Idle Mode Mobility
Short Description
Idle Mode Mobility...
Description
Nokia Academy LTE Radio Parameters 2 [FL15a] Idle Mode Mobility
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Module Objective After completing this learning element, the participant should be able to describe discuss and analyze:
•Parameters associated to idle mode mobility load balancing
Index •Idle Mode Mobility Load Balancing •Load triggered Idle Mode Mobility Load Balancing •Measurement based Idle Mode Load Balancing
Index •Idle Mode Mobility Load Balancing •Load triggered Idle Mode Mobility Load Balancing •Measurement based Idle Mode Load Balancing
Idle Mode Mobility Load Balancing Load Balancing Features Overview Intra-Frequency
Inter-Frequency Intra-LTE
Inter-RAT
Idle Mode Load Balancing Features
LTE487 – Idle Mode Load Balancing (RL50/RL35TD/RL50FZ) LTE1677 – Idle Mode Load Balancing Extensions (RL60/RL45TD) LTE2050 – Load Triggered Idle Mode Load Balancing (RL70/RL55TD) LTE2051 – Measurement Based Idle Mode Load Balancing (FL15A/TL15A)
LTE 487 Idle Mode Mobility Load Balancing RL50 LTE1677 Idle Mode Mobility Load Balancing Extensions RL60 A percentage of UEs switching from connected to idle state are provided dedicated cell reselection priorities for different frequency layers and RATs via RRC Release message Percentage of UEs
33%
4. UEs uses the IMMLB priorities for reselection
1. UEs connected to Freq1
Dedicated Cell Reselection Priorities
Broadcasted Cell Reselection Priorities Freq 1
High
Freq 2
Low
Low
Freq 2
High
Low
Freq 2
High
2. UEs are released by the cell Broadcasted Cell Reselection Priorities
Dedicated Cell Reselection Priorities Freq 1
Freq 1
Freq1 3. Selected UEs are sent IMMLB priorities
Freq 1
High
Freq 2
Low
Broadcasted Cell Reselection Priorities Freq 1
High
Freq 2
Low
Freq2
LTE 487/LTE1677 Idle Mode Mobility Load Balancing/Extensions Candidate UE selection
Each time a UE is released without redirection, the ratio of RRC connection release messages with idlemodemobilityConfigInfo IE configured with RRC connection release messages is compared with the configured idleLBPercentageOfUe
This is done at the object level (LNCEL, MOPR or MODPR) selected by the IMMLB algorithm
Check assumes that UE to be released is sent idleModeMobility ControlInfo
# of RRC connection release messages with idleModeMobilityControlInfo
idleLBPercentageOfUe # of RRC connection release messages
If the condition is met, the RRC connection release message is configured to include the idleModeMobilityControlInfo IE and UE would use dedicated IMMLB priorities in cell reselection
Otherwise, the RRC connection release would be constructed without the idleModeMobilityControlInfo IE and UE would use SIB priorities in cell reselection
Idle mode mobility balancing extensions LTE1677 – Idle Mode Mobility Load Balancing Extensions (RL60) -
Weighted Round Robin (WRR)
-
In RL60 the Cell does not have configured the absolute dedicated priorities, instead a weighting factor is set and available alternative layers chosen at random via WRR and dedicated priority for this layer is then set =max. EXAMPLE •
•
Random value from the range [0;1] is generated. -
[0;0.5] then frequency f 1 will be chosen as a main target for IMMLB; Dedicated Cell Reselection Priority for f 1 7
-
(0.5;0.75] then frequency f 3 will be chosen as a main target for IMMLB; Dedicated Cell Reselection Priority for f 3 7
-
(0.75;1] then frequency f 4 will be chosen as a main target for IMMLB; Dedicated Cell Reselection Priority for f 4 7
Please note that frequency/layer configured with the highest IMMLB weight (in this example f 1) in relation to other frequency/layers has the highest probability of being selected as a main target for IMMLB
•
IMMLB weights are used only to determine which frequency will be selected as main target for IMMLB Generated value 0.76 means that f 4 will get priority 7 in IMMCI
Example: Value 0.76 was randomly generated
p1WRR(f 1 ) = 0.5
0
p2 WRR(f 3 ) = 0.25
0.5
f 1 = [ 0;0.5 ]
0.5
0.75
f 3 = ( 0.5;0.75 ]
p3WRR(f 4 ) = 0.25
0.75
f 4 = ( 0.75;1 ]
1
LTE 487/LTE1677 Idle Mode Mobility Load Balancing/Extensions Parameters • •
actIdleLB idleLBPercentageOfUes balancing moimpId modimpId T320 For MODIMP, MOIMP, LNCEL
• • • • • • • • • • • • • • • •
Activation of idle mode load balancing (IdleLB) MODPR, MOPR, LNCEL Percentage of UE for idle mode load Idle mode mobility profile identifier Idle mode mobility default profile identifier LNCEL Timer T320
dlCarFrqEut EUTRA carrier freq for IMMLB utrFddCarFrq UTRA-FDD carrier frequency for IMMLB cdmaRttBdCl CDMA 1xRTT band class for IMMLB cdmaHRPDBdCl CDMA HRPD band class for IMMLB g eranB andInd GERAN carrier frequency band for IMMLB g eranC arFrqIdleModeL GERAN carrier frequency list for IMMLB idleLBCellReSelPWeight Cell Reselection Priority for IMMLB (LNC E L only) idleLBEutCelResWeight EUTRA carrier frequency priority for IMMLB idleLBUtraFddCelResWeight UTRA-FDD carrier frequency priority for IMMLB idleLBRttCelResWeight CDMA 1xRTT band class priority for IMMLB idleLBHrpdCelResWeight CDMA HRPD band class priority for IMMLB idleLBGeranCelResWeight GERAN carrier frequency priority for IMMLB
Index •Idle Mode Mobility Load Balancing •Load triggered Idle Mode Mobility Load Balancing •Measurement based Idle Mode Load Balancing
LTE2050 Load Triggered Idle Mode Load Balancing •
Idle Mode Mobility Load Balancing (IMMLB) refers to the inclusion of Dedicated Priorities within the RRC Connection Release message
•
Load balancing is achieved by allowing:
•
•
some UE’s use the Dedicated Priorities broadcast within the SIB
•
some UE’s use Dedicated Priorities included within their RRC Connection Release
IMMLB has evolved with each software release
RL40 •
•
Load balancing across LTE carriers
RL50 – LTE487 •
Introduction of interRAT capability
RL60 – LTE1677 •
Introduction of Absolute Priority Weights
RL70 introduces the capability to trigger IMMLB only when the load becomes high •
rather than always triggering the feature
LTE2050 Load Triggered Idle Mode Load Balancing • The load threshold used to trigger Idle Mode Mobility Load Balancing is configured using the idleLBCapThresh parameter • This parameter defines a percentage Composite Available Capacity (CAC)
• CAC = 100 % corresponds to an unloaded cell • CAC = 0 % corresponds to a fully loaded cell • Configuring a value of 100 % provides the same functionality as RL60, i.e. the feature i s always triggered
LNCEL; idleLBCapThresh Idle mode load balancing capacity threshold 0 to 100 %, Default: 100
LTE2050 Load Triggered Idle Mode Load Balancing Composite Available Capacity (CAC) •
Triggering based upon load uses the Composite Available Capacity (CAC) •
load balancing is triggered when CAC <
idleLBCapThresh •
CAC is calculated from the downlink GBR, non-GBR and PDCCH loads
•
The calculation is completed in 3 steps •
Relative Load = Measured Load / Target Load
• Available Capacity = 100 % - Relative Load •
Composite Available Capacity = Min(Available Capacities) Available Capacity calculated for GBR, non-GBR and PDCCH
Loadsettings; mlbEicicOperMode Mode for calculating the CAC in load bal. and eICIC nonGbrOnly (0), nonGbrPdcch (1), allUes (2) Default : AllUes
LTE2050 Load Triggered Idle Mode Load Balancing Triggering • load balancing is triggered when CAC < idleLBCapThresh
LNCEL; idleLBCapThresh Idle mode load balancing capacity threshold 0..100% Default: 100%
Cell load max 100% Target load 60%
Rel load 100% CAC 50%
CAC 50% < idleLBCapThresh 90% therefore IMLB = True
idleLBCapThresh 90%
LTE2050 Load Triggered Idle Mode Load Balancing •
Triggering based upon load uses some of the parameters from the loadSettings parameter structure
•
The relevant parameters are:
nomNumPrbNonGbr • targetLoadGbrDl • targetLoadNonGbrDl • targetLoadPdcch •
New object for common load balancing parameters
LNCEL - loadSettings cellCapClass mlbEicicOperMode nomNumPrbNonGbr targetLoadGbrDl targetLoadNonGbrDl targetLoadPdcch ulCacSelection ulStaticCac
Index •Idle Mode Mobility Load Balancing •Load triggered Idle Mode Mobility Load Balancing •Measurement based Idle Mode Load Balancing
LTE2051: Measurement based Idle Mode Load Balancing
• LTE2051 is an extension of IMMLB algorithm
FL/TL15A
• From FL/TL15A onwards eNB may validate if selected main target frequency layer has sufficient power (RSRP) and/or quality (RSRQ) • Starting from FL/TL15A it is possible to avoid steering UEs to worse cells in terms of RSRP as well as avoid reselections to congested cells (RSRQ) • Selected main target frequency layer is checked against absolute configurable thresholds as well as against serving cell RSRP/RSRQ • LTE2051 can be used together with LTE2050, but LTE2050 is not a prerequisite
LTE2051: Measurement based Idle Mode Load Balancing Load Triggered Idle Mode Load Balancing •
The feature is split into 5 f unctions; 1) Load supervision and CAC calculation: •
Measurements of source cell DL CAC (CAC S)
2) Check if IMMLB should be triggered •
Source cell CAC is compared with configured load threshold (LNCEL:idleLBCapThresh) that defines an IMMLB trigger point
3) IMMLB Objects Selection • According to configuration, proper IMMLB object is selected, from which percentage of UEs as well as IMMLB weights are taken 4) Candidate UE selection •
Connected
For each UE that is being released, it is verified if IMMCI should be added
5) IMMCI creation •
WRR (selection of main target frequency layer) [LTE487/LTE1677]
•
Main target validation (A4 measur ements of main target) [LTE2051]
•
IMMCI is filled up with frequency layers and assigned dedicated priorities [LTE487/LTE1677]
Load supervision and CAC calculation Check if IMMLB should be triggered
L T E 2 0 5 0
IMMLB Objects Selection Candidate UE Selection IMMCI creation LTE2051
Idle
L T E 4 8 7 / 1 6 7 7
I d l e M o d e M o b i l i t y L o a d B a l a n c i n g
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI* Creation • Overview of enhanced Idle LB procedure is illustrated below (LTE2051 part is included)
START
1.UE is a candidate for LB 2.IMMLB object(s) is/are selected for UE, IMMLB weights can be derived from proper structure
STEP 2
STEP 1
STEP 4
STEP 3
STOP = NO IMMCI is sent to UE No
STEP 5 List of frequency layers, based on selected IMMLB object is created. This is done for the Main target frequency selection
Is there any frequency on list?
Weighted Round Robin Algorithm is used to determine the main target for IMMLB Yes
Main target validation RSRP/RSRQ of cells of main target are checked
All criteria fulfilled?
Yes No
STEP 7 IMMCI list is filled up:
STOP = NO IMMCI is sent to UE
1)Main target frequency layer is added with assigned priority 7 2)All frequencies from STEP 6 with SIB priority lowered by one 3)t320 timer is added
LTE2051 STEP 6
1)Second list containing frequency layers configured in selected IMMLB object is created. 2)Main target frequency is removed (if present) 3)Frequency layers that not configured for SIB broadcast are removed
STOP
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI Creation -
STEP 4: Main target validation (LTE2051) When LTE2051 is activated (LNBTS:actMeasBasedIMLB = true), eNB considers RSRP/RSRQ validation of the main target frequency layer, provided that: •Selected main target frequency layer is inter-frequency LTE layer
-
If serving cell`s frequency layer is selected as main target or frequency layer that belongs to different RAT, quality check (RSRP/RSRQ) for the primary target is not done (IMMCI with dedicated priorities is sent according to LTE487/LTE1677 rules)
•Selected LTE target frequency layer is configured to be measured (IRFIM:enableA4IMLB = true)
FL/TL15A Only primary target that is an inter-frequency LTE layer may be validated with LTE2051
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI Creation -
STEP 4: Main target validation (LTE2051) Idle LB algorithm is working just before RRC Connection Release message is built for UE •LTE2051 requires A4 measurements to be done before RRC Connection Release is sent to UE • A4 measurements are possible only in RRC Connected state •To facilitate A4 measurements for Idle LB needs, prolonged RRC Connected state is required -
•
e t a t s C R R
RRC Connected
1
A4 supervision timer (LNBTS:reportTimerIMLBA4) is controlling both prolonged RRC Connected state as well as A4 measurement period
2 3
RRC Idle time
Normal data activity (signalling or user data) can happen in prolonged RRC Connected state
Just before RRC Connection Release with or without IMMCI is sent, eNB has to verify inactivity state again. If any activity was recorded, RRC Connection Release procedure is stopped
Note: 1 InactivityTimer is running (LNCEL:InactivityTimer) 2 RRC Connected phase is prolonged as A4 supervision timer is running
3 RRC Connection Release with or without IMMCI, depending on Idle LB algorithm decision
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI Creation -
STEP 4: Main target validation (LTE2051) Once A4 MR is received, TCL is created •Cells belonging to TCL are checked against RSRP and/or RSRQ thresholds: -If RSRP parameters are configured (IFRIM:minRsrpIMLB, IRFIM:minDeltaRsrpIMLB): •RSRP of potential target (RSRPT) is checked against absolute RSRP threshold IFRIM:minRsrpIMLB •RSRP of each potential target (RSRPT) is checked against serving cell RSRP (RSRPS), i.e. whether RSRPT > RSRPS + IRFIM:minDeltaRsrpIMLB
-If RSRQ parameters are configured (IFRIM:minRsrqIMLB, IRFIM:minDeltaRsrqIMLB): •RSRQ of potential target is checked against absolute RSRQ threshold IFRIM:minRsrqIMLB •RSRQ of each potential target (RSRQT) is checked against serving cell RSRQ (RSRQS), i.e. whether RSRQT > RSRQS + IRFIM:minDeltaRsrqIMLB
-
STEP 5: Main target validation (LTE2051) If all abovementioned criteria are met for at least one cell, IMMCI will be added to RRC Connection release, otherwise RRC Connection release is sent without dedicated priorities
Note: If IMMCI is not sent after the primary target validation , #of RRC Connection Release message s with idleModeMobilityControlInfo is not decremented!
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI Creation -
STEP 6: Gathering frequency layers that will fulfill the IMMCI If IMMCI is still to be sent, i.e. the primary target layer is already determined [verified by measurements or not], second list of frequency layers is created •
CASE A: Selected objects MOPR + MOIMPs (the same approach for MODPR + MODIMPs)
-
Serving cell frequency layer is included in Frequency List only if it is configured in MODIMP/MOIMP
•
CASE B: LNCEL+(LNCEL,IRFIM) or LNCEL+(LNCEL,IRFIM,UFFIM,CDFIM,GFIM) [when LNBTS:actIdleLB = true]
-
When LNCEL is selected as IMMLB object for UE, then serving cell frequencyis always included in the Frequency List
Frequency List
MOPR
OR MOIMP-1 MOIMP-X
FREQ
SIB PRIO
f 1
3
f 3
5
f 5
2
f 6
6
LNCEL GFIM CDFIM UFFIM IRFIM
STEP 4: Frequency List contains all frequencies and priorities for SIB broadcast configured in IMMLB object(s), excluding: • frequency that is selected as main target for LB • frequencies not supported by UE • frequencies that have not configured Cell Reselection Priority for SIB broadcast
STEP 6
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI Creation -
STEP 7: IMMCI is filled up •
Main target frequency layer is added to IMMCI with the highest
priority 7 •
Frequencies from Frequency List (created in STEP 6) with SIB priority FREQ
SIB PRIO
of main target that could appear (priority value 7 in SIB will be
f 1
3
changed into 6), however hierarchy of priorities is kept
f 3
5
If configured absolute priority broadcasted in SIB is equal to 0, it is not
f 5
2
f 6
6
lowered by 1 are placed into IMMCI list •
-
(STEP 4) Frequency List
Lowering of SIB priorities while creating IMMCI prevents duplication
lowered. Value of 0 is kept
Main target frequency is added with the highest prio
-1 … …
-1
Dedicated Cell Reselection Priorities (IMMCI list) f 4
7
f 1
2
f 3
4
f 5
1
f 6
5
LTE2051: Measurement based Idle Mode Load Balancing 5) IMMCI Creation -
STEP 7: IMMCI is filled up •
Timer t320 is added to IMMCI
-
t320 defines how long dedicated priorities take precedence over SIB priorities •
timer t320 is configurable (LNCEL:t320)
IE/ Group Name RRCConnectionRelease > rrc-TransactionIdentifier > releaseCause > redirectedCarrierInfo > idleModeMobilityControlI nfo > cellInfoList-r9
Need
ON
Source RRC RRC eNB/RRC eNB/RRC
OP OP
eNB/RRC eNB/RRC
IE/Group Name idleModeMobilityControlInfo > freqPriorityListEUTRA >> carrierFreq >> cellReselectionPriority > freqPriorityListGERAN >> carrierFreq >> cellReselectionPriority > freqPriorityListUTRA-FDD >> carrierFreq >> cellReselectionPriority > freqPriorityListUTRA-TDD >> carrierFreq >> cellReselectionPriority > bandClassPriorityListHRPD >> bandClass >> cellReselectionPriority > bandClassPriorityList1XRTT >> bandClass >> cellReselectionPriority > t320
Presence M OP M M OP M M OP M M OP M M OP M M OP M M OP
LTE2051: Measurement based Idle Mode Load Balancing Configuration management Abbrev
Description
MO
actMeasBasedIMLB
Activate measurement-based Idle mode load balancing
LNBTS
minRsrpIMLB
Target cell minimum RSRP for idle mode load balancing
IRFIM
inDeltaRsrpIMLB
Target cell min delta RSRP for idle mode load balancing
IRFIM
minRsrqIMLB
Target cell minimum RSRQ for idle mode load balancing
IRFIM
minDeltaRsrqIMLB
Target cell min delta RSRQ for idle mode load balancing
IRFIM
enableA4IMLB
Enable A4 event for idle mode load balancing
IRFIM
reportTimerIMLBA4
Idle mode load balancing supervision timer for A4 event
LNBTS
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