LTE小区重选

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1. Cell selection5.2.3.2    Cell Selection Criterion

The cell selection criterion S is fulfilled when:

Srxlev > 0  AND  Squal > 0

where:

Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation Squal = Qqualmeas – (Qqualmin + Qqualminoffset)

where:

Srxlev	Cell selection RX level value (dB)
Squal	Cell selection quality value (dB)
Qrxlevmeas	Measured cell RX level value (RSRP)
Qqualmeas	Measured cell quality value (RSRQ)
Qrxlevmin	Minimum required RX level in the cell (dBm)
Qqualmin	Minimum required quality level in the cell (dB)
Qrxlevminoffset	Offset to the signalled Qrxlevmin taken into account in the Srxlev evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN [5]
Qqualminoffset	Offset to the signalled Qqualmin taken into account in the Squal evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN [5]
Pcompensation	max(PEMAX –PPowerClass, 0) (dB)
PEMAX	Maximum TX power level an UE may use when transmitting on the uplink in the cell (dBm) defined as PEMAX in [TS 36.101]
PPowerClass	Maximum RF output power of the UE (dBm) according to the UE power class as defined in [TS 36.101]

The signalled values Qrxlevminoffset and Qqualminoffset are only applied when a cell is evaluated for cell selection as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN [5]. During this periodic search for higher priority PLMN the UE may check the S criteria of a cell using parameter values stored from a different cell of this higher priority PLMN.

2. Cell reselection5.2.4.2    Measurement rules for cell re-selection

When evaluating for reselection purposes cell selection criterion or SnonServingCell,x, the UE shall use parameters provided by the serving cell.

Following rules are used by the UE to limit needed measurements:

-     If Sintrasearch is sent in the serving cell and SServingCell > Sintrasearch, UE may choose to not perform intra-frequency measurements.

-     If SServingCell <= Sintrasearch, or Sintrasearch is not sent in the serving cell UE shall perform intra-frequency measurements.        //同频测量条件

-     The UE shall apply the following rules for E-UTRAN inter-frequencies and inter-RAT frequencies which are indicated in system information and for which the UE has priority provided as defined in 5.2.4.1:

-     For an E-UTRAN inter-frequency or inter-RAT frequency with a reselection priority higher than the reselection priority of the current E-UTRA frequency the UE shall perform measurements of higher priority E-UTRAN inter-frequency inter-RAT frequencies according to [10].              //异频高优先级测量条件

-     For an E-UTRAN inter-frequency with an equal or lower reselection priority than the reselection priority of the current E-UTRA frequency and for inter-RAT frequency with lower reselection priority than the reselection priority of the current E-UTRAN frequency:

-     If Snonintrasearch is sent in the serving cell and SServingCell > Snonintrasearch UE may choose not to perform measurements of E-UTRAN inter-frequencies or inter-RAT frequency cells of equal or lower priority.

-     If SServingCell <= Snonintrasearch or Snonintrasearch is not sent in the serving cell  the UE shall perform measurements of E-UTRAN inter-frequencies or inter-RAT frequency cells of equal or lower priority according to [10].   //异频同优先级或者低优先级测量条件

Where SServingCell is the Srxlev-value of the serving cell.

5.2.4.5           E-UTRAN Inter-frequency and inter-RAT Cell Reselection criteria

If threshServingLowQ is provided in SystemInformationBlockType3, cell reselection to a cell on a higher priority E-UTRAN frequency or inter-RAT frequency than the serving frequency shall be performed if:              

-     A cell of a higher priority EUTRAN or UTRAN FDD RAT/ frequency fulfils Squal > ThreshX, HighQ during a time interval TreselectionRAT; or

-     A cell of a higher priority UTRAN TDD, GERAN or CDMA2000 RAT/ frequency fulfils Srxlev > ThreshX, HighP during a time interval TreselectionRAT; and

-        More than 1 second has elapsed since the UE camped on the current serving cell.

Otherwise, cell reselection to a cell on a higher priority E-UTRAN frequency or inter-RAT frequency than the serving frequency shall be performed if:         //异频高优先级小区重选的条件

-     A cell of a higher priority RAT/ frequency fulfils Srxlev > ThreshX, HighP during a time interval TreselectionRAT; and

-        More than 1 second has elapsed since the UE camped on the current serving cell.

Cell reselection to a cell on an equal priority E-UTRAN frequency shall be based on ranking for Intra-frequency cell reselection as defined in sub-clause 5.2.4.6.     //同优先级异频小区和同频小区的重选条件遵循R准则。

If threshServingLowQ is provided in SystemInformationBlockType3, cell reselection to a cell on a lower priority E-UTRAN frequency or inter-RAT frequency than the serving frequency shall be performed if:      

-     The serving cell fulfils Squal < ThreshServing, LowQ and a cell of a lower priority EUTRAN or UTRAN FDD RAT/ frequency fulfils Squal > ThreshX, LowQ during a time interval TreselectionRAT; or

-     The serving cell fulfils Squal < ThreshServing, LowQ and a cell of a lower priority UTRAN TDD, GERAN or CDMA2000 RAT/ frequency fulfils Srxlev > ThreshX, LowP during a time interval TreselectionRAT; and

-     More than 1 second has elapsed since the UE camped on the current serving cell.

Otherwise, cell reselection to a cell on a lower priority E-UTRAN frequency or inter-RAT frequency than the serving frequency shall be performed if:     //低优先级异频小区的重选条件

-     The serving cell fulfils Srxlev < ThreshServing, LowP and a cell of a lower priority RAT/ frequency fulfils Srxlev > ThreshX, LowP  during a time interval TreselectionRAT; and

-     More than 1 second has elapsed since the UE camped on the current serving cell.

Cell reselection to a higher priority RAT/ frequency shall take precedence over a lower priority RAT/ frequency, if multiple cells of different priorities fulfil the cell reselection criteria.

5.2.4.6           Intra-frequency and equal priority inter-frequency Cell Reselection criteria

The cell-ranking criterion Rs for serving cell and Rn for neighbouring cells is defined by:

where:

Qmeas	RSRP measurement quantity used in cell reselections.
Qoffset	For intra-frequency: Equals to Qoffsets,n, if Qoffsets,n is valid, otherwise this equals to zero. For inter-frequency: Equals to Qoffsets,n plus Qoffsetfrequency, if Qoffsets,n is valid, otherwise this equals to Qoffsetfrequency.

The UE shall perform ranking of all cells that fulfil the cell selection criterion S, which is defined in 5.2.3.2, but may exclude all CSG cells that are known by the UE to be not allowed.

The cells shall be ranked according to the R criteria specified above, deriving Qmeas,n and Qmeas,s and calculating the R values using averaged RSRP results.

If a cell is ranked as the best cell the UE shall perform cell reselection to that cell. If this cell is found to be not-suitable, the UE shall behave according to subclause 5.2.4.4.

In all cases, the UE shall reselect the new cell, only if the following conditions are met:

-        the    new cell is better ranked than the serving cell during a time interval TreselectionRAT;

-        more than 1 second has elapsed since the UE camped on the current serving cell.

//36.331

CellReselectionPriority

The IE CellReselectionPriority concerns the absolute priority of the concerned carrier frequency/ set of frequencies (GERAN)/ bandclass (CDMA2000), as used by the cell reselection procedure. Corresponds with parameter "priority" in TS 36.304 [4]. Value 0 means: lowest priority. The UE behaviour for the case the field is absent, if applicable, is specified in TS 36.304 [4].

CellReselectionPriority information element

-- ASN1START

CellReselectionPriority ::=             INTEGER (0..7)

-- ASN1STOP

GCF 6.1.2.4：

with { UE in E-UTRA RRC_IDLE state }

ensure that {

  when { UE detects the cell ranked as the best cell }

    then { UE reselects the new cell }

            }