S6-3 Handover
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Transcript of S6-3 Handover
1 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESS
2 © NOKIA 1999 ho.ppt/ July 2000 /
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
3 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESS
What is the purpose of HO?What is the purpose of HO?
Call continuityCall quality
Others...
Call continuityCall quality
Others...
4 © NOKIA 1999 ho.ppt/ July 2000 /
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
5 © NOKIA 1999 ho.ppt/ July 2000 /
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
6 © NOKIA 1999 ho.ppt/ July 2000 /
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)
7 © NOKIA 1999 ho.ppt/ July 2000 /
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
8 © NOKIA 1999 ho.ppt/ July 2000 /
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
9 © NOKIA 1999 ho.ppt/ July 2000 /
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
10 © NOKIA 1999 ho.ppt/ July 2000 /
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
11 © NOKIA 1999 ho.ppt/ July 2000 /
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)
12 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSHandover 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 … -47px 1 … 32nx 1 … 32
Parameter Value
rxLevMinCell(n) -110 … -47 dBmmsTxPwrMax(n) 5 … 43 dBmhoMarginLev(n) -24 … 24 dB
13 © NOKIA 1999 ho.ppt/ July 2000 /
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
14 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSHandover due to Quality (1/2)
• Trigger
Threshold Comparison ( hoThresholdsQualUL/DL (px - nx) )
• Candidate Selection
Equation 1 used
Equation 2 used if enableHoMarginLevQual = N
Equation 2' with hoMarginQual used if enableHoMarginLevQual = Y
Priority and Load Considered
hoThresholdQualUL/DL 0 … 7px 1 … 32nx 1 … 32
Parameter Value
rxLevMinCell(n) -110 … -47 dBmmsTxPwrMax(n) 5 … 43 dBmhoMarginQual(n) -24 … 24 dB
15 © NOKIA 1999 ho.ppt/ July 2000 /
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
16 © NOKIA 1999 ho.ppt/ July 2000 /
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) )
• 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 … -47px 1 … 32nx 1 … 32
enableIntraHoInterfUL/DL Y / N
Parameter Value
hoPreferenceOrderInterfUL/DL INTER / INTRABSC
17 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSHandover due to Interference (2/3)
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
18 © NOKIA 1999 ho.ppt/ July 2000 /
• 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
HANDOVER PROCESSHandover due to Interference (3/3)
19 © NOKIA 1999 ho.ppt/ July 2000 /
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 )
• Candidate Selection
Equation 1' used
Consistency between mobile classmark and target cell power constraints
Priority and Load Considered
• Multi-Layered Network
20 © NOKIA 1999 ho.ppt/ July 2000 /
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
21 © NOKIA 1999 ho.ppt/ July 2000 /
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
22 © NOKIA 1999 ho.ppt/ July 2000 /
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
23 © NOKIA 1999 ho.ppt/ July 2000 /
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)
24 © NOKIA 1999 ho.ppt/ July 2000 /
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
25 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSMS Speed
FMMS Example macrocells
microcells
measured signal strength
HO
hoLevelUmbrella = -85 dBm
RxMinCell = -95 dBm
FMT Counter
HO
FMT Threshold=40
time ‘t’
time ‘t’
26 © NOKIA 1999 ho.ppt/ July 2000 /
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’
27 © NOKIA 1999 ho.ppt/ July 2000 /
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
28 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSMS Speed : MS Speed Detection (2/3)
• 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
29 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSMS Speed : MS Speed Detection (3/3)
• 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
30 © NOKIA 1999 ho.ppt/ July 2000 /
HANDOVER PROCESSMS Speed
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)
31 © NOKIA 1999 ho.ppt/ July 2000 /
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
32 © NOKIA 1999 ho.ppt/ July 2000 /
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
33 © NOKIA 1999 ho.ppt/ July 2000 /
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)
• Candidate Selection
Only Chained adjacent cell
Equation 1 only / no priority
• Multi-Layered Network
Parameter Value
34 © NOKIA 1999 ho.ppt/ July 2000 /
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
35 © NOKIA 1999 ho.ppt/ July 2000 /
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
36 © NOKIA 1999 ho.ppt/ July 2000 /
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
37 © NOKIA 1999 ho.ppt/ July 2000 /
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
38 © NOKIA 1999 ho.ppt/ July 2000 /
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
39 © NOKIA 1999 ho.ppt/ July 2000 /
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
40 © NOKIA 1999 ho.ppt/ July 2000 /
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
41 © NOKIA 1999 ho.ppt/ July 2000 /
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
42 © NOKIA 1999 ho.ppt/ July 2000 /
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
43 © NOKIA 1999 ho.ppt/ July 2000 /
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
44 © NOKIA 1999 ho.ppt/ July 2000 /
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
45 © NOKIA 1999 ho.ppt/ July 2000 /
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
46 © NOKIA 1999 ho.ppt/ July 2000 /
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
47 © NOKIA 1999 ho.ppt/ July 2000 /
AMH 2 and AMH 3Parameters
Parameters Values
AmhTrafficControlIUO Y/N
AmhTrafficControlMCN Y/N
AmhLowerLoadThreshold 0…100%
48 © NOKIA 1999 ho.ppt/ July 2000 /
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
49 © NOKIA 1999 ho.ppt/ July 2000 /
• 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)
50 © NOKIA 1999 ho.ppt/ July 2000 /
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