07 rn20107en14gln0 handover control and adjacencies

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Handover Control and Adjacencies

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1 Nokia Siemens Networks RN20107EN14GLN0

BSSPAR1: Chapter 7Handover Control and Adjacencies

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Module Objectives

Explain the motivation for handover Indicate the different types of handover and multi layer network Describe the principle steps to be executed for handover (averaging,

triggering, adjacent cell ranking, target cell selection, timer) Discuss the handover algorithms applied to interference, RX quality and RX

level handover Discuss the handover algorithms applied to power budget and umbrella

handover, and the impact of the MS speed Describe the different kinds of imperative handovers, especially the role of

rapid field drop Explain the use of handover for traffic control Explain the use of IMSI based handover Handover types not discussed here:

AMR packing/unpacking DTM based handover Inter-system handovers (GSM WCDMA)

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Intra cellOnly other carrier / timeslot

Inter cellIntra BSC

Inter BSCIntra MSC

Inter MSC

Inter PLMNGlobal Cell ID requiredMCC + MNC + LAC + CI

Germany Czech Republic

Intra PLMNSimple Cell ID requiredLAC + CI

Handover Types

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New Channel, New Cell

ACTIVE CALL

HANDO CMD

HANDO ACCHANDO ACCHANDO ACCHANDO ACC

HANDO COM

ACTIVE CALL

MS NETWORK

Old Channel, Old Cell

Original and target cells controlled by same BCF No timing advanced information required for MS Inter cell handover from one sector to another of same site (BCF)

Synchronized Handover Signalling

MO Class Abbreviated Name Range And Step Default value BSC - MML Name

ADCE synchronized not synchronized (N) (0), synchronized (Y) (1)

not synchronized (N) (0)

SYNC

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MS NETWORK

ACTIVE CALL

HANDO CMD

HANDO ACC.

HANDO ACC

PHYS INFO

PHYS INFO

HANDO COM

ACTIVE CALL


maxNumberOfRepetition (NY1) 5..35

Source and target cells controlled by different BCF Timing advanced information required for MS Inter cell handover from one BTS to another

Timer T3124 in MS (320 ms)

Non Synchronized Handover Signalling

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HANDOVER CMD

ACTIVE CALL

MS NETWORK

HANDOVER FAIL

ACTIVE CALL



Timer T3103 expiry orRadio link failure

Handover Failure Signalling

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Multi Layer Network Types

Coverage Layer: Gives access to the networkCapacity Layer: Provides additional capacity and allows traffic distribution

Macro cells

Micro cells Intelligent Underlay OverlayDifferent frequencies for high / low power TRx

Normalfrequency

Super reusefrequency

GSM 900 cellGSM 1800 cell

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threshold

Actual average samples

Nx samplesLess than Px samples >= thresholdNo handover triggered

Nx samplesPx samples are >= thresholdhandover triggered

Signal interference thresholdshoThresholdsInterferenceDL/UL (IDR/IUR) -110..-47 dBm

Signal quality thresholdshoThresholdsQualDL/UL (QDR/QUR) 0..7

Signal level thresholdshoThresholdLevelDL/UL (LDR/LUR) -110..-47 dBmhoThresholdRapidLevelUL (RPD) -110..-47 dBm

MS speed thresholdsupper/lowerSpeedLimit (USL/LSL) 0..255 (unit = 2km/h)

Number of average samplesNx 1..32Px 1..32

Target cell selection

Handover StrategyTriggering

Trigger Point When the set threshold has been met or exceeded Px times of Nx times

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More than one handover criterion fulfilled -> process of higher priority performedHandover and power control criteria fulfilled -> handover performed

1) Interference (uplink or downlink)2) Intra-segment inter-band because of downlink level (from higher to lower frequency band) 3) Uplink quality4) Downlink quality5) AMR unpacking (uplink level and also uplink unpacking quality triggers)6) Uplink level7) AMR unpacking (downlink level and also downlink unpacking quality triggers)8) Downlink level9) Coverage based inter-system handover to WCDMA RAN10) IMSI-based inter-system handover to WCDMA RAN11) IMSI-based handover12) DTM-based handover to WCDMA RAN13) Inter-system handover to WCDMA RAN14) MS-BS distance (maximum or minimum)15) Turn-around-corner MS16) Rapid field drop17) Slow/fast-moving MS18) Umbrella19) Power budget20) DTM-based handover to a GSM DTM cell21) BSC-initiated TRHO22) IUO23) Intra-segment HO based on load24) AMR packing because of good uplink and downlink quality25) AMR unpacking because of bad uplink or downlink quality26) PC because of lower quality thresholds (uplink and downlink)27) PC because of lower level thresholds (uplink and downlink) 28) PC because of upper quality thresholds (uplink and downlink)29) PC because of upper level thresholds (uplink and downlink)

Handover Strategy(Priorities)

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Cell a b c

Overloaded? N/Y N NPriority 4 3 3 hoLoadFactor 2 1 1Corrected priority 4/2 3 3Rx level -75 -80 -83

No cell overloaded -> priorities 4,3,3 -> cell list a,b,cA overloaded -> priorities 2,3,3 -> cell list b,c,a

Cell a b c

Overloaded? N/Y N NPriority 4 3 3 hoLoadFactor 2 1 1Corrected priority 4/2 3 3Rx level -75 -80 -83

No cell overloaded -> priorities 4,3,3 -> cell list a,b,cA overloaded -> priorities 2,3,3 -> cell list b,c,a

Adjacent Cell Load Threshold Can be checked only for cells belonging to the same BSC as the serving onebtsLoadThreshold (BLT) 0..100 %

Adjacent Cell PriorityhoPriorityLevel (PRI) 0..7

Overloaded Cell -> Reduction of PriorityhoLoadFactor (OF) 0..7

Ranking (not for imperative and traffic reason handover)1) Corrected priority2) Cells with same priority -> RX level

Handover StrategyStandard Target Cell Ranking

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AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) P)P depends on MS power class

1a

Any kind of handover (except umbrella)

AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)1b

Umbrella handover

Minimum allowed signal level for target cell

rxLevMinCell (SL) -110..-47 dBm any handover (except umbrella)hoLevelUmbrella (AUCL) -110..-47 dBm umbrella handover

Handover StrategyDecision due to Rx Level

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PBGT > hoMarginLev/Qual(n)PBGT = (AV_RXLEV_NCELL(n) - AV_RXLEV_DL_HO) -

(btsTxPwrMax - BTS_TXPWR)

2b

PBGT > hoMarginPBGT(n)PBGT = (msTxPwrMax - msTxPwrMax(n))

(AV_RXLEV_DL_HO - AV_RXLEV_NCELL(n)) -(btsTxPwrMax - BTS_TXPWR)

2a

General case

Handover due to RX level, RX quality, distance and umbrella handover

Power budget margin to prevent repeated handovers between adjacent cellshoMarginPBGT (PMRG) -24..63 dB general case

RX level and RX quality margins to prevent repeated handovers between adjacent cellshoMarginQual (QMRG) -24..24 dB handover due to signal qualityhoMarginLevel (LMRG) -24..24 dB handover due to signal levelEnableHOMarginLevQual (MRGS) Y/N required to enable margins

Handover StrategyDecision due to Power Budget

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ciEstMethod (HOC) AVE (Average taking method)MAX (Maximum taking method)NONE (C/I estimation not used)

LAC1-5 (ADJC) Location area code of reference cell 1-5 0 ... 65535CI1-5 (ADJC) Cell identification of reference cell 1-5 0 ... 65535 L1-5 (ADJC) Level adjustment for reference cell 1-5 - 63 ... 63 dBW1-5 (ADJC) C/I estimation weight parameter for reference cell 1-5 0 ... 10

Designed to estimate the level of the potential interference for each handover candidate (used during the target cell evaluation process) The purpose is to direct the mobile station to a cell which can provide a minimum interference service at the current location of the MS Enabled using parameter ciEstMethod (HOC) on a cell-by-cell basis Each Adjacent Cell can have up to 5 "reference cells"

Real source of interference or just reference Reference cells must be adjacent cells for MS to report measurements

Parameter Value

C/I Based HO Candidate Evaluation

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lowerCIlimit (L1-L6)(HOC) L1 (Lower C/I limit for band 1) -128 ... 127 dBL2 (Lower C/I limit for band 2) -128 ... 127 dB.L6 (Lower C/I limit for band 6) -128 ... 127 dB

priorityAdjStepforBand1 P1 (Priority adj. for band 1) -8 ... 7(P1-P7)(HOC) P2 (Priority adj. for band 2) -8 ... 7

P6 (Priority adj. for band 6) -8 ... 7

C/I is calculated for the handover candidates Averaged over the reference cells (Average) By taking the worst interferer (Maximum)C/I is compared to 7 user-defined bands Priority of the Cell is incremented by the quantity

associated with the band

Parameter Value

-8 Eliminates the Adjacent Cell from the candidates list

C/I Calculation

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Estimation of C/IFor each adjacent cell: reference cells (indicated by LAC and cell identification)ciEstMethod AVE -> C/I averaged over all reference cells

MAX -> C/I taken from worst reference cell

ciEstWeight (W1-W10) 0 -> reference cell not used1..10 -> individual weight for average C/I

levelAdjustment (L1-L10) -63..63 dB -> signal difference adjacent reference cell

Comparison with user defined interference bandlowerCLimit (L1-L6) -128..127 dB

Correction of prioritypriorityAdjStep (P1-P7) -8 -> cell removed from target candidate list

-7..7 -> priority decreased/increased in dependence on C/I

C/I Based HO Candidate EvaluationParameters

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C/I estimates used to: Remove any HO candidates whose predicted C/I is below acceptable level Increase priority rating of cells with good C/I Reduce priority rating of cells with bad C/IModified cell priority equation:

PRIORITY(n) = hoPriorityLevel(n) - hoLoadFactor(n) + CI_Priority_Factor(n)

Applies to all handover cases that use priority levels(e.g. PBGT, RxLev, RxQual, Umbrella)but not imperative handovers & traffic reason handover(e.g. DR, RFD, distance)

C/I Modified Cell Priority

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Interference band lowerCILimit priorityAdjStep1 30 32 25 13 20 04 17 -15 13 -26 9 -5

Cell a b cOverloaded? Y N NPriority 4 3 3 hoLoadFactor 2 1 1Corrected priority 2 3 3C/I 28 18 22C/I band 1 4 3priorityAdjStep 3 -1 0Corrected priority 5 2 3Rx level -75 -80 -83

Without C/I correction -> priorities 2,3,3 -> cell list b,c,aWith C/I correction -> priorities 5,2,3 -> cell list a,c,b

Interference band lowerCILimit priorityAdjStep1 30 32 25 13 20 04 17 -15 13 -26 9 -5

Cell a b cOverloaded? Y N NPriority 4 3 3 hoLoadFactor 2 1 1Corrected priority 2 3 3C/I 28 18 22C/I band 1 4 3priorityAdjStep 3 -1 0Corrected priority 5 2 3Rx level -75 -80 -83

Without C/I correction -> priorities 2,3,3 -> cell list b,c,aWith C/I correction -> priorities 5,2,3 -> cell list a,c,b

C/I Modified Cell PriorityExample

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Minimum time between consecutive handovers related to same connectionminIntBetweenHOReq (MIH) 0..31 s

Minimum time between consecutive handover attempts after failureminIntBetweenUnsuccHOAttempt (MIU) 0..31s

Time interval between consecutive RX level estimations of the adjacent cells for power budget and umbrella handoverhoPeriodPBGT (HPP) 0..63 SACCH periodshoPeriodUmbrella (HPU) 0..63 SACCH periods

Basic timers do not stop averaging and threshold comparison

Basic Handover Timers

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First handover Back handover Guard Time

Interference / RX quality power budget 2 * hoPeriodPBGTInterference / RX quality umbrella 2 * hoPeriodUmbrella

Interference slow MS 255 s

Distance any 20 s + minIntBetweenHOReq

Traffic reason power budget / umbrella 20 s + minIntBetweenHOReq

Intra cell Intra cell 4 * minIntBetweenUnsuccHOAttempt

Guard timers do not stop averaging and threshold comparison

Guard Handover Timers

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Thresholds

hoThresholdsInterferenceDL/UL -110..-47 dBmhoThresholdsQualDL/UL 0..7

Intra / inter cell handover

hoPreferenceOrderInterDL/UL (HDL/HUL) INTRA for network without frequency hopping

INTER for network with frequency hoppingenableIntraHOInterDL/UL Y/N required to enable intra cell

handover

Interference HandoverParameters

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AvRX level hoThresholdsInterferenceDL/ULAND

AvRX quality value hoThresholdsQualDL/UL

If hoPreferenceOrderInterDL/UL = INTER(perform Intra cell HO if preference is INTRA)

Ranking of adjacent cells

enableHOMarginLevQual = Y enableHOMarginLevQual = N

Check of adjacent cells with conditions 1a and 2b

Check of adjacent cells with conditions 1a and 2a

Suitable adjacent cell ?

Yes No

Inter cell handover Intra cell handover (if enabled)

Otherwise Handover failure

Interference HandoverExecution

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hoThresholdQualDL = 4 /Px:4, Nx:6hoThresholdInterferenceDL = -85 dBm /Px:1, Nx:1hoMarginQual = 0 dB

hoPreferenceOrderInterfDL = INTERenableHandoverMarginLevQual = YBTS output power = Maximum

BOTH the Quality and Interference Threshold is exceeded (bad_RxQuality/good_RxLevel) INTERFERENCE HO

BOTH the Quality and Interference Threshold is exceeded (bad_RxQuality/good_RxLevel) INTERFERENCE HO

Adjacent cells evaluation

Conditions 1a and 2b:

AV_RXLEV_NCELL AV_RXLEV_DL_HO > hoMarginQual fulfilled

If no adjacent -> Intra HO




If no adjacent -> Intra HO

-85

-90

-80

Serving cellAdjacent cell(n)

RX Level

Suitable HO target cell:

RxLev(n) RxLev


RxLev(n) RxLev

hoThresholdInterferenceDL

t1 t2

RX Quality

hoThresholdQualDL

3

4

2

5

6

Serving cell

t1 t2

Adjacent cell(n)

HOHO

Interference HandoverExample

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AvRX quality value hoThresholdsQualDL/UL






Yes No

Inter cell handover Handover failure

ThresholdshoThresholdsQualDL/UL 0..7

RX Quality HandoverExecution

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If no adjacent -> HO Fail





hoThresholdQualDL = 4 /Px:4, Nx:6hoMarginQual = 3 dB

Quality Threshold is met (bad_RxQuality) QUALITY HOQuality Threshold is met (bad_RxQuality) QUALITY HO

enableHandoverMarginLevQual = YBTS output power = Maximum

-85

-90

-80

Serving cell

Adjacent cell(n)

RX Level


RxLev(n) RxLev


RxLev(n) RxLev

t1 t2

RX Quality

hoThresholdQualDL

3

4

2

5

6

Serving cell

t1 t2

Adjacent cell(n)

hoThresholdLevDL

HOHO

Rx Quality HandoverExample

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AvRX level hoThresholdsLevDL/UL






Yes No


ThresholdshoThresholdsLevDL/UL -110..-47 dBm

RX Level HandoverExecution

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hoThresholdLevDL = -95 dBm /Px: 1, Nx: 1hoMarginLevel = 3 dB

enableHandoverMarginLevQual = YBTS output power = Maximum



AV_RXLEV_NCELL AV_RXLEV_DL_HO > hoMarginLevel fulfilled




AV_RXLEV_NCELL AV_RXLEV_DL_HO > hoMarginLevel fulfilled


-95

-100

-90 Serving cell

RX Level

hoThresholdLevelDL

Level Threshold is met (bad_RxLevel) LEVEL HOLevel Threshold is met (bad_RxLevel) LEVEL HO

HOHO

-95

-100

-90Serving cell

Adjacent cell(n)

RX Level

3 dB

t1 t1t2 t2

Suitable target cell:RxLev(n) RxLev+3dBSuitable target cell:

RxLev(n) RxLev+3dB

Rx Level HandoverExample

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Estimation of RX levels of adjacent cells



Adjacent cell with sufficient RX level / power budget

Yes No

Inter cell handover No handover

Must be enabled withenablePwrBudgetHandover (EPB) Y/N

Serving cell measurements need not exceed a threshold

Periodic check of RX levels of adjacent cellshoPeriodPBGT 0..63 SACCH periods

Power Budget HandoverExecution

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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 > 6 dBPBGT > hoMarginPBGT(n) fulfilled

AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) - msTxPwrMax)-80 dBm > -99 dBm + (33 dBm - 33 dBm) = -99 dBm fulfilled

1a

2a

AV_RXLEV_DL_HO = -90 dBmmsTxPwrMax = 33 dBmBTS_TX_PWR = 42 dBmbtsTxPwrMax = 42 dBm

Serving Cell: Best Adjacent Cell:

AV_RXLEV_NCELL(n) = -80 dBmrxLevMinCell(n) = -99 dBmmsTxPwrMax(n) = 33 dBmbtsTxPwrMax = 42 dBmhoMarginPBGT(n) = 6 dB

Power Budget HandoverExample

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Serving cell: AHO candidate target cells: B, C, D

All cells have the following parameter set:rxLevMinCell= -99 dBmmsTxPwrMax= 33 dBmbtsTxPwrMax= 42 dBmhoMarginPBGT= 6 dB

Target cell hoPriorityLevel:B priority: 4C priority: 3D priority: 3

Target cell HOLoadFactor:B load factor: 2C load factor: 1D load factor: 1

Target cell B is considered overloaded

BTS BTS

BTS

BTSBSC

A B

C

D

Which cell (B/C/D) will be chosen as target for the Power Budget HO?

Which cell (B/C/D) will be chosen as target for the Power Budget HO?

AV_RXLEV_NCELL (B)= -80 dBmAV_RXLEV_NCELL (C)= -83 dBmAV_RXLEV_NCELL (D)= -85 dBm

Serving cell A:AV_RXLEV_DL_HO= -92 dBmBTS_TX_PWR= 42 dBm

Exercise Solution

Power Budget HandoverExercise

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Must be enabled withenableUmbrellaHandover (EUM) Y/N

Serving cell measurements need not exceed a threshold

Periodic check of RX levels of adjacent cellshoPeriodUmbrella 0..63 SACCH periods

Thresholds to determine layers of adjacent cellsgsmMacrocellThreshold (GMAC) 5..43 dBm for GSM 900 / 800dcsMacrocellThreshold (DMAC) 0..36/32 dBm for GSM 1800 / 1900gsmMicrocellThreshold (GMIC) 5..43 dBm for GSM 900 / 800dcsMicrocellThreshold (DMIC) 0..36/32 dBm for GSM 1800 / 1900

Umbrella HandoverParameters

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PTCH >= Macrocell Threshold -> adjacent cell = macro cell Microcell Threshold < PTCH < Macrocell Threshold -> adjacent cell = middle size cell PTCH adjacent cell = micro cell

Maximum MS output power allowed on TCH: PTCH -> defined for every adjacent cellMaximum MS output capability : PMAX -> defined by power class

PMAX >= Macrocell Threshold -> only handover to macro cell Microcell Threshold < PMAX < Macrocell Threshold -> only handover to middle size cell

PMAX only handover to micro cell

Cell classification criteria (what cell type is the adjacent cell): consider PTCH

Handover criteria (where is the MS allowed to handover to): consider PMAX

Umbrella HandoverAdjacent Cell Classification

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Estimation of RX levels and PTCH check of adjacent cells

Ranking and layer classification of adjacent cells

Check of adjacent cells with condition 1b

Adjacent cell with sufficient RX level and of correct layer

Yes No

Inter cell handover No handover

Umbrella HandoverExecution

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Umbrella handover to 1800 cell

Umbrella handover to 1800 cell

A

B

900 Macro

hoLevelUmbrella = -85 dBmgsmMacrocellThreshold = 33 dBmdcsMacrocellThreshold = 33 dBm

Threshold RX level handover 95 dBm

Threshold umbrella handover 85 dBm

PTCH (msTxPwrMax(n)) = 30 dBm -> micro cellPMAX = 30 dBm -> handover to micro cell onlyhoThresholdLevelDL = -95 dBm

1800 Micro

RX level handoverback to 900 cell

RX level handoverback to 900 cell

Umbrella HandoverExample

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enablePowerBudgetHo = Yes & enableUmbrellaHo = YesPower budget handover to cells of the same layerUmbrella handover to cells of different layer

Combined Umbrella & Power Budget HOOverview

macrocells

microcells

RR

PBGT,RR

PBGT,RRUMBR

UMBR umbrella HORR radio reason HOPBGT power budget HO

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UPPER layer (macro)

SAME layer (serving layer)

LOWER layer (micro)

Predefinition of layer possible by adjCellLayer (ACL)Three layers visible relative to serving cellUsed for target cell evaluation Combined umbrella and power budget Handover based on MS speed Fast moving MS handling in macro cell

N (no predefinition)

Combined Umbrella & Power Budget HOAdjacent Cell Classification

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Mobile distribution in multi layer networks based on speed

Slow moving MS -> lower layer (micro) cells -> optimum capacity use Fast moving MS -> upper layer (macro) cells -> reduction of signalling traffic

Two proprietary features Fast Moving Mobile Support (FMMS)

Estimation of MS speed based on number of measurement reports fromadjacent micro cells

used to move MS from UPPER (macro) to LOWER (micro) cell

MSSpeed Detection Measurement of MS speed by counting fading dips Used to move slow/fast MS from macro/micro to micro/micro cell

Combined Umbrella & Power Budget HOImpact of MS Speed

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Macro cell

Micro cell

time t

Counter

Slow moving MShandover triggered

time t

Estimation of MS speed based on measurement reports from adjacent micro cellsMS enters macro cell -> counter is startedrxLevMinCell -110..-47 dBm if micro cell has higher level -> counter +2

otherwise counter 1fastMovingThreshold (FMT) 0..255 SACCH frames if exceeded -> handover to micro cell triggered

target cells selected as for umbrella handover

Threshold umbrellahandover 85 dBm

Fast movingthreshold 40

Micro cell has sufficient RX levelHandover possible

Combined Umbrella & Power Budget HOFast Moving MS Support

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Measurement of MS speed based on number of fading dips crossing the average signal level

Speed thresholds

upperSpeedLimit (USL) 0..255 units of 2 km/h if exceeded -> handover to upper layer (macro) celllowerSpeedLimit (LSL) 0..255 units of 2 km/h if exceeded -> handover to lower layer (micro) cellNx 1..32 Number of averaged values taken for comparisonPx 1..32 Number of averaged values which must exceed

threshold

Crossing rate measurements not reliable for

Frequency hopping networkDTX during current or previous SACCH framePower control

Combined Umbrella & Power Budget HOMS Speed Detection

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BSCBTS

BTS

Macro cell with RF hopping

Micro cells without RF hopping

fast MSs

slow MSs Crossing rate algorithmas no RF hopping

Adjacent cell

measurements

Handoveralgorithm

Upper speed thresholdexceeded

Slow MS

No crossing rate algorithmbecause of RF hoppingBut fast moving MS support

Combined Umbrella & Power Budget HOCombined MS Speed Handling

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MS just entered macro cell Counter = 0

Check of adjacent cells with condition 1a

Fulfilled -> counter + 2 Not fulfilled -> counter -1

Yes

Slow moving MS HO to micro cell

Counter > fast moving threshold

MS just entered micro cell

Measurement of MS speed

MS speed > upper speed threshold

No

Fast moving MS No HO

Yes

Fast moving MS HO to macro cell

No

Slow moving MS No HO

Combined Umbrella & Power Budget HOMS Speed Handling Execution

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No TCH available during call set up in serving cell -> handover to TCH of other cell

Must be enabled withdrInUse (DR) Y/N

Thresholds to be exceeded by target cell according condition (1a)drMethod (DRM) 0/1 Defined type of thresholdrxLevMinCell -110..-47 dBm Used if drMethod = 0drThreshold (DRT) -110..-47 dBm Used if drMethod = 1 and

drThreshold > rxLevMin CellTimers (to be counted from TCH assignment)minTimeLimitDirectedRetry (MIDR) 0..14 s No target cell evaluation

allowedmaxTimeLimitDirectedRetry (MADR) 1..15 s Target cell evaluation allowed

SDCCH

TCH

congested TimeAssignmentRequest

minTimeLimitDR

maxTimeLimitDR

DR not allowed DR allowed

Directed RetryParameters

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TCH available in serving cell

Yes No

Estimation of RX levels of adjacent cells


Check of adjacent cells with condition 1a

Adjacent cell with sufficient RX level

Yes No

Directed retry handover Call set up fails

Normal call set up

Directed RetryExecution

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congestion

macro cell (GSM cell)

micro cells (MCN cells)

GSM subscriberBoth GSM and MCN cellsallowed as target

congestion

macro cell (GSM cell)

micro cells (MCN cells)

Target cell selection including cell and subscriber type

Must be enabled withidrUsed (IDR) Y/N

Cell type classificationidrcellType (CTY) GSM/MCN GSM = macro cell

MCN = micro cell

Subscriber classification byPower classPriority (defined by network administrator)

Directed Retry to external BSSdisableExtDr Y/N N possible only, if directed retry supported(DEXDR) by all BSCs and the MSC

MCN subscriberOnly MCN cellsallowed as target

Intelligent Directed Retry

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Target cell selection including cell and subscriber type

Must be enabled withenableMSDistanceProcess (EMS) Y/N

Distance thresholdsmsDistanceHoThresholdParam (MSR) 0..63 63 = maximum allowed distanceNx (MSN) 1..32 Number of averaged values taken for comparisonPx (MSP) 1..32 Number of averaged values which must exceed

threshold

Procedures after handover triggeringmsDistanceBehaviour (DISB) 0 Call released immediately

1..60 s Handover attempt within given timeUnsuccessful attempt -> call released

255 Just handover attemptUnsuccessful attempt -> call still supported by old cell

MS BTS Distance Handover

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Normal RX level handover -> triggered by averaged measurements-> too slowly in case of rapid field drop

Rapid field drop handover -> triggered by raw measurements-> can react immediately

ThresholdshoThresholdsRapidLevUL (RPD) -110..-47 dBm Raw uplink level to be exceededhoThresholdsRapidLevUIN (CNT) 0..32 1..32 = number of consecutive

measurements which must exceed RX level threshold0 = rapid field drop handover disabled

Target cell selectionchainedAdjacentCell (CHAIN) Y/N Cell must be defined as chained cell

Rapid Field Drop HandoverParameters

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RX level hoThresholdsRapidLevUIN consecutive times below hoThresholdsRapidLevUL

Ranking of chained adjacent cells only according RX level

Check of adjacent cells with conditions 1a


Yes No


ThresholdshoThresholdsRapidLevUL -110..-47 dBmhoThresholdsRapidLevUIN 1..32

Rapid Field Drop HandoverExecution

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ChainedCell

1st

2nd

Serving cell

hoThresholdRapidLevUL = -93 dBmhoThresholdRapidLevUlN = 2chainedAdjacentCell = Y

Threshold rapid field drophandover 93 dBm

Handover triggered

Serving Cell

Rapid Field Drop HandoverExample

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

MS turns a corner, the signal drops rapidly

Sign

al L

evel

Time

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

MS turns a corner, the signal drops faster than moving in straight line

Sign

al L

evel

Time

Fast moving MS Slow moving MS

Enhanced Rapid Field Drop HandoverScenarios

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Mast be enabled witherfdEnabled (ERFD) DIS,UL,DL,UDL DIS = disabled

UL/DL = only downlink/uplink consideredUDL = both considered

ThresholdsddeThresholdsLev (ERT) 0..63 dB Field drop suffered by signal to be exceededNx (ERN) 1..32 Number of single values taken for comparisonPx (ERP) 1..32 Number of single values which must exceed threshold

Deep drop edge windowddeWindow (ERMW) 1..32 Field drop is determined by comparing current

measurement n with measurement n - ddeWindow

Enhanced Rapid Field Drop HandoverParameters

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Handover

ddeWindow = 2 SACCH framesddeThresholdsLev = 20 dBpx = 2nx = 3

Serving cell

Adjacent cell

Field drop threshold 20 dB

ddeWindow

Handover triggered

-83 -87-63-61-60-60 -89 -91 -94 -89 -89

Field drop 1 3 22 24

px 1 2

nx 3 3

Enhanced Rapid Field Drop HandoverField Drop Detection

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Handover

Serving cell

Adjacent cell

Field drop threshold 20 dB

ddeWindow

Handover triggered

-83 -87-63-61-60-60 -89 -91 -94 -89 -89

averagingWindowSizeAdjCell = 4

modifiedAveWinNcell = 2

ErfdOver

Handover executed

Handover triggered -> modified averaging parameters for adjacent cell RX levels

modifiedAveWinNcell (ERAW) 1..32 SACCH frames Shorter averaging windowmodified NOZ (ERZ) 1..32 Modified number of allowed

zero resultserfdOver (EFD) 0..64 s New parameters valid until timer

expires

Field drop detection -> 5 SACCH frames

Handover execution -> 2 SACCH frames

Total -> 7 SACCH frames

Enhanced Rapid Field Drop HandoverHandover Speed Up

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MSC handover request

Ranking of adjacent cells only according RX level

Check of adjacent cells with condition 1a for

rxLevMinCell (SL) andtrhoTargetLevel (TRHO)

Adjacent cell with sufficient RX level

Yes No


Traffic Reason HandoverMSC Initiated

DeactivationtrhoTargetLevel = N

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Advanced Multilayer Handling

BSC Initiated Traffic Reason HO Relieve load on contested cell(s) Distribute load over the network If the traffic load of the serving cell exceeds a threshold, the different (smaller) power budget margin is used for all adjacent cells instead of the existing HO margin pbgt(PMRG).

Multilayer Load Control During low traffic hours, prevent the use of the microcellular layer by keeping MS in the macro layer (once they camp on it) Reduce unnecessary handover between layers

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Serving cell with load > amhUpperLoadThreshold

Ranking of adjacent cells only according RX level

Check of adjacent cells with condition 1a for trhoTargetLevel condition 2a for amhTrhoPbgtMargin

Adjacent cell with sufficient RX level / power budget load < amhMaxLoadOfTgtCell

Yes No

Power budget handover

Handover failurePower budget >=hoMarginPGBT

Power budget < hoMarginPGBT

Traffic reason handover

Must not be used together withMSC initiated handover

DeactivationamhTrhoPbgtMargin = N

Traffic Reason Handover (AMH)BSC Initiated

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Traffic Reason Handover (AMH)Parameters

ATPM255 dBmThe power budget margin used when the load of the cell exceeds the value defined with the AMH Upper Load Threshold (AUT).

-24...24 dBm, step 1 dBm

amhTrhoPbgtMargin

HOC

AMLNThe maximum traffic load in the adjacent cell that is allowed to be the target cell for a traffic reason handover (TRHO). MML NOTE: Range: 0...100 % and N default: N

N, 0...100 %, step 1 %

amhMaxLoadOfTgtCell

BTS

AUT80 %The upper threshold for the load of the base station. The parameter is used to trigger BSC-controlled traffic reason handovers.

0...100 %, step 1 %

amhUpperLoadThreshold

BSC

TGT30 sThe guard time after a BSC-controlled or an MSC-controlled TRHO, during which a handover back to the original cell is not allowed.

0...120 s, step 1 samhTrhoGuardTime

BSC

AML70 %The maximum traffic load in adjacent cell allowed for a target cell of traffic reason handover (TRHO).

0...100 %, step 1 %

amhMaxLoadOfTgtCell

BSC

TRHO0 dBmThe minimum signal level when a traffic reason handover is allowed to an adjacent cell.

-109...-47 dBm, step 1 dBmN = not in use

trhoTargetLevel

ADCE

BSC - MML Name

Default value

DescriptionRange And StepAbbreviated Name

MO Class

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If there is little traffic in serving cell, the following handovers are not allowed:- FMMS, DADL/B, Umbrella, fast moving MS support / MS speed detection

MS is kept in coverage layer

Multilayer Load Control (AMH)Parameters

ATCMNIndicates whether the Advanced Multilayer Handling is used with micro cells or dual band.

Y, NamhTrafficControlMCN

HOC

ALT20 %Defines the lower threshold for the load of the base station. The parameter is used to trigger advanced multilayer handling functionality with IUO and/or Dual Band/ microcell features.

0...100 %, step 1 %

amhLowerLoadThreshold

BSC

BSC - MML Name

Default value


MO Class

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Typically the GSM/EDGE cells can have four types of neighbouring cells: Operator's own GSM/EDGE cells Operator's own WCDMA cells GSM/EDGE cells of a roaming partner WCDMA cells of a roaming partnerIMSI Based Handover enables a control of handovers between networks of different operators: The mobile subscriber in a home or visited network can measure selectively only the cells

of specified PLMN areas (PLMN id) Making handovers to specified PLMNs The functionality is based on the international mobile subscriber identityMain benefits: The access of the partners subscribers can be limited to defined cells only maintaining

service preference to own subscribers The partners can prefer their own cells and thus optimize costs caused by network visits

IMSI based handover

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Authorised Networks (ANE) Group of network PLMN identifiers having similar access rights a subscriber has the same access rights to all networks of the Authorised Networks

Subscriber Group (SG) All subscribers of an operator, which are identified with the home PLMN code of IMSIWhen a mobile subscriber belongs to a Subscriber Group and its IMSI can be recognized: It is possible to make handovers to the Authorised Networks (ANE) (GSM/WCDMA) It is possible to prevent the handovers of unwanted subscribers

IMSI based handover

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ANE Lists & SGs: Allows to define that BSC performs handovers only to certain

cells Each SG is attached to a ANE List containing all network

PLMN identifiers of the allianceThe application software consists of two parts depending on which network type the handover is directed to: Support for GSM-GSM Handover Support for GSM-WCDMA Inter-System Handover

GSMOperator A

GSMOperator A

GSMOperator A

GSMOperator A

GSMOperator A

GSMOperator A

GSM/WCDMARoaming partner BGSM/WCDMA

Roaming partner B

GSMOperator A

GSMOperator A

WCDMAOperator AWCDMA

Operator A

IMSI based handover

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The GSM-GSM Handover can be used e.g. when: The host GSM operator offers GSM coverage in the same country for several competing

GSM operators The host GSM operator wants the BSS to prevent unnecessary HO attempts of its own

subscribers to the client operator's GSM network The client GSM operator wants to transfer own subscribers to its own network whenever

possible

= Host Operator A with GSM network

= Client GSM Operator B

= Client GSM Operator C

GSM (A)GSM (A)

GSM of AGSM of A GSM of BGSM of B GSM of AGSM of A

GSM (A)GSM (A) GSM (A)GSM (A) GSM (A)GSM (A) GSM (A)GSM (A)GSM (A)GSM (A)

GSM (B)GSM (B) GSM (B)GSM (B) GSM (B)GSM (B)

GSM (C)GSM (C) GSM (C)GSM (C) GSM (C)GSM (C) GSM (C)GSM (C)

GSM of AGSM of A GSM of AGSM of A GSM of AGSM of ASubs of A

GSM of AGSM of A GSM of CGSM of C GSM of AGSM of A

Subs of B

Subs of C

IMSI based handover

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The GSM-WCDMA Inter-System Handover can be e.g.: The host GSM operator wants to offer GSM coverage for several competing WCDMA operators The host GSM operator also has its own WCDMA network in the same country The host GSM operator wants to prevent handover attempts of its own subscribers from the GSM network to

other operator's WCDMA network(s) The host GSM operator wants to prevent handover attempts of other operator's subscribers from the GSM

network to its own WCDMA network

WCDMA (A)WCDMA (A)

GSM (A)GSM (A)

GSM of AGSM of A WCDMA of BWCDMA of B GSM of AGSM of A

WCDMA (A)WCDMA (A) WCDMA (A)WCDMA (A)WCDMA (A)WCDMA (A)

GSM (A)GSM (A) GSM (A)GSM (A) GSM (A)GSM (A) GSM (A)GSM (A)GSM (A)GSM (A)

WCDMA (B)WCDMA (B) WCDMA (B)WCDMA (B) WCDMA (B)WCDMA (B)

WCDMA (C)WCDMA (C) WCDMA (C)WCDMA (C) WCDMA (C)WCDMA (C) WCDMA (C)WCDMA (C)

GSM of AGSM of A WCDMA of AWCDMA of A GSM of AGSM of ASubs of A

GSM of AGSM of A WCDMA of CWCDMA of C GSM of AGSM of A

Subs of B

Subs of C

= Host Operator A with GSM and WCDMA networks

= Client WCDMA Operator B

= Client WCDMA Operator C

IMSI based handover

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Inter-system HO feature must be enabled when IMSI Based HO to WCDMA cell is performed The RNC orders the mobile station to start the periodical reporting of inter-system measurement results when an intersystem handover or cell re-selection is needed Support of Cell Global Identity: Own/alien PLMN parameters effect only in the case of IMSI Based HO to a GSM cell It is recommended not to use the feature at the same time with DFCA GSM-GSM functionality requires that active MSs (having an active CS connection) use the BCCH frequency list which is constructed from the adjacent GSM cells defined for the BTS or SEG

IMSI based handover

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The following features cant be used in the same cell where the IMSI Based HO to GSM is enabled: Undefined Adjacent Cell Measurement Channel Finder Measurement Statistical Support for Automated Planning Automated Planning EnhancementsRequired BTS are: UltraSite / Metrosite / Talk-family / Flexi EDGEAdditionally: 64k signalling links for assuring necessary signalling capacity The MSC sends IMSI always when it is availableThe IBHO is an application software and requires a valid licence in BSC

IMSI based handover

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IMSI based handoverParameters 1/3

IBWA0 (All)In the case of WCDMA handover whether one of the existing Authorised Networks is used for target cell selection or all neighbour WCDMA cells are permitted.

This parameter is used in a serving GSM cell when a mobile subscriber is anonymous and IMSI based GSM-WCDMA handovers are enabled in the serving GSM cell.

0...10, step 1

ibhoWcdmaCellsAnoMs

BSC

IBGA0 (All)In the case of intra-GSM handover: whether one of the existing Authorised Networks is used for target cell selection or if all neighbour GSM cells are permitted (value 0 = ALL)

This parameter is used in a serving GSM cell when a mobile subscriber is anonymous and IMSI based GSM-GSM handovers are enabled in the serving GSM cell.

0...10, step 1

ibhoGsmCellsAnoMs

BSC

BSC - MML Name

Default value

DescriptionRange And Step

Abbreviated Name

MO Class

If the status of IMSI based handover to GSM cell is active but the ISHO_SUPPORT_IN_BSC option is deactive, then all neighbour WCDMA RAN cells are permitted for all mobile subscribers

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IWENWith this parameter you define whether forbidden neighbour WCDMA cells are filtered out from mobile specific handover target cell lists or not.

The filtering is done based on IMSI information of a mobile, ANE and SG definitions.

If the filtering is enabled in the cell and the MS is anonymous for BSC, then the BSC level filtering parameter IBWA is used to define permitted neighbourWCDMA cells for the MS.

IMSI based handover to WCDMA cells is disabled (N), IMSI based handover to WCDMA cells is enabled (Y)

ibhoWcdmaEnabled

BTS

IGENWith this parameter you define whether forbidden neighbour GSM cells are filtered out from mobile specific handover target cell lists or not.

The filtering is done based on IMSI information of a mobile, ANE and SG definitions.

If the filtering is enabled in the cell and the MS is anonymous for BSC, then the BSC level filtering parameter IBGA is used to define permitted neighbourGSM cells for the MS.

IMSI based handover to GSM cells is disabled (N), IMSI based handover to GSM cells is enabled (Y)

ibhoGsmEnabled

BTS

BSC - MML Name

Default value


MO Class

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WANDefines whether all neighbour WCDMA cells are filtered out from mobile specific handover target cell lists or not.

Y = IMSI based handovers to neighbour WCDMA cells are allowed for the mobiles of the Subscriber GroupN = IMSI based handovers to neighbour WCDMA cells are not allowed for the mobiles of the Subscriber Group

Y, NwcdmaRanAccess

SG

NAMEA unique name for a Subscriber Group1...15 characterssgNameSG

SGA unique identifier number for a Subscriber Group1...128, step 1sgIdSG

ANEDefines the Authorised Networks which the Subscriber Group is using.

1...10, step 1relatedAneSG

HMNCWith this parameter you define Home Mobile Network Code of the Subscriber Group

2...3 characters (Range 0999)

homeMncSG

HMCCHome Mobile Country Code of the Subscriber Group1...3 characters(Range 0999)

homeMccSG

NAMEA unique name for a group of Authorised Networks1...15 charactersaneNameANE

ANEA unique identifier number for Authorised Networks.1...10, step 1aneIdANE

BSC - MML Name

Default value


MO Class

07 rn20107en14gln0 handover control and adjacencies

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