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CDMA1x handover huawei
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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
www.huawei.com
Internal
CDMA 1x Handoff Algorithm
ISSUE 3.0
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 2
Learning Guide
What is Handoff in mobile network?
What is the Search Window?
How to optimize handoff parameters?
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Upon completion of this course, you will be able
to:
Know handoff principle and classification.
Know search window and key parameters.
Master handoff tuning in network.
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Chapter 1 Basic ConceptChapter 1 Basic Concept
Chapter 2 Handoff in CDMAChapter 2 Handoff in CDMA
Chapter 3 Optimization CommandChapter 3 Optimization Command
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What is handoff
BTS_ABTS_B
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Why do we need handoff
To provide the continuous service for subscribers
In wireless communications, during HO process, there is a high probability of call drop, which directly effects the system performance ( 90% of radio call drop occurs during handoff). Proper handoff algorithm can reduce
system call drop and increase network capacity.
Notice
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How many kinds of handoff in CDMA
Soft handoff
It is a process of establishing a link with a target sector before
breaking the link with the serving sector.
Softer handoff
Similar to the soft handoff, but the softer handoff is occurred
among multi-sectors in the same base station.
Hard handoff
Hard handoff occurs when the two sectors are not
synchronized or are not on the same frequency. Interruption in
voice or data communication occurs but this interruption does
not effect the user communication.
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Chapter 1 Basic ConceptChapter 1 Basic Concept
Chapter 2 Handoff in CDMAChapter 2 Handoff in CDMA
Chapter 3 Optimization CommandChapter 3 Optimization Command
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Soft Handoff
It is a process of establishing a link with a target sector before
breaking the link with the serving sector.
Soft handoff branches are selected by BSC.
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Soft Handoff
CDMA soft handoff is driven by the handset
Handset continuously measures available pilots and report
to the system
System assigns sectors (up to 6 max.), informs handset
Handset assigns its fingers accordingly
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Softer Handoff
Similar to the soft handoff, but the
softer handoff is occurred among
multi-sectors in the same base
station.
Softer handoff: Signal of different
branches are combined in BTS.
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Questions
Which channel signal strength from BTS should be compared by
MS during HO process?
How does MS identify which signal is better than others?
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Searcher Correlator
Pilot Sets
Pilots of sectors actually in use
Pilots mobile requested, but not yet being used by system
Pilots being sent to mobile by system, as nearby sectors to measure
Any pilots used by system but not already in the other sets
Active Set Active Set
Candidate Set
Candidate Set
Neighbor Set
Neighbor Set
Remaining Set
Remaining Set
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Handoff Parameters
Handset sends PPilot SStrength MMeasurement MMessage to the
system whenever
It notices a pilot in neighbor or remaining set exceeds T_ADDT_ADD
An active set pilot drops below T_DROPT_DROP for T_TDROPT_TDROP time
A candidate pilot exceeds an active by T_COMPT_COMP
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How to implement Soft Handoff
T_ADDT_ADD
T_DROPT_DROP
Pilot 1
Pilot Strength
Pilot 2
T_TDROPT_TDROP
NeighborSet
CandidateSet
ActiveSet
NeighborSet
TIME1 2 3 4 5 6
ActiveSet
T_COMPT_COMP
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Hard Handoff
MS assistedHard handoff
Pseudo pilotHard handoff
Hand down
Hard handoffDirect
Hard handoff
Hard Handoff
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MS Assisted Hard Handoff
CFSRQM: Candidate Frequency Search Request Message
CFSRSM: Candidate Frequency Search Response Message
CFSCNM: Candidate Frequency Search Order Message
CFSRPM: Candidate Frequency Search Report Message
CFSRPM(Report)
CFSCNM(Search Order)
F1 (serving)
F2 (candidate)
GHDM(HHO)
CFSRQM(Search Parameters)
CFSRSM(Acceptance)
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Pseudo Pilot Hard Handoff
F0F0
F3F3
F2F2
F1F1
F0F0
F1F1
F2F2
F0F0
Sector 1Sector 1 Sector 2Sector 2 Sector 3Sector 3
Pilot BeaconF3
Pilot BeaconF3
Pilot BeaconF1
Pilot BeaconF1
Pilot BeaconF2
Pilot BeaconF2
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F0F0
Hand Down Hard Handoff
F3F3
F2F2
F1F1
F0F0
F1F1
F2F2
F0F0
Sector 1Sector 1 Sector 2Sector 2 Sector 3Sector 3
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Direct Hard Handoff
F2F2 F1F1
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Chapter 1 Basic ConceptChapter 1 Basic Concept
Chapter 2 Handoff in CDMAChapter 2 Handoff in CDMA
Chapter 3 Optimization CommandChapter 3 Optimization Command
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How to search pilot
The purpose of SRCH-WIN set by MS is to capture the multi-path
components, which arrived before or after the current signal. Based on
experience, the SRCH-WIN should be set wide enough so that it can
capture the signal, which has the maximum time delay due to multi-path.
Search Window
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SRCH-WIN Classification
Currently MS uses three kinds of search windows, these are:
SRCH-WIN-ASRCH-WIN-A , used for searching the pilots in the active set and
the candidate set
SRCH-WIN-NSRCH-WIN-N , used for searching the pilots in the neighbor set
SRCH-WIN-RSRCH-WIN-R , used for searching the pilots in the remain set
The MS fixes the width of the search window according to the system
message. An MS can search the multi-path components of the available
pilot signals within the setting.
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The Complete Picture of Handoff & Pilot Sets
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Pilot Searching
SRCH-WIN-ASRCH-WIN-A
The MS can utilize the search window to search the pilots in
the active set and the candidate set based on the PN code.
For pilots in the active set and candidate set, the MS fixes
the center of the search window at the moment, when the
multi-path signal of the pilot reaches earliest.
SRCH-WIN-ASRCH-WIN-A
The earliest arrived pilot
PILOT PHASE
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Pilot Searching
SRCH-WIN-NSRCH-WIN-N
Uses to monitor neighbor set , the size of this window is
larger than SRCH-WIN-A. The distance is measured in term
of chips (1 chips approximately covers 244m).
The distance is measured in term of chips (1 chips approximately covers
244m).
PN4PN4PN4PN4{{
{{
n chip offset with delayed signal necessary n chip offset with delayed signal necessary n chip offset with delayed signal necessary n chip offset with delayed signal necessary PN16PN16PN16PN16
{{n chip offset because of the search center of active set n chip offset because of the search center of active set n chip offset because of the search center of active set n chip offset because of the search center of active set
{{ Expected windowExpected windowExpected windowExpected window
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Pilot Searching
SRCH-WIN-RSRCH-WIN-R
Uses to track the remaining pilots. A typical requirement for
the size of windows is, it should be equal or larger than
SRCH-WIN-N.
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The Pilot Searcher’s Measurement Process
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Delay budget and size of search windowSRCH_WIN_A
Width of SRCH_WIN_A
(Chips)
Delay Budget
(ms)Available PN
0 4 T < 1.64 512
1 6 1.64 < T < 2.45 512
2 8 2.45 < T < 3.27 512
3 10 3.27 < T < 4.09 512
4 14 4.09 < T < 5.72 512
5 20 5.72 < T < 8.17 512
6 28 8.17 < T < 11.44 512
7 40 11.44 < T < 16.34 512
8 60 16.34 < T < 24.51 512
9 80 24.51 < T < 32.68 512
10 100 32.68 < T < 40.85 512
11 130 40.85 < T < 53.11 512
12 160 53.11 < T < 65.36 256
13 226 65.36 < T < 92.32 256
14 320 92.32 < T < 130.72 170
15 452 130.72 < T < 184.42 128
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Questions
Whether data service supports soft handoff?
Considering the fact, high power may affect the system, whether
soft handoff can be performed after reducing the rate?
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How To Optimize Soft Handoff
Reasonable coverage planning and BTS layout
Reasonable setting of T_Add, T_Drop, T_TDROP
Optimize the maximum branches in active handoff
Reasonable planning of handoff region
Reasonable setting of neighbor and neighbor priority
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How To Optimize Soft Handoff MOD HOMOD HO (Modify Handoff Parameters )
This command is executed to modify handoff parameters.
Index: CN -- Cell number, SCTID -- Sector ID, CRRID -- Carrier ID.
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How To Optimize Soft Handoff
MOD BSCHOMOD BSCHO (Modify Inter-BSC Handoff Parameters )
This command is executed to modify handoff parameters at system level.
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Optimize Intra-frequency Hard Handoff
MOD HHOSFMOD HHOSF (Modify Same-Frequency HHO Parameters )
This command is executed to modify same-frequency hard
handoff parameters.
Index: CN -- Cell number, SCTID -- Sector ID, CRRID--
Carrier ID.
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Optimize MS Assistant Hard Handoff
MOD HHOMAMOD HHOMA (Modify Mobile Assisted HHO Parameters )
This command is executed to modify the mobile assisted hard
handoff parameters.
Index: CN -- Cell number, SCTID -- Sector ID, CRRID -- Carrier ID.
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Optimize Pseudo Pilot Hard Handoff
MOD HHOBPLTMOD HHOBPLT (Modify Pilot Beacon HHO Parameters )
This command is executed to modify pilot beacon hard handoff
parameters.
Index: CN -- Cell number, SCTID -- Sector ID, CRRID -- Carrier
ID.
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Optimize Hand Down Hard Handoff
MOD HNDDWNMOD HNDDWN (Modify Hand down HHO Parameters )
This command is executed to modify handdown hard handoff
parameters.
Index: CN -- Cell number, SCTID -- Sector ID, CRRID -- Carrier ID.
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Optimize Direct Hard Handoff
MOD DRCTMOD DRCT (Modify Direct HHO Parameters )
This command is executed to modify direct hard handoff parameters.
Index: CN -- Cell number, SCTID -- Sector ID, CRRID -- Carrier ID.
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Questions
What is Handoff in mobile network?
What is the Search Window?
How to optimize handoff parameters?
www.huawei.com
Thank You