09-wcdma rno handover principal_20051214
TRANSCRIPT
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Huawei Confidential. All Rights Reserved
WCDMA Handover Principal and
Analysis1.0
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Internal Use 1
Why mobile systems need
handover?It is decided by the characters of
mobile system:
The mobility of UE
The mobile system is composed by
cells which the coverage ability is
limited.
Providing the continuous service in
mobile system is the basic element inQoS.
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Internal Use 2
Object
Upon completion this course, you will
be able to:
The basic definitions of Handover The algorithms of handover
decision
The handover flow
The parameters of handover
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Internal Use 3
Chapter 1 Introduction of Handover
Chapter 2 Measurement of Handover
Chapter 3 The Basic Handovers
Chapter 4 Blind Handover and
Direct Retry Algorithm
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Internal Use 4
The Purpose of Handover
Providing the continuous service in mobile system is the basic
element in QoS.
The load balance: sharing the resource
The hierarchy divided by speed and service: high efficiency of usingresource
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Internal Use 5
The Basic Concepts of Handover
Active Set Monitored Set Detected set Event reporting
Event reporting to Periodic reporting Periodic reporting Radio Link (RL)
Radio Link Set (RLS) Combination way:
maximum ratio combination selection combination
The soft handover gain
CPICH Soft handover, softer handover, hard handover Blind handover
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The Categories of Handover
According to the signaling characters:
Soft handover (softer handover)
Hard handover According to the properties of source cell and target cell
Intra-frequency handover
Inter-frequency handover
Inter-mode handover (FDD TDD) Inter-system handover (UMTS GSM/CDMA2000)
According to the purpose of handover
Based on Coverage
Based on Load (Optional)
Based on mobility of UE (Optional)
Based on Service (Optional)
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The Characters of Different Handovers
Item Soft Handover Hard Handover
The numbers of RL
in active set after
handover
Several One
Interruption duringhandover
No Yes
The frequencies of
cells
Only happened
in Intra-
frequency cells
Can be happened in
Intra-frequency cells or
Inter-frequency cells
Comparison between soft handover and hard handover:
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The Characters of Different Handovers
During softer handover, the uplink signaling are
combined in NodeB by maximum ratio combination, butduring soft handover they are combined in RNC by
selection combination.
Compare to later one, the maximum ration combination
can get more gain. So the performance of maximum
ration combination is better.
Since softer handover is completed in NodeB, it do not
consume transport resource of Iub.
Comparison between soft handover and softer handover:
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RNC
NodeB 2NodeB 1
Soft Handover
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RNC (WFMR)
NodeB
Softer Handover
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Hard Handover
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Three Steps of Handover
Decision
Execute
Measurement
Measurement Measurement control Measurement execution and
the result processing The measurement report Mainly accomplished by UE
Decision Based on Measurement The application and
distribution of resource Mainly accomplished by
RRM in RNC
Execution The process of signaling Support the failure drawback Measurement control refresh
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Questions
The differences among Soft handover,softer handover and hard handover
Typical application scenarios
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Summary
This chapter focus on the purpose of handovers and the
categories of handover in WCDMA.
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Chapter 1 Introduction of Handover
Chapter 2Measurement of Handover
Chapter 3 The Basic Handovers
Chapter 4 Blind Handover and
Direct Retry Algorithm
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Chapter 2 Measurement of Handover
Section 1 Measurement control and
measurement report
Section 2 The basic definitions of measurement
Section 3 Intra-frequency measurement event
Section 4 Inter-frequency and
inter-system measurement event
Section 5 UE internal measurement
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Measurement Control and Measurement
Report
Measurement Control
UE UTRAN
MEASUREMENT CONTROL
Measurement Control, normal case
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Measurement Control and Measurement
Report
Measurement report
UE UTRAN
MEASUREMENT REPORT
Measurement report, normal case
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Chapter 2 Measurement of Handover
Section 1 Measurement control and
measurement report
Section 2 The basic concepts of measurement
Section 3 Intra-frequency measurement event
Section 4 Inter-frequency and
inter-system measurement event
Section 5 UE Internal Measurement
Th B i C t f M t
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The Basic Concepts of Measurement
The measurement values of Handover
Intra-frequency and inter-frequency: CPICH RSCP CPICH
Ec/N0Path loss Inter-frequencyCPICH RSCPCPICH Ec/N0
Inter-systemGSM Carrier RSSI BSIC IdentificationBSIC
Reconfirmation
The reporting methods of measurement
Periodic reporting
Event reporting
The events of reporting
Intra-frequency events1A,1B,1C,1D,1F
Inter-frequency events2D,2F,2B,2C Inter-system events3A,3C
Others6G,6F
M t M d l
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Measurement Model
Layer 1filtering
Layer 3filtering Evaluation
of reporting
criteria
A DB C
C'
parameters parameters
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Internal Use 22
Reporting Criterion
Reporting Criterion
Decision formula: for example, 1A event :1.Path Loss
2.Other measurement
Relative threshold, Absolute threshold, Hysteresis, Time
to trigger
),2/(10)1(1010 11
aBest
N
i
iNew HRLogMWMLogWLogMA
),2/(10)1(1010 11
aBest
N
i
iNew HRLogMWMLogWLogMA
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Key Parameters
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Chapter 2 Measurement of Handover
Section 1 Measurement control and
measurement report
Section 2 The basic definitions of measurement
Section 3 Intra-frequency measurement events
Section 4 Inter-frequency and
inter-system measurement eventsSection 5 UE Internal Measurement
Intra frequency Measurement Events
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Intra-frequency Measurement Events
All intra-frequency measurement report events are identified with
1X :
1AA primary pilot channel enters the reporting range. Whenthe active set of UE is full, UE stops reporting 1A event;
1BA primary pilot channel leaves the reporting range;
1CThe primary pilot channel in a non active set is better than
the primary pilot channel in an active set;
1DThe best cell changes;
1EThe measurement value of a primary pilot channel exceeds
the absolute threshold
1F, The measurement value of a primary pilot channel is lower
than the absolute threshold
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Internal Use 26
Chapter 2 Measurement of Handover
Section 1 Measurement control and
measurement report
Section 2 The basic definitions of measurement
Section 3 Intra-frequency measurement events
Section 4 Inter-frequency and
inter-system measurement eventsSection 5 UE Internal Measurement
Inter frequency Measurement Events
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Internal Use 27
Inter-frequency Measurement Events
Inter-frequency measurement events are identified with 2X 2A: The best frequency changes;
2B: The estimated quality value of the used frequency is lower thana certain threshold, and that of the non-used frequency is higher
than a certain threshold;
2C: The estimated quality value of the non-used frequency is higher
than a certain threshold;
2DThe estimated quality value of the used frequency is lower than a
certain threshold
2E:The estimated quality value of the non-used frequency is lower
than a certain threshold
2F:The estimated quality value of the used frequency is higher thana certain threshold
Inter system Measurement Events
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Inter-system Measurement Events
Inter-system measurement events are identified with
3X 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;
3B: The estimated quality value of the other system is lower
than a certain threshold; 3C: The estimated quality value of the other system is higher
than a certain threshold;
3D: The best cell in the other system changes
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Internal Use 29
Chapter 2 Measurement of Handover
Section 1 Measurement control and
measurement report
Section 2 The basic definitions of measurement
Section 3 Intra-frequency measurement events
Section 4 Inter-frequency and
inter-system measurement eventsSection 5 UE Internal Measurement
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Internal Use 30
UE Internal Measurement
UE Internal measurement events are identified with 6X
6G: The time difference between downlink receiving anduplink transmission of the UE is shorter than an absolute
threshold;
6F: The time difference between downlink receiving and
uplink transmission of the UE is bigger than an absolute
threshold;
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Internal Use 31
Questions
How many events are there in intra-frequency measurement?What are they?
How many events are there in UE internal measurement?
How many events are there in inter-frequency measurement?
What are they?
S
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Summary
This chapter covers intra-frequency measurement, inter-
frequency measurement, inter-system measurement and UE
internal measurement from their definitions and applicationscenarios.
Summary
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Chapter 1 Introduction of Handover
Chapter 2 Measurement of Handover
Chapter 3The Basic HandoversChapter 4 Blind Handover and
Direct Retry Algorithm
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Chapter 3 The Basic Handovers
Section 1 Soft Handover
Section 2 Intra-frequency Hard Handover
Section 3 Inter-frequency Hard Handover
Section 4 Inter-system Hard Handover
Section 5 HSDPA Handover
Section 6 Compressed Mode
B i f I t d ti f S ft H d
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Brief Introduction of Soft Handover
Characters of Soft Handover During handover, UE has several RLs with different cells----
active set. The handover among different cells which are in same RLS can
be softer handover.
Soft handover:
Selection combination in uplink
Maximum combination in downlink
Softer handover Maximum combination in uplink and downlink
B i f I t d ti f S ft H d
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Brief Introduction of Soft Handover
Advantages Soft handover gain:
Multi-Cell gain: Multiple irrelated soft handover branches lowthe required margin for fading
Macro Diversity Combining gain: Gain for the linkdemodulation of the soft handover:
Load balance: Different cells receive the signals from UE inuplink, which can decrease the transmission power of UE. AndUE receive signal from different cells, which also can decreasethe transmission power of base station.
Decrease the possibility of call drop caused by ping-ponghandover.
Disadvantages More resource needed in downlink, especially for the code
resource of BE service. Usually, the gain of downlink power is negative. When the downlink power from different cells is not balanced, it
will bring side-effect.
Measurement of Soft Handover
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Measurement of Soft Handover
The measurement of soft handover/softer handover
Measurement valueCPICH RSCPCPICH Ec/NoPathloss
Process of MeasurementLayer 1 filter, Layer 2 filter Reporting way
Periodic reporting
Event reporting
Event type1A1B1C1D1F
UE measures the time difference between CFN and SFN
Reporting rules: trigger condition, Relative threshold,
Absolute threshold, Hysteresis, Time to trigger
Event reporting to periodic reporting
The Events of Soft Handover Measurement
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The Events of Soft Handover Measurement
Soft/softer handover measurement events
Intra-frequency events reporting:
1AA primary pilot channel enters the reporting range.When the active set of UE is full, UE stops reporting 1A event;
1BA primary pilot channel leaves the reporting range;
1CThe primary pilot channel in a non active set is better
than the primary pilot channel in an active set;
1DThe best cell changes;
1EThe measurement value of a primary pilot channel
exceeds the absolute threshold
1F, The measurement value of a primary pilot channel is
lower than the absolute threshold
The Decision Algorithm of Soft Handover
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The Decision Algorithm of Soft Handover
Soft/softer handover decision
1Aadd RL into active set
1BDelete RL from active set
1Creplace cell
1Dchange best cell
The Execution of Soft Handover
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The Execution of Soft Handover
Soft handover execution
The update principal of measurement control
Configure the neighbor cells and the parametersaccording to best cell
RLC mode
AM mode is used for measurement control
UM mode is used for measurement reporting
The compensation and restriction of soft handover
From event reporting to periodic reporting
Parametersthe time value for periodic reporting,
the number for reporting times
Soft Handover Flow (add RL)
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Soft Handover Flow (add RL)
The execution of soft handover (add RL)
Soft Handover Flow (del RL)
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Soft Handover Flow (del RL)
The execution of soft handover (del RL)
Key Parameters
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Key Parameters
Relative threshold Set 1A, 1B value separately 1A < 1Bwhich makes deleting RL is more difficult, and it can
avoid ping-pong handover Usually 1A: 3dB; 1B: 6dB
Time to trigger Each event can be set separately Usually, 1B>1Awhich makes deleting RL is more difficult, and
it can avoid ping-pong handover Usually, 1A: 320ms, 1B: 640ms
Layer 3 filter coefficient Only one value for all intra-frequency measurement Sensitive to the delay of event trigger and ping-pong handover Usually3
absolute threshold of soft handover
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Chapter 3 The Basic Handovers
Section 1 Soft Handover
Section 2Intra-frequency Hard Handover
Section 3 Inter-frequency Hard Handover
Section 4 Inter-system Hard Handover
Section 5 HSDPA Handover
Section 6 Compressed Mode
The Characters of Intra-frequency Hard Handover
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The Characters of Intra frequency Hard Handover
Characters UE only has one RL with one cell in the process of handover Disconnect UE with the original cell, then hand it over to target
cell The working frequency of source cell and target cell are same
Advantages Enhance the using efficiency of the OVSF code and hardware
resource Disadvantages
High call drop possibility because of the intra-frequencyinterference
Application scenarios
Without Iur interface between two RNCs or the Iur interface jam(only happened in inter-RNC handover)
The different strategies can be used for different conditions, such
as code resource condition, the QoS condition and so no.
The Measurement, Decision and Execution of
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The Measurement, Decision and Execution of
Intra-frequency Hard Handover
Measurement
Similar to soft handover
Decision
1D event
Execution
UE reports CFN-SFN information
Synchronization hard handover
Use the original DOFF value
Continuous CFN
UE does not report CFN-SFN information
The hard handover based on timingRe-configure DOFF
Calculate CFN according to DOFF
Intra-frequency Hard Handover Flow
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q y
Intra-frequency hard handover flow
UE1.RADIO LINK SETUP REQUEST
Target
NODEB
Source
NODEBSRNC
2. RADIO LINK SETUP RESPONSE
3.ALCAP establish
4. PHYSICAL CHANNEL RECONFIGURATION
5. RADIO LINK
FAILURE INDICATION
6. PHYSICAL CHANNEL RECONFIGURATION COMPLETE
7. RADIO LINK
DELETION REQUEST
8. RADIO LINK
DELETION RESPONSE
9.ALCAP release
Key Parameters
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Key Parameters
Handover decision threshold based on BE speed
UE should do soft handover when the speed of BE service isless than the threshold.
UE should do intra-frequency hard handover when the speed of
BE service is greater than the threshold.
The parameters about 1D event:
time to triggerhysteresis
The parameters should be set accord with the Qos
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Internal Use 49
Chapter 3 The Basic Handovers
Section 1 Soft Handover
Section 2 Intra-frequency Hard Handover
Section 3Inter-frequency Hard Handover
Section 4 Inter-system Hard Handover
Section 5 HSDPA Handover
Section 6 Compressed Mode
The Brief Introduction of Inter-frequency
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q y
Hard Handover Characters
The working frequency is different after handover
The compressed mode needed if the UE only has one receiver Usually, the timing re-initiation hard handover is used for hard
handover Advantages
Compare to intra-frequency hard handover, the success
possibility is higher The load balance among cells with different frequencies Can realize the reasonable configuration for hierarchy cells
Disadvantages Compressed mode results in extra radio resource occupied The timing re-initiation hard handover increase the time of
handover and the risk of call drop Application scenarios
Disconnected coverage Handover based on load Hierarchy cells
The Inter-frequency Hard Handover Measurement
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Values and Events
The Inter-frequency hard handover measurement values Measurement values:
CPICH RSCPCPICH Ec/N0 Different handover purpose for different measurement type:
In the edge of carrier coverage: CPICH RSCP
In the center of carrier coverage: CPICH Ec/No
The Measurement Values and Events of Inter-
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frequency Hard Handover
Measurement reporting Periodic reporting
Event reporting
2A: The best frequency changes;
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;
2C: The estimated quality value of the non-used frequency is
higher than a certain threshold;
2DThe estimated quality value of the used frequency is lower
than a certain threshold
2E:The estimated quality value of the non-used frequency islower than a certain threshold
2F:The estimated quality value of the used frequency is
higher than a certain threshold
Compressed Mode Initiation in Inter-frequency
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Internal Use 53
p q y
Hard Handover
Conditions for measurement initiated 2D eventcan be used to enable the compressed mode
to perform inter-frequency measurement. Enable inter-frequency measurement by moving speed
estimation algorithm Conditions for Measurement stopping
2F eventAfter the best cell is changed, the cell does not contain
inter-frequency neighbor cells. Inter-frequency measurement timer expired Because the moving speed of UE is changed, the inter-
frequency handover measurement is stopped by cell
hierarchy algorithm.
Cells Hierarchy Algorithm Based on UE
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Moving Speed
When UE is in one of the hierarchy cells, the moving speed
estimation algorithm is initiated Handover events in a while decides whether the speed of UE
satisfies the current cell hierarchy condition
UE is remained in the current cell if the speed is medium.
If the speed is very high, it will be handed over to higher
hierarchy cell. And if not, hand it over to lower hierarchy cell. UEsmoving speed decided the result.
If the hierarchy is configured by different frequencies, theinter-frequency blind handover or inter-frequencymeasurement handover can be initiated.
If the hierarchy is configured by one frequency, the intra-frequency handover can be initiated.
Inter-frequency Hard Handover Decision
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Algorithm
The inter-frequency hard handover decision
The coverage triggers the handover
2B event
the quality in the used frequency is lower than absolute
threshold, but the quality in another non-used frequency
is higher than another absolute threshold.
The load triggers handover
2C event
the quality in another frequency is higher than an
absolute threshold
The Execution of Inter-frequency Hard Handover
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q y
The execution of Inter-frequency hard handover UE report the timing information
UE with two receivers does not need compressed mode.
Synchronization hard handoverUsing the original DOFF
Continued CFN UE does not report timing information
UE with a single receiver has to initiate compressed mode
If the NodeB of target cell is not the same one which the cellsin active set belong to
the timing re-initiation hard handover
Re-configure DOFF
Calculate the CFN according to DOFF
If the NodeB of target cell is the same one which the cells inactive set belong to Calculate the target cell timing relationship
Synchronization hard handover
Using the original DOFF
Continued CFN
Inter-frequency Hard Handover Flow
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Signaling flow
UE
1.RADIO LINK SETUP REQUEST
TargetNODEB
SourceNODEB SRNC
2. RADIO LINK SETUP RESPONSE
3.ALCAP established
4. PHYSICAL CHANNEL RECONFIGURATION
5. RADIO LINK
FAILURE INDICATION
6. PHYSICAL CHANNEL RECONFIGURATION COMPLETE
7. RADIO LINK
DELETION REQUEST
8. RADIO LINK
DELETION RESPONSE
9.ALCAP released
Key Parameters (I)
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Key Parameters (I)
Inter-frequency coverage handover parameters:
Inter-frequency measurement reporting: periodic reporting or
event reporting Inter-frequency measurement values: CPICH Ec/No or CPICH
RSCP
Inter-frequency measurement layer 3 filter coefficient, delay
trigger time and hysteresis
Inter-frequency initiated and stopped threshold: Considering thedifferent demands of CPICH Ec/No and CPICH RSCP for PS
domain and CS domain, the different 2D and 2F parameters are
configured.
Inter-frequency handover based on coverage: the quality
threshold of target cell Using frequency quality threshold in inter-frequency hard
handover
The minimum access threshold for inter-frequency handover
Key Parameters (II)
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Key Parameters (II)
Inter-frequency handover parameters caused by non-
coverage ability Inter-frequency measurement layer 3 filter coefficient, delay trigger
time and hysteresis
Inter-frequency handover based on non-coverage ability
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Chapter 3 The Basic Handovers
Section 1 Soft Handover
Section 2 Intra-frequency Hard Handover
Section 3 Inter-frequency Hard Handover
Section 4Inter-system Hard Handover
Section 5 HSDPA Handover
Section 6 Compressed Mode
The Brief Introduction of Inter-system Hard
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Handover
Application scenarios WCDMA FDD GSM
WCDMA FDD WCDMA TDD WCDMA FDD CDMA2000
Characters Different radio access technology is used after handover Usually, compressed mode should be used to help the
measurement Advantages For coverage, it can solve the problems from one system
to another system For capacity, it can enhance the utilizing efficiency of old
equipments(2G->3G)
Disadvantages The flow is complicated, and it demands higher
compatibility for equipments Demands more complicated UE
The Measurement for Inter-system
C
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Compressed Mode Initiated
The inter-system measurement (GSM measurement)
Measurement type:GSM Carrier RSSI
BSIC Identification
BSIC Reconfirmation
The process of measurement: layer 1 filter, layer 3 filter
Measurement reporting
Event reporting
2D Event: initiate GSM measurement
2F Event: stop GSM measurement
The Inter-system Hard Handover
D i i Al ith
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Decision Algorithm
The inter-system hard handover decision
Inter-system handover caused by coverageEvent reporting:
3A eventThe 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 .Periodic reporting:
EvaluationAccording to the periodic reported GSM
RSSI measurement value and the BSIC confirming state
of target cell of GSM system, and meanwhile the UE
evaluates the GSM RSSI of target cell is greater than theabsolute threshold, then consider the cell confirmed by
BSIC.
The Inter-system Hard Handover
D i i Al ith
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Decision Algorithm
The inter-system hard handover decision
Inter-system handover caused by non-coverageEvent reporting
3C event: The estimated quality value of the other
system is higher than a absolute threshold.
Inter-system Handover Flow
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The execution of inter-system handover
1. RelocationRequired 2. Prepare
Handover3. Handover
Request
4. HandoverRequest Ack
12. Iu ReleaseCommand
13. Iu ReleaseComplete 14. Send End
Signal Response
5. PrepareHandover6. Relocation
Command7.DCCH: Handover
from UTRAN Command8. Handover
Detect
9. Handover Complete
10. HandoverComplete
11. SendEnd
UE Node B SRNC CN MSC BSC
Key Parameters (I)
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y ( )
Inter-system handover caused by coverage parameters Inter-system measurement initiated and stopped threshold:
Considering the different demands of CPICH Ec/No and CPICHRSCP for PS domain and CS domain, the different 2D and 2Fparameters are configured
Inter-system measurement values (2D, 2F)
CPICH Ec/No
CPICH RSCP BSIC confirmed (Optional) Inter-system handover caused by coverage parameters
configure the GSM RSSI threshold of CS domain and PSdomain separately
Using inter-system frequency quality handover threshold Configure the delay trigger time, hysteresis for each event
Key parameters (II)
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Internal Use 67
y ( )
Inter-system handover caused by non-coverage parameters The period of inter-system measurement report
The decision threshold for inter-system handover: configure theCS, PS, signaling separately
Time delay trigger : configure BSIC with acknowledged andunacknowledged mode
Inter-frequency measurement layer 3 filter coefficient and
hysteresis Penalty time
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Internal Use 68
Chapter 3 The Basic Handovers
Section 1 Soft Handover
Section 2 Intra-frequency Hard Handover
Section 3 Inter-frequency Hard Handover
Section 4 Inter-system Hard Handover
Section 5HSDPA Handover
Section 6 Compressed Mode
The Brief Introduction HSDPA Handover
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Internal Use 69
Application Scope
Related to the handover between the HS-DSCH channel
of HSDPA
The service cell update of HSDPA
HSDPADCH
Purpose
the service which data rate satisfied the threshold ofHSDPA should use the HSDPA resource. To realize the
maximum traffic volume, the service cell with HS-DSCH
should be the best cell in the active set.
HSDPA Measurement
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Internal Use 70
HSDPA handover measurement
Measurement type: CPICH RSCPCPICH Ec/N0Path
loss
The process of measurement: layer 1 filter coefficient and
layer 3 filter coefficient
Measurement reporting
Periodic reportingEvent reporting
Reporting type: 1A, 1B, 1C, 1D
The event reporting converted to periodic
reporting
Service Cell Change Algorithm
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Internal Use 71
Change the service cell for HS-PDSCH in active set
According to 1D event to decide the best cell, and hand it over
to the cell.
After handover, initiate the timer to forbid the ping-pong
handover
Change the service cell for HS-PDSCH after hard handover
Establish the HSDPA channel in target cell with hard handover Establish DCH channel if the target cell can not support HSDPA
Change the service cell for HS-PDSCH during soft handover
The service should be handed over to the cell which support
HSDPA when the best cell does not support HSDPA and the
original service cell for HSDPA already deleted from active set.
Direct Retry for HSDPA
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Internal Use 72
Direct retry from R99 cell to R5 cell Conditions
UE in cell 1 requests to establish an BE/streaming RAB, orUE of Cell-FACH state has much BE/streaming data
volume to transfer (Switch channel type from FACH to HS-DSCH)
Existing cells: support HSDPA, with same coverage area
Advantage: To make full use of HSDPA resource
Direct retry
HSDPA
resource
R5CELL ACarrier B
R99CELL2 R99 CELL 1Carrier A
Service Cell Update Flow
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Internal Use 73
Key Parameters
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Internal Use 74
HSDPA handover protecting timer
Configure the T-HSDPA to avoid the influence for the dataservice caused by the ping-pong handover. During this period,
the service cell for HSDPA can not be changed.
The value scope ( 01024) seconds
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Internal Use 75
Chapter 3 The Basic HandoversSection 1 Soft Handover
Section 2 Intra-frequency Hard Handover
Section 3 Inter-frequency Hard Handover
Section 4 Inter-system Hard Handover
Section 5 HSDPA Handover
Section 6Compressed Mode
The Purpose of Compressed mode
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Internal Use 76
Purpose
Measure the inter-frequency cell or inter-system cell under
FDD mode
Cause:
Downlink compressed:
Since one receiver only can work in one frequency, the
UE has to stop working if it is going to measure the signalfrom another frequency cell. To ensure the downlink
service unaffected, the remained data should be sent in
the limited time.
Uplink compressed
UE should stop the uplink transmission when the uplinkworking frequency is very close to the measured
frequency, for example GSM 1800/1900 is very close to
the UMTS FDD uplink working frequency.
Compressed Mode Sketch Map
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Internal Use 77
Compressed mode sketch map
One frame
(10 ms) Transmission gap available fo r
inter-frequency measurements
The realization Methods of Compressed mode
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Internal Use 78
Realization Methods SF/2
Should use the replace scrambling code
Advantage: easy to handle for RNCDisadvantage: occupied the resource of NodeB, decrease the
utilizing efficiency of OVSF, influenced the coverage andincreased interference caused by the replace scrambling code.
rate matching/puncturing
Decrease the coding redundancyAdvantage: easy to handle for RNC; the SF 4 can be used; no
influence to utilizing efficiency of OVSF
Disadvantage: limited to the property of channel coding;decreased the coding gain
higher layer schedulingMAC can restrict TFCS to change the downlink data rate.
Advantage: the interference is lower
Disadvantage: complicated for higher layer, only fit for non-timing data service.
Questions
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Internal Use 79
What are the differences between soft handover and softer
handover?
What is compressed mode?
Draw out the hard handover signaling flow.
Summary
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Internal Use 80
This chapter focus on the basic handovers in WCDMA: soft handover,
softer handover, intra-frequency hard handover, inter-frequency hardhandover and inter-system hard handover. It also introduced the
application scenarios for these different handovers
Meanwhile, compressed mode is introduced in this chapter
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Internal Use 81
Chapter 1 Introduction of Handover
Chapter 2 Measurement of Handover
Chapter 3 The Basic Handovers
Chapter 4Blind Handover and
Direct Retry Algorithm
Application scenarios and Trigger Conditions
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Internal Use 82
RRC direct retry During the initial signaling establishment, the RRC connection is
refused. RRC redirection
The initial signaling is already established, but the requestedcell refused and RRC direct retry is failed.
RAB direct retry The signaling is established successfully, but the service
establishment is failed. Blind handover
Load balanced between inter-frequency cells RRC direct retry RAB direct retry
RRC Direct Retry (I)
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Internal Use 83
Application scenarios (I)
Same sector covered by different frequencies
cell1
cell2
1 2
3
RRC Direct Retry (II)
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Internal Use 84
Application scenarios (II)
The soft handover area
cell1 cell2
1
2
3
UE camp ing
cel l1 first
RRC Retry Key Parameters
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Internal Use 85
DRMaxNumber The maximum allowed retry times for the direct retry module
after the initial failure CsThreshold.
When the signal quality of a cell is higher than this threshold,this cell will be included in the direct retry candidate set.
MinSignalRequired
The basic access threshold described in Section 2.2.8,namely the minimum requirement of the UE form the receivingCPICH Ec/No density during normal demodulation.
MaxRelatingTime The maximum time that the RACH measurement report can
continue to be used for the direct retry candidate set.
RRC Redirection
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Internal Use 86
Application scenarios
The signaling connection is failed, and RRC retry is also failed.
Inter-freq cell
cell1
1
2
1
GSM cell
1
RRC Direct Retry and Direction
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Internal Use 87
The trigger condition should be the signaling permitting failure
if congestion happed, the RRC connection signaling is refused. Advantages and disadvantages:
RRC direct retry can ensure the time delay. RRC direction is more flexible, and can select to GSM cell. But
the time delay is longer.
RAB Direct Retry
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Internal Use 88
Application scenarios
UTRAN CELL
GSM CELL
1 3
4
Signaling process
1 RAB Assignment (from CN)2 SRNS relocation (to CN)
3 Handover from UTRAN ( Inform UE
access to GSM system)
4 Handover Complete (GSM message)
2
CN
Questions
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Internal Use 89
What is the difference of RRC direct retry and RRCredirection?
What are the trigger conditions for RRC direct retry and RRC
direction?
Summary
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Internal Use 90
This chapter focus on RRC direct retry, RRC redirection, the
application scenarios of RAB direct retry and blind handover.
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