_FACH state and in case the MS is assigned a new CRNTI RNTI and/ and/or or U-RN U-RNTI TI (S-R (S-RNT NTII plus plus SRNC SRNC iden identi tity ty), ), an RRC: RRC: UTRA UTRAN N MOBILITY INFORMATION CONFIRM message is sent by the MS to the RRC entity. E. Cell update due to paging response MS
RNC
BTS
MS is in CELL_PCH state or URA_PCH state
RRC:PAGING RRC:PAGING TYPE 1 [U-RNTI] MS moves to CELL_FACH state
RRC:CELL UPDATE [Cause: Paging Response] RRC:CELL UPDATE CONFIRM [New C-RNTI] RRC:UTRAN MOBILITY INFORMATION CONFIRM
MS is in CELL_FACH state
NAS signaling sequence or u-plane data flow
If the cell update cause in RRC: CELL UPDATE message is ‘paging response’ , the RRC entity updates the MS location information. F. Cell update due to re-entering service area If the cell update cause in RRC: CELL UPDATE message is ‘re-entering service area’ then the RRC entity shall check if a state supervision timer,
PeriodicCellURAupdateWait, is runnin running g and stop stop this this timer. timer. After this the possible possible suspended RRC procedure can be reinitiated. In other case the indication of ‘re-entering of ‘re-entering service area’ received area’ received from the MS may be collected in statistics (if needed). If the Iu connection for this MS is already released, the RRC Connection release is executed via the CCCH, and the MS is moved to the Idle Mode. G.Cell update due to RLC unrecoverable error If in MS RLC the number of retransmissions of the RLC RESET PDU exceeds the upper limit, the MS shall send a Cell Update message (with a cause value “RLC unrecoverable error”) to RNC. The MS should indicate in the message whether the unrecoverable error exists in the signaling radio bearer SRB2, SRB3 or SRB4 or in another radio bearer (RB>4). When RRC entity/MCC receives this message, it checks which radio bearer(s) has the unrecoverable error. If MS is in Cell_FACH state when the ‘unrecoverable error’ occurs in control and/or user plane RBs, the RRC entity/MCC shall order the MS to re-establish its control/user plane RLC entities accordingly by RRC: CELL UPDATE CONFIRM mess messag age. e. At the the same same time time RNC RNC shal shalll also also re-e re-est stab abli lish sh its its own own cont contro roll plane/user plane RLC entities. RLC Re-establishment is done by sending the RFU control command message with re-establishment info per SRB/RB to RLC entity by RRC entity/MCC.
In case the MS was in Cell_DCH Cell_DCH state and the ‘unrecoverable ‘unrecoverable error’ error’ occurred in cont contrrol plan planee RBs RBs whil hile runni unning ng the HHO HHO or SHO SHO proc proced edur ures es or the the ‘unrecoverable error’ occurred in user plane RB, the handling is as in Cell_FACH state. In any other case the RRC entity/MCC shall initiate the RRC Connection Release procedure. When When RRC RRC enti entity ty/M /MCC CC recei receive vess a Cell Cell Upda Update te mess message age beca becaus usee of RLC RLC unrecoverable error in SRB2, SRB3 or SRB4, it shall initiate the RRC Connection Releas Releasee procedu procedure re by transm transmitt itting ing RRC: RRC: RRC CONNEC CONNECTIO TION N RELEAS RELEASE E message on the downlink CCCH.
