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GBC_005_E1_1
Handover and Power control
ZTE University
GSM-BSS Team
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Content
Handover
Power control
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Handover reasons
Handover: Hand-over is a process that transfers a MS
that is in setting up or busy status to a new traffic channel
Handover reasons
Weak signal
Bad quality
Severe interference
Large TA
Macro-micro handover
Better cell handover
Handover
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Types of handover
Intra-cell hand-over: hand-over occurs in the same cell.
Controlled independently by the BSC the cell attached to.
Inter-cell hand-over of the same BSC: involving by MSC is
not needed. Inter-BSC hand-over of same MSC: Before and after hand-
over, the two cells belong to different two BSCs which are
controlled by the same MSC. All the MSC and BSCs are
involved. Inter-MSCs hand-over: Before and after hand-over, the two
cells belong to different two MSCs. All the relevant MSCs
and BSCs are involved.
Handover
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Network overview
MSCBSC
BTS
MS
BSC Evaluation and Decision
of HO
MSC: routes the call to the other
MSC during Inter-MSC HO
BTS preprocess
measurements UL and DL
MS measures:
Signal Strength DL own cell
and neighboring cells, Quality
DL
Signal Strength of
Neignboring Cells
BTS measures:
Signal Strength UL, Quality
UL , TA
Handover
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Intra-cell handover signaling process
MSBTS BSC MSC
Meas RepMeas Res
Phy Context Req
Phy Contest Conf
Chan Act
Chan Act ACK
Assign Command
SABMEst Ind
UA
Assign CompleteHo Perform
Deact SACCH
RF Chan Release
RF Chan Rel ACK
Handover
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Inter-cell handover signaling process
DT1HO PERF
HO CMD
CH ACT
MEAS REP
RF CH REL ACK
RF CH REL
DIHO COM
EST IND
HO DET
CH ACT ACK
MS BTS1 BTS2 BSC MSC
MEAS RES
DRHO CMD
HO ACCESS
PHY INFO
SABM
UA
HO COM
Handover
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Handover layer
Cell layer is relative defined by operator
Not defined
Upper layer
Same layer
Lower layer
Handover target cell is sorted by
Priority
Traffic
Radio environment
Handover
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Measurement report
Period 480ms
MS downlink measurement report (carried by SACCH) :
Downlink RXLEV
Downlink RXQUAL(BER)Other adjacent cells downlink RXLEVless than 6,
designated by BA list)
Measurement report made by BTS
Uplink RXLEV
Uplink RXQUAL
TA
Interference strip
Handover
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Preprocess of measurement report
PROCESSING OF BTS MEASURED DATA
RXLEV_XXXXDL or UL
For each connection, at most 32 sampling data are retained and
the average of RX level is calculated out by BSS in each
SACCH period.
Adjacent cellsBCCH carrier receiving level RXLEV_NCELL(n)
For each connection and each cell, the most 32 sampling data
are stored by BSS to calculate out the adjacent cells BCCH
carrier receiving level.
Handover
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Power budgetPBGT)
PBGT(n)=(Min(MS_TXPWR_MAX,P)RXLEV_DLPWR_C_D) (Min(MS_TXPWR_MAX(n),P)RXLEV_NCELL(n))
Where
PWR_C_Dis the difference of cell-allowed downward maximum
power with actual power
MS_TXPWR_MAX(current traffic channel)
MS_TXPWR_MAX(n)(adjacent cell n traffic channel)
P is the maximum transmission power of MS
Handover
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Parameters in Handover judgement
PARAMETER FUNCTION
UpLevThNP upward level threshold
UpQualThNP upward quality thresholdDwLevThNP downward level threshold
DwQualThNP downward quality threshold
UpIntfThNP upward interference threshold
DwIntfThNP downward interference threshold
MsDistThNP distance thresholdsame unit with TA)HoMarginn Adjacent cells hand-over margin
Handover
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Threshold Comparison
1.Hand-over will occur if at least P out of N upward levels
are lower than UpLevTh.
2. Hand-over will occur if at least P out of N downwardlevels are lower than DwLevTh.
3. Hand-over will occur if at least P out of N upward levels
are higher than UpQualTh.
4. Hand-over will occur if at least P out of N downward
levels are higher than DwQualTh.
Handover
H d
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Threshold Comparison
5. Hand-over will occur if the latest P out of N upward
levels are higher than UpIntfTh and condition 3 is met at
the same time.
6. Hand-over will occur if the latest P out of N downwardlevels are higher than DwIntfTh and condition 4 is met at
the same time.
7. Hand-over will occur if the latest P out of N TAs are
higher than MsDistTh.
8. Hand-over will occur if PBGT of some adjacent cell is
higher than its corresponding HoMargin.
Handover
H d
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Selection of target cell
Principle 1 ( All type of handover )
AvRxLevNCell(n) > RXLEV_MIN(n) + MAX(0,(MS_TXPWR_MAX(n)-
P(n)))
Principle 2 ( PBGT handover )
PBGT(n ) > HO_MARGIN(n)
Principle 3 ( Quality handover )
AvRxLevNCell(n) > avRxLevDL + HO_MARGIN_QUAL(n)
Principle 4 ( Signal level handover )
AvRxLevNCell(n) > avRxLevDL + HO_MARGIN_LEVEL(n)
Handover
H d
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Sort order of target cell
Principle:
Cell dynamic priority
PBGT
Dynamic priority
Static priority: 07
Ratio of cell resource: idle TCH/ total TCH
Handover
H d
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Handover penalty strategy
Inter-cell handover
PenaltyLevOffset
PenaltyCount
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Content
Handover
Power control
Power control
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Purpose of power control
Lower interference within a cell
Save power
Consideration: Call quality or data transmission quality be
guaranteed
A B
Power control
Power control
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Power control procedure
Power
controlperiod:
480ms
MS
BTS
BSC
SACCH
MEASURED DATA
AVERAGE MEASURED DATA
POWER CONTROL DECISION
SEND POWER CONTROL COMMAND
MEASURED DATA CORRECTION
Power control
Power control
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Relation of level with power control
63
0
Upper limit
Lower limit
Fast power control
zone
Fast power control zone
High
Low
Normal
Power control
Power control
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Relation of BER with power control
0
7
Upper limit
Lower
limit
Fast power control
zone
Fast power control zone
Low
High
Normal
Power control
Power control
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Relationship between RXQUAL and BER
RXQUAL BER (%) Typical(%)
0 BER
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Power control strategy
Normal Level LEVELCAUSE = 0
Low Level LEVELCAUSE = 1
High Level LEVELCAUSE = 2
Normal BERQUALCAUSE = 0
Low BER QUALCAUSE = 1
High BER QUALCAUSE = 2
LEVELCAUSE QUALCAUSE OUTPUT
0 2 INCREASE
1 0 STAY
1 1 STAY
1 2 INCREASE2 0 DECREASE
2 1 DECREASE
2 2 INCREASE
Power control
Power control
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RANGE OF POWER CONTROL
BTS Power Control BTS has 6 classes of static power configured by network, each
class has 15 levels of dynamic power which can be configured bynetwork.
MS Power Control
GSM900 class A MS power capability 43dbm20W
GSM900 class B MS power control 39dbm8W
GSM900 class C MS power capability 37dbm5W
GSM900 class D MS power capability 33dbm2W
GSM900 class E MS power capability 29dbm0.8W
GSM900 power control range of MS is 43dbm ~ 5dbmat
least 2dbm one step
DCS1800 class A MS power control capability 30dbm1W
DCS1800 class B MS power control capability 24dbm0.25W
DCS1800 class C MS power control capability 36dbm4W
DCS1800 power control range 36dbm ~ 0dbm2dbm one step
Power control
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