Interworking wcdma to lte

02-1 TA-TC 6541 E01 www.techcom.de Copyright © All rights reserved
Content
GSM / WCDMA / LTE Interworking
 Interworking GSM to WCDMA & LTE
 Interworking WCDMA to GSM
 Interworking WCDMA to LTE
 Interworking LTE zu WCDMA and GSM

 Features and Parameters
Content
Interworking WCDMA to LTE

 Introduction
 RAN Parameter Objects for Mobility from 3G to 4G
 Cell Reselection from 3G to 4G
 PS Redirections and Handovers Between UMTS and LTE
 CSFB & SRVCC
Content
Features and Parameters

WCDMA to LTE related procedures – HO, Redirection,
Reselection
URA_PCH
CELL_DCH
CELL_FACH
CELL_PCH
UTRA RRC Connected Mode
Idle Mode
Connected
Idle
3G LTE
Reselection

UMTS Interoperability with LTE
Mode Function
Idle mode UMTS-to-LTE cell reselection
Idle mode LTE-to-UMTS cell reselection
Connected mode PS service LTE-to-UMTS PS redirection or handover
LTE-to-UMTS inter-RAT handover based on the UMTS cell load status
UMTS-to-LTE fast cell reselection
Service-based UMTS-to-LTE PS redirection or handover
Coverage-based UMTS-to-LTE PS redirection or handover
Load-based UMTS-to-LTE PS redirection or handover
CS service R8-compliant LTE-to-UMTS CSFB
LTE-to-UMTS CSFB based on the UMTS cell load status
UMTS-to-LTE fast return
CSFB guarantee for LTE emergency calls
CSFB guarantee for LTE common calls
Single radio voice call continuity (SRVCC) from LTE to UMTS with PS Handover
The functions supported by the interoperability between UMTS and LTE
• RIM During the RAN information management (RIM) procedure, RAN information, such as cell system information and load information,
can be mutually exchanged between GSM and UMTS systems or between UMTS and LTE systems for better implementation of the
interoperability procedure.
• CSFB After CSFB is introduced, a UE on the LTE network needs to be redirected or handed over to the UMTS network for service
processing when performing CS services. This aims at reusing the UMTS network to provide traditional CS services for UEs on the LTE
network.
• SRVCC(Single Radio Voice Call Continuity) When a UE on the LTE network performs voice over Internet Protocol (VoIP) services, the
SRVCC converts VoIP services to CS services on the UMTS network for voice service continuity.

 Introduction
 CSFB & SRVCC
Content

Managed Object Models (MOMs)
LTE Interoperability Configuration MOM View

Managed Object Models (MOMs)
Configuration of Neighboring RNCs, Neighboring BSCs, Neighboring UMTS Cells, Neighboring GSM Cells, and Neighboring LTE Cells
MOM View:
4G neighbours

Type MO Description Remarks
GSM cell configuration UEXT2GCELL Refers to the MO for configuring GSM cells adjacent to the boundary
of UMTS cells.
-
Cell configuration for
GU interoperability
U2GNCELL Refers to the MO for configuring neighboring GSM cells for UMTS
cells.
This MO is used to configure neighbor relationships between
UMTS cells and neighboring GSM cells and relevant
parameters.
UCELLINTERRATHOCOV Refers to the MO for configuring parameters for coverage-based inter-
RAT handover measurement algorithm in cells.
-
UCELLINTERRATHONCOV Refers to the MO for configuring parameters for non-coverage-based
inter-RAT handover measurement algorithm in cells.
-
UCELLLDR Refers to the MO for configuring parameters for load reshuffling
algorithm in cells.
-
LTE cell configuration ULTECELL Refers to the MO for configuring LTE cells adjacent to the boundary of
UMTS cells.
-
UL interoperability
ULTENCELL Refers to the MO for configuring neighboring LTE cells for UMTS
cells.
This MO is used to configure neighbor relationships between
UMTS cells and neighboring LTE cells and relevant
parameters.
UCELLU2LTEHOCOV Refers to the MO for configuring parameters for coverage-based
UMTS-LTE handover/redirection measurement algorithm in cells.
-
UCELLU2LTEHONCOV Refers to the MO for configuring parameters for non-coverage-based
UMTS-LTE handover measurement algorithm in cells.
-
UCELLNFREQPRIOINFO Refers to the MO for configuring the information about priorities of E-
UTRA (LTE) adjacent frequencies in cells.
-
UCELLSIBSWITCH Refers to the MO for cell system information block (SIB) switch. This MO is used to configure the SIB19 switch.
interoperability
UCELLHOCOMM Refers to the MO for configuring cell-level handover common
parameters.
This MO is used to configure handover or redirection
parameters during interoperability.
RNC configuration for
GU interoperability
UINTERRATHOCOV Refers to the MO for configuring parameters for coverage-based inter-
RAT handover measurement algorithm in the RNC.
Use the CELLINTERRATHOCOV parameter if it has been
configured. Otherwise, use the RNC-level parameter.
UINTERRATHONCOV Refers to the MO for configuring parameters for non-coverage-based
inter-RAT handover measurement algorithm in the RNC.
Use the CELLINTERRATHOCOV parameter if it has been
RNC configuration for
UL interoperability
UU2LTEHOCOV Refers to the MO for configuring parameters for coverage-based
UMTS-LTE handover/redirection measurement algorithm in the RNC.
Use the CELLU2LTEHOCOV parameter if it has been
UU2LTEHONCOV Refers to the MO for configuring parameters for non-coverage-based
UMTS-LTE handover measurement algorithm in the RNC.
Use the CELLU2LTEHOCOV parameter if it has been
UMTS Interoperability MOs

 Introduction
 CSFB & SRVCC
Content

WCDMA to LTE – Cell Reselection
URA_PCH
CELL_DCH
CELL_FACH
CELL_PCH
Idle Mode
Connected
Idle
3G LTE
Reselection
• When camping on the UMTS cells in idle mode or when finishing a service and camping on the UMTS network, a
UL multimode UE continues to receive system information from the serving UMTS cell.
• Information element SIB19 contained in the system information carries the absolute priorities of the serving UMTS
cell and EARFCNs (LTE or GSM).
• Based on the SIB19 information, the UE will trigger measurements if measurement triggering conditions are met.
• Based on the measurement result, the UE camps on the best cell through reselection.

Cell Reselection with LTE
Cell Reselection between UMTS and LTE includes:
WRFD-020126 Mobility Between UMTS and LTE Phase 1
implemented on the LTE side based on absolute priorities of cells
LTE-to-UMTS cell reselection – e.g., when LTE coverage
is weak or limited
UMTS-to-LTE cell reselection – to provide better experience
of high-speed services and reduce load of the UMTS network
UMTS-to-LTE quick cell reselection – fast state transitions
to improve user experience

Cell Reselection with LTE – General Parameters
SIB19 must be broadcast in the cell – SIB19 selected under the SibCfgBitMap parameter
SIB19 carries:
• absolute priority of the serving UMTS cell
• absolute priorities of the LTE frequencies
• cell reselection thresholds
UE performs cell reselection based on the absolute priority criteria, including
RSRQ of the LTE frequency (RSRQSwitch = True) or RSRP as the quality measure.
Spriority – absolute priority level of the serving UMTS cell
Npriority – absolute priority of the E-UTRA frequency
MO:UCELLSIBSWITCH
SibCfgBitMap = {SIB2, SIB4, SIB12, SIB18,
SIB19, SIB11BIS}, default = 0 for all
MO:UCELLSIBSWITCH
SibCfgBitMap = {SIB2, SIB4, SIB12, SIB18,
SIB19, SIB11BIS}, default = 0 for all
MO: UCELLNFREQPRIOINFO RSRQSwitch – default = 0: False
• Whether SIB19 contains the RSRQ-related "ThdToHighRSRQ", "ThdToLowRSRQ", "EQqualmin" and "ThdServingLow2"(See "ADD
UCELLSELRESEL") parameters. When this parameter is set to True, SIB19 contains these parameters. When this parameter is set
to False, SIB19 does not contain these parameters.
MO: UCELLNFREQPRIOINFO RSRQSwitch – default = 0: False
• Whether SIB19 contains the RSRQ-related "ThdToHighRSRQ", "ThdToLowRSRQ", "EQqualmin" and "ThdServingLow2"(See "ADD
UCELLSELRESEL") parameters. When this parameter is set to True, SIB19 contains these parameters. When this parameter is set
to False, SIB19 does not contain these parameters.
MO: UCELLSELRESEL Spriority – Range: 0~7, default = 4MO: UCELLSELRESEL Spriority – Range: 0~7, default = 4
MO: UCELLNFREQPRIOINFO Npriority – Range: 0~7, default = NoneMO: UCELLNFREQPRIOINFO Npriority – Range: 0~7, default = None
If the RSRQSwitch is set to 0: False then every time the RSRP is used for cell reselection to LTE: under MO UCELLNFREQPRIOINFO
the following parameters are used: ThdToLow (RSRP Threshold for Low-prio-freq Reselection) and ThdToHigh (RSRP Threshold for High-
prio-freq Reselection)

Cell Reselection with LTE – Concept
• Cell reselection from WCDMA to LTE when UE is in idle mode, Cell_PCH or URA_PCH state in WCDMA layer.
• The UE, on operator’s preference, selects to camp on LTE layer based on absolute layers priorities once coverage is available.
LTE
3G
MO: UCELLSELRESEL Spriority
MO: UCELLNFREQPRIOINFO Npriority
MO:UCELLSELRESEL ThdPrioritySearch1
MO:UCELLSELRESEL ThdPrioritySearch2
MO: UCELLSELRESEL ThdServingLow
MO: UCELLNFREQPRIOINFO EQrxlevmin
ThdToLow
ThdToLowRSRQ
ThdToHigh
ThdToHighRSRQ
MO: UCELLNFREQPRIOINFO EARFCN
MO: UCELLNFREQPRIOINFO EMeasBW
LTE Layer Prioritylower higher
• the priority-based LTE reselection mechanism, uses signal strength criteria (3GPP Rel. 8) or signal quality
criteria if the UE is > 3GPP Rel. 8 AND RSRQSwitch is set to 1.
• SIB 19 provides: Serving
WCDMA cell & IRAT cell
information for E-UTRA
• RNC compiles SIB 19 and
provides to WBTS for SysInfo
broadcast
• Priority for SIB 19 can be set
with RNC level parameter:
SibCfgBitMap

LTE Reselection – Measurements – Higher Prio
• If the UE has received absolute priority information for different layers and there is a layer with higher priority
than the current serving layer has, the UE follows this rule:
UE starts to search higher priority layers immediately. Each (Nlayers * 60) seconds
• it checks whether an LTE coverage is available or not. Nlayers refers to number of configured higher priority
layers.
• if the UE detects LTE layer it performs inter RAT measurements according to measurement events in UTRAN.
LTE layer 1
Priority 7
WCDMA layer
Priority 5 from SIB19
SIB19 e.g.:
in idle mode, Cell_PCH or URA_PCH

LTE Reselection – Measurements – Lower Prio
• One of the following criteria need to be fulfilled in order to start measurements of lower priority layers by the UE
(the operator can choose which criteria is used in the system via setting the WCEL/CellSelQualMeas parameter
value):
1. RX level (CPICH RSCP) in the serving cell falls below threshold:
Measured RSCP – Qrxlevmin (default -116dBm) <= ThdPrioritySearch1 (default 4dB)
2. Quality level (CPICH Ec/No) in the serving cell falls below threshold:
Measured Ec/No – Qqualmin (default -18dB) <= ThdPrioritySearch2 (default 2dB)
OR
LTE layer 2
Priority 3
WCDMA layer
Priority 5 from SIB19
SIB19 e.g.:
in idle mode, Cell_PCH or URA_PCH

LTE Cell Reselection – Decision
To higher priority layer:
Measured RSRP – EQrxlevmin (default -140Bm) >= ThdToHigh (default 10dB) during the Treselection time
OR (if the UE > 3GPP Rel. 8 and RSRQSwitch is set to 1)
Measured RSRQ – EQqualmin (default -22dB) >= ThdToHighRSRQ (default 3dB) during the Treselection time
To lower priority layer:
{Measured RSCP – Qrxlevmin (default -116dBm) <= ThdServingLow (default 2dB)
OR
Measured Ec/No – Qqualmin (default -18dB) <= ThdServingLow2 (default 2 dB)}
AND
{(Measured RSRP – EQrxlevmin (default -140Bm) > ThdToLow (default 10dB) during the Treselection time
OR (if the UE > 3GPP Rel. 8 and RSRQSwitch is set to 1)
Measured RSRQ – EQqualmin (default -22dB) > ThdToLowRSRQ (default 3dB)}
• 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

UMTS-to-LTE Quick Cell Reselection
A UMTS/LTE multi-mode UE camping on the UMTS network can initiate UMTS-to-LTE cell reselection only when it is in
the CELL_PCH or idle state.
• State transition to the CELL_PCH or idle state is slow because the state transition is triggered only when the UE
does not transmit or receive service data during the time length of an inactivity timer.
• To accelerate the UMTS-to-LTE cell reselection, you need to enable the UMTS-to-LTE quick cell reselection function
by running the SET URRCTRLSWITCH command with FAST_RETURN_LTE_BY_CELL_SELECT_SWITCH under
PROCESSSWITCH4 set to ON.

Type of UEs Before the Function Is
Enabled…
After the Function Is
Enabled…
UEs that are not enabled with
enhanced fast dormancy
State transition from the CELL_DCH state to the CELL_PCH state is
triggered when the UE does not transmit or receive service data
during the time length specified by PsInactTmrForInt (for interactive
services) or PsInactTmrForBac (for background services)
State transition from the CELL_DCH state to the
CELL_PCH state or idle mode is triggered when the UE
does not transmit or receive service data during the
time length specified by PsInactTmr- ForFstDrmDch
UEs that are
enabled with
enhanced fast
dormancy and
in the CELL_DCH state
When RNC_EFD_D2F_SWITCH under OptimizationSwitch in
URRCTRLSWITCH is selected, the UE transits from CELL_DCH to
CELL_FACH when it does not transmit or receive service data
during the time length specified by PsInactTmrForFstDrmDch and
then transits from CELL_FACH to CELL_PCH.
When RNC_EFD_D2F_SWITCH under OptimizationSwitch
is not selected, state transition from CELL_DCH to CELL_PCH is
triggered when the UE does not transmit or receive service data
during the time length specified by PsInactTmrForFstDrmDch
The UE is able to transit from CELL_DCH directly to
CELL_PCH or idle mode when it does not transmit or
receive service data during the time length specified by
PsInactTmrForFstDrmDch
UEs that are enabled with
enhanced fast
dormancy and in the
CELL_FACH state
State transition from CELL_FACH to CELL_PCH is triggered when
the UE does not transmit or receive service data during the time
length specified by PsInactTmrForFstDrmFach.
State transition from CELL_FACH to
CELL_PCH or idle mode is triggered when the UE does
not transmit or receive service data during the time
length specified by
PsInactTmrForFstDrmFach
The lists the inactivity timers that are used and state transitions that are triggered before and after the UMTS-to-LTE quick cell reselection function
is enabled:
UMTS-to-LTE Quick Cell Reselection – Inactivity timers
State transition from CELL_DCH to CELL_PCH or the idle state is done by running the SET URRCTRLSWITCH command with
UL_DUAL_MODE_UE_D2P_OR_D2I_SWITCH set to an appropriate value under PROCESSSWITCH4.
• When UL_DUAL_MODE_UE_D2P_OR_D2I_SWITCH is cleared, the UE transits from CELL_DCH to CELL_PCH.
• When UL_DUAL_MODE_UE_D2P_OR_D2I_SWITCH is selected, the UE transits from CELL_DCH to the idle state.
UL_DUAL_MODE_UE_D2P_OR_D2I_SWITCH under PROCESSSWITCH4 is cleared by default.
• Select UL_DUAL_MODE_UE_D2P_OR_D2I_SWITCH if some UEs in the network do not support state transition from CELL_DCH to
CELL_PCH.

 Introduction
 CSFB & SRVCC
Content

URA_PCH
CELL_DCH
CELL_FACH
CELL_PCH
Idle Mode
Connected
Idle
3G LTE
PS Redirections and Handovers from UMTS to LTE

UMTS-to-LTE PS Redirection – Motivation
Cell Reselection with LTE
Absolute priorities for layer selection introduced in RAN2067 are available
in Idle Mode, Cell_PCH or URA_PCH state
• LTE capable UEs are able to move from WCDMA to LTE when LTE
coverage is available
• Load balancing mechanism is not available
• In high load states of WCDMA cell, LTE capable UEs may experience
low throughputs instead of switching to LTE layer
Problem: no possible moving UEs with active PS services to LTE
Smartphones often stay in a connected
mode Cell_DCH state or Cell_FACH
state and it is resource consuming.
LTE
WCDMA
Allways in WCDMA
if active!!!
UMTS-to-LTE PS Redirection and Handover
• redirect or handover active UEs from WCDMA to LTE
• if WCDMA cell is congested, LTE capable UEs may be redirected
to LTE layer.
• Blind redirection is good alternative when WCDMA and LTE cells
are co-located and have well overlapping coverage areas
Problems: in case of non-overlaping WCDMA/LTE coverage
Problem appears when there is no
coverage and theoretically should be, this
may cause ‘ping-pong effect’
LTE
WCDMA
Moves to a
coverage hole

UMTS-to-LTE PS Redirection
During a UMTS-to-LTE PS redirection, the RNC sends the UE an RRC Connection Release message,
which contains LTE frequencies.
Redirections are:
• non-neighboring-cell-based redirection
• neighboring-cell-based redirection - neighboring LTE cell configuration are required
Redirections can also be classified into
• blind redirection and
• measurement-based redirection - UE supports the measurement of LTE cell signal quality.
Non-neighboring-cell-based redirection if:
• The target frequency for redirection is obtained from the configured frequencies (EARFCN)
• UEs perform non-neighboring-cell-based redirections when no neighboring LTE cell is configured
• if non-neighboring-cell-based redirection is enabled, the non-neighboring-cell-based redirection
is preferred even if neighboring LTE cells are configured
Neighboring-cell-based redirection:
• The target redirection frequency is obtained from the neighboring LTE cell frequencies as indicated
by the LTEArfcn parameter
MO: ULTECELL
LTEArfcn
0..65535, none
MO: ULTECELL
LTEArfcn
0..65535, none
• This parameter specifies the downlink frequency used by an LTE cell.

UMTS-to-LTE PS Blind Redirection
• A blind redirection is required when a UE not supporting LTE signal quality measurement attempts to perform a UMTS-to-LTE
handover or redirection.
• During the blind redirection, if LTE coverage does not exist, the UE has to wait for 15 to 20 seconds and then falls back to the UMTS
network.
• During the 15 to 20 seconds, the UE is out of service.
• After the UE falls back to the UMTS network, the service-based UMTS-to-LTE redirection algorithm will trigger another blind
redirection.
To prevent such blind redirections between UTMS and LTE, the RNC performs the following steps:
Problem appears when there is no
coverage and theoretically should be, this
may cause ‘ping-pong effect’
LTE
WCDMA
1. During a UMTS-to-LTE blind redirection, the RNC saves the UE's IMSI and RRC
connection release time after receiving an RRC CONNECTION RELEASE message
from the UE.
2. When the UE initiates a phone call, the RNC receives a Common ID message from
the CN. If the blind redirection function is enabled, the RNC determines whether the
UE has performed a blind redirection within last 30 seconds based on the UE's IMSI
included in the Common ID message, the reception time of this message, and the
previously mentioned RRC connection release time.
3. If the UE has performed a blind redirection within last 30 seconds, the RNC starts a
penalty timer for the blind redirection. Before the penalty timer expires, the RNC
prohibits the UE from performing UMTS-to-LTE blind redirections, regardless of
whether these blind redirections are triggered by services, loads, or event 1F. The
length of the penalty timer is determined by bits 0 through 15 under the
RsvU32Para10 parameter in the SET UALGORSVPARA command.
U2LBlindRedirPingpongTimer SET UHOCOMM
MO: UHOCOMM
U2LBlindRedirPingpongTimer
0~65535 s; 60 s
MO: UHOCOMM
U2LBlindRedirPingpongTimer
0~65535 s; 60 s
MO: UCELLHOCOMM U2LBlindRedirSwitch OFF~0, ON~1; OFF
When the switch is turned on, the BSC6900 directly performs a UMTS-to-LTE redirection on the UE not supporting
LTE cell measurements, and a UE that camps on a UMTS cell without the coverage of the neighboring LTE cell
cannot access the network for some time. Therefore, the switch is turned on only when the UMTS cell that the UE
camps on is under the coverage of the neighboring LTE cell.
MO: UCELLHOCOMM U2LBlindRedirSwitch OFF~0, ON~1; OFF
When the switch is turned on, the BSC6900 directly performs a UMTS-to-LTE redirection on the UE not supporting
LTE cell measurements, and a UE that camps on a UMTS cell without the coverage of the neighboring LTE cell
cannot access the network for some time. Therefore, the switch is turned on only when the UMTS cell that the UE
camps on is under the coverage of the neighboring LTE cell.

UMTS-to-LTE PS Redirection – Signalling process

UMTS-to-LTE PS Handover – Signalling process

UMTS-to-LTE PS Redirections and HOs – Switch
Types of Redirections:
- To enable non-neighboringcell- based redirection, select HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH
under HoSwitch1 in the SET UCORRMALGOSWITCH command.
MO: UCORRMALGOSWITCH HoSwitch1
2. HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH: This switch specifies whether handover and
redirection from UMTS to LTE are allowed. When this switch is turned on, redirection from UMTS to LTE is
allowed but handover is prohibited. During the redirection procedure, the LTE frequencies configured by using
the "ADD UCELLNFREQPRIOINFO" command are used for the redirection, and the BSC6900 does not
consider whether the best cell is configured with neighboring LTE cells. When this switch is turned off, both
redirection and handover from UMTS to LTE are allowed. The LTE frequencies configured by using the "ADD
ULTENCELL" command are used for the redirection and handover
MO: UCORRMALGOSWITCH HoSwitch1
2. HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH: This switch specifies whether handover and
redirection from UMTS to LTE are allowed. When this switch is turned on, redirection from UMTS to LTE is
allowed but handover is prohibited. During the redirection procedure, the LTE frequencies configured by using
the "ADD UCELLNFREQPRIOINFO" command are used for the redirection, and the BSC6900 does not
consider whether the best cell is configured with neighboring LTE cells. When this switch is turned off, both
redirection and handover from UMTS to LTE are allowed. The LTE frequencies configured by using the "ADD
ULTENCELL" command are used for the redirection and handover
When neighboring LTE cells are configured, it is recommended that
HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH be deselected so that neighboring-cell-based redirections are
performed.

UMTS-to-LTE PS redirections and handovers
• Coverage-based UMTS-to-LTE PS redirections and handovers.
• Service-based UMTS-to-LTE PS redirections and handovers.
• Load-based UMTS-to-LTE PS redirections and handovers.
Operation Application Scenario
Coverage-based UMTS to LTE PS
redirection or handovers
UMTS and LTE are deployed together and the UMTS
coverage is poor.
Service-based UMTS to LTE PS
redirections or handovers
• A CSFB UE is still performing a PS connection after it
falls back to UMTS and the voice service is completed
• An UE initiates only a PS connection when it is located
in the UMTS and LTE overlapping coverage area
• An UE initiates only a PS connection in UMTS and
moves to the LTE coverage area
Load-based UMTS to LTE PS
redirection or handovers
UMTS cell is located is located in the area coverd also by
LTE cell(s) and it become congested (basic congestion
state)

Coverage-based UMTS-to-LTE PS Redirections and
Handovers – Process
Trigger Phase
Decision Phase
Measuremnt
Phase
Execution Phase
Trigger cause: RNC receives the
event 2D or 1F measurement report
RNC allowes a redirection or handover
to LTE
RNC determines whether to start the LTE
Measurement and measurement execution
RNC decides which procedure to trigger:
a blind redirection, a measurement based
redirection or a handover to LTE
• If no GSM network or inter-frequency UMTS network is deployed, the UE is not handed over to the LTE network until event 1F is triggered.
• Event 1F indicates that the UMTS signals are very weak and call drops may occur.
• Therefore, the UE is shifted to the LTE network through a blind redirection.
• You are advised to set the trigger threshold for event 1F the same as that for event 2D in the scenario where no GSM and inter-frequency
UMTS networks are deployed

Coverage-based UMTS-to-LTE PS Redirections and
Handovers – Conditions
1. There are no CS RABs among the UE's RABs.
2. All PS RABs for the UE can be shifted to LTE through a handover or redirection. An RAB can be shifted to LTE through a handover or
redirection only when the IE EUTRAN Service Handover in the RAB Assignment Request message is not set to ‘’Handover to E-UTRAN
shall not be performed" and HO_TO_EUTRAN_SHOULD_BE_PERFORM under the EUTRANSHIND parameter is selected.
3. The UE supports both UMTS and LTE.
4. LTE network is available. The RNC uses the following methods to determine whether the LTE network is available:
• If the switch for frequency-based redirection in case that no neighboring cells is configured is set to on, that is,
HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH under the HoSwitch1 parameter is selected, the LTE network is
available when an LTE frequency is configured.
• If the switch for frequency-based redirection in case that no neighboring cells is configured is set to off, the LTE network is
available when a neighboring LTE cell is configured.
5. Switches related to coverage-based UMTS-to-LTE interoperability have been turned on.
• The general switch for UMTS-to-LTE PS interoperability is turned on. This switch is configured by HO_LTE_PS_OUT_SWITCH
under the HoSwitch parameter.
• Condition a or condition b is met
 a: The coverage-based UMTS-to-LTE PS redirection switch is turned on. That is,
HO_U2L_COV_PS_REDIRECT_SWITCH under the HoSwitch1 parameter is selected.
 b: The coverage-based UMTS-to-LTE PS handovers switch is turned on. That is, HO_U2L_COV_PS_HO_SWITCH
under the HoSwitch1 parameter is selected. However, HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH under
the HoSwitch1 parameter is not selected.

Event 2D/2F
Events 2D and 2F are defined as follows:
• When the measurement quantity is less than the threshold for event 2D, the UE reports event 2D to RNC to request a measurement.
• When the measurement quantity exceeds the threshold for event 2F, the UE reports event 2F to RNC to stop the measurement.
For a coverage-based UMTS-to-LTE redirection or handover, the RNC selects the parameters related to the threshold for event 2D and
the threshold for event 2F as follows.
• If UMTS cells on a network use the same frequency and coexist with GSM or LTE cells, RNC selects GSM or LTE cells' parameters
related to the threshold for event 2D and the threshold for event 2F.
• If UMTS cells on a network use different frequencies and coexist with GSM or LTE cells: RNC selects inter-frequency UMTS cells'
parameters related to the threshold for event 2D
 and the threshold for event 2F when the CoexistMeasThdChoice parameter in the ADDUCELLHOCOMM or SET UHOCOMM
command is set to COEXIST_MEAS_THD_CHOICE_INTERFREQ.
 The RNC selects GSM or LTE cells' parameters related to the threshold for event 2D and the threshold for event 2F when
CoexistMeasThdChoice is set to COEXIST_MEAS_THD_CHOICE_INTERRA.
MO: UCELLHOCOMM
CoexistMeasThdChoice
COEXIST_MEAS_THD_CHOICE_INTERFREQ, COEXIST_MEAS_THD_CHOICE_INTERRAT;
COEXIST_MEAS_THD_CHOICE_INTERFREQ
MO: UCELLHOCOMM
CoexistMeasThdChoice
COEXIST_MEAS_THD_CHOICE_INTERFREQ, COEXIST_MEAS_THD_CHOICE_INTERRAT;
COEXIST_MEAS_THD_CHOICE_INTERFREQ

CPICH EC/I0 / RSCP Triggered HHO (2D)
- The quality of the currently used frequency is below a certain threshold- The quality of the currently used frequency is below a certain threshold
Time to trigger I-RAT
measurements
CPICH/ECNO1
CPICH/ECNO 2
CPICH/ECNO 3
M
time
Threshold 2D
MO: UCELLU2LTEHOCOV LTEReportMode : PERIODICAL_REPORTING~0, EVENT_TRIGGER~1; PERIODICAL_REPORTING~0MO: UCELLU2LTEHOCOV LTEReportMode : PERIODICAL_REPORTING~0, EVENT_TRIGGER~1; PERIODICAL_REPORTING~0
MO: UCELLU2LTEHOCOV U2LTEHO2DEventType : ONLYECNO, ONLYRSCP, ECNOANDRSCP; ECNOANDRSCPMO: UCELLU2LTEHOCOV U2LTEHO2DEventType : ONLYECNO, ONLYRSCP, ECNOANDRSCP; ECNOANDRSCP
Threshold 2F
MO: UINTERRATHOCOV gives the RSCP/EcNO values for 2D/2F events – as seen in Chapter 2 per type of
connection (Rel. 99, HSPA, CS, PS)

Event 3A
Reporting mode of measurement reports:
• A UE can periodically report measurement reports or in event-triggered reporting mode. LTEReportMode
specifies which reporting mode is used.
• For a coverage-based UMTS-to-LTE PS redirection or handover, the measurement reports can be periodically
reported or in event-3A-triggered mode. The LTEPeriodReportInterval parameter specifies the interval at which
the measurement reports are reported.
When the RNC receives a 3A measurement report from the UE, it performs decision and execution of the UE's
redirection or handover.
The following formulas are fulfilled within a duration specified by 3a: QUsed <= TUsed - H3a/2 and MOtherRAT >=
TOtherRAT + H3a/2
MO: UCELLU2LTEHOCOV LTEPeriodReportInterval : NON_PERIODIC_REPORT, 250, 500, 1000, 2000, 3000, 4000, 6000, 8000,
12000, 16000, 20000, 24000, 28000, 32000, 64000 ms; 1000 ms
MO: UCELLU2LTEHOCOV LTEPeriodReportInterval : NON_PERIODIC_REPORT, 250, 500, 1000, 2000, 3000, 4000, 6000, 8000,
12000, 16000, 20000, 24000, 28000, 32000, 64000 ms; 1000 ms

• Event 3A:
• Quality of used UTRAN frequency below certain threshold AND quality of non-used inter-
RAT frequency above certain threshold
• Event 3A:
• Quality of used UTRAN frequency below certain threshold AND quality of non-used inter-
RAT frequency above certain threshold
CPICH
RSRP or RSRQ
M
time
Threshold for used
UTRAN frequency
Threshold for non-used
LTE frequency
HHO Execution (3A)
MO: UCELLU2LTEHOCOV
UsedFreqThdRSCP -115~-25; - 107 dBm
MO: UCELLU2LTEHOCOV
UsedFreqThdRSCP -115~-25; - 107 dBm
MO: UCELLU2LTEHOCOV
UsedFreqThdEcNo -24~0; - 13 dB
MO: UCELLU2LTEHOCOV
UsedFreqThdEcNo -24~0; - 13 dB
MO: UCELLU2LTEHOCOV LTEMeasQuanOf3A
RSRP~0, RSRQ~1; RSRP~0
MO: UCELLU2LTEHOCOV LTEMeasQuanOf3A
RSRP~0, RSRQ~1; RSRP~0
MO: UCELLU2LTEHOCOV Hystfor3A
0~7.5 dB; 2 dB
MO: UCELLU2LTEHOCOV Hystfor3A
0~7.5 dB; 2 dB
MO: UCELLU2LTEHOCOV TrigTime3A
0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640, 1280, 2560, 5000 ms; 0 ms
MO: UCELLU2LTEHOCOV TrigTime3A
0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640, 1280, 2560, 5000 ms; 0 ms
MO: UCELLU2LTEHOCOV
TargetRatThdRSRP -140~-44; - 107 dBm
MO: UCELLU2LTEHOCOV
TargetRatThdRSRP -140~-44; - 107 dBm
MO: UCELLU2LTEHOCOV TargetRatThdRSRQ
-19.5~-3; - 10 dB
MO: UCELLU2LTEHOCOV TargetRatThdRSRQ
-19.5~-3; - 10 dB

Coverage-based UMTS-to-LTE PS Redirections and HO –
Cell level Parameters 1/2
UCELLU2LTEHOCOV MO defines the cell-oriented coverage-based UMTS-to-LTE handover/redirection measurement algorithm parameters.
Parameter Description
Cell ID Unique ID of a cell
LTE Report Mode Mode for a UE to report LTE cell measurement results.
When the parameter is set to PERIODICAL_REPORTING, the UE reports measurement results periodically. When the parameter is
set to EVENT_TRIGGER, the UE reports measurement results by triggering an event.
RSCP Threshold for Used
Frequency
RSCP threshold of the used frequency. Event 3A is triggered when the quality of the used frequency is lower than the threshold and
the quality of the target cell is higher than the corresponding decision threshold as indicated by "TargetRatThdRSRP" or
"TargetRatThdRSRQ".
Ec/No Threshold for Used
Frequency
Ec/No threshold of the used frequency. Event 3A is triggered when the quality of the used frequency is lower than the threshold and
the quality of the target cell is higher than the corresponding decision threshold as indicated by "TargetRatThdRSRP" or
"TargetRatThdRSRQ".
Measurement Quantity for Event
3A in LTE
LTEMeasQuanOf3A
Measurement quantity of the target LTE network reported in event 3A for a coverage-based handover.
RSRP indicates the average signal power received at all REs carrying reference signals in a symbol.
RSRQ is equal to RSRP divided by RSSI. A factor (N) is used to adjust the ratio if the bandwidths used for measuring RSRP and
RSSI are different. That is, RSRQ = N x RSRP/RSSI..
3A Event Hysteresis Hysteresis for reporting event 3A.
According to simulation results, the shadow fading variance of high-speed cells covering highways is small due to flat ground and few
barriers. Therefore, decrease the parameter value to 1.5 dB. The shadow fading variance of low-speed cells covering many high
buildings is large. Therefore, increase the parameter value to 3.0 dB.
3A Event Trigger Delay Time Time-to-trigger for reporting event 3A. The value of this parameter is related to slow fading.
Layer 3 Filter Coefficient for LTE
Measurement
Layer 3 filtering coefficient for LTE cell measurements.
The RNC delivers the layer 3 filtering coefficient to a UE to smooth measurement results based on the following formula:
Fn = (1-a) x Fn-1 + a x Mn
where
a = 1/(2^(k/2))
k indicates the layer 3 filtering coefficient.
Fn-1 indicates the measurement result after the filtering of the preceding time.
Mn indicates the latest measurement result.
Fn indicates the measurement result after filtering for this time.

LTE Measurement Timer
Length
Length of a timer for LTE cell measurements. The BSC6900 starts the timer to perform LTE cell measurements. When the timer expires, the
BSC6900 stops measuring LTE cells. If the parameter is set to 0, the BSC6900 keeps measuring the LTE cells.
RSRP Threshold During
PS Handover to LTE
Reference signal received power (RSRP) threshold for LTE cell measurements. If "LTEReportMode" is set to EVENT_TRIGGER, event 3A is
triggered when the UE detects the quality of the target cell is higher than the threshold and the quality of the used frequency is lower than the
corresponding threshold. If "LTEReportMode" is set to PERIODICAL_REPORTING, a handover is triggered when the BSC6900 detects that
the quality of the target cell is higher than the threshold. The RNC carries the Threshold other system IE in the measurement control message
sent to the UE. This IE is used to calculate the actual value of the inter-RAT measurement threshold. Actual value = Threshold other system -
25 [dBm], Threshold other system = GUI value - 116.
RSRQ Threshold During
PS Handover to LTE
RSRQ threshold for LTE cell measurements. If "LTEReportMode" is set to EVENT_TRIGGER, event 3A is triggered when the UE detects the
quality of the target cell is higher than the threshold and the quality of the used frequency is lower than the corresponding threshold. If
"LTEReportMode" is set to PERIODICAL_REPORTING, a handover is triggered when the BSC6900 detects that the quality of the target cell is
higher than the threshold. The RNC carries the Threshold other system IE in the measurement control message sent to the UE. This IE is used
to calculate the actual value of the inter-RAT measurement threshold. Actual value = Threshold other system/2 [dB], Threshold other system =
GUI value - 40.
LTE Period Reporting
Interval
Interval at which a UE periodically reports LTE cell measurements to the BSC6900. If "LTEPeriodReportInterval" is set to
NON_PERIODIC_REPORT, the UE cannot periodically report LTE cell measurements, which is not recommended.
LTE Period Reporting
HO Hysteresis
Hysteresis for periodically reporting LTE signal quality. When LTE cell measurements are periodically reported and the target frequency quality
meets the following requirement, the UE performs handovers or redirections:
• Mother_RAT is greater than or equal to Tother_RAT plus HystforPeriodLTE/2, where
• Mother_RAT refers to the LTE cell measurement result. Tother_RAT refers to the threshold for RSRP or RSRQ decision of the LTE system
for PS services. Setting this parameter reduces the error decision rate caused by signal jitter.
According to simulation results, the shadow fading variance of high-speed cells covering highways is small due to flat ground and few barriers.
Therefore, decrease the parameter value to 1.5 dB.
The shadow fading variance of low-speed cells covering many high buildings is large. Therefore, increase the parameter value to 3.0 dB.
Event 2D Type for LTE
Measurement
Type of event 2D for triggering LTE measurement. When this parameter is set to ONLYECNO, only event 2D whose decision threshold is
Ec/N0 can trigger LTE measurement. When this parameter is set to ONLYRSCP, only event 2D whose decision threshold is RSCP can trigger
LTE measurement. When this parameter is set to ECNOANDRSCP, event 2D whose decision threshold is either Ec/N0 or RSCP can trigger
LTE measurement.
Cell level Parameters 2/2

UU2LTEHOCOV MO defines the RNC-oriented coverage-based UMTS-to-LTE handover/redirection measurement algorithm parameters.
RNC level Parameters 1/3
LTE Report Mode
LTEReportMode
Mode for a UE to report LTE cell measurement results.
When the parameter is set to PERIODICAL_REPORTING, the UE reports measurement results periodically. When
the parameter is set to EVENT_TRIGGER, the UE reports measurement results by triggering an event.
RSCP Threshold for Used
Frequency
UsedFreqThdRSCP
RSCP threshold of the used frequency. Event 3A is triggered when the quality of the used frequency is lower than
the threshold and the quality of the target cell is higher than the corresponding decision threshold as indicated by
"TargetRatThdRSRP" or "TargetRatThdRSRQ".
Ec/No Threshold for Used
Frequency
UsedFreqThdEcNo
Ec/No threshold of the used frequency. Event 3A is triggered when the quality of the used frequency is lower than
the threshold and the quality of the target cell is higher than the corresponding decision threshold as indicated by
"TargetRatThdRSRP" or "TargetRatThdRSRQ".
Measurement Quantity for Event
3A in LTE
LTEMeasQuanOf3A
Measurement quantity of the target LTE network reported in event 3A for a coverage-based handover.
RSRP indicates the average signal power received at all REs carrying reference signals in a symbol.
RSRQ is equal to RSRP divided by RSSI. A factor (N) is used to adjust the ratio if the bandwidths used for
measuring RSRP and RSSI are different. That is, RSRQ = N x RSRP/RSSI.
3A Event Hysteresis
Hystfor3A
Hysteresis for reporting event 3A.
According to simulation results, the shadow fading variance of high-speed cells covering highways is small due to
flat ground and few barriers. Therefore, decrease the parameter value to 1.5 dB. The shadow fading variance of
low-speed cells covering many high buildings is large. Therefore, increase the parameter value to 3.0 dB.
3A Event Trigger Delay Time
TrigTime3A
Time-to-trigger for reporting event 3A. The value of this parameter is related to slow fading.
Layer 3 Filter Coefficient for LTE
Measurement
U2LTEFilterCoef
Layer 3 filtering coefficient for LTE cell measurements.
The RNC delivers the layer 3 filtering coefficient to a UE to smooth measurement results based on the following
formula:
Fn = (1-a) x Fn-1 + a x Mn where a = 1/(2^(k/2)) and k indicates the layer 3 filtering coefficient.
Fn-1 indicates the measurement result after the filtering of the preceding time. Mn indicates the latest
measurement result.
Fn indicates the measurement result after filtering for this time.

LTE Measurement Timer Length
U2LTEMeasTime
Length of a timer for LTE cell measurements. The BSC6900 starts the timer to perform LTE cell measurements. When
the timer expires, the BSC6900 stops measuring LTE cells. If the parameter is set to 0, the BSC6900 keeps measuring
the LTE cells.
RSRP Threshold During PS
Handover to LTE
TargetRatThdRSRP
Reference signal received power (RSRP) threshold for LTE cell measurements. If "LTEReportMode" is set to
EVENT_TRIGGER, event 3A is triggered when the UE detects the quality of the target cell is higher than the threshold
and the quality of the used frequency is lower than the corresponding threshold. If "LTEReportMode" is set to
PERIODICAL_REPORTING, a handover is triggered when the BSC6900 detects that the quality of the target cell is
higher than the threshold. For details about this parameter, see section 10.3.7.30 "Inter-RAT measurement reporting
criteria" in 3GPP TS 25.331. The RNC carries the Threshold other system IE in the measurement control message sent
to the UE. This IE is used to calculate the actual value of the inter-RAT measurement threshold. Actual value =
Threshold other system - 25 [dBm], Threshold other system = GUI value - 116.
RSRQ Threshold During PS
Handover to LTE
TargetRatThdRSRQ
RSRQ threshold for LTE cell measurements. If "LTEReportMode" is set to EVENT_TRIGGER, event 3A is triggered
when the UE detects the quality of the target cell is higher than the threshold and the quality of the used frequency is
lower than the corresponding threshold. If "LTEReportMode" is set to PERIODICAL_REPORTING, a handover is
triggered when the BSC6900 detects that the quality of the target cell is higher than the threshold. For details about this
parameter, see section 10.3.7.30 "Inter-RAT measurement reporting criteria" in 3GPP TS 25.331. The RNC carries the
Threshold other system IE in the measurement control message sent to the UE. This IE is used to calculate the actual
value of the inter-RAT measurement threshold. Actual value = Threshold other system/2 [dB], Threshold other system =
GUI value - 40.
LTE Period Reporting Interval
LTEPeriodReportInterval
Interval at which a UE periodically reports LTE cell measurements to the BSC6900. If "LTEPeriodReportInterval" is set
to NON_PERIODIC_REPORT, the UE cannot periodically report LTE cell measurements, which is not recommended.
LTE Period Reporting HO
Hysteresis
HystforPeriodLTE
Hysteresis for periodically reporting LTE signal quality. When LTE cell measurements are periodically reported and the
target frequency quality meets the following requirement, the UE performs handovers or redirections:
Mother_RAT is greater than or equal to Tother_RAT plus HystforPeriodLTE/2, where
Mother_RAT refers to the LTE cell measurement result. Tother_RAT refers to the threshold for RSRP or RSRQ decision
of the LTE system for PS services. Setting this parameter reduces the error decision rate caused by signal jitter.
According to simulation results, the shadow fading variance of high-speed cells covering highways is small due to flat
ground and few barriers. Therefore, decrease the parameter value to 1.5 dB. The shadow fading variance of low-speed
cells covering many high buildings is large. Therefore, increase the parameter value to 3.0 dB.

Thd for Cov U2L HO Fail by
Phy CH Fail
U2LPhyChFailNum
Threshold for the number of coverage-based UMTS-to-LTE handover failures caused by physical channel
failures. During a coverage-based UMTS-to-LTE handover, if the UE sends a HANDOVER FROM UTRAN
FAILURE message with a cause value of "physicalChannelFailure" to the RNC, the RNC regards that the
handover fails. When the number of such failures is greater than or equal to this parameter value, the RNC
punishes the UE by prohibiting the UE from initiating coverage-based UMTS-to-LTE handovers within the
period specified by the "PenaltyTimeForPhyChFail" parameter.
When this parameter is set to 0, no punishment is imposed on UEs that have experienced coverage-based
UMTS-to-LTE handover failures caused by physical channel failures.
Punishment Cov U2L HO Fail
by Phy CH Fail
PenaltyTimeForPhyChFail
Period in which UEs that have experienced coverage-based UMTS-to-LTE handover failures caused by
physical channel failures are punished. Within the period specified by this parameter, the RNC punishes
these UEs by prohibiting them from initiating coverage-based UMTS-to-LTE handovers.
When this parameter is set to 0, no punishment is imposed on UEs that have experienced coverage-based
UMTS-to-LTE handover failures caused by physical channel failures.
Event 2D Type for LTE
Measurement
U2LTEHO2DEventType
Type of event 2D for triggering LTE measurement. When this parameter is set to ONLYECNO, only event
2D whose decision threshold is Ec/N0 can trigger LTE measurement. When this parameter is set to
ONLYRSCP, only event 2D whose decision threshold is RSCP can trigger LTE measurement. When this
parameter is set to ECNOANDRSCP, event 2D whose decision threshold is either Ec/N0 or RSCP can
trigger LTE measurement.

00-40 www.techcom.de Copyright © All rights reservedTA-TC 6541 E01
Service-based UMTS-to-LTE PS redirections and HOs
Process:
Trigger Phase
Decision Phase
Measuremnt Phase
Execution Phase
Trigger cause: RB establishment,
RB reconfiguration, low activity state,
periodic trigger, best cell change or Iur Release
Message delivery in the CS domain
RNC allowes a redirection or handover to LTE
All Triggers:
• RAB setup: The RNC receives a Radio Bearer Setup Complete message from
the UE.
• RAB reconfiguration: The RNC receives a Radio Bearer Setup Complete
message from the UE, except during the D2F and D2P state transition
processes.
• Low activity state: Conditions for a D2F or D2P state transition are met when the
UE enters the low-speed data transmission state.
• Periodic triggering: A timer for the periodic service-based UMTS-to-LTE PS
redirection or handover expires. The timer is set by bit0 to bit15 of
RsvU32Para15 parameter.
• Iu CS release: The RNC receives an Iu Release message from the CS domain
of the CN.
• RB release: A Radio Bearer Release Complete message is received.
• Best cell change: 1D event is reported.
• Other causes: A migration process is complete or the LTE-to-UMTS penalty
timer expires.

Service-based UMTS-to-LTE PS redirections and HOs
Triggers – Parameter
Trigger Source for
Service-based U2L
HO/Redir
U2LServTrigSource
- Bit Field Type
1. U2L_SERV_RAB_SETUP_TRIGGER: Whether a service-based UMTS-to-LTE PS handover or redirection can be triggered when a PS
services is being set up. When this switch is set to on, a service-based UMTS-to-LTE PS handover or redirection can be triggered in the
preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection cannot be triggered in the preceding
scenario.
2. U2L_SERV_LOWACTIVE_TRIGGER: Whether a service-based UMTS-to-LTE PS handover or redirection can be triggered when the PS
service is in the low-rate transmission state. When this switch is set to on, a service-based UMTS-to-LTE PS handover or redirection can be
triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection cannot be triggered
in the preceding scenario.
3. U2L_SERV_PERIOD_TRIGGER: Whether service-based UMTS-to-LTE PS handovers or redirections can be triggered periodically according
to the duration specified by the "U2LServPrdTrigTimerLen" parameter. When this switch is set to on, a service-based UMTS-to-LTE PS handover
or redirection can be triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection
cannot be triggered in the preceding scenario.
4. U2L_SERV_RB_REL_TRIGGER: Whether a service-based UMTS-to-LTE handover or redirection can be triggered when the service is being
released. When this switch is set to on, a service-based UMTS-to-LTE handover or redirection can be triggered in the preceding scenario. When
this switch is set to off, a service-based UMTS-to-LTE handover or redirection cannot be triggered in the preceding scenario.
5. U2L_SERV_IUCS_REL_TRIGGER: Whether a service-based UMTS-to-LTE handover or redirection can be triggered when the Iu-CS
connection of the service is being released. When this switch is set to on, a service-based UMTS-to-LTE handover or redirection can be triggered
in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE handover or redirection cannot be triggered in the
preceding scenario.
6. U2L_SERV_OTHER_TRIGGER: Whether service-based UMTS-to-LTE handovers or redirections can be triggered by other service change
processes such as intra-RAT migration or upon expiry of the timer specified by the "U2LPunishSwitch" parameter. When this switch is set to on, a
service-based UMTS-to-LTE handover or redirection can be triggered in the preceding scenario. When this switch is set to off, a service-based
UMTS-to-LTE handover or redirection cannot be triggered in the preceding scenario.
Default value • U2L_SERV_RAB_SETUP_TRIGGER:0,
• U2L_SERV_LOWACTIVE_TRIGGER:1,
• U2L_SERV_PERIOD_TRIGGER:0,
• U2L_SERV_RB_REL_TRIGGER:0,
• U2L_SERV_IUCS_REL_TRIGGER:0,
• U2L_SERV_OTHER_TRIGGER:0
MO: UU2LTEHONCOV RNC level parameter

Service-based UMTS-to-LTE PS Redirections and HOs
Conditions
2. All PS RABs for the UE can be shifted to LTE through a handover or redirection. An RAB can be shifted to LTE through a handover
or redirection only when the IE EUTRAN Service Handover in the RAB Assignment Request message is not set to "Handover to E-
UTRAN shall not be performed" and HO_TO_EUTRAN_SHOULD_BE_PERFORM under the EUTRANSHIND parameter is
selected.
3. UE supports both UMTS and LTE.
4. LTE network is available. The RNC uses the following methods to determine whether the LTE network is available:
– If HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH under the HoSwitch1 parameter is selected, the LTE network is
available when an LTE frequency is configured.
– If HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH is not selected, the LTE network is available when a neighboring
LTE cell is configured.
5. Switches related to service-based UMTS-to-LTE interoperability have been turned on.
• The general switch for UMTS-to-LTE PS interoperability is turned on. This switch is configured by
HO_LTE_PS_OUT_SWITCH under the HoSwitch parameter.
• Condition a (for redirection) or condition b (for handovers) is met.
 a: cell-level or RNC-level switch for the service-based UMTS-to-LTE PS redirection is set to on  select
RESERVED_SWITCH_0_BIT28 under the RsvSwitch0 parameter &  select
HO_LTE_SERVICE_PS_OUT_SWITCH under the RsvSwitch0 parameter. Setting of the cell-level switch takes
precedence.
 b: The switch for non-neighboring-cell-based redirection (HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH) is
set to off but the cell-level or RNC-level switch for the service-based UMTS-to-LTE PS handover is set to on. To set the
cell-level switch to on, select RESERVED_SWITCH_0_BIT32 under the RsvSwitch0 parameter. To set the RNC-
levelswitch to on, select HO_LTE_SERVICE_PSHO_OUT_SWITCH under the HoSwitch parameter. Setting of the cell-
level switch takes precedence.
6. If the measurement-based redirection or handover is enabled, the RNC checks whether thetotal number of UEs in compressed
mode in the current cell exceeds the threshold for the number of users in compressed mode for triggering the service-based UMTS-
to-LTE measurement (RsvU32Para0).

Load-based UMTS-to-LTE PS redirections and HOs
Process:
Trigger Phase
Decision Phase
Measuremnt Phase
Execution Phase
Trigger cause: Basic congestion of a cell
Triggeres the LDR action of UMTS to LTE
PS redirection or handover
RNC allowes a redirection or handover to LTE
UE selection for LDR
Selection
• If the LDR action of UMTS-to-LTE PS handover is triggered
when the UMTS cell is in the basic congestion state, the RNC
enables UL or GUL multi-mode UEs carrying only PS services
to be redirected or handed over to LTE to facilitate inter-RAT
load balancing

Load-based UMTS-to-LTE PS redirections and HOs
Conditions
2. All PS RABs for the UE can be shifted to LTE through a handover or redirection. An RAB can be shifted to LTE through a handover or
redirection only when the IE EUTRAN Service Handover in the RAB Assignment Request message is not set to "Handover to E-UTRAN shall
not be performed" and HO_TO_EUTRAN_SHOULD_BE_PERFORM under the EUTRANSHIND parameter is selected.
3. UE supports both UMTS and LTE.
4. An LTE network is available. The RNC uses the following methods to determine whether the LTE network is available:
• If HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH under the HoSwitch1 parameter is selected, the LTE network is available
when an LTE frequency is configured.
• If HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH is not selected, the LTE network is available when a neighboring LTE cell is
configured.
5. Switches related to load-based UMTS-to-LTE interoperability have been turned on.
• The general switch for UMTS-to-LTE PS interoperability is turned on. This switch is configured by HO_LTE_PS_OUT_SWITCH
under the HoSwitch parameter.
• The LDR action of UMTS-to-LTE PS handover is enabled. These switches can be turned on by running the command ADD
UCELLLDR or MOD UCELLLDR.
• Either of the following is true:
 The HO_U2L_LOAD_PS_REDIRECT_SWITCH check box under the HoSwitch1 parameter is selected.
 The HO_U2L_LOAD_PS_HO_SWITCH check box under the HoSwitch1 parameter is selected but the
HO_U2L_REDIR_BASED_ABSOLUTE_FREQ_SWITCH check box under this parameter is not selected.

Non coverage-based UMTS-to-LTE PS redirections and
Handovers – Cell level Parameters 1/3
UCELLU2LTEHONCOV MO defines the cell-oriented non-coverage-based UMTS-to-LTE handover/redirection measurement algorithm
parameters and is used to configure related parameters
Cell ID Unique ID of a cell
Report Type of LTE
Measurement
Specifies the type of measurement result that a UE needs to carry in an event-triggered or periodical measurement report. When this
parameter is set to Measurementquantity, the parameter value is the same as that of "Measurement Quantity for Event 3C
Measurement of LTE". When this parameter is set to Both, the UE needs to report measurement results of both the types: Reference
Signal Received Power (RSRP) and Reference Signal Receiving Quality (RSRQ).
Layer 3 Filter
Coefficient for LTE
Measurement
Specifies the layer 3 filter coefficient for the LTE measurement. Layer 3 filter coefficient is sent to the UE and the UE performs filtering
of the measurements according to the following formula: Fn=(1-a)*Fn-1 + a*Mn
The variables in the formula are defined as follows: a=1/(2^(k/2)), where k is this parameter. Fn-1 is the old filtered measurement
result. Mn is the latest received measurement result from physical layer measurements. Fn is the updated filtered measurement
result.
LTE Measurement
Timer Length
Length of a timer for LTE cell measurements. The BSC6900 starts the timer to perform LTE cell measurements. When the timer
expires, the BSC6900 stops measuring LTE cells. If the parameter is set to 0, the BSC6900 keeps measuring the LTE cells.
Measurement Quantity
for Event 3C
Measurement of LTE
Specifies the measurement quantity of a handover target LTE system in an event 3C measurement report sent by a UE during a
handover that is not based on coverage. This parameter can be set to RSRP or RSRQ. Note that what specific measurement results
are reported depends on the setting of "Report Type of LTE Measurement“. RSRP is the average power of signals received on all
resource elements (REs) that carry reference signals within a certain symbol.
RSRQ is defined as the ratio of RSRP to RSSI (RSRQ = N x RSRP/RSSI). The coefficient N is introduced to adjust possible
bandwidth difference in both types of measurement.
Hysteresis for Event 3C Specifies the hysteresis for a UE to report event 3C.
Time to Trigger Event
3C
Specifies the interval time between detection of event 3C and sending of the measurement report. How to set this parameter is related
to slow fading.
RSRP Threshold
During PS Handover to
LTE
RSRP threshold for event 3C for LTE cell measurements during a non-coverage-based handover. If RSRP is used as the
measurement quantity for event 3C, event 3C can be triggered only when the signal quality of the target cell is greater than the
threshold. The RNC carries the Threshold other system IE in the measurement control message sent to the UE. This IE is used to
calculate the actual value of the inter-RAT measurement threshold. Actual value = Threshold other system - 25 [dBm], Threshold
other system = GUI value - 116.

RSRQ Threshold
During PS Handover
to LTE
RSRQ threshold for event 3C for LTE cell measurements during a non-coverage-based handover. If RSRQ is used as the measurement
quantity for event 3C, event 3C can be triggered only when the signal quality of the target cell is greater than the threshold. The RNC carries the
Threshold other system IE in the measurement control message sent to the UE. This IE is used to calculate the actual value of the inter-RAT
measurement threshold. Actual value = Threshold other system/2 [dB], Threshold other system = GUI value - 40.
Best Cell Change
Triggered LTE
Measure Switch
Whether the RNC triggers service-based LTE cell handovers or redirections when the best cell that a UE camps on changes. The best cell can
be an intra-frequency or inter-frequency cell. When the switch is turned on, the BSC6900 triggers service-based LTE cell handovers or
redirections after the best cell changes. When the switch is turned off, the BSC6900 does not trigger service-based LTE cell handovers or
redirections after the best cell changes.
Trigger Source for
Service-based U2L
HO/Redir
preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection cannot be triggered in the
preceding scenario.
triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection cannot be triggered
in the preceding scenario.
3. U2L_SERV_PERIOD_TRIGGER: Whether service-based UMTS-to-LTE PS handovers or redirections can be triggered periodically according
to the duration specified by the "U2LServPrdTrigTimerLen" parameter. When this switch is set to on, a service-based UMTS-to-LTE PS
handover or redirection can be triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or
redirection cannot be triggered in the preceding scenario.
4. U2L_SERV_RB_REL_TRIGGER: Whether a service-based UMTS-to-LTE handover or redirection can be triggered when the service is being
released. When this switch is set to on, a service-based UMTS-to-LTE handover or redirection can be triggered in the preceding scenario. When
this switch is set to off, a service-based UMTS-to-LTE handover or redirection cannot be triggered in the preceding scenario.
connection of the service is being released. When this switch is set to on, a service-based UMTS-to-LTE handover or redirection can be
triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE handover or redirection cannot be triggered in
the preceding scenario.
processes such as intra-RAT migration or upon expiry of the timer specified by the "U2LPunishSwitch" parameter. When this switch is set to
on, a service-based UMTS-to-LTE handover or redirection can be triggered in the preceding scenario. When this switch is set to off, a service-
based UMTS-to-LTE handover or redirection cannot be triggered in the preceding scenario.

Service-based U2L
Algorithm Switch
1. HO_LTE_SERVICE_PSHO_OUT_SWITCH: Whether to allow service-based UMTS-to-LTE PS handovers. When this switch is set to on, the BSC6900 is
allowed to deliver service-based LTE cell measurement control messages and initiate service-based UMTS-to-LTE PS handovers. When this switch is set to off,
the BSC6900 is prohibited from initiating service-based UMTS-to-LTE PS handovers.
2. HO_LTE_SERVICE_PS_OUT_SWITCH: Whether to allow service-based UMTS-to-LTE redirections. When this switch is set to on, the BSC6900 is allowed to
deliver service-based LTE cell measurement control messages and initiate service-based UMTS-to-LTE PS redirections. When this switch is set to off, the
BSC6900 is prohibited from initiating service-based UMTS-to-LTE PS redirections.
3. HO_LTE_SERVICE_NEED_RSCP_SWITCH: Whether the corresponding algorithm can be used to judge signal quality of the LTE cell preliminarily according
to the RSCP of the best cell before service-based UMTS-to-LTE handovers or redirections. When this switch is set to on, the algorithm takes effect and the RNC
sends an intra-frequency measurement control message to the UE to measure RSCP of the best cell. If RSCP reported by the UE is lower than
"U2LNCovRscpThd", the LTE coverage is regarded poor and UMTS-to-LTE handovers or redirections are prohibited. When this switch is set to off, the algorithm
does not take effect. Note: This algorithm applies to scenarios where the best UTRAN cell and the neighboring E-UTRAN cell share the same site.
4. HO_LTE_SERVICE_BLIND_FIRST_SWITCH: Whether a blind redirection can be preferentially performed to switch a UE to an LTE network if the UE meets
conditions for a service-based UMTS-to-LTE handover or redirection and there is a blind handover neighboring cell or a blind handover adjacent frequency.
When this switch is set to on, a blind redirection is preferentially performed. When this switch is set to off, LTE measurement is preferentially performed and then
a handover or redirection is performed based on the measurement report from the UE.
RSCP Threshold for
Non-coverage-based
U2L
Threshold for RSCP of the best cell.
When the "HO_LTE_SERVICE_NEED_RSCP_SWITCH" in the "SET UCORRMALGOSWITCH" command is set to on, there are the following cases:
If the RSCP of the best cell is lower than this threshold, the LTE cell coverage is regarded as poor and a service-based UMTS-to-LTE handover or redirection
cannot be triggered.
If the RSCP of the best cell is higher than this threshold, a service-based UMTS-to-LTE handover or redirection will be triggered.
When the "HO_CSFB_BASED_RSCP_FAST_RETURN_SWITCH" in the "SET UCORRMALGOSWITCH" command is set to on, there are the following cases:
If the RSCP of the best cell is lower than this threshold, the LTE cell coverage is regarded as poor and a UMTS-to-LTE blind fast return cannot be triggered.
If the RSCP of the best cell is higher than this threshold, a UMTS-to-LTE blind fast return will be triggered.
U2L Virtual Grid
Information Low
Threshold
Lower threshold for the UMTS-to-LTE virtual grid information. If the success rate of UMTS-to-LTE handovers or redirections is lower than this threshold in a grid,
the BSC6900 marks this grid as a class II virtual grid. The BSC6900 enables some UEs in class II virtual grids to perform LTE measurement-based CSFB fast
return based on the value of "ProbaofU2LforClassIIGrid" in the "SET UVIRTUALGRID" command, so that the BSC6900 learns the success rate of the UMTS-to-
LTE handover and redirection in class II virtual grids. In this situation, the BSC6900 prohibits other UEs from performing CSFB fast return in class II virtual grids.
U2L Virtual Grid
Information High
Threshold
Upper threshold for the UMTS-to-LTE virtual grid information. If the success rate of UMTS-to-LTE handovers or redirections is higher than this threshold in a grid,
the BSC6900 marks this grid as a class I virtual grid. In class I virtual grids, the BSC6900 allows UEs to perform blind redirection-based CSFB fast return.

UU2LTEHONCOV MO defines the RNC-oriented non-coverage-based UMTS-to-LTE handover/redirection measurement algorithm
parameters.
Handovers – RNC level Parameters 1/4
Report Type of LTE
Measurement
LTEMeasTypOf3C
Specifies the type of measurement result that a UE needs to carry in an event-triggered or periodical measurement report. When this parameter is set
to Measurementquantity, the parameter value is the same as that of "Measurement Quantity for Event 3C Measurement of LTE". When this parameter
is set to Both, the UE needs to report measurement results of both the types: Reference Signal Received Power (RSRP) and Reference Signal
Receiving Quality (RSRQ).
Layer 3 Filter Coefficient for
LTE Measurement
U2LTEFilterCoef
Specifies the layer 3 filter coefficient for the LTE measurement. Layer 3 filter coefficient is sent to the UE and the UE performs filtering of the
measurements according to the following formula: Fn=(1-a)*Fn-1 + a*Mn
The variables in the formula are defined as follows: a=1/(2^(k/2)), where k is this parameter. Fn-1 is the old filtered measurement result. Mn is the
latest received measurement result from physical layer measurements. Fn is the updated filtered measurement result.
LTE Measurement Timer
Length
U2LTEMeasTime
Length of a timer for LTE cell measurements. The BSC6900 starts the timer to perform LTE cell measurements. When the timer expires, the BSC6900
stops measuring LTE cells. If the parameter is set to 0, the BSC6900 keeps measuring the LTE cells.
Measurement Quantity for
Event 3C Measurement of LTE
LTEMeasQuanOf3C
Specifies the measurement quantity of a handover target LTE system in an event 3C measurement report sent by a UE during a handover that is not
based on coverage. This parameter can be set to RSRP or RSRQ. Note that what specific measurement results are reported depends on the setting of
"Report Type of LTE Measurement“. RSRP is the average power of signals received on all resource elements (REs) that carry reference signals within
a certain symbol. RSRQ is defined as the ratio of RSRP to RSSI (RSRQ = N x RSRP/RSSI). The coefficient N is introduced to adjust possible
bandwidth difference in both types of measurement.
Hysteresis for Event 3C
Hystfor3C
Specifies the hysteresis for a UE to report event 3C.
Time to Trigger Event 3C
TrigTime3C
Specifies the interval time between detection of event 3C and sending of the measurement report. How to set this parameter is related to slow fading.
RSRP Threshold During PS
Handover to LTE
TargetRatThdRSRP
RSRP threshold for event 3C for LTE cell measurements during a non-coverage-based handover. If RSRP is used as the measurement quantity for
event 3C, event 3C can be triggered only when the signal quality of the target cell is greater than the threshold.For details about this parameter, see
section 10.3.7.30 "Inter-RAT measurement reporting criteria" in 3GPP TS 25.331. The RNC carries the Threshold other system IE in the measurement
control message sent to the UE. This IE is used to calculate the actual value of the inter-RAT measurement threshold. Actual value = Threshold other
system - 25 [dBm], Threshold other system = GUI value - 116.
RSRQ Threshold During PS
Handover to LTE
TargetRatThdRSRQ
RSRQ threshold for event 3C for LTE cell measurements during a non-coverage-based handover. If RSRQ is used as the measurement quantity for
event 3C, event 3C can be triggered only when the signal quality of the target cell is greater than the threshold. For details about this parameter, see
section 10.3.7.30 "Inter-RAT measurement reporting criteria" in 3GPP TS 25.331. The RNC carries the Threshold other system IE in the measurement
control message sent to the UE. This IE is used to calculate the actual value of the inter-RAT measurement threshold. Actual value = Threshold other
system/2 [dB], Threshold other system = GUI value - 40.

Best Cell Change Triggered LTE
Measure Switch
BestCellTrigLTEMeasSwitch
Whether the RNC triggers service-based LTE cell handovers or redirections when the best cell that a UE camps on changes.
The best cell can be an intra-frequency or inter-frequency cell. When the switch is turned on, the BSC6900 triggers service-
based LTE cell handovers or redirections after the best cell changes. When the switch is turned off, the BSC6900 does not
trigger service-based LTE cell handovers or redirections after the best cell changes.
U2L Penalty Timer
U2LPunishTimer
Timer during which service-based ping-pong handovers or redirections between UMTS cells and LTE cells are prevented. When
this parameter is set to 0, the service-based ping-pong handovers or redirections between UMTS cells and LTE cells are
allowed.
U2L Punish Switch
U2LPunishSwitch
Whether the function of preventing service-based ping-pong handovers or redirections between UMTS cells and LTE cells takes
effect. When this switch is turned on, the function takes effect. Otherwise, the function does not take effect.
LTE FDD Cell Redirect Ping Pong
Prevent Switch
AntiPinpanLteFddRedrSwitch
Whether a UE that is redirected from the LTE network to the UMTS network can be redirected back to an LTE FDD frequency.
When this switch is turned on, the UE cannot initiate the redirection to an LTE FDD frequency, which prevents ping-pong
redirections between the UMTS network and the LTE network. When this switch is turned off, the UE can be redirected to an
LTE FDD frequency.
Thd for No-Cov U2L HO Fail by Phy
CH Fail
U2LPhyChFailNum
Threshold for the number of non-coverage-based UMTS-to-LTE handover failures caused by physical channel failures. During a
non-coverage-based UMTS-to-LTE handover, if the UE sends a HANDOVER FROM UTRAN FAILURE message with a cause
value of "physicalChannelFailure" to the RNC, the RNC regards that the handover fails. When the number of such failures is
greater than or equal to this parameter value, the RNC punishes the UE by prohibiting the UE from initiating non-coverage-
based UMTS-to-LTE handovers within the period specified by the "PenaltyTimeForPhyChFail" parameter.
When this parameter is set to 0, no punishment is imposed on UEs that have experienced non-coverage-based UMTS-to-LTE
handover failures caused by physical channel failures.
Punish No-Cov U2L HO Fail by Phy
CH Fail
PenaltyTimeForPhyChFail
Period in which UEs that have experienced non-coverage-based UMTS-to-LTE handover failures caused by physical channel
failures are punished. Within the period specified by this parameter, the RNC punishes these UEs by prohibiting them from
initiating non-coverage-based UMTS-to-LTE handovers.
When this parameter is set to 0, no punishment is imposed on UEs that have experienced non-coverage-based UMTS-to-LTE
handover failures caused by physical channel failures.
Penalty Time for Service-based U2L
Meas Expiry
U2LServMcTimeOutPunishTime
The penalty duration during which service-based LTE measurement cannot be started again after the previous service-based
LTE measurement control is released. The types of service-based LTE measurement control release that will be punished are
specified by the PERFENH_SERV_LTE_MC_PUNISH_OPT_SWITCH under the "PerfEnhanceSwitch5" parameter in the "SET
UCORRMPARA" command.

Trigger Source for Service-based
U2L HO/Redir
U2LServTrigSource
preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection cannot be triggered in the
preceding scenario.
triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS handover or redirection cannot be
triggered in the preceding scenario.
3. U2L_SERV_PERIOD_TRIGGER: Whether service-based UMTS-to-LTE PS handovers or redirections can be triggered periodically
according to the duration specified by the "U2LServPrdTrigTimerLen" parameter. When this switch is set to on, a service-based UMTS-to-LTE
PS handover or redirection can be triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE PS
handover or redirection cannot be triggered in the preceding scenario.
4. U2L_SERV_RB_REL_TRIGGER: Whether a service-based UMTS-to-LTE handover or redirection can be triggered when the service is
being released. When this switch is set to on, a service-based UMTS-to-LTE handover or redirection can be triggered in the preceding
scenario. When this switch is set to off, a service-based UMTS-to-LTE handover or redirection cannot be triggered in the preceding scenario.
connection of the service is being released. When this switch is set to on, a service-based UMTS-to-LTE handover or redirection can be
triggered in the preceding scenario. When this switch is set to off, a service-based UMTS-to-LTE handover or redirection cannot be triggered in
the preceding scenario.
processes such as intra-RAT migration or upon expiry of the timer specified by the "U2LPunishSwitch" parameter. When this switch is set to
on, a service-based UMTS-to-LTE handover or redirection can be triggered in the preceding scenario. When this switch is set to off, a service-
based UMTS-to-LTE handover or redirection cannot be triggered in the preceding scenario.
Timer for Periodic Service-based
U2L
U2LServPrdTrigTimerLen
Timer for periodically triggering service-based UMTS-to-LTE PS handover or redirection. The value 0 indicates that this timer is
disabled.
LTE Measurement Duration with
Only Signaling
U2LTESigMeasTime
Timer for LTE measurement when the UE has only signaling connections. The RNC starts this timer for LTE
measurement. When the timer expires, the RNC stops LTE measurement.

Load-based U2L Penalty Timer
Length
U2LPunishTimerLenForLoad
Penalty timer for preventing load-based ping-pong handovers or redirections between UMTS and LTE cells. When the
value of this parameter is set to 0, the penalty on load-based UMTS-to-LTE handovers or redirections does not take effect.
RSCP Threshold for Non-
coverage-based U2L
U2LNCovRscpThd
Threshold for RSCP of the best cell.
When the "HO_LTE_SERVICE_NEED_RSCP_SWITCH" in the "SET UCORRMALGOSWITCH" command is set to on,
there are the following cases:
If the RSCP of the best cell is lower than this threshold, the LTE cell coverage is regarded as poor and a service-based
UMTS-to-LTE handover or redirection cannot be triggered.
If the RSCP of the best cell is higher than this threshold, a service-based UMTS-to-LTE handover or redirection will be
triggered.
When the "HO_CSFB_BASED_RSCP_FAST_RETURN_SWITCH" in the "SET UCORRMALGOSWITCH" command is set
to on, there are the following cases:
If the RSCP of the best cell is lower than this threshold, the LTE cell coverage is regarded as poor and a UMTS-to-LTE
blind fast return cannot be triggered.
If the RSCP of the best cell is higher than this threshold, a UMTS-to-LTE blind fast return will be triggered.
RSCP Measure Timer for Non-
coverage-based U2L
U2LNCovRscpPrdTimer
Period for reporting the non-coverage-based UMTS-to-LTE RSCP intra-frequency measurement report.
U2L RSRP Threshold with Only
Signaling
SigTargetRatThdRSRP
Reference signal received power (RSRP) threshold for reporting event 3C during LTE measurement control for non-
coverage-triggered UMTS-to-LTE redirection with only signaling connections. If the RSRP of an LTE cell reaches this
threshold, the UE reports event 3C. If the RSRP of an LTE cell falls below this threshold, the UE does not report event 3C.
For details about this parameter, see 3GPP TS 25.331.The RNC carries the Threshold other system IE in the
measurement control message sent to the UE. This IE is used to calculate the actual value of the inter-RAT measurement
threshold. Actual value = Threshold other system - 25 [dBm], Threshold other system = GUI value - 116.
U2L RSRQ Threshold with Only
Signaling
SigTargetRatThdRSRQ
Reference signal received quality (RSRQ) threshold for reporting event 3C during LTE measurement control for non-
coverage-triggered UMTS-to-LTE redirection with only signaling connections. If the RSRQ of an LTE cell reaches this
threshold, the UE reports event 3C. If the RSRQ of an LTE cell falls below this threshold, the UE does not report event 3C.
For details about this parameter, see 3GPP TS 25.331.The RNC carries the Threshold other system IE in the
measurement control message sent to the UE. This IE is used to calculate the actual value of the inter-RAT measurement
threshold. Actual value = Threshold other system - 25 [dBm], Threshold other system = GUI value - 40.

RIM Based UMTS Target Cell Selection for LTE
Motivation
• eNodeB does not consider the load status of the target UMTS cell during a circuit switched fallback
(CSFB) to the UMTS network. If the target UMTS cell is congested, the UE may fail to access the
UMTS network.
• eNodeB does not consider the load status of the target UMTS cell during a load-based handover from
LTE to UMTS.
• it leads to handover preparation failures, increases the signaling load, and may also increase
the possibility that handovers are not performed in time
Solution: RIM Based UMTS Target Cell Selection for LTE feature
• the load status of the target UMTS cells to the eNodeB is reported through the RAN information
management (RIM) procedure during a CSFB or load-based handover from LTE to UMTS
• during a CSFB, the eNodeB preferentially selects a non-overloaded UMTS cell as the target cell.
• during a load-based handover from LTE to UMTS, the eNodeB preferentially selects a UMTS
cell that is neither congested nor overloaded as the target cell.

RIM Procedure
The RIM procedure supports two information exchange modes: Single Report and Multiple Report.
• Single Report
• In Single Report mode, the source sends a request, and then the target responds with a single report. In this
feature, the source is the eNodeB, and the target is the RNC.
• Multiple Report
• In Multiple Report mode, the target responds with a report upon receiving the initial request from the source
and sends a report to the source each time the load status changes.
During a CSFB or load-based handover from LTE to UMTS, the RIM procedure uses the Multiple Report mode to
report the load status of target UMTS cells.

RIM 3G Parameter & RNC Procedure
Huawei RNC reports the load status of target UMTS cells to the eNodeB through the RIM procedure in Multiple
Report mode. The RIM procedure is enabled on the RNC side only when
INTERRAT_LOAD_REPORT_FOR_LTE_SWITCH under the PROCESSSWITCH parameter in the SET
URRCTRLSWITCH command is selected.
RIM procedure on the RNC side:
1. The RNC receives a RAN Information Request message.
• The RNC determines whether to use the Multiple Report mode based on the value of the PDU Type
Extension IE in the RIM PDU Indications IE.
• The RNC checks whether the message requests the reporting of the load status of UMTS cells based on
the value of the RIM Application Identity IE. When the value is SON Transfer, the RNC should report the
load status of UMTS cells.
2. The RNC reports the load status of UMTS cells to the eNodeB through the RIM message. The Overload Flag IE
in the message carries the load status information. The RNC sets this IE based on the following rules:
• When the UMTS cell is in normal state, the RIM message does not carry the Overload Flag IE.
• When the UMTS cell is in Overload Control (OLC) state, the RNC sets the IE to overload.
• When the UMTS cell is in load reshuffling (LDR) state, the value of the IE is congestion.
3. When the load status of the UMTS cell changes, the RNC notifies the eNodeB of the new load status through
the RIM procedure.
Note: Huawei has extended the value range of the Overload Flag IE. According to 3GPP protocols, this IE has
only one value (overload). Huawei adds another value (congestion) for the IE.

 Introduction
 CSFB and SRVCC
Content

CSFB and SRVCC procedures
• Single Radio Voice Call Continuity (SRVCC) from LTE to WCDMA  coverage driven
• Service continuity of LTE VoIP in WCDMA CS domain
• Multi-RABs supported
• Existing WCDMA coverage can be used for LTE voice call continuation
• CS Fallback from LTE to WCDMA – service (setup) driven
• Terminal is handed over to WCDMA for speech call establishment
• RAB for CS voice is set up in the WCDMA layer after inter-system handover
• CS Fallback allows LTE deployment as a data only network
LTE
WCDMA
CSFB
CS call
VoIP call
CS call
SRVCC

CSFB – Overview
CSFB: incoming call:
The user is in LTE data connection.
The LTE network pages the LTE user.
The device responds with a special „Service
Request” message to the network, then network
signals the device to move = fallback to 2G/3G to
accept the incoming call.
CSFB: outgoing call:
The device sends the same „Service Request”
message to the LTE network, then network signals
the device to fallback to 2G/3G to make a call.

CSFB – Process
When a UE on an LTE network initiates a CS service, the CSFB feature migrates the UE to a UMTS network so
that the UE can perform the CS service on the UMTS network.
As specified in the 3GPP protocol, an LTE-to-UMTS CSFB can be performed through either a redirection or PS
handover:
• During an LTE-to-UMTS CSFB through a redirection, the eNodeB sends an RRC CONNECTION RELEASE
message carrying the UARFCN of a UMTS cell to the UE. The UE accesses the UMTS cell based on the
UARFCN and initiates a voice service again in the UMTS cell.
• During an LTE-to-UMTS CSFB through a PS handover, the RNC receives a PS handover request and
determines whether to reserve resources and admit the UE. If resources are reserved and the UE is admitted
successfully, the eNodeB sends a handover command to the UE.
After accessing the UMTS network, the UE initiates a voice service again on the UMTS network.
The CSFB process is optimized in the following aspects:
• The CSFB guarantee function is introduced for LTE emergency calls and normal calls on the UMTS side. By
reducing the rate of PS services or allowing resource preemption, this function reserves resources and
ensures successful access for PS handovers, improving the call success rate.
• A series of CSFB delay reduction measures are introduced on the UMTS side to solve problems of
postponed voice service access and poor user experience, which is caused by procedures of access,
handover, and redirection on the LTE side.

UMTS-to-LTE Fast Return
MO: UCELLHOCOMM FastReturnToLTESwitch Bit Field Type
Value range: PERFENH_PS_FAST_RETURN_LTE_SWITCH~0, HO_UMTS_TO_LTE_FAST_RETURN_SWITCH~1,
HO_SRVCC_FAST_RETURN_TO_LTE_SWITCH~2, HO_CSFB_BASED_MEAS_FAST_RETURN_SWITCH~3,
HO_CSFB_BASED_RSCP_FAST_RETURN_SWITCH~4, HO_CSFB_BASED_GRID_FAST_RETURN_SWITCH~5
Default value: PERFENH_PS_FAST_RETURN_LTE_SWITCH:0, HO_UMTS_TO_LTE_FAST_RETURN_SWITCH:0,
HO_SRVCC_FAST_RETURN_TO_LTE_SWITCH:0, HO_CSFB_BASED_MEAS_FAST_RETURN_SWITCH:0,
HO_CSFB_BASED_RSCP_FAST_RETURN_SWITCH:0, HO_CSFB_BASED_GRID_FAST_RETURN_SWITCH:0
MO: UCELLHOCOMM FastReturnToLTESwitch Bit Field Type
Value range: PERFENH_PS_FAST_RETURN_LTE_SWITCH~0, HO_UMTS_TO_LTE_FAST_RETURN_SWITCH~1,
HO_SRVCC_FAST_RETURN_TO_LTE_SWITCH~2, HO_CSFB_BASED_MEAS_FAST_RETURN_SWITCH~3,
HO_CSFB_BASED_RSCP_FAST_RETURN_SWITCH~4, HO_CSFB_BASED_GRID_FAST_RETURN_SWITCH~5
Default value: PERFENH_PS_FAST_RETURN_LTE_SWITCH:0, HO_UMTS_TO_LTE_FAST_RETURN_SWITCH:0,
HO_SRVCC_FAST_RETURN_TO_LTE_SWITCH:0, HO_CSFB_BASED_MEAS_FAST_RETURN_SWITCH:0,
HO_CSFB_BASED_RSCP_FAST_RETURN_SWITCH:0, HO_CSFB_BASED_GRID_FAST_RETURN_SWITCH:0
This feature incorporates the following functions:
• UMTS-to-LTE Fast Return
• Enhanced UMTS-to-LTE Fast Return
UMTS-to-LTE Fast Return:
• At the cell level, this function is controlled by the HO_UMTS_TO_LTE_FAST_RETURN_SWITCH under the FastReturnToLTESwitch
parameter in the MOD UCELLHOCOMM command.
• At the RNC level, this function is controlled by the HO_UMTS_TO_LTE_FAST_RETURN_SWITCH under the HoSwitch parameter in
the SET UCORRMALGOSWITCH command. When this function is configured at both the RNC and cell levels, the cell-level
configuration takes effect.
Procedure:
1. The RNC first determines that a UMTS/LTE UE is a CSFB UE if the UE meets either of the following conditions:
• When the UE is moving from an LTE cell to a UMTS cell through a PS handover, the RELOCATION REQUEST message
contains a "cause" information element (IE) whose value is "CS Fallback triggered (268)" or a "CSFB Information" IE whose
value is "CSFB" or "CSFB High Priority."
• When the UE is moving from an LTE cell to a UMTS cell through a redirection, the RRC CONNECTION REQUEST message
does not contain the "Pre-redirection info“ IE. The first service that the UE processes after accessing the UMTS cell is a CS
service
2. After the UE is identified as a CSFB UE and the UE finishes all services in the UMTS cell, the RNC triggers the RRC connection
release procedure.
3. The RNC includes the information about the neighboring LTE cells whose frequencies have higher absolute priorities than the
frequency of the UMTS cell in an RRC CONNECTION RELEASE message. Upon receiving the message, the UE selects a target cell
based on the information and attempts to camp on this cell.

Enhanced UMTS-to-LTE Fast Return
Enhanced UMTS-to-LTE Fast Return parameters
• At the cell level, this function is controlled by the PERFENH_PS_FAST_RETURN_LTE_SWITCH under the FastReturnToLTESwitch
parameter in the ADD UCELLHOCOMM command.
• At the RNC level, this function is controlled by the PERFENH_PS_FAST_RETURN_LTE_SWITCH under the PerfEnhanceSwitch3
parameter in the SET UCORRMPARA command. When this function is configured at both the RNC and cell levels, the cell-level
configuration takes effect.
The RNC first determines that a UMTS/LTE UE is a CSFB UE if the UE meets any of the following conditions:
• When the UE is moving from an LTE cell to a UMTS cell through a PS handover, the RELOCATION REQUEST message contains a
"cause" IE whose value is "CS Fallback triggered (268)" or a "CSFB Information" IE whose value is "CSFB" or "CSFB High
Priority."
• When the UE is moving from an LTE cell to a UMTS cell through a redirection, the RRC CONNECTION REQUEST message does
not contain a "Pre-redirection info" IE. After the RNC receives an RRC Connection Setup Complete message, the UE successfully
sets up a CS service within 10 seconds.
• When the UE is moving from an LTE cell to a UMTS cell through a redirection, the RRC CONNECTION REQUEST message
contains a "CSFB Indication" IE.
• After the UE finishes the CS service in a UMTS cell, an IU RELEASE COMMAND message from the CN to the RNC contains an
"End Of CSFB" IE.
After the UE is identified as a CSFB UE and the UE finishes the CS service in the UMTS cell, the RNC triggers the RRC connection
release procedure. The RNC includes the information about the neighboring LTE cells whose frequencies have higher absolute priorities
than the frequency of the UMTS cell in an RRC CONNECTION RELEASE message. Upon receiving the message, the UE selects a
suitable LTE cell based on the information and attempts to camp on this cell.

CS Fallback Guarantee for LTE Emergency Calls
For CSFB for an emergency call:
• If the UE is to fall back to the UMTS network by using the LTE-to-UMTS PS redirection, the LTE network will send an RRC connection
release message to the UE and the UE reinitiates an emergency call on the UMTS network. CSFB should be successful once the UE
has accessed the UMTS network. The feature WRFD-021104 Emergency Call ensures that emergency calls are granted access to the
UMTS network before other call types.
• If a UE is to fall back to the UMTS network by using the LTE-to-UMTS PS handover, the RNC performs resource reservation and
service admission for the PS service of the UE. Then the eNodeB instructs the UE to perform an inter-RAT handover for UMTS network
access. After falling back to the UMTS network, the UE re-initiates an emergency call.
CSFB should be successful once resource reservation and service admission are successful for the PS service on the RNC. The feature
WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls ensures that resource reservation and service admission are successful
for PS services, by decreasing the PS service rate, performing resource preemption, or both.
The HO_L2U_EMGCall_Switch field has been added to the HoSwitch parameter in the SET UCORRMALGOSwitch command. The feature
WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls is enabled when this switch is turned on.
MO: UCORRMALGOSwitch HoSwitch Bit Field Type (from Bit 1 to Bit 31)
….
Bit 28. HO_L2U_EMGCALL_SWITCH set to 1  Function switch of the CS Fallback Guarantee for LTE Emergency Calls feature. When
this switch is turned on, this feature is activated. When a UE is making an emergency call in an LTE cell, the UE is instructed to move to
a UMTS cell and the UMTS cell preferentially guarantees the successful access of the UE. If the UE is processing non-real-time PS
services, the channel types and initial data rates for these services are determined by the "NRTInitRateforL2U" parameter in the "SET
UFRC" command during service admission. If the UE is processing real-time PS services, the original channel types and data rates of
these services are retained during service admission. When this switch is turned off, this feature is not activated. When a UE is making
an emergency call in an LTE cell, the UE is instructed to move to a UMTS cell but the UMTS cell does not preferentially guarantee the
successful access of the UE. If the UE is processing PS services, the original channel types and data rates of these services are
retained during service admission.
MO: UCORRMALGOSwitch HoSwitch Bit Field Type (from Bit 1 to Bit 31)
….
Bit 28. HO_L2U_EMGCALL_SWITCH set to 1  Function switch of the CS Fallback Guarantee for LTE Emergency Calls feature. When
this switch is turned on, this feature is activated. When a UE is making an emergency call in an LTE cell, the UE is instructed to move to
a UMTS cell and the UMTS cell preferentially guarantees the successful access of the UE. If the UE is processing non-real-time PS
services, the channel types and initial data rates for these services are determined by the "NRTInitRateforL2U" parameter in the "SET
UFRC" command during service admission. If the UE is processing real-time PS services, the original channel types and data rates of
these services are retained during service admission. When this switch is turned off, this feature is not activated. When a UE is making
an emergency call in an LTE cell, the UE is instructed to move to a UMTS cell but the UMTS cell does not preferentially guarantee the
successful access of the UE. If the UE is processing PS services, the original channel types and data rates of these services are
retained during service admission.
MO: UFRC NRTInitRateforL2U (Initial Rate Type for Income L2U HO of NRT Service)
OFF, DCH0K, DCH8K, DCH8KHSDPA; DCH8K
MO: UFRC NRTInitRateforL2U (Initial Rate Type for Income L2U HO of NRT Service)
OFF, DCH0K, DCH8K, DCH8KHSDPA; DCH8K

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