WCDMA CELL SELECTION AND RESELECTION PARAMETERS
MTN Ghana
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
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When a UE in Idle mode has had a number of failed RRC connection requests
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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
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When a UE moves from dedicated mode to Idle mode
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When a UE returns to Idle mode after an emergency call on any PLMN
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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 •
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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 Q rxlevmeas is the received signal strenght measured by the UE and expressed as CPICH RSCP. P compensation 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
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Unit: dB, Range: -50 to 50
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They are used to prioritise/penalize the cells in selection/reselection
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Too high values; cell is selected harder
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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 •
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 mODE mODE- IFHO •
Inter-frequency handover (IFHO) allows the UTRAN to switch the serving frequency of the UE during dedicated channel state.
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Like the inter-RAT handover, the inter-frequency handover procedure consists of two steps:
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The inter-frequency measurements
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The inter-frequency handover
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Since IFHO is a hard handover, it employs compressed mode to facilitate inter-frequency measurements.
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LAYER MANAGEMENT for multi multi- 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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