Feature Description for LTE Mobility Load Balancing-V1.4

Feature Description for LTE Mobility Load Balancing

Organization

Nokia SON

Version

14

Date

Dec 14, 2015

Dec 14, 2015 – Feature Description for LTE Mobility Load Balancing 1 / 24

© Nokia Solutions and Networks 2015

Contents 1

Introduction Introductio n.............................................................................................................. 3

1.1

Eden-NET Release Information ............................................................................... 3

1.2

Audience Audienc e ................................................................................................................. 3

2

Background Backgroun d ............................................................................................................. 5

3

Dependencies Depende ncies and Interaction Interactions s ............................................................................... 6

3.1

Dependencies Depende ncies ......................................................................................................... 6

3.2

Interactions Interaction s .............................................................................................................. 6

4

Module Functiona Functionall Description................................................................................. 7

4.1

Module Reporting .................................................................................................... 7

4.2

CM and PM Inputs for LTE Load Balancing ............................................................. 8

4.3

Supported Vendo Vendors rs and Technolo Technologies gies ..................................................................... 8

4.4

Running the LTE Load Balancin Balancing g Module................................................................ 8 Module Configuration Parame Parameters ters (user accessible, graphical interface) ................. 9 Module Configuration Parame Parameters ters (Configu (Configuration ration File, Export settings) ................... 11

4.5

LTE Load Balancin Balancing g Flow Chart .............................................................................. 14

5

System Delay .......................................................................................................... 16

6

Module Outputs ....................................................................................................... 21

6.1

Action Performed..................................................................................................... 21

6.2

Offset Data .............................................................................................................. 21

6.3

KPI Data .................................................................................................................. 23



1

Introduction

This document contains the functional description and high level requirements for the Eden-NET LTE Mobility Load Balancing (MLB) module. It should be noted that additional implementation level requirements may be identified by developers implementing the module. 1.1

Eden-NET Release Information

The version of module described in this document is planned as part of the Eden-NET 15 SP2 release. 1.2

Audience

This document is intended for the use of the following audience(s): 1. Operators using the Eden-NET LTE Load Balancing module





This document provides a reference describing the module that may be reviewed by operators and other customers that plan to use this tool. Please note that the information contained in this document is confidential and proprietary to Eden Rock Communications and is generally only shared outside of Eden Rock under the terms of a Non Disclosure Agreement (NDA), Proprietary Information Agreement (PIA) or similar agreement.

1. Developers implementing the Eden-NET LTE Load Balancing module



This document provides the requirements that feed into the development of the module

1. Testers developing test cases and testing the Eden-NET LTE Load Balancing module





The requirements in this document directly feed into the test cases that are developed for testing the functionality of the module.



2

Background

The Eden-NET LTE Load Balancing module detects cells that are exhibiting signs of high utilization when compared to neighbor cells. The module redistributes traffic through the use of idle mode reselection parameters and dedicated mode offset parameters to up to five immediate intrafrequency neighbor cells. The module monitors the impacted cells to ensure that the parameter changes do not negatively impact those cells. When the high utilization has abated, the module reverts the parameter settings to their default, long-term, settings. Reports detailing network changes taken by the module can be automatically sent to the relevant RF engineers.



3

Dependencies and Interactions

3.1

Dependencies

The LTE MLB module is adjusting CIO and reselection offsets according to the mobility flows, utilization, buffer delay, and performance. The module target cell selection inputs are based on handovers, so it is necessary to have clean neighbor lists or the module may select non-optimal target cells for traffic mitigation. 3.2

Interactions

The LTE MLB module needs to have clean coverage delimitation so it is recommended to run the LTE CCO before working on CIO offsets or optimizing the mobility performance (LTE MRO).



4

Module Functional Description

The LTE load balancing module detects cells within the LTE network that exceed the loading threshold triggers for admission control access failures, physical resource block utilization, and buffer delay. When congested cells are detected, the module attempts to reduce congestion by moving idle mode users on the congested cell edges and dedicated users on the congested cell to neighbor cells. The LTE loadbalancing will only operate on cell where enough average active users are present. The LTE load balancing module does this through: -

Making adjustments to neighbor cell offset parameters used in both dedicated and idle mode.

-

Making adjustments to handover thresholds.

The module examines the loading on neighbor cells and attempts to distribute load among the top 5 target neighbor cells in order to reduce source cell congestion. Every 15 minute PM reporting period, the module retrieves the load on the source and neighbor cells and adjusts individual offsets per neighbor pair to allow priority selection in UE offload to these neighbor cells. The cell with the lowest load can be assigned the highest priority and the cell with the highest load is assigned the lowest priority. The module monitors the handover success rate for each handover pair to ensure that the most suitable neighbors are selected as target cells for sharing the excess load on the source cell. The module ensures that corrective actions do not cause the neighbors cells themselves to become congested. The module continually monitors the load of the neighbor cells to ensure that the UE offloading (particularly for dedicated mode UEs) does not cause the target neighbor cells to become congested. If this occurs, other neighbor cells will be made more attractive (through offset adjustments), so offloading decreases to the loaded target cell. Once loading consistently decreases the module returns all parameters to operator defined settings. Section 3.6 provides the LTE Load balancing flow chart for the above description. 4.1

Module Reporting

In open and closed loop modes the module provides the following reports at each iteration of the module:



All cells that exceed the load thresholds, together with the cause of the cell load trigger accessibility or cell loading or both. The congested cells top 5 neighbor target cells with their offset priorities as well as their respective cell loading metrics. PM metrics that provide accessibility, retainability and cell loading measurements per cell which is being acted on by the load balancing algorithm. The report is in the form of an Excel spreadsheet. In addition to the module reports, the Eden-NET framework logs module activity. These logs may be retrieved and reviewed by the module user. 4.2

CM and PM Inputs for LTE Load Balancing

The LTE Load Balancing module requires the intra frequency neighbor list configuration for each of the target cells in the network. This data is read via the OSS interfaces. The configuration information (e.g., lat/long, neighbor lists, etc.) used by the module shall be read from the Eden-NET CM cache in order to minimize accesses to OSS. The Eden-NET framework automatically determines if the parameter data should be read from the radio access network, based on timeout parameters for the cache. The LTE Load Balancing module requires cell load and accessibility PM data. In particular, the module retrieves blocking metrics including call establishment success rates, and cell loading metrics including PRB utilization, scheduler buffer delay, and average connected UEs. 4.3

Supported Vendors and Technologies

This module shall provide load optimization for all LTE RAN Vendors that are supported by EdenNET. This includes but is not to be limited to Ericsson 4G and NSN 4G. 4.4

Running the LTE Load Balancing Module

The module shall be launched by users using the standard Eden-NET interface. Target cells shall be selected by the user. Eden-NET restricts module to making changes to only those target cells selected by the user. Note that a module may retrieve configuration and performance information for other cells in the network that are not on the target list. For many modules, this information may be required by the modules core algorithms.



The module run mode may be one time or continuous. For continuous operation, the module shall re-evaluate the load triggers every performance measurement period - e.g. 15min. The reports are stored within the Eden-NET framework. When the module is run in open loop, the reports are created after the overloaded cells have been determined. When the module is run in closed loop, the reports are created after the module has validated whether or not the changes pushed to the network were successful. The module shall support open loop and closed loop modes of operation. Multiple instances of the module, each with its own target cell list are permitted. Module Configuration Parameters (user accessible, graphical interface) Parameter Name

Parameter Description

Default Range Value (min, max)

Step

PRB threshold

This parameter allows the user to define a trigger threshold for setting of PRB occupancy over a measurement period.

80

0..100

1

Buffer Delay QC1

This parameter defines the 30 maximum amount of time data scheduled for a user is allowed to be delayed within the eNB. As the eNB loads per cell the delays for transmission of data will increase and eventual exceed this threshold indicating overload.

10..100

10

Buffer Delay Non GBR

This parameter defines the 300 maximum amount of time data scheduled for a user is allowed to be delayed within the eNB. As the eNB loads per cell the delays for transmission of data will increase and eventual exceed this threshold indicating overload.

100..1000 50



Parameter Name


Userdefined_L_RAC (LACHysteresis / RACHysteresis)

This parameter allows the user to 5 define a threshold for the percentage of blocking due to Load and Admission Control before load balancing is activated.This parameter sets the threshold for the increase in eNB resource failure on the target cell before the algorithm attempts to reduce the offsets applied.

0..100

1

Userdefined_Erab

This parameter allows the user to set 5 a threshold for ERAB failures due eNB resource blocking before load balancing is activated

0..100

1

Userdefined_Time_No_Res

This parameter allows the users to set a percentage of time threshold for blocking due to lack of eNodeB resources over the measurement period, before load balancing is activated.

0..100

1

HOHysteresis

This parameter sets the threshold for 10 the increase in HO failure rate between the target and source cell before the algorithm attempts to reduce the offsets applied.

0..100

1

ERABHysteresis

This parameter sets the threshold for 10 the increase in drop rate for the target cell before the algorithm attempts to reduce the offsets applied.

0..100

1



5

Step


Parameter Name



Step

SNRThreshold

This parameter allows the user to set 10 a threshold to allow high levels of interference for a percentage of all SINR measurements before reducing the cell weighting for all neighbor cells.

0..100

1

RedOffset

Value that sets the amount by which 1 the CIO offsets can be decreased.

0..2

1

IncOffset

Value that sets the amount by which 1 the CIO offsets can be increased.

0..2

1

Maintenance_Window_Start_Time

Start time 0 - 23 hours

22

0..23

1

Maintenance_Window_End_Time

End time 0 - 23 hours

8

0..23

1

Allowed non-congestion times for reducing offsets

Consecutive times of non-congestion 3 till which offsets can be reduced

0..10

1

SON Operation Mode

Set to "Open Loop" to run module in Open open loop mode. Set to "Closed Loop Loop" to run module in closed loop mode. In Open Loop mode, module cannot push parameter changes to network elements.

Open Loop, Close Loop

Module Configuration Parameters (Configuration File, Export settings) For reference purpose, the parameters available through the configuration file are listed in appendix B. These parameters are set by Nokia's engineers. [Global]

Comments

Low_Users = 5

The minimum required average active users for the module to trigger a cell for mitigation



Buffer_Slope = 2

Model factor for penalizing utilization calculation for cells with high latency

Buffer_Weight = 30

Model factor for penalizing utilization calculation for cells with high latency

Loading_Threshold = 20

Overhead capacity required over the source cells for qualifying target cells for mitigation

Reduce_Congested_Target_Offset = 2

Offset reduction when a target cell goes triggers high utilization

Hourly_kpi_interval_hrs = 24

Aggregation window for handover traffic kpis

Quarterly_kpi_periods = 3

Number of kpi periods to scan back for valid and complete data before starting algorithm run

[Cell Data] White_listed_cells = ,

For testing purposes only. For the cluster selected, only the white listed cells are allowed to enter mitigation

[Target Neighbor Offloading - Dedicated Mode (S->T, T->S)]

Specify the changes of offset for the 5 targets, the first value being the offset from source to cell and the second value being the offset for the reverse flow target to source.

Target1 = 2, -2

Lowest load

Target2 = 2, -2 Target3 = 3, -3 Target4 = 3, -3 Target5 = 4, -4

Highest load

Threshold_Increment = 6

sMeasure offset



[Target Neighbor Offloading - Idle Mode (S->T, T->S)]

Specify the changes of offset for the 5 targets, the first value being the offset from source to cell and the second value being the offset for the reverse flow target to source.

Target1 = 2, -2

Lowest load

Target2 = 2, -2 Target3 = 3, -3 Target4 = 3, -3 Target5 = 4, -4

Highest load

Threshold_Increment = 10

sIntraSearch offset



4.5

LTE Load Balancing Flow Chart





5

System Delay

In consideration of PM File Delay and System Feedback Cycle Length, the module should not make a response action if the current available PM Period is not older than the last OSS Push Time. This means the system will take steps at least every 3 PM file periods for 15 mins data. See diagram below:











6

Module Outputs

6.1

Action Performed

Timestam Source p

Action_performe Reason-congestion d

8/17/2015 LBQ04820B3 Overloaded 10:15 1 Cell/Pushing offset

ReasonReason performance -Uplink-degradation Noisy

Congestion Detected: %_DL_PRB_Util=85.497199059 9. Greater than 80

8/17/2015 LBQ04820B3 No degradation Congestion Detected: 12:15 1 or noisy %_DL_PRB_Util=96.706579775. uplink/Increasing Greater than 80 offset 8/17/2015 LBQ04820B3 No degradation Congestion Detected: 14:15 1 or noisy %_DL_PRB_Util=84.258996442 uplink/Increasing 4. Greater than 80 offset 8/17/2015 LBQ04820B3 No degradation Congestion Detected: 20:15 1 or noisy %_DL_PRB_Util=84.698447184 uplink/Increasing 6. Greater than 80 offset 6.2 Time

Offset Data Relatio Source n Type

Cell 1

Cell 2

Offset name

Offse Action t Performe value d

8/17/201 Source LBQ04820B LBQ04820B LBK04040C cellIndividualOffsetEUtr 1 5 10:18 - NR_1 31 31 11 an


new offset applied (S->T)


8/17/201 NR_1 - LBQ04820B LBK04040C LBQ04820B cellIndividualOffsetEUtr -1 5 10:19 Source 31 11 31 an

new offset applied (T->S)

8/17/201 Source LBQ04820B LBQ04820B LBK04040C qOffsetCellEUtran 5 10:19 - NR_1 31 31 11

1


8/17/201 NR_1 - LBQ04820B LBK04040C LBQ04820B qOffsetCellEUtran 5 10:19 Source 31 11 31

-1


8/17/201 Source LBQ04820B LBQ04820B LBQ04820B cellIndividualOffsetEUtr 1 5 10:19 - NR_2 31 31 11 an


8/17/201 NR_2 - LBQ04820B LBQ04820B LBQ04820B cellIndividualOffsetEUtr -1 5 10:19 Source 31 11 31 an


8/17/201 Source LBQ04820B LBQ04820B LBQ04820B qOffsetCellEUtran 5 10:19 - NR_2 31 31 11

1


8/17/201 NR_2 - LBQ04820B LBQ04820B LBQ04820B qOffsetCellEUtran 5 10:19 Source 31 11 31

-1


8/17/201 Source LBQ04820B LBQ04820B LBQ04820B cellIndividualOffsetEUtr 1 5 10:19 - NR_3 31 31 21 an




8/17/201 NR_3 - LBQ04820B LBQ04820B LBQ04820B cellIndividualOffsetEUtr -2 5 10:19 Source 31 21 31 an


8/17/201 Source LBQ04820B LBQ04820B LBK04040C cellIndividualOffsetEUtr 2 5 12:15 - NR_1 31 31 11 an

Increase d Offset (S->T)

8/17/201 NR_1 - LBQ04820B LBK04040C LBQ04820B cellIndividualOffsetEUtr -2 5 12:15 Source 31 11 31 an

Decrease d Offset (T->S)

8/17/201 Source LBQ04820B LBQ04820B LBK04040C qOffsetCellEUtran 5 12:15 - NR_1 31 31 11

2

Increase d Offset (S->T)

8/17/201 NR_1 - LBQ04820B LBK04040C LBQ04820B qOffsetCellEUtran 5 12:15 Source 31 11 31

-2

Decrease d Offset (T->S)

6.3

KPI Data

Timesta Cell Cell mp Type

%_DL_PR Avg_Lat_ Avg_Lat_All Avg_Act_ DL_Traffic %_B_PUSCH B_Util QC1 _QCI User _Vol _SNR

12/31/2 Sour LCH3202 89.2 014 ce 9A11 14:50

18

463

28.66

10385257 18.46838818 696

12/31/2 nr-1 LCH2282 76.8 014 6B21 14:50

15

191

10.5

41752943 16.17648273 68

12/31/2 nr-2 LCH3202 63.9 014 9A21 14:50

18

173

9.16

53223200 9.00862671 88



12/31/2 nr-3 LCH2070 64.5 014 0B31 14:50

23

167

5.08

42453023 13.99109283 36

12/31/2 nr-4 LCH1209 80.0 014 9A21 14:50

19

144

16.26

98864343 20.00402641 60

12/31/2 nr-5 LCH1209 42.9 014 8A31 14:50

17

64

9.27

41799716 8.20935475 24



Feature Description for LTE Mobility Load Balancing-V1.4

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