handover process presentation [read-only]

8/12/2019 Handover Process Presentation [Read-Only]

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© NOKIA BSSPAR FOR S9 / 03.04.2000 / Cellular Network Planning page: 1

HANDOVER PROCESSHANDOVER PROCESS

Nokia Networks Thailand

Radio Network Planning

Prepared By

Aumpika Viaun




HANDOVER PROCESSHANDOVER PROCESSContentsContents

1. Overview

2. Handover Decision

3. Target Cell Evaluation

4. Handover Algorithms

5. Level & Quality & Interference

Handover

6. Power Budget Handover

7. Umbrella Handover

•Combined Umbrella & Power Budget

•MS Speed

8. Imperative Handover

9. Timers for Handovers

10. Direct Access to Desired Layer/Band

11. Related Parameters




HANDOVER PROCESSHANDOVER PROCESSCausesCauses

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

LEVEL

DISTANCE

PERIODICCHECKS

UMBRELLA

POWER BUDGET

IMPERATIVEHOCHANNEL ADMINISTRATION

DIRECTED RETRY

THRESHOLDCOMPARISON

RAPID FIELD DROP

Others:

Intelligent Underlay Overlay

Traffic Reason

……….

MS SPEED

MS Speed AV_MS_SPEED




HANDOVER PROCESSHANDOVER PROCESSIntraIntra--BSC HOBSC HO

CH Actvn

CH Actvn Ack

MS BTS (NEW)BTS BSC MSC

HANDO CMDHANDO CMD

HANDO ACC

HANDO Detec

Phys Info

HANDO COM

HANDO COMCH RELEASE

CH RELEASE ACK

HO PERFORMED


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HANDOVER PROCESSHANDOVER PROCESSInter Inter --BSC HOBSC HO

MS BSC (NEW)BSC(OLD) MSC

HANDO REQD ACK

HANDO CMD

HANDO ACC

HANDO COM

HANDO COM

HANDO REQD

HANDO REQD

HANDO CMD

HANDO DET

CLEAR CMD



HANDOVER PROCESSHANDOVER PROCESSHandover PriorityHandover Priority

• Handover priority

1. Uplink and downlink Interference

2. Uplink quality

3. Downlink quality

4. Uplink level5. Downlink level

6. 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)



HANDOVER PROCESSHANDOVER PROCESSHandover AlgorithmsHandover Algorithms

AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)

PBGT > hoMarginPBGT(n) where

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

- (btsTxPwrMax - BTS_TXPWR))

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

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

PBGT > hoMarginLev/Qual(n) where

PBGT = (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

If enableHoMarginLevQual = Y



HANDOVER PROCESSHANDOVER PROCESSTarget Cell Selection (1)Target Cell Selection (1)

The evaluation on the preferred list of the target cells is based on:

4. The load of the neighbouring cells which belong to the sam

1. The radio link measurements

2. Threshold comparison3. The priority levels of the neighbouring cells

as the serving cell.

5. Rx level comparison – if it is needed




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 AdjacentCell of thesame BSC





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 r

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




HANDOVER PROCESSHANDOVER PROCESSHandover due to Level (1/2)Handover due to Level (1/2)

• Trigger

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

• Candidate Selection

• Equation 1 used

• Equation 2 used if enableHoMarginLevQual = N

• Equation 2' with hoMarginLev used if enableHoMarginLevQual = Y• Priority and Load Considered

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




HANDOVER PROCESSHANDOVER PROCESSHandover due to Level (2/2)Handover due to Level (2/2)

Equations 1 and 2’ are used if parameter enableHoMarginLevQual 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

hoThresholdsLevUL/DL




HANDOVER PROCESSHANDOVER PROCESSHandover due to Quality (1/2)Handover due to Quality (1/2)

• Trigger

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


• Equation 1 used

• Equation 2 used if enableHoMarginLevQual = N

• Equation 2' with hoMarginQual used if enableHoMarginLevQual = Y• Priority and Load Considered

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




HANDOVER PROCESSHANDOVER PROCESSHandover due to Quality (2/2)Handover due to Quality (2/2)

Equations 1 and 2’ are used if parameter enableHoMarginLevQual 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

hoThresholdsQualUL/DL




HANDOVER PROCESSHANDOVER PROCESSHandover due to Interference (1/2)Handover due to Interference (1/2)

• Trigger : Threshold Comparison

• Threshold Comparison for Quality ( hoThresholdsQualUL/DL (px - nx) )

• Threshold Comparison for Level ( hoThresholdsInterferenceUL/DL (px - nx) )


• Priority InterCell / Intracell selected at BSC independently UL / DL

• Priority Inter

Quality HO if Any Target

Otherwise Intra Cell HO

enableIntraHoInterfUL/DL Y / N

hoThresholdInterferenceUL/DL -110 … -47

px 1 … 32

nx 1 … 32

Parameter Value

hoPreferenceOrderInterfUL/DL INTER / INTRA

BSC

• Priority Intra

Intra Cell HO




HANDOVER PROCESSHANDOVER PROCESSHandover due to Interference (2/2)Handover due to Interference (2/2)

Equations 1 and 2’ are used if parameter enableHandoverMarginQual 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




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 !!!!

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

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

1.

2.

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)

HANDOVER PROCESSHANDOVER PROCESSPower Budget Handover (1)Power Budget Handover (1)





• Trigger

• Periodic Check ( hoPeriodPBGT )


• Equation 1 & 2 used

• Priority and Load Considered

•Typically used between cells of the same "Layer"

hoPeriodPBGT 1 ... 63 (SACCH Period)

enablePwrBudgetHandover Y / N

Parameter Value

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





time

cell 1

cell 2

RX_lev

HoMarginPBGT

“ “ Power Budg et HO” Power Budg et HO”




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 dBmmsTxPwrMax(n) = 33 dBm

hoLevUmbrella = -85 dBm

hoThresholdLevDL = -90 dBm

-85 dBm

Umbrella

Handover

Handover due

to Level

HANDOVER PROCESSHANDOVER PROCESSUmbrella Handover (1)Umbrella Handover (1)

• Trigger

• Periodic Check ( hoPeriodUmbrella )


• Equation 1' used

• Consistency between mobile classmark and target cell power constraints

• Priority and Load Considered

• Multi-Layered Network





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) <gsmMacrocellThreshold )

Max power capability of MS <=

HO allowed only to microcell ( MS_TXPWR_MAX(n) <= gsmMicrocellThreshold )

enableUmbrellaHandover Y / NhoPeriodUmbrella 0 … 63 (SACCH)

hoLevelUmbrella -110 … -47

Parameter Value

gsmMicrocellThreshold 5 … 43

gsmMacrocellThreshold 5 … 43 BSC





Cell 1 (GSM 900)

Cell 2 (DCS 1800)

RX_lev (dBm)

time

“ “ Umb rel la HO” Umb rel la HO”

HoLevelUmbrella




macrocells

microcells

UMB,RR

PBGT,RR

PBGT,RR

UMB,RR

UMB umbrella HORR radio reason HO

PBGT power budget HO

HANDOVER PROCESSHANDOVER PROCESSCombined Umbrella & Power BudgetCombined Umbrella & Power Budget

• When

enablePowerBudgetHo = Yes & enableUmbrellaHo = Yes

• Power Budget Handover to cells of the same layer

• Umbrella Handover to cells of different layer

• Based on

•gsmMacrocellThreshold, gsmMicrocellThreshold

• msTxPwrMax, msTxPwrMaxCell(n)

• MS classmark




HANDOVER PROCESSHANDOVER PROCESSMS SpeedMS Speed

• Multi-Layer Network

• Slow Moving MS in Microcells

• Problem :

• Determine the MS speed

•Direct MS to correct Layer

• Fast Moving MS in Macrocells

• Methods (Nokia specific)

• Fast moving MS handling (S5)

•MS speed detection (S6)




HANDOVER PROCESSHANDOVER PROCESSImperative Handover Imperative Handover

• Handover considered to be imperative:

• Handover due to Distance

• Order to empty a cell ( from O&M )

• Directed Retry and IDR

• Rapid Field Drop




HANDOVER PROCESSHANDOVER PROCESS

Imperative Handover: DistanceImperative Handover: Distance

Distance Process ---> msDistanceBehaviour (0,1..60,255) in BSC

• 0 : Release immediately

• 1 - 60 : Release after certain time 1 - 60 s, try handover during th

• 255 : No release, only imperative Handover attempt

Distance Process

enableMsDistanceProcess Y / N

msDistanceHoThresholdParam 0 … 63px 1 … 32

nx 1 … 32

Parameter Value

msDistanceBehaviour 0, 1 … 60, 255 BSC




MS

hoThresholdLevULforRapidFieldDrop -110 ... -47 dBm

hoThresholdRapidLevU1N 0 ... 32

chainedAdjacentCell Y / N

Chained

CellServing

Cell

HANDOVER PROCESSHANDOVER PROCESSImperative Handover :Rapid Field Drop (1/2)Imperative Handover :Rapid Field Drop (1/2)

• Trigger

• Threshold Comparison ( HoThresholdRapidLevUl (px) )

• Rx_Lev_UL (Not averaged / Only UL)


• Only Chained adjacent cell

• Equation 1 only / no priority

• Multi-Layered Network

Parameter Value




MS

Rapid Field Drop Handover ..1st

2nd

hoThresholdRapidLevUl = - 93 dBm

hoThresholdRapidLevUlN (px) = 2

chainedAdjacentCell = Yes

ChainedCellServingCell

-93 dBm

Serving

Cell

HANDOVER PROCESSHANDOVER PROCESSImperative Handover :Rapid Field Drop (2/2)Imperative Handover :Rapid Field Drop (2/2)

Example




HANDOVER PROCESSHANDOVER PROCESSTimersTimers

• Minimum time between consecutive handovers related to the same connections

• MinIntBetweenHoReq

• Minimum time between handover attempts after a failure

• MinIntBetweenUnsuccHoAttempt

• Applied differently in Intercell / Intracell handovers

• Additional Guard Periods are used for Back-handovers

• Quality

• Distance

• Traffic reason

• Interference

minIntBetweenUnsuccHoAttempt 0 ... 30 (seconds)

minIntBetweenHoReq 0 ... 30 (seconds)

Parameter Value




Direct Access to Desired Layer/Band (1/2)Direct Access to Desired Layer/Band (1/2)

• DADL/B is DR like procedure, triggered due to exceded TCH load in accessed cell

• Target cells are selected according to MS properties, radio environment and adjacent cellindications and priorities

• Allows also the support for Phase 1 MSs

• BENEFIT: By directing the calls to proper layer / band as early as possible the network canabsorb more traffic and thus provide more capacity

E-GSM 900 cell

GSM 1800 cell

P-GSM 900

micro cell

accessed P-GSM

900 macro cell

2nd

1st3rd

TCH

TCH

TCH

SDCCH




• DADL/B is applied in call setup phase if

• DADL/B feature is enabled with BSC level optionality management parameter • TCH load of accessed cell exceeds the BTSLoadThreshold

• There are adjacent cells defined with the d adlbTargetCel l parameter (cells verifiedaccording to MS capabilities), which are to be used as target cells for DADL/B handover.

• The signal level of the DADL/B target cell exceeds the HOLevelUmbrella(n)

• BSC will evaluate the target cells for DADL/B handover during the time indicated with theMinTimeLimitDR parameter

• Adjacent cell priorities HOPriori tyL evel(n) and load factors HOLoadFactor(n) are used intarget cell sorting for DADL/B handover

• DR will be applied if there is real TCH congestion in accessed cell

• If the DADL/B handover fails (no TCHs available in target cells, no DADL/B target cells, MSreturns to old channel) the TCH is tried to allocate attempted from the accessed cell

• Pre-emption has higher priority than DADL/B handover

DADL/B functionality (2/2)DADL/B functionality (2/2)



DEFAULTDEFAULT PARAMETERsPARAMETERs SETTING FOR AIS’s PROJECTSETTING FOR AIS’s PROJECT

&&

RELATED ISSUED DISCUSSIONRELATED ISSUED DISCUSSION

(REFERENCE DOCUMENTS)(REFERENCE DOCUMENTS)

HANDOVER PROCESSHANDOVER PROCESSRELATED PARAMETERSRELATED PARAMETERS

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