12 GSM BSS Network KPI (TCH Assignment Success Rate) Optimization Manual2.doc
05 GSM BSS Network KPI (TCH Congestion Rate) Optimization Manual.doc.doc
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
Product Name Confidentiality Level
G3BSC INTERNAL
Product Version Total 3 !a"es
GS# BSS Net$or% &PI 'TC( Con"estion Rate)
*!timi+ation #anual V,-.
'/or internal use only)
Prepared
by
GS#01#TS Net$or%
Performance Researc2
e!artment
42a
o &an"
Date 5..67.87
.
Reviewed
by
Date
Reviewed
by
Date
Approved
by
Date
(ua$ei Tec2nolo"ies Co-9 Ltd-
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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All ri"2ts reserved
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Contents
" einition o t*e TCH Congestion Rate#####################################################################################+
"#" einition########################################################################################################################+
"#, Re-ommen.e. /ormua##################################################################################################+
, Impa-ts o TCH Congestion Rate###############################################################################################0
1 Inuen-ing /a-tors o TCH Congestion Rate############################################################################2
1#" Network Capa-it3 an. Trai- istri4ution####################################################################2
1#, /auts O--urre. uring %5uipment Instaation6 Transmission6 or on Har.ware##########2
1#1 Network Intereren-e####################################################################################################"$
1#7 In-orre-t Parameter Settings#########################################################################################"$
1#8 Cooperation wit* T*ir.9part3 e:i-es#########################################################################""
1#+ Sotware !ersion Pro4em#############################################################################################""
7 &na3sis Pro-e.ure an. Optimization Met*o.#########################################################################""
7#" Network Capa-it3 an. Trai- istri4ution##################################################################",
-,-, Traffic Balancin"#############################################################################################",
-,-5 Traffic istri:ution Environment###################################################################"1
7#, /aut O--urre. uring %5uipment Instaation an. On Har.ware###############################"7
-5-, /eeder Installation and /ault########################################################################"7
-5-5 Board faults#####################################################################################################"+
-5-3 Transmission and Cloc% Pro:lem################################################################"0
7#1 Intereren-e Causes#######################################################################################################"0
-3-, Inter7Net$or% Interference############################################################################"0
-3-5 Im!ro!er /re;uency Plannin"######################################################################"0
7#7 KPI Measurement Pro4ems#########################################################################################";
7#8 Parameter Settings#########################################################################################################";
-<-, C2annel Assi"nment Parameters################################################################"2
-<-5 Call Control Parameters################################################################################,$
-<-3 (andover Parameters###################################################################################,"
-<- Basic Cell Parameters###################################################################################,,
7#+ T*ir.9Part3 e:i-e Pro4ems#######################################################################################,7
-8-, Re!eater Pro:lems########################################################################################,7
-8-5 Com!ati:ility $it2 Non7(ua$ei E;ui!ment################################################,7
-8-3 5G=3G Intero!era:ility###################################################################################,8
7#0 Sotware !ersion Pro4em############################################################################################,+
8 Test Met*o.###############################################################################################################################,0
+ &ppen.i< C*e-k Items on TCH Congestion Rate####################################################################,;
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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0 T3pi-a Cases#############################################################################################################################,;
0#" Case "= TCH Congestion Cause. 43 Terrain Reasons##################################################,;
0#, Case ,= Hig* TCH Congestion Rate Cause. 43 /aut o TR> Boar.##########################,2
0#1 Case 1= Stati- TCHH Congestion Cause. 43 Insui-ient TCH/s###############################,2
0#7 Case 7= In-rease o TCH Congestion Rate Cause. 43 Improper Ha9Rate Parameters
ater ?pgra.e rom BSC C"$ to BSC C"1###############################################################################1$
0#8 Case 8= In-rease o TCH Congestion Rate Cause. 43 Mo.ii-ation o eaut !aue
o Han.o:er T*res*o.#############################################################################################################1"
0#+ Case += In-rease o TCH Congestion Rate Cause. 43 Re:erse Conne-tions o
&ntennas####################################################################################################################################1,
0#0 Case 0= Hig* TCH Congestion Rate ue to No Capa-it3 %<pansion o Repeaters ater
BTS Capa-it3 %<pansion rom O, to O7#################################################################################1,
0#; Case ;= Intereren-e Cause. 43 Repeaters####################################################################11
0#2 Case 2= TCP Congestion Cause. 43 %<terna Intereren-e##########################################17
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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Revision Record
Date Revision Version Change Description Author
5..67.>75< V,-. raft com!leted 42ao
&an"
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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GSM BSS Network KPI (TCH Congestion Rate)
Optii!ation Man"a#
Ke$ words% TC( Con"estion Rate
&'stract% T2is document aims at reducin" t2e con"estion rate and im!rovin" t2e call
connection rate :y analy+in" t2e TC( con"estion rate in t2e traffic measurement of t2e
e?istin" net$or%-
&cron$s and a''reviations
&cron$ and&''reviation
"## Spe##ing
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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PreaceT2is document descri:es causes and im!acts of t2e TC( con"estion rate and !rovides
measures ta%en to reduce t2e con"estion rate and o!timi+e t2e &PI-
* +einition o t,e TCH Congestion Rate
,-, efinition
T2e TC( con"estion rate is t2e !ro!ortion of t2e num:er of TC( assi"nment failures to
t2e num:er of TC( sei+ure re;uests- If t2e TC( con"estion rate is 2i"29 t2e net$or%service ;uality deteriorates- In t2is case9 you can e?!and t2e ca!acity to reduce t2e TC(
con"estion rate-
,-5 Recommended /ormula
T2e TC( con"estion rate is o:tained from t2e traffic measurement result- T2e
recommended formula is t2e !ro!ortion of /ailed TC( Sei+ures due to Busy TC( to TC(
Sei+ure Re;uests- T2e formulas defined for t2e BSC35 and t2e BSC8... are as follo$s@
,- efined for t2e BSC35@ TC( Con"estion Rate 'All C2annels Busy) /ailed TC(
Sei+ures due to Busy TC( = TC( Sei+ure Re;uests ? ,..
5- efined for :y BSC8...@ TC( Con"estion Rate 'All C2annels Busy) TC( Sei+ure
Re;uests 'Si"nalin" C2annel) D TC( Sei+ure Re;uests 'Traffic C2annel) D TC(
Sei+ure Re;uests in TC( (andovers 'Traffic C2annel) F 'all t2e TRs in t2e cell)
Successful C2annel Assi"nments 'TC()H = TC( Sei+ure Re;uests 'Si"nalin"
C2annel) D TC( Sei+ure Re;uests 'Traffic C2annel) D TC( Sei+ure Re;uests in
TC( (andovers 'Traffic C2annel)H ? ,..H
Note@ /or t2e BSC8...9 t2e formula of calculatin" t2e con"estion rate on TC( !er BSC
is as follo$s@
Con"estion Rate on TC( !er BSC 'All C2annels Busy) /ailed TC( Sei+ures due to
Busy TC( !er BSC 'Si"nalin" C2annel) D /ailed TC( Sei+ures due to Busy TC( 'Traffic
C2annel) !er BSC D /ailed TC( Sei+ures in TC( (andovers due to Busy TC( !er BSC
'Traffic C2annel)H = TC( Sei+ure Re;uests !er BSC 'Si"nalin" C2annel) D TC( Sei+ure
Re;uests !er BSC 'Traffic C2annel) D TC( Sei+ure Re;uests in TC( (andovers !er BSC
'Traffic C2annel)H ? ,..
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ
- Ipacts o TCH Congestion Rate
T2e TC( con"estion rate is measured in t2e assi"nment and 2andover !rocedures- T2e
measurement !oints are A9 B9 and C- T2e follo$in" descri:es ne"ative im!acts :rou"2t
:y TC( con"estion in t2e !rocedures-
In t2e TC( assi"nment !rocedure9 t2e #S receives t2e Assi"nment Command messa"e
from t2e BSC at !oint A- If t2e TC( is con"ested9 t2e value of ai#ed TCH Sei!"res d"e
to B"s$ TCH increases :y one- T2en9 Iediate &ssignent S"ccess Rate is
decreased-
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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In assi"nment and 2andover !rocedures9 if t2e TC( con"estion leads to t2e TC(
assi"nment failure9 :ot2 t2e immediate assi"nment success rate and 2andover success
rate decrease- T2erefore9 reducin" t2e TC( con"estion rate o!timi+es t2e t$o counters-
Note
At !oint A9 B9 or C in t2e TC( assi"nment !rocedure9 if no TC( is idle9 ai#ed TCH
Sei!"res d"e to B"s$ TCH increases :y one-
At !oint B or C in t2e TC( assi"nment !rocedure9 if no TC( is idle9 :ot2 ai#ed
Incoing Interna# Inter.Ce## Handovers (d"e to '"s$ TCH) and ai#ed Incoing
/0terna# Inter.Ce## Handovers (d"e to '"s$ TCH) increase one-
1 In#"encing actors o TCH Congestion Rate
Accordin" to actual a!!lications and o!timi+ation e?!erience9 influencin" factors of t2e
TC( con"estion rate are as follo$s@
Net$or% ca!acity and traffic distri:ution
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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/aults occurred durin" e;ui!ment installation9 transmission9 or on t2e 2ard$are
Net$or% interference
&PI measurement !ro:lems
Incorrect !arameter settin"s
T2ird7!arty device !ro:lems
Soft$are version !ro:lems
3-, Net$or% Ca!acity and Traffic istri:ution
In t2e early !eriod of net$or% de!loyment9 t2e BTS !osition and t2e num:er of TRs are
desi"ned :ased on current #S distri:ution- T2e covera"e ca!a:ility of certain BTSs fails
to meet actual re;uirements due to c2an"es of traffic distri:ution- In t2is case9 it is difficult
to ma%e a call or t2ere are no si"nals-
*!erators and vendors must ta%e measures to reduce t2e TC( con"estion rate-
3-5 /aults *ccurred urin" E;ui!ment Installation9 Transmission9 or on
(ard$are
T2e traffic a:sor!tion is un:alanced in cells of an area :ecause of faults occurred durin"
e;ui!ment installation9 transmission or on t2e 2ard$are or cloc%- As a result9 TC(s in
certain cells are overloaded and in some cells are idle- T2erefore9 resources are $asted-
T2e cells controlled :y t2e BTS $or% a:normally due to t2e follo$in"s causes@
/eeders are installed reversely or dama"ed-
T2e TR :oard is faulty-
T2e BTS cloc% is faulty-
T2is increases t2e traffic of t2e nei"2:or cells and causes con"estion-
3-3 Net$or% Interference
Inter7net$or% interference or stron" intra7net$or% interference caused :y ti"2t fre;uency
reuse due to limited fre;uency resources affects t2e normal access of t2e #S9 causes
TC( assi"nment failure9 and increases t2e TC( con"estion rate-
T2e follo$in" ty!es of interference may occur@
,- Inter7net$or% interference from scram:lers or !rivately installed antennas
5- Interference from t2e C#A net$or% of C2ina 1nicom
3- Re!eater interference
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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- Intermodulation interference from BTSs
<- Intra7net$or% co7c2annel and adKacent7c2annel interference
3- Incorrect Parameter Settin"s
Parameter settin"s on t2e BSC and #SC affect t2e 2andover9 load9 c2annel assi"nment9
and cell con"estion- T2e follo$in" !arameters may cause ne"ative affects@
*2 TCH Traic B"s$ T,res,o#d(3) is incorrectly set-
-2 Tc, Traic B"s$ Over#a$ T,res,o#d and Tc, Traic B"s$ 4nder#a$ T,res,o#d
are incorrectly set-
12 &ssignent Ce## 5oad 6"dge /na'#e 'BSC8...) is invalid-
72 +irected Retr$ 5oad &ccess T,res,o#d is invalid-
82 Ba#ance Traic &##owed is not set-
92 5oad HO &##owed is not set-
:2 5oad HO Step Period is set to a too "reat value-
;2 R&CH Min2&ccess 5eve# is set to a too small value-
<2 Cell reselection !arameters are incorrectly set-
*=2 Ce## +irect Tr$ or'idden T,res,o#d 'BSC8...) is incorrectly set-
**2 +irect Retr$ is set to No2
*-2 S+CCH +$naic &d>"stent is invalid-
*12 /lo$ control !arameters are invalid-
*72 Speec, ?ersion is incorrectly set-
3-< Coo!eration $it2 T2ird7!arty evices
Some !ro:lems 'for e?am!le9 t2e 2andover or access is a:normal) may arise if t2ird7!arty devices are introduced suc2 as9 t2e ado!tion of re!eaters or se"mental net$or%in"
or in t2e :order areas of t2e local net$or%- T2ese !ro:lems cause a:normal &PIs 'for
e?am!le9 2andover success rate) and TC( con"estion-
3-8 Soft$are Version Pro:lem
2en t2e BSC is u!"raded or a ne$ version is used in t2e e?istin" net$or%9 t2e soft$are
of earlier versions may :e incom!ati:le $it2 t2e ne$ !latform 'for e?am!le9 BSC8...) or
soft$are :u"s may increase t2e TC( con"estion rate- T2erefore9 $e s2ould locate and
rectify t2e fault caused :y soft$are !ro:lems :y ta%in" !ro!er measures-
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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7 &na#$sis Proced"re and Optii!ation Met,od
Because reducin" t2e TC( con"estion rate involves a relatively lar"e sco!e9 $e canado!t t2e !rinci!le of first solvin" easy !ro:lems and t2en difficult !ro:lems- T2at is9
c2ec% t2e 2ard$are and soft$are to determine $2et2er t2e !ro:lem is common or
s!ecific- T2e !rocess is as follo$s@
C*e-k w*et*er t*ere are *ar.ware or
transmission aut aarms#
C*e-k w*et*er parametersare -orre-t3 set#
C*e-k settings o 4asi- -e parameters#
C*e-k settings o *an.o:er parameters#
C*e-k settings o -e oa. parameters#
C*e-k settings o -*anneassignment parameters#
C*e-k settings o un-tion
parameters#
So:e *ar.ware pro4ems an.-ear aarms#
T*e TCH -ongestion ratein-reases#
C*e-k w*et*er t*e trai- :oumee<-ee.s t*e .esigne. -apa-it3#
@es
Tra-e &4is9intera-e or &9intera-esignaing to o-ate -auses o TCHassignment aiure an. *an.o:er
aiure#
C*e-k w*et*er pro4ems areso:e.#
@es
No
@es
No
C*e-k w*et*er t*ere aresotware :ersion pro4ems#
'o-ate intereren-e -auses#
%<pan. t*e -apa-it3#
C*e-k t*e .istri4ution ointereren-e 4an.s#
@es
C*e-k w*et*er pro4ems o--ur ont*ir.9part3 e5uipment#
Coor.inate wit* t*e t*ir. part3#
@es
%n.
@es
No
&na3ze reate. trai-measurement -ounters#
No
No
No
No
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
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-, Net$or% Ca!acity and Traffic istri:ution
-,-, Traffic Balancin"
a"#t +escription and Ca"se &na#$sis
,- Common Cell
Radio traffic volume de!ends on t2e num:er of BTSs and cells in t2e net$or%9 t2e
num:er of radio c2annels confi"ured in eac2 cell9 and t2e covera"e of eac2 cell-
Currently9 c2annels are restricted :y desi"ned net$or% ca!acity- T2is is :ecause t2e
radio c2annel confi"uration and t2e covera"e is fi?ed as t2e num:er of BTSs and cells is
determined in t2e early !eriod of t2e net$or%9 2o$ever9 t2e deviation may e?ist :et$een
t2e actual net$or% ca!acity and t2e re;uired ca!acity- T2e TC( con"estion occurs in t2e
cells t2at re;uire "reater ca!acity- it2 city construction and economic develo!ment9
c2an"es of user density determined durin" t2e net$or% construction cause TC(
con"estion-
5- Concentric Cell
Concentric cells are introduced to solve traffic !ro:lems in t2e overlaid su:cell and solve
covera"e !ro:lems in t2e underlaid su:cell- (o$ever9 in actual a!!lications9 un:alanced
traffic distri:ution causes traffic im:alance in overlaid and underlaid su:cells- T2erefore9
t2e TC( con"estion rate in t2e overlaid su:cell is different from t2at in t2e underlaid
su:cell :ecause of t2e difference of t2e desi"n and actual a!!lication-
So#"tion
T2ere are t$o $ays to solve t2ese !ro:lems- T2e first met2od is to solve !ro:lemst2orou"2ly- T2at is9 conduct t2e detailed net$or% evaluation9 determine t2e cells $2ere
t2e TC( con"estion occurs9 and $or% out a detailed net$or% ca!acity e?!ansion solution
:ased on t2e con"estion severity- (o$ever9 $it2 city construction and furt2er economic
develo!ment9 t2e ca!acity e?!ansion is re;uired as t2e TC( con"estion reoccurs- In fact9
o!erators continually o!timi+e net$or%s $it2 t2e increase of su:scri:ers- T2e second
met2od is to o!timi+e net$or%s- T2ere are relatively idle cells in t2e net$or%- Mou can
decrease t2e TC( con"estion rate :y adKustin" TR confi"uration of t2e idle and :usy
cells- In addition9 you can ena:le t2e directed retry9 load 2andover9 and cell traffic
:alancin" functions- /or o!erators9 eac2 TR means ne$ investment- AdKustin" TR
confi"uration in a net$or% ma%es full use of net$or% ca!acity and o!timi+es t2e net$or%-
(o$ever9 t2e second met2od 2as certain limitations- If t2e actual used ca!acity is close
to t2e confi"ured ca!acity in terms of t2e total amount and ca!acity distri:ution9 you must
e?!and t2e net$or% ca!acity-
-,-5 Traffic istri:ution Environment
In actual a!!lications9 it is difficult for t2e #S t2at is located on t2e ed"e of t2e area
covered :y t2e BTS to ma%e a call due to $ea% level on t2e ed"e- T2is results in TC(
sei+ure failure and increases t2e TC( con"estion rate- 'Mou may as%@ oes t2is case
result in t2e increase of t2e TC( con"estion rate) Actually9 fe$er TC(s are sei+ed in t2is
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
BTS9 as s2o$n in t2e follo$in" fi"ure-
T2e follo$in" ta:le lists t2e TC( sei+ure counters in t2e traffic measurement result-
BSC 5eve# Ce## 5eve#
BSC #easurement 7O Access
measurement !er BSC 7O
TC( Availa:ility !er BSC
Confi"ured TC(s !er BSC
Availa:le TC(s !er BSC
&PI #easurement 7O
TC( Availa:ility
Availa:le TC(s
Confi"ured TC(s
TC( Con"estion Rate
TC( Traffic Volume
TR #easurement 7O
Num:er of confi"ured TRs in a cell
Num:er of availa:le TRs in a cell
So#"tion
AdKust t2e a+imut2 an"le or tilt of t2e antenna and set t2e static transmit !o$er of t2e
BTS to t2e ma?imum value- T2at is9 increase t2e si"nal stren"t2 in t2is area- In addition9
to decrease t2e TC( con"estion rate9 you can lo$er R&CH B"s$ T,res,o#d to ena:le
t2e #S to sei+e t2e TC( successfully- If t2ese met2ods do not ta%e effect9 de!loy ne$
BTSs near t2e user "rou!-
Case ,
-5 /ault *ccurred urin" E;ui!ment Installation and *n (ard$are
-5-, /eeder Installation and /ault
T2e TC( sei+ure failure may occur durin" t2e installation and confi"uration of feeders of
t2e BTS due to t2e follo$in" causes-
',) C1=SC1 confi"uration
/or e?am!le9 t2e C1DSC1 com:ination confi"uration is ado!ted in t2e cell $it2 four
TRs- T2e TR carryin" t2e BCC( sends si"nals to t2e antennas t2rou"2 t2e C19 and
ot2er TRs com:ine out!ut of si"nals t2rou"2 t2e SC1 and send t2e si"nals t2rou"2 t2e
C1- In t2is case9 t2e com:ination loss of BCC( "reatly differs from t2at of non7BCC(-T2erefore9 t2e transmit !o$er of BCC( is smaller t2an t2at of non7BCC(- If t2e BSC
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
assi"ns TC(s of t2e TR $2ere non7BCC( resides 'es!ecially far a$ay from t2e BTS)
$2en t2e #S ma%es a call9 t2e TC( may fail to :e si+ed :ecause of lo$ transmit !o$er
of t2e TR-
T2ere are t$o met2ods to solve t2is !ro:lem- *ne is to !ut t2e TR carryin" t2e BCC(on t2e c2annel !assin" t2e SC1- In t2is case9 t2e TR 2as smaller transmit !o$er and
TC(s of t2e TR $2ere non7BCC( resides can :e successfully assi"ned- T2e ot2er is to
modify t2e confi"uration- T2at is9 t2e dual C1 confi"uration instead of t2e C1DSC1
com:ination is ado!ted- T2is ensures t2e same !o$er consum!tion of c2annels $2ere
TRs reside and avoids t2e TC( sei+ure failure due to different transmit !o$er of TRs-
T2e second met2od is su!erior to t2e first one in terms of t2e !erformance :ecause t2e
loss of C1 is smaller t2an t2at of t2e SC1- T2is indicates t2at t2e second met2od
features relatively !ro!er covera"e distance- (o$ever9 t2e confi"uration cost is 2i"2er-
'5) Im!ro!er feeder installation
Reverse connections of antennas9 transmit antennas9 and receive antennas cause
serious si"nal im:alance on u!lin% and do$nlin% c2annels- T2at is9 t2e #S to $2ic2 t2e
transmit antenna !oints is :ac% of t2e receive antenna- If t2e #S receives t2e TC(
assi"nment command from t2e BSC durin" t2e call9 t2e TC( fails to :e assi"ned and t2e
TC( con"estion occurs due to !oor level and ;uality of u!lin% si"nals of t2e #S caused
:y small "ain of t2e receive antenna-
To solve t2is !ro:lem9 ma%e drive tests or use a si"nalin" analy+er to analy+e t2e level
and ;uality of u!lin% and do$nlin% si"nals to c2ec% $2et2er si"nal im:alance e?ists- If
yes9 ta%es !ro!er measures to solve t2is !ro:lem-
If t2e a+imut2 and tilt of t2e main antenna are inconsistent $it2 t2ose of t2e diversityantenna or t2e diversity or s!acin" is small $2en sin"le7!olari+ed antennas are used in a
cell9 u!lin% and do$nlin% si"nals are inconsistent and TC(s sei+ure failures tend to occur-
T2e solution to t2ese !ro:lems is t2e same as t2e !recedin" one- T2ese !ro:lems do not
e?ist in cells t2at ado!t dual7!olari+ed antennas-
Case 8
'3) /eeder fault
In t2e follo$in" cases 'suc2 as t2e feeder is dama"ed9 $ater runs into t2e feeder9 or t2e
feeder and t2e connector are not securely connected)9 t2e volta"e standin" $ave ratio
'VSR) increases and :ot2 t2e transmit !o$er and receiver sensitivity of t2e antenna
decrease- T2us9 t2e TC( assi"nment may fail9 causin" TC( con"estion-
To solve t2ese !ro:lems9 c2ec% $2et2er a VSR alarm is "enerated on t2e to$er
mounted am!lifier 'T#A)9 !o$er am!lifier9 com:iner9 and feeders- A rou"2 and sim!le
met2od is to use t2e test #S to test t2e actual transmit si"nals of t2e BTS on t2e foot of
t2e BTS- If si"nal stren"t2 ran"es from 3. dBm to <. dBm9 it indicates si"nals are too
$ea% and t2ere may :e !ro:lems-
If t2e antenna system 2as !ro:lems9 t2e TC( call dro! rate and 2andover failure rate are
2i"2- In addition9 t2e difference :et$een t2e u!lin% ;uality and t2e do$nlin% ;uality is
"reat9 or :ot2 t2e u!lin% ;uality and t2e do$nlin% ;uality are !oor- Mou can c2ec% $2et2er t2e antenna system is faulty :y vie$in" t2e traffic measurement results- T2e follo$in"
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
ta:le lists t2e traffic measurement counters related to t2e antenna system-
Ce## 5eve# TR@ 5eve#
Call #easurement 7O &PI #easurement 7O
Radio (andover Success Rate
Call #easurement 7O *ut"oin" Internal
Inter7Cell (andover #easurement !er Cell
7O
*ut"oin" E?ternal Inter7Cell (andover
Re;uests '1!lin% Stren"t2) 7O *ut"oin"
E?ternal Inter7Cell (andover Re;uests
'o$nlin% Stren"t2)
#R #easurement 7O
#easurement of Receive uality
#R #easurement 7O
1!lin%=o$nlin% Balance
Performance #easurement
If !ro:lems !ersist9 verify t2at remote BTSs are o!erational and conduct dialin" tests :y
!erformin" t2e follo$in" ste!s@
,- Perform local maintenance- C2ec% $2et2er alarms are "enerated- If yes9 clear t2ese
alarms immediately-
5- C2ec% $2et2er t2e u!lin% or do$nlin% antenna tri:utary 2as 2ard$are !ro:lems9 for
e?am!le9 t2e connector is loose9 antennas are reversely connected9 semi7ri"id ca:les are
connected incorrectly9 or ca:les are loosely connected to t2e :ac%!lane-
3- 1se t2e test #S to conduct dialin" tests on t2e same location-
Conduct dialin" tests on eac2 c2annel of eac2 TR to c2ec% $2et2er certain
timeslots or :oards cannot :e assi"ned-
C2ec% $2et2er t2e do$nlin% receive level of eac2 TR is similar- /or t2e TR $it2
a:normal level9 re!lace t2e :oard and u!lin% or do$nlin% antenna system to identify
t2e cause-
Note t2at if t2e cell ado!ts fre;uency 2o!!in" '/P)9 c2an"e t2e /( mode of t2e cell
to Non7/( :y usin" !arameters of t2e command line to facilitate dialin" tests-
- Conduct drivin" tests :y usin" t2e net$or% o!timi+ation soft$are ANT7PL*T- T2en9
c2ec% $2et2er t2ere are a:normal 2andover relations2i!s and do$nlin% interference and
find $ays to reduce t2e con"estion rate-
<- 1se a s!ectrum analy+er to furt2er locate t2e interference source-
8- C2ec% $2et2er t2e area covered :y t2e BTS features com!le? terrain-
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
-5-5 Board faults
/aults occurred on t2e TR :oard are t2e most ty!ical ones- T2ere is o:vious difference
:et$een t2e TC( sei+ure failure caused :y t2e :oard fault and t2at caused :y t2e feeder installation or fault- T2e former fault causes !oor c2annel availa:ility and t2e latter does
not affect t2e c2annel availa:ility-
T2e !ro:lem is easy to solve- 1se a si"nalin" analy+er to trace messa"e over t2e A:is
interface in t2e cell $it2 2i"2er TC( con"estion rate- T2en9 use t2e filter of t2e si"nalin"
analy+er to list t2e Assi"nment /ailure messa"e- In t2is messa"e9 t2e cause value is t2e
e;ui!ment failure- 1se t2e call trace function to list t2e entire messa"e !rocedure- /ind
t2e Assi"nment Command messa"e- T2en9 o!en t2e messa"e and o:tain t2e TR
num:er of t2e faulty TR :oard or #AI* 'of t2e /( c2annel)- T2erefore9 t2e fault is
concerned $it2 t2e TR- Mou can re!lace t2e TR or un:loc% t2e TR tem!orarily-
Case 5
-5-3 Transmission and Cloc% Pro:lem
Generally9 t2e u!!er7level cloc% is loc%ed :y t2e BTS- (o$ever9 due to o:Kective reasons
or malo!erations9 transmission !ro:lems suc2 as PC# out7of7sync2roni+ation of t2e A
interface9 intermittent LAP lin%s9 free oscillation and cloc% !ro:lems may occur- At t2is
time9 t2e TC( fails to :e sei+ed :y t2e #S9 causin" 2i"2er TC( con"estion rate-
To solve t2is !ro:lem9 c2ec% t2e alarm information and t2e status of t2e BTS cloc%
dis!layed on t2e L#T and determine $2et2er t2e transmission or t2e cloc% is faulty-T2en9 correctly set t2e status of t2e cloc% or contact related de!artment to rectify t2e
transmission fault-
-3 Interference Causes
-3-, Inter7Net$or% Interference
In t2e on7site de!loyment9 invalid inter7net$or% fre;uencies "enerate interference on our
net$or%- T2e interference affects t2e TC( sei+ure success rate9 call dro! rate9 and
2andover success rate- If t2e BSC assi"ns a TC( affected :y interference for a call9 t2e
assi"nment may fail and t2e TC( con"estion occurs-
/or inter7net$or% interference9 t2e traffic measurement s2o$s t2at t2e TC( con"estion
rate is 2i"2er in interference :ands four and five- T2e u!lin% interference is only for
reference- Eliminatin" t2e interference re;uires t2e coordination $it2 t2e local
"overnment- isa:le t2e affected fre;uencies- 1se t2e s!ectrum analy+er and 2i"27"ain
directional antenna to locate t2e interference source- T2en disa:le t2e interference
source- T2e inter7net$or% interference is difficult to analy+e- It is not descri:ed in detail
2ere-
Case Q
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
-3-5 Im!ro!er /re;uency Plannin"
In actual net$or%s9 fre;uency resources are limited- T2erefore9 fre;uencies must :e
reused to meet re;uirements of t2e net$or% ca!acity- /rom t2is !oint of vie$9 net$or%ca!acity is al$ays incom!ati:le $it2 net$or% !erformance- If t2e fre;uencies are
im!ro!erly !lanned9 t2e re;uirement for t2e carrier7to7interference ratios 'CIRs) fails to
meet and co7c2annel interference or adKacent7c2annel interference is "enerated- T2e co7
c2annel interference or adKacent7c2annel interference !roduces t2e same effect as t2e
inter7net$or% interference- T2at is9 t2e TC( assi"nment may fail and t2e TC( con"estion
occurs-
It is easier to analy+e and eliminate t2e interference caused :y im!ro!erly !lanned
fre;uencies- 1!lin% and do$nlin% fre;uencies are !aired- T2erefore9 $e can c2ec% t2e
information a:out interference :ands in t2e traffic measurement results- /irst9 find out t2e
cells $it2 2i"2 mean num:er of SCC(s in interference :ands four and five- T2en9 c2ec%
t2e fre;uency !lannin" and t2e to!olo"y of t2e BTS- /ind intra7fre;uency or inter7
fre;uency nei"2:or cells in o!!osite directions9 readKust t2e fre;uency !lannin"9 and
eliminate t2e interference- In addition9 if t2e antenna is installed reversely t2ou"2 t2e
fre;uency !lannin" is !ro!erly formulated9 interference is also "enerated- In t2is case9
you cannot solve t2is !ro:lem :y referrin" to t2e fre;uency !lannin" and net$or%
to!olo"y- T2erefore9 !erform a lar"e ;uantity of drive tests in t2e cells $it2 2i"2 mean
num:er of SCC(s in interference :ands four and five- C2ec% t2e actual distri:ution of
si"nals to determine $2et2er t2e interference e?ists- T2en9 modify t2e antenna !lannin"
or fre;uency !lannin"-
- &PI #easurement Pro:lems
T2ere are differences :et$een traffic measurement counters :ecause eac2 vendor
calculates t2ese counters :y usin" self7defined counters- It is difficult to find traffic
measurement !ro:lems causin" 2i"2 TC( con"estion rate- /or t2e BSC of earlier
versions9 t2e TC( sei+ure failure inde? 'numerator of t2e formula for calculatin" t2e TC(
con"estion rate) increases :y one if t2e Assi"nment Com!lete messa"e 'rat2er t2an t2e
Assi"nment /ailure messa"e) is not received after t2e BSC delivers t2e Assi"nment
Command messa"e- T2en9 a statistical error is "enerated9 and t2e calculated TC(
con"estion rate is 2i"2er t2an t2e actual rate-
T2is !ro:lem is com!le? :ecause a net$or% involves multi!le cells and TC( con"estion
occurs in many cells due to various causes@ suc2 as 2i"2 traffic or radio lin% failure 'due
to t2e !recedin" causes)9 includin" statistical errors- T2e ty!ical situation is t2at t2e call is
released once t2e #S initiates t2e call- T2e cause may :e t2at after re!ortin" t2e
isconnect messa"e9 t2e #S receives t2e Assi"nment Command messa"e from t2e
BSC9 and t2en re!orts t2e Status messa"e carryin" t2e cause value indicatin" messa"e
ty!e mismatc2- After receivin" t2e Status messa"e9 t2e #SC releases t2is call-
T2erefore9 neit2er t2e Assi"nment Com!lete messa"e nor t2e Assi"nment /ailure
messa"e e?ists in t2e messa"e !rocedure- /or t2e BSC of earlier versions9 t2e TC(
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
sei+ure failure counter increases :y one- T2ere are many cases in a lar"e GS# net$or%-
T2erefore9 t2e calculated TC( con"estion rate is 2i"2er t2an t2e actual rate- Currently9
t2e met2od of measurin" t2e TC( sei+ure failure is c2an"ed- T2e counter increases :y
one $2en t2e Assi"nment /ailure messa"e is received-/or t2e formula definition and recommended formula9 refer to t2e GSM BSS Network KPI
(TCH Call Drop Rate) Baseline-
-< Parameter Settin"s
Parameter settin"s may lead to t2e TC( con"estion due to various causes- Generally9
t2e !arameter settin"s may affect t2e TC( con"estion rate in all t2e cells in t2e entire
net$or% or certain cells- In t2e case of t2e former situation9 c2ec% $2et2er im!ortant
!arameters and t2en less im!ortant !arameters are correctly set :ecause of multi!le
cells involvin" t2e TC( con"estion and "reat on7site !ressure-
-<-, C2annel Assi"nment Parameters
TC( Traffic Busy T2res2old')H
/or (ua$ei c2annel assi"nment al"orit2m II9 $2en t2e TC( assi"nment rate reac2es or
e?ceeds t2e t2res2old9 t2e BSC assi"ns TC((s for t2e dual7rate call- *t2er$ise9 TC(/s
are assi"ned- *:viously9 t2is !arameter determines $2et2er TC((s or TC(/s are
assi"ned- T2erefore9 if t2e TC( con"estion rate is 2i"2er9 set t2e !arameter to a small
value to assi"n TC((s- T2is increases t2e c2annels usa"e ratio- (o$ever9 t2e s!eec2
;uality de"rades9 for e?am!le9 #*S tests may :e affected-
Tc2 Traffic Busy *verlay '1nderlay) T2res2oldH
T2e BSC assi"ns c2annels in t2e overlaid su:cell to t2e #S in a concentric cell- If t2e
c2annel sei+ure ratio of t2e overlaid su:cell is "reater t2an t2e value of t2is !arameter9
TC((s are assi"ned- *t2er$ise9 TC(/s are assi"ned- T2e im!acts of t2is !arameter are
t2e same as t2ose :rou"2t :y TCH Traic B"s$ T,res,o#d(3)9 t2at is9 c2annels are
utili+ed fully9 :ut t2e s!eec2 ;uality de"rades-
/i? A:is Prior C2oose A:is Load T2res2old')H
T2is !arameter s!ecifies t2e static A:is resource load t2res2old- 2en t2e static A:is
resource load is lo$er t2an t2e value of i0 &'is Prior C,oose &'is 5oad T,red(3)9
t2e TC(/ is !referentially assi"ned- *t2er$ise9 t2e TC(/ or TC(( is !referred
accordin" to t2e dynamic A:is resource load-
/le? A:is Prior C2oose A:is Load T2res2old')H
2en t2e static A:is resource load is 2i"2er t2an t2e value of i0 &'is Prior C,oose
&'is 5oad T,res,o#d(3) and t2e dynamic A:is resource load is 2i"2er t2an t2e value of
#e0 &'is Prior C,oose &'is 5oad T,res,o#d(3)9 t2e TC(( is !referred- *t2er$ise9
t2e TC(/ is !referred-
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
Balance Traffic Allo$edH
If t2is !arameter is set to A/S9 t2e start of t2e c2annel traverse is selected randomly- If
t2is !arameter is set to NO9 t2e ne?t c2annel of t2e assi"ned c2annel is selected as t2estart of t2e c2annel traverse-
Generally9 t2is !arameter is set to A/S to ensure t2at t2e start !oint of t2e c2annel
traversal is selected randomly and ensure t2e c2annel load s2arin"-
Case 3
-<-5 Call Control Parameters
Assi"nment Cell Load ud"e Ena:le 'BSC8...)H
2en &ssignent Ce## 5oad 6"dge /na'#ed is set to Aes9 t2e directed try !rocedure is
started if t2e follo$in" t$o conditions are met@ T2e cell su!!orts directed try- T2e load of
t2e cell is "reater t2an or e;ual to t2e value of Ce## +irect Tr$ or'idden T,res,o#d-
irected Retry Load Access T2res2old 'BSC8...)H
T2is !arameter is used to adKust candidate tar"et cells for directed retry-
urin" directed retry9 only t2e cells $2ose loads are smaller t2an or e;ual to t2e value of
+irected Retr$ 5oad &ccess T,res,o#d are selected as candidate tar"et cells-
If t2e !arameter value is too 2i"29 t2e cells $it2 2eavy loads are selected as candidate
tar"et cells so t2at t2e 2andover does not ma%e sense- If t2e value of t2e !arameter is
too lo$9 it is difficult to select candidate tar"et cells-
TC( Immediate Assi"nmentH
If t2e !arameter is set to Aes9 t2e BSC assi"ns TC(s immediately if no SCC(s are
availa:le durin" t2e !rocessin" of access re;uest- If t2e !arameter is set to No9 t2e BSC
can only assi"n SCC(s- T2is !arameter is used to relieve con"estion and increase t2e
c2annel assi"nment success rate-
Load (* Allo$edH
T2is !arameter s!ecifies $2et2er a traffic load7s2arin" 2andover is ena:led-Load s2arin" 2el!s to reduce cell con"estion9 increase success rate of c2annel
assi"nment and :alance t2e traffic load amon" cells9 t2us im!rovin" net$or%
!erformance- T2e load 2andover functions :et$een t2e TC(s $it2in one BSC or t2e
TC(s in t2e cells of t2e same layer-
T2e load 2andover is used as an emer"ency measure instead of a !rimary measure to adKust
a:normal traffic !ea% in certain areas- If load 2andovers occur fre;uently in a local net$or%9
you must adKust t2e TR confi"uration of t2e BTS and t2e net$or% layout-
Load (* Ste! Period and Load (* Ste! LevelH
2en t2e load of t2e cell is e;ual to or "reater t2an t2e value of 5oad HO T,res,o#d9 all
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
t2e calls served :y t2e cell may send 2andover re;uests simultaneously9 and t2e load on
t2e CP1 increases ra!idly as a conse;uence- In some cases9 call dro!s may occur due
to traffic con"estion in t2e cell- T2erefore9 t2e BSC ado!ts t2e 2ierarc2ical load 2andover
al"orit2m to control t2e num:er of calls to :e 2anded over at eac2 level-T2is !arameter s!ecifies t2e !eriod re;uired for !erformin" t2e load 2andover at a level-
In t2e 2ierarc2ical load 2andover9 t2e load 2andover stri! increases :y one 5oad HO
Step 5eve# for every 5oad HO Step Period9 startin" from t2e value of /dge HO +5
R@5/? T,res,o#d- T2e 2andovers are !erformed as suc2 until all t2e calls $2ose
receive levels are $it2in t2e ran"e of 'Ed"e (* L RJLEV T2res2old9 Ed"e (* L
RJLEV T2res2old D Load (* :and$idt2) are 2anded off t2e current servin" cell-
T2e value of 5oad HO Step 5eve# must :e smaller t2an t2at of 5oad HO Bandwidt,-
.83 corres!onds to ,,. dBm to > dBm-
irect Retry and Cell irect Try /or:idden T2res2old 'BSC8...)H
If &ssignent Ce## 5oad 6"dge /na'#e is set to Aes9 t2e directed try !rocedure is
started to assi"n c2annels for t2e #S if t2e follo$in" t$o conditions are met@ T2e cell
su!!orts t2e directed try !rocedure- T2e load of t2e cell is "reater t2an or e;ual to t2e
value of Ce## +irect Tr$ or'idden T,res,o#d- T2is !arameter decreases TC(
accesses of t2e source cell and reduces TC( con"estion t2rou"2 increases t2e call dro!
rate-
A#R TC(=( Prior Allo$edH
T2is !arameter s!ecifies $2et2er TC((s are !referentially assi"ned on t2e :asis of t2ec2annel ty!e and current service c2annel sei+ure ratio t2at are allo$ed :y t2e #SC-
urin" TC( assi"nment9 TC(/s or TC((s are re;uired and TC((s are !referentially in
t2e follo$in" conditions@ TC((s and TC(/s are allo$ed to :e assi"ned :y t2e #SC9
&MR TCHH Prior &##owed is set to Aes9 and t2e !ercenta"e of sei+ed TC(s in t2e cell
is "reater t2an t2e value of &MR TCHH Prior Ce## 5oad T,res,o#d- In ot2er cases9
TC(/s or TC((s are re;uired and TC(/s are !referentially-
-<-3 (andover Parameters
PBGT (* T2res2oldH
2en t2e 2andover is !erformed :et$een nei"2:or cells9 im!ro!er !arameter settin"s
cause out"oin" inter7cell 2andover or incomin" inter7cell 2andover to fail- T2is leads to
un:alanced traffic distri:ution and con"estion-
Parameters related to ed"e 2andoverH
2en t2e receive level dro!s "reatly9 an ed"e 2andover cannot :e !erformed in time in
any of t2e follo$in" conditions@ T2e !arameter /dge HO 45 R@5/? T,res,o#d or
/dge HO +5 R@5/? T,res,o#d is set to a small value t2e !arameter Inter.ce## HO
H$steresis is set to a "reat value t2e !arameters /dge HO Datc, Tie and /dge HO
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
?a#id Tie are set to "reat values- As a result9 con"estion occurs- To reduce t2e TC(
con"estion rate9 you can a!!ro!riately set t2ese !arameters so t2at ed"e 2andovers can
:e !erformed in time-
Parameters related to B 2andoverH
2en t2e si"nal ;uality deteriorates9 a B 2andover cannot :e !erformed in time in any
of t2e follo$in" conditions@ T2e !arameters 45 E"a#it$ 5iit or /ergenc$ Handover
(&MR&MRR&MRHR) and +5 E"a#it$ 5iit or /ergenc$ Handover
(&MR&MRR&MRHR) are set to "reat values t2e !arameter BE HO Margin is set to a
small value t2e !arameter Inter.ce## HO H$steresis is set to a "reat value- As a result9
call dro!s occur- To reduce t2e TC( con"estion rate9 you can a!!ro!riately set t2ese
!arameters so t2at B 2andovers can :e !erformed in time-
Parameters related to interference 2andoverH
If t2e !arameters R@E4&5* to R@E4&5*- are set to "reat values or if t2e R@5/?O
!arameter is set to a "reat value9 interference 2andovers cannot :e !erformed in time
$2en stron" interference occurs- As a result9 t2e con"estion occurs- To reduce t2e TC(
con"estion rate9 you can a!!ro!riately set t2ese !arameters so t2at interference
2andovers can :e !erformed in time to !revent con"estion- If t2e !arameters R@E4&5*
to R@E4&5*- are set to small values9 t2e num:er of 2andovers due to ot2er causes
increases "reatly9 t2us affectin" t2e 2andover success rate-
T3,.3 and T3,.>HT3,.3 and T3,.> are timers for t2e 2andover and assi"nment res!ectively- If eit2er timer
is set to a "reat value9 t2e time for $aitin" t2e 2andover=assi"nment com!lete messa"e
is too lon" after t2e 2andover=assi"nment command is delivered9 causin" con"estion-
/5( (* t2= (5/ (* t2H
2en an A#R call occu!ies a TC((9 an intra7cell TC(( to TC(/ 2andover is tri""ered if
t2e radio ;uality indication 'RI) remains lo$er t2an t2e confi"ured (5/ (* T2res2old
for a !redefined !eriod- T2is !arameter is used $it2 Intrace## .H HO Stat Tie (s) and
Intrace## .H HO 5ast Tie (s)-
Parameters related to concentric cell 2andoverH
A call at t2e ed"e of t2e overlaid su:cell cannot :e 2anded over to t2e underlaid su:cell
in any of t2e follo$in" conditions@ /or a normal concentric cell9 t2e !arameters R@5/?
T,res,o#d and R@5/? H$steresis are set to "reat values for an en2anced concentric
cell9 t2e !arameter Oto4 HO Received 5eve# T,res,o#d is set to a "reat value- As a
result9 TC( con"estion occurs- If t2e TC( con"estion rate in t2e overlaid su:cell is 2i"29
you can a!!ro!riately set t2ese !arameters so t2at calls at t2e ed"e of t2e overlaid
su:cell can :e 2anded over to t2e underlaid su:cell in time-
If R@E4&5 or 4O HO &##owed is set to Aes and R@E4&5 T,res,o#d is set to a"reat value9 a call in t2e case of interference cannot :e 2anded over from t2e underlaid
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
su:cell to t2e overlaid su:cell- T2us9 TC( con"estion occurs- If t2e TC( con"estion rate
in t2e underlaid su:cell is 2i"29 you can set t2ese !arameters !ro!erly so t2at t2e
interfered calls can :e 2anded over to t2e overlaid su:cell in time-
Case <
-<- Basic Cell Parameters
RLEVJACCESSJ#INH
T2is !arameter s!ecifies t2e minimum receive level of an #S to access t2e BSS- If t2is
!arameter is set to a too small value9 some #Ss $it2 lo$ receive levels may access t2e
net$or% and TC( con"estion is li%ely to occur- Mou can set t2is !arameter to a "reat
value to reduce t2e TC( con"estion rate- T2e counters suc2 as call setu! success rate
and t2e counters related to traffic volume9 2o$ever9 are accordin"ly affected-
SACC( #ulti7/rames and Radio Lin% TimeoutH
If t2e traffic volume is very 2eavy 'in cities)9 it is recommended t2at t2e value of S&CCH
M"#ti.raes ran"es from 5. to 35- In t2e areas $2ere t2e traffic volume is very 2eavy
'"enerally covered :y micro cells)9 it is recommended t2at t2is !arameter value ran"es
from to ,8- In t2e cells $2ere some areas are not covered or call dro!s occur fre;uently9
t2is !arameter must :e set to a lar"er value so t2at conversations can resume- T2erefore9 if
t2e !arameter is im!ro!erly set durin" 2eavy traffic volume9 t2e TC( con"estion is li%ely to
occur-
RAC( #in Access LevelH
T2is !arameter s!ecifies t2e level t2res2old for t2e #S access- If t2is !arameter is set to
a too small value9 some #Ss $it2 lo$ si"nal levels may access t2e net$or% and TC(
con"estion is li%ely to occur- Mou can set t2is !arameter to a "reat value to reduce t2e
TC( con"estion rate- T2e counters suc2 as call setu! success rate and !a"in" success
rate9 2o$ever9 are affected-
Parameters related to cell reselection
Im!ro!er settin"s of cell reselection !arameters affect t2e selection of t2e net$or% on$2ic2 t2e #S cam!s durin" cell reselection9 for e?am!le9 im!ro!er !arameter settin"s
durin" t2e dual7net$or% covera"e affect net$or% selection and cause TC( con"estion-
SCC( ynamic AdKustmentH
2en t2ere is a su:stantial user increase in a cell9 some users may not :e a:le to
access t2e net$or% :ecause t2ey cannot o:tain SCC(s- In t2is case9 you need to
convert some TC(s to SCC(s to ensure t2at all t2e users can access t2e net$or%-
2en t2e traffic volume decreases9 t2e TC(s used as SCC(s are converted :ac% to
TC(s- T2e dynamic conversion of SCC(s can increase t2e system ca!acity and lo$er
t2e re;uirement for t2e accurate num:er of re;uired si"nalin" c2annels-
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
/lo$ ControlH
T2ere are multi!le flo$ control !arameters- To relieve TC( con"estion9 t2e system starts
t2e flo$ control- (o$ever9 t2is affects TC( access and cause messa"e loss-
S!eec2 VersionH
T2is !arameter can :e set to one of t2e follo$in" values@ 2alf7rate version 39 2alf7rate
version 59 2alf7rate version ,9 full7rate version 39 full7rate version 59 and full7rate version ,-
If t2is !arameter does not su!!ort 2alf7rate versions9 t2e BSC assi"ns TC(/s instead of
TC((s- As a result9 TC( con"estion occurs-
-8 T2ird7Party evice Pro:lems
-8-, Re!eater Pro:lems
Currently9 re!eaters '/( re!eaters or o!tical re!eaters) are ado!ted to solve t2e !ro:lem
of insufficient indoor covera"e- It is difficult for /( re!eaters to o:tain si"nal resources-
T2e im!lementation !rinci!le of t2e /( re!eaters is t2at t2e /( re!eater am!lifies si"nals
received :y t2e main antenna of t2e o!tical re!eater and transmits t2ese am!lified
si"nals to t2e areas $it2 !oor covera"e- In ot2er $ords9 t2e covera"e of t2e cell is
e?!anded- T2erefore9 t2e traffic volume increases- If t2e traffic volume e?ceeds t2e
system ca!acity9 t2e TC( con"estion rate increases-
C2ec% $2et2er t2e !arameter +irect#$ Magniier Site #ag is set to Aes in t2e data
confi"uration on t2e L#T- If t2is !arameter is set to Aes9 you can infer t2at t2e cell is
confi"ured $it2 re!eaters- If t2is !arameter is set to No9 c2ec% $2et2er ot2er o!erators
re!eaters are installed near t2e cell-
If re!eaters are installed9 c2ec% $2et2er t2ey are $ide7fre;uency re!eaters- If yes9 c2ec%
$2et2er t2e u!lin%=do$nlin% am!lification coefficient is too "reat- Ensure t2at t2e
am!lification coefficient is !ro!erly set- If a re!eater 2as a "reat im!act on t2e call dro!
rate9 s$itc2 off t2e re!eater-
If re!eater !ro:lems e?ist in a cell9 t2e TA distri:ution varies "reatly in t2e traffic
measurement results- T2e follo$in" ta:le lists t2e traffic measurement counters related to
re!eaters-
Ce## 5eve# TR@ 5eve#
None #R #easurement 7O
Num:er of #Rs Based on TA
Case >
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
-8-5 Com!ati:ility $it2 Non7(ua$ei E;ui!ment
In t2e e?istin" net$or%9 t2ere are certain overla!!ed areas9 for e?am!le9 :oundary
:et$een t$o !rovinces and rural7ur:an frin"e +one covered :y e;ui!ment of differentvendors :ut t2e same o!erator- Coo!eration of e;ui!ment from different vendors re;uires
t2e inter7#SN 2andover- ifferent !olicies or !arameter settin"s may cause t2e traffic to
increase :ut fail to :e 2anded over immediately- As a result9 t2e TC( con"estion rate
increases-
If t2e !ro:lem occurs9 c2ec% t2e success rate of out"oin" BSC 2andovers and
distri:ution of out"oin" 2andover failure causes to identify t2e main causes- T2e follo$in"
ta:le s2o$s related traffic measurement counters-
Ce## 5eve# TR@ 5eve#
None Call #easurement 7O
*ut"oin" E?ternal Inter7Cell (andover
#easurement !er Cell
-8-3 5G=3G Intero!era:ility
it2 t2e develo!ment of 3G net$or%s9 certain 2i"27end #Ss ado!ts t2e dual transfer mode- T2erefore9 t2e #Ss can :e reselected from 5G net$or%s to 3G net$or%s and
5G=3G Intero!era:ility e?ists- it2 t2e increase of suc2 #Ss9 t2e con"estion may occur
in t2e 5G and 3G systems if !arameters are incorrectly set-
/or e?am!le9 normally9 an #S in t2e 5G net$or% is reselected to t2e 3G net$or%-
(o$ever9 nei"2:or cells in t2e Q..#7net$or% and 3G net$or% are set to unidirectional
adKacent cells- T2erefore9 t2e #S is reselected to t2e 5G net$or% rat2er t2an t2e 3G
net$or%9 causin" con"estion in t2e 5G net$or%-
5G=3G Intero!era:ility !ro:lems increase $it2 t2e develo!ment of 3G net$or%s- T2e
3GPP !rotocols s!ecify 5G=3G 2andovers of RQQ and later versions rat2er t2an
2andovers of earlier versions- T2erefore9 if !ro:lems occur9 c2ec% $2et2er t2e 2andover
is limited :y t2e version9 and t2en c2ec% t2e 2andover9 reselection9 confi"uration of
nei"2:or cells9 and !arameter settin"s to locate t2e !ro:lem-
/or !arameter settin"s9 refer to t2ose related to reselection9 2andover9 and 3G e?ternal
cells-
Note@ Currently9 t2e BSC8... su!!orts 5G7to73G inter7RAT 2andovers suc2 as TA emer"ency 2andover9
B emer"ency 2andover9 ra!id level dro! 2andover9 interference 2andover9 and ed"e 2andover-
Currently9 t2e BSC8... does not su!!ort t2e GS#7to7T7SC#A al"orit2m for t2e inter7RAT load7
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GSM BSS Network KPI (TCH Congestion Rate) Optimization Manua!"#$
INT%RN&'
:ased 2andovers and service7:ased 2andovers- (o$ever9 inter7RAT 2andovers :ased on certain
conditions can :e reali+ed in later versions-
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
-> Soft$are Version Pro:lem
Recently9 (ua$ei re;uires to im!lement multi!le mi"ration and u!"rade !roKects in t2e
5G net$or%- urin" t2e mi"ration9 early !roducts of (ua$ei re;uirin" to :e re!laced suc2
as BTSs of earlier version de!loyed on t2e BSC35 may :e incom!ati:le $it2 t2e
BSC8...- As a result t2e TC( con"estion rate increases or ot2er suc2 !ro:lems occur-
Solution
,- Mou re;uire to devote more ener"ies to analy+e suc2 !ro:lems- It is recommended
to c2ec% t2e !recaution9 find !ossi:le !ro:lems :efore t2e u!"rade9 and analy+e
cases to o:tain t2e solution and !rocessin" mec2anism ado!ted in t2e old version-
5- *n t2e remote L#T9 c2ec% $2et2er soft$are of eac2 :oard of t2e BTS is com!ati:le
and !erform version u!"rade accordin" to t2e version notice on t2e
2tt!@==su!!ort-2ua$ei-com site- *n t2e remote L#T9 :loc% TC(s of t2e TR :oard in
turn in t2e cell $it2 2i"2 con"estion rate- T2en9 c2ec% $2et2er t2e con"estion rate is
relevant to t2e TR :oard of t2e cell and t2en ado!t t2e follo$in" !rinci!les-
If yes9 it indicates t2at t2e con"estion rate is concerned $it2 t2e TR :oard-
C2ec% $2et2er co7c2annel interference e?ists9 and t2en c2ec% t2e !erformance
of u!lin% and do$nlin% 2ard$are and t2e TR :oard-
If not9 t2e interference e?ists in t2e entire cell or t2e con"estion rate is su:Kect to
t2e terrain-
3- Si"nalin" tracin" and analysis
1se a si"nalin" analy+er to trace messa"es over t2e A:is interface in t2e cell $it2 2i"2
con"estion rate- T2en9 com!are tracin" results $it2 measurement items in t2e call
!rocedure and measurement counters relatin" to t2e TC( assi"nment failure- T2e
follo$in" fi"ure dis!lays t2e messa"e tracin" results :y usin" t2e #A,. si"nalin"
analy+er-
C2ec%in" t2e &ssignent CM+ command delivered on t2e SCC(9 you can see t2at
T/I determines t2e TR :oard $2ere t2e SCC( resides9 and &RCN s!ecifies t2e
TR :oard $2ere t2e TC( resides- C2ec% $2et2er t2e assi"nment failure occurs on a
certain TR :oard- T2en9 locate s!ecific causes :ased on t2e TA value of t2e #S9
u!lin%=do$nlin% level9 and u!lin%=do$nlin% si"nal ;uality included in t2e measurement
re!ort and ma%e dialin" test locally-
5.,87<73. (ua$ei !ro!rietary Pa"e 56 of 38
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
T2e assi"nment failure occurred on a TR :oard may :e caused :y one of t2e follo$in"
reasons@
',) T2e TR :oard is faulty or t2e !erformance is unsta:le-
'5) 1!lin% and do$nlin% levels are not :alanced or u!lin% or do$nlin% antenna tri:utary
2as 2ard$are !ro:lems-
'3) 1!lin% and do$nlin% si"nals are of !oor ;uality- C2ec% t2e c2annel on $2ic2 t2e
interference e?ists :y considerin" t2e TA value-
If assi"nment failures randomly distri:ute on TR :oards in t2e entire cell9 t2e failures
may :e caused :y one of t2e follo$in"s t2rou"2 t2e measurement re!ort analysis@
',) T2e areas covered :y t2e BTS feature t2e com!le? terrain-
'5) T2e fre;uency interference e?ists in t2e entire cell9 for e?am!le9 interference from
re!eaters-
8 Test Met,od
T2e TC( con"estion rate is one of t2e &PIs to evaluate net$or% access !erformance9
$2ic2 can :e o:tained t2rou"2 t2e re"istration or re!ortin" of t2e related &PIs- At
!resent9 vendors and mo:ile o!erators use different formulas to calculate t2e TC(
con"estion rate9 t2us leadin" to different values of t2is counter- In actual measurement9
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
you s2ould re"ister t2e s!ecific counters and use an a!!ro!riate formula to calculate t2e
value of t2e counter-
9 &ppendi0 C,eck Ites on TCH Congestion Rate
C2ec% Item Remar%s Pur!ose
Version
information
Version information a:out
t2e BSC9 PC19 and BTS
To c2ec% t2e version matc2in" relations2i!-
/re;uency
multi!le?in"
mode
,6..#9 Q..# To c2ec% t2e fre;uency confi"uration-
ata
confi"uration
ta:le
U-dat file To c2ec% t2e settin"s of t2e net$or%
o!timi+ation !arameters9 nei"2:or cell
relations9 and !o$er confi"uration
Alarm
information
(ard$are9 cloc%9 and
transmission alarms 'self7
c2ec%)
To c2ec% $2et2er t2ese alarms are
"enerated in t2e cell- (andle t2e alarms if
t2ey are "enerated-
Traffic
measuremen
t
&PI #easurement !er Cell To com!are t2e num:er of S=TC(
re;uests9 S=TC( sei+ure success rate9
and traffic volume to c2ec% $2et2er t2e
coo!eration $it2 t2e nei"2:or BTS is
normal-
Intra7cell (andover
#easurement !er Cell
To com!are t2e num:er of incomin" inter7
cell 2andovers and t2e num:er of out"oin"
inter7cell 2andovers res!ectively :efore and
after net$or% re!lacement to c2ec% $2et2er
t2e coo!eration $it2 t2e nei"2:or BTS is
normal-
Incomin"=*ut"oin"
Internal=E?ternal Inter7Cell
(andover #easurement
!er Cell
rivin" test
data
U-lo" 'U-cell site) or U-ant
file
To identify t2e covera"e !ro:lem :y
com!arin" t2e covera"e :efore and after net$or% re!lacement-
*t2ers En"ineerin" !arameter
ta:le and electronic ma!
To c2ec% t2e "eo"ra!2ical information
t2rou"2 t2e NASTAR soft$are-
: T$pica# Cases
>-,Case ,@ TC( Con"estion Caused :y Terrain Reasons
+escription
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
T2e TC( con"estion rate of a certain omnidirectional cell is 3,.-
Tro"'#es,ooting
Analy+in" A:is7interface si"nalin"9 you can find t2at t2e con"estion reason is t2at t2e
level is too lo$ and t2e :it error rate increases- In addition9 t2e TA value of t2e #S t2e
distance :et$een t2e #S and t2e BTS is 5<-8 %m to 3,-, %m- *:vious9 t2e TC(
assi"nment fails :ecause t2e #S is far a$ay from t2e BTS- #a%e on7site drivin" tests9
and t2en you $ill find t2at an isolated BTS is de!loyed 2ere and t2e area features
com!le? terrain- T2erefore9 t2e con"estion of t2e BTS cannot :e solved tem!orarily due
to environment limitations
Hand#ing Proposa#
To solve t2e cell con"estion !ro:lem caused :y lar"e covera"e and com!le? terrain9
o!erators are advised to do t2e follo$in"s@ Add BTSs to im!lement continuous covera"e-
C2an"e t2e omnidirectional BTS to t2e directional BTS9 adKust t2e a+imut2 and tilt of t2e
antenna9 and en2ance transmit level- In addition9 !revent cross7area covera"e-
>-5 Case 5@ (i"2 TC( Con"estion Rate Caused :y /ault of TR Board
+escription
T2e BTS ado!ts t2e S8==5 confi"uration- *ne day9 t2e traffic measurements su""est
t2at t2e TC( overflo$ rate is 2i"2 in cell , $it2 si? TRs and t2e TC( con"estion rate
reac2es 5.- T2e traffic on TC( in t2e cell is lo$9 "enerally9 .-6Erl durin" :usy 2ours- In
addition9 t2e TC( sei+ure failure due to :usy TC( is .- C2annels on all t2e BTs in cell ,are in t2e idle state- T2e :ase:and attri:ute and RC attri:ute are normal- T2ere is no
a:normality on t2e L#T-
Tro"'#es,ooting
,- *n t2e L#T9 ;uery t2e status of c2annels on BTs :y usin" t2e !recedin" met2od- Mou
can conclude !reliminarily t2at t2e TC( fails to :e sei+ed on BT and BT< in cell ,-
5- If you :loc% BT9 BT<9 RC9 and RC<9 t2ere is no TC( con"estion all day- T2en9 you
can inter t2at RC and RC< are faulty-
3- If you un:loc% BT9 BT<9 RC9 and RC< and reset RC 'TR) and RC< 'TR<)9 2i"2
con"estion rate !ersists-
- Insert and remove TR and TR< on t2e field- After ma%in" dialin" tests 'on TR
and TR<) after fre;uency loc%9 t2e TC( still fails to :e sei+ed- E?c2an"e slots of TR
and TR< and ma%e dialin" tests 'on TR and TR<) after fre;uency loc%- In t2is case9
t2e TC( still fails to :e sei+ed-
<- #a%e dialin" tests 'on TR and TR<) after fre;uency loc% after re!lacin" TR and
TR<- T2en9 t2e TC( is successfully sei+ed and t2e TC( con"estion is released-
>-3 Case 3@ Static TC(( Con"estion Caused :y Insufficient TC(/s
+escription
Previously9 several BTSs ado!tin" t2e static 2alf7rate function $ere added to t2e BSC
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
'G3BSC35V3..R..5C,.)- In su:se;uent days9 2o$ever9 t2e con"estion rate of t2e
several BTSs in :usy 2ours in t2e evenin" is 2i"2 'over ,.)- Instead9 t2e traffic volume
is not very 2i"2- *:vious9 t2e a:normality occurs-
Ca"se &na#$sis
,- C2ec%in" !arameter settin"s9 you $ill find t2at TCH Rate &d>"st &##owed of eac2 cell
is disa:led and static TC((s are confi"ured in t2ese cells- *nly one or no TC( is
confi"ured in t2ese cells-
5- C2ec%in" t2e TC( !erformance measurement9 you $ill find t2at only one or t$o TRs
are confi"ured in t2e con"ested cell-
3- Recordin" t2e !erformance counters in cell !erformance measurement 59 you $ill find
t2at C/55 &55OC &I5 TIM/S R is muc2 "reater t2an &55OC &I5 TIM/S R-
Ma0i" N"'er o B"s$ TCHs is "reater t2an t2e num:er of confi"ured TC(/s-
Ma0i" N"'er o B"s$ TCHHs is smaller t2an t2e confi"ured num:er- C2ec%in"t2e status of TC(s in :usy 2ours9 you $ill find t2at all t2e TC(/s of t2ese cells are
occu!ied and some TC((s are in t2e idle state-
- T2ese cells are located in rural areas or su:ur:s and multi!le #Ss can only use
TC(/s :ecause TC((s are not su!!orted- In addition9 insufficient TC(/s result in
TC(( con"estion-
Tro"'#es,ooting
,- Increase t$o or t2ree TC(/s for eac2 cell accordin" to Traic ?o#"e on TCH and
Traic ?o#"e on TCHH and t2e num:er of TC((s confi"ured in ERLANG B-
5- *:serve t2e traffic measurement result after modifyin" t2ese !arameters- T2en9 youcan find t2at t2e TC( con"estion rate of eac2 cell is "reatly reduced9 nearly +ero-
Hand#ing Proposa#
Si"nificant modifications are made in t2e 2alf7rate al"orit2m ado!ted in C,3 and later
version- If TC((s must :e su!!orted9 it is recommended t2at t2e al"orit2m version is
u!"raded to C,3 or later- In C,3 version9 after t2e TC( rate adKustment is ena:led9 you
can set t2e traffic :usy t2res2old to control t2e ty!e of !referred TC(s- T2en9 t2e
!recedin" !ro:lems are solved-
/or t2e con"estion of t2e cell in $2ic2 2alf7rate service is ena:led9 c2ec% $2et2er
dynamic TC(( adKustment is allo$ed- T2en9 locate t2e main cause and ta%e !ro!er measures accordin"ly-
>- Case @ Increase of TC( Con"estion Rate Caused :y Im!ro!er (alf7Rate
Parameters after 1!"rade from BSC C,. to BSC C,3
+escription
In an area9 t2e TC( con"estion rate increases after BSC C,. is u!"raded to BSC C,3
and t2e 2alf7rate traffic a:sor!tion decreases-
Ca"se &na#$sis
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
BSC C,. does not su!!ort real7time conversion of TC((s- T2erefore9 :efore u!"rade9
TC((s are confi"ured in t2e net$or% and TCH Rate &d>"st &##ow is disa:led9 t2at is9
dynamic adKustment of TC( rate is unallo$ed- In BSC C,.9 if t2e assi"nment re;uest of
t2e #SC is TC(/ !referred or TC(( !referred9 t2e BSC c2ec%s $2et2er t2e num:er of
idle TC(/s is "reater t2an t2e value of Preerred TCH Id#e T,res,o#d and assi"ns
a!!ro!riate c2annels- T2e c2annel confi"uration remains unc2an"ed after u!"rade and
TC(( !arameters use default values in C,3 version- (o$ever9 t2e 2alf7rate al"orit2m
ado!ted :y BSC C,3 "reatly differs from t2at of BSC C,.- In BSC C,.9 TCH Rate
&d>"st &##ow is disa:led- T2erefore9 TC(/s fail to :e coverted to TC((s and t2e TC(
con"estion rate increases-
Tro"'#es,ooting
Set t2e TC( ty!e to TCH "## Rate and TCH Rate &d>"st &##ow to Aes- After t2e
dynamic adKustment of t2e TC( rate is allo$ed9 t2e con"estion rate decreases and 2alf7rate traffic a:sor!tion increases- T2en9 !ro:lems are solved-
Hand#ing Proposa#
BSC C,3 o!timi+es t2e 2alf7rate al"orit2m and reali+es t2e real7time dynamic adKustment
of t2e TC( rate- /ocus on t2e im!act im!osed on t2e traffic a:sor!tion and t2e TCP
con"estion rate :y t2e modification of t2e 2alf7rate al"orit2m after and :efore t2e u!"rade
of t2e BSC version-
>-< Case <@ Increase of TC( Con"estion Rate Caused :y #odification of efault Value of (andover T2res2old
+escription
In a site9 if BSC8... is u!"raded from VQR,C.,B.68 to VQR,C.3B,.9 t2e traffic
measurement result reveals t2at t2e num:er of TC( con"estion is muc2 "reater t2an t2at
'nearly +ero) :efore t2e u!"rade- In addition9 t2e 2i"2er traffic volume in t2e cell9 t2e
more serious t2e con"estion is- T2e traffic volume9 2o$ever9 does not increase s2ar!ly-
Tro"'#es,ooting
/irst9 t2e main cause is not t2e traffic volume :ecause t2e traffic measurement s2o$s no
o:vious c2an"es of traffic volume :efore and after con"estion-
Second9 t2e traffic measurement su""ests t2at t2e interference :and is normal-
T2erefore9 you can infer t2at t2ere is no u!lin% interference-
T2ird9 t2e con"estion occurs suddenly in a "reat num:er of cells and t2e TR sei+ure is
normal in t2e cell $it2 serious con"estion- T2erefore9 you can infer t2at t2ere are no
im!licit faults of t2e :oard-
/ourt29 t2ere are no !arameter modifications recently- T2en9 t2e con"estion cause
cannot :e t2e manual !arameter modification-
T2en9 you can determine t2at t2e con"estion is caused :y u!"rade- Accordin" to
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
tec2nical su!!ort en"ineers and R0 !ersonnel9 t2e P=N !arameter of t2e PBGT
2andover does not :rin" any im!act :efore u!"rade $2et2er t2is !arameter is set to any
value 'By default9 P 3 and N 3)- After u!"rade9 t2e P=N !arameter settin" 'P 3 and
N 5) ta%es effect- T2e num:er of 2andover re;uests is multi!lied several times due to
t2e decrease of t2e 2andover t2res2old-
Hand#ing Proposa#
T2is case !rovides ne$ t2ou"2ts for net$or% o!timi+ation@ To reduce t2e TC( con"estion
rate9 you can increase t2e 2andover t2res2old and reduce t2e num:er of 2andovers in
t2e com!le? do$nto$n area $it2 dense si"nals- If t2is met2od is a!!lied to t2e rural area
$it2 !oor si"nals9 some ris%s may e?ist9 suc2 as call dro! occurs and t2e s!eec2 ;uality
deteriorates 't2e 2andover cannot :e !erformed till t2e covera"e level is in !oor ;uality)-
>-8 Case 8@ Increase of TC( Con"estion Rate Caused :y ReverseConnections of Antennas
+escription
T2e customer com!lains t2at t2e covera"e of a BTS decreases and call setu! is difficult
2o$ever9 no alarm is found on t2e L#T-
Tro"'#es,ooting
Reverse connections of antennas9 transmit antennas9 and receive antennas cause
un:alanced si"nals on u!lin% c2annels and do$nlin% c2annels- T2at is9 t2e user to $2ic2
t2e transmit antenna !oints is :ac% of t2e receive antenna- If t2e #S receives t2e TC(assi"nment command from t2e BSC durin" t2e call9 t2e TC( fails to :e assi"ned and t2e
TC( con"estion occurs due to !oor level and ;uality of u!lin% si"nals of t2e #S caused
:y small "ain of t2e receive antenna-
Hand#ing Proposa#
To solve t2is !ro:lem9 ma%e drivin" tests or use a si"nalin" analy+er to analy+e t2e level
and ;uality of u!lin% and do$nlin% si"nals to c2ec% $2et2er si"nal im:alance e?ists- If
yes9 ta%es !ro!er measures to solve t2is !ro:lem-
If t2e a+imut2 and tilt of t2e main antenna is inconsistent $it2 t2ose of t2e diversity
antenna or t2e diversity or s!acin" is small $2en sin"le7!olari+ation antennas are used in
a cell9 u!lin% and do$nlin% si"nals are inconsistent and TC(s sei+ure failures tend to
occur- T2ere are no suc2 !ro:lems in cells t2at ado!t dual !olari+ation antennas-
>-> Case >@ (i"2 TC( Con"estion Rate ue to No Ca!acity E?!ansion of
Re!eaters after BTS Ca!acity E?!ansion from *5 to *
+escription
After t2e ca!acity of a BTS is e?!anded from *5 to *9 t2e con"estion rate increases9
reac2in" u! to .-Tro"'#es,ooting
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
,- If t2e latter t$o TRs are :loc%ed on t2e remote L#T9 t2e TC( con"estion rate is
dramatically reduced to t2e normal level- T2en9 you can infer t2at t2e main cause is t2e
t$o TRs-
5- Tracin" and analy+in" A:is7interface si"nalin"9 you can find t2at t2e assi"nment failure
occurs on t2e t$o ne$ TRs- 2en t2e assi"nment failure occurs9 t2e measure re!ort of
SCC(s su""ests t2at t2e level on t2e SCC( is normal and t2e TA value is relatively
"reater- T2en9 you can determine t2at t2e failure occurs on a remote area- (o$ever9
t2ere are no SACC( 'TC() measurement re!orts- It is estimated t2at u!lin% or do$nlin%
tri:utaries of t2e t$o TRs may :e faulty- In some cases9 t2e TC( assi"nment is
successful on t2e t$o TRs- T2en9 t2e t$o TRs cannot :e faulty-
3- T2ere are no faults occurred on antenna and feeder 2ard$are :ecause t2is cell ado!ts
t2e four7in7one com:iners and one7to7four dividers- In addition9 t2ere are no 2ard$are
!ro:lems on t2e semi7ri"id ca:les connectin" TR :oards to com:iners and dividers-
- Accordin" to t2e maintenance en"ineers9 t2is cell is installed $it2 a re!eater- Before
ca!acity e?!ansion9 t$o TRs are confi"ured in t2is cell and t$o fre;uencies are loc%ed
:y t2e re!eater- After ca!acity e?!ansion9 no fre;uencies are loc%ed for t2e t$o TRs-
T2erefore9 to solve t2e !ro:lem of 2i"2 TCP con"estion rate9 you must solve t2e
fre;uency !ro:lem of t2e re!eater-
Ca"se &na#$sis
T2e covera"e of t2e latter t$o TRs differs from t2at of former t$o TRs due to t2e
de!loyment of re!eaters- T2is causes TC( assi"nment failure-
>-6 Case 6@ Interference Caused :y Re!eaters
+escription
In cell 3 of a BTS9 t2e call dro! rate reac2es ,. traffic volume is lo$ t2e TC(
con"estion rate is 2i"2- In cell , and cell 59 2o$ever9 t2e call dro! rate and TC(
con"estion rate are normal-
Tro"'#es,ooting
,- T2e TC( con"estion rate remains 2i"2 no matter 2o$ to :loc% TC(s of t2e TR in t2e
cell- It is estimated t2at interference e?ists or t2e area covered :y t2e cell features
com!le? terrain-
5- Accordin" to t2e traffic measurement data9 idle TC(s fall in interference :and or < in
cell 3 in daytime and in interference :and , or 5 from 53@.. in t2e ni"2t to >@.. in t2e
mornin"- T2ere is re"ularity :et$een t2e TC( con"estion rate and call dro! rate and t2e
interference :and-
3- C2ec% $2et2er co7c2annel interference e?ists- C2an"e t2e fre;uency of cell 3 so t2at
t2e s!acin" :et$een t2e fre;uency and t2e ori"inal one is at least , meter- T2e
interference9 2o$ever9 !ersists- T2erefore9 t2e !ro:a:ility of co7c2annel interference and
adKacent7c2annel interference is eliminated-
- C2ec% $2et2er t2e e;ui!ment is faulty- E?c2an"e antenna feeders of cell 3 and cell ,-T2e interference9 2o$ever9 still e?ists in cell 3- T2erefore9 you can infer t2at t2e
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GS# BSS Net$or% &PI 'TC( Con"estion Rate) *!timi+ation#anual V,-.
Confidentiality Level
e;ui!ment is in t2e normal state- T2en9 c2ec% $2et2er e?ternal interference e?ists-
<- 1se a s!ectrum analy+er to ma%e fre;uency s$ee! tests on t2e divider !ort- T2en9 you
$ill find t2at a si"nal similar to t2e si"nal from an analo" s!ectrum 't2e central fre;uency
is Q.-, #(+ and t2e s!ectrum :and$idt2 is 3.. %(+) e?ists continuously- T2e stren"t2
of t2e si"nal at t2e divider !ort of cell 39 cell 59 and cell , is 5> dBm9 . dBm9 and 8.
dBm res!ectively9 and t2e si"nal stren"t2 is consistent $it2 t2e interference level-
T2rou"2 t2e s!acin" :et$een t2e fre;uency and t2e ori"inal one is ,. meters9 t2e
fre;uency out!uts continuous si"nals- In t2is case9 collision and intermodulation $it2
ot2er si"nals tend to occur- Some intersected si"nals may fall in t2e receivin" :and9
causin" interference- T2e traffic volume in daytime is 2i"2er t2an t2at in t2e ni"2t-
T2erefore9 intersected si"nals are more and t2e interference is more serious- (ua$ei
reac2es an a"reement $it2 o!erators t2at t2ere is no Q.-, #(+ interference source-
Put t2e s!ectrum analy+er in t2e car to ma%e drivin" tests- At t2is time9 2o$ever9 no Q.
#(+ interference source is found- T2en9 ma%e drivin" tests on t2e roof- At last9 t2e fault
is considered to :e concerned $it2 t2e unim!ortant little antenna- Su:se;uent si"nal
interru!tion tests !rove t2is 2y!ot2esis- After t2e antenna is !o$ered off9 t2e interference
is eliminated and measurement counters of BTS A :ecome normal-
>-Q Case Q@ TCP Con"estion Caused :y E?ternal Interference
+escription
A cell encounters TC( con"estion caused :y e?ternal interference-
Tro"'#es,ooting
T2ree radars are de!loyed in t2e BTS a:out one %ilometer a$ay from t2e do$nto$n
area- /or t2e 5> radar $2ose o!eratin" fre;uency :and is similar to GS# fre;uency
:and9 t2e o!eratin" fre;uency :and is Q..QQQ#(+ and t2e transmit !o$er is <6.&-
T2e stand:y time is lon"- Lon"7time tests and analysis s2o$ t2at t2e radar cause serious
interference- T2e receiver of t2e BTS features 2i"2 receive :ac%"round noise t2at
reac2es a ma?imum of 6.dBm- T2en9 u!lin% si"nals transmitted from t2e #S $it2 lo$
!o$er may :e over$2elmed :y noise si"nals- At t2is time9 it is difficult for su:scri:ers to
ma%e a call- In addition9 t2ere is no !rom!t sound- As a result9 t2e TC( con"estion
occurs- Mou can reduce t2e interference :y decreasin" t2e antenna tilt-