IDLE MODE BEHAVIOUR AND CONNECTED MODE BEHAVIOUR IN CELL_FACH STATE

IDLE MODE BEHAVIOUR AND CONNECTED MODE BEHAVIOUR IN CELL_FACH STATEAgendaIntroductionPLMN selectionCell selectionCell reselectionLocation area (LA) and Routing area (RA) updatingPagingSystem information broadcastCELL_FACH StateIntroductionIdle modeNo connection to radio network (No RRC connection established)This minimizes resource utilization in UE and the networkUE must be able to access the system and be reached by system with reasonable delays

CELL_FACH modeUser Equipment (UE) in Connected Mode (has an RRC Connection to radio network) UE uses the common transport channels RACH or FACH

CELL_DCH modeUser Equipment (UE) in Connected Mode (has an RRC Connection to radio network)UE uses dedicated channels for transmitting data and signallingIdle modeFunctions performedPLMN SelectionCell Selection and ReselectionLocation Area (LA) and Routing Area (RA) updatingPagingSystem Information Broadcast

PLMN SelectionPLMN selection performed upon power on or upon recovery from lack of coverage

If there is no last registered PLMN, or if it is unavailable, the UE will try to select another PLMN AUTOMATICALLY or MANUALLY depending on its operating mode

Manual modeUE displays all PLMNs (allowed and not allowed) by scanning all frequency carriersThe user makes a manual selection and the UE attempts registration on the PLMN

PLMN Selection (Contd)

In automatic mode, if no last registered PLMN exists or is available, the UE selects a PLMN in the following order of priorityEach PLMN in the user-controlled PLMN list in the USIM, in order of priorityEach PLMN in the operator-controlled PLMN list in the USIMOther PLMNs according to the high-quality criterion (WCDMA: CPICH RSCP >= -95 dBm; GSM: SS >= -85 dBm)Other PLMNs, in order of decreasing signal strengthPLMN selection (Contd)Roaming is a service through which a UE is able to obtain services from another PLMN

The UE in Automatic mode, having selected and registered a Visited PLMN (VPLMN) periodically attempts to return to its Home PLMN (HPLMN)

The time interval between consecutive attempts is stored in the USIM and is managed by the network operator using a timer. The timer may have a value between 6 minutes and 8 hours with a step size of 6 minutes. A default value is 30 minutes.Cell SelectionUE looks for a suitable cell in the selected PLMN and camps on to it

Cell search procedureUE acquires slot synchronization using P-SCHIt acquires frame synchronization using S-SCHPrimary scrambling code is obtained from CPICH

UE then monitors the paging and system information, performs periodical radio measurements and evaluates cell reselection criteria

WCDMA is sensitive to intra frequency interferenceMeasurements used in cell selection and cell re-selection not only relate to signal strength but also to quality of CPICH

Cell SelectionStrategies used for the cell selection process:

Initial Cell Selection: UE has no knowledge of the WCDMA radio channelsUE scans all WCDMA radio frequency channels to find a suitable cell with the highest signal level and read BCCHThe PLMN is determined from the mcc and mnc in the MIB in BCCH

Stored Information Cell Selection: UE knows the carrier frequencies that have previously been used

Cell Selection Procedure (Contd)

Cell selection procedure (Contd)For cell selection criteria the UE calculatesSqual = Qqualmeas - qQualMin (for WCDMA cells)Srxlev = Qrxlevmeas - qRxLevMin Pcompensation (for all cells)

Where Pcompensation = max(maxTxPowerUL P,0)P is output power of UE according to classCell selection criteria (S criteria) is fulfilled whenSqual>0 ( for WCDMA cells only)and Srxlev>0Recommended valuesqQualMin= -19dB (Values in BLUE are values of the parameters)qRxLevMin= -115dBmNote: Increase qRxLevMin if primaryCpichPower is increased to make cell size constant. (maxTxPowerUL = 24)Cell reselectionUE ranks available cells using R criteriaR(Serving) = Qmeas(s) + qHyst(s)R(Neighbour) = Qmeas(n) qOffset(s,n)

Qmeas is the quality value of the received signalDerived from the averaged received signal level for GSM cellsDerived from CPICH Ec/Io or CPICH RSCP for WCDMA cells depending on the value of qualMeasQuantity (2, Ec/Io)

qHyst(s) = qHyst1 when ranking based on CPICH RSCP (4)qHyst(s) = qHyst2 when ranking based on CPICH Ec/Io (4)qOffset(s,n) = qOffset1sn when ranking based on CPICH RSCPqOffset(s,n) = qOffset2sn when ranking based on CPICH Ec/IoThe above two values are 0 for WCDMA cells and 7 for GSM cellsCell reselection (Contd)The ranking is first based on RSCPIf a GSM cell is the best cell, the UE reselects to that cellIf a WCDMA cell is the best cell, the UE again performs ranking on a parameter depending on qualMeasQuantity and then performs cell reselectionThe UE will reselect a new cell if it is better ranked than the serving cell for a time interval of treSelection (1)Intra frequency measurementsIf Squal < SIntraSearch, the UE performs Intra-Freq measurements (22)Remember: Squal = Qqualmeas - qQualMinInter frequency measurementsIf Squal < SInterSearch, the UE performs Inter-Freq measurements (0)Inter-RAT measurementsIf Squal < SRatSearch or Srxlev 0 (4)

If the parameter interFreqFDDMeasIndicator = 1, the UE will evaluate cell reselection criteria on inter-frequency cells (0)

Paging: When a connection exists between the WCDMA RAN and the UE, Paging Type 2 is sent through dedicated control channels

System information change: Ue receives a System Information Change Indication message containing the information element BCCH modification info