Wcdma Rno Handover Algorithm Analysis And Parameter Configurtaion Guidance 20050316 A 1.0

Product Version Confidentiality level
Huawei Technologies V100R001 For Internal Use
Co. Ltd. Product Name: WCDMA RNP Total pages: 52

WCDMA RNO Handover
Algorithm Analysis and
Parameter Configuration
Guidance
For internal use only

Prepared by: URNP-SANA Date: 2003-12-15
Reviewed by: Date:
Reviewed by: Date:
Approved by: Date:

Huawei Technologies Co., Ltd.

All rights reserved

WCDMA RNO Handover Algorithm Analysis and Parameter
Configuration Guidance For Intanal Use

Revision Record
Date Rev. Description Author
Version
2003/12/15 Initial transmittal Znag Liang
2005/03/16 1.0 Change the date, no content updated. Qinyan

10-1-26 Confidential Page 2 of 52


Table of Contents
1 Introduction..................................................................................................................................................7
2 Handover Algorithm Analysis.....................................................................................................................7
2.1 Handover Measurement ..........................................................................................................................7
2.1.1 Intra-Frequency Measurement .........................................................................................................8
2.1.2 Inter-Frequency Measurement .......................................................................................................13
2.1.3 Inter-System Measurement ............................................................................................................14
2.1.4 UE Internal Measurement ..............................................................................................................15
2.2 Handover Algorithms ...........................................................................................................................16
2.2.1 Softer Handover and Soft Handover Algorithms ...........................................................................16
2.2.2 Intra-Frequency Hard Handover Algorithm ..................................................................................17
2.2.3 Inter-Frequency Hard Handover Algorithm ..................................................................................17
2.2.4 Inter-System Handover Algorithm .................................................................................................19
2.2.5 Handover Caused by Load Balancing ............................................................................................19
2.2.6 Cell Penalty.....................................................................................................................................20
2.2.7 Active Set Synchronization Maintenance.......................................................................................21
2.2.8 Direct Retry Algorithm ..................................................................................................................22
2.2.9 Principle for Generating Adjacent Cell List...................................................................................23
3 Handover Parameter Setting ......................................................................................................................24
3.1 Description.............................................................................................................................................25
3.2 Handover Common Parameters ............................................................................................................26
3.2.1 Maximum Number of Cells in Active Set......................................................................................26
3.2.2 Penalty Time....................................................................................................................................26
3.2.3 Event 6F Trigger Threshold ...........................................................................................................27
3.2.4 Event 6G Trigger Threshold...........................................................................................................27
3.2.5 Time-to-Trigger Parameters for Events 6F and 6G........................................................................28
3.2.6 BE Service Handover Rate Decision Threshold ............................................................................28
3.2.7 Soft Handover Method Select Switch ............................................................................................29
3.2.8 Handover Algorithm Switches........................................................................................................30
3.3 Intra-Frequency Handover Measurement Algorithm Parameters ........................................................31
3.3.1 Soft Handover Relative Thresholds ...............................................................................................31
3.3.2 Soft Handover Absolute Thresholds ..............................................................................................32
3.3.3 Intra-Frequency Measurement Filter Coefficient (FilterCoef).......................................................33
3.3.4 Hysteresis Related to Soft Handover .............................................................................................35
3.3.5 Time-to-Trigger Parameters Related to Soft Handover..................................................................36
3.3.6 WEIGHT.........................................................................................................................................37
3.3.7 Detected Set Statistics Switch.........................................................................................................38
3.4 Inter-Frequency Handover Algorithm Parameters ...............................................................................38
3.4.1 Inter-Frequency Measurement Filter Coefficient (FilterCoef).......................................................38
3.4.2 Cell Location Property....................................................................................................................39
3.4.3 Hysteresis Related to Inter-Frequency Handover...........................................................................40
3.4.4 Time-to-Trigger Parameters Related to Inter-Frequency Hard Handover.....................................41
3.4.5 Compressed Mode Enable/Disable Threshold Denoted by RSCP.................................................42
3.4.6 Compressed Mode Enable/Disable Threshold Denoted by Ec/No.................................................42
3.4.7 Inter-Frequency Hard Handover RSCP Threshold ........................................................................43
3.4.8 Inter-Frequency Hard Handover Ec/No Threshold ........................................................................44
3.5 inter-system handover measurement algorithm parameter ..................................................................44
3.5.1 inter-system measurement filter coefficient FilterCoef..................................................................44
3.5.2 Inter-System Hard Handover Decision Threshold .........................................................................45
3.5.3 Inter-system Hard Handover Hysteresis .......................................................................................45
3.5.4 Time-to-Trigger Parameter for Inter-System Hard Handover........................................................46
3.5.5 Inter-System Measurement Periodic Report Interval.....................................................................47
3.6 Compressed Mode Algorithm Parameter .............................................................................................47
3.6.1 CFN Offset to Enable Compressed Mode.......................................................................................47



3.6.2 Spreading Factor Threshold ...........................................................................................................48
3.7 Direct Retry Algorithm Parameter .......................................................................................................49
3.7.1 Maximum Direct Retry Times........................................................................................................49
3.7.2 Candidate Set Absolute Threshold .................................................................................................49
3.7.3 Minimum Ec/No Value...................................................................................................................50
3.7.4 Linear Factor of Relative Threshold and Time Interval.................................................................50
3.7.5 Maximum Relating Time for Direct Retry Decision......................................................................51



List of Tables
table 1Recommended Soft Handover Hysteresis Settings for Different Movement Speeds.......................35
table 2Recommended Time-to-Trigger Settings for Different Movement Speeds......................................36
table 3Recommended Inter-Frequency Hard Handover Hysteresis Settings for Different Movement
Speeds..........................................................................................................................................................40
table 4Recommended Inter-Frequency Hard Handover Time-to-Trigger Settings for Different Movement
Speeds..........................................................................................................................................................41

List of Figures
Figure 1 Measurement Model.........................................................................................................................8
Figure 2 Example of Event 1A and Trigger Delay.........................................................................................9
Figure 3 Periodic Reporting Triggered by Event 1A....................................................................................10
Figure 4 Example of Event 1C......................................................................................................................11
Figure 5 Example of Event 1D......................................................................................................................11
Figure 6 Restriction of measurement reporting by means of hysteresis.......................................................12
Figure 7 Example of Event 1E......................................................................................................................12
Figure 8 Example of Event 1D1F.................................................................................................................13
Figure 9 Power Control Timing....................................................................................................................21
Figure 10 MML Client .................................................................................................................................25



Configuration Guidance

Key words: handover algorithm, soft handover, hard handover, inter-system handover,
parameter setting
Abstract: This document first describes the measurements involved in the handover algorithms,
and then analyzes the measurement control and decision rules in the implementation of
the algorithm of each type of handover. Finally, it provides a detailed guidance for the
setting of various types of handover parameters, so that correct and effective handover
parameter adjustments can be carried out based on the actual requirements during
network optimization.
List of abbreviations: (Omitted)



1 Introduction

Handover types include softer handover, soft handover, intra-frequency hard handover,
inter-frequency hard handover and inter-system hard handover. A typical handover process is:
measurement control → measurement report → handover decision → handover execution →
new measurement control. Based on the measurement value, handover control method and
handover type selection required for the handover decision, the handover algorithm determines
how the UE carry out handover measurements and report the measurement result, and then
makes handover decision and guides the handover execution according to the reported
measurement result. Handover algorithms largely present themselves in the configuration of
measurement control parameters.

In Chapter 2, this document discusses the measurement control, reporting rules and related
handover decision algorithms involved in various types of handover. In Chapter 3, based on the
knowledge of the handover algorithms, this document provides detailed descriptions of the
specific parameter setting methods value assignment recommendations and ranges of effect of
the related algorithms of various types of handover, so as to provide a clear and practical
guidance for parameter adjustments in network optimization.

2 Handover Algorithm Analysis

Mobility management is an important part of radio resource management, while handover
algorithms are the most important part of mobility management. A handover algorithm involves
such contents as measurement control and handover decision. Therefore, to analyze a handover
algorithm, we should first analyze handover measurement.

2.1Handover Measurement

The radio resource management module (RRM) initiated measurements include dedicated
measurement and common measurement. All the measurements in the UE are dedicated
measurement. Handover measurement is specific to the physical layer, which provides
measurement of various items for the higher layers, so as to trigger various functions, including
handover.

The measurement result will go twice through smoothening processing. The first processing
is in the physical layer, and the purpose is to filter off the influence of fast fading before the
physical layer reports the measurement result to the higher layer. The second processing is
implemented by the higher layer on the measurement result reported by the physical layer before
event evaluation. This processing is to determine the filter coefficient according to the time



relation and implemented weighted averaging processing of the measurement result. The latest
measurement result after L3 filtering is used for evaluation of the reporting rule, and as the
reported result. The process is as follows:

Parameter Parameter

A L1 B L3 C Evaluation D
filtering filtering of reporting
rule
C'

Figure 1 Measurement Model

The reporting types include “on-demand reporting”, “periodic reporting” and “event triggered
reporting” (Event A to Event F). Generally, the last two types of measurement reporting are
involved in handover.

In the UE, measured cells are divided into the following three types:
 Active set cells: Cells in an active set communicate with the UE simultaneously. Active set
cells refer to those that are demodulated and correlatively combined at the UE and
communicate with the UE in the FDD mode, namely in soft handover and softer handover.
Cells in an active set are surely intra-frequency cells.
 Monitored set cells: Among the cells included in the adjacent cell list delivered by the RNC,
some adjacent cells may have already entered the active set at the time of soft handover,
and the remaining cells are in monitored sets. Monitored sets include intra-frequency
monitored sets, inter-frequency monitored sets and inter-system monitored sets.
 Detected set cell: Detected set cells refer to those cells detected by the UE itself, rather than
the cells in the active sets and monitored set.

The types of measurement involved in handover include intra-frequency measurement,
inter-frequency measurement and inter-system measurement, which will be discussed in the
following paragraphs.

2.1.1Intra-Frequency Measurement

UTRAN uses the measurement control message to inform the UE what events need to
trigger measurement reporting. All intra-frequency measurement report events are identified with
1X.
Event 1A: A primary pilot channel enters the reporting range
If the network, in the measurement report mechanism field, requires the UE to report event



1A while the UE has entered the Cell_DCH state, then when a primary pilot channel enters the
reporting range, the UE will send a measurement report.

When the measurement values satisfy the following formulas, the UE deems that a primary
pilot channel has entered the reporting range:
1. Path loss:
 NA 
10 ⋅ LogM New ≤ W ⋅10 ⋅ Log  ∑ M i  + (1 − W ) ⋅10 ⋅ LogM Best + ( R − H 1a / 2),
 
 i =1 
2. Other measurement values:
 NA 
10 ⋅ LogM New ≥ W ⋅10 ⋅ Log  ∑ M i  + (1 − W ) ⋅10 ⋅ LogM Best − ( R − H 1a / 2),
 
 i =1 
Where,
MNew is the measurement result of the cell that has entered the reporting range
Mi is the measurement result of the cells in the active set
NA is the number of cells in the current active set
MBest is the measurement result of the best cell in the current active set
W is the weight factor
R is the reporting range. With the signal strength as an example, R equals to the signal strength
of the best cell in the current active set minus a value
H1a is the hysteresis value of event 1A

In order to reduce the signaling traffic flow of the measurement report, the TIME-TO-
TRIGGER parameter is used so that the UE will not trigger measurement reporting before the
primary pilot enters the reporting range and is maintained for a certain period of time. This
parameter is also used in other events. An example of measurement reporting triggered by event
1A is given below:

Measurement
quantity
P CPICH 1
Reporting
range

P CPICH 2

P CPICH 3 Time-to-trigger

Reporting Time
event 1A

Figure 2 Example of Event 1A and Trigger Delay

Generally, if event 1A is triggered, the UE will send a measurement report to UTRAN, and
UTRAN will deliver an ACTIVE SET UPDATE signaling message to update the active set.



However, UTRAN may give no response after the UE sends the measurement report (for
example, due to insufficient capacity). In this case, the UE will shift from event reporting to
periodic reporting mechanism, and the content of the measurement report includes the
information of the cells in the active set and the cells in the monitored set that has entered the
reporting range. The UE will not stop sending periodically the measurement report until this cell
is successfully added into the active set or leaves the reporting range, as shown below:

PCPICH 1

PCPICH 2

Reporting
range
Reporting
terminated

Periodic Periodic
report report
Event-triggered
PCPICH 3
report

Figure 3 Periodic Reporting Triggered by Event 1A

Event 1B: A primary pilot channel leaves the reporting range
When the following formulas are satisfied, the UE deems that a primary pilot channel has left
the reporting range
1, Path loss:
 NA 
10 ⋅ LogM Old ≥ W ⋅ 10 ⋅ Log  ∑ M i  + (1 − W ) ⋅ 10 ⋅ LogM Best + ( R + H 1a / 2),
 
 i =1 
2, Other measurement values:
 NA 
10 ⋅ LogM Old ≤ W ⋅ 10 ⋅ Log  ∑ M i  + (1 − W ) ⋅ 10 ⋅ LogM Best − ( R + H 1b / 2),
 
 i =1 
Where,

MOld is the measurement result of the cell that has left the reporting range
Mi is the measurement result of the cell in the active set
NA is the number of cells in the current active set
MBest is the measurement result of the best cell in the current active set
W is the weighted factor
R is the reporting range
H1a is the hysteresis value of event 1A
If several cells satisfy the reporting condition simultaneously after the trigger delay, the UE



will sort the cells according to the measurement values and report all the measurement results.

Event 1C: The primary pilot channel in a non active set is better than the primary pilot
channel in an active set
This event can be described through the following example:

Measurement
quantity
P CPICH 1

P CPICH 2

P CPICH 3

P CPICH 4

Reporting Reporting Time
event 1C event 1C

Figure 4 Example of Event 1C
In this example, the cells where P CPICH 1, P CPICH 2 and P CPICH 3 are belong to an
active set, while that of P CPICH 4 does not. This event is used to replace the poor cells in the
active set, if the number of cells in the active set reaches or exceeds active set replacement
threshold.

Event 1D: The best cell changes

Measurement
quantity
P CPICH 1

P CPICH 2

P CPICH3

Reporting Time
event 1D

Figure 5 Example of Event 1D



In order to prevent frequent triggering of event 1D due to signal fluctuations when the
channel difference is small, which results in unnecessary increase of the air interface signaling
traffic flow, we can use the hysteresis parameter, as shown below:

Measurement
quantity
P CCPCH 1
Hysteresis

P CCPCH 2

Hysteresis

Reporting Time
event 1D

Figure 6 Restriction of measurement reporting by means of hysteresis

As we can see, as the hysteresis condition is not met at the second time, event 1D
reporting is not triggered. This parameter can also be used in other events.

Event 1E: The measurement value of a primary pilot channel exceeds the absolute
threshold

Measurement
quantity
P CPICH 1

P CPICH 2
Absolute
threshold

P CPICH 3

Reporting Time
event 1E

Figure 7 Example of Event 1E

Event 1E can be used to trigger the measurement reports of cells including those detected
by the UE before it receives the adjacent cell list.



Event 1F: The measurement value of a primary pilot channel is lower than the absolute
threshold

Measurement
quantity
P CPICH 1

P CPICH 2
Absolute
threshold
P CPICH 3

Reporting Time
event 1F

Figure 8 Example of Event 1D1F

2.1.2Inter-Frequency Measurement

Inter-frequency measurement events are identified with 2X. The frequency quality
estimation involved in events 2A, 2B, 2C, 2D and 2E is defined as follows:

 NA j 
Qcarrier j = 10 ⋅ LogM carrier j = W j ⋅ 10 ⋅ Log  ∑ M i
 i =1 j
 + (1 − W j ) ⋅ 10 ⋅ LogM Best j − H ,

 
Where,
Qcarrierj is the logarithmic form of the estimated quality value of frequency j
Mcarrier j is the estimated quality value of frequency j
Mi j is the measurement result of cell i with the frequency of j in the virtual active set
NA j is the number of cells with the frequency of j in the virtual active set
MBest j is the measurement result of the best cell with the frequency of j in the virtual active set
Wj is the weight factor
H is the hysteresis value

Before we describe events 2x, we should make the following two concepts understood:
“non-used frequency” refer to the frequency that the UE needs to measure but that is not in the
active set, and “used frequency” refers to the frequency that the UE needs to measure and that
is in the active set.



Event 2A: The best frequency changes
If the estimated quality value of the non-used frequency is better than that of the best cell in
the used frequency, and the hysteresis value and the “time to trigger” conditions are satisfied,
event 2A will be triggered.

Event 2B: The estimated quality value of the used frequency is lower than a certain
threshold, and that of the non-used frequency is higher than a certain threshold
If the estimated quality value of the used frequency is lower than the threshold defined by IE
“Threshold used frequency” delivered in the measurement control message, while that of the
non-used frequency is higher than the threshold defined by IE “Threshold non-used frequency”
delivered in the measurement control message, and the hysteresis value and the “time to trigger”
condition are satisfied, event 2B will be triggered.

Event 2C: The estimated quality value of the non-used frequency is higher than a
certain threshold
This threshold is specified by IE “Threshold non-used frequency” in the measurement
control message delivered by UTRAN.

Event 2D: The estimated quality value of the used frequency is lower than a certain
threshold
Event 2D can be used to enable the compressed mode to perform inter-frequency
measurement. This threshold is specified by IE “Threshold used frequency” in the measurement
control message delivered by UTRAN. This type of parameters can be modified through MML
commands.

Event 2E: The estimated quality value of the non-used frequency is lower than a
certain threshold
This threshold is specified by IE “Threshold non-used frequency” in the measurement

Event 2F: The estimated quality value of the used frequency is higher than a certain
threshold
Event 2F can be used to disable the compressed mode to stop inter-frequency
measurement. This threshold is specified by IE “Threshold used frequency” in the measurement

2.1.3Inter-System Measurement



Inter-system measurement events are identified with 3X. The quality estimation of a UTRAN
active set involved in events 3A, 3B, 3C and 3D is defined as follows:

 NA 
QUTRAN = 10 ⋅ LogM UTRAN = W ⋅ 10 ⋅ Log  ∑ M i  + (1 − W ) ⋅ 10 ⋅ LogM Best ,
 
 i =1 
Where,
QUTRAN is the logarithmic form of the estimated quality value of the UTRAN frequency currently in
use

MUTRAN is the estimated quality value of the UTRAN frequency currently in use

Mi is the measurement result of cell i in the active set

NA is the number of cells in the active set

MBest result is the measurement result of the best cell in the active set

W is the weight factor

Event 3A: The estimated quality value of the used UTRAN frequency is lower than a
certain threshold, and that of the other system is higher than a certain threshold
If the estimated quality value of the used UTRAN frequency is lower than the threshold
defined by IE “Threshold own system” delivered in the measurement control message, while that
of the other system is higher than the threshold defined by IE “Threshold other system” delivered
in the measurement control message, and the hysteresis value and the “time to trigger” condition
are satisfied, event 3A will be triggered.

Event 3B: The estimated quality value of the other system is lower than a certain
threshold
This threshold is specified by IE “Threshold other system” in the measurement control
message.

Event 3C: The estimated quality value of the other system is higher than a certain
threshold
This threshold is specified by IE “Threshold other system” in the measurement control
message.

Event 3D: The best cell in the other system changes

2.1.4UE Internal Measurement
Two UE internal measurement events are involved in the handover algorithms: 6F and 6G.
Event 6F: The time difference between downlink receiving and uplink transmission of
the UE is bigger than an absolute threshold
This threshold is specified in IE “UE Rx-Tx time difference threshold” delivered by UTRAN.



Event 6G: The time difference between downlink receiving and uplink transmission of
the UE is smaller than an absolute threshold
This threshold is specified in IE “UE Rx-Tx time difference threshold” delivered by UTRAN.

2.2Handover Algorithms

This section will describer the handover-related algorithms already supported by RNC V1.2,
so as to provide algorithm guidance for network optimization and parameter adjustments. The
contents of this section include softer handover and soft handover algorithms, intra-frequency
hard handover algorithm, inter-frequency hard handover algorithm, inter-system hard handover
algorithm, load balancing handover algorithm, cell penalty, direct retry algorithm and active set
synchronization maintenance and adjacent cell list maintenance method.

2.2.1Softer Handover and Soft Handover Algorithms

Presently, RNC V1.2 uses two soft handover algorithms: loose-mode algorithm and relative
threshold algorithm. The user can make selection between these two algorithms through the
algorithm switch. By default, algorithm 2, namely, relative threshold algorithm is enabled.

1. Loose-mode algorithm

1) When either event 1A or event 1E (referred to as “1A or 1E”) is satisfied, it will be
deemed as the trigger condition for adding a soft handover branch;

2) After event 1A or 1E is received, if the number of cells in the active set is 3, no
processing will be implemented.

3) When neither the relative threshold nor the absolute threshold (event 1B and 1F) is
satisfied, it is deemed as the trigger condition for removing a soft handover branch.

4) If handover is triggered when either event 1B or event 1F is received, but the triggered
cell is the best cell, then no processing will be made.

5) When the UE active set is full, event 1A and event 1E reporting is stopped, and event 1C
reporting starts

6) Event 1C is the trigger condition for cell replacement in the active set.

7) Event 1D occurs in the active set cell, and measurement control changes, based on the
best cell operation algorithm.

8) Event 1D occurs in the monitored set cell, and this cell is added into the active set. If the
active set is full, remove any cell among non-best cells and then add the reported best cell, and
mark it as the best cell. After successful operation, the measurement control change process is
started.



2. Relative threshold algorithm

1) When event 1A report is received, if the active set is not full, then links are sequenced
and added in the order of good quality to poor quality (CPICH Ec/No) (in case that multiple cells
report event 1A), until the active set is full; if the active set is already full, no processing will be
made.

2) When event 1B is received, if there are more than one links in the active set, then the
braches are sequenced and removed in the order of poor quality to good quality (CPICH Ec/No)
(in case that multiple cells report event 1B), until only one link is left; if there is only one in the
active set, no processing will be made.

3) In case of event 1C, the UE will report the replacing and replaced cells in the event
trigger list. If the active set is not full, then the triggered cell link will be added; if the active set is
already full at this moment and the replaced cell is not the best cell in the active set, then this cell
link will be removed.

4) In case of event 1D, if the triggered cell is an active set cell, then it will be marked as the
best cell and measurement control is updated; if the triggered cell doe not belong to the active
set, then this cell link will be added (if the active set is full, one of the non-best cell will be
removed before this link is added) and marked as the best cell, with measurement control
updated.

2.2.2Intra-Frequency Hard Handover Algorithm

Intra-frequency hard handover will occur in two cases: 1, handover between intra-frequency
adjacent cells that belong to different RNCs, between which no Iur interface is available; 2,
handover of high-rate PS Best Effort services that exceeds the rate threshold, because too much
forward capacity will be occupied if soft handover is adopted in this case.

Event 1D is used as the judgment criterion for event intra-frequency hard handover.
Namely, the event 1D triggered cell acts as the target cell of the handover.

2.2.3Inter-Frequency Hard Handover Algorithm

1. Basic concepts

Carrier coverage verge cell: a cell located at the outmost verge of a carrier coverage area.
The characteristic is that the cell does have an intra-frequency adjacent cell in a certain direction.



Carrier coverage center cell: a cell other than carrier coverage verge cells. The
characteristic is that the cell has intra-frequency adjacent cells in all directions.

In a carrier coverage verge cell, when the UE moves towards the direction in which the cell
has no intra-frequency adjacent cell, the CPICH Ec/No changes slowly because CPICH RSCP
has the same speed with the fading of interference. Simulation shows that CPICH Ec/No can still
reach -12dB or so when CPICH RSCP is already lower than the demodulation threshold (about
-110dBm). At this moment, the inter-frequency handover algorithm based on CPICH Ec/No
measurement has actually failed. Therefore, for a carrier coverage verge cell, it is more suitable
and more efficient to use CPICH RSCP as the inter-frequency measurement quantity.

For a carrier coverage center cell, CPICH RSCP can also be used as the inter-frequency
measurement quantity, but CPICH Ec/No can better reflect the actual link communication quality
and the load situation of the cell.

2. Enabling/disabling inter-frequency measurement

Because inter-frequency measurement may use the compressed mode, which usually
affects the link quality and system capacity, we generally hope that inter-frequency measurement
is not enabled unless necessary. Currently, RNC V1.2 decides to enable or disable inter-
frequency measurement through the reporting of event 2D and event 2F.

When the UE enters the CELL_DCH state or when the best cell is updated, if the inter-
frequency handover algorithm is enabled and an inter-frequency adjacent cell list is available for
the best cell, then the measurement of event 2D and 2F is configured. The absolute thresholds
of events 2D and 2F are the enabling/disabling thresholds of inter-frequency measurement.
CPICH Ec/No or RSCP measurement quantity and thresholds will be adopted respectively
according to the location property of the best cell in the active set (carrier coverage center or
carrier coverage verge as previously described). If the measurement quantity is lower than the
enabling threshold , event 2D will be reported, and inter-frequency measurement will be enabled
through decision; if the active set quality rises and becomes higher than the disabling threshold,
then event 2F reporting will be triggered and inter-frequency measurement will be stopped.

3. Inter-frequency hard handover decision

Presently, the periodic measurement reporting mode is used for inter-frequency
measurement. In RNC V1.2, the absolute threshold decision method based on cell properties is
used for inter-frequency handover decision. According to different cell properties (carrier
coverage verge cell and carrier coverage center cell), different physical measurement quantities
(CPICH RSCP and CPICH Ec/No) and handover thresholds are used for handover decision.

Based on the inter-frequency measurement result periodically reported by the UE, if the
measurement values exceed the absolute threshold and the hysteresis values and the “time to



trigger” condition is met, then the RNC will implement inter-frequency hard handover with the
reported cell as the handover target cell.

Note: Due to lack of a special compressed mode control policy, it is recommended that
inter-frequency handover be used only for necessary handover caused by discontinuous carrier
coverage. In this case, we can consider to enable the compressed mode only at the carrier
coverage verge, while disable the compressed mode at the carrier coverage center by means of
parameter configuration (by setting the absolute threshold of event 2D to the minimum) to
disable inter-frequency hard handover.

2.2.4Inter-System Handover Algorithm

RNC V1.2 supports 3G->GSM/GPRS handover. Presently, inter-system handover is used
only for inter-system handover caused by discontinuous coverage of 3G networks, and other
types of inter-system handover, such as load balancing, are not supported.

1) Inter-system handover is enabled only in cells located at the verge of WCDMA FDD
system coverage.

2) Inter-system handover algorithms and inter-frequency handover algorithms are mutually
exclusive. That is, when the compressed-mode measurement of inter-system handover is
enabled, the compressed-mode measurement of inter-frequency handover must be disabled.

3) Cells at the verge of WCDMA FDD system coverage are identified through the
configuration of GSM/GPRS adjacent cell list for them.

4) For inter-system handover, CPICH RSCP is used as the physical measurement quantity
and events 2D and 2F are used to decide enabling or disabling the compressed mode.

5) For inter-system handover, three compressed mode style sequences are used for
concurrent measurement of GSM RSSI, BASIC identification and BASIC reconfirm, and the
configuration of parameters is oriented to the cell type, namely, the parameters can be selected
and configured based on the cell characteristics and user mobility statistics characteristics.

6) Periodic measurement reports are used for inter-system handover, and the RNC decides
whether to implement hard handover according to the measurement reports.

2.2.5Handover Caused by Load Balancing

When the loads of the adjacent cells become unbalanced, the load control algorithm will
balance the loads between the adjacent cells through handover. Generally, the algorithm
implements load balancing by changing the power of the common pilot channel between
adjacent cells. Since handover algorithms obtain the Ec/No of the common pilot channel of



adjacent cells through the measurement by the UE, while the handover thresholds of various
cells are also obtained through the RNC database, the load balancing control algorithm is
transparent to handover algorithms, without any direct interface in between.

When the loads become unbalanced among cells of different frequencies in the same Node
B, the performance of the entire system may deteriorate. In this case, the load control algorithm
will notify the handover algorithm to switch some UEs on heavy-load carries onto light-load
carriers thus to balance the loads. At this time, the load control entity selects the specific UEs.
Upon selecting the UEs, the load control entity sends the source cell information and the target
cell information to the selected UEs’ Handover Control entities , and what the handover entity
should to do is just to give out the handover command based on the message it has received.

Load balancing between different NodeBs is transparent to the handover algorithm.
Therefore, we mainly analyze handover requests caused by load balancing between different
carriers in the same coverage area. In this kind of handover, the handover entity actually does
not make any specific decision, but it only “forwards” the decision command made by the load
control entity. In this kind of handover, two principles are followed for UE selection:

(1) UEs in soft handover are not selected. Since the target cell’s synchronization
information may be unavailable, the timming re-initiation hard handover procedure is used here.
As RNC V1.2 does not support immediate macro diversity, if a UE in soft handover state is
selected at this moment for load transfer, it will necessarily result in damage to the soft handover
state of this UE, and increase call drop risk.

(2) UEs with inconsistent SRNC and CRNC are not selected, because this kind of transfer
involves signaling interworking on the Iur interface, while the Iur is an open interface, without this
type of signaling.

Upon receiving the load transfer signaling, the handover entity first implements handover
decision to judge whether the two conditions previously mentioned are satisfied. If so, it will
proceed with the next step of processing; otherwise, it will reject the request and indicate the
reason.

2.2.6Cell Penalty

The purpose of cell penalty caused by handover failure is to prevent the handover algorithm
from deciding again on the handover of this UE to a cell that already has no more capacity. In
order to avoid making redundant judgments, in case of a handover failure (including soft
handover and hard handover), the involved UE will be restricted from initiating any further
handover request to the same cell within the penalty time, and the event periodic reporting
interval is required to be equal to the penalty time. Thus, after a handover failure, on one hand



penalty is exerted on the target cell involved in the handover failure, and on the other the periodic
reporting interval is made equal to the penalty time, so that large waste of processing capability
is avoided.

The Connection-oriented cell penalty algorithm is as follows:

(1) The cell penalty algorithm is to deny any handover access to the cell in penalty within
the specified period of time, namely, the involved UE is not allowed to initiate any further
handover request to this cell. The penalty flag is set to 1;

(2) After the penalty time expires, the penalty is released, and the penalty flag is set to 0.

2.2.7Active Set Synchronization Maintenance

According to the 25.214 protocol, from the downlink receiving moment of the UE to the
corresponding uplink transmission moment, there should be a 1024-chip delay, so as to ensure
the normal 1-slot uplink and downlink power control, as shown below:
Slot (2560 chips)

DL DPCCH T TF T
PILOT Data1 P CI Data2 PILOT Data1 P
at UTRAN
C C

Propagation delay
DL-UL timing Response
offset (1024 chips) To TPC (*3)

DL DPCCH T TF T
PILOT Data1 P CI Data2 PILOT Data1 P
at UE C
C
512 chips
DL SIR
measurement (*1) Response
to TPC

UL DPCCH
PILOT TFCI TPC PILOT
at UE

Slot (2560 chips)
Propagation delay UL SIR
measurement (*2)

UL DPCCH
PILOT TFCI TPC PILOT
at UTRAN

*1,2 The SIR measurement periods illustrated here are examples. Other ways of measurement are allowed to achieve
accurate SIR estimation.
*3 If there is not enough time for UTRAN to respond to the TPC, the action can be delayed until the next slot.

Figure 9 Power Control Timing

As illustrated in the diagram, when the UE complete receiving the downlink PILOT bit, it has
the time of 512 chips to generate the TPC bit for downlink power control according to the PILOT



bit. When the UE is in the soft handover state, the generation of the TPC bit should be based on
the PILOT calculation of all links. However, in the actual system, because the selection of the
downlink transmission time is obtained by the NodeB based on the RNC-configured frame offset
and code offset after roundup by 256 chips (the minimum time resolution of the NodeB is 256
chips), there is an error of ±128 chips between the actual transmission time and the RNC-
configured time. Plus errors in the UE movement speed and clock drift, there will be an error of
±(128+20) chips at the UE side. That is, when the Rx-Tx time difference is within the range of
1024±148 chips, the design of UE and NodeB should be able to satisfy the 1-slot power control
requirement; when it is out of this range, the system will be unable to guarantee the 1-slot power
control requirement, resulting in power control performance deterioration.

The UE Rx-Tx time difference is measured once every 10 frames. When the Rx-Tx time
difference is smaller than 876 (1024–148) chips, the UE-end processing time will be reduced,
and, as result, it will be likely that the downlink 1-slot power control cannot be guaranteed; when
the Rx-Tx time difference is greater than 1172 (1024+148) chips, the NodeB-end processing will
be reduced, and it will be likely that the uplink 1-slot power control cannot be guaranteed.

There are two UE internal measurement events for the measurement of the protocol-
provided synchronization maintenance information: event 6F and event 6G, as described
previously.

Algorithm description:

a) After the UE enters the CELL_DCH state, the algorithm enables the UE to report event
6F and event 6G through measurement control.

b) The thresholds, delays and hysteresis values of events 6F and 6G are used as algorithm
parameters, which can be adjusted through background configuration.

c) Once event 6F or event 6G occurs on a radio link, the network side will release this radio
link.

D) The cell with its link released may retrigger other events and then new RL could be
added to the active set.

2.2.8Direct Retry Algorithm

When the UE requests to leave the IDLE mode and enter the CONNECTION mode, if the
admission fails, another best cell will be selected for an access attempt based on the RACH
measurement report previously reported by the UE. Such an access attempt is called direct retry.

The direct retry algorithm needs the following parameters:

1) DRMaxNumber: the maximum direct retry times for each direct retry candidate cell



2) DRDCSThreshold: a basic threshold for entering the candidate set

3) MaxRelatingTime: the maximum time that the RACH measurement report can continue
to be used

4) LinearFactor: the linear factor for the relative threshold and time interval during candidate
set screening

5) MinSignalRequired: basic access threshold.

Algorithm description:

(1) The direct retry algorithm is effective only when the UE initiates RRC setup request.

(2) The direct retry algorithm buffers the cell measurement value in the RACH
measurement report of the UE, deletes the originally saved cell measurement information after
the RNC receives a new RACH measurement report, buffers the cells of which the measurement
signal CPICH Ec/No is greater than MinSignalRequierd (basic access threshold), and records
the reporting time.

(3) When the UE initiates an RRC setup requests, if the connection setup fails, the RNC will
choose a new cell with the best quality for a further access attempt based on the cell
measurement information in the RACH measurement report carried in the RRC CONNECTION
REQUEST message, until all the available cells (candidate cells) fail and the number of attempts
reaches the maximum retry times.

(4) Candidate cells are picked up as follows:

1) Read the current system time, calculate the buffering time of the cell measurement value,
and discards the cells of which the buffering time is bigger than MaxRelatingTime

2) Based on the measurement value in the buffered RACH report and the LinearFactor,
convert the estimated value of the current cell signal quality: cell measurement value (CPICH Ec/
No) – buffer time (s) × LinearFactor (dB/s)

3) Put the cells of which the estimated quality value is greater than DRDCSThreshold into
the candidate set of the direct retry algorithm.

(5) Retry with the cell having the best estimated quality from the candidate set cells. If retry
fails, continue to retry, until the number of attempts reaches the maximum retry times
(DRMaxNumber).

2.2.9Principle for Generating Adjacent Cell List

There are two adjacent cell list control methods:

1. Adjacent cell list control method based on the best cell



When the adjacent cell list is controlled based on the best cell, the basic policy is as follows:

(1) If there only one cell, the adjacent cell list will be controlled based on this cell;

(2) If a cell is added by event 1D, after it is successfully added, the adjacent cell list will be
controlled based on this cell;

(3) If a cell is added by an event other than event 1D, the adjacent cell list will not be
changed;

(4) If the best cell has not been removed, the adjacent cell list will not be changed;

(5) If the best cell has been removed, a new best cell will be selected based on the
information obtained during the removal action, and the adjacent cell list will be modified after
successful removal of the best cell;

(6) If event 1D occurs on a cell in the active set, the adjacent cell list will be modified.

(7) This method is relative simple, but is may bring the problem of inaccurate control for
UEs under the macro diversity.

2. Control method based on all the cells in the active set

A control method that can take the adjacent cells of all the cells in the active set is a good
policy. The adjacent cell list is generated by means of the following method:

Step 1: Add active set cells;

Step 2: Add the common adjacent cells of the cells of all the active sets (3 active sets) into
the adjacent cell list. If there are more than 32 adjacent cells after this action, remove randomly
cells added in this step;

Step 3: Add the common adjacent cells of every two active set cells into the adjacent cell
list. If there are more than 32 adjacent cells after this action, remove randomly cells added in this
step;

Step 4: Consider adding the common adjacent cells of each active set cell into the adjacent
cell list, starting from the adjacent cells of the best cell. If there are more than 32 adjacent cells
after this action, remove cells by starting from the worst cell.

Note: The RNC V1.2 version supports the adjacent cell list control method based on the
best cell.

3 Handover Parameter Setting



3.1Description

The MML client utility can be used for handover parameter setting. This utility provide
convenient command navigation and function description, detailed usage and parameter
descriptions of various commands.

Figure 10 MML Client

According to the functioning scope, handover algorithm parameter configuration commands
are divided into categories: RNC-oriented global parameter configuration and cell-oriented
parameter configuration.

Handover common parameter configuration is RNC-oriented global parameter setting.

Both RNC-oriented setting commands and cell-oriented setting commands are available for
the configuration of intra-frequency handover measurement algorithm parameters, inter-
frequency handover measurement algorithm parameters and inter-system handover
measurement algorithm parameters. Generally, the adjustments of these parameters during
network optimization are all cell-oriented settings, while RNC-oriented global parameter
configuration commands facilitate modification of whole-network handover parameters. For one
same parameter, the cell-oriented command has higher priority.



3.2Handover Common Parameters

3.2.1Maximum Number of Cells in Active Set
Definition
MaxCellInActiveSet, maximum number of cells in the active set
Scope
Per RNC
Range and unit
Integer(1..3)
Working range
Integer(1..3)
Recommended value
3
Balance in setting
Modification of value is not recommended.
Modification/query
To configure this RNC-oriented global handover parameter, use the command set
hocomm; to view the current configuration of the parameter, use the command lst
hocomm.

3.2.2Penalty Time
Definition
PenaltyTime, cell penalty time parameter, as described in Section 2.2.6.
Scope
Per RNC
Range and unit
Integer(1..255), s.
Working range
Integer(1..60)
Recommended value
30, namely the penalty time is 30 seconds
Balance in setting
The setting of this parameter is related to traffic statistics. According to the general traffic
statistics result, the average duration of a call is 60s, so the actual value range of this
parameter is 1 to 60 seconds. If this value is too small, the resources will not be timely
released, and therefore the penalty is meaningless; if this value is too big, radio links will
fail to be timely added, and this is bad for link QoS improvement.
Modification/query



hocomm.

3.2.3Event 6F Trigger Threshold
Definition
RxTxtoTrig6F, the trigger threshold of event 6F. Namely, if the time interval between the
UE’s downlink receiving and the corresponding uplink transmission is greater than this
absolute threshold, event 6F will be triggered.
Scope
Per RNC
Range and unit
Integer(768..1280), chip.
Working range
Integer(1024..1280)chip
Recommended value
1172
Balance in setting
The value of this parameter should not be too close to 1024; otherwise radio links will be
removed too early. It is recommended that this parameter be adjusted within the range of
1172±3 chips. To guarantee the 1-slot power control, decrease the value of this
parameter; otherwise, it could be increased.
Modification/query
hocomm.

3.2.4Event 6G Trigger Threshold
Definition
RxTxtoTrig6G, absolute threshold for triggering event 6G.
Scope
Per RNC
Range and unit
Integer(768..1280), chip.
Working range
Integer(768..1024)chip
Recommended value
876
Balance in setting



The value of this parameter should not be too close to 1024; otherwise radio links will be
removed too early. It is recommended that this parameter be adjusted within the range of
876±3 chips. To guarantee the 1-slot power control, increase the value of this parameter;
otherwise, it could be increased.
Modification/query
hocomm.

3.2.5Time-to-Trigger Parameters for Events 6F and 6G
Definition
Time-to-trigger parameters for event 6F and event 6G, including TrigTime6F and
TrigTime6G.
Scope
Per RNC
Range and unit
Enum(D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240, D320, D640,
D1280, D2560, D5000), ms.
Working range
Enum(0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640, 1280, 2560, 5000)ms
Recommended value
D240.
Balance in setting
UE Rx-Tx time difference type1 is measured once per 100ms, with measurement accuracy
being 1.5 chips. To avoid wrong judgment caused by measurement errors of the UE, a
delay can be set in the event trigger time, so that the UE can perform measurement at
least twice for judgment. The time delay on internal processing shall also be taken into
consideration. We recommend that this parameter be set at 240ms.
Modification/query
hocomm.

3.2.6BE Service Handover Rate Decision Threshold
Definition
BEBitRateThd. When the PS BE service rate exceeds this threshold, intra-frequency hard
handover will be implemented; when it is lower than this threshold, soft handover will be
implemented.
Scope



Per RNC
Range and unit
Enum (D8, D32, D64, D128, D144, D256, D384), corresponding to (8k, 32k, 64k, 128k,
144k, 256k, 384k) bps.
Working range
Enum(D8,D32,D64,D128,D144,D256,D384)
Recommended value
D64.
Balance in setting
It is the rate decision threshold deciding whether soft handover is to be implemented for
the BE service. When the maximum rate of the BE service transmission channel is smaller
than this threshold, the system will perform soft handover for the service user so as to
ensure the QoS for the user; when the maximum rate of the BE service transmission
channel exceeds this threshold, the system will implement intra-frequency hard handover
for the service user so as to prevent excessive influence on the system capacity caused
by soft handover.
Modification/query
hocomm.

3.2.7Soft Handover Method Select Switch
Definition
SHOMechod, used to select the loose-mode algorithm or the relative threshold algorithm
for soft handover decision.
Scope
Per RNC
Range and unit
Enum(SHO_METHOD1, SHO_METHOD2), soft handover algorithm 1, soft handover
algorithm 2
Working range
Enum(SHO_METHOD1, SHOMETHOD2)
Recommended value
Soft handover algorithm 2.
Balance in setting
Algorithm 1 is the loose-mode algorithm that adds a cell into the active set no matter the
cell triggers event 1A or event 1E, and removes a cell only after it triggers both event 1B
and event 1F simultaneously. Algorithm 2 is the relative threshold algorithm, which does



not involve events 1E and 1F. It adds a cell into the active set as soon as it triggers event
1A, and removes a cell from the active set as soon as it triggers event 1B.
Modification/query
hocomm.

3.2.8Handover Algorithm Switches
Definition
This parameter defines the switches of various algorithms related to connection-oriented
handover. The specific algorithm parameters can function only after the corresponding
algorithm switches being enabled.
Scope
Per RNC
Range and unit
32 bits, 0~4294967295; each bit can be set at 0 or 1 to control a handover algorithm.
Currently there are the 17 handover algorithm switches, arranged as follows from the
lowest bit to the highest:
Soft handover
Compressed mode maintenance algorithm at soft handover synchronization
Intra-frequency hard handover
Inter-frequency hard handover
3G-2G inter-system hard handover
2G-3G inter-system hard handover
Compressed mode
Uplink compressed mode
6G & 6F measurement
Cell penalty
Location
RTT enhanced location
Relocation
Relocation based on time delay optimization
Relocation based on Iur transmission resource optimization
CS UE relocation based on Iur transmission resource optimization
Direct retry
Working range
Integer(0~32767)
Recommended value
1159, namely 00000010010000111:



Soft handover — On (1)
Compressed mode maintenance algorithm at soft handover synchronization — On (1)
Intra-frequency hard handover — On (1)
Inter-frequency hard handover — Off (0)
3G-2G inter-system hard handover — Off (0)
2G-3G inter-system hard handover— Off (0)
Compressed mode — Off (0)
Uplink compressed mode — On (1)
6G & 6Fmeasurement — Off (0)
Cell penalty — Off (0)
Location — On (1)
RTT enhanced location — Off (0)
Relocation — Off (0)
Relocation based on time delay optimization — Off (0)
Relocation based on Iur transmission resource optimization — Off (0)
CS UE relocation based on Iur transmission resource optimization — Off (0)
Direct retry — Off (0)
Balance in setting
Corresponding configuration should be carried out based on the implementation of each
version of algorithm.

1) Test compressed mode: compressed mode switch should be enabled.

2) Test inter-frequency hard handover: inter-frequency hard handover + compressed mode
switch should be enabled.

3) Test inter-system hard handover : inter-system handover enabled + compressed mode
switch should be enabled.

4) Test relocation: relocation enable switch — a main switch. When the main switch is off,
the following three will not function
Relocation based on time delay optimization enable switch
Relocation based on Iur transmission resource optimization enable switch
CS UE relocation based on Iur transmission resource optimization enable switch
Modification/query
For RNC-oriented settings, use the command set/lst corrmalgoswitch.

3.3Intra-Frequency Handover Measurement Algorithm Parameters

3.3.1Soft Handover Relative Thresholds
Definition



These parameters define the difference between the quality of a cell (currently it is
evaluated with PCPICH Ec/No) and the overall quality of the active set (if w=0, then it is
the quality of the best cell). The relative threshold parameters for soft handover include
IntraRelThdFor1A (relative threshold for event 1A) and IntraRelThdFor1B (relative
threshold for event 1B).
Scope
Per RNC/CELL
Range and unit
Integer(0~29), corresponding to 0 to 14.5dB; configuration step: 1 (0.5dB).
Working range
Integer(0~16)
Recommended value
10, namely, 5dB.
Balance in setting
Settings of these parameters determine the size of the soft handover area and the soft
handover subscriber proportion. In a CDMA system, it is required that the UE proportion in
soft handover should be 30% to 40% so as to ensure smooth handover. Based on the
simulation result, when the relative thresholds are set at 5dB, the proportion of UEs in the
soft handover state (number of active set cells ≥ 2) is around 35%. It is recommended that
this value be slightly bigger in the early stage of deployment (5 to 7dB). To save system
resources, this figure can be gradually decreased with the growth of the number of
subscribers, but it must be bigger than 3dB. The default configuration is 5dB. In addition,
in special applications, different relative threshold values can be set for event 1A and
event 1B to reduce the ping-pong effect and change the soft handover proportion in some
special applications. For example, if the adjustment of the hysteresis values for events 1A
and 1B is insufficient for good control of the ping-pong effect, the relative threshold for
event 1B can be set larger than that for event A to reduce the ping-pong effect. However,
the relative thresholds for events 1A and 1B should generally be kept consistent; instead,
the time-to-trigger setting, L3 filter coefficient and hysteresis value should used to reduce
the ping-pong effect.
Modification/query
To implement cell-oriented settings, use the commands add/mod/rmv/lst
cellintrafreqho. Otherwise, use the RNC-oriented global settings configured with the
command set intrafreqho as the configuration for the concerned cell.

3.3.2Soft Handover Absolute Thresholds
Definition



These parameters correspond to the signal strength that satisfies the basic QoS
assurance. The soft handover absolute threshold parameters include IntraAblThdFor1E
(absolute threshold for event 1E) and IntraAblThdFor1F (absolute threshold for event 1F).
Scope
Per RNC/CELL
Range and unit
Integer(-20..-10), dB.
Working range
Integer(-20..-10)dB
Recommended value
-18.
Balance in setting
This value is the absolute threshold value used in the measurement reports of events 1E
and 1F in the soft handover algorithm, corresponding to the signal strength that satisfies
the basic QoS assurance. This value affects the trigger of events 1E and 1F. Because an
absolute threshold is only a necessary condition, but not a sufficient one, for access
judgment, this value should be relative loose. With value settings in IS-95 and the lower
threshold of -20dB, -18dB is deemed to be a reasonable value.
Modification/query
To implement cell-oriented settings, use the commands add/mod/rmv/lst cellintrafreqho.
Otherwise, use the RNC-oriented global settings configured with the command set
intrafreqho as the configuration for the concerned cell.

3.3.3Intra-Frequency Measurement Filter Coefficient (FilterCoef)
Definition
The measurement filtering coefficient used in L3 filtering of intra-frequency measurement
report
Scope
Per RNC/CELL
Range and unit
Enum(D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D11, D13, D15, D17, D19), corresponding
to (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 15, 17, 19)
Working range
Enum(D0, D1, D2, D3, D4, D5, D6, D7, D8)
Recommended value
D5, namely 5
Balance in setting
The following formula is used for the calculation of measurement value filtering:



Fn = (1 − a ) ⋅ Fn −1 + a ⋅ M n
Where,
Fn: the updated measurement result after filtering processing.
Fn-1: the old measurement result of the previous moment after filtering processing.
Mn: The latest measurement value received from the physical layer.
a = (1/2)(k/2), where, k is from IE "Filter coefficient", namely “FilterCoef” here. When k=0
and a=1, L3 filtering is not implemented.
According to R2-000809, we recommend that the commonly used value of the filter
coefficient be in the range of {0,1,2,3,4,5,6}. The bigger the filter coefficient is, the stronger
the burr filtering capability will be, but the weaker the signal tracking capability will be.
Therefore, a balance must be made. Calculated based on the typical handover area size
[3], the distance between two NodeBs is 1000m, while calculated based on the 40%soft
handover ratio of the entire system, the typical handover distance between two cells is
about 150m. A mobile station that is moving at the speed of 20km/h goes across the
handover area in averagely 20 to 30 seconds, while it takes only 5 to 6 seconds for a
mobile station that is moving at the speed of 100km/h to go across the handover area.
When such factors as hysteresis and trigger delay in event judgment are taken into
account, the tacking time needs to be further reduced. Based on the analysis above,
FilterCoef should be configured as follows: 5 as the default setting for intra-frequency filter
coefficient, and this parameter can be adjusted according to the actual situation. In
addition, for different cell coverage types, typical values are recommended as follows:
a, if the cell covers urban area, the intra-frequency filter coefficient can be 7;
b, if the cell covers suburbs, the intra-frequency filter coefficient can be 6;
c, if the cell covers rural area, the intra-frequency filter coefficient can be 3.
Table 1 Filter Coefficient vs. Intra-Frequency Tracking Time
Filter 0 1 2 3 4 5 6 7 8 9 11

coefficient
Iteration 1 2 3 5 7 10 15 21 30 42 85
times
The table above lists the iteration times required when different filter coefficients
are used to obtain 85% of the final output value. According to 25.133, in the
CELL_DCH state, L1 reports the intra-frequency measurement result to L3 at a
cycle of 200ms. When the iteration times are substituted with Intra-frequency
tracking time, the table above will become:
0 1 2 3 4 5 6 7 8 9 11
Filter
coefficient
Intra- 0.2 0.4 0.6 1 1.4 2 3 4.2 6 8.4 17
frequency
tracking
time (s)



Modification/query
Otherwise, use the RNC-oriented global settings configured with the command set/lst

3.3.4Hysteresis Related to Soft Handover
Definition
Hysteresis for event triggering, including Hystfor1A, Hystfor1B, Hystfor1C, Hystfor1D,
Hystfor1E and Hystfor1F
Scope
Per RNC/CELL
Range and unit
Integer(0..15) , corresponding to 0..7.5dB; configuration step 1(0.5dB)
Working range
table 1Recommended Soft Handover Hysteresis Settings for Different Movement Speeds
Speed (km/h) Range Recommended Value
5 6~10(3~5dB) 10(5dB)
50 4~10(2~5dB) 6(3dB)
120 2~6(1~3dB) 2(1dB)
Typical configuration 4~10(2~5dB) 6(3dB)

Recommended value
6(3dB) for events 1A and 1E, and 8(4dB) for events
Balance in setting
For UEs entering the soft handover area, increase of the hysteresis value means decrease
of the soft handover range, while for UEs leaving the soft handover area, it means
increase of the soft handover range. If the number of UEs entering the handover area is
the same as the number of UEs leaving the handover area, there will be no influence on
the actual soft handover proportion. The bigger the hysteresis value is, the stronger the
signal fluctuation resistance capability will be, and thus the better the ping-pong effect will
be suppressed, but the slower the handover algorithm can react on signal changes.
Therefore, in the setting of this parameter, not only the radio environment (slow fading
characteristic) but also the actual handover distance and the UE movement speed should
be taken into due consideration. The setting of this parameter can be adjusted within the
range of 2 to 5dB. As events that add cells to the active set, 1A and 1E are critical events.
In order to ensure timely handover, the hysteresis value for event 1A can be smaller, but
not be too smaller, than those for 1B, 1F, 1C and 1D; otherwise, the soft handover
proportion will be affected.



In addition, In addition, hysteresis adjustment should generally be considered together
with the filter coefficient and time-to-trigger settings.
Modification/query

3.3.5Time-to-Trigger Parameters Related to Soft Handover
Definition
Time-to-trigger parameters, including TrigTime1A, TrigTime1B, TrigTime1C, TrigTime1D,
TrigTime1E and TrigTime1F, corresponding to the six events for intra-frequency
measurement respectively.
Scope
Per RNC/CELL
Range and unit
Enum(D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240, D320, D640,
D1280, D2560, D5000), corresponding to (0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240,
320, 640, 1280, 2560, 5000)ms
Working range
Enum(D0, D200, D240, D640, D1280, D2560, D5000)
Recommended value
table 2Recommended Time-to-Trigger Settings for Different Movement Speeds
Speed (km/h) Range (ms) Recommended value (ms)
5 640, 1280 1280
50 240, 640 640
120 240, 640 640
Typical configuration 640, 1280 640

Balance in setting
Simulation shows that the setting of the hysteresis value can effectively reduce the
average handover times and mis-handover times, and thus can prevent the occurrence of
unwanted handover. The bigger the hysteresis value is, the less the average handover
timers will be. However, the increase of the hysteresis value will bring more risks of call
drop. It is stipulated in TS 25.133V3.6.0 that the physical layer of intra-frequency
measurement updates the measurement result every 200ms. Therefore, a time-to-trigger
value below 200ms does not make any practical sense, and it should be as close as
possible to an integral multiple of 200ms. In addition, simulation also shows that mobile
stations moving at different speeds respond differently to the time-to-trigger value. The call
drop rate is more sensitive to the time-to-trigger value when the mobile station is in high-
speed movement, while it is less sensitive when the mobile station is in low-speed



movement, and ping-pong handover and mis-handover are suppressed to a certain extent.
Therefore, for cells where there are more high-speed moving mobile stations, this value
can be relatively small, while for cells where there are more low-speed moving mobile
stations, this value can be relatively big. Different types of events have different
requirements on the time-to-trigger setting: events that add cells to the active set (event
1A and event 1E) generally require a small time-to-trigger setting, while events that
replace cells in the active set (event 1C and event 1D) generally require low ping-pong
handover and mis-handover and do have produce remarkable influence on the call drop
rate. For the latter type of events, the time-to-trigger setting can be properly big. For
events that remove cells from the active set (event 1Band event 1F), the time-to-trigger
value is set mainly to reduce ping-pong handover; the initial setting can be the same as
that for event 1A and event 1E, and can be properly adjusted based on the actual network
statistics result.
Modification/query

3.3.6WEIGHT
Definition
Weighted factor (see formulas on Section 2.1.1)
Scope
Per RNC/CELL
Range and unit
Integer(0..20), corresponding to 0..2; step: 0.1
Working range
Integer(0..10)
Recommended value
10, namely 1
Balance in setting
This parameter is used to determine the soft handover relative threshold based on the
measurement value of each cell in the active set. The bigger this parameter is, the higher
the relative threshold obtained under the same condition will be. When W=0, the
determination of soft handover relative threshold is related to only the best cell in the
active set.
Modification/query




3.3.7Detected Set Statistics Switch
Definition
DetectStatSwitch, used to control whether the UE measurement report contains the
information of cells in the detected set, so as to provide statistics data for future network
optimization.
Scope
Per RNC/CELL
Range and unit
Enum(ON, OFF)
Working range
Enum(ON,OFF)
Recommended value
OFF
Balance in setting
In the beginning of network operation, when you are not absolutely sure about the adjacent
cell configuration, this switch can be set to ON so that missed adjacent cells can be
detected and thus handover can be smoothly implemented. After network optimization, this
switch can be set to OFF.

Modification/query

3.4Inter-Frequency Handover Algorithm Parameters

3.4.1Inter-Frequency Measurement Filter Coefficient (FilterCoef)
Definition
The measurement smoothening coefficient used in L3 filtering of inter-frequency
measurement report
Scope
Per RNC/CELL
Range and unit



Enum(D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D11, D13, D15, D17, D19), corresponding
to (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 15, 17, 19)
Working range
Enum(D0, D1, D2, D3, D4, D5, D6, D7, D8)
Recommended value
D5, namely 5
Balance in setting
The following formula is used for the calculation of measurement value filtering:
Fn = (1 − a ) ⋅ Fn −1 + a ⋅ M n
Where,
Fn: the updated measurement result after filtering processing.
Fn-1: the old measurement result of the previous moment after filtering processing.
Mn: The latest measurement value received from the physical layer.
a = (1/2)(k/2), where, k is from IE "Filter coefficient", namely “FilterCoef” here. When k=0
and a=1, L3 filtering is not implemented. According to R2-000809, we recommend that the
commonly used value of the filter coefficient be in the range of {0,1,2,3,4,5,6}. The bigger
the filter coefficient is, the stronger the burr filtering capability will be, but the weaker the
signal tracking capability will be. Therefore, a balance must be made. For different cell
coverage types, typical values are recommended as follows:
a, if the cell covers urban area, the inter-frequency filter coefficient can be 7;
b, if the cell covers suburbs, the inter-frequency filter coefficient can be 6;
c, if the cell covers rural area, the inter-frequency filter coefficient can be 3.
Modification/query
To implement cell-oriented settings, use the commands add/mod/rmv/lst
cellinterfreqho. Otherwise, use the RNC-oriented global settings configured with the
command set interfreqho as the configuration for the concerned cell.

3.4.2Cell Location Property
Definition
CellProperty (cell location property), indicating whether the cell is located at the verge or
center of the carrier coverage.
Scope
Per CELL
Range and unit
Enum(CARRIER_FREQUENCY_VERGE_CELL,
CARRIER_FREQUENCY_CENTER_CELL), (cell located at carrier coverage verge / cell
located at carrier coverage center)
Working range


Wcdma Rno Handover Algorithm Analysis And Parameter Configurtaion Guidance 20050316 A 1.0

Wcdma Rno Handover Algorithm Analysis And Parameter Configurtaion Guidance 20050316 A 1.0

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