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8/17/2019 GSM P&O Training Material for Special Subject-Handover Algorithms - ZTE
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GSM Handover Algorithms
----Special Subject Training V1.4
Suitable or sta !ith junior "#$ s%ill certiicates &lo!er than certiicate '''(
'ssued b) GSM *et!or% "lanning # $ptimi+ation ,ept.
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Internal Use Only▲
Version introduction
Version Date Writer Assessor Amendment record
V1.0 2007-07-25
Chen Chun Zheng Hao None
V1.4 2009-03-12
Fei Aiping Chang Haijie Explanaion o! "# i$ a%%e%.
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Training goals
Get to know theories and classification
of GSM handover;
Get to know the various kinds of ZTEhandover algoriths!
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ontents
$vervie! o handover
lo! o handovers
/asic handover algorithms
Advanced handover algorithms
'nter-s)stem handovers
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Aims o handovers
BTS
Servingcell
Neighbour cell AFreq. A
Neighbour cellBFreq. B
Neighbour cell CFreq. C
To ensure normal phone calls
To improve call quality
GSM handover belongs to system hard handover.
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Aims o handovers
Retrieval handover—to
retrieve the on-going calls;
Marginal handover—to
improve the on-going call;
Intra-cell handover—to
reduce interference in the
cell;
Forced handover—to balance traffic dispersion
in different cells;
Directed retry—to improvethe call establishment rate.
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Handover eatures
Various algorithms
•
Various algorithms can unction simultaneously;•Controlled by s!itches;•System ma"es handover decision automatically.
Ordering oftarget cells
•Static #riority;•$esource available%&';
•Budget #o!er value.
Automatic trafficbalance
•(irected retry;•)raic load handover started by MSC;•*riority ad+ustment by traic load;
•Force directed,shit handover; &&&
Fast-fading handoveralgorithm
Unique penaltymechanism
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Application scenes or handovers ' ' scenes (
Algorithms
Scenes
U"#$"
interferencehandover
U"#$"
%ualityhandover
U"#$"
levelhandover
"ong
MS&'Sdistancehandover
U"
fast&fadinghandover
Macro
&icrohandover
('GT
handover
Traffic
loadhandoverstarted)y MS*
*o&'**+
handover
,orced
traffic&shifthandover
(athloss-T.&)asedconcentrichandover
*I&)asedconcentrichandover
urban - - - - - - -
,enseurban
- - - - - - - - - -
suburb - - - -
)he table is or reerence only
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Application scenes or handovers '' ' net!or%t)pes (Algorithms
Scenes
U"#$"interfer
encehandover
U"#$"%uality
handover
U"#$"level
handover
"ongMS&'S
distancehandover
U"fast&
fadinghandover
Macr o&
icr ohandover
('GThandov
er
Trafficload
handoverstarted)yMS*
*o&'**+handover
,orcedtraffic&
shifthandover
(athloss-T.&)asedconcentrichandover
*I&)asedconcentrichandover
,ual-bandnet!or%
- - - - - - -
,ouble-la)ernet!or%
- - - - - - - -
$-/H - - - - - -
0ong-distancecoverage
- - - - -
)he table is or reerence only
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ontents
$vervie! o handover
lo! o handover
/asic handover algorithms
Advanced handover algorithms
'nter-s)stem handover
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Internal Use Only▲
$verall handover lo!
* r o c e s s
o
M $
(ecisiono
handover
start
Selectiono target
cells
/rderingo target
cells
Start ohandover
* e n a l t y
s t r a t e g y o r
h a n d o v e r
a i l u r e
/verall handover lo!/verall handover lo!
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hat is M23
0. (1 ()2 #erormance3. 41 receive level5quality6. BS *o!er7. MS #o!er level8. )A9. (1 dynamic #o!er control
41 M$
(1 M$ 0. 41 ()2 #erormance3. (1 receive level5quality6. Ad+acent cell level7. 41 dynamic #o!er control
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M2 c)cle
M/ is sent to 'TS in S.**+ U" direction; 0hen MS is in S$**+1 M/ cycle is 234s#tie;
0hen MS is in T*+1 M/ cycle is 254s#tie!
03)C:03)C: 03)C:03)C:0SACC:0SACC: 00 )*)*
7
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"rocess o M2
eatures
Number o M$shall reach the
average si=e o!indo!;
)he ma> numbero missing M$ is
?eroAllo!ed;
@hen #o!ercontrol is on
#o!ercom#ensationshall be made to
handover decisionthreshold.
Consider ()2!eight;
Measurement re#ort is the original data base or handover decision. ?2G0< #rocessado#ts roll average method !ith various !eights !hich can ensure smooth handover.
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The ma number o missing M2 - 5eroAllo!ed
Su66ose Zero.llowed78M216"21
Average7M21M286"28
Average7M28M296"29
M246"24
M2:6"2:
M2;6"2;
M2
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Handover preprocess at /TS
Su66ose +O(re6rocess is o6en and the value is 9!
M$0
M$3
M$6
M$7
BSC
"reprocess 2esult1
"reprocess 2esult8
:/*re#rocess
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"rocess o M2 at /S
Su66ose window value721 :72M216"21
Average7M21M286"28
Average7M28M296"29
Average7M29
M246"24
Average7M24
*6" decision
M2:6"2:
M2;6"2;
M2
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Selection o target cells
Handover
t)pes
'ntra-cell
handover
Macrocell normal T2@
Macrocell special T2@
$ther T2@ in microcell
'nter-cell
handover
1 / Av20ev*ell&n( 2@0BV7M'*&n( >MA@&?C&MS7T@"27MA@&n(- "&n(((
8 / "/GT&n ( H$7MA2G'*&n(
9 / Av20ev*ell&n( av20ev,0 >H$7MA2G'*70BVB0&n(
4 / Av20ev*ell&n( av20ev,0 >
H$7MA2G'*7DEA0&n(
condition 0 must be satisied
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Settings o cell la)er # priorit)
,unctions of cell layer structure More reasona)le control of traffic dis6ersion;
*ontrol of traffic congestion;
'acku6 of network ca6acity redundancy!
Serial :andover causes :andover ty#es *riority Ater Tmicro
/eore Tmicro
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Internal Use Only▲Serial :andover causes :andover ty#es *riority Ater Tmicro
overtimes/eore Tmicroovertimes
8 !-"# Intra&cell Invalid Invalid
9 $% interference Intra&cell Invalid Invalid
< D% interference Intra&cell Invalid Invalid
2 $% &uality Inter&cell 'ame layer- upper layer-lo(er layer
$pper layer ) same layer-lo(er layer
= D% &uality Inter&cell 'ame layer- upper layer-lo(er layer
$pper layer ) same layer-lo(er layer
> $% level Inter&cell 'ame layer- upper layer-lo(er layer
$pper layer ) same layer-lo(er layer
3 D% level Inter&cell 'ame layer- upper layer-lo(er layer $pper layer ) same layer-lo(er layer
5 %ong distance Inter&cell 'ame layer- upper layer-lo(er layer
$pper layer ) same layer-lo(er layer
? $% fast fading Inter&cell First search for related cells
$pper layer ) same layer
lo(er layer
Invalid
84 *"+, Inter&cell .ccording to
()gt+o"ayer
Sae layer& u66er layer
lower layer
:o cells on sae layerand lower layerselected
88 Macro-micro timehyteresis
Inter&cell +andover to lower layer :o handover
89 ,raffic Inter&cell .ccording toTraffic+o"ayr*tl Traffic+o,re *tl
Invalid
Algorithmsare related totheir layers
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"arameter-*cell0a)er
@:cell"ayerA is a atheatical array! Each eleent
deterines the layer relation )etween the serving cell and its
adBacent cells!
The nu)er of cells in an array rests on :cell:u!
*cell*um 1alue
"eaning
0 N un%e!ine%
1 A"E he $eing ell an% i$ a%jaen ell$ ae onhe $a6e lae
2 8E# a%jaen ell$ ae on he $eing ell:$ uplae
3 ;lae
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0a)er parameter-Tmicro
Ticro is started when
the MS accesses into
new channel;
The layer selection
6riority of target cells
will )e affected1 if
handover is started
within the tie set on
Ticro!
$efault 54@5sA!
Tmicro Time duration
:? :s
:1 :.1s
F F
8?? 8?s
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$rdering o target cells
0a)er priorit) o
candidate cells
Static
priorit)2esource
available&
(
"o!er budget
margin
,)namic
priorit)
,)namic
priorit)
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#andover decision
eecution
#andover failure/
'tart #oFail*enal,ime
*enalount01
compare the difference bet(een ad2acent cell3s
priority and the
acceptable priority
,he punished cell o(ns
the highest priority/
*enalount4*enalount5
6
7
7
7
omplete handover flo(
8
R%ev9n:4R%ev9n:-
*enalty%ev!ffset ?*enaltyount4*enaltyount56
8
8
#oFail*enal,ime
overtimes
'creen the target cell
Relieve the target cell
of penalty
7
N
*enalty strategy o inter,cell handover ailure
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,MaI#o overtimes
#andover decision
'tart intra-cell
handover/
'tart #oFail*enal,ime
I#oount4
7
7
!ther handover 8
I#oount4I#oount56 ?
,MaI#o4
I#oount4MaI#o
'top starting intra-cellhandover
I#oount4MaI#o
7
8
7
8
!ther handover
re&uirements are satisfied/
7
8
8
*enalty strategy o intra,cell handover ailure
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ontents
$vervie! o handover
lo! o handover
/asic handover algorithms
Advanced handover algorithms
'nter-s)stem handover
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E06,0 intererence handover
dle )C:available in cellD
dle )C:available in cellD
415(1intererence
handoverintra,cellhandover
415(1intererence
handoverintra,cellhandover
415(1 quality
:andoverinter,cellhandover
415(1 quality
:andoverinter,cellhandover
E
N
(ecision o handover start
9n:InterfF
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E06,0 ualit) handover
(ecision o handover startAv2DualE0=HoElDualThs
Av2Dual,0=Ho,lDualThs
Selection o target cells
1 / Av20ev*ell&n( 2@0BV7M'*&n( > MA@&?C&MS7T@"27MA@&n(- "&n(((
8 / Av20ev*ell&n( Av20ev,0 > H$7MA2G'*7DEA0&n(
)hat is0. Ad+acent cells level must be larger than the minimum receive level set or it;3. Ad+acent cells level shall be larger than the sum o quality handover
threshold and the serving cells (1 level.
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E06,0 level handover
(ecision o handover startAv20evelE0=IHoEl0evThs
Av20evel,0=I Ho,l0evThs
Selection o target cells
1 / Av20ev*ell&n( 2@0BV7M'*&n( > MA@&?C&MS7T@"27MA@&n(- "&n(((
8 / Av20ev*ell&n( Av20ev,0 > H$7MA2G'*70BVB0&n(
)hat is0. Ad+acent cells level must be larger than the minimum receive level set or it;3. Ad+acent cells level shall be larger than the sum o level handover threshold
and the serving cells (1 level.
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0ong /S-MS distance handover
(ecision o handover start
Av(istanceH(istance)hreshold%)A'
Selection o target cells
1 / Av20ev*ell&n( 2@0BV7M'*&n( > MA@&?C&MS7T@"27MA@&n(- "&n(((
)he only condition is that the ad+acent cells level is larger than the minimumreceive level set or it.
$adioenvironment
quality isnot
regarded asdecision
standard.
$adioenvironment
quality isnot
regarded asdecision
standard.
A##lication range
)his "ind o handover is usually used in net!or"s !ith long distance coverage.
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"/GT handover
(ecision o handover start
Selection o target cells
1 / AvRxLevNCell(n) > RXLEV_MIN(n) + MAX(0,(MS_TXPWR_MAX(n)- P(n)))
2 / PBGT(n ) > !_MARGIN(n) )hat is
0 / Ad+acent cells level shall be larger than the minimum receivelevel set or it; 3 / ts #o!er budget value shall be larger than the *BG)handover threshold set or ad+acent cell.
Ma"e handover decision to each ad+acent cell in rotation;!hen an ad+acent cells *BG) value is higher than
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,irected retr)-decision o handover start
M' applies for ,#
$sable ,#
available/=ssignment success
Force disconnetionB
force handover and
ordering attempt
'uccessful force
disconnetionB force
handover and ordering
Directed retrys(itch open or not
Directed retry
7es
successful
7es
8o
unsuccessful
,# occupancy failure
8o
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,irected retr) handover
It ha66ens in the 6rocess of calling access; It dynaically adBusts call traffic )etween cells;
It can lower call loss rate;
Selection of target cells ust fulfill condition 8!
Get to "no! the lo! ointernal I e>ternal directed retry
:o! to control356G handover #riorityD
ts suggested that ordering #rocess be o#ened irstsince its eect is better than that o directed retry.
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"enalt) on directed retr) ailure
No candidatecells ound
Start thededicated timer
Ater timere>#ires
/rdercandidate cells
:andoverE
N %NH6 ailure'
Failure dueto radio lin"
#roblem(elete the
attem#t cells
3ndcandidate cell
:andover
E
N %NH6 or )60#ires give u# directed retry'
Candidatecells have no
radioresources BSC e>ternal
cells
BSC internal
cells
3ndcandida
te cell
:andoverE
Com#lete
N
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ontents
$vervie! o handover
lo! o handover
/asic handover algorithms
Advanced handover algorithms
'nter-s)stem handover
O
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Internal Use Only▲
E0 ast ading handover
This is a kind of algorith for saving handover due to U" level
decrease; It is fleDi)ly used in dense ur)an areas1 like icro&cells1 highways1
corners and slo6es1 where in&tie outgoing handovers are needed;
Selection of target cell shall fulfill condition 8;
Given condition 8 is fulfilled1 handover to relevant cellsF is 6referred!
M216"21
M286"28
M296"29
M246"24
*umber o consecutive
handover decisions &*(
(irectlyre#ort M$ to
B)S
* unavailable @
I t l U O l ▲
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Macro-micro handover
Handover trigger conditionsJ measured values o adjacent
cellKs signal strength is higher than thresholdC and this
reaches certain consecutive times.
Selection o target cellJ
*ondition 8 is fulfilled; "ayer relation with neigh)or cell ' NcellLayer ( is
"ower!
Av20evE0&n(= MacroMicroHoThs
Macrocell
MicrocellMicroce
ll
Serving cellmacrocell
)arget cellmicrocell
),
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Traic handover
0hen the serving cell suffers fro congestion1 for MS which has
esta)lished a call1 'S* will hand it over to an adBacent cellwhich can fulfill traffic handover conditions!
Ad+ust call traic in dierent cells to reach traic balance.
(ecision o handover start TH/us)"ercentTraicThs
K>cluding congested )C:s;
$egardless dynamic :$ anddynamic *()C:.
Selection o target cell
Condition 0 PBGT(n) > TrafficLevThs
I t l U O l ▲
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MS-started traic load handover
ItCs started )y MS*; Select at ost :uOfMS calls;
+andover fro high loaded cells to low loaded ones!
nter,BSC load ad+ustment;No data coniguration needed at radio side.
Note*recondition or this handover algorithm MSC starts theunction and BSC su##orts load re#ort.
Currently no manuacturer ma"es this unction o#en. DDDDD
I t l U O l ▲
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orced directed-shit handover
eatures
The last eans to adBust traffic; Mainly used in *O&'**+ cells;
.66lica)le
scenes?44M8544M cell of the
sae direction;
Target cell ust )e
forced firected shift
handover cell!
Internal Use Only▲
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orced directed-shit handover strateg)
(ecision o handover start
"ath0oss&n(I=Ma0ossThs
TA&n(I=MaTAThs
Ma>)A)hs96 Ma>1oss)hs 08<
/nlybased
on*athloss
/nlybased
on)A
Selection o target cell
*BG) value must be larger than the dierence bet!een *BG)threshold and Ma>Force:o(i;
4sable resource in target cell must be larger than :oForce$es)hs;
)arget cell must be the one or dorced directed,shit handover.
Internal Use Only▲
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omparison bet!een orced directed-shit handover and
other t)pes o handover
ompared!ith "/GT
handover
Usually they are valid at the sae tie1 )ut ('GTs 6riority is higher
than that of forced directed&shift handover;
The MaD"ev$iff of forced directed&shift handover ust )e saller
than the value of reverse ('GT1 or (ing6ong handover will )e resulted!
ompared
!ithdirected
retr)
,orced directed&shift is the handover )etween two T*+s during call
6rocess;$irected retry is carried out when a66lying for T*+ during call
access!
ompared
!ith traic
handover
$ifferent trigger conditions @forced directed&shift handover is
triggered )y MS1 traffic handover is triggered )y 'S*!A
$ifferent handover flows!
Internal Use Only▲
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o-/H handover-subcell
)he irst subcell
)he second subcell
o-/H
Conigurationo subcell
Conigurationo subcell
arriers in different
fre&uency bands belong to
different subcells;
,he first subcell is
configured (ith "#.
o-channel cell
oncentric circle
advance technology;
'ubcells are allo(ed to
maCe po(er controlrespectively.
Internal Use Only▲
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o-/H handover trigger decision
(ecision o
handovertrigg
er
Based on#athloss
I)A
Based on C5
too small#athloss
I)A
too large#athloss
I)A
C5 good
C5 bad
*ath1ossL*ath1ossMin
And )AL SubCell)AMin
*ath1ossH *ath1ossMa>/r )AH SubCell)AMa>
C5H GoodCi)hs
C5L BadCi)hs
)hesecondsubcell
)heirst
subcell
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ontents
$vervie! o handover
lo! o handover
/asic handover algorithms
Advanced handover algorithms
'nter-s)stem handover
Internal Use Only▲
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$ptions o inter-s)stem &8G-EMTS6T,( handover strateg)
Han%o1e4 o
3A
p4e!e44e%
Han%o1e4 o 3A
N
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Internal Use Only▲
,escription o inter-s)stem &8G-EMTS6T,( handover strateg)
9G cell
preerre
d
8G cell
preerred
9G cell
inhibited
'nter-s)stem handover is inhibitedL handover algorithms are the
same as those o 8G.
6G handover decision
Valid decision Start 6G handover no more attem#t to 3G;
Null decision 3G handover decision I selection o target cell;
3G:andover decision
Valid decisionSaving handover
Null decision 6G handover decision I selection o target cell;
Select a 6G cell as candidate
try it i there is no usable radioresource available in 3G cell;
Non,saving handover 6G cells are not or candidates;
Internal Use Only▲
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Internal Use Only▲
DuestionsJ
(lease si6ly descri)e the relation )etween layer
and 6riority in handover algoriths;
(lease enuerate radio 6araeters of 9&
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