Mobility features: RAN2717
RAN2980: Measurement Based LTE Layering RAN3069: RSRQ-based LTE Reselection RAN2264: Smart LTE Handover RAN2881: WCDMA and GSM Layer Priorities
Introduction
WCDMA - LTE Interworking overview
Cell_DCH
RRC_CONNECTED
Cell_FACH Cell_PCH
URA_PCH
RRC_IDLE
UTRA_IDLE
Handover
Redirection
Reselection
RAN2980: Measurement Based LTE Layering RAN2717 RAN3069: RSRQ-based LTE Reselection RAN2264: Smart LTE Handover RAN2881: WCDMA and GSM Layer Priorities
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Introduction RAN2980 Measurement Based LTE Layering
RAN2980 Measurement Based LTE Layering Description: • Feature allows for redirection from WCDMA to LTE UE’s with active
Packet Switched services or those which are moving from Cell_DCH to other Connected RRC states. RAN2980/2717
• Redirections are preceded by measurements of LTE frequencies. • UE with PS RABs in Cell_DCH are redirected to LTE Idle Mode,
where they are camping on LTE cell. Benefits: • Measurements before redirection highly increase chances for
successful UE camping on LTE Layer • Shorter camping period on LTE cell provides better end-user experience • Feature can also be used when WCDMA and LTE coverage don’t
overlap and sites are not co-located
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Cell_DCH
RRC_IDLE
Introduction: Evolution of WCDMA – LTE Interworking RAN2980 Measurement Based LTE Layering RAN2067 LTE Interworking (RU20 On TOP)
RAN 2717 Smart LTE Layering (RU40)
Cell Reselection also for LTE Layers is introduced
Redirection to LTE is possible with active PS services
Redirection to LTE based on measured LTE frequencies
NO POSSIBILITY for moving UEs with active PS services to LTE • Absolute priorities for layer selection introduced in
Problems appear in case of non-overlaping WCDMA/LTE coverage
• Redirection is based on measurements of LTE RSRP and
• There is a possibility to redirect active UEs from WCDMA
• There is a possibility to redirect UEs with active PS data
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
WCDMA Coverage
LTE Coverage
Smartphones often stay in a connected mode due to some traffic demanding services, this is very resource consuming. Always in WCDMA if active
to LTE
• While 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.
• CPICH RSCP threshold (SmartLTELayeringRSCP) is used to “ensure” the presence of LTE coverage (i.e in collocated WCDMA and LTE scenarios) but must be set manually Smart LTE Layering decrease impact of cell congestions. The best scenario is when LTE and WCDMA coverage overlaps Redirected to LTE
Problem appears when there is no coverage and theoretically should be, this may cause “ping-pong effect”
RSRQ. transmission, from RRC LTEPeriodicTriggerTimer.
Cell
DCH
to
LTE
using
• If UE is in a “black spot” of LTE coverage, it is not redirected • Feature decrease UE camping time on LTE layers and prevents from “ping-pong” effect.
• There is a possibility to configure many scenarios with different trigger combinations for blind or measurement based layering on a cell level
UEs make measurements on LTE frequencies. RRM decides about redirection
Trying move to LTE Redirected to LTE
RSCP threshold
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RAN2980 Measurement Based LTE Layering (RU50)
I stay in WCDMA
Introduction RAN2980 Measurement Based LTE Layering
• Measurement Based LTE Layering is an extension of Smart LTE Layering
RAN 2980 RAN 2717
• New trigger • More parameters • More options
• In RAN2717 UE move to LTE is blind, i.e. no frequencies measurements preceding redirection to LTE • recommended for scenarios with co-located WCDMA NodeB/LTE eNodeB sites or sites with shared antenna systems.
Cell DCH
No measurements
RRC Idle
• In RAN2980, before redirection from WCDMA to LTE, compressed mode measurements are used to determine if LTE coverage is available • recommended for scenarios with co-located and not co-located LTE and WCDMA sites.
Cell DCH
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With or without measurements
RRC Idle
Benefits and Gains RAN2980 Measurement Based LTE Layering
Before introduction of RAN2980 (with RAN2717) • In the scenario when WCDMA and LTE coverage doesn’t overlap it may happen that UE is not able to camp on any LTE cell (due to coverage) and is coming back to WCDMA after several seconds. This may create a ping-pong effect very severe for end-user experience.
• To prevent that in RAN2717 a parameter for setting CPICH RSCP value was introduced but it has to be set manually (SmartLTELayeringRSCP),
UEs in LTE UEs in WCDMA
For co-located WCDMA and LTE sites with well overlapping coverage RAN2717 can be used for redirection
If WCDMA and LTE coverage don’t overlap RAN2717 can cause problems (ping-pong effect) RSCP threshold
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Benefits and Gains RAN2980 Measurement Based LTE Layering
Before introduction of RAN2980 (with RAN2717)
Too high threshold will cause that LTE resources won’t be used and there won’t be load balance between LTE and WCDMA
SmartLTELayeringRSCP value has to be set very accurately
Problem appears when there is no coverage and theoretically should be, this may cause “ping-pong effect” Trying move to LTE Trying move to LTE
RSCP threshold
RSCP threshold
Too low threshold may cause that many “black spots” - areas without LTE coverage – will be in area where “blind” redirection is done.
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Only here allowed
redirection
is
Not used LTE resources
Benefits and Gains RAN2980 Measurement Based LTE Layering
After introduction of RAN2980:
• Compressed mode measurements are used to determine if LTE coverage is available • All BENEFITS of RAN2717 feature are also “inherited” by RAN2980. • Feature decreases time of UE camping on LTE cells. • Applicable for co- located and not collocated scenarios and for not well overlapping LTE/WCDMA coverages:
WCDMA Coverage
OR • No problems with setting RNP coverage parameters manually.
Trying move to LTE
RSCP threshold
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LTE Coverage
With RAN2980 it doesn’t matter where UE is, availability of LTE Coverage can always be checked
Benefits and Gains RAN2980 Measurement Based LTE Layering
After introduction of RAN2980: • Additional trigger for moving UE’s with long Cell_DCH reservations for PS services Periodic Trigger – timer for moving UE’s with PS Services from WCDMA to LTE
• There are many additional options which can be enabled: LTE Capable UE with active PS service in WCDMA
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•
HSDPA load check
•
Number of NRT users check
•
LTE TDD/FDD check
•
Services to be redirected check
LTE Capable UE with active PS service in LTE
Interdependecies RAN2980 Measurement Based LTE Layering
RAN2136
Feature interworking implemented
UE’s identified as “Legacy Fast Dormancy phones” are not redirected
Fast Dormancy
RAN2451 Fast Dormancy Profiling
Change from “blind” to measurement based redirection
RAN2717 SMART LTE LAYERING
RAN1668 HSUPA CM FOR LTE AND INTER-FREQUENCY HANDOVER
Support for E-DCH Compressed Mode
RAN2980
No license needed for RAN2717 if RAN2980 license is installed
Measurement based LTE Layering Interworking
RAN2067 license must be installed and feature must be activated
Recommended
RAN2067 LTE Interworking
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Mandatory
Basic
Interdependecies RAN2980 Measurement Based LTE Layering
RAN2067 LTE Interworking - mandatory •
LTE Interworking provides support for LTE cell re-selection in idle, Cell_PCH and URA_PCH states.
•
This feature provides BTS functionality for receiving SIB19 from RNC and broadcasting it over cells.
•
This feature must be ACTIVE i.e. the license must be installed and the state of the licence is “ON”
RAN1668 - recommended •
To measure LTE carrier frequency through compressed mode, transmission gap length TGL of 10 time slots with double frame method is required. Support of TGL of 10 TS with double frame method for HSUPA compressed mode is introduced in RAN1668.
•
In the absence of RAN1668, HSDPA/DCH and DCH/DCH modes are supported. If there is HSUPA in the uplink (E-DCH), then it is reconfigured to DCH, before initiating the compressed mode measurements.
RAN2717 Smart LTE Layering – basic feature With RAN2980 license there is no need to have RAN2717 license, all the functionalities are contained in RAN2980. •
Parameters used in Smart LTE Layering are also used in RAN2980 feature.
•
The layering was “blind”, i.e. no measurements were done before redirecting UE to LTE system.
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Interdependecies RAN2980 Measurement Based LTE Layering
• • • •
RAN2136 Fast Dormancy - interworking Fast Dormancy provides faster UE state change from Cell_DCH to Cell_PCH or URA_PCH. UE sends Signaling Connection Release Indication IE set to “UE Request PS Data session end” which overrides inactivity timers in RNC If the measurements are ongoing while IE is sent, measurements are finished and RRM on that basis decides about redirection If the measurements are not ongoing, they are started due to “state change trigger” and also for this case RRM makes decision about redirection based on measurements (if enabled)
RAN2451 Fast Dormancy Profiling - interworking • Fast Dormancy Profiling identifies Legacy Fast Dormancy Smartphones causing unnecessary signaling load. • These Smartphones/UEs sends RRC: Signaling Connection Release Indication WITHOUT cause value, in that case they are moved to CELL_PCH/URA_PCH states, no matters if the measurements are ongoing or they haven’t been started.
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Technical details - Triggers RAN2980 Measurement Based LTE Layering
RAN2980 use four triggers that can start the process of moving UEs to LTE, if UE is LTE capable: Triggers introduced in RAN2717
RAN2980 new trigger
First three triggers are also used in feature Smart LTE Layering. In addition to these, fourth trigger for terminals keeping long Cell_DCH reservations for PS services, was introduced
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Technical detail - Triggers RAN2980 Measurement Based LTE Layering
Triggers used for redirection can be set with WCEL- SmartLTELayeringEnabled parameter. Values of the parameter and respective trigger combinations are presented in following table:
LTELayeringMeasActivation parameter is used to define triggers for which measurements are executed. Values of the parameter and respective trigger combinations are presented in following table:
•
Measurements are done periodically, every 500ms are sent to RNC
•
As it can be seen in the table on the left, Trigger 4 is always set with measurements
•
If the measurements are not successful the redirection is not done Trigger 1 (T1): RRC State Change Cell_DCH to CCH Trigger 2 (T2): HSDPA/HSPA to DCH/DCH CTS Trigger 3 (T3): CS RAB Release Trigger 4 (T4): Periodic trigger
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Technical details – UE Capability RAN2980 Measurement Based LTE Layering In order to perform Layering from 3G towards LTE, the UE must be LTE capable. 3GPP Rel-8 capable UEs are required UE radio access capabilities for E-UTRA are sent via: • RRC: CONNECTION SETUP in Capability Update Requirement IE • UE provide radio access capabilities for E-UTRA within RRC: CONNECTION SETUP COMPLETE • RRC stores the information for the duration of UE RRC connection UE radio access capabilities provides following information: • Multi-mode/Multi-RAT capability, support for LTE FDD, TDD, frequency bands, need for compressed mode Exceptions: • UE radio access capabilities can also be received by UE specific RRC: • during incoming SRNS relocation with RRC: SRNS RELOCATION INFO • during incoming Inter-RAT handover within: INTER RAT HANDOVER INFO • Requested from UE with RRC: UE Capability Enquiry
• Majority of UEs require compressed mode to perform LTE inter-system measurements. During CM transmission gap of length of 10 time slots which spans over 2 consecutive radio frames is used to make measurements. • Compressed mode in HSPA requires RAN1668 license – If HSPA compressed mode is not available, UE is reconfigured to DCH. (e.g. HS-DSCH/E-DCH -> HSDSCH/DCH). • There could be some high end UE’s which have dual receiver and don’t require compressed mode to create gaps and listen to other frequencies.
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Technical details – Measurements (1/2) RAN2980 Measurement Based LTE Layering
•
LTE carrier frequencies used for redirection are sent over RRC: Measurement Control message and usually are the same as those broadcasted in SIB19 (please see Paremeters description)
•
UE Specific RRC configures redirection using following: • NBAP: RADIO LINK RECONFIGURATION PREPARE message: • Compressed Mode parameters • RRC: PHYSICAL CHANNEL RECONFIGURATION message which contains following information: • Compressed Mode Info • Transmission Gap Starting Slot Number • Transmission Gap length • Other Transmission Gap info.
•
If configuration fails UE/NodeB sends RRC: Physical Channel Reconfiguration Failure/ NBAP: Radio Link Reconfiguration failure messages
•
UE specific RRC activates CM in NodeB with NBAP: Radio Link Reconfiguration Commit message
•
UE specific RRC activates CM and triggers measurements in UE with RRC: MEASUREMENT CONTROL message which contains such a information as: • E-UTRA carrier frequencies list, • measurement bandwidth, • reporting mode, (measurements are sent periodically) • Measurements are reported every 500ms. • transmission gap pattern, etc.
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Technical details – Measurements (2/2) RAN2980 Measurement Based LTE Layering
• Measurement results are sent from UE via RRC in Measurement Report • LTE Reference symbol received power RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality) • If UE rejects measurement command, it sends RRC: Measurement control Failure message. UE specific RRC forwards the message to RRM which supports failure handling. • RRM – Handover Entity – compares averaged measurements results (averaging time period is defined with LTEMeasAveWindow) to thresholds., Maximum measurement period is set in LTEMaxMeasPeriod.
• RRM ranks LTE carrier frequencies according to measured RSRQ values, and put in that order to the list.)* • There is a space of maximum 8 carriers frequencies to be sent over IE “EUTRA Target Info” through RRC Connection Release.
* LTE Frequencies are placed in prioritized manner in the Redirection Info IE but 3GGP doesn’t specify on which frequency UE should start camping. It is UE specific implementation.
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Technical details RAN2980 Measurement Based LTE Layering
TIMERS (in case of T1, T2 or T3 triggers) • If trigger T1 or T2 or T3 appears, UE capability is checked together with all preconditions for redirection (see here) • LTE Maximum Measurement Period – defines maximum allowed period during which LTE measurements are performed. If the RNC is not able to redirect the UE to LTE system during this period, then RNC asks UE to stop the LTE measurements (default 6s) • LTE Minimum Measurement Interval - determines the minimum interval between Inter-RAT (LTE) measurement procedure which didn’t led to redirection and the following LTE measurement procedure related to the same RRC connection (default 5s). During that period, measurements are forbidden. Also if other trigger appear in this period, blind or with enabled measurements, it is ignored.
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Technical details RAN2980 Measurement Based LTE Layering
TIMERS (for T4 trigger – periodic trigger) • LTE Periodic Trigger Timer – starts when UE enters Cell DCH with active PS RAB, when expires, measurements are started (default 20s), if the measurements are unsuccessful, timer is started again. If any other trigger appears after LTEMinMeasInterval and it won’t lead to redirection (e.g. too low measured values), and UE still transmits PS data, timer is set again. Timer is set periodically until redirection decision is made OR UE has no data to transmit and PS RAB is released.
Timer reset
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_________
Technical details RAN2980 Measurement Based LTE Layering
During LTE Maximum Measurement Period following actions take place: • Measurement reports are sent every 500 ms (hardcoded) during LTE Maximum Measurement Period • LTE Neighbor Carrier Frequency Search Period – this parameter prevents UE redirection to LTE system, which eliminates too fast redirections based on only few measurements. • LTE Measurement Averaging Window – determines the maximum period for averaging the received periodical LTE measurement reports (maximum size of the sliding averaging window) from which the RNC calculates the averaged LTE RSRP and RSRQ
Timer reset
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Technical details – Message Flow RAN2980 Measurement Based LTE Layering
RRC State change from CELL_DCH to CCH 1. LTE capable UE is in CELL_DCH with active PS RAB, 2. Data activity stops 3. UE specific RRC starts making transition from CELL_DCH to CELL_FACH/CELL_PCH/URA_PCH Important: In case of 'state change trigger‘ (T1), and Periodic trigger (T4), UE state change (away from Cell_DCH state) shall be delayed until LTE frequency band measurements are done (opposite to CS RAB RELEASE and CTS Change). Reason is that UE dedicated resources are needed for LTE frequency band measurements. 1. RRM (Handover Control entity) triggers measurements (compressed or dual RX) 2. Measurement results from UE are compared with thresholds for minimum RSRQ received level and minimum RSRP received level 3. Measurements are ongoing until redirection decision is made or LTE Maximum Measurement Period timer expires
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Technical details RAN2980 Measurement Based LTE Layering
RRC State change from CELL_DCH to CCH 7. Measurements are successful i.e. measured RSRQ and RSRP values exceeds thresholds 8. Frequencies are prioritized by RRM Handover Entity and information of target frequencies is sent to UE through RRC Connection release 9. Connection release complete message is sent and RBs are released, 10. UE starts camping procedure on received frequencies
7. Measurements are not successful (or UE data activity restarts or CS RAB appears) 8. PS RB’s are released* 9. UE is kept in WCDMA
*not applicable in case when UE data activity restarts
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Technical details – Pre-conditions for redirection RAN2980 Measurement Based LTE Layering
Pre-Conditions for redirection to LTE system that MUST be fulfilled: •
RAN2980 feature license is in the „ON” state.
•
WCDMA Cell in which UE is, has at least one LTE neighbour
(ADJL-AdjlEARFCN) •
Trigger appears
•
UE must be LTE capable
•
Redirection is allowed only for PS services
•
Redirection must be allowed for ALL PS services the UE has.
•
No Iu procedure (e.g. Location Request) except Iu Release is ongoing
•
There is no Emergency call related activity.
•
Max number of UEs in HSDPA CM due to Non-Critical Handover is not exceeded. Set with MaxNumberUEHSPACmNCHO
•
E-UTRAN Service Handover functionality does not prevent mobility to LTE If the all above conditions are fulfilled, then UE is ordered to LTE
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Technical details – Pre-conditions for redirection RAN2980 Measurement Based LTE Layering
Pre-Conditions for redirection to LTE system that are OPTIONAL checks (parameters can be disabled):
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Deployment Aspects RAN2980 Measurement Based LTE Layering
• Exceptions – redirection with measurements is not done if one of the following appears:
** If the call establishment cause was emergency call OR the CS RAB had pre-emption capability OR if UE has had emergency positioning ongoing, then redirection to LTE is not done for the UE as long as the RRC Connection exists.
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Deployment Aspects – CM Measurements RAN2980 Measurement Based LTE Layering
• • •
Majority of UEs require compressed mode to perform LTE inter-system measurements. During CM transmission gap of length of 10 time slots which spans over 2 consecutive radio frames is used to make measurements. Compressed mode in HSPA requires RAN1668 license – If HSPA compressed mode is not available, UE is reconfigured to DCH. (e.g. HS-DSCH/EDCH -> HS-DSCH/DCH) There could be some high end UE’s which have dual receiver and don’t require compressed mode to create gaps and line to other frequencies RAN1668
RNC/WBTS
HSUPA CM FOR LTE AND INTER-FREQUENCY HANDOVER
BTS support for HSPA CM
Only DCH CM supported ==> 0 HSDPA CM supported ==> 1 HSPA CM supported ==> 2 (RAN1668 needed)
HSUPA Compressed Mode HS-DCH/E-DCH
* This implementation will be changed
Double frame gap: E-UTRA Freq. Measurements
normal radio frame
compressed radio frame
compressed radio frame
normal radio frame
Configuration Management – Parameters RAN2980 Measurement Based LTE Layering RNC/WBTS/WCEL RNC/FMCL FMCL Identifier FMCL Identifier Smart LTE Layering Enabled
•
RAN2980 feature introduces new Frequency Measurement Control LTE parameters (FMCL) which are advanced options for controlling of measurement timing processes
•
WCEL parameters are basic feature behavior parameters configured on a cell level
Change Origin for FMCL Object Measurement Based LTE Layering Activation
LTE Mesurement Averaging Window Smart LTE Layering RSCP threshold LTE Maximum Measurement Period
Smart LTE Layering NRT User Amount Threshold
LTE Minimum Measurement Interval Smart LTE Layering Target System Selection LTE Neighbour Carrier Frequency Search Period
Max number of UEs in HSDPA CM due to NCHO
LTE Layer Cell HSDPA Load NOT CONFIGURABLE
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BASIC PARAMETER
ADVANCED PARAMETER
PARAMETER NOT CHECKED IF MEASUREMENTS ENABLED
Configuration Management – Parameters RAN2980 Measurement Based LTE Layering RNC/HOPL
RNC/RNMOBI
LTE Carrier Frequency selection Minimum Rx power level
Smart LTE Layering Service Control
LTE Carrier Frequency selection Minimum Rx Quality level
Timer for Smart LTE Layering Prevention Timer
Adjacent LTE Frequency Priority
LTE Target Frequency Criterion CSFB detection for blind redirection
RNC
LTE Periodic Trigger Timer
Transmission Gap Length for LTE carrier frequency measurements
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•
RNC/RNMOBI parameters give a possibility to choose services that will be redirected to LTE system.
•
RNC/WBTS BTS support for HSPA Compressed Mode parameter defines if compressed mode for HSDPA traffic is enabled
RNC/WBTS
E-UTRA Absolute Radio Frequency Channel Number BASIC PARAMETER
RNC/HOPL parameters are used for setting threshold values that are compared to UE measured values. Thresholds are used for redirection decision.
RNC/RNHSPA
RNC/…/WCEL/ADJL
Adjacent LTE Selected Frequency (EARFCN)
•
PARAMETER NOT CHECKED IF MEASUREMENTS ENABLED
BTS support for HSPA CM ADVANCED PARAMETER
PARAMETER NOT CHECKED IF MEASUREMENTS ENABLED
M1010 Inter System Hard Handover RAN2980 Measurement Based LTE Layering related counters (1/2)
LTE CARRIER NOT FOUND FOR REDIRECTION M1010C237
LTE REDIRECTION STARTED AFTER MEASUREMENT M1010C238
Measuring cases when no carrier frequency was found for LTE redirection during measurements (with/without Compressed Mode.)
Measuring cases when LTE redirection was started after finding good enough carrier frequency with measurements (with/without CM). - UE with initiated Redirection Procedure
Measurements
- Redirection not started due to measurements’ results
Updated every time when measurement performed by the UE DOESN’T RESULT in a finding the LTE carrier frequency with acceptable quality to perform redirection.
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Updated every time when measurement performed by the UE RESULTS in a finding the LTE carrier frequency with acceptable quality to perform redirection and the RNC initiates the redirection procedure
M1010 Inter System Hard Handover RAN2980 Measurement Based LTE Layering related counters (2/2)
M1010C239 DURATION OF LTE CARRIER MEASUREMENT Measuring the duration of the LTE frequency band measurements in SRNC (with/without compressed mode)
Measurements
500ms 1s
2s
Sum from one WCDMA Cell
Updated every time when the LTE frequency band measurement session ends either to perform the redirection decision, or the decision not to perform it due to no good enough carrier found or the session was released/dropped during this measurement.
M1006 RRC signaling RAN2980 Measurement Based LTE Layering related counters
M1006C310 RRC CONN RELEASE LTE REDIR IN DCH The number of RRC connection releases for LTE redirection due to Periodic Trigger T(4) i.e. success cases when UE was redirected to LTE with periodic trigger enabled. COUNTER: Number of RRC Connection Rel. due to T4 Trigger T4 Trigger T1 Trigger T4
Updated when the RNC sends RRC Connection Release message to the UE redirecting it to LTE, and the redirection was performed due to periodic trigger.
RAN2980: Measurement Based LTE Layering RAN2717 RAN3069: RSRQ-based LTE Reselection RAN2264: Smart LTE Handover RAN2881: WCDMA and GSM Layer Priorities
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RN30083EN50GLA0
With and without the feature RAN3069 RSRQ-based LTE Reselection
RAN2067 Activated
RAN3069 Not activated
RAN2067 Activated
• SIB19 message does not contain quality threshold (LTE RSRQ minimum required level)
• SIB19 message contains quality threshold (LTE RSRQ minimum required level)
• UE performs reselection based on RSRP criterion • It may happen that the UE is not able to camp on LTE Cell due to low quality of the LTE signal (too low RSRQ)
• UE performs reselection based on RSRQ criterion • UE does not try to camp on LTE cell if quality thresholds are not met (even if signal level threshold is good enough - RSRP)
• Service interruption is observed!!!!
• No service interruption is possible
It is possible that the UE could not camp on an LTE cell due to signal quality level
UE reselect to LTE cell only if signal quality threshold is exceeded
RSRP criterion is fulfilled. However, minimum RSRQ requirement is not met – UE cannot access the cell
WCDMA Cell
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RAN3069 Activated
LTE Cell
UE checked RSRQ before reselection decision was made – UE can access the cell
WCDMA Cell
LTE Cell
Benefits and Gains RAN3069 RSRQ-based LTE Reselection
Brief Description: • This feature supports UE priority based cell reselection from WCDMA to LTE • The operator is able to set priorities for different Radio Access Technologies (RATs)
UTRAN Connected Mode
• Priorities are communicated to UE via SIB19 broadcast message
Cell_PCH
URA_PCH
Cell_DCH
Cell_FACH
• System Information Block number 19 (enabling LTE cell reselection) is introduced by 3GPP Release 8
• 3GPP Release 9 introduces quality based reselection • Additional, signal quality related thresholds are supported by RAN3069 RSRQ-based LTE Reselection
Establish RRC Connection
These features introduce parameter set that is necessary to perform priority based reselection to LTE
Release RRC Connection
Idle mode
Benefits: Based on rules it reselects back to LTE
UE listens to broadcast channel (SIB19)
LTE rollout phase support
In the initial phase, the LTE covearge is limited and UEs easily run out of it. Both TDD and FDD UARFCNs are supported. LTE cell reselection
LTE-users who did change RAT to WCDMA due to coverage/service reasons are able to automatically return to LTE. Thanks to 3GPP Rel-9 enhancements, LTE RSRP and RSRQ criteria are used.
35
Interdependecies RAN3069 RSRQ-based LTE Reselection Feature Interdependencies:
• RAN3069 RSRQ-based LTE Reselection requires one of the following HW elements:
RAN2067
• Flexi System Module Rel-1 • Flexi System Module Rel-2 • Flexi System Module Rel-3
LTE Interworking
• RAN3069 RSRQ-based LTE Reselection requires RAN2067 LTE Interworking • RAN3069 RSRQ-based LTE Reselection is an extension suporting 3GPP Rel9 quality thresholds for LTE cell reselection.
This feature introduces 3GPP Rel-9 extension – quality thresholds REQUIRES RAN2067 LTE INTERWORKING
Flexi System Module Rel-1, Rel-2, Rel-3 RAN3069 RSRQ-based LTE Reselection
RSRQ-based Cell Reselection
RAN2176
This is E-UTRAN counterpart for RAN3069 RSRQ-based LTE Reselection
• The quality thresholds include the UTRA serving cell Ec/N0 threshold and EUTRA neighbour cell RSRQ quality thresholds.
Feature allows seamless RAT change form LTE to WCDMA
• There is no separate licence for RAN3069 RSRQ-based LTE Reselection (this feature is controlled by RAN2067 LTE Interworking feature)
LTE1036
LTE PS Handover
E-UTRAN counterparts:
• LTE762 Idle Mode Mobility from LTE to WCDMA, GSM or other LTE Bands is EUTRAN counterpart for RAN2067 LTE Interworking
Feature allows seamless VoIP -> CS Handovers and CS FBs to WCDMA
• It allows idle mode mobility from LTE towards WCDMA – UE performs
RAN2435 SRVCC from LTE and CSFB with HO
measurement and reselection decision based on RSRP and RSCP
• LTE1036 RSRQ-based Cell Reselection is E-UTRAN counterpart for RAN3069 RSRQ-based LTE Reselection
• This feature introduces 3GPP Rel-9 extension to idle mode mobility
Possibility to control the order in which the information on E-UTRA frequency LTE neighbours are sent to UE via SIB19
RAN3088 E-UTRA Frequency Ordering
between LTE and WCDMA – quality thresholds.
• UE performs measurement and reselection decision based on RSRQ and Ec/No Mandatory
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LTE762 This is E-UTRAN counterpart for RAN2067 LTE Interworking
Interworking
Optional
Recommended
Idle Mode Mobility from LTE to WCDMA, GSM or other LTE Bands
Details -> next slide
Interdependecies RAN3069 RSRQ-based LTE Reselection and RAN3088
E-UTRA Frequency Ordering
Feature impact:
• With RAN2067 LTE Interworking or RAN3069 RSRQ-based LTE Reselection, the operator does not have the possibility to control the order in which EARFCNs are provided on E-UTRA frequency and priority info list.
• Especially when modifications to existing lists is carried out (for example addition or deletion of ADJL object, or RNC
Iphone5 reads only first 5 LTE frequencies in SIB19 (the operator can configure up to 8 LTE layers)
restart)
• It is known that different UEs have different implementation with regard to the reading order of this information • IPhone 5 reads only first 5 LTE frequencies in SIB19 (the operator can configure up to 8 LTE layers) • Being Iphone5 the popular LTE phone in customers’ networks, controlling of the list order brings tangible benefits in terms of performance of the WCDMA LTE mobility procedure
• This is directly translating in faster availability of LTE network to the end-users
• RAN3088 E-UTRA Frequency Ordering allows to put LTE frequencies for cell reselection (signalled via SIB19) in priority orderr defined by the following parameters:
• HOPL- AdjLAbsPrioCellReselec and • ADJL-ADJLId (used if two EARFCNs have equal HOPL- AdjLAbsPrioCellReselec parameter value)
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IPhone 5
Interdependecies RAN3069 RSRQ-based LTE Reselection - General requirements
Both features are introduced to follow 3GPP specifications in terms of idle mode mobility between WCDMA and LTE.
LTE Reselection 38
Release-8 capable RNC
AND
System Information Block number 19 (enabling LTE cell reselection) is introduced by 3GPP Rel-8. Thus, RAN2067 LTE Interworking feature requires:
Release-8 capable UE
3GPP Rel-8 Quality extensions in System Information Block number 19 are introduced by 3GPP Rel-9. Thus, LTE3069 RSRQ-based LTE Reselection feature requires:
3GPP Rel-9
Release-9 capable RNC
AND
• Rel-8 specifies the basic concept of cell reselection based on absolute priorities of WCDMA and LTE layers. UE performs the reselection decision based on measurement results (RSRP and RSCP results are taken into account) • Rel-9 specifies the extension to absolute priority based cell reselection. Starting from now, UE uses quality thresholds during reselection decision.
UE Vendor
Release-9 capable UE
Technical details RAN3069 RSRQ-based LTE Reselection – How does it work?
1
3
• SIB19 defines available E-UTRA frequencies characterized by:
• E-UTRA Absolute Radio Frequency Channel Number (EARFCN)
• Measurement bandwidth • LTE layer priority • Threshold parameters that are used by the UE to define LTE layer measurement rules
• Threshold parameters to decide on reselection criteria – both WCDMA layer related and LTE layer related parameters are delivered
• The Broadcast Channel BCH transports the information of logical Broadcast Control Channel
• This is then carried in the Primary Common Control Physical Channel (PCCPCH). All UEs are able to decode the information on this channel
UTRA Priority Info Threshservlow 2dB Sprioritysearch1 14dB Sprioritysearch2 2dB AbsPrioCellReselec 3
EUTRA Priority Info List
EUTRA layer 1
• Once decoded, the BCCH provides the UE with the necessary general parameters for both system and cell level to enable it to communicate with the network
• 3GPP defines 19 different SIBs • Each SIB groups together system information elements of the same nature
39
2
SIB3
SIB19
AdjLEARFCN 1401 AdjLMeasBw 50 AdjLAbsPrioCellReselec 7 AdjLQrxlevminEUTRA -130dBm AdjLThreshigh 18dB AdjLThreslow 4dB
EUTRA layer 2 AdjLEARFCN 6240 AdjLMeasBw 50 AdjLAbsPrioCellReselec 2 AdjLQrxlevminEUTRA -130dBm AdjLThreshigh 18dB AdjLThreslow 4dB
SIB4 QqualMin -15dB QrxlevMin -115dBm Treselection 2s TreselectionPCH 2s
• UE behaves according to 3GPP specification • This feature uses Absolute Priority Based Reselection specified in TS 25.304 „User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode”
• Based on delivered parameters via broadcast channel UE performs reselection from WCDMA towards LTE
• If a UE is Rel-9, it takes into account quality thresholds (WCDMA Ec/No and LTE RSRQ)
Technical Details RAN3069 RSRQ-based LTE Reselection - SIB scheduling
Hierarchical manner of SIB scheduling
• Up to two scheduling blocks (SB) may also be present, which contain the scheduling information for the SIBs • Master Block (MIB)inacts an index to the SIBs whichInformation could not be provided the as MIB contained in the broadcast. It is sent regularly on the BCH and its • The SIB is only valid in the cell or Public Land Mobile scheduling is static. Network (PLMN) in which it was read.
• UE must find out the schedule of various SIBs so that it can wake up and receive only those blocks it needs and skip reception of the others.
MIB SB1
SIB1 SB2 SIB2
How does it work? The UE wants to know parameters contained in SIB11
40
It receives MIB and knows exactly when SIB11 is planned to be broadcasted or when SB1/SB2 (containing the information when SIB11 is available) will be broadcasted
SIB3 ...
SIB19
Technical Details RAN3069 RSRQ-based LTE Reselection - SIB19
• What does the SIB19 contains?
MIB
Information Element/ Group name
SIB19
SIB3
SIB4
SIB5
Provides priority based reselection information for UTRA
E-UTRA frequency and priority info list
Provides priority based reselection information for E-UTRA
• The items on E-UTRA frequencies list (from 1 up to 8 items can be defined) are characterized by: • EARFCN
• The UTRA priority info list is characterized by: • AbsPrioCellReselec
Downlink E-UTRA Absolute Radio Frequency Channel Number (EARFCN)
• Measurement Bandwidth It indicates the number of resource blocks over which the UE could measure
•
• Priority Determines reselection priority of the corresponding EARFCN
• QrxlevminEUTRA Determines the minimum required Reference Signal Received Power (RSRP) level
•
• Threshx,high It specifies the RSRP threshold used by the UE when reselecting towards the higher priority frequency
• Threshx,low
•
It specifies the RSRP threshold used by the UE when reselecting towards the lower priority frequency
• QqualminEUTRA Determines the minimum required Reference Signal Received Quality (RSRQ) level
• Threshx,high2 It specifies the RSRQ threshold used by the UE when reselecting towards the higher priority frequency
• Threshx,low2 It specifies the RSRQ threshold used by the UE when reselecting towards the lower priority frequency 41
… Parameters in PURPLE are provided only if RAN3069 RSRQ-based LTE Reselection is enabled
Description
UTRA priority info list
SIB11
•
Defines the absolute priority level of the serving cell which is used in the priority based cell-reselection. Sprioritysearch1 Defines the threshold for Srxlev in the serving cell controlling the inter-frequency and inter-RAT measurements. Sprioritysearch2 Defines the threshold for Srxlev in the serving cell controlling the inter-frequency and inter-RAT measurements. Threshservlow Defines the threshold for Srxlev in the serving cell below which the UE may perform cell reselection to a cell on a lower absolute priority layer. Threshservlow2 Defines the threshold for Squal in the serving cell below which the UE may perform cell reselection to a cell on a lower absolute priority layer.
Technical Details
Frequency
RAN3069 RSRQ-based LTE Reselection - RSRP and RSRQ
Reflects power of a single resource element estimated based on Reference Signal
Reference Signal (RS) Slot 1 (0,5 ms) 7 symbols
12 subcarriers
UE measures the power of multiple resource elements used to transfer the Reference Signal (RS) and calculates the average over all Reference Signals (3GPP TS 36.214) Example: 1.4 MHz LTE bandwidth: • 6 Resource Blocks over which UE measures RSRP • Each RB contains 4 Reference Signals • 2 in slot 0 • 2 in slot 5 • UE measures RSRP only in symbols containing Reference Signals (slot 0 and slot 5 of each Resource Block) • Consequently, measurement is the average power of 12 Reference Signal
Subframe (TTI) 1 ms
RSRP=
Resource Block (RB)
avg Time
42
Technical Details RAN3069 RSRQ-based LTE Reselection - RSRP and RSRQ
Frequency
RSRQ - Reference Signal Received Quality is radio channel quality indicator reflecting interference level. According to 3GPP TS 36.214: RSRQ=RSRP/(RSSI/N) where: N – the number of RBs of the RSSI measurement BW RSRP - power of a single resource element estimated based on Reference Signal RSSI - (Received Signal Strength Indicator) - the total received power (over the considered measurement BW); includes all radio signal sources: co-channel serving and non-serving cells, adjacent channel interference, thermal noise etc. Example: 1.4 MHz LTE bandwidth: • 6 Resource Blocks over which UE measures RSRQ • Each RB consists of 12 subcarriers • UE measures RSRQ only in symbols containing Reference Signals
Reference Signal (RS)
12 subcarriers
Slot 1 (0,5 ms) 7 symbols
Subframe (TTI) 1 ms
avg
RSRQ= 43
(
all
+ 6
all
)
Resource Block (RB) Time
Technical Details RAN3069 RSRQ-based LTE Reselection - Measurement rules
Measurement rules for RAN3069 RSRQ-based Cell Reselection are the same as for RAN2067 LTE Interworking Higher priority layer
Lower priority layer
• If the UE has received absolute priority information for different layers and
• One of the following criteria need to be fulfilled in order to start measurements
there is a layer with higher priority than the current serving layer has, the UE follows this rule:
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):
UE starts to search higher priority layers immediately. Each
1. RX level (CPICH RSCP) in the serving cell falls below threshold:
(Nlayers * 60) seconds
Measured RSCP – Minimum RSCP <= RSCP_Threshold1
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.
2. Quality level (CPICH Ec/No) in the serving cell falls below threshold:
OR Measured Ec/No – Minimum Ec/No <= Ec/No_Threshold1 where: Minimum RSCP = WCEL-QrxlevMin (default -115dBm) RSCP_Threshold1 = WCEL-Sprioritysearch1 (default 14dB) Minimum Ec/No = WCEL-QqualMin (default -18dB) Ec/No_Threshold1 = WCEL-Sprioritysearch2 (default 0dB, recommended 4dB)
44
Priority 7
LTE layer 1
Priority 7
LTE layer 1
Priority 5
WCDMA layer
Priority 5
WCDMA layer
Priority 4
LTE layer 2
Priority 4
LTE layer 2
The UE is camped in WCDMA layer cell.
Technical Details RAN3069 RSRQ-based LTE Reselection - LTE Reselection criteria for RAN2067 LTE Interworking
RAN2067 Activated
RAN3069 Not Activated
Reselection rules: Towards higher priority layer
Towards lower priority layer
• The reselection is triggered if Reference Signal Received Power (RSRP) level
• The reselection is triggered if Reference Signal Received Power (RSRP) level
of LTE candidate cell is above the threshold related to higher priority layer over the defined time period.
of LTE candidate cell is above the threshold related to lower priority layer AND signal level or signal quality of current serving cell falls below threshold (both events occure simultaneously over the defined time period).
during the
Measured RSRP – Minimum RSRP > RSRP_Threshold1 Treselection time period
Measured RSCP – Minimum RSCP <= RSCP_Threshold2
OR Measured Ec/No – Minimum Ec/No <= 0
where: Minimum RSRP = HOPL-AdjLQrxlevminEUTRA (default -130Bm) RSRP_Threshold1 = HOPL-AdjLThreshigh (default 18dB)
AND
during the Treselection time period
Measured RSRP – Minimum RSRP > RSRP_Threshold2
Priority 7
LTE layer 1
Priority 5
WCDMA layer
Priority 4
LTE layer 2
where: Minimum RSCP = WCEL-QrxlevMin (default -115dBm) RSCP_Threshold2 = WCEL- Threshservlow (default 2dB) Minimum Ec/No = WCEL-QqualMin (default -18dB) Minimum RSRP = HOPL-AdjLQrxlevminEUTRA (default -130dBm) RSRP_Threshold2 = HOPL-AdjLThreslow (default 4dB)
• WCEL-Treselection is a parametr defining the time period for which the cell reselection criteria need to be fulfilled to trigger the reselection of a new cell
• Depend on current mobility state UE uses WCEL-Treselection or WCELTreselectionPCH timer. These parameters are broadcast via SIB3, SIB4 messages
• The additional restriction is that the UE cannot reselect to any cell if it is camped to the current serving cell less then 1 second 45
Technical Details RAN3069 RSRQ-based LTE Reselection - LTE Reselection criteria for RAN3069 RSRQ-based LTE Reselection
RAN2067 Activated
RAN3069 Activated
Reselection rules: Towards higher priority layer
Towards lower priority layer
• The reselection is triggered if Reference Signal Received Quality (RSRQ) level of LTE candidate cell is above the threshold related to higher priority layer over the defined time period.
during the
Measured RSRQ – Minimum RSRQ > RSRQ_Threshold1 Treselection time period
• The reselection is triggered if Reference Signal Received Quality (RSRQ) level of LTE candidate cell is above the threshold related to lower priority layer AND signal level or signal quality of current serving cell falls below threshold (both events occure simultaneously over the defined time period). Measured RSCP – Minimum RSCP <= RSCP_Threshold2
OR Measured Ec/No – Minimum Ec/No <= Ec/No_Threshold2
where: Minimum RSRQ = HOPL-AdjLQqualminEUTRA (default: -35dBm[not broadcast]) RSRQ_Threshold1 = HOPL-AdjLThreshigh2 (default: 32 dB [not broadcast])
AND
during the Treselection time period
Measured RSRQ – Minimum RSRQ > RSRQ_Threshold2
Priority 7
LTE layer 1
Priority 5
WCDMA layer
Priority 4
LTE layer 2
where: Minimum RSCP = WCEL-QrxlevMin (default -115dBm) RSCP_Threshold2 = WCEL- Threshservlow (default 2dB) Minimum Ec/No = WCEL-QqualMin (default -18dB) Ec/No_Threshold2 = WCEL- Threshservlow2 (default 0dB [not broadcast]) Minimum RSRQ = HOPL-AdjLQqualminEUTRA (default: -35dBm [not broadcast]) RSRQ_Threshold2 = HOPL-AdjLThreslow2 (default: 32dB [not broadcast])
• WCEL-Treselection is a parametr defining the time period for which the cell reselection criteria need to be fulfilled to trigger the reselection of a new cell
• Depend on current mobility state UE uses WCEL-Treselection or WCELTreselectionPCH timer. These parameters are broadcast via SIB3, SIB4 messages
• The additional restriction is that the UE cannot reselect to any cell if it is camped to the current serving cell less then 1 second
Deployment aspects RAN3069 RSRQ-based LTE Reselection - Activation
RAN2067 LTE Interworking
LTE absolute priority cell reselection was originally introduced by the RAN2067 LTE interworking feature.
RAN3069 RSRQ-based LTE Reselection is an extension suporting 3GPP Rel-9 quality thresholds for LTE cell reselection. The quality thresholds include the UTRA serving cell Ec/N0 threshold and E-UTRA neighbour cell RSRQ quality thresholds. This extension is controlled by the RAN2067 LTE Interworking feature There is no separate licence for RAN3069 RSRQ-based LTE Reselection (this feature is controlled by RAN2067 LTE Interworking feature)
Preconditions for activation License for interdependent, mandatory feature RAN2067 LTE Interworking need to be activated License Key: Cell Reselection to LTE License Name: Cell Reselection to LTE Feature Code: 1755 License Type: Long-term ON/OFF License Type: Long-term ON/OFF licence It is possible to create and modify ADJL and License can be activated using MML command: HOPL objects (and respective parameters), introduced by the RAN2067 LTE ZW7M: FEA=1755:ON; for Cell Reselection to LTE LK Description: Interworking and RAN3069 RSRQ-based Activate the feature on cell basis via WCEL-LTECellReselection LTE Reselection if the license exist and the state is ON.
Deployment aspects RAN3069 RSRQ-based LTE Reselection - Trial Area
Recommended trial area: In order to check whether RAN3069 RSRQ-based LTE Reselection works
WCDMA-LTE coverage overlapped
appropriately, trial area should be selected, so that the WCDMA network coverage and LTE network coverage is present
at lest one EARFCN should be available In order to follow UE behaviour with multiple EARFCNs, more than one LTE carrier should be available (configuration of neighbors should reflect that fact)
Different priority settings should be examined so that reselection to lower and higher priority layer are checked
Feature can be tested in the following environments: WCDMA – LTE coverage is fully overlapped In this case, user can be quickly moved back to LTE if LTE layer
WCDMA coverage LTE coverage
priority is set to higher value
If LTE layer has lower priority value, UE reselects back to LTE only if WCDMA signal strenght/quality falls below thresholds – unusual scenario
WCDMA – LTE coverage is not fully overlapped (LTE coverage holes) Consider frequent, unsuccesfull UE measurements of higher priority LTE layer
WCDMA-LTE coverage non- overlapped
User scenario RAN3069 RSRQ-based LTE Reselection - WCDMA-LTE
coverage non- overlapped UTRA Priority Info Threshservlow 2dB Sprioritysearch1 14dB Sprioritysearch2 2dB AbsPrioCellReselec 3 Threshservlow2 1dB
It is assumed that WCDMA network coverage spans over whole city area. WCDMA layer priority
5
EUTRA Priority Info List EUTRA layer 1 AdjLEARFCN 1401 AdjLMeasBw 50 AdjLAbsPrioCellReselec 7 AdjLQrxlevminEUTRA -130dBm AdjLThreshigh 18dB AdjLThreslow 4dB AdjLQqualMinEUTRA -18dB AdjLThreshigh2 4dB AdjLThreslow2 4dB
WCDMA LTE is in initial phase of deployment (purple area). LTE capable UE performs Cell Reselections on LTE coverage borders. LTE layer priority
7
LTE LTE RSRQ = -11 dB
LTE RSRQ = -14 dB UE cheks LTE layer 1 availability every (Nlayers x 60) seconds and discovers it while approaching the coverage border LTE RSRQ = -16 dB
EUTRA layer 2 AdjLEARFCN 6240 AdjLMeasBw 50 AdjLAbsPrioCellReselec 2 AdjLQrxlevminEUTRA -130dBm AdjLThreshigh 18dB AdjLThreslow 4dB AdjLQqualMinEUTRA -18dB AdjLThreshigh2 4dB AdjLThreslow2 4dB
User scenario RAN3069 RSRQ-based LTE Reselection - WCDMA-LTE
coverage overlapped UTRA Priority Info Threshservlow 2dB Sprioritysearch1 14dB Sprioritysearch2 2dB AbsPrioCellReselec 3 Threshservlow2 1dB
It is assumed that WCDMA network coverage spans over whole city area. WCDMA layer priority
5
EUTRA Priority Info List EUTRA layer 1 AdjLEARFCN 1401 AdjLMeasBw 50 AdjLAbsPrioCellReselec 7 AdjLQrxlevminEUTRA -130dBm AdjLThreshigh 18dB AdjLThreslow 4dB AdjLQqualMinEUTRA -18dB AdjLThreshigh2 4dB AdjLThreslow2 4dB
WCDMA LTE coverage is free of holes. VoLTE is not available. CSFB meachanisms implemented in E-UTRA. LTE layer priority
7 LTE Based on measurement and reselection rules, UE reselects back to LTE
Voice Call is disconnected . UE goes to Idle state and reads BCH
UE in connected mode in 3G due to CSFB from LTE. CS Call is ongoing.
EUTRA layer 2 AdjLEARFCN 6240 AdjLMeasBw 50 AdjLAbsPrioCellReselec 2 AdjLQrxlevminEUTRA -130dBm AdjLThreshigh 18dB AdjLThreslow 4dB AdjLQqualMinEUTRA -18dB AdjLThreshigh2 4dB AdjLThreslow2 4dB
Configuration Management RAN3069 RSRQ-based LTE Reselection - Parameters
Parameters introduced by RAN2067 LTE Interworking: RNC-SIB19Priority WCEL-AbsPrioCellReselec WCEL-LTECellReselection WCEL-Sprioritysearch1 WCEL-Sprioritysearch2 WCEL-Threshservlow HOPL-AdjLAbsPrioCellReselec HOPL-AdjLQrxlevminEUTRA HOPL-AdjLThreshigh HOPL-AdjLThreslow ADJL-AdjLEARFCN ADJL-AdjLMeasBw Parameters introduced by RAN3069 RSRQ-based LTE Reselection: WCEL-Threshservlow2 HOPL-AdjLQqualminEUTRA HOPL- AdjLThreslow2 HOPL- AdjLThreshigh2 Already existing parameters: WCEL-Treselection WCEL-TreselectionPCH
RNC SIB19Priority
Introduced by RAN3069 Introduced by RAN2067 Already existing
WBTS
WCEL AbsPrioCellReselec LTECellReselection Sprioritysearch1 Sprioritysearch2 Threshservlow Threshservlow2 Treselection TreselectionPCH
HOPL (up to 10) HopLId AdjLAbsPrioCellReselec AdjLQrxlevminEUTRA AdjLThreshigh AdjLThreslow AdjLQqualminEUTRA AdjLThreslow2 AdjLThreshigh2
ADJL (up to 8) AdjLId HopLIdentifier AdjLEARFCN AdjLMeasBw
Configuration Management RAN3069 RSRQ-based LTE Reselection - Parameterization Scenario
It is necessary to align reselection triggers in both RANs In E-UTRAN, RSRQ based cell reselection is controlled by LTE1036 RSRQ-based Cell Reselection (RL50/RL35TD/RL50FZ)
LTE priority = 7
Measurements: Always Reselection: RSRQ > AdjLQqualminEUTRA + AdjLThreshigh2 = -19dB + 4dB = -15dB
Measurements: RSRQ < qQualMinR9 + sNonIntraSearchQR9 = -19dB + 4dB = -15dB Reselection: RSRQ < qQualMinR9 + threshServingLowQR9 = -19dB + 2dB = -17dB AND Ec/No > qQualMinUtra+ utraFrqQThrLowR9 = -18dB + 4dB = -14dB
WCDMA priority = 6 Measurements: Ec/No <= qQualMin + Sprioritysearch2 = -18dB + 4dB = -14dB Reselection: Ec/No <= qQualMin + Threshservlow2 = -18dB + 1dB = -17dB AND RSRQ > AdjLQqualminEUTRA + AdjLThreslow2 = -19dB + 4dB = -15dB
LTE priority = 5
Measurements: Always Reselection: Ec/No > qQualMinUtra + utraFrqQThrHighR9 = -18dB + 4dB = -14dB
Configuration Management RAN3069 RSRQ-based LTE Reselection - User scenario
UE reselects from WCDMA to LTE based on LTE signal quality
SIB19 UTRA Priority Info Threshservlow 2dB Threshservlow2 1dB Sprioritysearch1 14dB Sprioritysearch2 2dB AbsPrioCellReselec 3
Treselection timer RAN3069 2 seconds
3G
Treselection timer RAN2067
3G
2 seconds
EUTRA Priority Info List
-115 + 14 (Qrxlevmin + Sprioritysearch1) 3G
3G
3G
3G
3G
3G
3G
3G
3G
3G 4G
-115 + 2 (Qrxlevmin + Threshservlow)
EUTRA layer 1 AdjLEARFCN 1401 AdjLMeasBw 50 AdjLAbsPrioCellReselec 7 AdjLQrxlevminEUTRA -130dBm AdjLQqualMinEUTRA -18dB AdjLThreshigh 18dB AdjLThreslow 4dB AdjLThreshigh2 4dB AdjLThreslow2 4dB
LTE RSRQ [dB]
WCDMA RSCP [dBm]
3G
4G
4G
-18 + 4 (AdjLQqualminEUTRA + AdjLThreshigh2)
-130 + 18 (AdjLQrxlevminEUTRA + AdjLThreshigh)
-130 + 4 (AdjLQrxlevminEUTRA + AdjLThreslow)
SIB3 SIB4 WCDMA layer RSCP LTE layer 1 RSRP (1800MHz)
LTE layer 1 RSRQ (1800MHz)
Time [s]
QqualMin -15dB QrxlevMin -115dBm Treselection 2s TreselectionPCH 2s
EUTRA layer 2 AdjLEARFCN 6240 AdjLMeasBw 50 AdjLAbsPrioCellReselec 2 AdjLQrxlevminEUTRA -130dBm AdjLQqualMinEUTRA -18dB AdjLThreshigh 18dB AdjLThreslow 4dB AdjLThreshigh2 4dB AdjLThreslow2 4dB
RAN2980: Measurement Based LTE Layering RAN3069: RSRQ-based LTE Reselection RAN2717 RAN2264: Smart LTE Handover RAN2881: WCDMA and GSM Layer Priorities
54
Introduction RAN2264 Smart LTE Handover
• RAN2067 LTE Interworking (RU20 On Top) and RAN3069 RSRQ based LTE Reselection (RU50) • The UE, on operator’s preference, selects to camp on LTE layer based on absolute layers’ priorities once coverage is available. • RAN3069 introduces quality criteria (RSRQ)
WCDMA - LTE Interworking overview
• RAN2176 LTE PS Handover (RU20 On Top) • Seamless handover of data services to WCDMA when Cell_DCH
RRC_CONNECTED
leaving the LTE coverage with minimal interruption time.
• Multi-RAB handover is supported. • RAN2435 SRVCC from LTE and CSFB with HO (RU40) • Single Radio Voice Call Continuity from LTE to WCDMA
Cell_FACH
allows LTE VoIP call to be handed over to WCDMA as a normal CS voice call.
Cell_PCH
• CS Fallback support (if VoLTE call cannot be setup, for realization of the voice call the UE is handed over to WCDMA for CS connection setup)
URA_PCH
• RAN2717 Smart LTE Layering (RU40) • Efficient mechanisms for moving active UEs to the LTE layer UTRA_IDLE
RRC_IDLE
(RRC Connection Release with Redirection command to LTE).
• RAN2264 Smart LTE Handover (RU50) • WCDMA LTE outgoing PS handover once LTE coverage is available
• RAN2980 Measurement based LTE Layering (RU50) • Moving active UEs to the LTE layer (measurements of LTE layer are done before redirection command)
Introduction RAN2264 Smart LTE Handover
Evolution path and interworking of LTE mobility features –RU50 EP2???? • • • •
RAN2067 LTE Interworking (LTE cell reselection) is a pre-requisite for RAN2264 Smart LTE Handover ADJL- and HOPL Managed Object Classes and respective parameters, introduced by the RAN2067 LTE Interworking feature, are needed for handover All these features can be used simultaneously Operator can implement the desired strategy by combining the features
• RAN2067 LTE Interworking • UE reselects LTE in idle mode or in connected mode (Cell_PCH, URA_PCH) based on the absolute priorities broadcast in SIB19
Cell Reselection to LTE
Blind Redirection • RAN2717 Smart LTE Layering • UE is moved from WCDMA to LTE without measurements by indicating LTE frequencies in RRC connection release
• RAN2980 Measurement based LTE Layering • UE is moved to LTE by indicating LTE frequencies in RRC connection release. Inter-RAT measurements are used for searching for the best LTE frequencies
Redirection with measurements
Handover • RAN2264 Smart LTE Handover • UE is moved from WCDMA to LTE by handover to an LTE cell. Inter-RAT measurements are used for searching for the best LTE cells. Handover and relocation signalling is applied
With and without the feature RAN2264 Smart LTE Handover
RAN2264 Not activated • No possibility to move active UEs directly to LTE EMM_CONNECTED state • UEs are redirected to LTE via RRC Connection Release message containing E-UTRA Target Info IE
• UE connection is terminated and UE redirected to LTE in idle mode w/out guaranty that target LTE can serve UE
• In UTRAN Cell_DCH state the UE performs Compressed Mode (or noncompressed mode) measurements of LTE Layers and performs a handover
• No need to go to RRC_IDLE state • End user experience is optimized – seamless handover – resources are reserved in advance on LTE side
There is no possibility to handover active UEs from WCDMA to LTE
Cell_DCH
RAN2264 Activated
EMM_CONNECTED
RRC_IDLE
Seamless handover based on several triggers
Cell_DCH
EMM_CONNECTED
RRC_IDLE
Benefits and Gains RAN2264 Smart LTE Handover
Brief Description:
• This mechanism is a next step on WCDMA – LTE interworking path. • Inter-RAT handover from WCDMA to LTE starts if compressed mode (or noncompressed mode) measurements indicate that LTE coverage is available.
• Measurements are triggered by the same events as for RAN2980
LTE
3G
Measurement Based LTE Layering feature (Inactivity, CTS, CS RAB release, Periodic check)
• Target system can be FDD-LTE and TDD-LTE
UE in WCDMA Cell_DCH
Benefits: Load balancing UE in LTE EMM_CONNECTED
End user experience
• Support of traffic steering and network load balancing scenarios offloading WCDMA network during high load states via seamless handover to LTE
• Support of current strategy in initial phase of deployment of LTE networks: move any LTE capable UE to LTE; let them only to perform CS calls in 3G but then pushing back to LTE
• Optimized end user experience by seamless RAT change from loaded 3G network
Interdependecies RAN2264 Smart LTE Handover
RAN2067
RAN2067 license must be installed and feature must be activated
Interworking mechanism implemented
LTE Interworking
RAN2717
No license needed for RAN2717 but features share triggers
Smart LTE Handover works irrespective of the RAN1276
No license needed for RAN2980 but features share triggers
Measurement based LTE Layering
RAN2172
RAN2264
Feature allows seamless RAT change form LTE to WCDMA
Smart LTE Handover LTE measurements are prioritised against WCDMA inter-frequency measurements
RAN2176 LTE PS Handover
Feature allows seamless VoIP -> CS Handovers and CSFBs to WCDMA
Multi-Band Load Balancing
RAN2451
RAN1276 HSDPA InterFrequency Handover
Smart LTE Layering
RAN2980
RAN2136 Fast Dormancy
RAN2435 SRVCC from LTE and CSFB with HO
Support for E-DCH Compressed Mode
Interworking mechanism implemented
Fast Dormancy Profiling
Mandatory
Interworking
Optional
Recommended
RAN1668 HSUPA CM for LTE and Inter-Frequency Handover
Basic
Interdependecies RAN2264 Smart LTE Handover
RAN2067 LTE Interworking Cell reselection to LTE mechanism is a pre-requisite for Smart LTE Handover ADJL and HOPL objects (and respective parameters) introduced by the RAN2067 LTE Interworking feature, are needed for handover Activation of RAN2067 LTE Interworking is not required in the cell but the licence is enough in order to modify ADJL and HOPL parameters RAN2717 Smart LTE Layering / RAN2980 Measurement Based LTE Layering RAN2264 Smart LTE Handover feature is independent from the RAN2717 Smart LTE Layering and RAN2980 Measurement Based LTE Layering RAN2717 Smart LTE Layering or RAN2980 Measurement Based LTE Layering feature is not included in RAN2264 Smart LTE Handover feature, meaning it is not possible to redirect UE to LTE using RAN2264 Smart LTE Handover only
However, features can work simultaneously LTE handover is prioritised to LTE redirection if an event triggers both redirection and handover, details are described here RAN2172 Multi-Band Load Balancing RAN2172 Multi-Band Load Balancing feature applies Cell_DCH state inactivity (Cell_DCH to CCH state transition) as a trigger to start WCDMA inter-frequency measurements; also the Smart LTE Handover applies the same trigger to start LTE measurements
If the Cell_DCH to CCH state transition triggers both LTE and WCDMA inter-frequency measurements at the same time, LTE measurements are prioritised if other conditions for LTE handover are fulfilled
After the decision to perform LTE measurements is done and results do not lead to LTE handover, WCDMA measurements due to the same inactivity trigger are not started - UE is transferred to CCH state according to the legacy principles
This behaviour is followed by other non-critical WCDMA inter-frequency measurements applying Cell_DCH to CCH state transition as trigger (HSPA capability based handover).
Interdependecies RAN2264 Smart LTE Handover
RAN2136 Fast Dormancy If UE sends RRC: SIGNALLING CONNECTION RELEASE INDICATION message with cause value “UE Request PS Data Session End” while LTE measurements are ongoing, measurement are continued
If results does not lead to handover, UE is transferred to Cell_PCH/URA PCH state The state transition trigger becomes effective if UE sends RRC: SIGNALLING CONNECTION RELEASE INDICATION message with cause value “UE Request PS Data Session End” while LTE measurements are not ongoing
Thus, state change away from Cell_DCH is delayed; LTE measurement are started and UE is handed over to LTE if results are good enough
If results does not lead to handover, UE is transferred to Cell_PCH/URA PCH state
RAN2451 Fast Dormancy Profiling If UE sends RRC: SIGNALLING CONNECTION RELEASE INDICATION message without cause value, UE is transferred to Idle state despite of the fact that LTE measurements are ongoing
If the trigger in question is parameterized not to use LTE handover and RAN2980 or RAN2717 uses this trigger to redirect UEs blindly to LTE, UE is redirected to LTE in blind manner
Technical Details Triggers for RAN2264 Smart LTE Handover
Triggers – the following triggers may initiate LTE measurements preceding I-RAT Handover State Change Cell_DCH to CCH
Inactivity (state change from Cell_DCH to CCH) triggers IS LTE measurements followed by handover decision towards LTE
CS RAB Release with PS service
HSDPA/HSPA to DCH/DCH CTS
The reconfiguration from
CS RAB release trigger means
HSDPA to DCH (CTS) means cases where E-DCH/HS-DSCH --> DCH/DCH or DCH/HSDSCH --> DCH/DCH) with some other bit rate than 0 (pure release cases are excluded).
case where an UE has CS RAB and at least one active PS RAB and then CS RAB is released (UE would stay in CELL_DCH state in WCDMA).
UTRAN Connected Mode Cell_PCH
URA_PCH
DCH
Cell_DCH
Cell_FACH
HSDSCH
Periodic trigger
Expiry of new supervisory timer set for PS RAB connections triggers LTE measurements followed by handover decision
When LTE capable UE’s enter into CELL_DCH state, timer starts. After expiration, measurements are done. You can measure LTE layers when timer expires
Mr (10-100sec) Periodical Timer
3 1 One of 4 triggering event appeared 2
CELL_DCH
1
2 LTE measurments started 3 LTE handover decision
Technical Details Triggers for RAN2264 Smart LTE Handover
Fine-tuners - There are additional parameters that tune triggering measurements for Smart LTE Handover: Cell load Load criterion for triggering measurements is applied: If the cell is highly loaded, LTE is preferred, i.e. measurements and handover can be initiated If the cell is not highly loaded, WCDMA is preferred, i.e. measurements and handover cannot be initiated
HSDPA PPU
There are two load criteria: HSDPA power per user, originating from RAN2980 Measurement Based LTE Layering (WCEL-LTELayerCellHSLoad) • Measured power per user must be lower than the parameter value in order to enable LTE measurements
• The HSDPA power per user criterion is ignored if the special value „0” is set
• For this feature, CellWeightForHSDPALayering always equals 1
=1
PNRTHSDPA CellWeight ForHSDPALayering max( NumberOfNRTHSDPAusers,1)
The configured NRT user amount threshold must be exceeded before measurements are initiated NRT user amount threshold of the SRNC main cell is checked Users utilizing Interactive or Background RABs are counted as NRT users The user amount criterion is ignored if the special value „0” is set
WCEL-SmartLTELayeringUE Number of NRT users
#NRT users
NRT user amount, originating from RAN2717 Smart LTE Layering (WCEL-SmartLTELayeringUA) • • • •
WCDMA
Measurements allowed
Measurements not allowed
Time
Technical Details Triggers for RAN2264 Smart LTE Handover
Service restrictions Inter-RAT handover from WCDMA to LTE is supported for the following services: PS Interactive (NRT) QoS class - request response pattern (e.g. web browsing) PS Background (NRT) QoS class - destination is not expecting the data within a certain time (e.g. E-mails)
Multi-RAB combinations: 1…3 NRT PS (Interactive/Background only) RABs Operator can choose which services can be handed over to LTE via RNMOBI-
RNMOBI-SmartLTELayeringServ
3 (0011)
SmartLTELayeringServ parameter; handover is allowed only if every PS RAB of the UE is allowed to be handed over; Bit 2 (PS Streaming) and Bit 3 (PS Conversational) of the RNMOBIBit 3 SmartLTELayeringServ parameter is ignored for the need of handover as PS Conversational and PS Streaming RABs cannot be handed over to LTE
0 – redirection not allowed 1 – redirection allowed
Bit 0
Bit 2 Bit 1
Inter-RAT handover from WCDMA to LTE is not supported for the following services: PS Conversational (RT) QoS class – I-RAT handover for multi-RABs containing this QoS class is also not supported PS Streaming (RT) QoS class – I-RAT handover for multi-RABs containing this QoS class is also not supported Push-To-Talk RABs - if UE has PTT RAB established, the measurements for inter-RAT WCDMA to LTE handover cannot be be started; PTT identification is done by RAN2300 Optimized Push-To-Talk Experience via comparing RAB parameters of the new RAB to values set to the RNP parameter PTTUEMapping – if parameters match, RAB is considered as PTT
CS RABs – if UE has any CS RAB established, the measurements for inter-RAT WCDMA to LTE handover cannot be started
Technical Details Triggers for RAN2264 Smart LTE Handover
Transport channel combinations Smart LTE Handover is supported with any transport channel combination (SRB and RB mapping): Radio Bearer (RB): DCH/DCH UL throughput HS-DSCH/DCH HS-DSCH/E-DCH HS-DSCH/ E-DCH Signalling Radio Bearer (SRB): DCH/DCH 1 DCH/E-DCH HS-DSCH/E-DCH (F-DPCH) RAN1668 HSUPA Compressed Mode for IF and LTE HO license is not required to start compressed mode measurements in these RB (SRB) mapping cases RAN2264 Smart LTE Handover license is enough
DCH_UL compressed mode EDCH_UL normal mode UL-SCH in LTE
90% or more uplink throughput reduction
2
HS-DSCH / DCH (RAN2264) 3 DL-SCH/UL-SCH
1 UE with HSPA service 2 HO trigger appears; EDCH reconfigured to DCH to start CM measurements of LTE carriers
3 UE with DCH UL executes LTE ISHO
HSUPA CM feature activation is required for UE with HSPA connection to start LTE measurements
The necessary Compressed Mode (CM) transmission gap pattern parameters are implemented, allowing HSPA to LTE measurement based mobility Several times higher end user uplink throughput in handover areas (HSUPA sustained during the IS measurements) Optional UTRAN feature (separate license required)
Technical Details Triggers for RAN2264 Smart LTE Handover
Handover prioritization LTE handover is prioritized over LTE redirection - if both LTE handover (WCEL-LTEHandoverEnabled) and LTE redirection, either w/ or w/o measurements, (WCEL-SmartLTELayeringEnabled) are simultaneously enabled, LTE handover is prioritized for the UE if the following conditions are true:
1. UE capability indicates support of Inter-RAT LTE handover for the radio technology (LTE-FDD/LTE-TDD) Handover Control decides whether handover or redirection is used when a trigger (T1,T2, T3, or T4) initiates LTE measurements. If the LTE measurement is started due to handover, the decision is not changed during the measurement.
If LTE measurements does not allow handover, a new trigger is needed for LTE redirection. UE
You will trigger redirection because UE told that it does not support LTE PS 2 Handover.
Will I trigger
1 redirection or handover?
NodeB
RRC: CONNECTION SETUP
IE “Capability Update Requirement” with „EUTRA” set as in System Specific Capability Update Requirement Handover Control
RRC: CONNECTION SETUP COMPLETE
Trigger
UE CAPABILITY INFORMATION contains IEs: UE Multi-mode/Multi-RAT Capability IE and the Measurement Capability IE UE E-UTRA Capability
I am redirecting you to LTE w/o 3 measurements.* * The decision to redirect the UE with or without measurements is done according toRAN2980 Measurements based LTE Layering settings (WCEL- SmartLTELayeringEnabled and WCELLTELayeringMeasandHOActivation) and trigger type.
RNC
Technical Details Triggers for RAN2264 Smart LTE Handover
Handover prioritization LTE handover is prioritized over LTE redirection - if both LTE handover (WCEL-LTEHandoverEnabled) and LTE redirection, either w/ or w/o measurements, (WCEL-SmartLTELayeringEnabled) are simultaneously enabled, LTE handover is prioritized for the UE if the following conditions are true:
2. Streaming PS RAB is not established ???(only RAN2980 Measurement based LTE Layering can trigger LTE measurements in this case) Handover Control decides whether handover or redirection is used when a trigger (T1,T2, T3, or T4) initiates LTE measurements. If the LTE measurement is started due to handover, the decision is not changed during the measurement.
As PS Streaming RABs cannot be 2 handed over, we will try to do redirection w/ measurements
Will I trigger
1 redirection or handover?
Handover Control
Trigger
Measure LTE Frequencies and send me the 3 report.*
PS Streaming
If LTE measurements does not allow handover, a new trigger is needed for LTE redirection.
* The decision to redirect the UE with or without measurements is done according toRAN2980 Measurements based LTE Layering settings (WCELSmartLTELayeringEnabled, RNMOBISmartLTELayeringServ and WCEL-LTELayeringMeasandHOActivation) and trigger type.
Technical Details Triggers for RAN2264 Smart LTE Handover
Handover prioritization LTE handover is prioritized over LTE redirection - if both LTE handover (WCEL-LTEHandoverEnabled) and LTE redirection, either w/ or w/o measurements, (WCEL-SmartLTELayeringEnabled) are simultaneously enabled, LTE handover is prioritized for the UE if the following conditions are true:
3. Handover is not prohibited by the timer defined by the parameterRNC/FMCL-LTEMinMeasInterva (otherwise redirection w/o measurements is prioritized)
Handover Control decides whether handover or redirection is used when a trigger (T1,T2, T3, or T4) initiates LTE measurements. If the LTE measurement is started due to handover, the decision is not changed during the measurement.
If LTE measurements does not allow handover, a new trigger is needed for LTE redirection. Timer is running. We 2 cannot do the measurements. Redirection w/o measurements is going to be done.
Will I trigger
1 redirection or handover?
RNC/FMCL-LTEMinMeasInterval timer is started as at this point of time an unsuccesfull inter_RAT LTE measurements were finished Trigger appears. Handover is prevented. Possibility for redirection w/o measurements is checked. RNC/FMCL-LTEMinMeasInterval timer expiration time
Handover Control
Trigger T2
Trigger
Trigger T3
I am redirecting you to LTE w/o 3 measurements.*
* The decision to redirect the UE with or without measurements is done according toRAN2980 Measurements based LTE Layering settings (WCELSmartLTELayeringEnabled, RNMOBI- SmartLTELayeringServ and WCEL-LTELayeringMeasandHOActivation) and trigger type.
Time
Technical Details Triggers for RAN2264 Smart LTE Handover
Handover prioritization LTE handover is prioritized over LTE redirection - if both LTE handover (WCEL-LTEHandoverEnabled) and LTE redirection, either w/ or w/o measurements, (WCEL-SmartLTELayeringEnabled) are simultaneously enabled, LTE handover is prioritized for the UE if the following conditions are true:
4. Handover is not prohibited by the timer defined by the RNC/FMCL-LTEMinHoInterval parameter Handover Control decides whether handover or redirection is used when a trigger (T1,T2, T3, or T4) initiates LTE measurements. If the LTE measurement is started due to handover, the decision is not changed during the measurement.
If LTE measurements does not allow handover, a new trigger is needed for LTE redirection.
Timer is running. We 2 cannot do the handover. Let’s check if redirection is possible.
Will I trigger
1 redirection or handover?
RNC/FMCL-LTEMinHoInterval timer is started as at this point of time an unsuccesfull inter_RAT LTE measurements were finished Trigger appears. Handover is prevented. Possibility for redirection is checked. RNC/FMCL-LTEMinHoInterval timer expiration time
Handover Control
Trigger
3
Trigger T2
Trigger T3
Stay in WCDMA for now as redirection is prevented as well. Time
Technical Details Inter-system Measurements – measurements order - RAN2264 Smart LTE Handover
E-UTRA Frequency list:
LTE frequencies to be measured are based on the configured LTE neighbor frequencies and UE capabilities All frequencies where at least one LTE neighbor cell (WCEL/ADJE-object exists) is configured (value of WCEL/ADJL-
Minimum number of configured LTE neighbors PER EACH FREQUENCY
AdjLSelectFreq is ignored; it is used for redirection purposes only)
RRC Measurement Control
Maximum number of E-UTRA frequencies that can be given to UE in RRC: MEASUREMENT CONTROL message is 8. The frequencies to be measured are put in the priority order in RRC: MEASUREMENT CONTROL message. The priority order is determined by the RNC/HOPL-AdjLFreqPriority parameter. First, the priority ordered frequencies of the strongest cell, then the second strongest cell and finally the third strongest cell, depending on the size of the active set.
E-UTRA Frequency list
Maximum number of E-UTRA frequencies to be measured
1
8
Cell 1/ Cell2 neighbor Priority 1
1…8
EARFCN_1 Measurement bandwidth_1
Cell 1/Cell 2 neighbor Priority 2
Cell 3
…
EARFCN_2 Measurement bandwidth_2
WCDMA coverage is underlayed by LTE coverage – not shown for simplicity Cell 1
…
Cell 3 neighbor Priority 1
Cell 2 Active set
EARFCN_3 Measurement bandwidth_3
Serving cell
Cell 1 RSCP = -104dBm
Cell 2 RSCP = -94dBm
Cell 3 RSCP= -98dBm
Technical Details Inter-system Measurements – measurements order - RAN2264 Smart LTE Handover Core Network
Cells in active set are under DRNC:
Cell 3 neigbours are not present on the E-UTRA Frequency List IE send from SRNC to UE via RRC: SRNC
Iub
Iub NodeB
NodeB
ADDITION/SETUP message received from DRNC over Iur (this IE is included only if DRNC cell in active set has RAN2264 Smart LTE Handover license in state „On”) containing handover path to LTE
Iub
NodeB
This is possible thanks to Neighbouring E-UTRA Cell Information IE included in RNSAP: RADIO LINK
Iub
Iur
NodeB
Measurement Bandwidth equals EARFCN and Measurement Bandwidth defined for neighbour of SRNC cell
DRNC
This RRC message is based on SRNC neighbour frequencies only However, neighbour of DRNC cell can become a target cell for Smart LTE HO if its EARFCN and
E-UTRA Frequency list
Iu
Iu
MEASUREMENT CONTROL message
Cell 1 neighbor Priority 1
1…8
EARFCN_1 Measurement bandwidth_1
Cell 3
WCDMA coverage is underlayed by LTE coverage – not shown for simplicity
Cell 1 neighbor Priority 2
…
EARFCN_2 Measurement bandwidth_2
Cell 1 Cell 2 Active set
…
Cell 3 neighbor Priority 1
EARFCN_3 Measurement bandwidth_3
Serving cell
Cell 1 RSCP = -104dBm
Cell 2 RSCP = -94dBm
Cell 3 RSCP= -98dBm
Technical Details Inter-system Measurements – parameters - RAN2264 Smart LTE Handover
Parameters controling the IS LTE measurements:
The timer RNC/FMCL-LTEMinHoInterval (default 10sec) determines the minimum interval between a successful inter-RAT handover from LTE to WCDMA and the following inter-RAT handover attempt back to LTE related to the same RRC connection
Neighbor frequency search period (FMCL/LTENCarrFreqSearchPeriod [default 1.5sec]) allows UE to find and report all potential LTE neighbor carrier frequencies before the handover decision; During this period of LTE measurements, handover to LTE system is forbidden
Measurement Reporting Interval is fixed (similarly to the RAN2980 Measurement Based LTE Layering). Thus, UE sends RRC: MEASUREMENT REPORT message to RNC every 500ms
RNC/FMCL- LTEMeasAveWindow (default 3sec) determines the maximum number of measurement reports (maximum size of the sliding averaging window) from which the RNC calculates the averaged LTE RSRP and RSRQ values for the handover decision
Maximum allowed period during which LTE measurements are performed is defined by RNC/FMCL-LTEMaxMeasPeriod (default 6sec); If timer expires, RNC asks UE to stop the LTE measurements
RNC/FMCL- LTEMinMeasInterval (default 5sec) determines the minimum interval between an unsuccessful inter-RAT (LTE) measurement , and the following LTE measurement procedure related to the same RRC connection Trigger appears
Trigger appears
LTE Neighbor Carrier Frequency Search Period Minimum interval between a successful inter-RAT handover from LTE to WCDMA and the following inter-RAT handover attempt back to LTE
Measurement report received
Trigger appears LTE Neighbor Carrier Frquency Search Period
Measurement procedure is not started again within certain time period
0,5 sec
Measurement report received
Time
RNC configures compressed mode
Sliding Averaging Window
RNC configures compressed mode
Sliding Averaging Window
Technical Details Inter-system Measurements – UE reporting - RAN2264 Smart LTE Handover
UE Reporting
is 8
UE reports the measurement results in 4 frequencies (E-UTRA Carrier Frequency IE) at most Within each reported frequency, UE may report the measurement result of 4 cells (Measured E-UTRA cells IE)
E-UTRA Frequency 1…4
1…4
LTE frequencies to be measured are based on the configured LTE neighbor frequencies and UE capabilities Maximum number of E-UTRA frequencies that can be given to UE in RRC: MEASUREMENT CONTROL message
Physical cell Identity RSRP
at most
RSRQ
Thus, 16 LTE cells can be reported by the UE at most in RRC: MEASUREMENT REPORT message Physical cell Identity
UE identifies the reported cells by using the physical cell identity (Physical Cell Identity IE) UE reports RSRP (RSRP IE) and RSRQ (RSRQ IE) of each cell
RSRP
Inter-RAT handover to LTE is performed based on the measurement results received in RRC: MEASUREMENT REPORT message
RSRQ
Trigger appears Measurement period UE
NodeB
RNC
RRC: Measurement Control
RRC: Measurement Report
Sliding Averaging Window
0,5 sec
Technical Details Handover Control - RAN2264 Smart LTE Handover
Handover Control Actions
RNC uses RRC: MEASUREMENT REPORT messages to calculate particular cells’ RSRQ and RSRP levels This is used by Handover Control algorithm to decide the target cell for inter-RAT LTE handover The target cell is chosen from a group of the configured LTE neighbor cells - either under SRNC or DRNC Step 1
Reported RSRP must be equal or higher than the threshold defined by the HOPL-AdjLMinRSRPLevel parameter (main cell threshold is used)
Reported RSRQ must be equal or higher than the threshold defined by the HOPL-AdjLMinRSRQLevel
Reported Cell 1
Reported Cell 2
parameter (main cell threshold is used) Step 2
Cells with the highest priority EARFCN defined by HOPL-AdjLFreqPriority parameter is chosen (DRNC cells’
Reported Cell 3
priority is set to the lowest possible value [0])
If there is more than one EARFCN with an equal priority, the EARFCN with the highest RSRQ cell is prioritized Step 3
The cell having the highest RSRQ is chosen for the target cel for inter-RAT LTE handover.
Target LTE Cell The RNC prevents handover to the target cell for which previous attempt was unsuccessful. Timer is defined as follows:
Time_interval = (1 + Number_of_LTE_HO_fails) * RNC/FMCL- LTEMinMeasInterval
Technical Details Handover Control - RAN2264 Smart LTE Handover No support for 3G MOCN – HO to subscribers own network is not guaranteed as UE measures all defined frequency layers (no layer filtering by PLMN ID before sending them in RRC: MEASUREMENT CONTROL)
Handover Control Target LTE Cell Selection Layer 1,2,3 - MOCN Operator 1 Layer 4 - MOCN Operator 2 1. RSRP/RSRQ Must be equal or higher than the threshold HOPL-AdjLMinRSRPLevel= -128 dBm HOPL-AdjLMinRSRQLevel= -18 dB EARFCN 1 EARFCN_Priority 5 Cell1.1 RSRP/RSRQ -129/-15 Cell1.2 RSRP/RSRQ -112/-9 Cell1.3 RSRP/RSRQ -102/-6 Cell1.4 RSRP/RSRQ -106/-7 EARFCN 2 EARFCN_Priority 7 Cell2.1 RSRP/RSRQ -112/-9 Cell2.2 RSRP/RSRQ -129/-14 EARFCN 3 EARFCN_Priority 7 Cell3.1 RSRP/RSRQ -102/-6 Cell3.2 RSRP/RSRQ -101/-7 EARFCN 4 EARFCN_Priority 6 Cell4.1 RSRP/RSRQ -130/-15
Reported Cell 1
2. Highest priority EARFCN HOPL-AdjLFreqPriority EARFCN 1 EARFCN_Priority 5 Cell1.2 RSRP/RSRQ -112/-9 Cell1.3 RSRP/RSRQ -102/-6 Cell1.4 RSRP/RSRQ -106/-7
Reported Cell 2
Reported Cell 3 3. Best RSRQ cell
EARFCN 2 EARFCN_Priority 7 Cell2.1 RSRP/RSRQ -112/-9 EARFCN 3 EARFCN_Priority 7 Cell3.1 RSRP/RSRQ -102/-6 Cell3.2 RSRP/RSRQ -101/-7
EARFCN 3 EARFCN_Priority 7 Cell3.1 RSRP/RSRQ -102/-6 Cell3.2 RSRP/RSRQ -101/-7
EARFCN 3 EARFCN_Priority 7 Cell3.1 RSRP/RSRQ -102/-6
Technical Details Example - RAN2264 Smart LTE Handover
User scenario presenting typical WCMDA – LTE Interworking procedures: First, UE is handed over to WCDMA due to coverage reasons; measurements of target layer are done in advance measurements After timer expiration (minimum time interval in WCDMA) one of the Smart LTE Handover triggers appears; RNC orders UE to perform measurements; Handover Control decides to start handover procedure based on received reports and configured thresholds
Finally, UE is back in LTE network
A2 event
Smart trigger based measurements T1, T2, T3 or T4 trigger
B2 event
Handover decision
T1, T2, T3 or T4 trigger
Handover decision
WCDMA RSCP
LTEMinMeasI nterval
LTEMinHoInterval a1TimeToTriggerDeactInterMeasm
LTE RSRP -140 + threshold2a
a2TimeToTriggerActWcdmaMeas -115 + b2Threshold2UtraRscp
RNC/HOPL-AdjLMinRSRPLevel -140 + b2Threshold1Utra b2TimeToTriggerUtraMeas
UE measures WCDMA according to the list of the measurement objects
UE in LTE
LTEMaxMeasPeriod
UE measures LTE according to the list and sends reports to RNC every 500ms
UE in WCDMA
*For simplicity reasons, only one LTE frequency RSRP (without other frequency RSRP and RSRQ) are shown in graph **On LTE side, hystereses equlas 0 assumed
LTEMaxMeasPeriod
UE measures LTE according to the list and sends reports to RNC every 500ms
Handover procedure
-140 + threshold2Wcdma
RNC/HOPL-AdjLMinRSRPLevel
Handover procedure
LTE RSRP [dBm]
Smart trigger based handover
WCDMA RSCP [dBm]
Coverage based handover
UE in LTE
Time [s]
Deployment aspects Activation of RAN2264 Smart LTE Handover
Preconditions License for interdependent, mandatory feature RAN2067 LTE Interworking need to be activated
License Key: Cell Reselection to LTE Feature Code: 1755 License Type: Long-term ON/OFF licence License for RAN2264 Smart LTE Handove needs to be activated as well License Key: Smart LTE Handover Feature Code: 3414 License Type: Long-term ON/OFF licence Licenses can be activated using MML commands: ZW7M: FEA=1755:ON; for Cell Reselection to LTE LK ZW7M: FEA=3414:ON; for Smart LTE Handover LK
License Name: Cell Reselection to LTE License Type:
Long-term ON/OFF
Description:
It is possible to create and modify ADJL and HOPL objects (and respective parameters), introduced by the RAN2067 LTE Interworking if the license exist and the state is ON.
License Name: Smart LTE Handover License Type:
Long-term ON/OFF
Description:
It is possible to enable the RAN2264 Smart LTE Handover on cell basis with the WCELLTEHandoverEnabled parameter when the license exists and the state is ON.
Deployment aspects Trial Area for RAN2264 Smart LTE Handover
Recommended trial area: In order to check whether RAN2264 Smart LTE Handover works
WCDMA-LTE coverage overlapped
appropriately, trial area should be selected, so that the WCDMA network coverage and LTE network coverage is present
at lest one EARFCN should be available In order to follow UE behaviour and Handover Decision algorithm (for example: target cell selection based on frequency prioritization) with multiple EARFCNs, more than one LTE carrier should be available (configuration of neighbors should reflect that fact)
Feature can be tested in the following environments: WCDMA – LTE coverage is fully overlapped In this case, user can be quickly moved back to LTE using for
WCDMA coverage LTE coverage
example the Periodic Trigger
WCDMA – LTE coverage is not fully overlapped (LTE coverage holes) Consider unnecessary frequent CM measurements if Periodic Trigger is used and coverage holes are significant
Additionally, it is beneficial to trial this feature together with RAN2980 Measurement based LTE Layering and RAN2172 Multi-band Load Balancing as theese features are interdependant
Features use similar triggers Features share parameters Features can be used as complementary mechanisms
WCDMA-LTE coverage non- overlapped
Configuration Management Parameters – overview - RAN2264 Smart LTE Handover
New Parameters: WCEL-LTEHandoverEnabled FMCL- LTEMinHoInterval ADJE-AdjePhysicalCellId ADJE-AdjeMCC ADJE-AdjeMNC ADJE-AdjeMNCLength ADJE-AdjeENodeBId ADJE-AdjeCellId ADJE-AdjeTAC Existing Parameters: ADJL-AdjLEARFCN WCEL-MaxNumberUECmSLHO ADJL-AdjLMeasBw WCEL-LTELayerCellHSLoad HOPL-AdjLFreqPriority WCEL-SmartLTELayeringUA HOPL-AdjLMinRSRPLevel WCEL-SmartLTELayeringTSysSel HOPL-AdjLMinRSRQLevel WCEL-HCS_PRIO FMCL-LTEMeasAveWindow HOPS-AdjsHCSpriority FMCL-LTEMaxMeasPeriod RNC-LTEPeriodicTriggerTimer FMCL-LTEMinMeasInterval FMCL-LTENcarrFreqSearchPeriod WCEL-MaxNumberUEHSPACmNCHO
RNC New parameters Existing parameters
LTEPeriodicTriggerTimer
WBTS
WCEL FMCL (up to 100) FMCLId LTEMinHoInterval LTEMeasAveWindow LTEMaxMeasPeriod LTEMinMeasInterval LTENcarrFreqSearchPeriod
HOPL (up to 10) HopLId AdjLFreqPriority AdjLMinRSRPLevel AdjLMinRSRQLevel
RNMOBI (1) SmartLTELayeringServ
FMCLIdentifier LTEHandoverEnabled LTELayerCellHSLoad SmartLTELayeringUA SmartLTELayeringTSysSel MaxNumberUEHSPACmNCHO MaxNumberUECmSLHO HCS_PRIO
ADJL (up to 8) AdjLId HopLIdentifier AdjLEARFCN AdjLMeasBw
ADJE (up to 64) AdjEId AdjLIdentifier AdjePhysicalCellId AdjeMCC AdjeMNC AdjeMNCLength AdjeENodeBId AdjeCellId AdjeTAC
Configuration Management Parameterization Scenarios - RAN2264 Smart LTE Handover
Two parameterization scenarios are examined within this chapter
Back to LTE as soon as possible
LTE to WCDMA handover due to coverage reasons
WCDMA to LTE handover due to Periodic Trigger
LTE RSRP [dBm]
-140 + threshold2Wcdma (LTE configuration)
LTE RSRP
WCDMA RSCP
Time [s]
WCDMA to LTE handover due to CTS
WCDMA RSCP [dBm]
LTE to WCDMA handover due to coverage reasons
LTE RSRP [dBm]
WCDMA to LTE handover due to Periodic Trigger
WCDMA RSCP [dBm]
LTE to WCDMA handover due to coverage reasons
Back to LTE only if WCDMA is not good enough
-140 + threshold2Wcdma (LTE configuration)
LTE RSRP
WCDMA RSCP
Time [s]
Configuration Management Parameterization Scenarios: Back
to LTE as soon as possible - RAN2264 Smart LTE Handover
This scenario best suits areas where WCDMA layer is well underlayed with LTE layer; small LTE coverage holes only
Frequent periodic check of LTE layer availability and short interval between both consecutive CM measurements and incoming-outgoing HOs ensures fast move to LTE
WCDMA load criteria (delaying LTE HO) are not used CM measurements can be triggered by T1, T2, T3 or T4 events Note that this scenario may cause rise of signaling traffic LTE to WCDMA handover due to coverage reasons
WCDMA to LTE handover due to Periodic Trigger
LTE to WCDMA handover due to coverage reasons
WCEL-LTELayerCellHSLoad = 0 (cell load is not checked) WCEL-SmartLTELayeringUA = 0 (user amount not checked) RNC-LTEPeriodicTriggerTimer = 10 seconds WCEL-LTEHandoverEnabled = 8 (enabled for all triggers) FMCL- LTEMinHoInterval = 10 seconds FMCL-LTEMinMeasInterval = 4 seconds Please consider inter-RAT HO threshold values in both RANs (LTE and WCDMA) to avoid unnecessary ping-pong effect
WCDMA to LTE handover due to Periodic Trigger
LTE RSRP [dBm]
WCDMA RSCP [dBm]
WCDMA-LTE coverage overlapped
-140 + threshold2Wcdma (LTE configuration)
WCDMA coverage LTE coverage
LTE RSRP
WCDMA RSCP
Time [s]
Configuration Management Parameterization Scenarios: Back
to LTE only if WCDMA is not good enough - RAN2264 Smart LTE Handover
This scenario assumes WCDMA-LTE co-siting; additionally WCDMA-LTE coverage is not fully overlapped
Periodic check is not used at all as UE can stay in WCDMA unless it is served with good quality; thus WCDMA load criteria (delaying LTE HO) are used – proposed values should be further tuned in the field
Note that this scenario limits CM measurement attemps and consequently signaling load
WCEL-LTELayerCellHSLoad = 31 dBm (default value) WCEL-SmartLTELayeringUA = 0 (user amount not checked) RNC-LTEPeriodicTriggerTimer = N/A since trigger is disabled WCEL-LTEHandoverEnabled = 4 (enabled for T1, T2 and T3) FMCL- LTEMinHoInterval = 10 seconds FMCL-LTEMinMeasInterval = 5 seconds Please consider inter-RAT HO threshold values in both RANs (LTE and WCDMA) to avoid unnecessary ping-pong effect
WCDMA to LTE handover due to CTS
LTE RSRP [dBm]
WCDMA RSCP [dBm]
LTE to WCDMA handover due to coverage reasons
-140 + threshold2Wcdma (LTE configuration)
WCDMA coverage LTE coverage
LTE RSRP
WCDMA RSCP
Time [s]
RAN2264 Smart LTE Handover related counters M1010 Inter System Hard Handover
M1010 counters can be used for regular success rate monitoring of the outgoing LTE PS
Active set
HO (per 3G source cell)
Total duration of LTE frequency band measurements in SRNC (M1010C239) Number of measurements with CM caused by the specific trigger (M1010C240-243) Number of measurements without CM caused by the specific trigger (M1010C244-247) Number of measurements not allowing LTE HO per specific trigger (M1010C248-251) Number of LTE PS HO preparation requests per specific trigger (M1010C252-255) LTE Target Cell Cell 4
Number of completed outgoing LTE PS HOs per specific trigger (M1010C256-259) Number of events where UE sends RRC: HANDOVER FROM UTRAN FAILURE after being commanded to LTE per specific trigger (M1010C260-263)
UE fails to establish the physical channel(s) indicated in the handover command. UE reverts to the old configuration (before receiving RRC: HANDOVER FROM UTRAN COMMAND ) and transmits a failure message to the source RNC. The hard handover procedure ends and the UE resumes the normal operation as if no hard handover attempt had occurred.
Number of connection drops during LTE PS HO per specific trigger (M1010C264-267) When the UE does not respond to RRC: HANDOVER FROM UTRAN FAILURE and timer expires in the RNC, or the UE responds with RRC: CELL UPDATE and therefore the call is dropped out of Cell_DCH state.
UE
Source RNC
RRC: Handover from UTRAN Command
FAILURE during establishing the physical channel(s) indicated in handover command
Number of PS LTE HO preparation failures for NRT calls (M1010C268) RRC: Handover from UTRAN Failure
M1036 LTE Relocation RAN2264 Smart LTE Handover related counters
M1036 LTE Relocation measurement type can be used to monitor WCDMA -> LTE relocation preparation related events:
Number of LTE PS HO preparation requests (M1036C0) Number of successful LTE PS HO preparations (M1036C1) Number of LTE PS HO preparation failures (M1036C2-7) radio network layer cause transport layer cause non-access stratum cause, protocol cause miscellaneous cause non-standard cause Number of LTE PS HO preparation cancellations total number of cancellations (M1036C8) relocation cancel due to Trelocoverall timer expiration (M1036C9) relocation cancel due to Trelocprep timer expiration (M1036C10)
RNC
M1036C0 +1
M1036C2-7 +1
Core Network
RANAP: RELOCATION REQUIRED
RANAP: RELOCATION COMMAND
RANAP: RELOCATION PREPARATION FAILURE
M1036C2-7 +1 radio network layer cause transport layer cause non-access stratum cause protocol cause miscellaneous cause non-standard cause M1036C9 +1 M1036C8 +1
RANAP: RELOCATION CANCEL TrelocOverall expiry
M1036C10 +1 M1036C8 +1
RANAP: RELOCATION CANCEL TrelocPrep expiry
M1019 AutoDef LTE New counters overview
•
The AutoDef LTE measurement (M1019) measures inter system hard handover success rate from 3G to LTE per source and target cell pair
•
This measurement has been introduced in RU50 as a new measurement and provides 2 new counters
•
Both new counters have been provided with RAN2264 Smart LTE Handover functionality
M1019 AutoDef LTE RAN2264 Smart LTE Handover related counters
Monitoring WCDMA -> LTE Handover on a pair of cells basis: Detailed troubleshooting and optimization can be done with the use of these counters:
M1019C0 LTE ISHO ATTEMPTS - the number of outgoing inter-system hard handover attempts to LTE. If cells Cell 1, Cell 2 and Cell 3 are in the active set and inter-system handover to LTE Cell 4 is attempted, this counter is updated by 1 for each pair of source/target cells:
Cell 1 – Cell 4 Cell 2 – Cell 4 Cell 3 – Cell 4
Cell 3
WCDMA coverage is underlayed by LTE coverage – not shown for simplicity Cell 1
Cell 2 Active set
M1019C1 LTE ISHO SUCCESSFUL - the number of completed outgoing Serving cell
inter-system hard handovers to LTE. If cells Cell 1, Cell 2 and Cell 3 are in the active set and inter-system handover to LTE Cell 4 is attempted, this counter is updated by 1 for each pair of source/target cells:
Cell 1 – Cell 4 Cell 2 – Cell 4 Cell 3 – Cell 4 RNC
M1019C0 +1
LTE Target Cell Cell 4
RNC
Core Network
RANAP: RELOCATION REQUIRED
M1019C1 +1
Core Network
RANAP: IU RELEASE COMMAND
RAN2980: Measurement Based LTE Layering RAN3069: RSRQ-based LTE Reselection RAN2717 RAN2264: Smart LTE Handover RAN2881: WCDMA and GSM Layer Priorities
87
Introduction RAN2881 – WCDMA & GSM Layer Priorities
• The feature implements 3GPP mechanism for inter-freq or inter-RAT cell reselection using layers priorities, alternative to HCS.
• The implemented mechanism supports idle mode and connected mode (PCH,URA) prioritybased reselection WCDMA to WCDMA and WCDMA to GSM. • The operator is able to set priorities for IF layers or GSM frequencies (or groups). • Prioritization of WCDMA and GSM layers (LTE via RAN2067/RAN3069) is done via eight distinct priority levels (0÷7). • Priorities are broadcasted in SIB19 messages (first time introduced in RU20 by RAN2067). • The feature requires 3GPP Rel-8 compliant UEs & implements Rel-8 reselection criterions.
Benefits: Traffic streering in idle, PCH/URA modes
UE at U2100 cell edge may easier reselect to e.g. U900/GSM layers (number of handovers to the preferred layer in CELL_DCH is reduced)
Idle mode (PCH/URA) coverage areas of low and high frequency bands can be separated
Micro/femto reselection support
Even if signal level or quality of the serving cell (e.g. macro) is very good, the UE can reselect higher prioritized inter-frequency layer (e.g. micro, pico, femto)
Introduction & Benefits With and Without the WCDMA & GSM Layer Priorities
Without RAN2881
Sintersearch
With RAN2881
If serving cell signal is above Sintersearch, UE does not even measure f2 cells
f1, priority 5 f2, priority 6
f1
f2
• Macro dominance may prevent reselection to nearby micro/pico/femto cells (nets w/out HCS).
Threshx,high
f2 with higher priority then f1 is always measured & may be reselected if having good enough signal (above the high threshold)
• Higher prioritized cells/layers are measured always and can be reselected also in areas with good coverage of current layer (e.g. macro).
Introduction & Benefits With and Without the WCDMA & GSM Absolute Layer Priorities
Without RAN2881
With RAN2881 In any area UE can camp either on U2100 or U900 depending on relative signals and parameter settings
U2100 can be preferred in closer distance, while lower priority U900 - at coverage boundary
Threshx,high Threshserving,low 1
f1 f2
Distance (RSCP) dependent reselection possible. Higher priority
2
f1, priority 5
f2, priority 4 1 U2100 signal below low threshold and U900 good enough
• Distance-dependent areas of U2100 or U900 idle/PCH/URA coverage cannot be implemented as legacy reselection depends on relative measures/signals
Threshx,low
2 U900 signal good enough but higher priority U2100 above high threshold
• Prioritization and signal thresholds allow to geographically split areas of U2100/U900 idle/PCH/URA coverage and lower the amount of handovers to preferred layer in CELL_DCH
Interdependencies RAN2881 – WCDMA & GSM Layer Priorities
RAN2881 WCDMA&GSM Layer Priorities
exclude each other
− The feature implements 3GPP Release 8 common absolute priorities (broadcasted in SIB messages).
complementary features
RAN2067 LTE Interworking
HCS Hierarchical Cell Structure
RAN2881 is a reselection mechanism alternative to HCS: − HCS is not in use when priority based
RAN3069 RSRQ based LTE Reselection
LTE priority-based reselections: − The priority-based LTE reselection mechanism, using signal strength criteria (3GPP Rel-8) is intoduced by RAN2067. The
quality-based criteria (3GPP Rel-9) are added with RAN3069
reselection is enabled (and vice versa). Note: The complete Absolute Priority mechanism involving IF WCDMA, GSM & LTE layers is available when both: RAN2881 and RAN2067 are activated in the network.
Interdependencies General requirements
The System Information Block (SIB) number 19 enabling priority-based reselection (LTE/WCDMA/GSM) is introduced by 3GPP Release 8. Thus RAN2881 requires: 1. Release-8 capable RNC
2. Release-8 capable NodeB
AND
3. Release-8 compliant UE (with absolute layer priority capability*) AND
WCDMA&GSM Layer Priorities
SIB19
(since RU20) Absolute priorities WCDMA layer priority list LTE layer priority list GSM layer priority list
Release 8
* The support of 3GPP absolute layer priorities is mandatory for reselections towards LTE (LTE capable UE), while optional within WCDMA. UEs with absolute layer priority capability in above systems must also support absolute priority in GSM (unless it is not supported by the UE)
Technical Details Absolute Priority vs Hierarchical Structure reselection
Absolute Priority-based Reselection (APR) mechanism is a simplified version of prioritized reselection available so far in form of Hierarchical Cell Structure (HCS). Both mechanisms are standardized by 3GPP (25.304) and exclude each other. When APR is configured the HCS cannot be used & vice versa.
HCS is more complicated mechanism with priorities defined on cell level. APR use layer priorities (frequency layer for WCDMA/LTE and frequency groups for GSM). APR can be used for unconditional reselection to other layer or RAT (e.g. to LTE) or conditional, depending on new thresholds settings (mechanism useful in inter-frequency scenarios).
APR used
APR & HCS used
HCS used
Technical details Absolute Priority vs legacy cell ranking based reselection – initiation of neighbor cells measurements
Legacy rankedbased reselection
Absolute prioritybased reselection Here assumed: enabled for IF & GSM
Current cell Squal [dB]
Current cell Squal [dB]
No reselections
Higher priority layer reselections
(signal of the current cell is good enough)
(Inter-freq or inter-RAT) Sintrasearch
Sintrasearch
Legacy intra-freq reselections
Intra-freq reselections
(rank-based)
(measurement started below Sintrasearch) Sintersearch
Inter-freq reselections (measurements started below Sintersearch)
SsearchRAT
Inter-RAT reselections (measurements started below SsearchRAT)
Sprioritysearch2
Equal/lower priority layer reselections (inter-freq or inter-RAT)
Technical Details Layer priorities
When RAN2881 APR is used in the network the Operator can assign each IF WCDMA layer (carrier) or group of GSM frequencies with a number indicating how much it is preferred compared to other layers. The layer preferences applies to idle mode and PCH/URA-PCH. Eight priority levels are available, 0 being the lowest & 7 the highest.
Same RAT layers may share the same priority but it is not allowed for layers in different RATs.
Different priorities in layers
Shared priorities in layers of same RAT
Shared priorities in layers of different RATs
WCDMA, f1, prio=4 (macro)
WCDMA, f1, prio=5 (macro)
WCDMA, f1, prio=3 (macro)
WCDMA, f2, prio=5 (macro)
WCDMA, f2, prio=5 (macro)
WCDMA, f2, prio=5 (macro)
WCDMA, f3, prio=6 (micro)
WCDMA, f3, prio=6 (micro)
WCDMA, f3, prio=6 (micro)
GSM, group1, prio=3
GSM, group1, prio=3
GSM, group1, prio=3
Technical Details Layer priorities
The APR mechanism is intended only for reselection of inter-freq WCDMA or inter-RAT cells. Reselection of intra-freq cells use legacy cell ranking-based mechanism. In APR reselection the UE searches the IF/inter-RAT layers in their priority order, looking for a suitable cell. Higher priority layers are considered first. If no cell is found then IF WCDMA equal priority layers are checked. If still no result, the lower priority layers are tried (WCDMA or inter-RAT). APR may be applied to 1) IF WCDMA & GSM or 2) only IF WCDMA or 3) only GSM layers. In 2) the cell ranking reselection is used for GSM, in 3) for WCDMA. Cell ranking based reselection
Priority based reselection
WCDMA, f1, prio=5 (macro)
WCDMA, f1, prio=5 (macro)
WCDMA, f2, prio=5 (macro)
WCDMA, f2, prio=5 (macro)
WCDMA, f2, prio=5 (macro)
GSM, group1, prio=3
GSM, group1, prio=3
WCDMA, f3, prio=6 (micro) GSM, group1, prio=3
Technical Details Absolute Priority general mechanism – reselecting higher priority layer cell
When APR is in use & UE camped on WCDMA cell, the higher priority layers are considered first for inter-freq or inter-RAT neighbors search. UE always periodically measures neighbor cells on higher prioritized layers, irrespectively of current cell received power/RSCP or quality/EcNo (only the rate of measurements is influenced). The neighbor cell on higher priority layer is reselected if its signal (Srxlev) by at least Treselection (WCEL:Treselection or WCEL:TreselectionPCH) time is good enough, that is above threshold Thresh or HOPG:AdjgThreshigh).* * HOPL:AdjlThreshold x,high (HOPI:AdjiThreshigh & reselection of LTE layer is covered by RAN2067 LTE Interworking feature
The neighbor with highest signal level (Srxlev) is selected in case more then one are available on prioritized layer (3GPP Release 8). Srxlev [dB]
Treselection Current cell
AdjxThreshigh Reselect high priority cell
High priority layer cell time
Technical Details Absolute Priority general mechanism – reselecting higher priority layer cell
Higher priority IF WCDMA or inter-RAT cell is reselected when:
RAN2881 a) Srxlevnon-servingCell > HOPx:AdjxThreshigh or*
b) Squalnon-servingCell > HOPL:AdjLThreshigh2
RAN3069 by at least WCEL:Treselection or WCEL:TreselectionPCH (idle or PCH/URA) * Note: the criteria (b) is: • applicable only to LTE neighbors (3GPP SIB19 does not include the quality threshold for IF WCDMA layers) • available with RAN3069 enabled (RU50 extensions to RAN2067) & applied when both AdjLThreshigh2 & AdjLThreshlow2 are broadcasted
Technical Details Absolute Priority general mechanism – reselecting lower or equal priority layer cell
Lower priority layers are measured when current cell signal is below/equal to WCEL:Sprioritysearch1 or quality is below/equal to WCEL:Sprioritysearch2. First the IF WCDMA neighbors are searched on equal priority layers. If not found, then neighbors on lower priority layers are evaluated (IF or inter-RAT). The RESELECTION is triggered only when current cell signal dropped below min required level (WCEL:Threshservlow) or UE lost the network. The neighbor can be reselected when its signal by at least Treselection (WCEL:Treselection or WCEL:TreselectionPCH) time is good enough. That is its Srxlev is above Threshx,low threshold (HOPI:AdjiThreshlow or HOPG:AdjgThreshlow. When more neighbors on certain priority layer fulfils APR reselection condition then one with highest signal (Srxlev) is selected. Srxlev [dB]
Reselect low/equal priority cell Low priority layer cell
Treselection
Threshservlow Current cell
AdjxThreshservlow time
Technical Details Absolute Priority general mechanism – reselecting equal priority layer cell
Equal priority IF WCDMA cell is reselected when:
a) SrxlevServingCell < WCEL:Threshservlow and
Srxlevnon-serving,x > HOPI:Threshlow by at least WCEL:Treselection or WCEL:TreselectionPCH (idle or PCH/URA)
Technical Details Absolute Priority general mechanism – reselecting equal priority layer cell
Lower priority IF WCDMA or inter-RAT cell is reselected when:
a) SrxlevServingCell < WCEL:Threshservlow
RAN2881
and
Srxlevnon-serving,x > HOPx:Threshlow or*
b) SqualServingCell < WCEL:Threshservlow2 and
Squalnon-serving,x > HOPL:Threshlow2
RAN3069
by at least WCEL:Treselection or WCEL:TreselectionPCH (idle or PCH/URA) * Note: the criteria (b) is: • applicable only to LTE neighbors (3GPP SIB19 does not include the quality threshold for IF WCDMA layers) • available with RAN3069 enabled (RU50 extensions to RAN2067) and applied when both AdjLThreshigh2 & AdjLThreshlow2 are broadcasted
Technical Details Srxlev metric in WCDMA cell selection & APR reselection procedures
In 3GPP terminology Srxlev is a metric based on received P-CPICH power and determines how much the received RSCP is better then minimum level (WCEL:Qrxlevmin broadcasted in SIB3) required for cell selection (in other words, how far the UE is from entering „out of coverage” state):
Srxlev=RSCPP-CPICH _ServingCell – WCEL:QrxlevMin – max(WCEL: UEtxPowerMaxPRACH – UE_PWR_MAX,0)
Cell selection
The APR reselection mechanism use SrxlevservingCell & Srxlevnon-serving metrics comparing signal level with minimum required on given layer. That is indicating how far the UE camped on current cell is, or on target layer would be, from entering „out of coverage” state: Absolute Priority Reselection
SrxlevservingCell=RSCPP-CPICH _ServingCell – WCEL: QrxlevMin Srxlevnon-serving,FDD=RSCPP-CPICH_non-ServingCell ,FDD – HOPI: AdjiQrxlevminFDD Srxlevnon-serving,LTE=RSRPnon-ServingCell ,LTE – HOPL: AdjLQrxlevminEUTRA
Srxlevnon-serving,GSM=RXLEVnon-ServingCell _GSM – HOPG: AdjgQrxlevmin The min required signal levels for neighboring frequency layers/groups are broadcasted in SIB19.
Technical Details Srxlev metric in WCDMA cell selection & APR reselection procedures
Similarly to Srxlev, the Squal is a relative metric and determines how much the received CPICH Ec/No is better then the minimum level (WCEL:QqualMin broadcasted in SIB3) required for cell selection. In other words, how far the UE is from entering „out of coverage” state due to signal quality reason: Cell selection
Squal = Ec/NoP-CPICH _ServingCell – WCEL:QqualMin The APR reselection mechanism use SqualServingCell and Squalnon-serving metrics comparing current and neighbor quality with minimum level required on the layer. That is indicating how far UE on current layer is, or would be on the target layer, from entering „out of coverage” state: Absolute Priority Reselection
SqualServingCell = Ec/NoP-CPICH_ServingCell – WCEL:QqualMin Squalnon-serving,FDD = Ec/NoP-CPICH_nonServingCell,FDD – HOPI:AdjiQqualminFDD
Squalnon-serving,LTE = RSQRnonServingCell,LTE – HOPL:AdjLQqualminEUTRA The minimum quality levels required for neighboring frequency layers are broadcasted in SIB19.
Technical Details SIB19 content
Priority based reselection is signaled in SIB19, if enabled by license(s) & cell level parameter(s). In RU20 the LTE priority list and UTRAN serving cell info is broadcast (RAN2067). In RU50 also IF & GSM priorities and parameters can be included (this feature). WCDMA
utra-PriorityInfoList gsm-PriorityInfoList eutra-FrequencyAndPriorityInfoList
M
M Serving cell info - this feature or RAN2067 activated O Utran priority info - WCEL:WCDMACellReselection=Enabled (this feature)
O
GSM priority info - WCEL:GSMCellReselection=Enabled (this feature)
O
LTE priority info - WCEL:LTECellReselection=Enabled (RAN2067)
M O
mandatory optional
part of SIB19 (when broadcasted)
Technical Details SIB19 content / UTRAN Priority Info - mapping to new and existng parameters
SysInfoType19 │ utra-PriorityInfoList: │ │ utra-ServingCell: │ │ │ priority: 5 │ │ │ s-PrioritySearch1: 31 │ │ │ s-PrioritySearch2: 7 │ │ │ threshServingLow: 0 │ │ utran-FDD-FrequencyList: SIZE: 1 │ │ │ utran-FDD-FrequencyList(0): │ │ │ │ uarfcn: 10568 │ │ │ │ priority: 4 │ │ │ │ threshXhigh: 18 │ │ │ │ threshXlow: 4 │ │ │ │ qQualMinFDD: -16 │ │ │ │ qRxLevMinFDD: -56 │ gsm-PriorityInfoList:
WCEL
•A b s P r i o C e l l R e s e l e c • Sprioritysearch1 • Sprioritysearch2 • Threshservlow Existing parameters
• AdjiRtHopiIdentifier • AdjiUARFCN
HOPI • AdjiAbsPrioCellReselec • AdjiThreshigh • AdjiThreslow • AdjiQqualminFDD • AdjiQrxlevminFDD
Note: qRxLevMinFDD is only included if HOPI:AdjgQrxlevminFDDWCEL:Qrxlevmin qQualMinFDD is only included if HOPI:AdjiQqualminFDD WCEL:Qqualmin
ADJI
New parameters
Technical Details SIB19 content / UTRAN Priority Info – selection of parameter set
The HOPI template assigned to ADJI: RtHopiIdentifier is used to determine WCDMA absolute priority parameters broadcast in UTRAN Priority Info list of SIB19. Absolute priorities are defined per frequency layer, thus cells on same carrier should have same priority.
When neighbors on same carrier use different HOPI templates, the one with highest priority is taken (AdjiAbsPrioCellReselec), to determine absolute priority parameters for given WCDMA layer. When more HOPI with same, highest priority is used by neighbors on same carrier, the one having lower HOPI_ID number is applied. If inter-frequency absolute priority reselection mechanism is in use, then neighbors on IF layers not included in SIB19 are not considered by UE for reselection.
Layer 1, priority 5 (HOPI_1 param. used)
HOPI_ID
AdjiAbsCellReselect
1
5
2
4
3
N/A
4
5
3G cell_1 HOPI_1
3G cell_2 HOPI_4 3G cell_4
Layer 2, priority 5
AbsPrioCellReselec=5
Layer 3, not enabled for priority based reselection
3G cell_5 HOPI_3
reselection possible
reselection not possible
3G cell_3 HOPI_2
Technical Details SIB19 content GSM Priority Info - mapping to new or existng parameters
SysInfoType19 │ utra-PriorityInfoList: │ · · · · · · · · · · │ gsm-PriorityInfoList: │ │ gsm-PriorityInfo(0): │ │ │ gsmCellGroup(0): │ │ │ │ startingARFCN: 736 │ │ │ │ bandIndicator: dcs1800 │ │ │ │ followingARFCNs: │ │ │ │ │ explicitListOfARFCNs: 736, │ │ │ │ priority: 3 │ │ │ │ qRxLevMinGSM: -51 │ │ │ │ threshXhigh: 31 │ │ │ │ threshXlow: 21
ADJG • AdjgBandIndicator
• AdjgBCCH • AdjgRtHopiIdentifier Existing parameters
• AdjgQrxlevmin
HOPG • AdjgAbsPrioCellReselec • AdjgThreshigh • AdjgThreslow New parameters
Technical Details SIB19 content / GSM Priority Info – selection of parameter set
The HOPG template assigned to ADJG:RtHopgIdentifier is used to determine GSM absolute priority parameters broadcast in GSM Priority Info list of SIB19. Absolute priorities are defined per frequency group, thus any neighbor using same band indicator and BCCH should have same priority. When neighbors from same group use different HOPG templates, the one with highest priority is taken (AdjgAbsPrioCellReselec), to determine absolute priority parameters for given group.
When more HOPG with same, highest priority is used by neighbors in same group the one having lower HOPG_ID number is applied. If inter-RAT GSM absolute priority reselection mechanism is in use, then neighbors using frequencies not included in any frequency group in SIB19 are not considered by UE for reselection. HOPG_ID 1 2 3 4
Layer 1, priority 2 (HOPI_1 param. used)
2G cell_1 HOPG_4
Layer 2, priority 5
Layer 3, not enabled for priority based reselection AdjiAbsCellReselect 3 2 N/A 3
2G cell_2 HOPG_1
2G cell_3 HOPG_2
3G cell_4 AbsPrioCellReselec=5
3G cell_5 HOPG_3
reselection possible reselection not possible
Technical Details SIB19 content / 3GPP Rel9 extensions and mapping to new parameters
The 3GPP Rel9 extensions to SIB19 are part of RSRQ-based LTE reselection feature (RU50 extension of RAN2067) and are mentioned here only for information completeness (SIB19 content in RU50). SysInfoType19 │ utra-PriorityInfoList: │ gsm-PriorityInfoList: │ eutra-FrequencyAndPriorityInfoList: │ v920NonCriticalExtensions: │ │ utra-PriorityInfoList-v920ext: │ │ │ threshServingLow2: 2 │ │ eutra-FrequencyAndPriorityInfoList-v920ext: │ │ │ qqualMinEUTRA: -34 │ │ │ threshXhigh2: 32 │ │ │ threshXlow2: 31
WCEL • Threshservlow2 New RU50 parameters
• AdjLQqualminEUTRA • A d j LT h r e s h i g h 2 • A d j LT h r e s l o w 2
HOPL RAN2067 – RU50 extensions
Configuration Management Activation of inter-freq APR on cell level
Abbreviated name
WCDMACellReselection (WCEL)
Parameter name
WCDMA Cell Reselection
Description
The parameter enables the absolute priority-based WCDMA inter-frequency cell reselection for idle and connected mode (Cell_PCH, URA_PCH) UEs.
Parameter group
SystemInfo
Classification
Telecom
Range and step
Disabled (0), Enabled (1)
Default value
Disabled (0) – optional feature thus by default disabled
Category
Basic (reflects customer idle/PCH/URA mode steering strategy)
Additional info
Enable in all UTRAN in network area where APR is to be used for IF reselection Layer 1
WCDMACellReselection=0
Layer 1
Inter-freq Layer n 3G cell_1
WCDMACellReselection=1
3G current cell Legacy IF reselection 3G cell_m
3G current cell
Inter-freq Layer n 3G cell_1
APR IF reselection 3G cell_m
Configuration Management Activating of GSM APR on cell level
Abbreviated name
GSMCellReselection (WCEL)
Parameter name
GSM Cell Reselection
Description
The parameter enables the absolute priority-based GSM cell reselection for idle and connected mode (Cell_PCH, URA_PCH) UEs.
Parameter group
SystemInfo
Classification
Telecom
Range and step
Disabled (0), Enabled (1)
Default value
Disabled (0) – optional feature thus by default disabled
Category
Basic (reflects customer idle/PCH/URA mode steering strategy)
Additional info
Enable in all UTRAN in network area where APR is to be used for GSM reselection Layer 1
GSMCellReselection=0
Layer 1
GSM freq group n GSM cell_1
GSMCellReselection=1
3G current cell Legacy GSM reselection GSM cell_m
3G current cell
GSM freq group n GSM cell_1
APR GSM reselection GSM cell_m
Configuration Management Layer priorities – current cell layer priority/ reused parameter RU20 parameter (RAN2067)
Abbreviated name
AbsPrioCellReselec (WCEL)
Parameter name
Absolute priority level for cell reselection
Description
The parameter defines the absolute priority level for a cell used in absolute priority cell-reselection procedure
Classification
Telecom
Range and step
0...7, step 1
Default value
0 (by default APR not used)
Category
Basic (reflects customer’s idle/PCH/URA mode steering strategy)
Additional info
In given deployment area keep same priorities for cells in given carrier (or GSM freq group) Layer 1, priority 5
3G cell_1
3G cell_m
WCEL:AbsPrioCellReselec=5
3G current cell LTE cell_1
HOPI:AdjiAbsPrioCellReselec=4 Layer 2, priority 4
HOPG:AdjgAbsPrioCellReselec=3 2G cell_1
2G cell_n
HOPL:AdjLAbsPrioCellReselec=6 Layer 4, priority 6
Layer 3, priority 3
LTE cell_k
Configuration Management Layer priorities – neighboring layers priority / new and reused parameters
RU20 parameter (RAN2067)
Abbreviated name
AdjiAbsPrioCellReselec (HOPI), AdjgAbsPrioCellReselec (HOPG), AdjgAbsPrioCellReselec (HOPL)
Parameter name
Absolute priority for GSM cell reselection
Description
The parameter defines the absolute priority level of IF (HOPI) or inter-RAT (HOPG or HOPL) layers/freq groups in the absolute priority-based cell reselection procedure
Classification
Radio Resource Utilisation
Range and step
0...7, step 1
Default value
255 (special value indicating cell is excluded from APR and not broadcasted in SIB19)
Category
BasicBasic (reflects customer idle/PCH/URA mode steering strategy)
Additional info
In given deployment area keep same priorities for cells in given carrier (or GSM freq group) Layer 1, priority 5
WCEL:AbsPrioCellReselec=5 3G cell_1
3G current cell
3G cell_m LTE cell_1
HOPI:AdjiAbsPrioCellReselec=4 Layer 2, priority 4
HOPG:AdjgAbsPrioCellReselec=3 2G cell_1
2G cell_n Layer 3, priority 3
LTE cell_k
HOPL:AdjLAbsPrioCellReselec=6 Layer 4, priority 6
Configuration Management Equal and lower priority layers measurements – activation thresholds RU20 parameter (RAN2067)
Abbreviated name
Sprioritysearch1 (WCEL)
Parameter name
S prioritysearch1
Description
The parameter defines RSCP-based threshold used in the measurement rules for cell re-selection when absolute priorities are used. If SrxlevServingCell <= Sprioritysearch1 or SqualServingCell <= Sprioritysearch2 the UE measures neighbor cells on equal and lower priority layers/freq groups (high priority measured always)
Classification
Telecom
Range and step
0...62 dB, step 2 dB
Default value
14dB (RSCP <= - 101dBm)
Category
Basic
Additional info
Common value can be used for all UTRAN cells in the layer in given network deployment area UE does not need to measure equal & lower priority layers
SrxlevServingCell [dB]
UE should measure equal & lower priority layers
UE must measure NC on equal/lower prioritized layers when current cell RSCP drops below:
Treselection
RSCPservingCell≤ WCEL:QrxlevMin+WCEL:Sprioritysearch1
Sprioritysearch1 Time [s]
Configuration Management Equal and lower priority layers measurements – activation thresholds RU20 parameter (RAN2067)
Abbreviated name
Sprioritysearch2 (WCEL)
Parameter name
S prioritysearch2
Description
The parameter defines Ec/No-based threshold used in the measurement rules for cell re-selection when absolute priorities are used. If SrxlevServingCell <= Sprioritysearch1 or SqualServingCell <= Sprioritysearch2 the UE measures neighbor cells on equal and lower priority layers/freq groups (high priority measured always)
Classification
Telecom
Range and step
0...7 dB, step 1 dB
Default value
0 dB (by default not broadcasted in SIB19) (if value 4 -14 dB )
Category
Basic
Additional info
Common value can be used for all UTRAN cells in the layer in given network deployment area
UE does not need to measure equal & lower priority layers
SqualServingCell [dB]
UE should measure equal & lower priority layers
UE must measure NC on equal/lower prioritized layers when current cell EcNo drops below:
Treselection
EcNoservingCell≤ WCEL:QqualMin+WCEL:Sprioritysearch2
Sprioritysearch2 Time [s]
Configuration Management The maximum rxlev threshold in current cell allowing APR reselection of IF/inter-RAT neighbor cells on equal/lower priority layer RU20 parameter (RAN2067)
Abbreviated name
Threshservlow (WCEL)
Parameter name
Thresh serving low
Description
The parameter specifies the limit for Srxlev in the serving cell below which the UE may perform cell reselection to a cell on a lower absolute priority layer (or equal priority inter-frequency layer) .
Classification
Telecom
Range and step
0...62 dB, step 2 dB
Default value
2dB
Category
Basic
Additional info
Common value can be used for all UTRAN cells in the layer in given network deployment area Reselect low/equal priority cell Srxlev [dB]
Treselection current cell
Threshservlow
neibour on equal/lower priority layer
AdjxThreshservlow
time
Configuration Management The minumum rxlev threshold in equal/lower priority inter-freq or inter-RAT neighbor cell required for APR reselection RU20 parameter (RAN2067)
Abbreviated name
AdjiThreslow (HOPI), AdjgThreslow (HOPG), AdjLThreslow (HOPL)
Parameter name
Threshold low (for inter-freq or GSM or LTE cell reselection)
Description
The parameter defines the Srxlev-based (RSCP/3G or GSM RSSI/2G or RSRP/LTE) threshold used by the UE for cell reselection towards a lower absolute priority layer (3G/2G/LTE) when absolute priorities are applied.
Classification
Radio Resource Utilisation
Range and step
0...62 dB, step 2 dB
Default value
0 dB (HOPI, HOPG) and 4dB (HOPL)
Category
Basic
Additional info
Common value can be used for all cells in the layer in given network deployment area
Srxlev [dB]
current cell neibour on equal/lower priority layer
Reselect low/equal priority cell
Treselection
Threshservlow
AdjxThreshservlow time
Configuration Management The minumum rxlev threshold in high priority neighbor cell required for APR reselection RU20 parameter (RAN2067)
Abbreviated name
AdjiThreshigh (HOPI), AdjgThreshigh (HOPG), AdjLThreshigh (HOPL)
Parameter name
Threshold high (for inter-freq or GSM or LTE cell reselection)
Description
The parameter defines the Srxlev (RSCP/3G or GSM RSSI/2G or RSRP/LTE) based threshold used by the UE for cell reselection towards a higher absolute priority layer (3G/2G/LTE) when absolute priorities are applied.
Classification
Radio Resource Utilisation
Range and step
0...62 dB, step 2 dB
Default value
0dB (HOPI, HOPG) and 18dB (HOPL)
Category
Basic
Additional info
Common value can be used for all 3G/GSM/LTE neighbor cells in the layer in given network deployment area
Srxlev [dB]
Treselection
Low priority cell
AdjxThreshigh Reselect high priority cell
High priority cell time
Configuration Management The minimum RSCP for cell selection in neighbor inter-freq layer cell in APR procedure
Abbreviated name
AdjiQrxlevminFDD (HOPI)
Parameter name
QrxlevminFDD for inter-frequency cell reselection
Description
The parameter defines the minimum required CPICH RSCP level of the neighboring UTRA frequency for interfrequency absolute priority based cell reselection.
Classification
Radio Resource Utilisation
Range and step
-119...-25 dBm, step 2 dBm
Default value
-115 dBm
Category
Basic
Additional info
Common value can be used for all UTRAN cells in the layer in given network deployment area. Parameter taken from HOPI corresponding to ADJI:AdjiRtHopiIdentifier. The value should be aligned with WCEL:Qrxlevmin and if equal it is not broadcasted in SIB19
Srxlevnon-serving,UTRAN=RSCPP-CPICH_non-ServingCell – HOPx:AdjiQrxlevminFDD
Configuration Management The minimum RSCP for current cell cell selection Reused parameter
Abbreviated name
QrxlevMin (WCEL)
Parameter name
Minimum required RX level in the cell
Description
The parameter defines the minimum required RX level in the cell (basic cell selection parameter)
Classification
Telecom
Range and step
-119...-25 dBm, step 2 dBm
Default value
-115 dBm
Category
Basic
Additional info
Common value can be used for all UTRAN cells in the layer in given network deployment area. Parameter used by UE in cell selection and ARP reselection to derive Srxlev value of current/serving cell
SrxlevservingCell=RSCPP-CPICH _ServingCell – WCEL:QrxlevMin
Configuration Management Minimum required EcNo for current cell selection Reused parameter
Abbreviated name
QqualMin (WCEL)
Parameter name
Minimum required quality level in the cell
Description
The parameter defines the minimum required quality level in the cell (Ec/No).
Parameter group
SystemInfo
Classification
Telecom
Range and step
-24...0 dB, step 1 dB
Default value
-18 dB
Category
Basic
Additional info
Common value can be used for all UTRAN cells in the layer in given network deployment area. Parameter used by UE in cell selection and ARP reselection to derive Squal value of current/serving cell
SqualservingCell=EcNoP-CPICH _ServingCell – WCEL:QqualMin
Configuration Management
Main Menu
Minimum required RXLEV for GSM neighbor cell selection Reused parameter
Abbreviated name
AdjgQrxlevMin (HOPG)
Parameter name
Cell Re-selection Minimum RX Level
Description
The parameter determines the minimum required RSSI level which the measurement result of the GSM neighbor cell must exceed before the cell re-selection is possible
Classification
Radio Resource Utilisation
Range and step
-115...-25 dBm, step 2 dBm
Default value
-101 dBm
Category
Basic
Srxlevnon-serving,GSM=RXLEVnon-ServingCell _GSM – HOPG:AdjgQrxlevMin
Configuration Management SIB19 scheduling
Abbreviated name
SIB19Priority (RNC)
Parameter name
Priority for SIB19
Description
This parameter defines the priority of the System Information Block 19, which is used by the scheduling algorithm in the RNC to give precedence to the SIB. 1 = highest priority, 4 = lowest priority
Parameter group
SystemInfo
Classification
Telecom
Range and step
1...4, step 1
Default value
4
Category
Advanced
Additional info
See https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/433812970 for more details on SIB scheduling
Configuration Management Time to trigger for cell reselection procedure Reused parameters
Abbreviated name
Treselection, TreselectionPCH (WCEL)
Parameter name
Cell reselection triggering time (PCH)
Description
The UE triggers the reselection of a new cell if the cell reselection criteria are fulfilled during the Treselection time interval while in idle mode (or TreselectionPCH while in CELL_PCH or URA_PCH states)
Classification
Telecom
Range and step
0...31 sec, step 1 sec
Default value
2 sec
Category
Advanced
or
or
Srxlev [dB]
Srxlev [dB]
AdjxThreshigh
Reselect high priority cell
Threshservlow AdjxThreshservlow
time
Reselect low/equal priority cell time
Deployment aspects Feature licensing
Licensing:
• This feature belongs to application software (ASW) and is under license key management.
• WCDMA and GSM Layer Priorities license is required – License key name „ WCDMA and GSM Layer Priorities "
– Feature code: 4781 – License type: Long-term on/off license.
• The license can be activated for example using MML command: ZW7M: FEA=4781:ON;
Deployment aspects Feature activation (1/2)
Activate license for RAN2881 − RU04781 WCDMA and GSM Layer Priorities LK
Configure parameters relevant to your scenario (IF or/and GSM ARP), that is: o Set layer priorities for UTRAN cells according to layering reselection strategy, if not done yet*: − WCEL:AbsPrioCellReselec = 1÷7 (keep same value for all UTRAN cells in the layer)
o Set layer priorities for neighbor cells according to layering reselection strategy: − Rt** HOPx:AdjxAbsPrioCellReselec = 1÷7 (keep same value for all cells in same layer or frequency group)
o If equal/lower priority layers exist, set non-zero Ssearchpriority1 & 2 , if not done yet*: (it is suggested to keep the relation: SsearchRAT≤Ssearchpriority2< Sintrasearch) − WCEL: Ssearchpriority1=7 (measurements of equal/lower prio layers starts when current cell RSCP falls below QrxlevMin+7dB)
− WCEL: Ssearchpriority2=4 (measurements of equal/lower prio layers starts when current cell Ec/No falls below QqualMin+4dB)
o If APR for WCDMA is to be enabled, align minimum required rxlevels for IF neighbors (HOPI:AdjiQrxlevminFDD and AdjiQqualminFDD with corresponding WCEL:QrxlevMin and QqualMin) * RAN2067 (LTE Interworking) not activated ** HOPx template identified by ADJx:RtHopxIdentifier assigned to given neigbour cell (x={I,G,L} for WCDMA, GSM or LTE respectively
Deployment aspects Feature activation (2/2)
o Set to non-zero value, the max signal level of the current cell, at which neighbors on equal or lower priority layers can be reselected (if not yet done)*: − WCEL:Threshservlow=4 (current cell RSCP must be below QrxlevMin+4*2dB to let equal/lower prio layers reselection)
o Set to non-zero value, the min signal level at which neighbors on higher priority layers can be reselected (common value shared by neighbors on same priority layers): − Rt HOPI: AdjiThreshigh=10 (WCDMA IF high prio NC needs RSCP better then AdjiQrxlevminFDD+10*2dB to be reselected) Note: if GSM is decided as higher priority layer (very unlikely strategy) then set non-zero HOPG:AdjiThreshigh. In case LTE layers exists & are higher prioritized, RAN2067 needs to be activated & related parameter HOPL:AdjLThreshigh set (optionally also HOPI:AdjLThreshigh2, if RU50 rel9 quality criterions are to be used).
o Set to non-zero value, the min signal level at which neighbors on equal or lower prioritised layers can be reselected (common value shared by same priority layers): − Rt HOPI: AdjiThreshlow=5 (WCDMA equal/lower priority NC need RSCP better then QrxlevMinFDD+5*2dB to be reselected) − Rt HOPG: AdjgThreshlow=5 (GSM lower priority NC need RXLEV better then HOPG:AdjgQrxlevmin+5*2dB to be reselected)
Enable APR relevant to your scenario (if LTE to be considered, activate RAN2067): − WCEL:WCDMACellReselection=Enabled (1) for inter-frequency priotity-based reselections − WCEL:GSMCellReselection=Enabled (1) for GSM priority-based reselections * RAN2067 (LTE Interworking) not activated
Deployment aspects Parameters relations worth fllowing
To avoid inconsistent settings of APR reselection thresholds or measurement activation thresholds, it is suggested to keep the following parameter relations: WCEL(high):Sprioritysearch1 > 2* WCEL(high):Threshservlow
WCEL(high):Threshservlow < HOPI(high):AdjiThreshigh High priority layer cell WCEL(high):Threshservlow
HOPI(high):AdjiThreshigh
Low priority layer cell
HOPI(low):AdjiThreslow
At the time when current cell RSCP drops below reselection threshold for equal or lower priority layers, the corresponding measurements were already started due to low signal level (may be independently started due to low Ec/No - Sprioritysearch2) The min RSCP at which higher prio layer cell is reselected (configured in low prio layer cell) is greater then max level at which equal or lower prio layer cell can be reselected (configured in high prio layer cell)
WCEL(low):Threshservlow
HOPI(low):Threshlow < HOPI(high):AdjiThreshigh
The min RSCP at which lower prio layer cell is reselected (configured in high prio layer cell) is lower then min level required to reselect high priority layer cell (configured in low prio cell)
Deployment aspects Configuration examples use cases (1/2)
Use case 1: Reselection of micro / femto IF layer in areas of strong macro layer signal Layer F1 (priority 4)
APR IF (≥Rel8 UE:s)
Layer F2 (priority 5)
APR (micro) or HCS (femto) IF reselections
Threshx,high
Parameter
Macro layer
Micro layer
or Femto layer
Enabled
Enabled
N/A*
4
5
N/A*
5 (micro/femto NC)
4 (macro NC:s)
N/A*
SsearchPriority1
7 (-108dBm)
14 (-101dBm)
N/A*
SsearchPriority2
4 (-14dB)
4 (-14dB)
N/A*
Threshservlow
0 (no IF/IS macro)
5 (-105dBm)
N/A*
AdjiThreshigh
10 (-95dBm)
10 (-95dBm)
N/A*
AdjiThreshlow
5 (-105dBm)
7 (-101dBm)
N/A*
WCDMACellReselection AbsPrioReselec AdjiAbsPrioReselec
* This are settings in femto RAN, where APR may be not available. On the femto side the usage of HCS is recommended for reselections towards macro (& forcing UE stay in femto)
In legacy reselection mechanism, IF neighbors are not measured unless current cell signal diminishes (Squal falls below Sintersearch). Increased Sintersearch (to force IF measurements) boosts UE battery consumptions (Sintrasearch also increased). The IF micro cells or femto cells deployed in area of strong macro cell signal may be not reselected even though layer is preferred by Operator’s strategy. In legacy mechanism, the HCS (Hierarchical Cell Structure) may be used to force micro/femto reselection however many operators do not want the feature activated in macro layer (less NCs in SIB11, which is not a problem in femto layer; usually few NCs only). The IF APR with higher prioritized micro/femto layers can be used to force preferred layers reselection (no drawback of HCS, though it’s applicable to ≥Rel-8 UEs). In case of femto layer reselection, the activation of RAN2581 Femto HO Control shall also be considered.
Deployment aspects Configuration examples use cases (2/2)
Use case 2: Separation of idle/PCH/URA coverage areas of different bands (high band close to cell, low band at the border)
The strategy may be implemented in connected mode using RAN2172 RU30 feature (MBLB). The APR complements the MBLB by adjusting UE location in multiband network in idle mode, thus lowering necessary MBLB relocations (lower signaling load in the network).
Threshx,high Threshserving,low 1
Some layering strategies consider U900 band to be reserved for UEs located too far from U2100 cells.
2
Priority 5 Priority 4
The geographical split is performed using RSCP-based thresholds and priorities. RSCP is an indicator of UE’s distance from the currently serving cell. Parameter
U2100 layer cells
U900 layer cells
Enabled
Enabled
5
4
4 (U900 NC:s)
5 (U2100 NC:s)
SsearchPriority1
25 (-90dBm)
7 (-108dBm)
SsearchPriority2
4 (-14dB)
4 (-14dB)
WCDMACellReselection
Threshx,low
AbsPrioReselec
AdjiAbsPrioReselec
1 U2100 signal below low threshold and U900 good enough
Threshservlow
10 ( -95dBm)
4 (-105dBm)
2
AdjiThreshigh
11(-93dBm)
11 (-93dBm)
AdjiThreshlow
0 (-115dBm)
5 (-105dBm)
U900 signal good enough but higher priority U2100 above high threshold
Deployment aspects Configurations options with concurently enabled legacy and APR reselections mechanisms
A) Absolute priority reselection enabled for IF layers (GSMCellReselection=Disabled)
Current cell Squal [dB]
Higher priority IF layer reselection
Sintrasearch
WCDMA, f1, prio=5 (macro) Priority-based reselection WCDMA, f2, prio=5 (macro) Cell ranking-based reselection
WCDMA, f3, prio=6 (micro)
Sprioritysearch2
SinterRAT
GSM
B) Absolute priority reselection enabled for inter-RAT layers (WCDMACellReselection=Disabled)
Cell ranking-based reselection Priority-based reselection
Current cell Squal [dB]
WCDMA, f1
Sintrasearch
WCDMA, f2=prio 5
Sintersearch
WCDMA, f3 GSM, prio 3 LTE, prio 7 (RAN2067)
Sprioritysearch2
Legacy intra-freq reselection Equal/lower IF priority layer res.
Legacy GSM reselection
Higher priority IS layer reselection Legacy intra-freq reselection Legacy IF reselect. Equal/lower priority IS layer reselection
The order in which legacy and APR IF & inter-RAT reselections are considered in case conditions fullflled simultaneously is UE vendor specific (not determined by 3GPP)
Compliant aspects
Absolute Priority-based Reselection was introduced first to 3GPP Release 8 specifications. Main document is 25.304. Supplementary requirements are included in 25.133 and 25.331 specifications. NSN implements common absolute priority reselection that is using parameters broadcasted in System Information Blocks (mainly new SIB19). Dedicated UE priorities are not in the scope. Release 8 & 9
The absolute priority mechanism was first implemented in RU20. The 3GPP Release 8 absolute priority reselection criteria were introduced for inter-RAT LTE layers and WCDMA layer (serving layer) with the RAN2067: LTE Interworking feature. This feature (RAN2881) extends available reselection scenarios by WCDMAIF WCDMA & WCDMA GSM.
RU50 also extends APR reselection criteria by 3GPP Release 9 current and target cells quality (the Release 8 criteria use signal level). The quality criteria are implemented in RAN3069 (RSRQ-based LTE reselection).