802 ue sendback based on load (feature description document)_v1.1

Feature Description Document

for

UE Sendback

Based on Load

Version 1.1

Document No. _______

Advanced Technology Lab Samsung Telecommunications America

Doc Category 802

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802 UE Sendback Based on Load FDD Version 1.1

of 23 2015 © Samsung Telecommunications America, LLC. All Rights Reserved

Proprietary and Confidential. Property of Samsung Telecommunications America.

VERSION HISTORY

Version Date Description Author

1.0 12/6/2013 Initial version Raj Sengupta

1.1 06/12/2015 Clarification on configuration and OMs

Sanil Ramachandran




TABLE OF CONTENTS

1. FEATURE DESCRIPTION .................................................................................................5

1.1 Overview .....................................................................................................................5 1.2 References ...................................................................................................................5

2. PREREQUISITES FOR IMPLEMENTATION ...............................................................6

3. FEATURE FUNCTIONALITY / IMPLEMENTATION .................................................7

4. REQUIREMENTS TRACEABILITY MATRIX (INCLUDING

INTERDEPENDENCIES) .................................................................................................12

5. OPERATIONAL IMPACTS .............................................................................................13

5.1 OMs ..........................................................................................................................13 5.2 Alarms .......................................................................................................................14 5.3 Billing .......................................................................................................................14

5.4 Logs ..........................................................................................................................15 5.5 Configuration Data ...................................................................................................16

5.6 GUI Changes (if applicable) .....................................................................................21

6. RESTRICTIONS AND LIMITATIONS ..........................................................................22

APPENDIX A. ACRONYMS .............................................................................................23




1. FEATURE DESCRIPTION

1.1 Overview The UE sendback based on load feature directs UE devices with a specified PLMN to

neighbor cells that are not overloaded at specified inter-frequencies, irrespective of the

load of the current serving cell. The purpose of this feature is not to control overload, but

to direct traffic such that UE devices will camp on the preferred frequencies.

Use cases:

Sprint has 2.5GHz TDD carriers and 1.9GHz/800MHz FDD carriers. Tri-band UE

devices may be offloaded from 2.5GHz TDD carriers to the 1.9GHz/800MHz FDD

carriers when all cells of a certain area in the 2.5GHz TDD network are fully loaded.

Since the Tri-band UE devices are supposed to camp on to the high priority TDD carriers

if possible, the UE sendback feature in a FDD eNB will direct the UE devices to TDD

carriers in neighbor cells that are not overloaded.

A cell is not overloaded if the cell load values are maintained below a certain threshold,

which can be configured by the operator.

Benefits:

The UE sendback feature provides the following operator benefit.

RRC-connected UEs with a specified carrier may move, if possible, to the preferred

carriers according to the operator policy.

1.2 References

3GPP 36.300: E-UTRA and E-UTRAN; overall description Stage 2

3GPP 36.331: E-UTRAN; Radio Resource Control (RRC); Protocol specification

3GPP 36.423: E-UTRAN; X2 application protocol (X2AP)

3GPP 36.902: E-UTRAN; Self-configuring and self-optimizing network (SON)

use cases and solutions

Feature Detail Description (LTE-SW2001, SW2002) Intra-LTE Load Balancing,

Samsung Electronics




2. PREREQUISITES FOR IMPLEMENTATION

eNB shall be able to exchange cell load information via X2 so that load information of

neighbor eNBs known to each other.




3. FEATURE FUNCTIONALITY / IMPLEMENTATION

The following terminology is used in the UE sendback (SB) feature description:

1. SB-target PLMN: PLMN to which the UE devices should be sent back.

2. SB-candidate UE: UE with the target PLMN.

3. SB-preferred carrier: carrier to which the SB-target UE should move via the UE

sendback feature.

4. SB-neighbor cell: neighbor cell that is in service at an SB-preferred carrier.

5. SB-neighbor eNB: neighbor eNB that has an SB-neighbor cell.

6. SB-source cell: cell that performs the sendback function.

7. SB-source eNB: eNB that has an SB-source cell.

8. SB-threshold-for-capacity: capacity value threshold for determining if a SB-

neighbor cell has an available resource to accommodate more UE devices that are

sent back.

9. SB-candidate-cell-list: list of SB-neighbor cells that are selected as candidate

cells for sendback in the current period.

10. SB-black-cell-list: List of SB-neighbor cells that should be excluded from the

SB-candidate-cell-list.




The UE sendback procedure is illustrated in the following figures.

Figure 1. UE sendback based on load procedure

SB-source eNB SB-neighbor eNB

Updating SB-candidate-cell-list

periodically

X2 Resource Status Request

X2 Resource Status Response

X2 Resource Status Update

(DL/UL capacity values)

Selecting SB-neighbor cells

highly-ranked in NRT

UEs SB-neighbor eNBSB-neighbor eNB

Sending X2 Resource Status

Update message periodically

UEsUEs

RRC Connection Reconfiguration

Event A4 Configuration

RRC Connection Reconfiguration Complete

Measurement Report

UEs are handed over to an SB-neighbor cell within the SB-candidate-cell list.

Updating SB-black-cell-list




Figure 2. UE sendback procedure in a UE sendback period

Measurement configuration on randomly selected SB-candidate UEs

UE

sen

db

ack

per

iod

UE

sen

dbac

k

report

ing t

imer

End of UE sendback action for this period

- Release measurement configuration for remaining SB-candidate UEs

- Update the SB-black-cell-list

Sendback UEs shall send measurement reports for sendback

within this duration. =

mult

iple

s of

Res

ourc

e S

tatu

s

Rep

ort

ing p

erio

dic

ity

The detailed UE sendback procedure is described below.

1. An SB-source cell selects a pre-configured number of high-ranked SB-neighbor

cells for each SB-preferred carrier in its NRT (Neighbor Relation Table).

The rank of each neighbor cell is determined by periodic ranking

developed using UE measurement reports.

The pre-configured number indicates the MaxCandidateCells, which is an

operator-configurable system parameter. For more information, see Table

4. CHG/RTRV-SENDBACK-FUNC.

2. An SB-source eNB sends an X2 Resource Status Request message to an SB-

neighbor eNB to which a selected SB-neighbor cell belongs. The X2 Resource

Status Request message shall include information such as Report Characteristic

IE and Reporting Periodicity IE.

Report Characteristic IE: Composite Available Capacity Group IE shall

be requested since an SB-source eNB can evaluate the load of an SB-

candidate cell based on DL/UL capacity values. In the initial release, only

the DL capacity value is used. In the next release, both DL and UL

capacity values will be used.

Reporting Periodicity IE: The Reporting Periodicity is determined by

tResourceStatusReporting, which is an operator-configurable system

parameter. For more information, see Table 4, .

3. When an SB-neighbor eNB receives an X2 Resource Status Request message, the

SB-neighbor sends an X2 Resource Status Response message if it can report the

requested DL/UL capacity values of the SB-neighbor cell(s).




4. The SB-neighbor eNB sends periodically an X2 Resource Status Update message,

which includes the requested DL/UL capacity values of the SB-neighbor cell(s).

5. The SB-source cell periodically updates its SB-candidate-cell-list based on the

received capacity values of the SB-neighbor cells.

Conditions for entering the SB-candidate-cell-list:

C1: Both the DL and UL capacity values of an SB-neighbor cell should be

maintained over the SB-threshold-for-capacity during a configured

duration. The configured duration is equal to cellSelectionHysteresis

tResourceStatusReporting.

C2: An SB-neighbor cell should not be included in the SB-black-cell-list.

Condition for leaving the SB-candidate-cell-list:

C1: The latest DL (or UL) capacity value of an SB-neighbor cell is less

than the SB-threshold-for-capacity.

6. The SB-source cell selects a configured ratio of SB-candidate UE devices and

provides them the measurement configuration, using the

RRCConnectionReconfiguration message. Then, the SB-source cell starts the

timer for collecting measurement reports.

Measurement configuration for sendback purpose: the A4 event for SB-

preferred carriers is configured for sendback purpose. The A4 event

indicates that a neighboring cell’s RSRP or RSRQ becomes better than a

configured threshold for the signal strength. The system allows

configuration of only one Event A4 threshold per serving cell. This single

threshold is configured towards all target frequencies for sendback

purpose ie. the A4 event threhsolds used for sendback purpose cannot be

configured per target FAs. Refer Table 5. CHG/RTRV-EUTRA-

A4CNF(/Q) (Existing PLD) for more details on A4 event configuration for

sendback purpose.

7. When the corresponding measurement report is received from an SB-candidate

UE, the SB-source cell checks if the SB-neighbor cell satisfying the A4 condition

is a member of the SB-candidate-cell-list. If the SB-neighbor cell is in the SB-

candidate-cell-list, the SB-candidate UE shall be handed over to the SB-neighbor

cell. Here, the HO cause for the sendback is set to Resource Optimization

Handover.

8. The SB-source cell performs step 7 above until the timer expires.

9. The SB-source cell releases the measurements of all the SB-candidate UE devices

that are still in the SB-source cell.

10. The SB-source cell updates its SB-black-cell-list.

Condition for entering the SB-black-cell-list:




C1: At least one UE is sent to the SB-neighbor cell in the current sendback

period. At least one HO preparation for sendback to the SB-neighbor cell

occurs in the current period.

Condition for leaving the SB-candidate-cell-list:

C1: The black-cell-duration-timer expires. The black-cell-duration-timer is

equal to cellReSBTimeCount tResourceStatusReporting.

3.1.1 Measurement for sendback purpose

To avoid affecting the QoE (Quality of Experience) of the UE, an SB-candidate UE

recently handed to a current serving cell shall not be selected to perform the measurement

on the sendback purpose. Only candidate UE devices that have been connected to a

current serving cell over a configured duration (i.e., ueSelectDuration) shall be selected

and configured by the A4 event for sendback purpose. The maximum number of reported

cells shall be fixed to 1 so that only the strongest SB-neighbor cell is reported.

3.1.2 Limitation on the number of candidate UEs to be handed over to a SB-neighbor cell

To avoid causing the cell load of an SB-neighbor to increase significantly in a short

amount of time, the number of candidate UE devices to be sent to an SB-neighbor cell

within one UE sendback period shall be limited according to the following equation.

( ) { ( )

}

In this equation:

floor{p} indicates the maximum integer which is less than or equal to p.

C(i) is the minimum of the latest DL and UL capacity values of the SB-

neighbor cell i.

Y and C_sb should be properly configured by the operator so that at most

Y UE devices (where Y= ueCountForSendback ) can be sent to an SB-

neighbor cell with the capacity value C_sb.




4. REQUIREMENTS TRACEABILITY MATRIX (INCLUDING INTERDEPENDENCIES)

N/A




5. OPERATIONAL IMPACTS

5.1 OMs Below sections describe the OMs and KPIs related to Sendback feature.

5.1.1 Out Handover by Sendback

This section provides statistics on the Out-handover by the unloading function.

5.1.1.1.1 Index

Name Description cNum Cell Id

tcID Target Cell Id

5.1.1.1.2 Statistics Type

Name Unit

Description Visible

Counter Typ

e

Trigge

r Typ

e

Data Type

Min/Max Granularity Formula

Hourly, Daily,

Monthly Formula

SendbackOutAtt

count

Sendback handover out attempt count

Y CC event int 0~2147483647

- -

SendbackOutPrepSucc

count

Sendback handover out preparation success count


- -

SendbackOutSucc

count

Sendback handover out execution success count


- -

SendbackOutCnt

count

Count of Sendback handover collected

- CC event int 0~2147483647

- -

SendbackOutCid

tcID tcID of which collection is requested

- OW event int 0~2147483647

- -

5.1.2 In Handover by Sendback

This section provides statistics on the In-Handover by the unloading function.

5.1.2.1.1 Index






Name Unit

Description Visible

Counter Type

Trigger Typ

e

Data

Type

Min/Max Granularity Formula

Hourly, Daily,

Monthly Formula

SendbackInAtt count

Sendback handover attempt count in Tcell


- -

SendbackInPreSucc

count

Sendback handover preparation success count in Tcell


- -

SendbackInSucc

count

Sendback handover execution success count in Tcell


- -

5.1.3 Load Balancing Handover KPI

This section provides statistics on the Load Balancing handover KPI from the collected Load Balancing handover.

5.1.3.1.1 Index



Name Unit

Description Visible

Counter Typ

e

Trigger Typ

e

Data Type

Min/Max

Granularity

Formula

Hourly, Daily,

Monthly Formula

SendbackHOSuccRatio

% Handover success ratio by sendback in SeNB

Y OW Period

float 0~100 SumSendbackHOSucc/SumSendbackHOAtt*100

sum(SumSendbackHOSucc)/sum(SumSendbackHOAtt)*100

SumSendbackHOAtt

count

Sum of handover preparation attempt count by sendback in SeNB

- CC event int 0~2147483647

- -

SumSendbackHOSucc

count

Sum of handover execution success count by sendback in SeNB

- CC event int 0~2147483647

- -

5.2 Alarms

N/A

5.3 Billing N/A




5.4 Logs N/A




5.5 Configuration Data Table 1. Sendback configuration commands

Command Description

RTRV-TM-CNTR RETRIEVE FLAGS IN TRAFFIC_MANAGEMENT_FUNC

CHG-TM-CNTR CHANGE FLAGS IN TRAFFIC_MANAGEMENT_FUNC

RTRV-SENDBACK-

CONF RTRIEVE PARAMETERS IN PLD_SENDBACK_CONFIGRATION

CHG-SENDBACK-

CONF CHANGE PARAMETERS IN PLD_SENDBACK_CONFIGRATION

RTRV-SENDBACK-

FUNC RETRIEVE PARAMETERS IN PLD_SENDBACK_LB_FUNC

CHG-SENDBACK-

FUNC CHANGE PARAMETERS IN PLD_SENDBACK_LB_FUNC

RTRV-EUTRA-

A4CNF RETRIEVE EUTRA A4CRITERIA INFORMATION

CHG-EUTRA-

A4CNF CHANGE EUTRA A4CRITERIA INFORMATION




5.5.1 Parameters

Table 2. CHG/RTRV-TM-CNTR

Parameter Range Default Value Description

cellNum 0~MAX_CELL _PER_SYS_CDD

0 Cell Index

sendbackEnable

enumDiagCallEnble_type = ci_ON, ci_OFF

Ci_OFF Whether to enable the sendback

feature

Table 3. CHG/RTRV-SENDBACK-CONF



0 Cell Index

plmnIdx 0~5 0

PLMN Index,

This PLMN index indicates the SB-

target PLMN that is configured as

the corresponding index in the

PLD_EnbPlmnInfo.

sendbackFlag enumActiveState = Inactive, Active

Inactive

sendbackFlag indicates whether to

use sendback to this PLMN.

-InActive: Set off sendback.

-Active: Set on sendback.

earfcn0 -1 ~ 65535 -1

earfcn0, earfcn1, earfcn2, and

earfcn3 are used to set EARFCN of

SB-preferred carrier for this SB-

target PLMN.

- The actual range for EARFCN is

from 0 to 65535.

- When it is set to -1, this slot is not

used.

earfcn1 -1 ~ 65535 -1 Same to the description for earfcn0






Table 4. CHG/RTRV-SENDBACK-FUNC


maxCandidateCells 0 ~ 32 19

Maximum number of SB-neighbor

cells in each EARFCN to report

Resource Status for sendback

purpose via X2

- Unit: none

tResourceStatusReporting

enumLbmcPeri

od1_type

= 1sec, 2sec,

5sec, 10sec

ci_lbPeriod1_100

00ms

Resource Status Reporting period

for sendback purpose

- Unit: seconds

maxCandidateUe 0 ~ 30 (%) 10

Maximum ratio of SB-candidate UE

to max call count in a cell, which are

selected to perform measurement

for sendback purpose

- Unit: percentage (%)

cellSendbackThreshold 0 ~ 100 (%) 40

Capacity value threshold for

determining if a SB-neighbor cell

has an available resource to

accommodate more UEs sent back

- Unit: percentage (%)

ueSelectDuration 1 ~ 30 (sec) 1

Only candidate UE which have

been connected to a current serving

cell over ueSelectDuration shall be

selected to perform measurement

for the sendback purpose.

- Unit: seconds

ueReportingTimer 1 ~ 10 (sec) 1

Timer for collecting measurement

reports on the sendback purpose.

If this timer expires, the SB-source

cell shall release the measurements

of all the SB-candidate UE which

are still in the SB-source cell.

- Unit: seconds

ueSendbackPrd 10 ~ 600 (sec) 10 Period for sendback process

- Unit: second

cellSelectionHysteresis 1 ~ 10 (times) 1

If both DL and UL capacity values of

an SB-neighbor cell exceed

cellSendbackThreshold more than

consecutive

cellSelectionHyteresis times

during recent Resource Status

Reporting, the cell is registered in

the SB-candidate-cell-list.





ueCountForSendback 1 ~ 10 1

This parameter is used to control

the max number of SB-candidate

UE which are handed over to an

SB-neighbor cell.

- Here, we assume that at most Y

UE devices (where

Y=ueCountForSendback) can be

sent to an SB-neighbor cell with

capacity value C_sb (=

‘cellSendbackThreshold’). If its cell

capacity value is larger than C_sb,

then we think that more UE are

allowed to be sent to an SB-

neighbor cell.

cellReSBTimeCount 1 ~ 100 (times) 1

When some UE are sent to an SB-

neighbor cell due to the sendback

process, then the SB-neighbor cell

is included in the black list during a

cell reconsideration time

(cell reconsideration time =

cellReSBTimeCount

tResourceStatusReporting).




Table 5. CHG/RTRV-EUTRA-A4CNF(/Q) (Existing PLD)



0 Cell Index

purpose enumA4Purpose_type

ci_A4PurposeIntraLteHandover. This value should be set to Ci_A4PurposeSendback.

Parameters should be set for the

sendback A4 measurement

configuration in the purpose index

Ci_A4PurposeSendback.

faIndex 0~7 0

FaIndex value 0 should be

equipped with A4 thresholds for

Sendback purpose. This single A4

event threshold, configured using

FaIndex#0 is used across all target

FAs. Even if different A4 thresholds

are configured for FA index other

than 0, they are ignored. Sendback

for target frequencies are enabled

using CHG -SENDBACK-CONF

command.

activeState enumActiveState = Inactive, Active

Inactive If this is set to Inactive, the event

A4 is not configured.

a4ThresholdRSRP 0 ~ 97 35 RSRP threshold used for the event

A4 condition

a4ThresholdRSRQ 0 ~ 34 32 RSRQ threshold used for the event

A4 condition

hysteresis 0 ~ 30 0

hysteresis value for the event A4,

This is used to determine the

entering condition [(Measurement

Result - Hysteresis) Threshold] and

leaving condition [(Measurement

Result + Hysteresis) Threshold].

timeToTrigger enumTimeToTrigger_type

9

The event A4 occurs only when a

specific threshold meet a threshold

during the period of

TIME_TO_TRIGGER and the

TIME_TO_TRIGGER can be set to

a value 0 - 5120 ms as defined in

the TS.36.331.

triggerQuantity triggerQuantity_type

0

The TRIGGER_QUANTITY for the

event A4 can be set to RSRP or

RSRQ.

reportQuantity eutraReportQuantity_type

1

The REPORT_QUANTITY can be

set to sameAsTriggerQuantity or

both.

maxReportCell 1 ~ 8 8 or 1, depending on configuration.

This parameter indicates the

maximum number of neighbor cells

that can be included in the





measurement report for the event

A4. For sendback, this should be

set to 1.

reportInterval enumReportInterval_type

1

This applies only when the

REPORT_AMOUNT is larger than

1. The REPORT_INTERVAL can

be set to 120 ms - 30 min.

according to TS36.331.

reportAmount enumReportAmount_type

3

The REPORT_AMOUNT is the

number of measurement reports

when the A4 event condition is met.

5.6 GUI Changes (if applicable) N/A




6. RESTRICTIONS AND LIMITATIONS

N/A




APPENDIX A. ACRONYMS

Acronym Definition

DL Downlink

EARFCN E-UTRA Absolute Radio Frequency Channel Number

eNB Evolved Node B

E-UTRA Evolved Universal Terrestrial Radio Access

E-UTRAN Evolved Universal Terrestrial Radio Access Network

FDD Frequency Division Duplex

HO Handover

IE Information Element

MOCN Multi Operator Core Network

PCID Physical Cell Identifier

PLMN Public Land Mobile Network

QoE Quality of Experience

RRC Radio Resource Control

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality

SB Sendback

TDD Time Division Dulplex

UE User Equipment

UL Uplink

802 ue sendback based on load (feature description document)_v1.1

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