1 OEO107010 LTE eRAN6.0 Idle Mode ISSUE1.00 C.pdf

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LTE eRAN6.0 Idle Mode

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LTE eRAN6.0 Idle Mode

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LTE eRAN6.0 Idle Mode

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The priority for initial PLMN selection 

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The EHPLMN with the highest priority will be selected. If no such list, then use HPLMN Each combination of PLMN with radio access technology (RAT) in the "User Controlled PLMN Selector with Access Technology" data file in the USIM, in order of priority.

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Each combination of PLMN with RAT in the "Operator Controlled PLMN Selector with Access Technology" data file in the USIM, in order of priority Other combinations of PLMNs with RATs providing high-quality signals, in a random order. A high-quality signal is defined as the Reference Signal Received Power (RSRP) value of a cell in the combination of PLMN with RAT being greater than or equal to -110dBm. Other combinations of PLMNs with RATs in order of descending RX signal quality.

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Cell search is a procedure in which a UE achieves time and frequency synchronization with

a cell, obtains the physical cell identifier (PCI), and learns the RX signal quality and other information about the cell based on the PCI. 

The detailed cell search procedure is as following: 

The UE monitors the P-SCH to achieve clock synchronization with a maximum synchronization error of 5 ms. The UE determines the cell identity in a cell identity group based on the mapping between cell identities and primary synchronization signals.

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The UE monitors the S-SCH to achieve frame synchronization, that is, time synchronization with the cell. Cell identity groups have a one-to-one relationship with secondary synchronization signals. Therefore, the UE acquires the number of the cell identity group to which the cell identity belongs by monitoring the S-SCH. The UE monitors the Broadcast Channel (BCH) to acquire other information about the cell The UE determines the PCI based on the cell identity and the cell identity group number. The UE monitors the downlink reference signal to acquire the RX signal quality in the cell

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The stored information cell search: It requires stored information on carrier frequencies and

information on cell parameters. The information is obtained from previously received measurement control information elements or from previously detected SI messages of cells. 

Initial cell search: If there is no prior knowledge of frequency information, the UE scans all RF channels in the E-UTRAN bands according to its capabilities in order to find a suitable cell. On each carrier frequency, the UE searches for the strongest cell only.

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Period of MIB: 40ms

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A UE considers an E-UTRAN cell as a suitable cell only when the measured RSRP and

reference signal received quality (RSRQ) values of the cell are greater than the receive (RX) level threshold (Qrxlevmin) and the RX signal quality threshold (QQualMin) for the cell, respectively. 

An E-UTRAN cell becomes a suitable cell when both the following conditions are met: 

Srxlev > 0 Squal > 0

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Srxlev = Qrxlevmeas - (Qrxlevmin + Qrxlevminoffset) – Pcompensation

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Squal = Qqualmeas - (QQualMin + QQualMinOffset)

Parameter

Description

Qrxlevmeas

Measured RSRP value

Qrxlevmin

Minimal Required Rx level (dBm) in SIB1

Qrxlevminoffset

Offset to Srxlev, relative with PLMN priority ,.QrxlevminOffset is 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 in SIB1

Pcompensation

max (PMaximum allowed power – PUE MAX Output Power, 0), where PMaximum allowed power is sent in SIB1

Qqualmeas

measured RX signal quality (RSRQ value) of the cell, expressed in units of dB.

Qqualmin

Minimal required signal quality

QQualMinOffset

Offset to Qqualmin, relative with PLMN priority ,.QrxlevminOffset is 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 in SIB1

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Following are the description of each parameters: Parameter ID

Description

Qrxlevmin

Indicates the minimum required RX level. This parameter is used in the formula of the cell selection criterion S.

Qrxlevminoffset

Indicates the offset to the minimum required RX level. This value is included in criteria S and used in the evaluation of cell selection. This parameter is valid only when the cell selection is triggered by periodic searches for higher-priority PLMNs and the UE is served by a Visited Public Land Mobile Network (VPLMN).

Qqualmin

Indicates the minimum RX level of the cell. It is included in criteria S and used in the evaluation of cell selection.

QQualMinOffsetCfgInd Indicates whether to set the offset to the minimum required RX qulity for the cell. If this parameter is set to CFG, the offset is required. If this parameter is set to NOT_CFG, the offset does not need to be set.

QQualMinOffset

Indicates the offset to the minimum required RX quality for the cell. It is included in criteria S and used in the evaluation of cell selection. This parameter is required only when the cell selection is triggered by periodic searches for higherpriority PLMNs and the UE is served by a Visited Public Land Mobile Network (VPLMN).

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UE cell reselection include two steps: 

Start the measurement for the neighboring cells

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Rank the measured cells based on radio signal quality and priorities.

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After having camped on a cell, a UE may decide to camp on another cell by performing cell

reselection. Before cell reselection, the UE is required to measure the signal strength of certain neighboring cells and evaluate each of them by using the criteria that are suitable according to the priority of the neighboring cell, that is, the priority of the frequency on which the neighboring cell operates. 

During the measurements and implementation of cell reselection, the UE needs to obtain the priorities of neighboring frequencies. Note that any two RATs must have nonoverlapping priorities of frequencies. During the evaluation for reselection to an intrafrequency neighboring cell, the UE ignores the priority of the target frequency because cells that work on the same frequency have the same priority.

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Frequencies of different RATs must have different priorities.

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The priorities of E-UTRAN frequencies and inter-RAT frequencies are classified into the following types: 

Absolute priority: This priority is specified by the CellReselPriority parameter and is sent to UEs through broadcast of system information. Serving cell frequency priority will be delivered in SIB3, inter-frequency priority will be delivered in SIB5, 3G frequency priority will be delivered in SIB6 and 2G frequency priority will be delivered in SIB7.

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Dedicated priority: The dedicated priority of an E-UTRAN or inter-RAT frequency is UEspecific. It is delivered to the UE in an RRC Connection Release message when the UE's radio resources are released.

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This priority will be broadcast in SIB3

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This priority will be broadcast in SIB5

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3G frequency will be broadcast in SIB6 and 2G frequency will be broadcast in SIB7.

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Note: The dedicated priority of frequencies for one RAT must be all different from those

for another RAT.

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If the threshold is set to “CFG”, these two thresholds(SIntraSearch and SIntraSearchQ) will

be delivered in SIB3.

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From SIB ,UE can get the serving cell and inter frequency/RAT neighbors’ priorities.

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For the high priority cells, UE measure them always, for the low priority cells, UE measure them in case of the serving cell signal is lower than the threshold.

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The intra frequency cells have the same frequency priority, frequencies of different RATs must have different priorities.

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Following are description of parameters: Parameter ID

Description

Threshold for non-intra Indicates whether to set the measurement triggering freq measurements threshold for reselection to inter-frequency or inter-RAT cells. configure indicator QRxLevMin

Indicates the minimum required RX level used in intrafrequency E-UTRAN cell reselection, which corresponds to the IE q-RxLevMin in SIB3. This value is included in criteria R and used in the evaluation of cell

SIntraSearchCfgInd

Indicates the minimum RX level of the cell. It is included in criteria S and used in the evaluation of cell selection.

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Following are description of parameters: Parameter ID

Description

SIntraSearchQ

Indicates the RSRQ threshold for starting intra-frequency measurements. It determines the probability of triggering cell reselection to an intra-frequency neighboring cell.

SNonIntraSearchQ

Indicates the RSRQ threshold for starting inter-frequency or inter-RAT measurements. It determines the probability of triggering cell reselection to an inter-frequency or inter-RAT neighboring cell.

QQualMin

Indicates the minimum required RX signal quality used in intra-frequency E-UTRAN cell reselection, which corresponds to the IE q-QualMin in SIB3. This value is included in criteria R and used in the evaluation of cell reselection.

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A UE makes a cell reselection decision according to cell reselection criteria. When making a

decision on reselection to an intra frequency or equal-priority inter frequency cell, the UE checks whether the signal quality of a neighboring cell is higher than that of the serving cell. 

The cell-ranking criteria R_s for the serving cell and R_n for neighboring cells are defined as follows: 

R_s = Qmeas,s + Qhyst

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R_n = Qmeas,n - CellQoffset

Where:  

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Qmeas_s is the measured RSRP of the serving cell, expressed in units of dBm Qhyst is the hysteresis for the serving cell used in the ranking criteria, expressed in units of dB. Qmeas_n is the measured RSRP of the neighboring cell, expressed in units of dBm CellQoffset is the offset for the neighboring cell used in the ranking criteria, expressed in units of dB

According to the cell reselection criteria, the UE should reselect the new cell only if both the following conditions are met: 

The new cell is ranked higher than the serving cell during the cell reselection time.

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More than one second has elapsed since the UE camped on the serving cell.

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Following are description of parameters Parameter ID

Description

Qhyst

Indicates the hysteresis for cell reselection when RSRP values are used in the evaluation. This parameter must be set based on the slow fading characteristic of the area covered by the cell. The greater the slow fading variance is, the larger the value of this parameter must be set to. A larger value of the hysteresis results in a larger boundary of the serving cell and a higher probability of cell reselection to neighboring cells

TReselEutran

Indicates the cell reselection duration of the E-UTRAN. When the signal quality of the new cell is better than the serving cell all the time and the UE stays in the current serving cell for more than 1s, the UE is initiating cell reselection request to the new cell.

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Following are description of parameters: Parameter ID

Description

CellQoffset

Indicates the offset for the intra-frequency neighboring cell, which is used in evaluation for cell reselections. A larger value of this parameter results in a lower probability of cell reselections. If this parameter is not set to dB0, it is delivered in SIB4 or SIB5.

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For EUTRAN and UTRAN, either Srxlev or Squal could be used for cell reselection, depends on the following parameter: 

If ThrshServLowQCfgInd is set “CFG”,then it use Squal

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Otherwise, it use Srxlev

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For GERAN, it only uses Srxlev

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Srxlev and Squal evaluation is the same as cell selection algorithm.

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If SIB3 contains the value of ThrshServLowQ, a UE performs reselection to a higher-priority interfrequency or inter-RAT neighboring cell when both the following conditions are met: 

The neighboring cell has one of the following measurement results: 



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The Squal value of the evaluated neighboring E-UTRAN or UTRAN cell is always greater than the RX signal quality threshold used in reselection to higher-priority cells (ThreshXHighQ) during the cell reselection time specified by the TReselEutran or TReselUtran parameter. The Srxlev value of the evaluated neighboring GERAN or CDMA2000 cell is always greater than the RX signal level threshold used in reselection to higher-priority cells (ThreshXHigh) during the cell reselection time specified by the TReselGeran or Cdma1XrttTreselection parameter

The UE has camped on the serving cell for more than 1 second.

If SIB3 does not contain the value of ThrshServLowQ, a UE performs reselection to a higherpriority inter-frequency or inter-RAT neighboring cell when the following conditions are both met: 

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The Srxlev value of the evaluated neighboring cell is always greater than the ThreshXHigh value during the predefined cell reselection time The UE has camped on the serving cell for more than 1 second

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If SIB3 contains the value of ThrshServLowQ, a UE performs reselection to a lower-priority interfrequency or inter-RAT neighboring cell when all the following conditions are met:  

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No cell meets the criteria for reselection to higher-priority cells The Squal value of the serving cell is always less than the RX signal quality threshold for the serving cell used in reselection to lower-priority cells (ThrshServLowQ) during the predefined cell reselection time. The neighboring cell has one of the following measurement results: 

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The Squal value of the evaluated neighboring E-UTRAN or UTRAN cell is always greater than the RX signal quality threshold used in reselection to lower-priority cells (ThreshXLowQ) during the predefined cell reselection time. The Srxlev value of the evaluated neighboring GERAN or CDMA2000 cell is always greater than the RX signal level threshold used in reselection to lower-priority cells (ThreshXLowQ) during the predefined cell reselection time.

The UE has camped on the serving cell for more than 1 second

If SIB3 does not contain the value of ThrshServLowQ, a UE performs reselection to a lower-priority inter-frequency or inter-RAT cell when all the following conditions are met:  

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No cell meets the criteria for reselection to higher-priority cells The Srxlev value of the serving cell is always less than the RX signal level threshold for the serving frequency used in reselection to lower-priority cells (ThrshServLow) during the predefined The Srxlev value of the evaluated neighboring cell is always greater than the threshold used in reselection to lower-priority cells (ThreshXLow) during the predefined cell reselection time cell reselection time. The UE has camped on the serving cell for more than 1 second

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