ZGO-02!02!002 Dynamic Handover Priority Algorithm Feature Guide ZXG10 IBSC (V12.3.0)20131108

ZGO-02-02-002 Dynamic

Handover Priority Algorithm

Feature Guide

ZGO-02-02-002 Dynamic Handover Priority Algorithm

ZTE Confidential Proprietary 1


Version Date Author Reviewer Notes

V1.0 2013/11/4

Hua Zhibin,

Zhang

Henglong

Gu Yuhui New

© 2014 ZTE Corporation. All rights reserved.

ZTE CONFIDENTIAL: This document contains proprietary information of ZTE and is not to be disclosed or used

without the prior written permission of ZTE.

Due to update and improvement of ZTE products and technologies, information in this document is subjected to

change without notice.


2 ZTE Confidential Proprietary

TABLE OF CONTENTS

1 Feature Attribute ............................................................................................... 5

2 Overview ............................................................................................................ 5

2.1 Feature Introduction ............................................................................................. 5

2.2 License Control .................................................................................................... 6

2.3 Correlation with Other Features ........................................................................... 6

3 Technical Description ....................................................................................... 6

3.1 Handover type classify ......................................................................................... 7

3.2 Traffic value for the target adjacent cells .............................................................. 8

3.3 Filter the high load target adjacent cells ............................................................... 9

3.4 Calculate the dynamic priority .............................................................................. 9

3.5 Adjacent cells queuing ....................................................................................... 10

4 Parameters and Configurations ..................................................................... 11

4.1 Parameter List ................................................................................................... 11

4.2 Parameter Configuration .................................................................................... 11

4.2.1 Allow dynamic adjustment of handover priority .................................................. 11

4.2.2 Minimal resource threshold ................................................................................ 12

4.2.3 Priority of handover ............................................................................................ 12

4.2.4 Difference of dynamic priority ............................................................................. 13

4.2.5 Target cell traffic threshold ................................................................................. 13

4.2.6 Dynamic Priority NCell Traffic Threshold ............................................................ 14

4.2.7 Non Emergency Handover use Dynamic Priority ............................................... 14

4.2.8 Emergency Handover use Dynamic Priority ....................................................... 14

4.2.9 Filter Exceed Traffic threshold NCell .................................................................. 15

5 Related Counters and Alarms ........................................................................ 15

5.1 Related Counters ............................................................................................... 15

5.2 Related Alarms .................................................................................................. 15

6 Engineering Guide .......................................................................................... 16

6.1 Application Scenario .......................................................................................... 16

6.2 Configuration Description ................................................................................... 16

6.3 Feature Validation .............................................................................................. 24

6.3.1 Non Emergency handover Dynamic priority ....................................................... 24

6.3.2 Emergency handover Dynamic priority ............................................................... 25

6.3.3 Non Emergency handover filter high load NCell ................................................. 25

6.4 Feature Turn off ................................................................................................. 26

6.5 Network Impact .................................................................................................. 27



7 Abbreviation .................................................................................................... 27

8 Reference Document ....................................................................................... 28



FIGURES

Figure 6-1 Allow dynamic adjustment of handover priority .................................................17

Figure 6-2 Minimal resource threshold ...............................................................................18

Figure 6-3 Priority of handover ...........................................................................................19

Figure 6-4 Difference of dynamic priority ............................................................................20

Figure 6-5 Target cell traffic threshold ................................................................................21

Figure 6-6 Dynamic Priority NCell Traffic Threshold...........................................................22

Figure 6-7 Non Emergency Handover use Dynamic Priority ..............................................22

Figure 6-8 Emergency Handover use Dynamic Priority ......................................................23

Figure 6-9 Filter Exceed Traffic threshold NCell .................................................................23

Figure 6-10 Close the function of Allow dynamic adjustment of handover priority ..............27

TABLES

Table 4-1 Parameter List ...................................................................................................11

Table 4-2 Configuration rule of allow dynamic adjustment of handover priority ..................11

Table 4-3 Configuration rule of Minimal resource threshold ...............................................12

Table 4-4 Configuration rule of Priority of handover ...........................................................12

Table 4-5 Configuration rule of Difference of dynamic priority ............................................13

Table 4-6 Configuration rule of Target cell traffic threshold ................................................13

Table 4-7 Configuration rule of Dynamic Priority NCell Traffic Threshold ...........................14

Table 4-8 Non Emergency Handover use Dynamic Priority ................................................14

Table 4-9 Configuration rule of Emergency Handover use Dynamic Priority ......................14

Table 4-10 Filter Exceed Traffic threshold NCell ................................................................15



1 Feature Attribute

BSC Version: [ZXG10 iBSC V6.30.103]

BTS Version: [Not related with BTS hardware platform]

Property: [Optional functionality]

Related Network Element:

NE Name Related or Not Special Requirements

MS -

BTS -

BSC √

MSC -

MGW -

SGSN -

GGSN -

HLR -

Dependent Function: [None]

Exclusive Function: [None]

Note: [None]

2 Overview

2.1 Feature Introduction

This feature enables the dynamic handover priority algorithm used in the target cells’

sequencing, controlling the handover direction and balancing the traffic between cells, so

as to reduce the interferences and improve voice quality as well.

This feature enables the dynamic priority algorithm for the target cells’ sequencing. The

user configures the different static priorities for different target cells according to the



geographic position, the traffic and the handover successful ratio of the cell.

ZTE GSM supports dynamic handover priority algorithm, which is composed of the static

priority and the traffic of cell. The static priority of cell has 8 levels from 0 to 7. Bigger the

number, higher the priority. The traffic of cell is reflected by the resource percentage of

TCH, which refers to the percentage of idle TCH proportion in total TCH in the cell,

ranging from 0 to 100. Higher the resource percentage of TCH, fewer loads of the cell

bear. The dynamic priority is gained with the resource percentage of TCH and the static

priority. When the same static priorities are set for two cells, the cell with low traffic has

high dynamic priority. It means that it’s much easier to get channel resources and

successfully handover.

2.2 License Control

None license control for this feature in UR12 Release.

2.3 Correlation with Other Features

The queuing of the target cells is for either a Emergency handover or a non-Emergency

handover. This feature is associated with the handover algorithm.

Please refer to ZGB-02-02-001 Basic Handover Feature Guide for detail.

3 Technical Description

When more than one adjacent cell is available for a handover operation, those cells shall

be queued and handover attempts are made to those cells by the queuing order.

When the switch is open, the target cells are sorted and filtered first by the cell traffic.

Then they are queued by the dynamic priority and PBGT level. When the switch is close,

they are only queued by the static priority and PBGT level.



Start

Is a Emergency handover?

Dynamic priority for

Emergency handover is

open?

Non Emergency handover

need to filter high load cell?

If the cell load of any cell in the

target cells list is bigger than the

filter thresholds, filter this cell

Dynamic priority for Non

Emergency handover is

open?

Y

N

Use the static priority for

target cell

Calculate the dynamic

priority for target cell

N

End

If the cell load of any cell in the

target cells list is 100, set the

priority of this cell to the lowest

Y

N

Cell Load bigger than the

Dynamic Priority NCell

Traffic Threshold?

Y Y

N

Y

N

3.1 Handover type classify

Handover Causes Type

Inter-cell handover is caused by high uplink BER. Emergency

Inter-cell handover is caused by high downlink BER. Emergency

Inter-cell handover is caused by low uplink level. Emergency



Inter-cell handover is caused by low downlink level. Emergency

Handover is caused by the large distance between MS and the

network.

Emergency

Inter-cell handover caused by the fast uplink fading. Emergency

Adjacent handover is caused by the PBGT value. Non

Emergency

Handover between a macro-cell and a micro-cell. Non

Emergency

Directed retry Non

Emergency

Handover candidate enquiry Non

Emergency

Forced handover caused by a directed transfer. Non

Emergency

A handover is caused by seizure. Emergency

A traffic handover caused by the database. Non

Emergency

3.2 Traffic value for the target adjacent cells

1. For an adjacent cell configured in the same CMP board, check the current traffic in

the database.

2. For an adjacent cell configured in the different CMP board or inter BSC, the traffic

information is saved in the CellLoad fields as the adjacent cell object data table

The traffic information has a life circle. The traffic information might be inaccurate if

the last update is much earlier than this handover judgment.

3. For an external cell (a GSM external cell or a 3G external cell) BSC stores the traffic

value in an external cell in the CellLoad related field. This field is in the object data

table R_3GNCEL of a 3G adjacent cell. This traffic value also requires a life circle

attribute.

4. If the service cannot find the traffic values of theadjacent cell and the external

adjacent cell in database, it uses the default value (0) as the load values of these

cells.



5. A parameter controls whether the traffic information of an external cell is extracted.

It is a BSC parameter.

3.3 Filter the high load target adjacent cells

The traffic queuing of the target adjacent cells is introduced below.

1. In an Emergency handover, the cells whose traffic is larger than the traffic threshold

are not filtered out. Then those cells not filtered out are queued by their traffic load.

The cells whose traffic load is 100 are put in the last place of target cell list. And the

cells whose traffic load less than 100 or equal to 100 are queued by their dynamic

priority and PBGT level respectively.

2. In a Non Emergency handover, if need to filter the high load cells, the cells whose

traffic is larger than the traffic threshold are filtered out. The cells remaining are

queued by their dynamic priority and PBGT level.

3. During the filtering, a cell’s traffic load is considered as 0 when the

non-local-module’s adjacent target cell traffic value in the database and the 3G

adjacent cell traffic value in the database are invalid.

3.4 Calculate the dynamic priority

Two algorithms are used to compute the handover priority. The static priority is effective

when the dynamic priority adjustment switch is not enabled or the neighbor cell load is

lower than the Dynamic Priority NCell Traffic Threshold. The static priority parameter

Hopriority is configured by OMCR. Its range is [0, 7] and the priority increases as the

value increases. The geological location of a cell is the major criterion in the static priority

configuration. An example is the microcells in a high building. The adjacent cells on the

same floor have higher priorities while the adjacent cells on different floors have lower

priorities. This is helpful to keep all the handovers on the same floor altitude and reduce

signal interference.



When the dynamic priority adjusting function is enabled, the priority of a cell is computed

with consideration to its static priority Hopriority, the cell resource ratio RescIndTh, and

the idle channel ratio in the adjacent cell. The computing formula is given below.

In this formula, the DynPriority value is the minimal integral that satisfies the conditions.

SatPriority is the static priority of a cell. DynPriority is the dynamic priority of a cell. Per is

the idle channel ratio (percentage) in an adjacent cell. Res_Ths refers to

RESOURCETHS, the resource percentage of a cell.

The resource percentage of a cell refers to the percentage of the idle TCH in the total

TCH in the cell. Its valid value is larger than 10 and not larger than 100. This is because

MS cares only the TCH of the destination cell during a handover process. The traffic in

the cell decreases as the TCH resource percentage increases. A low percentage value

means the channel is easy to access and the handover is easier to succeed.

3.5 Adjacent cells queuing

The queuing rules for the adjacent cells are introduced below.

First, queue the target cells by the dynamic priority index.

Compare with the dynamic priority offset, DynPrioOffset. If two cells have a same

dynamic priority or the difference between their priorities is less than DynPrioOffset,

queue them by the power budget margin.

When queuing destination cells, DynPrioOffset is used to identify the cells within the

same range of the dynamic priorities. The cells within the same range of the dynamic

priorities are then queued according to their power budget margins.

The handover algorithm based on the dynamic priority has a dynamic advantage. When

the TCH resources are abundant, its priority is high, and it can accept more handover

services. When the TCH resources are consumed, its priority become lower, and it can

Res_Ths

500ln

Res_Ths

5perlnyStaPriorityDynPriorit



accept less handover services. This is a control process based on negative feeding. It

can prevent unbalanced traffic sharing among cells.

4 Parameters and Configurations

4.1 Parameter List

Table 4-1 Parameter List

SN Name Figure

1 Allow dynamic adjustment of handover priority Figure 6-1

2 Minimal resource threshold Figure 6-2

3 Priority of handover Figure 6-3

4 Difference of dynamic priority Figure 6-4

5 Target cell traffic threshold Figure 6-5

6 Dynamic Priority NCell Traffic Threshold Figure 6-6

7 Non Emergency Handover use Dynamic Priority Figure 6-7

8 Emergency Handover use Dynamic Priority Figure 6-8

9 Filter Exceed Traffic threshold NCell Figure 6-9

4.2 Parameter Configuration

4.2.1 Allow dynamic adjustment of handover priority

Table 4-2 Configuration rule of allow dynamic adjustment of handover priority

Full name Allow dynamic adjustment of handover priority

Abbreviation hoControlPriChg

Description This parameter determines whether to allow dynamic adjustment

of handover priority.

Managed object Cell

Value range yes,no



Unit NA

Default value no

4.2.2 Minimal resource threshold

Table 4-3 Configuration rule of Minimal resource threshold

Full name Minimal resource threshold

Abbreviation resourceThs

Description This parameter indicates the minimal resource threshold allowed

by the cell. It is used to calculate dynamic cell priority

Managed object Cell

Value range 0-100

Unit %

Default value 20

4.2.3 Priority of handover

Table 4-4 Configuration rule of Priority of handover

Full name Priority of handover

Abbreviation HoPriority

Description

According to GSM specifications, cell priority should be considered

in sequencing candidate cells. Therefore, there are three decisive

factors to sequence candidate cells: priority, traffic, and radio

communication environment. Priority and traffic have the most

impact on cell sequencing. If they lead to the same result,

sequence cells by radio conditions. The priority of a cell is higher if

this value is set higher.

Managed object Cell

Value range 0-7

Unit N/A

Default value 3



4.2.4 Difference of dynamic priority

Table 4-5 Configuration rule of Difference of dynamic priority

Full name Difference of dynamic priority

Abbreviation dynPrioOffset

Description

This parameter defines a tolerable dynamic priority difference

between the destination cell and local cell during a handover when

using direction based handover algorithm. During handover, if the

first cells dynamic handover priority is higher than that of the

second cell but the second cell is in MS moving direction, then the

direction-based handover algorithm works if the difference

between the two cells’ handover priorities is within the tolerable

difference. MS is handover to the second cell.

Managed object Cell

Value range 1-7

Unit NA

Default value 1

4.2.5 Target cell traffic threshold

Table 4-6 Configuration rule of Target cell traffic threshold

Full name Target cell traffic threshold

Abbreviation TargetCellTrafficThs

Description

This parameter indicates the threshold for the target cell's traffic.

The system decides whether to perform handover to the cell

according to this parameter's value. If the traffic of the target cell is

higher than the threshold, handover is not made to the cell. This

parameter is used for 2G handover and reselecting adjacent cells.

Managed object Cell

Value range 0-100

Unit %

Default value 75



4.2.6 Dynamic Priority NCell Traffic Threshold

Table 4-7 Configuration rule of Dynamic Priority NCell Traffic Threshold

Full name Dynamic Priority NCell Traffic Threshold

Abbreviation DynPrioNCellTrafThs

Description

If the neighbor cell load is bigger than this threshold, the dynamic

priority will be calculated; otherwise the static priority will be used

as the dynamic priority.

Managed object Cell

Value range 0-100

Unit

Default value 0

4.2.7 Non Emergency Handover use Dynamic Priority

Table 4-8 Non Emergency Handover use Dynamic Priority

Full name Non Emergency Handover use Dynamic Priority

Abbreviation NonEmergHoDynPrio

Description

When the cell parameter "hoControlPrioChg" is enabled, this

parameter determines whether to calculate the dynamic priority of

a neighbor cell in the case of non-emergency handover.

Managed object Cell

Value range 0:No 1:Yes

Unit

Default value 0

4.2.8 Emergency Handover use Dynamic Priority

Table 4-9 Configuration rule of Emergency Handover use Dynamic Priority

Full name Emergency Handover use Dynamic Priority

Abbreviation EmergHoDynPrio



Description

When the cell parameter "hoControlPrioChg" is enabled, this

parameter determines whether to calculate the dynamic priority of

a neighbor cell in the case of emergency handover.

Managed object Cell


Unit

Default value 0

4.2.9 Filter Exceed Traffic threshold NCell

Table 4-10 Filter Exceed Traffic threshold NCell

Full name Filter Exceed Traffic threshold NCell

Abbreviation FiltExcdThsNCell

Description

In the case of non-emergency handover, "FiltExcdThsCell" is

supported to determine whether to filter the neighbor cells whose

traffic load exceeds the threshold. The switch does not depend on

the dynamic priority switch.

Managed object Cell


Unit

Default value 0

5 Related Counters and Alarms

5.1 Related Counters

There is no counter relative to this feature.

5.2 Related Alarms

This feature has no related alarms.



6 Engineering Guide

6.1 Application Scenario

It is recommended to split the traffic in a busy cell. Determine the priority of an adjacent

cell according to its traffic condition and its relative location to the initial cell. Set the

priority of an adjacent cell to a high level if it is close to the initial cell and its traffic is idle.

If it is not, set it to a lower priority level.

This priority setting can push the traffic from a busy cell to an idle cell. If the traffic is busy

in a cell of high static priority, the dynamic priority of this cell will be adjusted to avoid

congestion in this cell.

6.2 Configuration Description

1. In the window of Resource Tree Configuration, double click [GSM logic functionality

configuration →cell functionality configuration →handover control], and select

handover resource cell to double click in the cell list on the right window. Then set

‘Allow dynamic adjustment of handover priority’ in the popped [handover control]

sheet as the figure below.



Figure 6-1 Allow dynamic adjustment of handover priority


configuration →cell functionality configuration →GSM cell configuration], and select


‘Minimal resource threshold’ in the popped [GSM cell configuration] sheet as the

figure below.



Figure 6-2 Minimal resource threshold


configuration →cell functionality configuration →Adjacent cell configuration →GSM

Adjacent cell relation configuration], and select handover adjacent cell relation to

double click in the cell list on the right window. Then set ‘Priority of handover’ in the

popped [GSM adjacent cell relation configuration] sheet as the figure below.



Figure 6-3 Priority of handover


configuration →cell functionality configuration →handover control], and select

handover resource cell to double click in the cell list on the right window. Then set ‘A

Difference of dynamic priority’ in the popped [handover control] sheet as the figure

below.



Figure 6-4 Difference of dynamic priority


configuration →cell functionality configuration →Adjacent cell configuration →GSM

Adjacent cell relation configuration], and select handover adjacent cell relation to

double click in the cell list on the right window. Then set ‘Target cell traffic threshold’

in the popped [GSM adjacent cell relation configuration] sheet as the figure below.



Figure 6-5 Target cell traffic threshold




‘Dynamic Priority NCell Traffic Threshold’ in the popped [GSM cell configuration]




Figure 6-6 Dynamic Priority NCell Traffic Threshold




‘Non Emergency Handover use Dynamic Priority’ in the popped [GSM cell

configuration] sheet as the figure below.

Figure 6-7 Non Emergency Handover use Dynamic Priority






‘Emergency Handover use Dynamic Priority’ in the popped [GSM cell configuration]


Figure 6-8 Emergency Handover use Dynamic Priority




‘Filter Exceed Traffic threshold NCell’ in the popped [GSM cell configuration] sheet

as the figure below.

Figure 6-9 Filter Exceed Traffic threshold NCell



6.3 Feature Validation

6.3.1 Non Emergency handover Dynamic priority

Test Item Non Emergency handover Dynamic handover priority

Precondition 1. check CN is healthy;

2. check BSC is healthy;

3. check SDR is healthy;

4. check default cell configuration and parameters in

BSC;

5. MSs are ready;

6. ensure good radio environment;

Test Steps 1. Configure cell B and cell C as “Adjacent handover and

reselect cell” for Cell A.

2. Priority of cell B is higher than that of cell C. (for

example: Cell B’s priority is 7 and cell C’s priority is 5)

3. Set “Minimal resource threshold” of serving cell as

“15”.

4. Set ” Allow dynamic adjustment of handover priority”

as ’Yes’ in handover control;

5. Set “Non Emergency Handover use Dynamic Priority”

as ‘Yes’;

6. Rx_level of cell B > Rx_level of cell C > Rx_level of cell

A

7. Set “Difference of dynamic priority” as default value 0

8. MS make a call occupied in cell A

9. Move MS far away from cell A until Non Emergency

handover.

10. Make some calls in cell B to make idle channel

percentage is not more than ’ TargetCellTrafficThs’;

11. Repeat step 8-10.

Anticipative Result 1. In step 9, MS handover successfully , and target cell is

cell B after evaluate the dynamic priority of all target

cells

2. In step 11, MS handover successfully , and target cell

is cell C due to evaluate the dynamic priority of all

target cells

Test Result Non Emergency handover Dynamic priority is effective

Parameters Setting Default parameters



6.3.2 Emergency handover Dynamic priority

Test Item Emergency handover Dynamic priority





BSC;

5. MSs are ready;




2. Priority of cell B is higher than that of cell C. (for

example: Cell B’s priority is 7 and cell C’s priority is 5)

3. Set “Minimal resource threshold” of serving cell as

“15”.

4. Set ” Allow dynamic adjustment of handover priority”

as ’Yes’ in handover control;

5. Set “Emergency Handover use Dynamic Priority” as

‘Yes’;


A

7. Set “Difference of dynamic priority” as default value 0


9. Move MS far away from cell A until emergency

handover.


percentage is not more than ’TargetCellTrafficThs’;

11. Repeat step 8-10.

Anticipative Result 1. In step 9, MS handover successfully , and target cell is

cell B after evaluate the dynamic priority of all target

cells

2. In step 11, MS handover successfully , and target cell

is cell C due to evaluate the dynamic priority of all

target cells

Test Result Emergency handover Dynamic priority is effective


6.3.3 Non Emergency handover filter high load NCell

Test Item Non Emergency handover filter high load NCell







BSC;

5. MSs are ready;




2. Priority of cell B is same as cell C. (for example: Cell

B’s priority is 5 and cell C’s priority is 5)

3. Set “Filter Exceed Traffic threshold NCell” as ‘Yes’;


A


6. Move MS far away from cell A until handover.


percentage is no more than ’ TargetCellTrafficThs’ but

bigger than ‘FiltExcdThsNCell’;

8. Repeat step 6-7.

Anticipative Result 1. In step 6, MS handover successfully, and target cell is

cell B.

2. In step 7, MS handover successfully, and target cell is

cell C due to cell B is filtered.

Test Result Non Emergency handover filter high load NCell


6.4 Feature Turn off

In the window of Resource Tree Configuration, double click [GSM logic functionality

configuration →cell functionality configuration →handover control], and select handover

resource cell to double click in the cell list on the right window. Then set ‘Allow dynamic

adjustment of handover priority’ as “No”.



Figure 6-10 Close the function of Allow dynamic adjustment of handover priority

6.5 Network Impact

Dynamic priority can adjust cell traffic load flexibly. If the cell static priority is high, the

priority will be lower with the traffic load increase. It is avoided that all the handover are to

the cell with high static priority so as to make heavy traffic. After using dynamic priority,

priority can be adjusted according to traffic. When traffic is heavy, the priority becomes

low. This feature can realize traffic balance.

In addition, the target adjacent cell which has the highest level may not be selected as

the final target cell due to the high load, so this feature may influence the Handover

Success Rate.

7 Abbreviation Abbreviations Full Characteristics

3GPP 3rd

Generation Partnership Project

BER Bit Error Rate

BSC Base Station Controller

BTS Base Transceiver Station



GGSN Gateway GPRS Support Node

GSM Global System for Mobile Communications

HLR Home Location Register

MGW Media GateWay

MS Mobile Station

MSC Mobile Service Switching Centre

SGSN Serving GPRS SUPPORT NODE

TCH Traffic Channel

8 Reference Document

ZXG10 iBSC (V6.30.10) Base Station Controller Radio Parameter Reference

ZGO-02!02!002 Dynamic Handover Priority Algorithm Feature Guide ZXG10 IBSC (V12.3.0)20131108

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Transcript of ZGO-02!02!002 Dynamic Handover Priority Algorithm Feature Guide ZXG10 IBSC (V12.3.0)20131108