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• List the motivations for cell selection & reselection• Explain the meaning of “Equivalent PLMN“• Name the differences between access classes and cell access
restrictions• Describe the state transition in the RRC idle mode• Understand the cell selection criterion, S• Name the differences, when cell selection is performed with and
without HCS• Outline the measurement rules for both HCS enabled cells and
cells without priorities• Explain the ranking criterion, R
• The mobile phone tries to find a suitable cell to camp on. •With a suitable cell, all network services are available.
• If it is unable to find such a cell, it attempts to camp on any – non-barred – cell. •It enters an internal "limited service" state. In this state, only emergency calls can be carried out. The same state is given, when no USIM was inserted in the UE or the location registration failed.
• The UE is also responsible for cell reselection in the RRC connected mode states CELL_FACH, CELL_PCH and URA_PCH.
•The purpose of camping on a cell are the same as in the RRC idle mode with the exception of RRC connection establishment (because the RRC connection already exists). •The cell reselection procedure is the same in the RRC idle and RRC connected mode.
• WCEL: CellBarred•Defines whether the cell is barred or not. •A barred cell is a cell where a UE is not allowed to camp on. •This parameter is part of SIB 3.•0 (Barred), 1 (Not barred); default: 1.
• WCEL: TBarred•If the UE does not select another cell, and the barred cell remains to be the “best” one, the UE shall after expiry of the time interval Tbarred again check whether the status of the barred cell has changed.•This parameter is part of SIB 3.•[10, 20, 40, 80, 160, 320, 640, and 1280] seconds; default: 40 seconds.
• WCEL: Cell_Reserved•Defines whether the cell is reserved for operator use. •This parameter is part of SIB 3.•0 (Reserved), 1 (Not reserved); default: 1.
• WCEL: IntraFreq_Cell_Reselect_Ind•Defines whether intra-frequency cell re-selection is allowed when the cell is barred.•This parameter is part of SIB 3/4.•0 (Allowed), 1 (Not allowed); default: 0.
NSN Parameters for Cell Reservations and Restrictions
• WCEL: UseOfHCS•This parameter indicates whether the serving cell belongs to a Hierarchical Cell Structure (HCS). •This parameter is part of SIB 11/12.•0 (HCS not used), 1 (HCS in use); default: 0.
• WCEL: Sintrasearch•The threshold for intra-frequency measurements, and for the HCS measurement rules.•This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 10 dB.
• WCEL: Sintersearch•The threshold for inter-frequency measurements, and for the HCS measurement rules.•This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 8 dB.
• WCEL: Ssearch_RAT•The RAT-specific threshold for inter-RAT measurement rules. •This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 4 dB.
• WCEL: SHCS_RAT•The RAT specific threshold for inter-RAT measurement rules. •This parameter is part of SIB 3.•[-1 ... 91] dB, step 2 dB, default: -1 dB (UE sets this value to 0).
• WCEL: Slimit_SearchRAT•Threshold for skipping inter-RAT measurement rules in HCS. •Above this RAT specific threshold in the serving UTRA cell, the UE does not need to perform any inter-RATm measurements. •This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 2 dB.
• WCEL: SsearchHCS•Threshold for intra- and inter-frequency measurement rules in HCS. •Below this limit in the serving cell, the UE initiates measurements of all intra and inter-frequency neighbouring cells of the serving cell. •This parameter is part of SIB 3.•[-1 ... 91] dB, step 2 dB, default: -1 dB (UE sets this value to 0).
• WCEL: NCr•This parameter defines the maximum number of cell reselections.•If the number of cell reselections during the TCrmax time period exceeds the value of NCr, high mobility has been detected. •Not used if TCrmax equals 'not used’.•This parameter is part of SIB 3.•[1 ... 16], default: 8.
• WCEL: TCrmax•The duration for evaluating the allowed amount of cell reselections. •If the number of cell reselections during the time period defined by Tcrmax exceeds Ncr, high mobility has been detected. •This parameter is part of SIB 3.•[0 (= not used), 30, 60, 120, 180, 240] seconds, default: 60 seconds.
• WCEL: TCrmaxHyst•Cell reselection hysteresis for reverting from UE high-mobility measurements.•The additional time period before UE reverts to low-mobility measurements.•This parameter is part of SIB 3.•[0 (= not used), 10, 20, 30, 40, 50, 60, 70] seconds, default: 0 seconds.
• WCEL: HCS_PRIO•This parameter defines the HCS priority level for a cell. •Value 0 indicates the lowest HCS priority and value 7 indicates the highest HCS priority.•[0 ... 7], default: 0.
• WCEL: QHCS•Quality threshold level for applying prioritised hierarchical cell re-selection for a cell. •Part of HCS Serving cell information (Qhcss). •This parameter is part of SIB 3. •[-24 ... 0] dB, step 0.5 dB, default: -24 dB.
• HOPS: AdjsHCSthreshold•Defines the threshold level which must be exceeded by the CPICH Ec/No of the intra-frequency neighbouring cell before the hierarchical cell re-selection becomes possible (Qhcsn).•[-24 ... 0] dB, step 0.5 dB, default: -24 dB.
• HOPS: AdjsTempOffset1•This parameter is used in the cell ranking between cells when the intra-frequency neighbour cell has the same HCS priority level as the serving cell. •[3, 6, 9, 12, 15, 18, 21, 100 (Infinity)] dB, default: 3 dB. •HOPI: AdjiTempOffset1, •HOPG: AdjgTempOffset1
• HOPS: AdjsTempOffset2•This parameter is used in the cell ranking between WCDMA cells when the intra-frequency neighbour cell has the same HCS priority level as the serving cell. •[2, 3, 4, 6, 8, 10, 12, 100 (Infinity)] dB, default: 2 dB. •HOPI: AdjiTempOffset2
• HOPS: AdjsPenaltyTime•Defines the time period during which the Temporary Offset 1/2 is applied in the cell re-selection procedure for the intra-frequency neighbour cell in question.•[0 ... 60] seconds, step 10 seconds, default: 0.•HOPI: AdjiPenaltyTime, •HOPG: AdjgPenaltyTime
• WCEL: Qhyst1 (Qhyst2) • Qhyst1 is used for TDD and GSM cells, and for FDD cells when cell selection and re-
selection quality measure is set to CPICH RSCP (CPICH Ec/No) (Qhyst1s/ Qhyst2s). • This parameter is part of SIB 3.• [0 ... 40] dB, step 2 dB, default: Qhyst1 = 0 dB, Qhyst2 = 2 dB.
• HOPS: AdjsQoffset1 (AdjsQoffset2) • This parameter is used in the cell re-selection and ranking between WCDMA cells. • The value of this parameter is subtracted from the measured CPICH RSCP (CPICH Ec/No)
of the intra-frequency neighbour cell before the UE compares the quality measure with the cell re-selection/ranking criteria.
• How often are measurements conducted for cell re-selection evaluation? • What happens, if the criterion S is no longer fulfilled for the cell, the UE camps on?
• Serving Cell• At least once every DRX cycle, the UE must
• measure the CPICH Ec/Io & CPICH RSCP level of the Serving Cell and• evaluate the S criterion.
• Hereby, the UE filters measurement results. • It takes at least 2 measurements, and the time difference between the measurements must have been at least TmeasureFDD/2.• If the serving cell is not fulfilling the cell selection criterion S for Nserv consecutive DRX cycles, the UE has to start measurements on all neighbouring cells.
• The Nserv is known by the UE with the DRX cycle length. • The UE has to find a suitable cell within 12 seconds.
• If it fails, and the UE is in the RRC idle mode, it initiates the cell selection procedures for the selected PLMN. • If it fails to find a suitable cell within 12 seconds, and the UE is in the RRC connected states CELL_FACH, CELL_PCH or URA_PCH, it is considered to be “out of service area“.