Release with Redirect to LTE Based on
Coverage Check
User Guide
202/1553-HSD 101 02/1 Uen X
Copyright
© Ericsson AB 2017, 2020. All rights reserved. No part of this document may be
reproduced in any form without the written permission of the copyright owner.
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continued progress in methodology, design and manufacturing. Ericsson shall
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Contents
Contents
1
Release with Redirect to LTE Based on Coverage Check
Overview
1
2
Dependencies of Release with Redirect to LTE Based on
Coverage Check
2
3
Feature Operation of Release with Redirect to LTE Based on
Coverage Check
5
4
Network Impact of Release with Redirect to LTE Based on
Coverage Check
8
5
Parameters for Release with Redirect to LTE Based on
Coverage Check
9
6
Performance of Release with Redirect to LTE Based on
Coverage Check
11
7
Activate Release with Redirect to LTE Based on Coverage
Check
12
8
Deactivate Release with Redirect to LTE Based on Coverage
Check
13
9
Engineering Guidelines for Release with Redirect to LTE Based
on Coverage Check
14
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Release with Redirect to LTE Based on Coverage Check
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Release with Redirect to LTE Based on Coverage Check Overview
1
Release with Redirect to LTE Based on
Coverage Check Overview
The Release with Redirect (RWR) to LTE Based on Coverage Check feature
introduces the ability to control the redirection of the LTE-capable UE to cosited LTE cells. “Co-sited” means that the WCDMA and LTE cells share the
same antenna location and orientation.
Access Type:
Feature Identity:
Value Package Name:
Value Package Identity:
Node Type:
Licensing:
WCDMA
FAJ 121 3960
Traffic Management Advanced WCDMA-LTE
FAJ 801 0314
RNC
Licensed feature.
Summary
A coverage threshold that corresponds to the co-sited LTE cell coverage is
checked during 2d and 2f event measurements. The new 2d and 2f
measurements are called 2d-RWR and 2f-RWR accordingly, with the new
measurement identity 14 introduced by this feature. The UE unit is ordered to
perform measurements of downlink (DL) Received Signal Code Power (RSCP)
and reports when the 2d-RWR or 2f-RWR events occur. If the 2f-RWR event is
reported, the redirection to LTE is allowed. If the 2d-RWR event or no event is
reported, the redirection to LTE is not attempted.
The feature provides the following benefits:
— The attempts for redirection to LTE can be avoided, if the co-sited LTE cell
coverage is poor.
— The threshold parameter can be tuned on UTRAN cell and E-UTRAN
frequency basis.
— The redirection to LTE can be allowed after the Incoming Inter Radio Access
Technology (IRAT) Handover, which is restricted before.
When the LTE is deployed on a high frequency band and the WCDMA is on a low
frequency band, the LTE cell coverage is much poorer than the co-sited WCDMA
cell. In this case, the feature can be very beneficial.
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1
Release with Redirect to LTE Based on Coverage Check
2
Dependencies of Release with Redirect to
LTE Based on Coverage Check
The Release with Redirect to LTE Based on Coverage Check feature
associated with six features and three system functions.
Features
Table 1
2
Feature Dependencies
Feature
Relationship
Description
Release with Redirect to LTE (FAJ
121 2174)
Prerequisite
The Release with Redirect to LTE is
an inter-RAT mobility function that
provides LTE-capable UE basic
mobility from WCDMA to LTE.
Release with Redirect to LTE (FAJ
121 2174)
Related
When the Release with Redirect to
LTE Based on Coverage Check
feature is enabled, more conditions
regarding coverage check must be
fulfilled before the redirection to LTE
is attempted.
Packet Switched Handover to LTE
(FAJ 121 4721)
Related
When this feature is active, PS
handover to LTE has higher priority
than release with redirect to LTE in
case of CS release for CS fallback
users.
PS Handover to LTE based on
Related
Measurements in LTE (FAJ 121 3519)
The PS Handover to LTE based on
Measurements in LTE feature has
higher priority than the Release with
Redirect to LTE based on Coverage
Check feature in case of CS release
for CS fallback users. In this case, if
the evaluation of LTE measurement
fails, Release with Redirect to LTE
based on Coverage Check is
attempted.
Release with Redirect to LTE Based
on Measurements in LTE (FAJ 121
4277)
The Release with Redirect to LTE
based on Coverage Check feature has
higher priority than the Release with
Redirect to LTE Based on
Measurements in LTE feature in case
of CS release for CS fallback users. In
this case, if the evaluation of
Related
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Dependencies of Release with Redirect to LTE Based on Coverage Check
Feature
Relationship
Description
Coverage Check fails, Release with
Redirect to LTE Based on
Measurements in LTE is attempted.
Subscriber Based Mobility Using SPID Related
(FAJ 121 3637)
The Subscriber based mobility using
SPID feature can be used to prevent
Release with Redirect Based on
Coverage Check for users with certain
Subscriber Profile IDs.
Service-Based Mobility to LTE (FAJ
121 4928)
Related
The feature Service-Based Mobility to
LTE (FAJ 121 4928) can be used to
prevent Release with Redirect Based
on Coverage Check for users for
which RANAP message E-UTRAN
Service Handover IE is received with
the handover-to-E-UTRAN-shall-notbe-performed value.
Preferred Mobility at CS Fallback
Return to LTE (121 5216)
Related
A WCDMA RAN feature.
For the
UtranCell.releaseRedirectEutra
Triggers.csFallbackCsRelease
trigger, if the feature is enabled and
configured, the Release with Redirect
to LTE based on Coverage Check
feature may be omitted. This depends
on the feature setting.
User Profile Based Mobility (FAJ 121
5184)
Related
If the User Profile Based Mobility
feature is activated, redirection
candidates are filtered according to
the redirectionOrder member of
the
UeMobilityProfile.eutranFreque
ncyConfList attribute.
System Functions
Table 2
Affected System Functions
Function
Description
Channel Switching
When the Release with Redirect to
LTE Based on Coverage Check feature
is enabled, and when the UE is in a
CELL_DCH state, more conditions
regarding coverage check must be
fulfilled before the redirection to LTE is
attempted.
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3
Release with Redirect to LTE Based on Coverage Check
Function
Description
Connection Handling
When the Release with Redirect to
LTE Based on Coverage Check feature
is enabled, more conditions regarding
coverage check must be fulfilled
before the redirection to LTE is
attempted.
Licenses and Hardware Activation
Codes in Ericsson Software Model
To activate the Release with Redirect
to LTE Based on Coverage Check
feature, the license for the feature
must be enabled.
Hardware
No specific hardware requirements.
Limitations
No known limitations.
Network Requirements
The following must be fulfilled at feature activation:
— The license key for the FAJ 121 3960: Release with Redirect to LTE Based on
Coverage Check is installed.
— The FAJ 121 2174: Release with Redirect to LTE feature is activated.
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Feature Operation of Release with Redirect to LTE Based on Coverage Check
3
Feature Operation of Release with Redirect
to LTE Based on Coverage Check
The details information of the feature, including feature operation flows and
the associated tasks are described in this section.
The Release with Redirect to LTE Based on Coverage Check feature works in the
following way:
1. The start of the 2d-RWR or 2f-RWR measurement
When establishing or reestablishing a UE connection in CELL_DCH state, the
2d-RWR and 2f-RWR measurements are started if the following
prerequisites are fulfilled:
— The Release with Redirect to LTE feature is activated.
— The Release with Redirect to LTE Based on Coverage Check feature is
activated.
— The Release with Redirect to LTE Based on Coverage Check feature is
activated on cell level by setting the UtranCell::rwrEutraCc
parameter to ON.
— The Release with Redirect to LTE Based on Coverage Check feature is
activated on IurLink level by setting the IurLink::rwrEutraCc
parameter to ON.
— The configured EutranFreqRelation MOs with
coSitedCellAvailable set to TRUE exist between the best cell and
EutranFrequency MOs after applicable legacy filtering for the Release
with Redirect to LTE feature.
— The UE unit is LTE-capable.
The coverage thresholds for the 2d-RWR and 2f-RWR measurements are
sent in the MEASUREMENT CONTROL message with the measurement
identity 14.
2. The reception of the measurement report
At the reception of a 2d-RWR measurement report, the RNC stores the
information that the redirection to LTE is not allowed.
At the reception of a 2f-RWR measurement report, the RNC stores the
information that the redirection to LTE is allowed.
3. The reception of a supported RWR trigger
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5
Release with Redirect to LTE Based on Coverage Check
The following existing triggers are applicable to the Release with Redirect to
LTE Based on Coverage Check feature:
•
dchToFach: RWR to LTE at the channel switch from DCH to FACH or at
•
csFallbackDchToFach: RWR to LTE after the CS fallback at channel
•
csFallbackCsRelease: RWR to LTE after the CS fallback at CS release,
Circuit Switched (CS) release from Sp0 state
switch from DCH to FACH or at CS release from Sp0 state or Speech
state
but with the Packet Switched (PS) target configuration
Note:
For the trigger, the Release with Redirect to LTE based on
Coverage Check feature may be omitted when the Preferred
Mobility at CS Fallback Return to LTE (FAJ 121 5216) feature is
enabled. This depends on the feature setting. For more
information, see Preferred Mobility at CS Fallback Return to
LTE.
•
fastDormancy: RWR to LTE at fast dormancy with the CELL_DCH
•
normalRelease: RWR to LTE at normal release with the CELL_DCH
source state
source state
Note:
The feature does not cover the fachToUra and FastDormancy
triggers, when the source state is FACH. For those triggers, the
Release with Redirect to LTE feature is applicable.
When the supported RWR triggers from the CELL_DCH state occur, the
legacy checks for the Release with Redirect to LTE feature are done,
including the timer blockEcRelRwrEutraTime for the emergency calls.
Additionally, the following checks are performed:
6
•
Check if the Release with Redirect to LTE Based on Coverage Check
feature is activated.
•
Check if the feature is activated for the best cell.
•
Check if the feature is activated on IurLink for the best cell located in
Drift Radio Network Controller (DRNC).
•
Check if the stored information indicates the redirection to LTE is
allowed.
•
Check if Subscriber Profile ID (SPID) value does not restrict the UE from
being redirected to LTE. The SPID check is according to the existing SPID
checks for the Release with Redirect to LTE feature.
•
Check if the RANAP message E-UTRAN Service Handover IE with the
handover-to-E-UTRAN-shall-not-be-performed value is not received by
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Feature Operation of Release with Redirect to LTE Based on Coverage Check
an RNC when the Service-Based Mobility to LTE (FAJ 121 4928) feature
is activated.
If the Release with Redirect to LTE Based on Coverage Check feature is not
activated or not activated for the best cell, a blind release with redirect to
LTE is attempted.
If the Release with Redirect to LTE Based on Coverage Check feature is not
activated on IurLink for the best cell located in DRNC, a blind release with
redirect to LTE is attempted.
If the stored information indicates the redirection to LTE is allowed, the
redirection is attempted. Otherwise, no attempt is made. The UE unit is
handled according to the legacy procedure for the Release with Redirect to
LTE feature, for example, the switch to CELL_FACH.
An indication of a CS Fallback from LTE (CSFB) is kept throughout the
lifetime of the connection in WCDMA. This means that for a CS+PS multiRAB
connection where the PS part is kept in WCDMA after a coverage check at
release of the CS part, any subsequent CS connections are also treated as
CSFB connections.
The 2d-RWR and 2f-RWR measurements can be started, stopped or modified
due to mobility in CELL_DCH state.
The Release with Redirect to LTE Based on Coverage Check feature is supported
over Iur, if the best cell belongs to a DRNC. The following two situations are
possible:
— When the DRNC is not an Ericsson RNC, or its software version is earlier than
W15.1, the 2d-RWR thresholds are not transferred by an Ericsson proprietary
Information Element (IE) in the RNSAP interface from the DRNC to the
Serving Radio Network Controller (SRNC). If the WcdmaCarrier MO is
configured for the used frequency, 2d-RWR threshold values configured in
the WcdmaCarrier::thresh2dRwrDrnc parameter, under the IurLink MO, in
the SRNC is used. Up to eight different WCDMA carriers can be defined for
each IurLink, with individual event 2d-RWR thresholds set. The
IurLink::rwrEutraCc parameter is used to turn on and off the feature for
each IurLink for the whole RNC.
— When both SRNC and DRNC are Ericsson RNCs, 2d-RWR thresholds are
transferred by an Ericsson proprietary IE in the RNSAP interface, from the
DRNC to the SRNC. These thresholds are then used in the same way as in the
non-Iur case. Turning on and off the feature on the cell level is also possible
when the best cell is in the DRNC. The feature configuration then works the
same as in the non-Iur cases.
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Release with Redirect to LTE Based on Coverage Check
4
Network Impact of Release with Redirect to
LTE Based on Coverage Check
The Release with Redirect to LTE Based on Coverage Check feature has no
network impact.
Capacity and Performance
No impact is expected from this feature.
Interfaces
No impact is expected from this feature.
Other Network Elements
No impact is expected from this feature.
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Parameters for Release with Redirect to LTE Based on Coverage Check
5
Parameters for Release with Redirect to LTE
Based on Coverage Check
The Release with Redirect to LTE Based on Coverage Check feature
introduces seven new parameters and is affected by two parameters.
Table 3
Parameters
Parameter
Type
Description
EutranFreqRelation::
thresh2dRwr
Introduced
See MOM description.
UeMeasControl::timeT
oTrigger2dRwr
Introduced
UeMeasControl::timeT
oTrigger2fRwr
Introduced
UeMeasControl::relTh
resh2fRwr
Introduced
UtranCell::rwrEutraC
c
Introduced
IurLink::rwrEutraCc
Introduced
WcdmaCarrier::thresh
2dRwrDrnc
Introduced
EutranFreqRelation::
coSitedCellAvailable
Affecting
Indicates if the parent
MO UtranCell is co-sited
with the E-UTRAN cell
operating on the
frequency indicated by
EutranFreqRelation::eutr
anFrequencyRef.
Values: TRUE and
FALSE
Default value: FALSE
Note:
During RNC upgrade to
W17.Q4 or later, this
value is set to TRUE for
the existing
EutranFreqRelation
instances for
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Release with Redirect to LTE Based on Coverage Check
Parameter
Type
Description
compatibility with the
Release with the
Redirect to LTE based on
Coverage Check and
Packet Switched
Handover to LTE
features.
UtranCell::releaseRe
direct
Affecting
During RNC upgrade to
W17.Q4 or later, the
value is automatically
changed from EUTRA to
OFF or from
UTRAN_EUTRA to
UTRAN for the UtranCell
MO instances with no
child EutranFreqRelation
MO instances
configured.
Therefore, the behaviors
of the features Release
with Redirect to LTE and
Release with Redirect to
LTE Based on Coverage
Check are not changed
after upgrade.
10
EUtraNetwork.prefMob
ilityToLteCsfbEnable
d
Affecting
Indicates if the Preferred
Mobility at CS Fallback
Return to LTE (FAJ 121
5216) feature is enabled
for this LTE network.
UtranCell.prefMobili
tyToLteCsfbHandling
Affecting
Selects the preferred
mobility to LTE feature
for the Preferred Mobility
at CS Fallback Return to
LTE (FAJ 121 5216)
feature. If the parameter
is set to RWR_LTE_MEAS
or RWR, the "Release with
Redirect to LTE based on
Coverage Check" is
omitted for CS fallback
to LTE trigger.
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Performance of Release with Redirect to LTE Based on Coverage Check
6
Performance of Release with Redirect to LTE
Based on Coverage Check
The Release with Redirect to LTE Based on Coverage Check feature
introduces four new counters and associated with three events and one
counter.
Key Performance Indicators
This feature has no associated Key Performance Indicators (KPIs).
Counters
Introduced counters:
— UtranCell::pmRedirAttRwrEutraCcTrigg
— UtranCell::pmRedirRwrEutraCcAcc
— IurLink::pmRedirAttRwrEutraCcTrigg
— IurLink::pmRedirRwrEutraCcAcc
Related counters:
— UtranCell::pmEushPreventRwrEutra
Events
Table 4
Events
Event
Description
RRC_MEASUREMENT_CONTROL
The existing event to observe the
MEASUREMENT CONTROL messages.
RRC_MEASUREMENT_REPORT
The existing event to observe the
MEASUREMENT REPORT messages.
RRC_MEASUREMENT_CONTROL_FAI The existing event to observe the
LURE
MEASUREMENT CONTROL FAILURE
messages.
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Release with Redirect to LTE Based on Coverage Check
7
Activate Release with Redirect to LTE Based
on Coverage Check
The Redirect to LTE Based on Coverage Check feature requires CXC 403
0168 license key installation and appropriate parameter configuration to be
activated.
Prerequisites
— The FAJ 121 2174: Release with Redirect to LTE feature must be activated
before activation of the FAJ 121 3960: Release with Redirect to LTE Based
on Coverage Check feature.
— License key CXC 403 0168 is installed for the feature. For more information
about license, refer to Licenses and Hardware Activation Codes in Ericsson
Software Model.
— The operators are familiar with the Preferred Mobility at CS Fallback Return
to LTE (FAJ 121 5216) feature.
Steps
1. Set the UtranCell::rwrEutraCc parameter to ON for the selected cells
where the coverage check is applicable.
2. Set the featureState attribute in the
RncFeature=ReleaseRedirectLteCovCheck MO to ACTIVATED.
3. Set EutranFreqRelation::coSitedCellAvailable to TRUE for the cosited cells.
For the configuration of the Release with Redirect to LTE Based on Coverage
Check over Iur, the following points applies to each IurLink:
— The Release With Redirect to LTE Based on Coverage Check feature
must be activated.
— The Release With Redirect to LTE Based on Coverage Check feature is
activated for each IurLink by setting IurLink::rwrEutraCc to ON.
— When the DRNC is not an Ericsson RNC, or its software version is earlier
than W15.1, the WcdmaCarrier under IurLink MO for the used frequency
must be configured. If the feature is turned on for IurLink, while the
WcdmaCarrier for the used frequency is not configured, the feature is not
activated.
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Deactivate Release with Redirect to LTE Based on Coverage Check
8
Deactivate Release with Redirect to LTE
Based on Coverage Check
The Redirect to LTE Based on Coverage Check feature can be deactivated
by the appropriate attributes on the different level.
Prerequisites
This feature has no prerequisites for deactivating.
Steps
1. Set the relevant attributes on different levels:
— To deactivate the feature on the RNC level, set the featureState
attribute in the RncFeature::ReleaseRedirectLteCovCheck MO to
DEACTIVATED.
— To deactivate the feature only in a specific cell, set
theUtranCell::rwrEutraCc parameter of this cell to OFF.
— To deactivate the feature for every IurLink, set the
IurLink::rwrEutraCc for each IurLink to OFF.
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Release with Redirect to LTE Based on Coverage Check
9
Engineering Guidelines for Release with
Redirect to LTE Based on Coverage Check
The purpose of this section is to provide additional information on practical
engineering aspects about how to use parameters to achieve certain
behaviors.
To ensure that the release with redirect to LTE is performed only in location with
good LTE coverage, the thresholds for 2d-RWR and 2f-RWR must be set
appropriately. For details about how to set these thresholds, refer to Inter-Radio
Access Technology.
To ensure that the frequency with good LTE coverage is tried first, it is
recommended to set redirectionOrder to 1 for the EutranFreqRelation MOs with
the lowest thresh2dRwr value.
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