Traffic Steering
WCDMA-LTE
Overview of Mobility Funtions
WCDMA Evolution
Maximize
capacity
HS Capacity Increase
Flow of users
Cater for “4G data apps”
on 3G network
Optimize for
LTE
PS HO to LTE
Release with ReDirect
Spectrum sharing
Accelerate 4G Migration
Best end-user performance
Future Proof
Network
Controller evolution
WCDMA on new Baseband and Radios
Energy Efficiency
Automation
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 2 of 31
Secure efficient operation with less
effort2030
LTE mobility in WCDMA
LTE Mobility
WCDMA
Maximize traffic on LTE
LTE users camping on
with WCDMA
WCDMA
LTE Mobility Solutions in WCDMA
Subscriber Handling
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 3 of 31
LTE
Offload
High load in LTE
Coverage
No LTE coverage
Subscription Based
No 4G subscription
CS Fallback
VoLTE not available
LTE Mobility Solutions in WCDMA
Packet Switched Handover to LTE
•
•
•
Possible to use with Coverage Check and LTE Measurements
Good end-user experience – seamless transition
Coverage measured and secured
Seamless handover
Maximize use of LTE
investment
Best end-user experience
Release with Redirect to LTE – UE measurements
PS pre-empted
•
•
•
•
Possible to use with Coverage Check and LTE Measurements
Many triggers available
Easy to deploy
Coverage measured and secured
Release with Redirect to LTE – no UE measurements
Enable re-farming of 3G
frequencies
•
•
•
Blind release at state transition
Applicable in areas with good LTE coverage
Fast return for CS Fallback users
No ongoing PS transfer
Cell reselection
•
•
•
SIB19 broadcast
Dedicated Priorities
Reselection possible from FACH, URA or IDLE
PS inactive or idle
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Subscriber Handling
Service-Based Mobility to LTE
•
Received information from Core Network indicates if user is allowed LTE mobility
in connected mode
Requires CN configuration
Subscriber Based Mobility Using SPID
CN
•
•
•
SPID configuration done in Core Network
Received information from Core Network indicates if user is allowed LTE mobility
LTE cell re-selection with dedicated priorities
User Profile Based Mobility
•
•
•
•
RAN stand-alone configuration
User profiles groups defined in RNC
Groups are based on IMSI series or CN operator
Shared and non-shared networks support
LTE cell re-selection with dedicated priorities
UE-Selective Relocation to LTE
RNC
•
•
•
•
RNC monitors success rate of UE returning to WCDMA after LTE mobility attempt
User without subscription are blocked
Configurable timers
Easy to deploy
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 5 of 31
4G UEs traffic in 3G
– Basic principles
A UE is intended to camp
and be connected in the
RAT according to the
highest UE capability.
The WCDMA network will
always look for the
opportunity to guide the
LTE capable UE back to
higher priority LTE from
WCDMA when there is
LTE coverage available
— LTE providing higher
bitrates for Mobile
Broadband
— Maximize VoLTE
usage
LTE
Reselect
to LTE
(higher
priority)
Release
with
redirect to
LTE
Reselect
to WCDMA
(lower priority)
PSHO
Idle mode
CS
fallback
to
WCDMA
WCDMA
The level of data traffic on
3G is dependent on:
— 4G UE penetration
— 4G UEs capability of
VoLTE
— 4G band and coverage
compared to 3G
Off load
Coveragetriggered
PSHO/SRVC
C to WCDMA
CS fallback & Return
Connected Mode
(load-triggered)
Connected Mode
(coverage-triggered)
There are basically four different reasons for an 4G
capable UE to be in 3G coverage.
— CS Fallback: VoLTE (speech) service not available
in LTE RAN or UE
— Offload: due to high load in LTE, UE is moved to 3G
— Coverage: No 4G coverage available
— Subscriber management: Lack of 4G subscription
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 6 of 31
Supporting Value Packages
Traffic Management
WCDMA-LTE
FAJ 121 1474 LTE Cell Re-selection
FAJ 121 2174 Release with re-direct to LTE
Traffic Management Advanced
WCDMA-LTE
FAJ 121 1611
FAJ 121 3427
FAJ 121 3588
FAJ 121 3637
FAJ 121 3520
FAJ 121 3963
FAJ 121 3960
FAJ 121 4721
FAJ 121 3519
FAJ 121 4277
FAJ 121 4928
FAJ 121 5184
FAJ 121 5216
FAJ 121 5267
Packet Switched Handover from LTE
IRAT Offload from LTE
LTE Cell Reselection Dedicated Priorities
Subscriber Based Mobility using SPID
Cell Reselection to LTE in cell-FACH
LTE cell reselection for Advanced LTE deployments
Release with re-direct to LTE based on coverage check
Packet Switched Handover to LTE
PS handover to LTE based on measurements in LTE
Release with Redirect to LTE Based on Measurements in LTE
Service Based Mobility to LTE
User Profile Based Mobility
Preferred mobility at CS fallback return to LTE
UE-Selective Relocation to LTE
Traffic Managaement CS
Fallback
FAJ 121 1610
FAJ 121 2179
FAJ 121 4250
FAJ 121 4365
CS voice fallback from LTE
RIM Support for System Information Transfer to LTE
CS Priority at CS Fallback from LTE
CS Fallback based on PS Handover
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 7 of 31
Mobility to LTE - WCDMA features and
enhancements up to W22.Q2
W21.Q4: Periodic trigger for
LTE measurements
W19.Q4: PSHO LTE
measurement enhancement
● Using defined LTE neighbors
of all cells in Active Set for
handover
● Results in more PSHO to LTE
W20.Q3: Preferred mobility
at CS fallback return to LTE
W20.Q4: UE-Selective
Relocation to LTE
● Flexible handling of CS
fallback users
● Temporarily block LTE
users without
subscription
● LTE measurement can be
re-started in a periodic
manner if no valid cell or
frequency was found
during previous
measurement
● RAN stand-alone
feature
● Increase probability of
PSHO or RWR
● Set preferred LTE
mobility method
W19.Q4
W20.Q1
W20.Q2
W20.Q3
W20.Q4
W21.Q1
W21.Q2
W21.Q3
● Facilitate identification of
valid LTE neighbors
● Increase number of
PSHO to LTE
● Reduce time spent on
defining and maintaining
LTE neighbors
W21.Q4
W20.Q2: PSHO LTE
measurement enhancement
W20.Q4: PSHO/RWR LTE
measurement enhancement
W21.Q1: User Profile Based
Mobility
W21.Q4: LTE Measurement
Enhancement
• Combining Coverage Check
and LTE measurement as
triggers for PSHO to LTE
● Prolong DCH state when
LTE measurements are
started
● Allow/prohibit user
groups access to LTE
frequencies
• Measurements Started
More Efficiently for
csFallback Users
● More PSHO to LTE
● More efficient use of
compressed mode
● Groups defined by IMSI
series or CN operator
● Less usage of compressed
mode
W22.Q2: Future: Simplified
definition of WCDMA to LTE
neighbor relations
...
W22.Q2
Future: PSHO/RWR
LTE measurements
enhancement
● Avoid compressed
mode for short PS
sessions
● Increase probability of
PSHO or RWR
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 8 of 31
Released SW
PRM
...
PRT
Candidate
Mobility to LTE - WCDMA features and
enhancements up to W22.Q2
W21.Q4: Periodic trigger for
LTE measurements
W19.Q4: PSHO LTE
measurement enhancement
● Using defined LTE neighbors
of all cells in Active Set for
handover
● Results in more PSHO to LTE
W20.Q3: Preferred mobility
at CS fallback return to LTE
W20.Q4: UE-Selective
Relocation to LTE
● Flexible handling of CS
fallback users
● Temporarily block LTE
users without
subscription
● LTE measurement can be
re-started in a periodic
manner if no valid cell or
frequency was found
during previous
measurement
● RAN stand-alone
feature
● Increase probability of
PSHO or RWR
● Set preferred LTE
mobility method
W19.Q4
W20.Q1
W20.Q2
W20.Q3
W20.Q4
W21.Q1
W21.Q2
W21.Q3
● Facilitate identification of
valid LTE neighbors
● Increase number of
PSHO to LTE
● Reduce time spent on
defining and maintaining
LTE neighbors
W21.Q4
W20.Q2: PSHO LTE
measurement enhancement
W20.Q4: PSHO/RWR LTE
measurement enhancement
W21.Q1: User Profile Based
Mobility
W21.Q4: LTE Measurement
Enhancement
• Combining Coverage Check
and LTE measurement as
triggers for PSHO to LTE
● Prolong DCH state when
LTE measurements are
started
● Allow/prohibit user
groups access to LTE
frequencies
• Measurements Started
More Efficiently for
csFallback Users
● More PSHO to LTE
● More efficient use of
compressed mode
● Groups defined by IMSI
series or CN operator
● Less usage of compressed
mode
W22.Q2: Future: Simplified
definition of WCDMA to LTE
neighbor relations
...
W22.Q2
Future: PSHO/RWR
LTE measurements
enhancement
● Avoid compressed
mode for short PS
sessions
● Increase probability of
PSHO or RWR
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 9 of 31
Released SW
PRM
...
PRT
Candidate
W19.Q4: Handover to LTE using all cells in Active Set
TrafficManagementAdvancedWCDMA-LTE (FAJ801 0314), PS HandovertoLTEbasedonMeasurementsinLTE(FAJ121 3519)
Background
● LTE coverage measurement is received in RNC, but the
reported cells are sometimes unknown LTE neighbors.
Description
● To find neighbor relation for LTE more often, neighbors of all
cells in Active Set are considered for PS handover to LTE.
Benefits
● Reducing the impact on handover, due to missing
configuration of LTE neighbors
● Better end user throughput performance by increased
mobility to LTE
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 10 of 31
Cell 1
Neighbor
Relation not
defined
Cell A
Neighbor
Relation
defined
Cell B
Red color: WCDMA cells
Blue color: LTE cells
W20.Q2: PSHO based on both Coverage Check and LTE Measurements
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
PS Handover to LTE based on Measurementsin LTE, FAJ 121 3519 R6
Background
● In co-sited cells the Compressed Mode based LTE
measurements are used and coverage check information is
ignored.
Description
● PSHO to LTE (FAJ 121 4721) and PSHO to LTE based on
measurements in LTE (FAJ 121 3519) are both taken into
consideration.
● LTE measurements are only used when the coverage check
cannot result in PSHO to LTE.
Benefits
– Reduced usage of Compressed Mode.
– Earlier triggering of PSHO to LTE, allowing PSHO even for
UEs with short PS sessions.
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 11 of 31
EutranCellRelation
Cell 1 (Co-sited)
EutranCellRelation
Cell 2
(Co-sited)
Cell B
Cell A
Purple color: WCDMA cells (A and B)
Green color: LTE cells (1 and 2)
LTE and WCDMA cells co-sited with defined coverage
relations.
The dotted ellipses showing the event 2f-RWR threshold with
dark purple parts, where PSHO based on Coverage Check is
possible, while in light purple parts PSHO needs and will use
LTE measurements.
In dark purple parts, where the LTE coverage is very certain,
PSHO to LTE is done based on Coverage check.
In light purple parts, where the LTE coverage is not so certain,
the PSHO will be done based on measurements in LTE.
W20.Q3: Preferred mobility at CS fallback return to LTE
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
Preferred Mobilityat CS Fallback Return to LTE, FAJ 121 5216 R1
CS Fallback
Background
– Different options exist to push a CS fallback user
back to LTE after completed CS call
Packet Switched Handover:
—
LTE measurements
—
Coverage Check
LTE
– The choice of method is prioritized in a fixed
order
Description
– Faster return to LTE when in known LTE
coverage
Average attempts per hour
– Flexibility for operators to set preferred
method to re-direct or handover CS fallback
users to LTE
WCDMA
Release with re-direct:
—
Blind
– The operator can configure which feature
should take precedence at CS call release
Benefits
Release with re-direct:
—
Coverage Check
—
LTE measurements
Usage of mobility features
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
PS HO to LTE
Feature OFF
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 12 of 31
RWR CC
Feature ON
RWR
W20.Q4: UE-Selective Relocation to LTE
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
UE-SelectiveRelocation to LTE, FAJ121 5267 R1
Background
X
● WRAN should minimize the volume of futile Release with Redirect (RwR) or PS
Handover to LTE (PSHO) attempts for UEs without LTE subscription.
● Existing features: Subscriber Based Mobility Using SPID and Service-Based Mobility
to LTE use indication from Core Network (CN) that specific subscriber should not be
relocated to LTE. These features require support in CN, which is not always available,
and their flexibility is limited.
RNC
eNB
NB
1. initial mobility to LTE attempt
Description
● Initial UE mobility to LTE attempts via RwR and PSHO are monitored by the RNC
● A UE without LTE subscription is expected to return to WCDMA within a short time
● Basing on the subsequent UE behavior, the RNC decides if further RwR and PSHO to
LTE attempts shall be allowed for the specific subscriber for a configurable amount of
time
Benefits
● Limits the side effects of enabling RwR and PSHO to LTE features in networks with
significant number of WCDMA-only subscribers
● This solution does not depend on Core Network support
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3. Quick return to WCDMA
UE A
UE A
W20.Q4: LTE Measurement Enhancement -Prolong duration of CELL_DCH state
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
PS Handover to LTE based on Measurementsin LTE, FAJ 121 3519
Background
● Legacy Channel Switching functionality does not consider ongoing LTE
measurement when deciding about leaving CELL_DCH state
● LTE measurement is terminated at down-switching
Description
● When LTE measurement is ongoing the triggers for down-switching from
CELL_DCH state are postponed
● The prolonged period in Cell_DCH state is controlled with a configurable
timer
● The timer is started along with the ordered LTE measurement
Benefits
● Increased probability of Measurement Report reception when LTE
measurements are started
● Increased mobility to LTE and improved end-user experience
● Reduced overall usage of radio resources in WCDMA
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 14 of 31
Payload
PS Handover to LTE
LTE measurements ongoing
PS session
User
inactivity
time
W21.Q1: User Profile Based Mobility Enhancement
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
User profile based mobility, FAJ 121 5184 R2
Background
– There is a need to control mobility of UEs from WCDMA to LTE in
a Shared RAN
– Priority of frequencies for redirection and cell reselection to LTE
can be set independently for a group of users defined by IMSI or
CN operator handling the connection
Description
– Priority of frequencies for PS handover to LTE can be set
independently for each group of users
LTE Frequency 1
LTE Frequency 2
– Support for shared network features
– Support for non-shared networks
Benefits
– The feature enables the operator to steer groups of subscribers
identified by IMSI to selected LTE frequencies, in order to meet the
operator’s subscriber mobility strategy
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 15 of 31
WCDMA
IMSI#1
IMSI#2
IMSI#3
W21.Q4: LTE Measurement Enhancement –Periodic Measurement Trigger
Description
● LTE measurement can be re-started in a periodic manner if no valid cell or
frequency was found during previous measurement
● Periodic LTE measurements are started immediately after configurable timer
expiry or at next upswitch to DCH state
Benefits
● Better WCDMA resource usage due to users moving to LTE
● Better end-user experience
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 16 of 31
PS Handover to LTE
FACH -> DCH
DCH -> FACH
● The LTE measurement start triggers due to best cell change, or CS call release, has
no effect if the UE is temporarily down-switched to FACH or URA during a long PS
session
FACH -> DCH
● If no valid LTE cell is found during an LTE measurement period, there is a risk that
the UE does not get further opportunities to measure LTE coverage
Example UE session
DCH -> FACH
Background
RRC & PS RAB setup
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
PS Handover to LTE based on Measurementsin LTE, FAJ 121 3519
Release with Redirect to LTE Based on Measurementsin LTE, FAJ 121 4277
UE session time
Legacy
trigger
Periodic
trigger
Timer expiry
for periodic
trigger
Periodic trigger
moved to the next
upswitch
Time on DCH -> chance for legacy LTE measurement trigger
Time on Common Channel -> no chance for LTE measurements
LTE measurements trigger
W21.Q4: LTE Measurement Enhancement – Measurements Started
More Efficiently for csFallback Users
Background
● CS call release during an active PS session is a trigger to start LTE measurements.
Initial Direct Transfer
received
Without enhancement
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
PS Handover to LTE based on Measurementsin LTE, FAJ 121 3519 R8
CM
start time
● When CSFB call is released and PS session is active, LTE measurements are started
only at the end of the LAU procedure.
Benefits
● Reduced usage of Compressed Mode
● Increased probability of Measurement Report reception when LTE measurements are
started
● Speed up of mobility to LTE in relation to CS fallback release case
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With enhancement
Description
CM
start time
LAU time
LAU time
LTE
measurements
ongoing
time
Initial Direct Transfer
received
● The vast majority of CSFB call releases is followed by the LAU procedure.
● LTE measurements already started by the above trigger are terminated due to conflict
with the LAU procedure.
CM stop
time
CM
start time
LTE measurements
ongoing
time
Activation period
%
%
W22.Q2 Simplified Definition of WCDMA to LTE Neighbor Relations
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
Simplified Definition of WCDMA to LTE Neighbor Relations, New
Background
● Correct LTE neighbor definition is a pre-requisite for successfully deploying PS
handover to LTE based on measurements in LTE
Neighbor cell relation
- WRAN created
● Defining the correct set of LTE neighbors for each WCDMA cell is time consuming
and cumbersome
LTE cell definition in WRAN
- Operator created
LTE cell
Description
Cell relation
● Based on existing configuration in the WRAN, the RNC can automatically identify,
create and maintain missing LTE neighbor relations
Benefits
● Reduce time spent on defining and maintaining correct LTE neighbor relations
● Increased number of handovers to LTE
● Better WCDMA resource usage due to users moving to LTE
● Better end-user experience
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 18 of 31
WCDMA cell
WCDMA cell
Future: LTE Measurement Enhancement - Delay Start of LTE Measurements
Background
— Majority of the PS sessions are shorter than the time that is needed to
start Compressed Mode and measure and report LTE neighbor cells
— LTE measurements are started and stopped during short PS session
where there is no chance for the UE to send a valid measurement report
Description
— LTE measurement will not be started until the PS session has been active
for a pre-defined time
Benefits
— Increased probability of the number of Compressed Mode Starts resulting
in a measurement report e3c
— Better resource usage and end user throughput performance by more
efficient usage of compressed mode for LTE measurements
| QKRAMAR Marcin Krawiec | BNEWIQGB [Marcin Krawiec] | 17/221 09-FGC 101 3355 Uen | A | 2021-10-12 | Ericsson Internal | Page 19 of 31
CDF of PS Sessions length %
Traffic Management Advanced WCDMA-LTE, FAJ 801 0314
PS Handover to LTE based on Measurements in LTE, FAJ 121 3519
100
Time needed
for LTE meas.
Measurements
started
Duration of PS session
Delay LTE meas.
Guidelines
● CPI: Inter-Radio Access Technology (WCDMA)
● CPI: LTE Mobility and Traffic Management Guideline
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