08- OWJ200102 WCDMA Handover Algorithm and Parameters
Transcript of 08- OWJ200102 WCDMA Handover Algorithm and Parameters
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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page1
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 coverageability is limited.
Providing the continuous service in mobile system is the basic
element in 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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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 the
basic 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)
maximum ratio combination
selection combination
The soft handover gain
CPICH
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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-RAT handover (UMTS GSM/GPRS)
According to the purpose of handover:
Based on Coverage
Based on Noncoverage
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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 inactive 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
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
Comparison between soft handover and softer handover :
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Soft Handover
RNC
NodeB 2NodeB 1
Cell A Cell B
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Softer Handover
RNC
NodeB
Cell BCell A
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Hard Handover
RNC
NodeB 2NodeB 1
Cell A Cell B
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Three Steps of Handover
Decision
Execution
Measurement
The following figure shows handover
procedure (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 and
its neighboring cells as well as the relative time
difference between the cells
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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, normal case
UE UTRAN
MEASUREMENT CONTROL
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
Layer 1
filteringLayer 3
filteringEvaluation
of reporting
criteria
A DB C
C'
parameters parameters
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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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 Intr a-freq meas L3 fi l ter coeff)
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
Periodic Report
Event Trigger Report
Event to Periodic Report
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Contents
1. Introduction of Handover
2. 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 Handover
3.5 Blind Handover
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Brief Introduction of Soft Handover
Characters of Soft Handover
During handover, UE has several RLs with different cells
The handover among different cells which are in same RLS can be
softer handover
Signals from each RL will be combined in UL and DL.
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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 Descr ip t ion
1A The PCPICH quality of the cells in the monitored set enters the repor t ing 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 repor t ing 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 worstcell in the active set ; thus achieving a higher combined gain
1D Event of the change of the best cell
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Example of 1A Event
A: signal curve of the best cell in the active set
B: signal curve of a cell in the monitoring set
C: The 1A curve
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Key parameters of 1A Event
INTRARELTHDFOR1ACS
Parameter name: CS service 1A event relative threshold
The default value of this parameter is 6 ( 3dB )
INTRARELTHDFOR1APS
Parameter name: PS service 1A event relative threshold
The default value of this parameter is 6 ( 3dB )
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Key parameters of 1A Event
HYSTFOR1A
Parameter name: 1A event hysteresis
The default value of this parameter is 0( 0dB )
TRIGTIME1A
Parameter name: 1A event trigger delay time
The default value of this parameter is D320 ( 320ms )
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The Trigger Algorithm of 1B Event
Event 1B is triggered on the basis of the following formula
),2/(10)1(1010 111
bbBest
N
i
iOldOld HRLogMWMLogWCIOLogMA
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Example of 1B Event
A: signal curve of the best cell in the active set
B: signal curve of a cell in the monitoring set
C: The 1B curve
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Key parameters of 1B Event
INTRARELTHDFOR1BCS
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 Event
HYSTFOR1B
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
Event 1C is triggered on the basis of the following formula
,2/1010 1cInASInASNewNew HCIOLogMCIOLogM
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Example of 1C Event
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 Event
HYSTFOR1C
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
Event 1D is triggered on the basis of the following formula
,2/1010 1cInASNew HLogMLogM
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Key parameters of 1D Event
HYSTFOR1D
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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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 target
cell
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-frequencyinterference
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Key parameters of Intra-frequency Hard handover
BEBITRATETHD
Parameter name: BE service handover rate threshold
The default value of this parameter is 384k
The Parameters about 1D Event
Time to trigger
Hysteresis
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Brief Introduction of Inter-Frequency Handover
Characters of Soft Handover
The frequency of original cell and source cell are different
There is only one RL for the UE
The compressed mode is needed
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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 Descr ipt ion
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 handoverbased 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
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 Event
HYSTFOR2D
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
Event 2F is triggered on the basis of the following formula
2/22 ffUsedUsed HTQ
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Key parameters of 2F Event
InterFreqCSThd2FEcN0
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
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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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
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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
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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
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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 Event
HYSTFOR2B
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
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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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
Brief Introduction of Inter-RAT 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 Descr ip t ion
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-RATmeasurement.
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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K P t f 2D E t
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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 )
K P t f 2D E t
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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 )
Th T i Al ith f 2F E t
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The Trigger Algorithm of 2F Event
2/HTQ 2fUsed2fUsed
Event 2F is triggered on the basis of the following formula:
K P t f 2F E t
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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 )
K P t f 2F E t
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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 )
K P t f 2F E t
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Key Parameters of 2F Event
HYSTFOR2F Parameter name: 2F hysteresis
The default value of this parameter is 4 ( 2 dB )
TRIGTIME2F Parameter name: 2F event trigger delay time
The default value of this parameter is D1280 (1280 ms )
Th T i Al ith f 3A E t
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The Trigger Algorithm of 3A Event
2/HTQ 3aUsed3aUsed
Event 3A is triggered on the basis of the following formula:
2/HTM 3aOtherRatOtherRatOtherRat CIO
K P t f 3A E t
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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 )
K P t f 3A E t
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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
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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 )
Key Parameters of 3A Event
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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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Key Parameters of 3C Event
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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 )
Key Parameters of 3C Event
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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 )
Key Parameters of 3C Event
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Key Parameters of 3C Event
PENALTYTIMEFORINTERRATHO Parameter name: Inter-RAT handover failure penalty timer
length
The default value of this parameter is 30 ( 30 s )
INTERRATHOATTEMPTS
Parameter name: Inter-RAT handover max attempt times
The default value of this parameter is 16
Key Parameters of 3C Event
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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 )
Contents
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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
Blind Handover Measurement
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Blind Handover Measurement
Blind handover means UE can directly handover to theneighboring cell without measuring it.
The Trigger Algorithm of 1F Event
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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
The Trigger Algorithm of 1F Event
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The Trigger Algorithm of 1F Event
Absolute
Threshold T1f
Reporting
event 1F
Measurement
Quantity
Time
Cell 1
Hysteresis
H1f/2
1F TriggerDelay Time
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Key Parameters of Event 1F
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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
Blind Handover Decision
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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 for the
cell.
If multiple blind handover neighbors are configured, the
RNC would perform blind handover to the target cell with
the highest priority
Key Parameters of Blind Handover
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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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