S6-3 Handover

1 © NOKIA 1999 ho.ppt/ July 2000 /

HANDOVER PROCESS


HANDOVER PROCESSContents

1. Overview

2. Handover Decision

3. Target Cell Selection

4. Algorithms

5. Power Budget Handover

6. Level & Quality Handover

7. Umbrella Handover

• Combined Umbrella & Power

Budget

• MS Speed

8. Imperative Handover

9. Timers for Handovers

10. C/I Based Handover Candidate

Evaluation

11. Traffic Reason Handover


HANDOVER PROCESS

What is the purpose of HO?What is the purpose of HO?

Call continuityCall quality

Others...

Call continuityCall quality

Others...


HANDOVER PROCESSCauses

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

LEVELLEVEL

DISTANCEDISTANCE

PERIODICCHECKS

UMBRELLAUMBRELLA

POWER BUDGETPOWER BUDGET

IMPERATIVE HOCHANNEL ADMINISTRATIONCHANNEL ADMINISTRATION

DIRECTED RETRYDIRECTED RETRY

THRESHOLD COMPARISON

RAPID FIELD DROPRAPID FIELD DROP

Others:

Intelligent Underlay Overlay

Traffic Reason

……….

MS SPEEDMS SPEED

MS Speed AV_MS_SPEED


HANDOVER PROCESSHandover Desicion

Handover process may be triggered by

• Quality, field strength or distance values fall below/exceed their threshold

• Periodic checksPower budget HOUmbrella HO


HANDOVER PROCESSHandover Priority

• Handover priority

1. Uplink and downlink Interference2. Uplink quality3. Downlink quality4. Uplink level 5. Downlink level6. Distance7. Rapid Field Drop8. Slow moving MS9. 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 Algorithms

AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)

PBGT > hoMarginPBGT(n) wherePBGT = ((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

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 PROCESSTarget 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 cellinter BSC HO numberOfPreferredCells

Comparison of priorities of Candidates (hoLevelPriority (0..7))

1.

2.

3.

Only for Adjacent Cell of the same BSC


HANDOVER PROCESSTarget Cell Selection (2/2)

All cells have equal priority

cell a b c

Rx_Level -75 -80 -831. Load overl. overl. n.overl. hoLoadFactor 1 1 12. Priority 3 3 3 New Priority 2 2 3

3. Rx_Level -75 -80 -83

=> cell list c , a ,b

One cell has higher priority because of some reason

cell a b c

Rx_Level -75 -80 -831. Load n./overl.n.overl.n.overl. hoLoadFactor 2 1 12. Priority 4 3 3 New Priority 4/2 3 3

3. Rx_Level -75 -80 -83

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


HANDOVER PROCESSPower Budget Handover (1/2)

• Trigger

Periodic Check ( hoPeriodPBGT )

• Candidate Selection

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


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 usedEquations 1 and 2 are used

AV_RXLEV_DL_HO = -90 dBmmsTxPwrMax = 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 dBmrxLevMinCell(n) = -99 dBmmsTxPwrMax(n) = 33 dBm (= 2W)btsTxPwrMax = 42 dBm (= 16 W)

HANDOVER PROCESSPower Budget Handover (2/2)


HANDOVER PROCESSHandover due to Level (1/2)

• Trigger

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


Equation 1 used

Equation 2 used if enableHoMarginLevQual = N

Equation 2' with hoMarginLev used if enableHoMarginLevQual = Y


hoThresholdLevUL/DL -110 … -47px 1 … 32nx 1 … 32

Parameter Value

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


HANDOVER PROCESSHandover 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

=> Cell B is not selected as candidate for HO due to level since 2dB < 4 dB

Threshold (Lev)-95 dBm


HANDOVER PROCESSHandover 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


hoThresholdQualUL/DL 0 … 7px 1 … 32nx 1 … 32

Parameter Value

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


HANDOVER PROCESSHandover 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

=> Cell B is selected as potential candidate for HO due to Quality since 2 dB > 0 dB


HANDOVER PROCESSHandover due to Interference (1/3)

• Trigger : Threshold Comparison

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

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


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 … -47px 1 … 32nx 1 … 32

enableIntraHoInterfUL/DL Y / N

Parameter Value

hoPreferenceOrderInterfUL/DL INTER / INTRABSC



Equations 1 and 2’ are used if parameter enableHandoverMarginQual is set “Yes”

hoThresholdQual = 4hoThresholdInterferenceDL = -85 dBmhoPreferenceOrderInterfDL = intra Trigger for Handover due to Interference

A

B

- Field strength higher than threshold- Bad quality=> interference=> intra cell handover !!

- Field strength higher than threshold- Bad quality=> interference=> intra cell handover !!

Threshold (Interference Lev) -85 dBm

5

0


• Intracell HO based on the UL idle channel interference measurements can effectively avoid UL interference when the network load is reasonable

0 1 2 3 4 5 6 7

RTSL

TRX 1

TRX 2

f1, f2, f3

0 1 2 3 4 5 6 7

TRX 1

TRX 2

TRX 3

f1, f2, f3

• When the load is high in the network, the gain of intracell HO is low

0 1 2 3 4 5 6 7

RTSL

TRX 1

TRX 2

f1, f2, f3

0 1 2 3 4 5 6 7

TRX 1

TRX 2

TRX 3

f1, f2, f3

Low

High

Low

High

Idle channel interference level

Idle channel interference level



6 dB

UmbrellaHandover

A

B-90 dBm

Handover dueto Level

Macro cell

Micro cellExample

GSM MS class 4 (33 dBm)gsmMacrocellThreshold = 35 dBmgsmMicrocellThreshold = 33 dBmmsTxPwrMax(n) = 33 dBm

hoLevUmbrella = -85 dBmhoThresholdLevDL = -90 dBm

Example

GSM MS class 4 (33 dBm)gsmMacrocellThreshold = 35 dBmgsmMicrocellThreshold = 33 dBmmsTxPwrMax(n) = 33 dBm

hoLevUmbrella = -85 dBmhoThresholdLevDL = -90 dBm

-85 dBm

UmbrellaHandover

Handover dueto Level

HANDOVER PROCESSUmbrella Handover (1/2)

• Trigger

Periodic Check ( hoPeriodUmbrella )


Equation 1' used

Consistency between mobile classmark and target cell power constraints


• Multi-Layered Network


HANDOVER PROCESSUmbrella 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) < gsmMacrocellThreshold )Max power capability of MS <= gsm MicrocellThreshold

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

enableUmbrellaHandover Y / NhoPeriodUmbrella 0 … 63 (SACCH)hoLevelUmbrella -110 … -47

Parameter Value

gsmMicrocellThreshold 5 … 43gsmMacrocellThreshold 5 … 43 BSC


macrocells

microcells

UMB,RR

PBGT,RR

PBGT,RRUMB,RR

UMB umbrella HORR radio reason HOPBGT power budget HO

HANDOVER PROCESSCombined 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, msTxPwrMax(n)

MS classmark


upper layer (macro)

same layer (serving layer)

lower layer (micro)

HANDOVER PROCESS Adjacent Cell Layer Definition

• Three layers visible to serving cell

• To be used in

Fast moving MS handling in macro cell

HOs based on MS speed (BSS6)

Combined umbrella and power budget

Umbrella HO

• Supports multilayer networks

N (not in use)

Parameter adjacentCellLayer


HANDOVER PROCESSMS 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)


Macro cell’s parametersfor each adjacent micro cell:

• fastMovingThreshold 0 .. 255• rxLevMinCell• hoLevelUmbrella

BSC

micro

macro as serving cell

Counter for each adjacent micro cell +2measurement and over rxLevMinCell -1 no meas. or bad level

Target cell selection based on adjacentcell RX_LEVEL and on hoLevelUmbrella

HANDOVER PROCESSMS Speed : Fast Moving MS Handling

• Fast Moving MS Handling in macro layer

# of measurements received from adjacent microcells

slow or fast moving MS



FMMS Example macrocells

microcells

measured signal strength

HO

hoLevelUmbrella = -85 dBm

RxMinCell = -95 dBm

FMT Counter

HO

FMT Threshold=40

time ‘t’

time ‘t’


HANDOVER PROCESSMS SpeedFMMS Example

macrocells

microcells

measured signal strength

HO

hoLevelUmbrella = -85 dBmRxMinCell = -85 dBm

FMT Counter

HO

FMT Threshold=40

time ‘t’

time ‘t’


HANDOVER PROCESSMS Speed : MS Speed Detection (1/3)

• BTS detects the MS speed by using crossing rate algorithm

BTS supports measurement of MS speed

Call is on non-hopping TCH (no SDCCH, no Hopping TRX)

• BTS sends MS speed indications every SACCH multiframe period (480 msec.)

Speed Indications are not valid if

( * ) UL DTX was used during the SACCH period

( ** ) MS was changing output power during the SACCH period



• BSC Averages MS speed indications

• Window Size is msSpeedAveraging ( pre processing in BTS )

• Result is AV_MS_SPEED

• BSC ignores non valid speed indications ( * , ** )

• AV_MS_SPEED is compared with Thresholds

• LowerSpeedLimit

• UpperSpeedLimit

• px and nx are in common



• LowerSpeedLimit : Enables identification / triggers handover for slow-moving MS

• UpperSpeedLimit : Enables identification / triggers handover for fast-moving MS

• Target Cell Selection

Fast-moving to upper / Slow-moving to lower layer adjacent cells

Equation 1' used

Priority considered

msSpeedAveraging 1 ... 32 (SACCH Period)

Parameter Value

adjCellLayer N / Same / Upper / LowerhoLevelUmbrella -110 ... -47 dBm

0 means "Not Used"

lowerSpeedLimit 0 … 255upperSpeedLimit 0 … 255msSpeedThresholdNx 1 … 32msSpeedThresholdPx 1 … 32



BSCBTS

BTS

macrocell with RF hopping

microcell(s) , no RF hopping

fast MSs

slow MSs

meas_res

Crossing rate algorithmBS

S6/M

S s

peed

BS

S5/F

ast

MS

Adjacent cell measurements

HO&PCalgorithm

Combination of Fast Moving MS Handling (BSC) and MS Speed Detection (BTS)


HANDOVER PROCESSImperative 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 considered to be imperative:

• Handover due to Distance

• Order to empty a cell ( from O&M )

• Directed Retry and IDR

• Rapid Field Drop


HANDOVER PROCESS Imperative Handover:

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

• 0 : Release immediately• 1 - 60 : Release after certain time 1 - 60 s, try handover

during that time• 255 : No release, only imperative Handover attempt

Distance Process

enableMsDistanceProcess Y / NmsDistanceHoThresholdParam 0 … 63

px 1 … 32nx 1 … 32

Parameter Value

msDistanceBehaviour 0, 1 … 60, 255 BSC


MS

hoThresholdLevULforRapidFieldDrop -110 ... -47 dBmhoThresholdRapidLevU1N 0 ... 32

chainedAdjacentCell Y / N

Chained Cell

Serving Cell

HANDOVER PROCESSImperative 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 dBmhoThresholdRapidLevUlN (px) = 2chainedAdjacentCell = Yes

Chained Cell

Serving Cell

-93 dBm

Serving Cell

HANDOVER PROCESSImperative Handover :Rapid Field

Drop (2/2)

Example


HANDOVER PROCESS Imperative Handover:Enhanced Rapid Field Drop

(1/3)

• In case of DDE (Deep Dropping Edge), the averaging window sizes and power budget period are reduced

• level downlink window size• level uplink window size• adjacent cell averaging window size• handover period power budget

A MS moves away from cell site,the signal is dropping gradually

A MS turns a corner,the signal drops rapidly

Sign

al L

evel

Time Figure 7 Signal Strength of a Fast Moving MS

MS moves away from cell site,the signal is dropping gradually

MS turns a corner, thesignal drops faster thanmoving in straight line

Sign

al L

evel

TimeFigure 8 Signal Strength of a Slow Moving MS


HANDOVER PROCESS Imperative Handover:Enhanced Rapid Field Drop

(2/3)

ParameterParameter ValueValue

erfdEnablederfdEnabled DIS, UL, DL or UDLDIS, UL, DL or UDL

ddeThresholdLevddeThresholdLev 0 … 63 dB0 … 63 dB

NxNx 1 … 321 … 32

PxPx 1 … 321 … 32

ddeWindowddeWindow 1 … 32 SACCH1 … 32 SACCH

modifiedAveWinNcellmodifiedAveWinNcell 1 … 32 1 … 32

modifiedNOZmodifiedNOZ 1 … 321 … 32

erfdOvererfdOver 1 … 64 sec1 … 64 sec


HANDOVER PROCESS Imperative Handover:Enhanced

Rapid Field Drop (3/3)Example

ddeWindow = 3 SACCH (n = 3)

ddeThresholdLev = 10, px = 2 and nx =3

• the BSC compares the most recent measurement sample 8 (multiframe k) with the measurement sample 5 (multiframe k-n).

• DDE_LEVEL = RXLEV(k- ddeWindow) – RXLEV(k) = -69 dBm – (-83 dBm) = 14 dB

Sample 1 2 3 4 5 6 7 8Signallevel

-71dBm

-68dBm

-70dBm

-71dBm

-69dBm

-70dBm

-75dBm

-83dBm


HANDOVER PROCESSPractical Examples

1. Adjacent Channel in Adjacent Cell

2. Cell with Very Large Coverage Area

• In practice after -6 dB -> interference increases and quality goes down to 4-5

• hoMarginLev < 6 dB

• MS switched off in cell A and transferred to area of cell X

C I - 9 dBa •

A X

20 km

• • xx

• MS switched on in new place -> MS tries first old channel + neighbours

• MS camped on cell A which is not in neighbour list of cell X -> do not listen BCCH of cell X -> no HOs to cell X !!!

a

b

- 9dB


HANDOVER PROCESSTimers

• 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


HANDOVER PROCESSTimers (HO Failure)

• Reversion to old channel OR no radio resource available

MinIntBetweenUnsuccHoAttempt applied only to intra-cell handover attempts

• Other failure cases (BSS failures)

MinIntBetweenUnsuccHoAttempt applied to all types of handover attempts

• Reversion to old channel

( 1 + NUMBER_OF_HO_FAIL ) * MinIntBetweenUnsuccHoAttempt

applied to handover attempts to the same target cell

• No Radio Resource Available

MinIntBetweenUnsuccHoAttempt applied to handover attempts to the same target cells ( all those in the list )

• Other Failure Cases

MinIntBetweenUnsuccHoAttempt applied to all types of handover attempts


HANDOVER PROCESSTimers ( Guard period for back - handover )

• after a HO due to quality (UL/DL) and interference (UL/DL):

a Power Budget HO back is not allowed during

GUARD_TIME = 2 * HoPeriodPBGT

an Umbrella HO back is not allowed during

GUARD_TIME = 2 * HoPeriodUmbrella

• after an inter-cell HO due to MS-BS distance:

a HO back to the source cell is not allowed during

GUARD_TIME = 20sec + MinIntBetweenHOReq

• after a Traffic Reason HO:

Power Budget HO and Umbrella HO back to the source are not allowed during

GUARD_TIME = 20sec + MinIntBetweenHOReq

• Repetitive Intra Cell HO not allower during

GUARD_TIME = 4 * MinIntBetweenUnsuccHoAttempt


Advanced Multilayer Handling:Advanced Multilayer Handling: three features conceptthree features concept

Load PBGTm Penalty IUO MCN

>80 0 60 - -

<50 - - Yes Yes

Intelligent underlay-overlay

Handover

Multilayerhandling

GSM/superGSM/super

GSM1800/microGSM1800/micro

AMH 1

AMH 2

AMH 3


AMH 1: BSC Initiated TRHO benefits (1/2)

Handover

+0 dB +4dB +6 dB

•Network wide load can be smoothed out by reducing power budget margins between heavy loaded and less loaded cells => more trunking efficiency => more capacity•Capacity of the regular layer can be released and performance of IUO is increased => Quality + capacity

• Ping-pong handovers are avoided due to AMH penalty system => quality


AMH 1: BSC Initiated TRHO benefits (2/2)

New algorithm:

1. AV_RXLEV_NCELL(n) > TRHO_TARGET_LEVEL(n)+Max(0,(MS_TXPWR_MAX_CELL(n)-P))

2.PBGT (n) > AmhTrhoPbgtMArgin and PBGT(n) < HOMArginPBGT

AmhTrhoPbgtMargin -24dBm..+24dBm,NAmhUpperLoadThreshold 0…100%AmhMaxLoadOfTgtCell 0…100% TrhoGuardTime 0…120 sec

Parameters Values


AMH 2:IUO Load Control benefits

super-reuse TRXsuper-reuse TRX

•During a very light load, only regular frequencies are used. Thus additional handovers are avoided => increases quality


AMH 3: Multilayer Load Control

benefits

GSM/macroGSM/macro

DCS/microDCS/micro

• Avoid additional handovers between different layers => quality

•In the night time, when the load is very small, and the speed of the MS’s can be very fast, the MS’s can be kept in the macro cell layer => quality


AMH 2 and AMH 3Parameters

Parameters Values

AmhTrafficControlIUO Y/N

AmhTrafficControlMCN Y/N

AmhLowerLoadThreshold 0…100%


Direct Access to Desired Layer/Band (1/3)

• 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 cell indications 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 can absorb more traffic and thus provide more capacity

E-GSM 900 cell

GSM 1800 cellP-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 dadlbTargetCell parameter (cells verified according 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 the MinTimeLimitDR parameter

• Adjacent cell priorities HOPriorityLevel(n) and load factors HOLoadFactor(n) are used in target 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, MS returns 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 (2/3)


DADL/B applications (3/3)• The use of DADL/B is flexible with adjacent cell indications

and thus DADL/B can be tailored to different environments / concepts

1st2nd

Office

1st

2nd

Multilayer

Multiband

GSM 900 micro

Multilayer & band

GSM 900

GSM 1800

GSM 900 macro

GSM 1800

Documents

S6-3 Handover