WCDMA Handover Algorithm and Parameters-libre
Transcript of WCDMA Handover Algorithm and Parameters-libre
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WCDMA Handover Principle
and Relevant Parameters
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Foreword
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 islimited.
Providing the continuous service in mobile system is the basic elementin QoS.
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Objectives
Upon completion of this course, you will be able to:
Know the basic definitions of Handover
The algorithms of handover decision
The handover flow
The parameters of handover
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Contents
1. Introduction of Handover
2. Measurement of Handover
3. The Basic Handovers
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The Purpose of Handover
Providing the continuous service in mobile system is thebasic element in QoS
The load balance: sharing the resource
The hierarchy divided by speed and service: high
efficiency of using resource
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The Basic Concepts of Handover Active Set
Monitored Set
Detected set
Radio Link (RL)
Radio Link Set(RLS)
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maximum ratio combination
selection combination
The soft handover gain
CPICH
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The Characters of Different Handover
Comparison between soft handover and hard handover:
Item Soft Handover Hard Handover
The number of RLs in
active set after handover
Several One
Interruption during
handover
No Yes
The frequencies of cells Only happened
between Intra-
frequency cells
Can be happened in Intra-
frequency cells or Inter-frequency
cells
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The Characters of Different Handover
Comparison between soft handover and softer handover :
Item Soft Handover Softer Handover
UL combination Signal combined in
RNC by selective
combination
Signal combined in NodeB by
maximum ratio combination
DL combination Signal combined in
UE by maximum ratio
combination
Signal combined in UE by
maximum ratio combination
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Soft Handover
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RNC
NodeB 2NodeB 1
Cell A Cell B
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Softer Handover
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RNC
NodeB
Cell BCell A
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Hard Handover
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RNC
NodeB 2NodeB 1
Cell A Cell B
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Three Steps of Handover
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Decision
Execution
Measurement
The following figure shows handoverprocedure (measurement quality set toPCPICH Ec/No)
Decision phase
Execution phase
Measurement phase
Yes
NoAre handover criteria satisfied?
Perform a handover and update relative parameters
Measure the CPICH Ec/N0 of the serving cell andits neighboring cells as well as the relative timedifference between the cells
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Contents
1. Introduction of Handover
2. Measurement of Handover
3. The Basic Handovers
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Contents
2. Measurement of Handover
2.1 Measurement Control and Measurement Report
2.2 Measurement Phase
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Measurement Control
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Measurement Control, normal case
UE UTRAN
MEASUREMENT CONTROL
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Measurement Control, normal case
UE UTRAN
MEASUREMENT REPORT
Measurement Report
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Contents
2. Measurement of Handover
2.1 Measurement Control and Measurement Report
2.2 Measurement Phase
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Measurement Model
A is measurement value at the physical layer
B is the measurement value after layer 1 filtering at physical layer. The
value goes from the physical layer to high layer
C is measurement after processing in the layer3 filter
C is another measurement value
D is measurement report information sent on the radio interface or Iub
interface
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Layer 1filtering
Layer 3filtering
Evaluationof reporting
criteria
A DB C
C'
parameters parameters
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Measurement Quantity
Ec/No
CPICH signal quality
RSCP
CPICH signal level
RSSI
GSM cell signal level
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Measurement Quantity Configuration
IntraFreqMeasQuantity Parameter name: Intra-frequency measure quantity
The default value of this parameter is Ec/No
InterFreqMeasQuantity
Parameter name: Inter-frequency measure quantity
The default value of this parameter is Both
MeasQuantityOf3A
Parameter name: 3A Measure Quantity
The default value of this parameter is RSCP
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Layer 3 filtering
Fn is the new measurement value after filtering.
Fn-1 is the last measurement value after filtering.
Mn is the latest measurement value from the physical layer.
a= 1/2(k/2) (k is set to Intra-freq meas L3 filter coeff)
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nnn MaFaF += 1)1(
Where:
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Layer 3 filtering coefficient
FilterCoef Parameter name: Intra-frequency measurement filter coefficient
The default value of this parameter is D3
InterFreqFilterCoef
Parameter name: Inter-frequency measure filter coefficient
The default value of this parameter is D3
InterRATFilterCoef
Parameter name: Inter-RAT filter coefficient
The default value of this parameter is D3
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Measurement Report Mode
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Periodic Report
Event Trigger Report
Event to Periodic Report
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Contents
1. Introduction of Handover2. Measurement of Handover
3. The Basic Handovers
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Contents
3. The Basic Handovers
3.1 Soft Handover
3.2 Intra-frequency Hard Handover
3.3 Inter-frequency Hard Handover
3.4 Inter-RAT Hard Handover3.5 Blind Handover
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Contents
3. The Basic Handovers
3.1 Soft Handover
3.2 Intra-frequency Hard Handover
3.3 Inter-frequency Hard Handover
3.4 Inter-RAT Hard Handover3.5 Blind Handover
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Brief Introduction of Soft Handover Advantages
Soft handover gain
Decrease the possibility of call drop
Disadvantages More resource needed in downlink
it way cause side-effect
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Measurement of Soft Handover Measurement quantity
CPICH RSCP
CPICH Ec/No
Reporting mode Periodic reporting
Event trigger reporting Event trigger reporting to Periodic reporting
Event type 1A,1B,1C,1D,1F
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Soft Handover Measurement EventsEvent Description
1A The PCPICH quality of the cells in the monitored set enters the reporting range.
This indicates that the quality of a cell is close to the quality of the best cell . A
relative high combined gain can be achieved when the cell is added to the active
set
1B The PCPICH quality of the cells in the active set leaves the reporting range. This
indicates that quality of a cell is much worse than the quality of the best cell. The
cell should not stay in the active set
1C A non-active PCPICH becomes better than an active PCPICH. This indicates that
the quality of a cell is close to the quality of the best cell. In addition ,the number of
cells in the active set has reached the maximum value. The cell replaces the worst
cell in the active set ; thus achieving a higher combined gain
1D Event of the change of the best cell
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The Trigger Algorithm of 1A Event
),2/(10)1(1010 111
aaBest
N
i
iNewNew HRLogMWMLogWCIOLogMA
+
+
=
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Event 1A is triggered on the basis of the following formula
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The Trigger Algorithm of 1B Event
),2/(10)1(1010 111bbBest
N
iiOldOld HRLogMWMLogWCIOLogM
A
++
+
=
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Event 1B is triggered on the basis of the following formula
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Example of 1B Event
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A: signal curve of the best cell in the active set
B: signal curve of a cell in the monitoring setC: The 1B curve
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Key parameters of 1B EventINTRARELTHDFOR1BCS
Parameter name: CS service 1B event relative threshold
The default value of this parameter is 12 ( 6dB )
INTRARELTHDFOR1BPS
Parameter name: PS service 1B event relative threshold
The default value of this parameter is 12 ( 6dB )
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Key parameters of 1B EventHYSTFOR1B
Parameter name: 1B event hysteresis
The default value of this parameter is 0( 0dB )
TRIGTIME1B
Parameter name: 1B event trigger delay time
The default value of this parameter is D640 ( 640ms )
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The Trigger Algorithm of 1C Event
,2/10101cInASInASNewNew
HCIOLogMCIOLogM +++
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Event 1C is triggered on the basis of the following formula
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Example of 1C Event
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A: signal curve of the best cell in the active set
B: signal curve of a cell in the active set
C: signal curve of the worst cell in the active set
D: signal curve of a cell in the monitoring set
E: The 1C curve
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Key parameters of 1C EventHYSTFOR1C
Parameter name: 1C event hysteresis
The default value of this parameter is 8( 4dB )
TRIGTIME1C
Parameter name: 1C event trigger delay time
The default value of this parameter is D640 ( 640ms )
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The Trigger Algorithm of 1D Event
,2/10101cInASNew
HLogMLogM +
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Event 1D is triggered on the basis of the following formula
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Example of 1D Event
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A: signal curve of the best cell in the active set
B: signal curve of a cell in the active set or monitoring set
C: Th1D curve
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Key parameters of 1D EventHYSTFOR1D
Parameter name: 1D event hysteresis
The default value of this parameter is 8( 4dB )
TRIGTIME1D
Parameter name: 1D event trigger delay time
The default value of this parameter is D640 ( 640ms )
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Other key parameters for SHO
Weight Parameter name: Weighted factor
The default value of this parameter is 0
SHOQualmin
Parameter name: Min quality THD for SHO The default value of this parameter is -24(-24 dB)
CELLINDIVIDALOFFSET
Parameter name: Cell offset
The default value of this parameter is 0 ( 0dB )
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Contents
3. The Basic Handovers
3.1 Soft Handover
3.2 Intra-frequency Hard Handover
3.3 Inter-frequency Hard Handover
3.4 Inter-RAT Hard Handover
3.5 Blind Handover
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Brief Introduction of Intra-Frequency Handover
Characters of Intra-Frequency Handover During handover, UE has only one RL with one cell
Switch off the RL with the original cell, then setup the RL with targetcell
The frequency of source cell and target cell are same
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Brief Introduction of Intra-Frequency Handover
Advantages Enhance the usage efficiency of the OVSF code and hardware
Disadvantages High call drop possibility because of the intra-frequency interference
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Contents
3. The Basic Handovers
3.1 Soft Handover
3.2 Intra-frequency Hard Handover
3.3 Inter-frequency Hard Handover
3.4 Inter-RAT Hard Handover
3.5 Blind Handover
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Compressed Mode
Purpose Measure the inter-frequency cell or Inter-RAT cell under FDD mode
Categories Downlink compressed mode
Uplink compressed mode
Realization Methods SF/2
Higher layer scheduling
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Measurement of Inter-frequency Handover
Measurement quantity CPICH RSCP
CPICH Ec/No
Reporting mode Periodic reporting
Event trigger reporting Event trigger reporting to Periodic reporting
Event type 2B,2C,2D,2F
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Inter-frequency Handover Measurement Events
Event Description
2D When the current signal quality is lower than the preset threshold , the
UTRAN enables the compressed mode and starts inter-frequency
measurement
2F When the current signal quality is higher than the preset threshold, the
UTRAN disables the compressed mode and stops inter-frequency
measurement
2B When the current signal frequency is lower than the preset threshold and
the signal quality of an inter-frequency neighbouring cell is higher than
the preset threshold , the UTRAN trigger an inter-frequency handover
based on coverage
2C The estimated quality of a inter-frequency neighbor cell is higher than the
preset threshold
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The Trigger Algorithm of 2D Event
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Event 2D is triggered on the basis of the following formula
2/22 ddUsedUsed HTQ
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Key parameters of of 2D Event
InterFreqCSThd2DEcN0
Parameter name: Inter-freq CS measure start Ec/No THD
The default value of this parameter is -14 dB
InterFreqPSThd2DEcN0
Parameter name: Inter-freq PS measure start Ec/No THD
The default value of this parameter is -14 dB
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Key parameters of of 2D Event
InterFreqCSThd2DRSCP
Parameter name: Inter-freq CS measure start RSCP THD
The default value of this parameter is -95 dBm
InterFreqPSThd2DRSCP
Parameter name: Inter-freq PS measure start RSCP THD
The default value of this parameter is -95 dBm
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Key parameters of 2D EventHYSTFOR2D
Parameter name: 2D event hysteresis
The default value of this parameter is 4( 2dB )
TRIGTIME2D
Parameter name: 2D event trigger delay time
The default value of this parameter is D320 ( 320ms )
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The Trigger Algorithm of 2F Event
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Event 2F is triggered on the basis of the following formula
2/22 ffUsedUsed HTQ +
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Key parameters of 2F EventInterFreqCSThd2FEcN0
Parameter name: Inter-freq CS measure stop Ec/No THD
The default value of this parameter is -12 dB
InterFreqPSThd2FEcN0
Parameter name: Inter-freq PS measure stop Ec/No THD
The default value of this parameter is -12 dB
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Key parameters of 2F Event
InterFreqCSThd2FRSCP
Parameter name: Inter-freq CS measure stop RSCP THD
The default value of this parameter is -92 dBm
InterFreqPSThd2FRSCP
Parameter name: Inter-freq PS measure stop RSCP THD
The default value of this parameter is -92 dBm
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Key parameters of 2F Event
HYSTFOR2F
Parameter name: 2F event hysteresis
The default value of this parameter is 4( 2dB )
TRIGTIME2F
Parameter name: 2F event trigger delay time
The default value of this parameter is D1280 ( 1280ms )
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The Trigger Algorithm of 2B Event
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Event 2B is triggered on the basis of the following formula
2/22 bbusedNonusedNon HTQ + 2/22 bbUsedUsed HTQ , and
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Key parameters of 2B Event
InterFreqCovHOCSThdEcN0
Parameter name: Inter-freq CS target frequency trigger Ec/No THD
The default value of this parameter is -12 dB
InterFreqCovHOPSThdEcN0
Parameter name: Inter-freq PS target frequency trigger Ec/No THD
The default value of this parameter is -12 dB
g
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Key parameters of 2B Event
InterFreqCovHOCSThdRSCP
Parameter name: Inter-freq CS target frequency trigger RSCP THD
The default value of this parameter is -92 dBm
InterFreqCovHOPSThdRSCP
Parameter name: Inter-freq PS target frequency trigger RSCP THD
The default value of this parameter is -92 dBm
g
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Key parameters of 2B Event
IFHOUsedFreqCSThdEcN0
Parameter name: Inter-freq CS Used frequency trigger Ec/No THD
The default value of this parameter is -12dB
IFHOUsedFreqPSThdEcN0
Parameter name: Inter-freq PS Used frequency trigger Ec/No THD
The default value of this parameter is -12 dB
g
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Key parameters of 2B Event
IFHOUsedFreqCSThdRSCP
Parameter name: Inter-freq CS Used frequency trigger RSCP THD
The default value of this parameter is -92dBm
IFHOUsedFreqPSThdRSCP
Parameter name: Inter-freq PS Used frequency trigger RSCP THD
The default value of this parameter is -92 dBm
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Key parameters of 2B EventHYSTFOR2B
Parameter name: 2B event hysteresis
The default value of this parameter is 4( 2dB )
TRIGTIME2B
Parameter name: 2B event trigger delay time
The default value of this parameter is D0 ( 0ms )
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The Trigger Algorithm of 2C Event
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Event 2C is triggered on the basis of the following formula
2/22 ccusedNonusedNon HTQ +
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Key parameters of 2C Event
InterFreqNCovHOThdEcN0
Parameter name: Inter-freq CS target frequency trigger Ec/No THD
The default value of this parameter is -16 dB
Hystfor2C
Parameter name: 2C hysteresis The default value of this parameter is 6 (3dB)
TrigTime2C
Parameter name: 2C event trigger delay time
The default value of this parameter is D640 (640ms)
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Contents
3. The Basic Handovers
3.1 Soft Handover
3.2 Intra-frequency Hard Handover
3.3 Inter-frequency Hard Handover
3.4 Inter-RAT Hard Handover
3.5 Blind Handover
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Brief Introduction of Inter-RAT Handover
Characters of Inter-RAT Handover Based on handover directions, inter-RAT handover is of two
types:
UMTS->GSM handover
UMTS->GSM coverage-based handover
UMTS->GSM load-based handover
UMTS->GSM service-based handover GSM->UMTS handover
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Brief Introduction of Inter-RAT Handover
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
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Inter-RAT Handover Measurement Events
Event Description
2D When the signal quality of the currently used frequency is lower than the preset
threshold, the RNC enables the compressed mode and starts inter-RAT
measurement.
2F When the signal quality of the currently used frequency is higher than the preset
threshold, the RNC disables the compressed mode and stops inter-RAT
measurement.
3A When the signal quality of the currently used UMTS frequency is lower than the
preset threshold while the signal quality of any other system is higher than the
preset threshold, the RNC triggers UMTS->GSM handover based on coverage.
3C When the signal quality of any other system is higher than the preset threshold,
the RNC triggers UMTS->GSM handover based on load or service.
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The Trigger Algorithm of 2D Event
2/H-TQ 2dUsed2dUsed
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Event 2D is triggered on the basis of the following formula:
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Key Parameters of 2D Event
INTERRATCSTHD2DECNO
Parameter name: Inter-RAT CS measure start Ec/No THD
The default value of this parameter is -14 ( -14 dB )
INTERRATPSTHD2DECNO
Parameter name: Inter-RAT PS measure start Ec/No THD
The default value of this parameter is -15 ( -15 dB )
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Key Parameters of 2D Event
INTERRATCSTHD2DRSCP
Parameter name: Inter-RAT CS measure start RSCP THD
The default value of this parameter is -100 ( -100 dBm )
INTERRATPSTHD2DRSCP
Parameter name: Inter-RAT PS measure start RSCP THD
The default value of this parameter is -110 (-110 dBm )
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Key Parameters of 2D Event
HYSTFOR2D
Parameter name: 2D hysteresis
The default value of this parameter is 4 ( 2 dB )
TRIGTIME2D
Parameter name: 2D event trigger delay time
The default value of this parameter is D320 (320 ms )
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The Trigger Algorithm of 2F Event
2/HTQ 2fUsed2fUsed +
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Event 2F is triggered on the basis of the following formula:
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Key Parameters of 2F Event
INTERRATCSTHD2FECNO
Parameter name: Inter-RAT CS measure stop Ec/No THD
The default value of this parameter is -12 ( -12 dB )
INTERRATPSTHD2FECNO
Parameter name: Inter-RAT PS measure stop Ec/No THD
The default value of this parameter is -13 ( -13 dB )
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Key Parameters of 2F Event
INTERRATCSTHD2FRSCP
Parameter name: Inter-RAT CS measure stop RSCP THD
The default value of this parameter is -97 ( -97 dBm )
INTERRATPSTHD2FRSCP
Parameter name: Inter-RAT PS measure stop RSCP THD
The default value of this parameter is -107 (-107 dBm )
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The Trigger Algorithm of 3A Event
2/HTQ3aUsed3aUsed
+
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Event 3A is triggered on the basis of the following formula:
2/HTM3aOtherRatOtherRatOtherRat ++CIO
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Key Parameters of 3A Event
IRHOUSEDFREQCSTHDECNO Parameter name: Inter-RAT CS Used frequency trigger Ec/No THD
The default value of this parameter is -12 ( -12 dB )
IRHOUSEDFREQPSTHDECNO
Parameter name: Inter-RAT PS Used frequency trigger Ec/No THD
The default value of this parameter is -13 ( -13 dB )
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Key Parameters of 3A Event
IRHOUSEDFREQCSTHDRSCP Parameter name: Inter-RAT CS Used frequency trigger RSCP THD
The default value of this parameter is -97 ( -97 dBm )
IRHOUSEDFREQCSTHDRSCP
Parameter name: Inter-RAT PS Used frequency trigger RSCP THD
The default value of this parameter is -107 (-107 dBm )
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Key Parameters of 3A Event
INTERRATCOVHOCSTHD Parameter name: Inter-RAT CS handover decision THD
The default value of this parameter is 16 ( -95 dBm )
INTERRATCOVHOPSTHD
Parameter name: Inter-RAT PS handover decision THD
The default value of this parameter is 16 ( -95 dBm )
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Key Parameters of 3A Event
HYSTFOR3A Parameter name: 3A hysteresis
The default value of this parameter is 4 ( 2 dB )
TRIGTIME3A
Parameter name: 3A event trigger delay time
The default value of this parameter is D0 ( 0 ms )
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Key Parameters of 3A Event
CELLINDIVIDALOFFSET Parameter name: Cell individual offset
The default value of this parameter is 0 ( 0 dB )
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The Trigger Algorithm of 3C Event
2/HTM 3cOtherRatOtherRatOtherRat ++CIO
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Event 3C is triggered on the basis of the following formula:
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Key Parameters of 3C Event
INTERRATNCOVHOCSTHD Parameter name: Inter-RAT CS handover decision THD
The default value of this parameter is 21 ( -90 dBm )
INTERRATNCOVHOPSTHD
Parameter name: Inter-RAT PS handover decision THD
The default value of this parameter is 21 (-90 dBm )
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Key Parameters of 3C Event
HYSTFOR3C Parameter name: 3C hysteresis
The default value of this parameter is 0 ( 0 dB )
TRIGTIME3C
Parameter name: 3C event trigger delay time
The default value of this parameter is D640 ( 650 ms )
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Key Parameters of 3C Event
INTERRATMEASTIME Parameter name: Inter-RAT measure timer length [s]
The default value of this parameter is 60 ( 60 s )
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Contents
3. The Basic Handovers3.1 Soft Handover
3.2 Intra-frequency Hard Handover
3.3 Inter-frequency Hard Handover
3.4 Inter-RAT Hard Handover
3.5 Blind Handover
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Blind Handover Measurement
Blind handover means UE can directly handover to theneighboring cell without measuring it.
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The Trigger Algorithm of 1F Event
Where:
MOld is the measurement value of the cell signal that becomesworse
T1f is the absolute threshold of event 1F.H1f is the hysteresis value of event 1F.
2/HTLogM10 f1f1Old
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The Trigger Algorithm of 1F Event
AbsoluteThreshold T1f
Reportingevent 1F
MeasurementQuantity
Time
Cell 1
HysteresisH1f /2
1F Trigger
Delay Time
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Key Parameters of Event 1F
INTRAABLTHDFOR1FECNO Parameter name: 1F event absolute EcNo threshold
The recommended value is -24 dB
INTRAABLTHDFOR1FRSCP
Parameter name: 1F event absolute RSCP threshold The recommended value is -115 dBm
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Key Parameters of Event 1F
HYSTFOR1F Parameter name: 1F hysteresis The recommended value is 8, namely 4 dB
TRIGTIME1F
Parameter name: 1F event trigger delay time The recommended value is D640, namely 640 ms
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Blind Handover Decision
After receiving event 1F of best cell from UE, the RNCwould check if blind handover neighbor is configured forthe cell.
If multiple blind handover neighbors are configured, theRNC would perform blind handover to the target cell
with the highest priority
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Key Parameters of Blind Handover
BLINDHOFLAG Parameter name: Blind handover flag The default value is FALSE
BLINDHOPRIO
Parameter name: Blind handover Priority The value is set according to actual situation.
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