WCDMA CELL SELECTION AND RESELECTION PARAMETERS
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INTRODUCTION
• The cell selection and reselection procedures allows the UE to look for a suitable cell in the selected PLMN and camp on it. • The measurement used in the cell selection and cell reselection processes are CPICH RSCP and CPICH Ec/No. • Once UE enters a camped normally state, it is able to monitor paging, system information, perform periodic radio measurement and evaluates cell reselection algorithm.
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Cell selection • When a UE is switched on • When a UE in Idle mode has had a number of failed RRC connection requests • When a UE returns to Idle mode from the Connected mode on common channels (CELL_FACH state) after a number of failed cell update attempts • When a UE moves from dedicated mode to Idle mode • When a UE returns to Idle mode after an emergency call on any PLMN • When a UE moves from dedicated mode to state CELL_FACH or URA_PCH.
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CELL RESELECTION • The UE performs the cell reselection procedure in the following cases: – When the cell on which it is camping is no longer suitable – When the UE, in "camped normally" state, has found a neighboring cell better than the cell on which it is camping – When the UE is in "limited service" state on an acceptable cell – The UE reselects the new cell if it is better ranked than the serving cell during a time interval treSelection.
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CELL SELECTION/RESELECTION criteria S - Criteria • Measurements for GSM selection/reselection starts if Squal < sRatSearch and/or Srxlev < sHcsRat where Srxlev = Qrxlevmeas – qRxLevMin – P_compensation where P_compensation = max(maxTxPowerUl-P,0) where P is is the maximum RF output power of the UE according to its class. • Measurements for UMTS selection/reselection starts if Squal < sIntraSearch where Squal = Qqualmeas – qQualMin
R- Criteria R(s)=Q meas (s) + qHyst (s) + Q offmbms R(n)= Qmeas(n) – qOffset (s,n) + Qoffmbms – TO (n)
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definition • qQualMin is a cell parameter that indicates the minimum required quality value in the cell for idle mode camping and is sent in SIB3 for the serving cell and SIB11 for adjacent cells. • qRxLevMin is a cell parameter that indicates the minimum required signal strength in the cell for idle mode camping and is sent in SIB3 for the serving cell and SIB11 for adjacent cells. • Qqualmeas is the quality value measured by the UE expressed as CPICH Ec/No • Qrxlevmeas is the received signal strenght measured by the UE and expressed as CPICH RSCP. • Pcompensation is introduced for UEs that cannot trasmit at maximum power on the RACH in the cell. • maxTxPowerUl is a cell parameter that indicates the maximun allowed transmitted power when the UE accesses the system on RACH and is broadcasted on SIB3
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definition
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definition
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PARAMETERS
Parameters are set per utrancell • qQualMin; Unit: dB, Range: -24 to 0 – Too low values; selection criteria is satisfied harder, less reselections... – Too high values; selection criteria is satiesfied easily, more reselections... • sIntraSearch; Unit: 2 dB, Range: 0 to 27, 0:not sent, 1:-32dB, 2:-30dB....27:20dB – Too high values; selection criteria is met easier, more reselections... – Too low values; selection criteria is met harder, less reselections...
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PARAMETERS • qRxLevMin; Unit: dBm, Resolution: 2, Range: -119 to -25 – Set per utrancell – Too low values; less reselections... – Too high values; more reselections... • sRatSearch; Unit: 1dB, Resolution: 2, Range: -32 to 20 – Set per utrancell – Too high values; more reselections from UMTS to GSM... – Too low values; less reselections... • sHcsRat; Unit: dB, Resolution:2, Range: -105 to 91 – Set per utrancell – Too high values; more reselections... – Too low values; less reselections... • maxTxPowerUl; Unit: dBm, Range: -50 to 33 – Set per utrancell 10
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PARAMETERS • qOffset1sn is used at cell ranking when selection/reselection criteria is CPICH RSCP • qOffset2sn is used at cell ranking when selection/reselection criteria is CPICH Ec/No • Parameters are set per utran/gsm relation • Unit: dB, Range: -50 to 50 • They are used to prioritise/penalize the cells in selection/reselection • Too high values; cell is selected harder • Too low values; cell is selected easier
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PARAMETERS • •
qHyst1 is used at cell ranking when selection/reselection criteria is CPICH RSCP qHyst2 is used at cell ranking when selection/reselection criteria is CPICH Ec/No - Parameters are set per utrancell. - Resolution: 2, Range: 0 to 40 - They are used to prioritise/penalize serving cell in selection/reselection - Too high values; Serving cell serves longer time - Too low values; Serving cell serves shorter time
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The UE reselects the cell if it is best ranked than the serving cell during a time interval treSelection. – Unit: seconds, Range: 0 to 31 – Too high values; less reselections... – Too low values; more reselections...
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EXAMPLE
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Cell reselection in DCH mODEmODE- IFHO • • 1. 2. •
Inter-frequency handover (IFHO) allows the UTRAN to switch the serving frequency of the UE during dedicated channel state. Like the inter-RAT handover, the inter-frequency handover procedure consists of two steps: The inter-frequency measurements The inter-frequency handover Since IFHO is a hard handover, it employs compressed mode to facilitate inter-frequency measurements.
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LAYER MANAGEMENT for multimulti- CARRIER
•This is a layer management for 2nd and 3rd carrier. HO ttype here is set to IFHO, IRAT NONE.. Depending on coverage, traffic and position of the cell, whether border site or not.
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• Questions
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