07) handover and power control

8/11/2019 07) Handover and Power Control

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ZTE University www.univ.zte.com.cnThe information contained in the file is solely property of ZTE corporation. Any kind of disclosing without permission is prohibited.


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OBJECTIVES

To understand the procedures of GSMHandover

To understand the procedures of PowerControl

To identify parameters needed forHandover and Power Control Operation


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HAND-OVER ANDPOWER CONTROL


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HAND-OVER


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PURPOSES OF HAND-OVER

1. Save the calls in progress bad quality)2. Cell-boundary handing over to improve

ongoing calls (weak signal)

3. Intra-cell hand-over reducing interferencewithin a cell (severe interference)

4. Compelled hand-over to balance traffic

distribution of inter-cells.


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NETWORK OVERVIEW

MSC BSC

BTSMS

BSC Evaluation and Decisionof HO

MSC: routes the call to the otherMSC during Inter-MSC HO

BTS preprocessmeasurements UL and DL

MS measures:

Signal Strength DL own celland neighboring cells, QualityDL

Signal Strength ofNeignboring Cells

BTS measures:

Signal Strength UL, QualityUL , TA


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1. Intra-cell hand-over: hand-over occurs in the samecell. Controlled independently by the BSC the cellattached to.

2. Inter-cell hand-over of the same BSC: involving byMSC is not needed.

3. Inter-BSC hand-over of same MSC: Before and afterhand-over, the two cells belong to different two BSCswhich are controlled by the same MSC. All the MSCand BSCs are involved.

4. Inter-MSCs hand-over: Before and after hand-over,the two cells belong to different two MSCs. All therelevant MSCs and BSCs are involved.

TYPES OF HANDOVER


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In this case, BSC should set up a new link with new BTS andassign a TCH in the new cell for MS.

HAND-OVER INSIDE BSCBSC

H/O

BTS OLD BTS NEW


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HAND-OVER BETWEEN DIFFERENTBSCs


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HANDOVER FLOWCHARTInter-BSC Handover

DT1 HO PERF

HO CMD

CH ACT

MEAS REP

RF CH REL ACK

RF CH REL

DI HO COM

EST IND

HO DET

CH ACT ACK

MS BTS1 BTS2 BSC MSC

MEAS RES

DR HO CMD

HO ACCESS

PHY INFO

SABM

UA

HO COM


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INTER-MSC HANDOVER

OLD LINK

NEW LINK

BSC OLD

H/OBSC NEW

MSC OLD MSC NEW

BTS OLD BTS NEW5

5

5

1

5

5

7

2

3

446

3

5

7


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INTER-MSC HANDOVERPROCEDURE (1)

1 BSCA sends hand-over request to MSCA whendeemed necessary according to MSs measurementreport.

2 MSCA sends this request to MSCB which is

responsible for setting up links with BSCB and BTSB.

3 MSCB sends back radio channel acknowledgement toMSCA.4 Communication links are established between MSCAand MSCB according to Hand-over Number(HON).

5 MSCA send hand-over command to MS who thenhanded over to a new TCH.


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INTER-MSC HANDOVERPROCEDURES (2)

6 BSCB send to MSCB, then to MSCA the commandof hand-over completion.

7 MSCA controls BSCA and BTSA to release the oldTCH.


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HANDOVER FLOWCHARTInter-MSC Handover


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HANDOVER CLASSIFICATION

1. Synchronous

2. Asynchronous

3. Pseudo-synchronous


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QUEUING AND FORCEDDISCONNECTION

Queuing - To increase the successful rate of hand-over,when no radio resource is available, the applicant of hand-over may be put into queuing and wait for release of radioresources.

Forced disconnection - when in emergency andno radio resource is available, some subscribers withlower priority may be disconnected, or handed out forcibly

to ensure that the subscribers with higher priority couldkeep their calls continuously.


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BASE STATION PRE-PROCESSING

1. RXLEV_XX XX DL or UL For each connection, at least 32 sampling data areretained and the average of RX level is calculated out by

BSS in each SACCH period.

2. Adjacent cells BCCH carrier receiving levelRXLEV_NCELL(n)

For each connection and each cell, the latest 32 samplingdata are stored by BSS to calculate out the adjacent cellsBCCH carrier receiving level.

PROCESSING OF BTS MEASURED DATA


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3. POWER BUDGET (PBGT)

For each connection and each allowable cell,

BSS calculates PBGT as follows


PBGT(n)=RxLevDL(n)-[RxLevDL(s)+BSTxPwrMax(s)-BSCurrentTxPwr(s)]


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4. Timing AdvanceFor each connection, BSS calculate the TA usingparameters Hreqt and Hreqave

5. Interference bandBSS averages interference on idle time-slots and

maps to five classes called strips.



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PARAMTERS IN CONNECTION WITHHAND-OVER

PARAMETER FUNCTION

UpLevTh N P upward level thresholdUpQualTh N P upward quality threshold

DwLevTh N P downward level thresholdDwQualTh N P downward quality thresholdUpIntfTh N P upward interference thresholdDwIntfTh N P downward interference thresholdMsDistTh N P distance threshold same unit with TA)HoMargin n Adjacent cells hand-over margin


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THRESHOLD COMPARISON

1. Hand-over will occur if at least P out of N upward levels arelower than UpLevTh.

2. Hand-over will occur if at least P out of N downward levelsare lower than DwLevTh.

3. Hand-over will occur if at least P out of N upward levels arehigher than UpQualTh.

4. Hand-over will occur if at least P out of N downward levelsare higher than DwQualTh.


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THRESHOLD COMPARISON

5. Hand-over will occur if the latest P out of N upward levelsare higher than UpIntfTh and condition 3 is met at the sametime.

6. Hand-over will occur if the latest P out of N downward levelsare higher than DwIntfTh and condition 4 is met at thesame time.

7. Hand-over will occur if the latest P out of N TAs are higherthan MsDistTh.

8. Hand-over will occur if PBGT of some adjacent cell is higher

than its corresponding HoMargin.


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HANDOVER ALGORITHM

The hand-over algorithm BSC adopts is based on the

following equation:

1) RXLEV_NCELL(n) > RXLEV_MIN(n) + Max (0, Pa)

where: Pa = (MS_TXPWR_MAX(n) P)

2) PBGT (n) - HO_MARGIN(n) > 0

BSS selects from all adjacent cells that both meets equation(1) and (2) and queue them from large PBGT to smallones and serves as candidate adjacent cells.


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POWER CONTROL


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POWER CONTROL PROCEDURES

MEASURED DATA

AVERAGE MEASURED DATA

POWER CONTROL DECISION

SEND POWER CONTROL

COMMAND

MEASURED DATA

CORRECTION


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RELATION OF LEVEL WITH POWERCONTROL

63

0

Upper limit

Lower limit

Fast power controlzone

Fast power control zone

High

Low

Normal


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RELATION OF BER WITH POWERCONTROL

0

7

Upper limit

Lowerlimit

Fast power controlzone

Fast power control zone

Low

High

Normal

C di R l i b


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Corresponding Relation betweenRXQUAL and BER

RXQUAL BER (%) Typical(%)0 BER


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BTS POWER CONTROLSTRATEGY

Keep current transmission power when received levelis normal.

Lower the transmission power when received level ishigh.

Increase the transmission power when received levelis low.

Keep current transmission power when BER is

normal. Increase the transmission power when BER is high.

Lower the transmission power when BER is low.


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MS POWER CONTROL STRATEGY

Normal Level LEVELCAUSE = 0

Low Level LEVELCAUSE = 1High Level LEVELCAUSE = 2

Normal BER QUALCAUSE = 0

Low BER QUALCAUSE = 1High BER QUALCAUSE = 2

LEVELCAUSE QUALCAUSE OUTPUT0 2 INCREASE1 0 STAY1 1 STAY1 2 INCREASE2 0 DECREASE2 1 DECREASE2 2 INCREASE


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RANGE OF POWER CONTROL 1 B T S Po w e r Co n t r o l

BTS has 6 classes of static power configured by network, each classhas 15 levels of dynamic power which can be configured bynetwork.

2 M S Po w e r Co n t r o l

GSM900 class A MS power capability 43dbm 20W

GSM900 class B MS power control 39dbm 8W GSM900 class C MS power capability 37dbm 5W GSM900 class D MS power capability 33dbm 2W GSM900 class E MS power capability 29dbm 0.8W GSM900 power control range of MS is 43dbm ~ 5dbm at least

2dbm one stepDCS1800 class A MS power control capability 30dbm 1W DCS1800 class B MS power control capability 24dbm 0.25W

DCS1800 class C MS power control capability 36dbm 4W DCS1800 power control range 36dbm ~ 0dbm 2dbm one step


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07) handover and power control

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