Idle Mode Mobility Management from WCDMA
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Idle Mode Mobility Management from WCDMA
Inter-layer Mobility Parameters [FL19A, WCDMA19, GSM19]
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Idle Mode Mobility Management from WCDMA
Module Objectives
After completing this module, you will be able to:
- Describe the processes and parameters for Idle Mode mobility
(Cell Selection and Re-selection) from WCDMA to LTE and 2G
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Idle Mode Mobility Management from WCDMA
Module content
• Cell Reselection Overview
• RAN2067 LTE Interworking
• RAN3069: RSRQ-based LTE Reselection
• Appendix: Hierarchical Cell Structures (HCS)
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Idle Mode Mobility Management from WCDMA
Cell Reselection Overview
Cell Reselection in the RRC Idle and RRC Connected Mode.
• As soon as a UE camps on a cell, it has to wait 1 second and start periodically looking for a better cell to camp on.
• But what is a “better“ cell?
- “legacy rank based” or “priority based”
- A cell that meets the cell selection criteria of BCCH parameters, it is a better cell to camp on
?
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If the UE camps normally on a cell, it is responsible to:
•
Monitor the BCCH;
•
Listen for paging;
•
serving cell measurements periodically;
•
neighboring cell measurements;
•
cell reselection, to a better cell;
•
Move the UE to the internal state Any cell selection, if no suitable cell can be found.
•
The BCCH also delivers the neighborhood list to the UE.
•
Ranks the cells to determine the best suitable cell for cell reselection.
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Idle Mode Mobility Management from WCDMA
WCDMA Cell Reselection Mechanisms
From R8 on, a WCDMA UE will do cell reselection using either:
legacy Ranking Based
(qHyst and qOffset broadcast via SIBs)
or
legacy HCS
(HCS relative parameters broadcast via SIBs)
or
new APR based If RAN2067 is enabled
(CRP relative parameters broadcast via SIBs)
•
Ranking based cell reselection mechanism simple compares the measured results with offsets from serving cell and
neighbor cells
•
HCS (Hierarchical Cell Structure) is more complicated mechanism with priorities defined on cell level. (see appendix)
•
APR (Absolute Priority-based Reselection) mechanism is a simplified version with priorities compared to HCS, with
frequency (group for GSM) layer level priory.
•
The mechanisms are standardized by 3GPP (25.304) and exclude each other.
•
APR is mandatorily used for reselection to other layer or RAT.
•
With RAN2881 (WCDMA and GSM Layer Priorities) we can assign each IF WCDMA layer (carrier) or group of GSM
frequencies with a number indicating how much it is preferred compared to other layers. The layer preferences
applies to idle mode and PCH/URA-PCH.
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The feature implements 3GPP mechanism for inter-freq or inter-RAT cell reselection using layers priorities,
alternative to HCS.
•
The implemented mechanism supports idle mode and connected mode (PCH,URA) priority-based reselection
WCDMA to WCDMA and WCDMA to GSM.
•
The operator is able to set priorities for IF layers or GSM frequencies (or groups).
•
Prioritization of WCDMA and GSM layers (LTE via RAN2067/RAN3069) is done via eight distinct priority levels
(0 through 7).
•
Priorities are broadcasted in SIB19 messages(first time introduced in RU20 by RAN2067).
•
The feature requires 3GPP Rel-8 compliant UEs & implements Rel-8 reselection criterions.
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Idle Mode Mobility Management from WCDMA
Srxlev metric in WCDMA cell selection:
In 3GPP terminology Srxlev is a metric based on received P-CPICH power and determines how
much the received RSCP is better than minimum level (WCEL:Qrxlevmin broadcasted in SIB3)
required for cell selection (in other words, how far the UE is from entering ”out of coverage” state):
Cell selection
Srxlev=RSCPP-CPICH _ServingCell – WCEL:QrxlevMin – max (WCEL:UEtxPowerMaxPRACH – UE_PWR_MAX,0)
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Srxlev metric in WCDMA APR reselection procedures
• The APR reselection mechanism use SrxlevservingCell & Srxlevnon-serving metrics comparing
signal level with minimum required on given layer. That is indicating how far the UE camped on
current cell is, or on target layer would be, from entering „out of coverage” state:
Absolute Priority Reselection
SrxlevservingCell=RSCPP-CPICH _ServingCell – WCEL:QrxlevMin (SIB3)
Srxlevnon-serving,FDD=RSCPP-CPICH_non-ServingCell ,FDD – HOPI:AdjiQrxlevminFDD (SIB19)
Srxlevnon-serving,LTE=RSRPnon-ServingCell ,LTE – HOPL:AdjLQrxlevminEUTRA (SIB19)
Srxlevnon-serving,GSM=RXLEVnon-ServingCell _GSM – HOPG:AdjgQrxlevmin (SIB19)
• The min required signal levels for neighboring frequency layers/groups are broadcasted in SIB19.
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Idle Mode Mobility Management from WCDMA
Squal metric in WCDMA cell selection & APR reselection procedures
• Similarly to Srxlev, the Squal is a relative metric and determines how much the received CPICH Ec/No is better then
the minimum level (WCEL:QqualMin broadcasted in SIB3) required for cell selection. In other words, how far the UE
is from entering „out of coverage” state due to signal quality reason:
Cell selection
Squal=Ec/NoP-CPICH _ServingCell – WCEL:QqualMin (SIB3)
• The APR reselection mechanism use SqualServingCell and Squalnon-serving metrics comparing current and
neighbor quality with minimum level required on the layer. That is indicating how far UE on current layer is, or would
be on the target layer, from entering „out of coverage” state:
SqualServingCell=Ec/NoP-CPICH_ServingCell – WCEL:QqualMin (SIB3)
Absolute Priority Reselection
Squalnon-serving,FDD=Ec/NoP-CPICH_nonServingCell,FDD – HOPI:AdjiQqualminFDD (SIB19)
Squalnon-serving,LTE=RSRQnonServingCell,LTE – HOPL:AdjLQqualminEUTRA (SIB19)
• The minimum quality levels required for neighboring frequency layers are broadcasted in SIB19.
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Idle Mode Mobility Management from WCDMA
APR Cell Reselection Summary
Phase1: Neighbor Measurement Trigger
Phase2: Reselection Criteria ( > Tresel )
(implicit: Snei > 0, both Srxlev & Squal)
Always
Snei > Threshold high
to Higher
Intra-Freq
Sserv_qual ≤ Sintrasearch
Inter-Freq
Sserv ≤ Sprioritysearch1/2
to Equal
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to Lower
Sserv ≤ Sprioritysearch1/2
Notes:
Sserv means serving cell’s:
• Srxlev (based on RSCP) OR
• Squal (based on EcNo).
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Rn > Rs where:
Rs ＝ EcNo/RSCP_s + Qhysts1/2
Rn ＝ EcNo/RSCP_n－Qoffset1/2_s,n
1. Snei_rxlev > Threshold low
2. Sserv < Threshold serv,low/2
1. Snei > Threshold low/2
2. Sserv < Threshold serv,low/2
Snei means neighbor cell’s:
• Srxlev (for IF or GSM or R8_LTE) OR
• Squal (for R9+_LTE).
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See 3GPP TS25.304:5.2.6.1 for details.
•
RAN2881 is for IF/GSM reselection: ①To higher prioritized IF/GSM neighbor, only neighbor’s RSCP/RxLev
is concerned;
②To equal or lower prioritized IF/GSM neighbor, both neighbor’s RSCP/RxLev
and serving’s RSCP/EcN0 are concerned.
•
RAN3069 is for LTE reselection only, and cares only quality for both WCDMA serving cell (Ec/N0) and
higher/lower LTE neighbor cells (RSRQ).
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Idle Mode Mobility Management from WCDMA
Initiation of neighbor cells measurements
Legacy ranked-based
reselection
Serving
Srxlev /
Squal
Serving
Squal
(Inter-freq or inter-RAT)
Sintrasearch
Sintrasearch
Intra-freq reselections
Inter-freq reselections
(measurements stared below Sintersearch)
Legacy intra-freq reselections
(rank-based)
(measurement started below Sintrasearch)
SsearchRAT
Here assumed: enabled for IF & GSM
Higher priority layer reselections
No reselections
(signal of the current cell is good enough)
Sintersearch
Absolute prioritybased reselection
Sprioritysearch1 for RSCP
or
Sprioritysearch2 for EcNo
Equal/lower priority layer
reselections
(inter-freq or inter-RAT)
Inter-RAT reselections
(measurements started below SsearchRAT)
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Idle Mode Mobility Management from WCDMA
APR: Layer Priorities
•
The APR mechanism is intended only for reselection of inter-freq WCDMA or inter-RAT cells.
•
Reselection of intra-freq cells use legacy cell ranking-based mechanism.
•
UEs search the IF/inter-RAT layers in their priority order, looking for a suitable cell.
•
•
Higher priority layers are considered first.
•
If no cell is found then IF WCDMA equal priority layers are checked.
•
If still no result, the lower priority layers are tried (WCDMA or inter-RAT).
Additional to reselection to LTE, APR may be applied to 1) IF WCDMA & GSM or 2) only IF WCDMA or 3) only GSM layers.
•
In 2) the cell ranking reselection is used for GSM,
•
In 3) the cell ranking reselection is used for WCDMA.
Cell ranking
based reselection
Priority based
reselection
WCDMA, f1, prio=5
(macro)
WCDMA, f1, prio=5
(macro)
WCDMA, f2, prio=5
(macro)
WCDMA, f2, prio=5
(macro)
WCDMA, f2, prio=5
(macro)
GSM, group1, prio=3
GSM, group1, prio=3
WCDMA, f3, prio=6 (micro)
GSM, group1, prio=3
Start searching for high priority, then equal priority and finaly lower priority
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Idle Mode Mobility Management from WCDMA
APR – reselecting higher priority layer cell (1/2)
▪ When APR is in use & UE camped on WCDMA cell, the higher priority layers are considered first for inter-freq or interRAT neighbors search.
▪ UE always periodically measures neighbor cells on higher prioritized layers, irrespectively of current cell received
power/RSCP or quality/EcNo (only the rate of measurements is influenced).
▪ The neighbor cell on higher priority layer is reselected if its signal (Srxlev) by at least T reselection (WCEL:Treselection or
WCEL:TreselectionPCH) time is good enough, that is above threshold Threshx,high (HOPI:AdjiThreshigh or
HOPG:AdjgThreshigh).*
* HOPL:AdjlThreshold & reselection of LTE layer is covered by RAN2067 LTE Interworking feature
▪ The neighbor with highest signal level (Srxlev) is selected in case more then one are available on prioritized layer
(3GPP Release 8).
Srxlev [dB]
AdjxThreshigh
Treselection
Current cell
High priority
layer cell
Reselect high
priority cell
time
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If APR is in use (signaled in current cell) and no priority is defined for the current cell it is
assumed to have lowest priority then any of 8 available
If priority for all IF layers are not defined then cell ranking based reselection is used wrt IF
cells.
If priority for all inter-RAT carriers (groups) are not defined then cell ranking based reselection
is used wrt inter-RAT cells.
If any IF layer has priority signalled then APR mechanism is applied wrt all IF cells (similar for
inter-RAT).
If ARP is in use then IF or inter-RAT cells on layers with no priority (or threshold) defined are
omitted
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Idle Mode Mobility Management from WCDMA
APR – reselecting higher priority layer cell (2/2)
▪ Higher priority IF WCDMA or inter-RAT cell is reselected when:
a) Srxlevnon-servingCell > HOPx:AdjxThreshigh
RAN2881
or
b) Squalnon-servingCell > HOPL:AdjLThreshigh2
RAN3069
for at least WCEL:Treselection or WCEL:TreselectionPCH (idle or PCH/URA)
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Idle Mode Mobility Management from WCDMA
APR – trigger of measurement for lower or equal priority layer cell
Lower or equal priority layers are measured when :
• current cell signal level is below/equal to WCEL:Sprioritysearch1
• or quality is below/equal to WCEL:Sprioritysearch2
Reselect low/equal
priority cell
Srxlev [dB]
Treselection
Low priority layer
cell
Threshservlow
AdjxThreshservlow
Current cell
time
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▪ Lower priority layers are measured when current cell signal is below/equal to
WCEL:Sprioritysearch1 or quality is below/equal to WCEL:Sprioritysearch2.
▪ First the IF WCDMA neighbors are searched on equal priority layers. If not found, then
neighbors on lower priority layers are evaluated (IF or inter-RAT). The search is triggered
only when current cell signal dropped below min required level (WCEL:Threshservlow) or
UE lost the network.
The neighbor can be reselected when its signal is good enough for at least T reselection
(WCEL:Treselection or WCEL:TreselectionPCH) time. That is its Srxlev is above
Threshx,low threshold (HOPI:AdjiThreshlow or HOPG:AdjgThreshlow.
▪ When more neighbors on certain priority layer fulfils APR reselection condition then one with
highest signal (Srxlev) is selected.
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Idle Mode Mobility Management from WCDMA
APR – reselect equal priority layer cell
▪ Equal priority IF WCDMA cell is reselected when:
a) SrxlevServingCell < WCEL:Threshservlow
and
Srxlevnon-serving,x > HOPI:Threshlow
for at least WCEL:Treselection or WCEL:TreselectionPCH (idle or PCH/URA)
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Idle Mode Mobility Management from WCDMA
APR – reselect lower priority layer cell
▪ Lower priority IF WCDMA or inter-RAT cell is reselected when:
a) SrxlevServingCell < WCEL:Threshservlow
RAN2881
and
Srxlevnon-serving,x > HOPx:Threshlow
or*
b) SqualServingCell < WCEL:Threshservlow2
and
Squalnon-serving,x > HOPL:Threshlow2
RAN3069
for at least WCEL:Treselection or WCEL:TreselectionPCH (idle or PCH/URA)
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* Note: the criteria (b) is:
• applicable only to LTE neighbors (3GPP SIB19 does not include the quality threshold for IF
WCDMA layers)
•available with RAN3069 enabled (RU50 extensions to RAN2067) and applied when both
AdjLThreshigh2 & AdjLThreshlow2 are broadcasted
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Idle Mode Mobility Management from WCDMA
SIB19 content
• Priority based reselection is signaled in SIB19, if enabled by license(s) & cell level parameter(s).
• In RU20 the LTE priority list and UTRAN serving cell info is broadcast (RAN2067).
• In RU50 also IF & GSM priorities and parameters can be included (RAN2881).
WCDMA
M = mandatory
utra-PriorityInfoList
gsm-PriorityInfoList
eutra-FrequencyAndPriorityInfoList
O = optional
M
M Serving cell info - RAN2881 or RAN2067 activated
O Utran priority info - WCEL:WCDMACellReselection=Enabled
(RAN2881)
O
GSM priority info - WCEL:GSMCellReselection=Enabled
(RAN2881)
O
LTE priority info - WCEL:LTECellReselection=Enabled
(RAN2067)
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SIB19 content / UTRAN Priority Info - mapping to new and existing parameters
SysInfoType19
│ utra-PriorityInfoList:
│ │ utra-ServingCell:
│ │ │ priority: 5
│
││ s-PrioritySearch1: 31
│ │ │ s-PrioritySearch2: 7
│ │ │ threshServingLow: 0
│ │ utran-FDD-FrequencyList: SIZE: 1
│ │ │ utran-FDD-FrequencyList(0):
│ │ │ │ uarfcn: 10568
│ │ │ │ priority: 4
│ │ │ │ threshXhigh: 18
│ │ │ │ threshXlow: 4
│ │ │ │ qQualMinFDD: -16
│ │ │ │ qRxLevMinFDD: -56
│ gsm-PriorityInfoList:
WCEL
•A b s P r i o C e l l R e s e l e c
3G Serving
• Sprioritysearch1
• Sprioritysearch2
• Threshservlow
Existing
parameters
• AdjiRtHopiIdentifier
ADJI
• AdjiUARFCN
HOPI
• AdjiAbsPrioCellReselec
• AdjiThreshig h
• AdjiThreslow
3G Neighbours
• AdjiQqualminFDD
• AdjiQrxlevminFDD
New parameters
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Note: qRxLevMinFDD is only included if HOPI:AdjgQrxlevminFDDWCEL:Qrxlevmin
qQualMinFDD is only included if HOPI:AdjiQqualminFDD WCEL:Qqualmin
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SIB19 content / UTRAN Priority Info – selection of parameter set
HOPI template (WCDMA absolute priority)
HOPI_ID
1
2
3
4
AdjiAbsCellReselect
5
4
N/A
5
Layer 1, priority 5
(HOPI_1 param. used)
3G cell_1
HOPI_1
3G cell_2
HOPI_4
3G cell_3
HOPI_2
3G cell_4
Layer 2, priority 5
AbsPrioCellReselec=5
Layer 3, not enabled for priority
based reselection
3G cell_5 HOPI_3
reselection possible
reselection not possible
When neighbors on same carrier use different HOPI templates, the one with highest priority is taken
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• The HOPI template assigned to ADJI:RtHopiIdentifier is used to determine WCDMA
absolute priority parameters broadcast in UTRAN Priority Info list of SIB19.
• Absolute priorities are defined per frequency layer, thus cells on same carrier should have
same priority.
• When neighbors on same carrier use different HOPI templates, the one with highest priority
is taken (AdjiAbsPrioCellReselec), to determine absolute priority parameters for given
WCDMA layer.
• When more HOPI with the same, highest priority are used by neighbors on same carrier, the
one having lower HOPI_ID number is applied.
• If inter-frequency absolute priority reselection mechanism is in use, then neighbors on IF
layers not included in SIB19 are not considered by UE for reselection.
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Idle Mode Mobility Management from WCDMA
SIB19 content GSM Priority Info - mapping to new or existing parameters
SysInfoType19
│ utra-PriorityInfoList:
│ · · · · · · · · · ·
│ gsm-PriorityInfoList:
│ │ gsm-PriorityInfo(0):
│ │ │ gsmCellGroup(0):
│ │ │ │ startingARFCN: 736
│ │ │ │ bandIndicator: dcs1800
│ │ │ │ followingARFCNs:
│ │ │ │ │ explicitListOfARFCNs: 736,
│ │ │ │ priority: 3
│ │ │ │ qRxLevMinGSM: -51
│ │ │ │ threshXhigh: 31
│ │ │ │ threshXlow: 21
ADJG
• AdjgBandInd ic ator
• AdjgBCCH
• AdjgRtHopiId entifier
• AdjgQrxlevm in
HOPG
• AdjgAbsPrio C ellR eselec
• AdjgThresh igh
• AdjgThreslow
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SIB19 content / GSM Priority Info – selection of parameter set
Layer 1, priority 3
(HOPG_1 param. used)
HOPI template
HOPG_ID
1
2
3
4
AdjiAbsCellReselect
3
2
N/A
3
2G cell_1
HOPG_4
2G cell_2
HOPG_1
2G cell_3
HOPG_2
3G cell_4
Layer 2, priority 5
AbsPrioCellReselec=5
Layer 3, not enabled for priority
based reselection
2G cell_5
HOPG_3
reselection possible
reselection not possible
When neighbors from same group use different HOPG templates, the one with highest priority is taken
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The HOPG template assigned to ADJG:RtHopgIdentifier is used to determine GSM absolute priority parameters
broadcast in GSM Priority Info list of SIB19.
Absolute priorities are defined per frequency group, thus any neighbor using same band indicator and BCCH
should have same priority.
When neighbors from same group use different HOPG templates, the one with highest priority is taken
(AdjgAbsPrioCellReselec), to determine absolute priority parameters for given group.
When more HOPG with the same, highest priority are used by neighbors in same group the one having lower
HOPG_ID number is applied.
If inter-RAT GSM absolute priority reselection mechanism is in use, then neighbors using frequencies not included
in any frequency group in SIB19 are not considered by UE for reselection.
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SIB19 content / 3GPP Rel9 extensions and mapping to new parameters
• The 3GPP Rel9 extensions to SIB19 are part of RSRQ-based LTE reselection feature (RU50 extension of
RAN2067) and are mentioned here only for information completeness (SIB19 content in RU50).
SysInfoType19
│ utra-PriorityInfoList:
│ gsm-PriorityInfoList:
│ eutra-FrequencyAndPriorityInfoList:
│ v920NonCriticalExtensions:
│ │ utra-PriorityInfoList-v920ext:
│ │ │ threshServingLow2: 2
│ │ eutra-FrequencyAndPriorityInfoList-v920ext:
│ │ │ qqualMinEUTRA: -34
│ │ │ threshXhigh2: 32
│ │ │ threshXlow2: 31
WCEL
• Threshservlow2
• AdjLQqual mi nEUTRA
• A d j LT h r e s h i g h 2
• A d j LT h r e s l o w 2
HOPL
RAN2067 – RU50 extensions
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Module content
•
•
•
•
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Cell Reselection Overview
RAN2067 LTE Interworking
RAN3069: RSRQ-based LTE Reselection
Appendix: Hierarchical Cell Structures (HCS)
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RAN2067 LTE Interworking
Brief Introduction of LTE interworking:
Benefits:
LTE rollout phase support
In the initial phase the LTE coverage is limited and
UEs easily run out of it.
LTE cell reselection
LTE-users who did cell selection to WCDMA due to
coverage reasons are able to automatically return to
LTE in case LTE RAT becomes available again.
•
•
This feature has successfully passed Interoperability Tests (IOT) for FDD LTE mode.
These tests consider UEs from multiple vendors.
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Brief Description:
• This feature supports priority based cell reselection from WCDMA to FDD and TDD LTE
modes
• The operator is able to set priorities for cells belonging to different RATs
• Prioritizing WCDMA and LTE RATs with eight distinct priorities
• Priorities are handled by newly introduced SIB19 broadcast message
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RAN2067 LTE Interworking
Mobility states
This feature enables the LTE cell reselection when UE is in one of the following mobility states:
UTRAN Connected Mode
Cell_PCH
URA_PCH
Cell_DCH
Cell_FACH
Establish RRC
Connection
Release RRC
Connection
Idle mode
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Idle Mode
• UE stays in idle mode until it transmits a request to establish an RRC connection. In
idle mode the connection of the UE is closed on all layers of the UTRAN.
Cell_PCH
• No dedicated physical channel is allocated to the UE.
• The UE uses discontinuous reception (DRX) for monitoring a paging channel (PCH)
through an allocated paging indicator channel (PICH).
• No uplink activity is possible.
URA_PCH
• The URA_PCH state is very similar to the Cell_PCH state. The main difference is that
UE executes URA Update when the URA area changes, and when paging needs to be
initiated, it is sent to all cells within the URA area.
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RAN2067 LTE Interworking
SIB19 message – 3G part
The System Information Block type 19 contains Inter-RAT frequency and priority information for cell reselection
MIB
SIB19
SIB3
SIB4
SIB5
SIB11
Information Element/ Group name
…
Description
UTRA priority info list
Provides priority based reselection information for UTRA
E-UTRA frequency and priority info list
Provides priority based reselection information for E-UTRA
• This is the list of available UTRA layers – this list is used by RAN2067 feature to get the WCDMA serving cell
priority:
• Serving Layer Priority – WCDMA serving cell priority
• Additional threshold parameters used for define measurement rules and reselection criteria
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RAN2067 LTE Interworking
SIB19 message – LTE part
The System Information Block type 19 contains Inter-RAT frequency and priority information for cell reselection
MIB
SIB19
SIB3
SIB4
SIB5
SIB11
Information Element/ Group name
…
Description
UTRA priority info list
Provides priority based reselection information for UTRA
E-UTRA frequency and priority info list
Provides priority based reselection information for E-UTRA
• This is the list of available E-UTRA frequencies – items are characterized by:
• E-UTRA Absolute Radio Frequency Channel Number (EARFCN)
• Measurement bandwidth – it indicates the number of resource blocks over which the UE could measure
• LTE layer priority - 0 indicates the lowest absolute priority and 7 indicates the highest absolute priority
• Cell Reselection Minimum RX level – it determines the minimum required Reference Signal Received Power (RSRP) level which the
measurement result of the E-UTRA/LTE neighbor cell must exceed before the cell reselection becomes possible
• Additional threshold parameters used for define measurement rules and reselection criteria
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Measurement rules for the UE camped in WCDMA cell
If the UE has received absolute priority information for different layers, the UE shall follow these rules:
• It is mandatory that a UE perform measurements of layers with a priority higher than the priority of the current serving layer
Priority 7
LTE layer
Priority 5
WCDMA layer 1
Priority 5
WCDMA layer 2
The UE is camped in
WCDMA layer 1 cell.
In this case, UE
measures LTE layer
with priority 7
• It is possible that the UE measures equal or lower priority layers. Any one of the following rules on serving cell need to be fulfilled to do so:
• RX level (measured as Received Signal Code Power at Common Pilot Channel [CPICH RSCP] level) in the serving cell falls below threshold
SrxlevServingCell <= Sprioritysearch1
Or
• Quality level (measured as energy per modulating bit to the noise spectral density [CPICH Ec/No] ratio) in the serving cell falls below threshold
SqualServingCell <= Sprioritysearch2
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where:
• SrxlevServingCell = Qrxlev_meas – Qrxlevmin; Squal = Qqual_meas – QqualMin
• Sprioritysearch1, Sprioritysearch2 are operator configurable parameters broadcast via
SIB19 message
• There also is a basic parameter Wcel:CellSelQualMeas broadcast via SIB3/4/11/12, indicating what a UE
concerns (RSRP / EcNo) for cell selection and reselection using traditional Ranking criteria. It doesn’t play a
role when absolute priorities are applied after Rel.8.
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WCDMA
coverage
Reselection Criteria (all RATs)
LTE
coverage
Reselection to higher priority layer
SrxLevNonServingCell > AdjLThreshigh during the Treselection time period
Reselection to equal priority layer
SrxLevNonServingCell > AdjLThresLow during the Treselection time period
Reselection to lower priority layer
Priority 7
LTE layer
Priority 5
WCDMA layer 1
Priority 5
WCDMA layer 2
Priority 3
WCDMA layer 3
SrxLevServingCell < Threshservlow
and
SrxLevNonServingCell > AdjLThresLow
Both conditions during the Treselection time period
If more than one cell meets the above criteria, the UE reselects the cell with the highest SrxlevNonServing Cell among the cells meeting the
criteria on the highest absolute priority layer.
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where:
SrxLevNonServingCell = Qrxlev_meas – Qrxlevmin
Orxlev_meas in LTE cell is measured as Reference Signal Received Power (RSRP) level
Threshservlow is a threshold related to radio conditions in current serving cell below which the
UE may perform cell reselection to lower priority layer. This parameter is operator configurable
and broadcast via SIB19 message.
AdjLThreshigh, AdjLThreslow are operator configurable parameters defining the required
quality in cell to which the UE performs cell reselection procedure (broadcast via SIB19
message.
Treselection is a parameter defining the time period for which the cell reselection criteria need
to be fulfilled to trigger the reselection of a new cell . Depend on current mobility state UE
uses Treselection or TreselectionPCH timer. These parameters are broadcast via SIB3, SIB4
messages.
The additional restriction is that the UE cannot reselect to any cell if it is camped to the
current serving cell less than 1 second.
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Consequent TAU after Cell reselection from WCDMA to LTE
UE
NodeB
RNC
eNodeB
1
MME/SGSN
The RNC schedules SIBs and
informs the Node B how to
broadcast them via SIB update
procedure
RRC: SYSTEM INFORMATION
UE measures neighbor LTE layers
2
UE reselects to LTE target cell according to reselection rules
RRC: SYSTEM INFORMATION
RRC: RRC CONNECTION REQUEST
RRC: RRC CONNECTION SETUP
RRC: RRC CONNECTION SETUP COMPLETE
3
NAS: TRACKING AREA UPDATE REQUEST
NAS: TRACKING AREA UPDATE ACCEPT
NAS: TRACKING AREA UPDATE COMPLETE
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1 The NodeB broadcasts System Information containing the measurement rules and
thresholds for LTE layer cells.
2 The UE ranks the cells, evaluates the reselection criteria and eventually reselects to the
target LTE cell. Then it starts to read System Information and performs RRC connection
establishment.
3 The UE performs Tracking Area Update in MME via Non-Access Stratum messages. During
this procedure the MME and SGSN exchanges the UE context.
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Network planning parameters
Newly introduced MOCs
ADJL
• This feature introduces two new parameter Managed Object Classes (MOC): HOPL
• HOPL containing reselection related parameters/thresholds
• ADJL containing non-serving cell related information (for example bandwidth of an LTE layer)
• All these parameters are On-line modifiable.
Existing parameters
• This feature uses existing parameters as well
• Cell reselection triggering timer for IDLE MODE mobility state
• Cell reselection triggering timer for CELL_PCH and URA_PCH mobility states
• These parameters are On-line modifiable. as well.
Detailed parameters’ descriptions, ranges and default values are presented on next slides.
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Network planning parameters - E-UTRA detection
Abbreviated name
EUTRAdetection (RU20 On Top: RNC; RU30: RNFC)
Parameter name
E-UTRA detection
Data type
Enumeration
Description
This parameter defines whether the UE in idle mode may detect the presence of an E-UTRA
cell
Parameter group
SystemInfo
Classification
Telecom
Range and step
Disabled (0), Enabled (1)
Default value
Disabled (0)
On-line modifiable.
.
WCDMA
coverage
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coverage
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With the default value UE is not able to detect the presence of a E-UTRA cell. Thus, cell
reselection to LTE is not possible
It is necessary to set Enabled (1) value for this parameter to switch on the LTE cell reselection
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RAN2067 LTE Interworking
Network planning parameters - LTE Cell Reselection
Abbreviated name
LTECellReselection (WCEL)
Parameter name
LTE Cell Reselection
Data type
Enumeration
Description
The parameter indicates if cell Reselection from WCDMA to LTE for idle and connected mode(Cell_PCH ,URA_PCH)
UE’s is enabled in the cell or not.
Parameter group
SystemInfo
Classification
Telecom
Range and step
Disabled (0), Enabled (1)
Default value
Disabled (0)
CELL
CELL
CELL
CELL
CELL
CELL
With this
parameter it is
possible to
control the cell
reselection
availability on a
cell level
BTS
On-line modifiable.
CELL
CELL
CELL
LTE Cell Reselection capable cell
LTE Cell Reselection non-capable cell
BTS
BTS
RNC
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With this parameter it is possible to control the cell reselection availability on a cell level
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RAN2067 LTE Interworking
Network planning parameters - Priority for SIB19
Abbreviated name
SIB19Priority (RNC)
Parameter name
Priority for SIB19
Data type
Number
Description
This parameter defines the priority of the System Information Block 19, which is used by the scheduling
algorithm in the RNC to give precedence to the SIB.
1 = highest priority
4 = lowest priority
Parameter group
SystemInfo
Classification
Telecom
Range and step
1...4, step 1
Default value
3
On-line modifiable.
It is recommended that Information Block 19
priority has higher priority value than SIB 1, SIB2,
SIB3, SIB5 and SIB7.
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SIB3
SIB4
SIB5
SIB11
…
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• This is used by the scheduling algorithm in the RNC to give precedence to the SIB.
• SIBs with higher priority value will be broadcast earlier in SFN cycle and with large number
of repetitions
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SIB19
Network planning parameters - E-UTRA Absolute Radio Frequency Channel Number
37
Abbreviated name
AdjLEARFCN (ADJL)
Parameter name
E-UTRA Absolute Radio Frequency Channel Number
Data type
Number
Description
This parameter defines the E-UTRA Absolute Radio Frequency Channel Number of the
neighboring E-UTRA frequency. This parameter defines the EARFCN of the downlink carrier
frequency.
Parameter group
HCConfiguration
Classification
Radio Resource Utilization
Range and step
0...65535, step 1
Default value
-
On-line modifiable.
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SIB19
Network planning parameters - Measurement Bandwidth
Abbreviated
name
AdjLMeasBw (ADJL)
Parameter name Measurement Bandwidth
Channel
Bandwidth
Data type
Enumeration
Description
This parameter indicates the measurement bandwidth information common
for all neighboring E-UTRA cells on the carrier frequency.
Parameter
group
SystemInfo
Classification
Telecom
Range and step
6 (6), 15 (15), 25 (25), 50 (50), 75 (75), 100 (100)
Default value
6 (6)
Transmission
Bandwidth
1.4
6
3
15
5
25
10
50
15
75
20
100
[MHz]
[NRB]
On-line modifiable.
The values indicate the number of resource blocks over which the UE could measure
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The values indicate the number of resource blocks over which the UE could measure
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Network planning parameters - Absolute priority level for cell reselection
Abbreviated
name
AbsPrioCellReselec (WCEL)
Parameter
name
Absolute priority level for cell reselection
Data type
Number
Description
This parameter defines the absolute priority level for the serving
cell which is used in the absolute priority based cell-reselection.
Parameter
group
SystemInfo
Classification
Telecom
Range and
step
0...7, step 1
Default value
0
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Priority 7
LTE layer
Priority 5
WCDMA layer 1
Priority 5
WCDMA layer 2
Priority 3
WCDMA layer 3
© Nokia 2019
It must be ensured that AbsPrioCellReselec and AdjLAbsPrioCellReselec always have
unique values.
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Idle Mode Mobility Management from WCDMA
SIB19
RAN2067 LTE Interworking
Network planning parameters - Cell Reselection Absolute Priority
Abbreviated
name
AdjLAbsPrioCellReselec (HOPL)
Parameter
name
Cell Reselection Absolute Priority
Data type
Number
Description
This parameter defines the absolute priority level of the inter-rat
LTE (E-UTRA) neighbor frequency in the absolute priority based
cell Reselection procedure.
Parameter
group
Priority 7
LTE layer
Priority 5
WCDMA layer 1
Priority 5
WCDMA layer 2
Priority 3
WCDMA layer 3
HCConfiguration
The values indicate the number of
resource blocks over which the UE
could measure
Classification Radio Resource Utilization
40
Range and
step
0...7, step 1
Default value
1
On-line modifiable.
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It must be ensured that AbsPrioCellReselec and AdjLAbsPrioCellReselec always have
unique values
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Idle Mode Mobility Management from WCDMA
SIB19
RAN2067 LTE Interworking
Network planning parameters - Cell Reselection Minimum RX level
Abbreviated name
AdjLQrxlevminEUTRA (HOPL)
Parameter name
Cell Reselection Minimum RX level
Data type
Number
Description
This parameter determines the minimum required Reference Signal Received Power (RSRP) level which the
measurement result of the E-UTRA/LTE neighbor cell must exceed before the cell Reselection becomes possible.
Parameter group
HCConfiguration
Classification
Radio Resource Utilization
Range and step
-140...-44 dBm, step 2 dBm
Default value
-140 dBm
On-line modifiable.
• This is the RSRP
• For example
SrxLev related to
E-UTRA cell
level measured for
E-UTRA cell
• This is the minimum
required RSRP level
for E-UTRA cell
SrxlevNonServingCell = AdjLQrxlev_meas – AdjLQrxlevmin
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The default value is the less demanding value.
This value must be aligned with the LTE RAT configurations to avoid ping-pong behavior.
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Idle Mode Mobility Management from WCDMA
SIB19
RAN2067 LTE Interworking
Network planning parameters - Cell Reselection Threshold high
Abbreviated name
AdjLThreshigh (HOPL)
Parameter name
Cell Reselection Threshold high
Data type
Number
Description
This parameter defines the Srxlev based threshold used by the UE for cell reselection towards a higher absolute
priority layer when absolute priorities are applied. A threshold is defined for each absolute priority layer.
Parameter group
HCConfiguration
Classification
Radio Resource Utilization
Range and step
0...62 dB, step 2 dB
Default value
On-line modifiable.
0 dB
The values indicate the number of
resource blocks over which the UE
could measure
SrxlevNonServingCell = AdjLQrxlev_meas – AdjLQrxlevmin
Trigger a reselection to
higher priority layer?
Srxlev
42
Threshold
high
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The default value is the less demanding value. It is possible to perform cell reselection as soon
as the measured RSRP level for E-UTRA cell is equal to the minimum required RSRP level for
E-UTRA cell. This value must be aligned with the LTE RAT configurations to avoid UE pingpong behavior.
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SIB19
RAN2067 LTE Interworking
Network planning parameters - Cell Reselection Threshold low
Abbreviated name
AdjLThreslow (HOPL)
Parameter name
Cell Reselection Threshold low
Data type
Number
Description
This parameter defines the Srxlev based threshold used by the UE for cell reselection towards an equal or
lower absolute priority layer when absolute priorities are applied. A threshold is defined for each absolute priority
layer.
Parameter group
HCConfiguration
Classification
Radio Resource Utilization
Range and step
0...62 dB, step 2 dB
Default value
0 dB
On-line modifiable.
SrxlevNonServingCell = AdjLQrxlev_meas – AdjLQrxlevmin
Trigger a reselection to
lower priority layer?
Threshold
low
Srxlev
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The default value is the less demanding value. It is possible to perform cell reselection as soon
as the measured RSRP level for E-UTRA cell is equal to the minimum required RSRP level for
E-UTRA cell. This value must be aligned with the LTE RAT configurations to avoid UE pingpong behavior.
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SIB3
RAN2067 LTE Interworking
SIB4
Network planning parameters - Thresh serving low
Abbreviated name
Threshservlow (WCEL)
Parameter name
Thresh serving low
Data type
Number
Description
This parameter defines the threshold for Srxlev in the serving cell below which the UE may perform cell reselection
to a cell on a lower absolute priority layer.
Parameter group
SystemInfo
Classification
Telecom
Range and step
0...62 dB, step 2 dB
Default value
0 dB
Srxlev
[dB]
SrxlevServingCell = Qrxlev_meas – Qrxlevmin
Threshservlow
Time [s]
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The lower the threshold, the worse the radio conditions in the serving cell have to become in
order to reselect the UE to a lower priority cell.
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SIB3
RAN2067 LTE Interworking
SIB4
Network planning parameters - S prioritysearch1
Sprioritysearch1 (WCEL)
Parameter name
S prioritysearch1
Data type
Number
Description
This parameter defines the threshold for Srxlev in the serving cell controlling the inter-frequency and inter-RAT
measurements.
If SrxlevServingCell > Sprioritysearch1 and SqualServingCell > Sprioritysearch2 then the UE may not search for,
or measure layers of equal and lower priority.
Parameter group
SystemInfo
Classification
Telecom
Range and step
0...62 dB, step 2 dB
Default value
0 dB
Srxlev [dB]
Abbreviated name
SrxlevServingCell = Qrxlev_meas – Qrxlevmin
Received Signal Code Power at Common
Pilot Channel (CPICH RSCP) level
Sprioritysearch1
From t1 point of time, the UE measures
higher, equal and lower priority cells.
Threshservlow
t1
Time [s]
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SIB3
RAN2067 LTE Interworking
SIB4
Network planning parameters - S prioritysearch2
Sprioritysearch2 (WCEL)
Parameter name
S prioritysearch2
Data type
Number
Description
This parameter defines the threshold for Squal in the serving cell controlling the inter-frequency and inter-RAT
measurements.
If SrxlevServingCell > Sprioritysearch1 and SqualServingCell > Sprioritysearch2 then the UE may not search for, or
measure E-UTRA layers of equal or lower priority.
Parameter group
SystemInfo
Classification
Telecom
Range and step
0…7 dB, step 1 dB
Default value
0 dB
Squal [dB]
Abbreviated name
SqualServingCell = Qqual_meas - Qqualmin
Energy per modulating bit to the noise spectral
density [Ec/No] ratio
Sprioritysearch2
From t1 point of time, the UE measures
higher, equal and lower priority cells.
t1
Time [s]
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SIB3
RAN2067 LTE Interworking
SIB4
Network planning parameters - Cell reselection triggering time (PCH)
Abbreviated name
Treselection, TreselectionPCH (WCEL)
Parameter name
Cell reselection triggering time (PCH)
Data type
Number
Description
The UE triggers the reselection of a new cell if the cell reselection criteria are fulfilled during the Treselection
(PCH) time interval. Different triggers are provided for different UE mobility states:
•Treselection for idle state
•TreselectionPCH for CELL_PCH and URA_PCH states.
Parameter group
SystemInfo
Classification
Telecom
Range and step
0...31 s, step 1 s for Treselection
0...31 s, step 1 s for TreselectionPCH
Default value
2 s; 2 s
On-line modifiable.
On-line modifiable.
SIB3
Treselection
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SIB4
Treselection
TreselectionPCH
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RAN2067 LTE INTERWORKING
Example : UE reselects from WCDMA to LTE
SIB19
3G
3G
Treselection timer
Treselection timer
2 seconds
2 seconds
4G
4G
EUTRA Priority Info List
4G
-115 + 14 (Qrxlevmin + Sprioritysearch1)
3G
3G
3G
3G
3G
4G
3G
3G
3G
3G
3G
EUTRA layer 1
LTE RSRP [dBm]
WCDMA RSCP [dBm]
4G
UTRA Priority Info
Threshservlow 2dB
Sprioritysearch1 14dB
Sprioritysearch2 2dB
AbsPrioCellReselec 3
-115 + 2 (Qrxlevmin + Threshservlow)
AdjLEARFCN 1401
AdjLMeasBw 50
AdjLAbsPrioCellReselec 7
AdjLQrxlevminEUTRA -130dBm
AdjLThreshigh 18dB
AdjLThreslow 4dB
EUTRA layer 2
-130 + 18 (AdjLQrxlevminEUTRA + AdjLThreshigh)
SIB3
SIB4
-130 + 4 (AdjLQrxlevminEUTRA + AdjLThreslow)
Time [s]
WCDMA layer RSCP
LTE layer 1 RSRP (1800MHz)
LTE layer 2 RSRP (2600Mhz)
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AdjLEARFCN 6240
AdjLMeasBw 50
AdjLAbsPrioCellReselec 2
AdjLQrxlevminEUTRA -130dBm
AdjLThreshigh 18dB
AdjLThreslow 4dB
QqualMin -15dB
QrxlevMin -115dBm
Treselection 2s
TreselectionPCH 2s
© Nokia 2019
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Module content
•
•
•
•
49
Cell Reselection Overview
RAN2067 LTE Interworking
RAN3069: RSRQ-based LTE Reselection
Appendix: Hierarchical Cell Structures (HCS)
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RAN3069: RSRQ-based LTE Reselection
Introduction
These features introduce parameter set
that is necessary to perform priority
based reselection to LTE
Based on rules it reselects
back to LTE
UTRAN Connected Mode
Cell_PCH
URA_PCH
Cell_DCH
Cell_FACH
UE listens to broadcast
channel (SIB19)
Establish RRC
Connection
Release RRC
Connection
Idle mode
Benefits:
LTE rollout phase support
In the initial phase, the LTE covearge is limited and UEs easily run out of it. Both TDD and FDD UARFCNs are
supported.
LTE cell reselection
LTE-users who did change RAT to WCDMA due to coverage/service reasons are able to automatically return to LTE.
Thanks to 3GPP Rel-9 enhancements, LTE RSRP and RSRQ criteria are used.
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Brief Description:
This feature supports UE priority based cell reselection from WCDMA to LTE
The operator is able to set priorities for different Radio Access Technologies (RATs)
Priorities are communicated to UE via SIB19 broadcast message
System Information Block number 19 (enabling LTE cell reselection) is introduced by 3GPP
Release 8
3GPP Release 9 introduces quality based reselection
Additional, signal quality related thresholds are supported by RAN3069 RSRQ-based LTE
Reselection
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RAN3069: RSRQ-based LTE Reselection
With and without the feature
RAN2067
Activated
RAN3069
Not activated
• SIB19 message does not contain quality threshold (LTE RSRQ minimum
required level)
RAN2067
Activated
• SIB19 message contains quality threshold (LTE RSRQ minimum required
level)
• UE performs reselection based on RSRP criterion
• It may happen that the UE is not able to camp on LTE Cell due to low
quality of the LTE signal (too low RSRQ)
• UE performs reselection based on RSRQ criterion
• UE does not try to camp on LTE cell if quality thresholds are not met (even if
signal level threshold is good enough - RSRP)
• Service interruption is observed
• No service interruption is possible
Reselection failure : It is possible that the UE could
not camp on an LTE cell due to signal quality level
UE reselect to LTE cell only if signal quality threshold
is exceeded
UE checked RSRQ
before reselection
decision was made – UE
can access the cell
RSRP criterion is fulfilled.
However, minimum RSRQ
requirement is not met –
UE cannot access the cell
WCDMA Cell
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RAN3069
Activated
LTE Cell
WCDMA Cell
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RAN3069: RSRQ-based LTE Reselection
Interdependencies
RAN2067
LTE Interworking
Flexi System Module Rel-1,
Rel-2, Rel-3
This feature introduces 3GPP Rel-9 extension – quality thresholds
REQUIRES RAN2067 LTE INTERWORKING
Feature allows seamless RAT change form LTE to WCDMA
Feature allows seamless VoIP -> CS Handovers and CS FBs to
WCDMA
This is E-UTRAN counterpart for RAN2067 LTE Interworking
Mandatory
52
Interworking
RAN3069
RSRQ-based LTE Reselection
LTE1036
RSRQ-based Cell Reselection
This is E-UTRAN counterpart for
RAN3069 RSRQ-based LTE
Reselection
RAN2176
LTE PS Handover
RAN2435
SRVCC from LTE and CSFB
with HO
LTE762
Idle Mode Mobility from LTE to
WCDMA, GSM or other LTE
Bands
Optional
RA47030-V-19A
Recommended
© Nokia 2019
Feature Interdependencies:
• RAN3069 RSRQ-based LTE Reselection requires one of the following HW elements:
• Flexi System Module Rel-1
• Flexi System Module Rel-2
• Flexi System Module Rel-3
• RAN3069 RSRQ-based LTE Reselection requires RAN2067 LTE Interworking
• RAN3069 RSRQ-based LTE Reselection is an extension suporting 3GPP Rel-9 quality thresholds for LTE cell reselection.
• The quality thresholds include the UTRA serving cell Ec/N0 threshold and E-UTRA neighbor cell RSRQ quality thresholds.
• There is no separate license for RAN3069 RSRQ-based LTE Reselection (this feature is controlled by RAN2067 LTE
Interworking feature)
E-UTRAN counterparts:
• LTE762 Idle Mode Mobility from LTE to WCDMA, GSM or other LTE Bands is E-UTRAN counterpart for RAN2067 LTE Interworking
• It allows idle mode mobility from LTE towards WCDMA – UE performs measurement and reselection decision based on RSRP
and RSCP
• LTE1036 RSRQ-based Cell Reselection is E-UTRAN counterpart for RAN3069 RSRQ-based LTE Reselection
• This feature introduces 3GPP Rel-9 extension to idle mode mobility between LTE and WCDMA – quality thresholds.
• UE performs measurement and reselection decision based on RSRQ and Ec/No
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RAN3069: RSRQ-based LTE Reselection
Interdependencies
• The following allow to put LTE frequencies for cell reselection (signalled via SIB19) in priority order:
- HOPL- AdjLAbsPrioCellReselec and
- ADJL-ADJLId (used if two EARFCNs have equal HOPL- AdjLAbsPrioCellReselec parameter value)
Iphone5 reads only first 5 LTE frequencies in SIB19
(the operator can configure up to 8 LTE layers)
SIB19
IPhone 5
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Feature impact:
With RAN2067 LTE Interworking or RAN3069 RSRQ-based LTE Reselection, the operator
does not have the possibility to control the order in which EARFCNs are provided on E-UTRA
frequency and priority info list.
Especially when modifications to existing lists is carried out (for example addition or deletion of
ADJL object, or RNC restart)
It is known that different UEs have different implementation with regard to the reading
order of this information
IPhone 5 reads only first 5 LTE frequencies in SIB19 (the operator can configure up to 8
LTE layers)
Being Iphone5 the popular LTE phone in customers’ networks, controlling of the list
order brings tangible benefits in terms of performance of the WCDMA->LTE mobility
procedure
This is directly translating in faster availability of LTE network to the end-users
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Idle Mode Mobility Management from WCDMA
RAN3069: RSRQ-based LTE Reselection
General requirements (3GPP R8 & R9 are needed)
Both features are introduced to follow
3GPP specifications in terms of idle mode
mobility between WCDMA and LTE.
UE Vendor
System Information Block
number 19 (enabling LTE cell
reselection) is introduced by
3GPP Rel-8. Thus, LTE2067
LTE Interworking feature
requires:
3GPP Rel-8
Release-9
capable UE
Release-9
capable RNC
AND
Quality extensions in System
Information Block number 19
are introduced by 3GPP Rel9. Thus, LTE3069 RSRQbased LTE Reselection
feature requires:
LTE Reselection
54
Release-8
capable UE
Release-8
capable RNC
AND
• Rel-8 specifies the basic concept of cell
reselection based on absolute priorities of
WCDMA and LTE layers. UE performs the
reselection decision based on
measurement results (RSRP and RSCP
results are taken into account)
• Rel-9 specifies the extension to absolute
priority based cell reselection. Starting
from now, UE uses quality thresholds
during reselection decision.
3GPP Rel-9
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Idle Mode Mobility Management from WCDMA
RAN3069: RSRQ-based LTE Reselection
How does it work?
1
•
•
•
•
•
3
SIB19 defines available E-UTRA frequencies characterized by:
E-UTRA Absolute Radio Frequency Channel Number (EARFCN)
Measurement bandwidth
LTE layer priority
Threshold parameters that are used by the UE to define LTE layer
measurement rules
• Threshold parameters to decide on reselection criteria – both WCDMA
layer related and LTE layer related parameters are delivered
SIB19
• The Broadcast Channel BCH transports the information of
Threshservlow 2dB
Sprioritysearch1 14dB
Sprioritysearch2 2dB
AbsPrioCellReselec 3
logical Broadcast Control Channel
• This is then carried in the Primary Common Control
Physical Channel (PCCPCH). All UEs are able to decode
the information on this channel
• Once decoded, the BCCH provides the UE with the
EUTRA Priority Info List
• 3GPP defines 19 different SIBs
• Each SIB groups together system information elements of
the same nature
QqualMin -15dB
QrxlevMin -115dBm
Treselection 2s
TreselectionPCH 2s
EUTRA layer 1
specification
• This feature uses Absolute Priority
Based Reselection specified in TS
25.304 „User Equipment (UE)
procedures in idle mode and procedures
for cell reselection in connected mode”
broadcast channel UE performs
reselection from WCDMA towards LTE
• If a UE is Rel-9, it takes into account
AdjLEARFCN 6240
AdjLMeasBw 50
AdjLAbsPrioCellReselec 2
AdjLQrxlevminEUTRA -130dBm
AdjLThreshigh 18dB
AdjLThreslow 4dB
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• UE behaves according to 3GPP
• Based on delivered parameters via
EUTRA layer 2
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2
SIB4
AdjLEARFCN 1401
AdjLMeasBw 50
AdjLAbsPrioCellReselec 7
AdjLQrxlevminEUTRA -130dBm
AdjLThreshigh 18dB
AdjLThreslow 4dB
necessary general parameters for both system and cell
level to enable it to communicate with the network
55
SIB3
UTRA Priority Info
quality thresholds (WCDMA Ec/No and
LTE RSRQ)
© Nokia 2019
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Idle Mode Mobility Management from WCDMA
RAN3069: RSRQ-based LTE Reselection
RAN2067
Activated
LTE Reselection rules Towards higher priority layer
RAN3069
Activated
• The reselection is triggered if Reference Signal Received Quality (RSRQ) level of LTE candidate cell is above
the threshold related to higher priority layer over the defined time period.
LTE good
Measured RSRQ – Minimum RSRQ >
RSRQ_Threshold1
during the
Treselection time
period
where: Minimum RSRQ = HOPL-AdjLQqualminEUTRA (default: -35dBm [not broadcast])
RSRQ_Threshold1 = HOPL-AdjLThreshigh2 (default: 32 dB [not broadcast])
56
Priority 7
LTE layer 1
Priority 5
WCDMA layer
Priority 4
LTE layer 2
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Idle Mode Mobility Management from WCDMA
RAN3069: RSRQ-based LTE Reselection
RAN2067
Activated
LTE Reselection rules Towards lower priority layer
RAN3069
Activated
• The reselection is triggered if Reference Signal Received Quality (RSRQ) level of LTE candidate cell is above
the threshold related to lower priority layer AND signal level or signal quality of current serving cell falls below
threshold (both events occure simultaneously over the defined time period).
Measured RSCP – Minimum RSCP <= RSCP_Threshold2
3G bad
OR
Measured Ec/No – Minimum Ec/No <= Ec/No_Threshold2
AND
LTE good
during the
Treselection time
period
Measured RSRQ – Minimum RSRQ > RSRQ_Threshold2
where: Minimum RSCP = WCEL-QrxlevMin (default -115dBm)
RSCP_Threshold2 = WCEL- Threshservlow (default 2dB)
Minimum Ec/No = WCEL-QqualMin (default -18dB)
Ec/No_Threshold2 = WCEL- Threshservlow2 (default 0dB [not broadcast])
Minimum RSRQ = HOPL-AdjLQqualminEUTRA (default: -35dBm [not broadcast])
RSRQ_Threshold2 = HOPL-AdjLThreslow2 (default: 32dB [not broadcast])
57
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• WCEL-Treselection is a parameter defining the time period for which the cell reselection criteria need to be
fulfilled to trigger the reselection of a new cell
• Depend on current mobility state UE uses WCEL-Treselection or WCEL-TreselectionPCH timer. These
parameters are broadcast via SIB3, SIB4 messages
• The additional restriction is that the UE cannot reselect to any cell if it is camped to the current serving cell less
then 1 second
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RAN3069: RSRQ-based LTE Reselection
Configuration Management - Parameters
RNC
Introduced by RAN3069
Introduced by RAN2067
Already existing
SIB19Priority
WBTS
WCEL
HOPL (up to 10)
HopLId
AdjLAbsPrioCellReselec
AdjLQrxlevminEUTRA
AdjLThreshigh
AdjLThreslow
AdjLQqualminEUTRA
AdjLThreslow2
AdjLThreshigh2
58
AbsPrioCellReselec
LTECellReselection
Sprioritysearch1
Sprioritysearch2
Threshservlow
Threshservlow2
Treselection
TreselectionPCH
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ADJL (up to 8)
AdjLId
HopLIdentifier
AdjLEARFCN
AdjLMeasBw
© Nokia 2019
Parameters introduced by RAN2067 LTE Interworking:
RNC-SIB19Priority
WCEL-AbsPrioCellReselec
WCEL-LTECellReselection
WCEL-Sprioritysearch1
WCEL-Sprioritysearch2
WCEL-Threshservlow
HOPL-AdjLAbsPrioCellReselec
HOPL-AdjLQrxlevminEUTRA
HOPL-AdjLThreshigh
HOPL-AdjLThreslow
ADJL-AdjLEARFCN
ADJL-AdjLMeasBw
Parameters introduced by RAN3069 RSRQ-based
LTE Reselection:
WCEL-Threshservlow2
HOPL-AdjLQqualminEUTRA
HOPL- AdjLThreslow2
HOPL- AdjLThreshigh2
Already existing parameters:
WCEL-Treselection
WCEL-TreselectionPCH
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Idle Mode Mobility Management from WCDMA
Example of RSRQ-based LTE Reselection
▪ It is necessary to align reselection triggers in both RANs (3G & LTE)
▪ In E-UTRAN, RSRQ based cell reselection is controlled by LTE1036 RSRQ-based Cell Reselection (RL50/RL35TD/RL50FZ)
Measurements:
RSRQ < qQualMinR9 +
sNonIntraSearchQR9
= -19dB + 4dB = -15dB
LTE priority = 7
Measurements:
Always
Reselection:
RSRQ < qQualMinR9 + threshServingLowQR9 = -19dB
+ 2dB = -17dB
AND
Ec/No > qQualMinUtra+ utraFrqQThrLowR9
= -18dB + 4dB = -14dB
Reselection:
RSRQ > AdjLQqualminEUTRA + AdjLThreshigh2
= -19dB + 4dB = -15dB
3G parameters
LTE parameters
WCDMA priority = 6
Measurements:
Ec/No <= qQualMin + Sprioritysearch2
= -18dB + 4dB = -14dB
Measurements:
Always
Reselection:
Ec/No <= qQualMin + Threshservlow2
= -18dB + 1dB = -17dB
AND
RSRQ > AdjLQqualminEUTRA + AdjLThreslow2
= -19dB + 4dB = -15dB
Reselection:
Ec/No > qQualMinUtra +
utraFrqQThrHighR9
= -18dB + 4dB = -14dB
LTE priority = 5
59
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Idle Mode Mobility Management from WCDMA
Configuration Management – User Scenario
SIB19
Treselection timer
RAN3069
2 seconds
Treselection timer
RAN2067
2 seconds
3G
-115 + 14 (Qrxlevmin + Sprioritysearch1)
3G
3G
3G
3G
3G
3G
3G
3G
3G
3G
EUTRA Priority Info List
EUTRA layer 1
4G
4G
-115 + 2 (Qrxlevmin + Threshservlow)
AdjLEARFCN 1401
AdjLMeasBw 50
AdjLAbsPrioCellReselec 7
AdjLQrxlevminEUTRA -130dBm
AdjLQqualMinEUTRA -18dB
AdjLThreshigh 18dB
AdjLThreslow 4dB
AdjLThreshigh2 4dB
AdjLThreslow2 4dB
4G
3G
LTE RSRQ [dB]
WCDMA RSCP or LTE RSRP [dBm]
UE reselects from WCDMA to LTE based on LTE signal quality
3G
-18 + 4 (AdjLQqualminEUTRA + AdjLThreshigh2)
-130 + 18 (AdjLQrxlevminEUTRA + AdjLThreshigh)
EUTRA layer 2
-130 + 4 (AdjLQrxlevminEUTRA +
AdjLThreslow)
SIB3
WCDMA layer RSCP
LTE layer 1 RSRP (1800MHz)
LTE layer 1 RSRQ (1800MHz)
Time [s]
SIB4
QqualMin -15dB
QrxlevMin -115dBm
Treselection 2s
TreselectionPCH 2s
60
UTRA Priority Info
Threshservlow 2dB
Threshservlow2 1dB
Sprioritysearch1 14dB
Sprioritysearch2 2dB
AbsPrioCellReselec 3
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AdjLEARFCN 6240
AdjLMeasBw 50
AdjLAbsPrioCellReselec 2
AdjLQrxlevminEUTRA -130dBm
AdjLQqualMinEUTRA -18dB
AdjLThreshigh 18dB
AdjLThreslow 4dB
AdjLThreshigh2 4dB
AdjLThreslow2 4dB
© Nokia 2019
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Idle Mode Mobility Management from WCDMA
Module content
•
•
•
•
•
61
Cell Reselection Overview
WCDMA and GSM Layer Priorities
RAN2067 LTE Interworking
RAN3069: RSRQ-based LTE Reselection
Appendix: Hierarchical Cell Structures (HCS)
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Idle Mode Mobility Management from WCDMA
Hierarchical Cell Structures (HCS)
3G: Hierarchical Cell Structures HCS:
• Typical:
- smallest cell ➔ highest HCS priority
- different layer ➔ different frequency
Priority
3
3
2
1
3
3
2
3
3
2
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The radio access network may be designed using hierarchical cell structures.
Numbers in the picture describe different layers in the hierarchy.
The highest hierarchical layer, i.e. typically smallest cell size, has the higher priority (number 3 in the figure).
The HCS priority of each cell is given in system information
Normally, different layers are created using different frequencies.
However, in some scenarios, different layers can use the same frequency.
Different frequencies can also be used on the same hierarchical layer e.g.
in order to cope with high load in the system.
In order to cope with UEs travelling fast through smaller cells (e.g. through micro or pico cells), the cell reselection procedure can be
performed towards bigger cells on lower priority layers e.g. to macro cells so as to avoid unnecessary cell reselections.
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Idle Mode Mobility Management from WCDMA
Hierarchical Cell Structures (HCS)
• Cell Reselection in the RRC Idle and RRC Connected Mode:
HCS in use:
for fast
moving UEs
cells with
lower HCS
priority than
in serving cell
R-Criterion
cell ranking
63
HCS not in use:
measurement
thresholds
measurement
thresholds
S-Criterion
fulfilled
S-Criterion
fulfilled
H-Criterion
for slow
moving UEs
if no cell
with H>0
accept all
neighbors
cells with
highest HCS
Priorities &
H>0
R-Criterion
cell ranking
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R-Criterion
cell ranking
© Nokia 2019
HCS introduces an additional cell (re-)selection criterion.
In order to cope with UEs travelling fast through smaller cells (e.g. through micro or pico cells),
the cell reselection procedure can be performed towards bigger cells on lower priority layers
e.g. to macro cells so as to avoid unnecessary cell reselections.
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Idle Mode Mobility Management from WCDMA
Cell reselection with HCS
UseOfHCS
• Cell reselection with HCS
WCEL;
0: HCS not used;
1: HCS in use
SIB 11/12
neighbor list
from BCCH
Measurement criteria
with HCS
Measured
neighbors
S – criteria
HCS_PRIO
WCEL;
Suitable
neighbors
0 (lowest)..
7(highest); step: 1
SIB 3/4
H – criteria
neighbors
to rank
Prioritized
neighbors
R – criteria
Best ranked cell
Reselection if not serving cell
64
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Normal Reselection process (without HCS) follows procedure.
Measurement criteria without HCS:
•S-criteria
•H-criteria
•R-criteria
HCS specific H-criteria defines whether priorities are applied in Reselection
If coverage is bad, all neighbors will be measured, disregarding HCS priority, see flow chart
slides following
In high mobility state, the UE measures on all neighboring cells, which have equal or lower
HCS priority than the serving cell, details to follow
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Cell reselection with HCS
• HCS measurements: Slow FDD intra-RAT
Start
SrxlevS<SsearchHCS?
( RSCP<-115dBm b.d.)
yes
no
Squal<Sintersearch?
( EcNo<-10dB b.d.)
yes
Measure all neighbors
no
Squal>Sintrasearch?
( EcNo>-8dB b.d.)
yes
Measure only higher
HCS neighbors
no
Measure only higher
&equal HCS neighbors
End
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•
The UE gains from the BCCH system information, that HCS is used. Then the UE knows that it has to perform the following threshold
based measurements rules (replace Sx by Squal for FDD cells and by Srxlev for TDD cells):
•
intra-frequency & inter-frequency threshold based measurement rule :
“IF (Srxlevs  SsearchHCS) OR (if FDD AND Sx  Sintersearch)
THEN measure on all intra-frequency & inter-frequency cells
ELSE
IF (Sx > Sintrasearch)
THEN measure on all intra-frequency & inter-frequency cells, which have higher HCS priority level than the serving
cell unless measurement rules for fast-moving UEs are triggered ELSE measure on all intra-frequency and inter-frequency cells, which
have equal or higher HCS priority level than the serving cell unless measurement rules for fast-moving UEs are triggered ENDIF “ (cited
from TS25.304 V3.11.0, chap 5.2.6.1.2)
•
If HCS is used and if Sintrasearch or SsearchHCS or Sintersearch (in FDD) are not sent for the serving cell, UE performs measurements on all
intra-frequency and inter-frequency cells. SsearchHCS can get integer values ranging from -1 to 91 (step size 2) in the FDD mode.
Negative values are set to 0 by the UE.
b. d. means “by default”
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Cell reselection with HCS
• HCS Measurement Rules for Intra-RAT, slow UE
BCCH SI: HCS used
if Srxlevs
> SsearchHCS
(i.e. RSCP > - 115 dBm)
-10 dB
EC/N0 =
Sintersearch
Sintrasearch
-8 dB
search
search ALL
Intra- &
Inter- Frequency
if Srxlevs ≤ SsearchHCS OR Squal ≤ Sintersearch
if Srxlevs
≤ SsearchHCS
Equal &
higher HCS
priority
Intra- & InterFrequency
*
WCEL; -1..91; def.: -1 dB
SIB3
search ALL
Intra- & Inter-frequency cells
*negative values are set to 0 by UE
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Srxlev =
Qrxlevmeas –
Qrxlevmin
Qrxlevmin:
WCEL; -119...-25;
2; -115 dBm
SIB 11/12
Squal =
CPICH Ec/No
- QqualMin
SsearchHCS
(i.e. RSCP < - 115 dBm):
66
search
higher HCS
priority
Intra- &
Inter- Frequency
Example: NSN
Sintrasearch = 10 dB,
Sintersearch = 8 dB,
Ssearch_RAT = 4 dB,
SsearchHCS = -1 dB
QqualMin:
WCEL; -24...0;
1; -18 dB
SIB 11/12
© Nokia 2019
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Idle Mode Mobility Management from WCDMA
Cell reselection with HCS
• HCS measurements: Slow FDD inter-RAT
Start
SrxlevS<SHCS,RATm?
( RSCP<-115dBm b.d.)
yes
no
Squal<SsearchRATm?
( EcNo<-14dB b.d.)
yes
Measure all RATm
neighbors
no
Squal>SlimitSearchRAT?
( EcNo>-16dB b.d.)
yes
Don‘t measure InterRAT
no
Measure higher &equal
HCS Inter-RATneighbors
b.d. this will never
happen!
End
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•
If HCS is used in the serving cell, what kind of inter-RAT measurements are conducted?
(replace Sx by Squal for FDD cells and bySrxlev for TDD cells):
•
Inter-RAT threshold-based measurement rules:
“IF (Srxlevs <= SHCS,RATm) or (if FDD and Squal <= SSearchRATm)
THEN UE shall measure on all inter-RAT “m“ cells
ELSE
IF (Sx > Slimit,SearchRATm)
THEN UE need not measure neighboring cells in RAT “m”
ELSE
UE shall measure on all neighboring cells in RAT “m”, which have equal or higher HCS
priority level than the serving cell unless measurement rules for fast-moving UEs are triggered
ENDIF “
(cited from TS25.304 V3.11.0, chap 5.2.6.1.2)
•
If HCS is used and if SHCS,RATm is not sent for the serving cell, UE performs measurements on all Inter-RATm cells.
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Cell reselection with HCS
• Default HCS Measurement Rules, Inter-RAT, slow UE
if Srxlevs > SHCS,RATm
(i.e. RSCP > - 115 dBm)
Sintersearch
SsearchRAT m
EC/N0 =
Sintrasearch
HCS;
Inter-RAT measurements?
-14dB
Srxlev =
Qrxlevmeas –
Qrxlevmin
search
search ALL
Intra- &
InterFrequency
+
Inter-RAT
search all
Intra- &
InterFrequency
search
Equal &
higher HCS
priority
Intra- &
InterFrequency
higher HCS
priority
Intra- &
InterFrequency
if Srxlevs ≤ SHCS_RATm
Slimit_SearchRAT#
(i.e. RSCP > - 115 dBm):
SIB3
WCEL; 0..20; 2; 2 dB
search ALL Inter-RAT cells
SHCS_RAT
-1..91; 2; -1 dB*
SIB3
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WCEL; -119...-25;
2; -115 dBm
SIB 11/12
Squal =
CPICH Ec/No
- QqualMin
QqualMin:
WCEL; -24...0;
1; -18 dB
SIB 11/12
Example: Nokia
Sintrasearch = 10 dB,
Sintersearch = 8 dB,
Ssearch_RAT:
WCEL; 0...20; 2; 4 dB
* negative values are set to 0 by UE
# Threshold for skipping inter-RAT measurement rules in HCS
Qrxlevmin:
Ssearch_RAT = 4 dB,
Slimit, searchRAT = 2 dB,
SsearchHCS = -1dB,
SHCS_RAT = -1dB
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Idle Mode Mobility Management from WCDMA
Cell reselection with HCS
• Non-default HCS Measurement Rules for Inter-RAT
HCS;
Inter-RAT measurements?
Let Slimit_searchRAT m=6dB
SsearchRAT m
EC/N0 =
-14 dB
Sintrasearch
Sintersearch
Slimit_searchRAT m
-13 dB
search
search ALL
Intra- &
InterFrequency
+
Inter-RAT
search
Intra- &
Inter-frequency
&
Equal & higher
HCS priority
Inter- RAT
search all
Intra- &
InterFrequency
Slimit_SearchRAT
if Srxlevs ≤ SHCS_RATm
WCEL; 0..20; 2; 2 dB
SIB3
(i.e. RSCP > - 115 dBm):
Ssearch_RAT:
search ALL Inter-RAT cells
WCEL; 0...20; 2; 4 dB
SHCS_RAT
• negative values are set to 0 by UE
• Threshold for skipping inter-RAT
measurement rules in HCS
69
Equal &
higher
HCS
priority
Intra- &
InterFrequency
-1..91; 2; -1 dB*
SIB3
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search
higher
HCS
priority
Intra- &
InterFrequency
Example: Nokia
Sintrasearch = 10 dB,
Sintersearch = 8 dB,
Ssearch_RAT = 4 dB,
Slimit, searchRAT = 2 dB,
SsearchHCS = -1dB,
SHCS_RAT = -1dB
Srxlev =
Qrxlevmeas –
Qrxlevmin
Qrxlevmin:
WCEL; -119...-25;
2; -115 dBm
SIB 11/12
Squal =
CPICH Ec/No
- QqualMin
QqualMin:
WCEL; -24...0;
1; -18 dB
SIB 11/12
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Idle Mode Mobility Management from WCDMA
Cell reselection with HCS
• Measurement Rules: HCS & fast moving UEs
NCr: WCEL; 1..16; 1; 8; SIB3
TCrmax: WCEL; not used, 30, 60, 120, 180, 240 s; 60s; SIB3
TCrmaxhyst: WCEL; not used; 10..70; 10; SIB3
NCR/TCRmax
time
measurement rules for
slow moving UEs
fast moving UE
TCrmaxHyst
measurement rules for
slow moving UEs
measurement rule for fast moving UEs
NCR = cell reselections threshold
TCRmax = duration for evaluating the # of cell reselections
TCrmaxhyst: Cell reselection hysteresis for reverting
from UE high-mobility measurements
measures
neighboring cells
with equal or lower
HCS priority
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prioritizes cells with
lower HCS priority
for Reselection
© Nokia 2019
HCS is introduced so that slow moving UEs are served in cells with high priority, which often have a small radius (micro or pico cells). On the
other hand, fast moving UEs should remain on cells with low priority, which often have a large cell radius (macro cells). By doing so, too
many Reselection shall be avoided. For fast moving UEs, following intra-frequency, inter-frequency & inter-RAT measurement rules apply:
•NCR is a threshold value for the number of cell Reselections.
•TCRmax is a time period.
If there are more than NCR cell reselections during TCRmax, then high-mobility has been detected (UE).
•
In this state, the UE measures on all neighboring cells, which have equal or lower HCS priority than the serving cell.
Candidate cells for Reselections fulfill the S-criterion. If there are several candidates for cell Reselection, the UE
prioritizes Reselection neighboring cells on lower HCS priority level before neighboring cells on the same HCS priority
level.
What happens, if the number of cell Reselections no longer exceeds NCR during the time period TCRmax?
•
Then, for the time period TCrmaxHyst, the high speed cell Reselection rule is applied.
•
Afterwards, the UE must apply the normal (low speed) threshold based measurement rules for HCS.
According to the specifications, following parameter values are possible:
•
TCRmax: Enumerated (not used, 30, 60, 120, 180, 240), in seconds. Default value is set to ’60s’.
•
NCR : is an integer value ranging from 1 to 16. Default value is 8.
•
TCrmaxHyst : Enumerated (not used, 10,20, 30, 40,50, 60, 70), in seconds. Default: not used.
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Cell reselection with HCS
Cell Reselection: H-Criterion (slow moving UE)
• HCS is in use. Which cells are potential candidates for cell re-selection?
• Here, we use the quality level threshold criterion H.
• It is applied for all neighboring cells, i.e. Intra-frequency cells, Inter-frequency cells & Inter-RAT cells. H values are
defined for the serving & neighboring cells:
•
•
Hs = Qmeas,s – Qhcss
Hn = Qmeas,n - Qhcsn – TOn * Ln
(for the serving cell)
(for candidate neighboring cells for cell re-selection)
• Qmeas is the quality of the Rx signal at the UE.
•
•
•
For FDD cells, this value is calculated from the averaged CPICH Ec/No or CPICH RSCP.
For TDD cells, it results from the averaged P-CCPCH RSCP.
For GSM cells, the UE determines it from the averaged received signal level.
• There are two measurement options for FDD cells. The UE derives the measurement quality (Ec/No or RSCP)
from UTRAN.
• A cell fulfils the quality level threshold criterion H, if its H-value is equal or larger then zero.
• The value Qhcs is used to determine the UE “distance“ from the Node B before the cell becomes a candidate for
cell re-selection; its value depends on the measurement method. The specification default value is 0.
TOn = TEMP_OFFSET n * W(PENALTY_TIMEn – Tn)
•
-
Ln =
0 if HCS_PRIOn = HCS_PRIOs
1 if HCS_PRIOn <> HCS_PRIOs
71
W(x) =
0 for x < 0
1 for x >= 0
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•
TEMP_OFFSETn introduces an additional offset to the H (and R) criterion, but only for a certain period of time, which is specified by the
parameter PENALTY_TIMEn.
•
This timer is set for each neighboring cell.
•
A timer is started from value zero, when one of the following conditions is fulfilled:
• If HCS_PRIOn <> HCS_PRIOs and Qmeas,n > Qhcsn
• If HCS_ PRIOn = HCS_PRIOs and
i)
for serving FDD and neighbor FDD cells if the quality measure for cell selection and
CPICH Ec/No in the serving cell, and:
reselection is set to
Qmeas,n > Qmeas,s + Qoffset2s,n
ii)
for serving FDD and neighbor FDD cells if the quality measure for cell selection and
CPICH RSCP in the serving cell, and for all other serving and neighbor cells:
reselection is set to
Qmeas,n > Qmeas,s + Qoffset1s,n“ (from TS25.304 V3.11.0, chap 5.2.6.1.4)
•
The timer Tn is only in use, when one of the above conditions is fulfilled.
•
If a cell-reselection takes place, and the cell, for which this timer was triggered is still a neighboring cell, and the above conditions are
fulfilled with the threshold values of the new cell, then the timer continues to run. Otherwise, it‘s use is stopped. If no condition is fulfilled,
the value TOn is set to zero.
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Cell reselection with HCS
HCS_PRIO*
Cell Reselection: H-Criterion (slow moving UE)
0 (lowest)..
7(highest); step: 1
SIB 11/12
• According to the specifications, following parameter values are possible:
•
HCS_PRIO gives a cells priority.
•
TEMP_OFFSET value depends on the measurement method.
•
•
If in the FDD mode, CPICH Ec/No is used, then its value are 3, 6, 9, 12, 15, 18, 21, or infinitive; Otherwise, its values
are 2, 3, 4, 6, 8, 10, 12, or infinitive.
PENALTY_TIMEn is an integer value of either 0, 10, 20, 30, 40, 50, or 60 seconds.
•
The default value is 0.
• The H-selection criterion:
•
The UE has determined all neighboring cells, which fulfil the S-criterion.
•
Then, it determines all cells of the highest HCS_PRIO, which fulfil the quality level threshold criterion
•
Only these cells are ranked by the UE.
•
If no cell fulfils the quality level threshold criterion H >=0, then all cells will be ranked by the UE, independent of their HCS
priority level. This rule also applies, when no HCS is in use.
H  0.
•
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Cell reselection with HCS
• Cell Reselection: H-Criterion (slow moving UE)
measurement
thresholds
HCS is in use:
Candidates
for cell Reselection?
H-Criterion !
TOn: temporary Offset
during Penalty Time
→ next slide
Qhcs:
Quality threshold
level for HCS
WCEL; -24..0;
0.5; -24 dB
Hs = Qmeas,s – Qhcss
S-Criterion
fulfilled
Hn = Qmeas,n - Qhcsn – TOn * Ln
Ln = 0, if HCS_Prion = HCS_Prios
= 1, if HCS_Prion ≠ HCS_Prios
H-Criterion
for fast
moving UEs
cells with
lower HCS
priority than
in serving cell
73
cells with
H>0
only cells
with
highest HCS
priorities &
H>0
for slow
moving UEs
no cells with
H>0
accept all
neighbors
(same as HCS
not in use)
R-Criterion
R-Criterion
R-Criterion
cell ranking
cell ranking
cell ranking
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Cell reselection with HCS
• Cell Reselection: H-Criterion (slow moving UE) & TOn
Adjs,i,gPenalty_Time:
HOPx; 0..60; 10; 0 s
Adjg,i,sTempOffset;
HOPx; 3, 6, 9, 12, 15, 18,
21, Infinity; 3 dB;
temp. offset during
Penalty Time used when
neighbor has different
priority than serving cell
Hs = Qmeas,s – Qhcss
Ln = 0, if HCS_Prion = HCS_Prios
= 1, if HCS_Prion ≠ HCS_Prios
Hn = Qmeas,n - Qhcsn – TOn * Ln
TOn = TEMP_OFFSET * W(PENALTY_TIMEn – Tn)
n
Qmeas,n - Qhcsn
PENALTY_TIMEn
PENALTY_TIMEn
TOn
TOn
0
H-Criterion:
H>0
TOn = 0
TOn = 0
Start Stop
Start
Tn T n
Tn
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•
•
•
•
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time
Example:
HCS_PRIOn ≠
HCS_PRIOs
 Ln = 1
© Nokia 2019
TEMP_OFFSETn introduces an additional offset to the H (and R) criterion, but only for a certain period of time, which is specified by the
parameter PENALTY_TIMEn.
This timer is set for each neighboring cell.
A timer is started from value zero, when one of the following conditions is fulfilled:
•
if HCS_PRIOn <> HCS_PRIOs and Qmeas,n > Qhcsn
According to the specifications, following parameter values are possible:
•
HCS_PRIO gives a cell’s priority.
•
TEMP_OFFSET value depends on the measurement method.
•
If in the FDD mode, CPICH Ec/No is used, then its value are 3, 6, 9, 12, 15, 18, 21, or infinitive; Otherwise, its
values are 2, 3, 4, 6, 8, 10, 12, or infinitive.
•
PENALTY_TIMEn is an integer value of either 0, 10, 20, 30, 40, 50, or 60 seconds.
•
The default value is 0.
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Cell reselection with HCS
Cell Reselection: H-Criterion (slow moving UE) & TOn
The H-selection criterion:
• The UE has determined all neighboring cells, which fulfill the S-criterion.
• Then, it determines all cells of the highest HCS_PRIO, which fulfill the quality level threshold criterion
H  0.
• Only these cells are ranked by the UE.
• If no cell fulfils the quality level threshold criterion H >=0, then all cells will be ranked by the UE,
independent of their HCS priority level. This rule also applies, when no HCS is in use.
• if HCS_ PRIOn = HCS_PRIOs and
• i) for serving FDD and neighbor FDD cells if the quality measure for cell selection and reselection is set to CPICH
Ec/No in the serving cell, and:
Qmeas,n > Qmeas,s + Qoffset2s,n
• ii) for serving FDD and neighbor FDD cells if the quality measure for cell selection and reselection is set to CPICH
RSCP in the serving cell, and for all other serving and neighbor cells
Qmeas,n > Qmeas,s + Qoffset1s,n
(from TS25.304 V3.11.0, chap 5.2.6.1.4)
• The timer Tn is only in use, when one of the above conditions is fulfilled.
• If a cell-reselection takes place, and the cell, for which this timer was triggered is still a neighboring cell, and the above
conditions are fulfilled with the threshold values of the new cell, then the timer continues to run. Otherwise, it‘s use is stopped.
If no condition is fulfilled, the value TOn is set to zero.
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Cell reselection with HCS
Cell Reselection with HCS: R-Criterion
• After checking the measurement thresholds, the UE has detected suitable cells to camp on.
• If HCS is in use, it has reduced the candidate cells for cell reselection to those with highest priority and H >= 0 (given a slow moving
UE).
• But which of the remaining candidate cells is the best one for cell Reselection?
• For that, a cell-ranking criterion R was specified:
•
Rs = Qmeas,s + Qhysts
•
Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls) (for candidate neighboring cells for cell reselection)
(for the serving cell)
• The serving cell and the remaining candidate cells are ranked according to criterion R.
• The cell ranked with the highest value R is the best cell for the UE to camp on.
• Qhysts gives a hysteresis value to make the serving cell more attractive and thus delay the cell Reselection. It exists in two versions:
•
If the quality measure is based on CPICH Ec/No, Qhyst2 s is used in (FDD cell only); otherwise the hysteresis value Qhyst1 s is used (if the quality measure for FDD
cells is based on CPICH RSCP, for TDD cells and GSM cells).
•
It ranges between 0 and 40 (step size 2).
• If HCS is applied in the serving cell, TOn is calculated as described on the preceding pages.
• If HCS is not applied, then this temporary offset term is not used when calculating Rn.
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Cell reselection with HCS
• Cell Reselection with HCS: R-Criterion and TOn
Rs = Qmeas,s + Qhysts
Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls)
Qmeas
TOn = TEMP_OFFSET n *
W(PENALTY_TIMEn – Tn)
PENALTY_TIMEn
temp. offset used only
when neighbor has
same priority than
serving cell
PENALTY_TIMEn
TOn
TOn
Qmeas,s
TOn = 0
77
TOn=0
Start
Stop
Start
Tn
Tn
Tn
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HCS_PRIOn = HCS_PRIOs
 Ln = 0
© Nokia 2019
•
•
•
After checking the measurement thresholds, the UE has detected suitable cells to camp on.
If HCS is in use, it has reduced the candidate cells for cell reselection to those with highest priority and H >= 0 (given a slow moving UE).
But which of the remaining candidate cells is the best one for cell Reselection?
•
For that, a cell-ranking criterion R was specified:
• Rs = Qmeas,s + Qhy
(for the serving cell)
• Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls) (for candidate neighboring cells for cell
reselection)
•
•
•
The serving cell and the remaining candidate cells are ranked according to criterion R.
The cell ranked with the highest value R is the best cell for the UE to camp on.
Qhysts gives a hysteresis value to make the serving cell more attractive and thus delay the cell Reselection. It exists in two versions:
• If the quality measure is based on CPICH Ec/No, Qhyst2s is used in (FDD cell only);
otherwise the hysteresis value Qhyst1s is used (if the quality measure for FDD
cells is based on CPICH RSCP, for TDD cells and GSM cells).
• It ranges between 0 and 40 (step size 2).
If HCS is applied in the serving cell, TOn is calculated as described on the preceding pages.
If HCS is not applied, then this temporary offset term is not used when calculating Rn.
•
•
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Cell reselection with HCS
Rs = Qmeas,s + Qhysts
Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls)
WCDMA & GSM;
RxLev: 1st Ranking
Qmeas
Rn > Rs  Cell Reselection
Qhyst1
WCEL; 0.. 40; def.: 0 dB
Qmeas,n
Rn
Adjg,s,iQoffset1
HOPx; -50.. 50; def.: 0 dB
Qmeas,s
Qhysts
Rs
Qoffsets,n
Treselection:
WCEL; 0..31; 1; 2s
Adji&sQoffset2
HOPx; -50.. 50; 1; 0 dB
FDD cells & Ec/No:
2nd Ranking
Qhyst2
WCEL; 0.. 40; 2; 2 dB
Example: HCS_PRIOn ≠ HCS_PRIOs  Ln = 1
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