3GSM Radio Network Tuning_Handover (Day3)

7/30/2019 3GSM Radio Network Tuning_Handover (Day3)

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GSM Radio Network Tuning Course2

Subjects

4/8/2008GSM Radio Network Tuning Course

2

1. Overview

2. Handover Decision

3. Target Cell Selection

4. Algorithms5. Power Budget Handover

6. Level & Quality Handover

7. Umbrella Handover

Combined Umbrella & Power Budget

MS Speed8. Imperative Handover

9. Timers for Handovers


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HANDOVER PROCESS: Causes

Timing Advance

Adjacent Cells

Downlink Quality

Uplink Quality AV_RXQUAL_UL_HO

AV_RXQUAL_DL_HO

Downlink Level

Uplink Level AV_RXLEV_UL_HO

AV_RXLEV_DL_HO

AV_RANGE_HO

AV_RXLEV_NCELL(n)

QUALITY&

INTERFERENCE

QUALITY&

INTERFERENCE

LEVEL

LEVEL

DISTANCE

DISTANCE

PERIODICCHECKS

UMBRELLA

UMBRELLA

POWER BUDGET

POWER BUDGET

IMPERATIVEHOCHANNEL ADMINISTRATION

CHANNEL ADMINISTRATION

DIRECTED RETRY

DIRECTED RETRY

THRESHOLD

COMPARISON

RAPID FIELD DROP

RAPID FIELD DROP

Others:

Intelligent Underlay Overlay

Traffic Reason

.

MS SPEED

MS SPEED

MS Speed AV_MS_SPEED


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HANDOVER PROCESSHandover Decision

Handover process may be triggered by

Quality, field strength or distance values

fall below/exceed their threshold

Periodic checksPower budget HO

Umbrella HO


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HANDOVER PROCESS

Handover Priority

Handover priority

1. Uplink and downlink Interference

2. Uplink quality

3. Downlink quality

4. Uplink level

5. Downlink level6. Distance

7. Rapid Field Drop

8. Slow moving MS

9. Better cell i.e. Periodic check (Power Budget HO or Umbrella HO)

10. PC: Lower quality/level thresholds (UL/DL)11. PC: Upper quality/level thresholds (UL/DL)


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HANDOVER PROCESS

Handover Algorithms

AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)

PBGT > hoMarginPBGT(n) where

PBGT = ((msTxPwrMax - msTxPwrMax(n)) - (AV_RXLEV_DL_HO -

AV_RXLEV_NCELL(n))

- (btsTxPwrMax - BTS_TXPWR))

AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, A)

A = msTxPwrMax(n) - P P = depending on MS Classmark

A > hoMarginLev/Qual(n) where

A = (AV_RXLEV_NCELL(n) - AV_RXLEV_DL_HO)-(btsTxPwrMax -

BTS_TXPWR)

1.

2.

1.

In all Handover cases (in imperative HO only requirement)

Except for Umbrella Handover

2.

The additional condition

IfenableHoMarginLevQual = Y


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HANDOVER PROCESS

Target Cell Selection (1/2)

If two or more Adjacent cells with equal priorities

-> Ranking based on radio properties

Load check of Candidates by btsLoadThreshold (0..100%)

If overloaded priority decreased by hoLoadFactor(0...7)

Best candidates to RR Management:

intra BSC HO max 16 cells under the same BSC as the source cell

inter BSC HO numberOfPreferredCells

Comparison of priorities of Candidates (hoLevelPriority

(0..7))

1.

2.

3.

Only for Adjacent

Cell of thesame BSC


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HANDOVER PROCESSTarget Cell Selection (2/2)

All cells have equal priority

cell a b c

Rx_Level -75 -80 -83

1. Load overl. overl. n.overl.

hoLoadFactor 1 1 1

2. Priority 3 3 3

New Priority 2 2 3

3. Rx_Level -75 -80

=> cell list c , a ,b

One cell has higher priority because of some reason

cell a b c

Rx_Level -75 -80 -83

1. Load n./overl. n.overl. n.overl.

hoLoadFactor 2 1 1

2. Priority 4 3 3

New Priority 4/2 3 3

3. Rx_Level -75 -80/-80 -83

=> cell list a,b,c (if cell a is not overload)

=> cell list b,c,a


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HO flow chart

BSC

Eq. 1

orEq. 1'

Adj1..Adj2.Adj3.-----------------

---------------------------------------

Adj32

Adj1Adj3------------

------Adjn

Eq.2or

Eq.2'

Target Cell Evaluation

Cell ranked according to priority/load

Adj1

Adj3-------

Adji

.

Load informationfrom the RRmanagement


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HANDOVER PROCESS

Power Budget Handover (1/2) Trigger

Periodic Check ( hoPeriodPBGT )

Candidate Selection

Equation 1 & 2 used

Priority and Load Considered

Performed ONLY between cells of the same "Layer" if:

umbrella HO is enabled

in inter-band HO case

hoPeriodPBGT 1 ... 63 (SACCH Period)

enablePwrBudgetHandover Y / N

Parameter Value

rxLevMinCell(n) -110 -47 dBmmsTxPwrMax(n) 5 43 dBmhoMarginPBGT(n) -24 63 dB

HOC

ADJC


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PBGT = ((msTxPwrMax- msTxPwrMax(n)) - (AV_RXLEV_DL_HO -

AV_RXLEV_NCELL(n)) - (btsTxPwrMax - BTS_TXPWR)

PBGT = ((33dBm-33dBm)-(-90 - -80)-(42dBm-42dBm)

= 10 dB

10 dB > 6 dB OK !!!!

Equations 1 and 2 are used

AV_RXLEV_DL_HO = -90 dBm

msTxPwrMax = 33 dBm (= 2W)

btsTxPwrMax = 42 dBm (= 16 W)

BTS_TX_PWR = 42 dBm = (16 W)

hoMarginPBGT(n) = 6 dB

Serving Cell: Best Adjacent Cell:

AV_RXLEV_NCELL(n) = -80 dBm

rxLevMinCell(n) = -99 dBm

msTxPwrMax(n) = 33 dBm (= 2W)

btsTxPwrMax = 42 dBm (= 16 W)

AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) - msTxPwrMax)

-80 dBm > -99 dBm + (33 dBm - 33 dBm) = -99 dBm

1.

2.

HANDOVER PROCESS

Power Budget Handover (2/2)


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HANDOVER PROCESS

Handover due to Level (1/2) Trigger

Threshold Comparison ( hoThresholdsLevUL/DL (px - nx) )

Candidate Selection

Equation 1 used

Equation 2 used ifenableHoMarginLevQual = N

Equation 2' with hoMarginLev used if

enableHoMarginLevQual = Y


hoThresholdLevUL/DL -110 -47

px 1 32

nx 1 32

Parameter Value

rxLevMinCell(n) -110 -47 dBmmsTxPwrMax(n) 5 43 dBmhoMarginLev(n) -24 24 dB

HOC

ADJC


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HANDOVER PROCESSHandover due to Level (2/2)

Equations 1 and 2 are used if parameterenableHoMarginLevQual is set Yes

2 dB

hoMarginLev = 4 dB

Trigger for Handover due to Level

A

B

=> Cell B is not selected as candidate for

HO due to level since 2dB < 4 dB

Threshold (Lev)

-95 dBm


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HANDOVER PROCESS

Handover due to Quality (1/2) Trigger

Threshold Comparison ( hoThresholdsQualUL/DL (px - nx) )

Candidate Selection

Equation 1 used

Equation 2 used ifenableHoMarginLevQual = N

Equation 2' with hoMarginQual used ifenableHoMarginLevQual = Y


hoThresholdQualUL/DL 0 7

px 1 32

nx 1 32

Parameter Value

rxLevMinCell(n) -110 -47 dBmmsTxPwrMax(n) 5 43 dBmhoMarginQual(n) -24 24 dB

HOC

ADJC


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HANDOVER PROCESSHandover due to Quality (2/2)

Equations 1 and 2 are used if parameterenableHoMarginLevQual is set Yes

2 dB

hoMarginQual = 0 dB

Trigger for Handover HO due to Quality

A

B

=> Cell B is selected as potential candidate for

HO due to Quality since 2 dB > 0 dB


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HANDOVER PROCESSHandover due to Interference (1/2)

Trigger : Threshold Comparison Threshold Comparison for Quality ( hoThresholdsQualUL/DL (px - nx) ) Threshold Comparison for Level ( hoThresholdsInterferenceUL/DL (px -

nx) )

Candidate Selection Priority for InterCell / Intracell HO selected at BSC independently for UL /

DL Priority InterCell HO Quality HO if any candidate

If not IntraCell HO Priority IntraCell HO

hoThresholdInterferenceUL/DL -110 -47

px 1 32

nx 1 32

enableIntraHoInterfUL/DL Y / N

Parameter Value

hoPreferenceOrderInterfUL/DL INTER / INTRA

BSC

HOC

BSC


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HANDOVER PROCESSHandover due to Interference (2/2)

Equations 1 and 2 are used if parameterenableHandoverMarginQual is set Yes

hoThresholdQual = 4

hoThresholdInterferenceDL = -85 dBm

hoPreferenceOrderInterfDL = intra Trigger for Handover due to Interference

A

B

- Field strength higher than threshold- Bad quality

=> interference

=> intra cell handover !!

Threshold (Interference Lev)

-85 dBm

5

0


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6 dB

Umbrella

Handover

A

B-90 dBm

Handover due

to Level

Macro cell

Micro cellExample

GSM MS class 4 (33 dBm)

gsmMacrocellThreshold = 35 dBm

gsmMicrocellThreshold = 33 dBm

msTxPwrMax(n) = 33 dBm

hoLevUmbrella = -85 dBm

hoThresholdLevDL = -90 dBm

-85 dBm

Umbrella

Handover

Handover due

to Level

HANDOVER PROCESS

Umbrella Handover (1/2) Trigger

Periodic Check ( hoPeriodUmbrella )

Candidate Selection

Equation 1' used

Consistency between mobile classmark and target cell power

constraints


Multi-Layered Network


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HANDOVER PROCESS

Umbrella Handover (2/2)Max power capability of MS >= gsmMacrocellThreshold

HO allowed only to a macrocell ( MS_TXPWR_MAX(n) >=

gsmMacrocellThreshold )

gsmMicrocellThreshold < Max power capability of MS < gsmMacrocellThreshold

HO only to middle size cell ( gsmMicrocellThreshold < MS_TXPWR_MAX(n)

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3GSM Radio Network Tuning_Handover (Day3)