Idle Mode Mobility

(1)

LTE Radio Parameters 2 [FL15a]

Idle Mode Mobility

Nokia

(2)

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(3)

Module Objective

After completing this learning element, the participant should be able to describe

discuss and analyze:

(4)

Index

•Idle Mode Mobility Load Balancing

•Load triggered Idle Mode Mobility Load Balancing

•Measurement based Idle Mode Load Balancing

(5)

Index

•Idle Mode Mobility Load Balancing

•Load triggered Idle Mode Mobility Load Balancing

•Measurement based Idle Mode Load Balancing

(6)

Intra-Frequency

Inter-Frequency

Intra-LTE

Inter-RAT

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) Idle Mode Load Balancing Features

Idle Mode Mobility Load Balancing

Load Balancing Features Overview

(7)

LTE 487 Idle Mode Mobility Load Balancing

RL50

LTE1677 Idle Mode Mobility Load Balancing Extensions

RL60

Broadcasted Cell Reselection Priorities Freq 1 High

Freq 2 Low

Dedicated Cell Reselection Priorities Freq 1 Low Freq 2 High Broadcasted Cell Reselection Priorities Freq 1 High Freq 2 Low 1. UEs connected to Freq1

Freq1

Freq2

2. UEs are released by the cell

3. Selected UEs are sent IMMLB priorities

4. UEs uses the IMMLB priorities for reselection

Broadcasted Cell Reselection

Priorities

Freq 1

High

Freq 2

Low

Dedicated Cell Reselection

Priorities

Freq 1

Low

Freq 2

High

Percentage of UEs

33%

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

(8)



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



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

Candidate UE selection

LTE 487/LTE1677 Idle Mode Mobility Load

Balancing/Extensions

# of RRC connection release messages with idleModeMobilityControlInfo # of RRC connection release messages

idleLBPercentageOfUe

Check assumes that UE to be released is sent idleModeMobility ControlInfo

(9)

Idle mode mobility balancing extensions

- 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 1will be chosen as a main target for IMMLB; Dedicated Cell Reselection Priority for f 17

- (0.5;0.75] then frequency f ₃will be chosen as a main target for IMMLB; Dedicated Cell Reselection Priority for f ₃7 - (0.75;1] then frequency f ₄will 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

LTE1677

_–

Idle Mode Mobility Load Balancing Extensions (RL60)

0

0.5

0.5 0.75 0.75

1

p1WRR(f 1 ) =0.5 p2 WRR(f 3 ) =0.25 p₃WRR(f ₄ ) =0.25

f

₁

= [ 0;0.5 ]

f

₃

= ( 0.5;0.75 ]

f

4

= ( 0.75;1 ]

Generated value 0.76 means that f 4 will get priority 7 in IMMCI

(10)

• actIdleLB

Activation of idle mode load balancing (IdleLB)

• idleLBPercentageOfUes

MODPR, MOPR, LNCEL Percentage of UE for idle mode load

balancing

• moimpId

Idle mode mobility profile identifier

• modimpId

Idle mode mobility default profile identifier

• T320

LNCEL Timer T320

• For MODIMP, MOIMP, LNCEL

• 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

Parameters

LTE 487/LTE1677 Idle Mode Mobility Load

Balancing/Extensions

(11)

Index

•Idle Mode Mobility Load Balancing

•Load triggered Idle Mode Mobility Load Balancing

•Measurement based Idle Mode Load Balancing

(12)

LTE2050 Load Triggered Idle Mode Load Balancing

• Introduction of

inter-RAT capability

RL40

RL50

_–

LTE487

• Load balancing across

LTE carriers

• 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

• RL70 introduces the capability to trigger IMMLB only when the load becomes high

• rather than always triggering the feature

• Introduction of Absolute

Priority Weights

(13)

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 %,

(14)

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

(15)

LTE2050 Load Triggered Idle Mode Load Balancing

Triggering

• load balancing is triggered when

CAC <

idleLBCapThresh

CAC

50%

Target load

60%

Cell load max

100%

Rel load 100%

idleLBCapThresh 90%

CAC 50% < idleLBCapThresh 90% therefore IMLB = True

LNCEL; idleLBCapThresh

Idle mode load balancing capacity threshold

0..100% Default: 100%

(16)

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

LNCEL - loadSettings

cellCapClass

mlbEicicOperMode

nomNumPrbNonGbr

targetLoadGbrDl

targetLoadNonGbrDl

targetLoadPdcch

ulCacSelection

ulStaticCac

New object for common load balancing parameters

(17)

Index

•Idle Mode Mobility Load Balancing

•Load triggered Idle Mode Mobility Load Balancing

•Measurement based Idle Mode Load Balancing

(18)

LTE2051: Measurement based Idle Mode Load Balancing

• LTE2051 is an extension of IMMLB algorithm

• 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

(19)

• 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

• 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]

LTE2051: Measurement based Idle Mode Load Balancing

Check if IMMLB should be triggered IMMLB Objects Selection Candidate UE Selection IMMCI creation Load supervision and

CAC calculation L T E 2 0 5 0

Load Triggered Idle Mode Load Balancing

Connected 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

(20)

Is there any frequency

on list?

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 1

List of frequency layers, based on selected IMMLB object is created. This is done for the Main target frequency selection

Weighted Round Robin Algorithm is used to

determine the main target for IMMLB Yes

No

STEP 2

STOP = NO IMMCI is sent to UE

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

STEP 4

STEP 6

STOP

STEP 3

IMMCI list is filled up: 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

Main target validation RSRP/RSRQ of cells of main target are checked

All criteria fulfilled?

STOP = NO IMMCI is sent to UE STEP 5 Yes No STEP 7

LTE2051

(21)

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)

Only primary target that is an inter-frequency

LTE layer may be validated with LTE2051

(22)

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

- A4 supervision timer (LNBTS:reportTimerIMLBA4) is controlling both prolonged RRC Connected state as well as A4 measurement period

- 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 R R C s t a t e RRC Connected RRC Idle time 1 2 3 Note:

InactivityTimer is running (LNCEL:InactivityTimer) RRC Connected phase is prolonged as A4 supervision timer is running

RRC Connection Release with or without IMMCI, depending on Idle LB algorithm decision

1 2

(23)

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 (RSRP_T) is checked against serving cell RSRP (RSRP_S), 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 (RSRQ_T) is checked against serving cell RSRQ (RSRQ_S), 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

(24)

- 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

STEP 6

LTE2051: Measurement based Idle Mode Load Balancing

5) IMMCI Creation

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 Frequency List

FREQ SIB PRIO

f 1 3 f ₃ 5 f 5 2 f ₆ 6 MOPR MOIMP-1 MOIMP-X LNCEL GFIM CDFIM UFFIM IRFIM

OR

(25)

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 lowered by 1 are placed into IMMCI list

• Lowering of SIB priorities while creating IMMCI prevents duplication of main target that could appear (priority value 7 in SIB will be changed into 6), however hierarchy of priorities is kept

- If configured absolute priority broadcasted in SIB is equal to 0, it is not lowered. Value of 0 is kept

(STEP 4) Frequency List

FREQ SIB PRIO

f ₁ 3 f 3 5 f 5 2 f 6 6 Dedicated Cell Reselection Priorities (IMMCI list) f 4 7 f ₁ 2 f 3 4 f ₅ 1 f 6 5

-1

…

-1

Main target frequency is added with the highest prio

(26)

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

Presence

idleModeMobilityControlInfo

M

> freqPriorityListEUTRA

OP

>> carrierFreq

M

>> cellReselectionPriority

M

> freqPriorityListGERAN

OP

>> carrierFreq

M

>> cellReselectionPriority

M

> freqPriorityListUTRA-FDD

OP

>> carrierFreq

M

>> cellReselectionPriority

M

> freqPriorityListUTRA-TDD

OP

>> carrierFreq

M

>> cellReselectionPriority

M

> bandClassPriorityListHRPD

OP

>> bandClass

M

>> cellReselectionPriority

M

> bandClassPriorityList1XRTT

OP

>> bandClass

M

>> cellReselectionPriority

M

> t320

OP

IE/ Group Name

Need

Source

RRCConnectionRelease

RRC

> rrc-TransactionIdentifier

RRC

> releaseCause

eNB/RRC

> redirectedCarrierInfo

ON

eNB/RRC

>

idleModeMobilityControlI

nfo

OP

eNB/RRC

> cellInfoList-r9

OP

eNB/RRC

(27)

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

(28)