W(Level3)-WCDMA RNO Handover in WCDMA-20041217-A-1[1].0

8/2/2019 W(Level3)-WCDMA RNO Handover in WCDMA-20041217-A-1[1].0

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Wireless Curriculum Development Section

ISSUE

OWJ104104 WCDMA

Handover analysis

1.0


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2Confidential Information of Huawei.No Spreading without Permission. Security Level: Internal

Objectives

How to configure the handover

parameters

How to do at handover optimization

Upon completion of this course,you will be able to:


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Course Contents

Chapter 1Introduction

Chapter 2 handover principle

Chapter 3 SHO Optimization

Chapter4 Inter-RAT Optimization


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Introduction

In WCDMA system, there are soft handover, Intra

frequent hard handover, Inter frequent hard

handover, Inter system handover. Handover is the

most important part of mobile manage. It plays

very important role in RNO of WCDMA system .


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Chapter 2 Handover principle

2.1 Intra-frequency measurement

2.2 Hard handover measurement

2.3 Handover algorithms review

2.4 Handover parameters review


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Intra-frequency measurement

Event 1A:A primary pilot channel enters the reporting range

When the measurement values satisfy the following formulas, the UE deems that a primary pilot

channel has entered the reporting range,the trig condition for Ec/Io:

MNewis the measurement result of the cell that has entered the reporting range

CIOnew is the cell individual offset which is configured for neighbor cells of

servicing cell

Miis the measurement result of the cells in the active set

NA is the number of cells in the current active set

MBestis the measurement result of the best cell in the current active set

Wis 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

H1ais the hysteresis value of event 1A

)2/(log.10).1(.10.log10 11

abest

N

i

inewnew HRMWMLogWCIOMA


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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 .trig condition for Ec/Io:

MOldis the measurement result of the cell that has left the reporting range

CIOold is the cell individual offset which is configured for neighbor cells of

servicing cell

Miis the measurement result of the cell in the active set

NA is the number of cells in the current active set

MBestis the measurement result of the best cell in the current active set

Wis the weighted factor

Ris the reporting range

H1bis the hysteresis value of event 1B

)2/(log.10).1(.10.log10 11

bbest

N

i

ioldold HRMWMLogWCIOMA


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Event 1C: The primary pilot channel in a non active set is better than the

primary pilot channel in an active set

When the following formulas are satisfied, a non-active set cell replaces an old

active set cell and becomes an active set cell.trig condition for Ec/Io:

MNewis the measurement result Ec/Io of the cell not included in the active set.

CIONew is the individual cell offset for the cell becoming better than the cell in the

active set if an individual cell offset is stored for that cell. Otherwise it is equal to 0.

MInASis the measurement result Ec/Io of the cell in the active set with the lowest

measurement result.

CIOInAS is the individual cell offset for the cell in the active set that is becoming

worse than the new cell

H1cis the hysteresis parameter for the event 1C, which is Hystfor1C.

2/.10.log10 1cInASInASnewnew HCIOLogMWInASCIOM


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Event 1D: The best cell changes

When the following formulas are satisfied, the best cell will be

changed .trig condition for Ec/Io:

MNotBestis the measurement result Ec/Io of a cell not stored

in "best cell".

MBest is the measurement result Ec/Io of the cell stored in

"best cell".

H1d is the hysteresis parameter for the event 1D, which is

Hystfor1D

2/log.10log10 1DbestNotBest HMM


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Hard handover measurement

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.

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

,2/10)1(10101

HLogMWMLogWLogMQ jBestj

N

i

jijjcarrierjcarrier

jA


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Hard handover 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 .

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

,2/10)1(10101

HLogMWMLogWLogMQ jBestj

N

i

jijjcarrierjcarrier

jA


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Handover Algorithms review

Soft Handover Algorithms review

Inter-RAT Handover Algorithms review


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Handover algorithms review: SHO

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. 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.


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Confidential Information of Huawei.No Spreading without Permission. Security Level: Internal

Handover algorithms review: SHO

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.

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 thenon-best cell will be removed before this link is added) and

marked as the best cell, with measurement control updated.


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Handover algorithms review: Inter-RAT

Inter-system handover is enabled only in cells located at theverge of WCDMA FDD system coverage.

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.

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.


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Handover algorithms review: Inter-RAT

Periodic measurement reports are used for inter-system

handover, and the RNC decides whether to implement hardhandover according to the measurement reports.

Handover Evaluation, while the compressed mode is started

and this following formulas is satisfied, Inter-system handover

will be implemented. .

Mother_RAT + CIO Tother_RAT + H/2

Mother_RAT is the estimated quality value RSSI of inter-system frequency

Tother_RAT is the GSM RAT measurement init_threshold, the minimum

signal Rxlev requirement for GSM cell as a handover target cell.

CIO is Cell individual offset , the measurement signal Rxlev offset for GSM

cell

H is the hysteresis for GSM RSSI threshold.


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Handover parameters review-SHO

Report range (SHO relative threshold )

Intra-frequency measurement filter coefficient

Time to Trigger

Hysteresis

CIO (cell individual offset)


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Report range (SHO relative threshold )

The relative threshold parameters for soft handover include

IntraRelThdFor1A (relative threshold for event 1A) and

IntraRelThdFor1B (relative threshold for event 1B) .

The parameters determine the size of the soft handover area

and the soft handover subscriber proportion. If report range is

too larger, monitor cell adds to active set cell very easily, soft

handover area is too larger and the forward capacity will be

waste serious; if the 1A and 1B report range is too small,

monitor cell is difficult to join to active cell and SHO cant

implement smoothly, and handover success rate may be low


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Intra-frequency measurement filter coefficient The filter is configured at Layer 3 intra-frequency

measurement report. This parameter used to smooth the

influence of shadow fading and some fast fading burrs.

The bigger the filter coefficient is, the stronger the smoothing

capability of the burr will be, but the lower the signal tracing

capacity will be. If if this parameter is too small, unnecessary

soft handover and ping pong handover will influence the

system; if the filter is too bigger, soft handover cant

implement in time and the call will always dropped in

handover area .


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Time to Trigger The effect of the time-to-trigger is that the report is triggered

only after the conditions for the event have existed for the

specified time-to-trigger

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


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Hysteresis parameter related to SHO

To limit the amount of event-triggered reports.

The bigger the hysteresis is, the stronger the signal fluctuation

resistance capability will be, and the better the ping pong

effect will be suppressed; however, the response speed of the

handover algorithm on signal changes will be decreased.

Therefore, the radio environment (slow fading characteristics),

the actual handover distance and the user moving speed

should be fully considered for the setting of this parameter.


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CIO (Cell Individual Offset )

This offset mechanism provides the network with an efficient

tool to change the reporting of an individual primary CPICH .

The bigger this parameter is, the more easily soft handover

will occur, and the more UEs will be in the soft handover state,

but the more forward resources will be occupied; the smaller

this parameter is, the more difficultly soft handover will occur,

which will be likely to affect the receiving quality .


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Handover parameters review-HHO

compressed mode enable /disable threshold(2D/2F

Event threshold )

GSM RSSI threshold

filter coefficient

Time to Trigger

HysteresisCIO (cell individual offset)


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2D/2F Event threshold

UE will start compressed mode and measure GSM signal as

a handover target cell when the value of RSCP is below the

setting. UE will stop compressed mode l when the value of

WCDMA cell RSCP is higher than the setting.

if the compressed mode is expected to start as early as

possible, set the 2D event threshold to a relatively big value;

otherwise, set it to a relatively small value. To control the ping

pong effect of the compressed mode start/stop, increase

appropriately the difference between the thresholds for 2D

event and 2F .


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filter coefficient

The hysteresis for GSM RSSI threshold and the setting of

which can reduce the probability of mis-decision caused by

signal jitter .


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Time to Trigger If the inter-RAT quality always satisfies the inter-RAT

handover decision condition within the time specified by this

parameter, the network will start the inter-RAT handover

process

In high-speed cells, as mobile stations usually move fast, they

pass through the handover area very quickly. In addition, as

the shadow fading variance in a high-speed cell is small and

signal jitter after filtered by mobile stations is relatively small,

this parameter can be set to 2000ms or lower for high-speed

cells.


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Hysteresis

The hysteresis for GSM RSSI threshold and the setting of

which can reduce the probability of mis-decision caused by

signal jitter.


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CIO

The measurement signal Rxlev offset for GSM cell .

The bigger this parameter is, the higher the handover priority

of the GSM cells will be .


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Course Contents






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Soft Handover Optimization

SHO Optimization Target

Drive Routes

Optimization Solution

Optimization Analysis approach


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SHO Optimization Target

In the early phase of the network, from KPI target, soft

handover success rate for event 1A&1B&1C should be larger

than 95%, and the call drop rate should be smaller than 5%.


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Drive Routes

In the early phase of the network, because KPI result dont

change in evidence prior and post optimization, GPS drive test

is very important .It is essential to use identical drive routes

prior and post any optimization changes in order to accurately

quantify the impact of such changes.


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Optimization Solution

Many handover problems can be resolved through adjusting

the soft handover parameters, such as:

1A & 1B report range

time to trigger

intra-frequceny measurement filter coefficient

CIO

hysteresis

Soft Handover Optimization: Optimization


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Analysis approach

Small handover areaThe active set quality decreases quickly but the good quality

monitor cell cant add to active set in time.

This issue may be RNP problem but sometime this cant be

resolved at RF optimization stage and also could be due to

soft handover configuration problem .

Enlarge 1A &1B&CIO report range to make the UE monitor

cell easily add to active set;Short 1A time to trig to make the measurement report in time,

also can optimize the intra-frequency measurement coefficient;


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CIO Handover optimization example

After setting 3dB CIO of 506 and 505 cell, we can see that the

drop calls between 505 and 506 decreased. (Left picture is

before optimization)



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Analysis approach

Ping-Pong handover

The active set cell change frequently between the same cells.

This issue may be RF problem, and also cell soft handover

configuration problem.

Cells with many Ping-Pong handover may be causing call

dropped and poorer cell capacity.

This can enlarge intra-frequency measurement coefficient and

time to trigger.


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Ping-Pong handover example

The ping-pong handover of 505 cell and 506 cell

can be seen.


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Course Contents






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Inter-RAT Optimization

Presently, the main purpose of inter-RAT handover is toextend the signal coverage range, so that the UEs at the

verge of WCDMA coverage can implement handover to the

GSM system without communication interruption.

The configuration GSM neighbor list of WCDMA cells is very

important and always make wrong. At the same time, the

parameters optimization is very important.

The optimization solution is parameters configuration such as:

2D & 2F Event threshold, GSM RSSI threshold, Inter-RAT

handover trigger time, intra-frequceny measurement filter

coefficient, CIO and Hysteresis.


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W(Level3)-WCDMA RNO Handover in WCDMA-20041217-A-1[1].0

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Transcript of W(Level3)-WCDMA RNO Handover in WCDMA-20041217-A-1[1].0