LTE Retainability
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Transcript of LTE Retainability
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LTE Retainability
Problem cause &solution a-z step
Prepared by- Rajesh Kumar
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RetainAbility/SARR(Session abnormal release rate) :-
Definition: Ability of a user to retain the E-RAB once Connected for the
desired duration.
Point:-E-RAB release can be initiated by ENB & MME
Definition based on Counter :-
SARR=[(PErabRelAbnoralEnbAct!PErabRelMeAct"#
(PErabRelAbnoralEnbAct!PErabRelNoralEnb!PErabRelMe"$%''
Enb nitiated E-Rab Release:-
1> PmErabRelNormalEnb
> PmErabRelAbnormalEnbAct
MME nitiated E-Rab Release:-
> PmErabRel!me
>PmErabRel!meAct
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RetainAbility/SARR(Session abnormal release rate) :-
1> )ErabRelAbnoralEnbActCdt"#he total number of abnormal ERAB
releases by the eNB $er cell due cell do%n time "manual inter&ention' %ith the
$re-condition that the (nitial Conte)t Establishment $rocedure must first ha&e
been successfully com$leted and that there %as data in either the *+ or ,+ buffer
"i.e. acti&e'.
Soln: Chec uta/e re$ort or 0luctuation Re$ort.
>)ErabRelAbnoralEnbAct*o"#he total number of abnormal ERABreleases $er cell by the eNB due to hando&er e)ecution failure and that there %as
data in either the *+ or ,+ buffer "i.e. acti&e'.
Soln:1>PC( Collision issue chec"PC( Plannin/ should be correct'.#here should
no PC( re-use %ithin near by cell"1tiertier neib'.
> Co&era/e issue"mae Any PC( ,ominant %hich should be based on Clutter as
$er Common sense'.!ae E,#Chan/e A2imuth3> 4i/h *+ (nterference issue on #ar/et cell"PmRadiorec(nterferenceP%r'. Chec
Connection b5% Antenna Connector 6 RR* Connector.
7> Also Re$eater is res$onsile sometimes for 4i-*+ (nterference.!i/ht be due to
Po%er +eaa/e.
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RetainAbility/SARR(Session abnormal release rate) :-
7> 458 issueAlarm issue.Correct the issue based on Problem u (dentify.#ae hel$
of Ale) if you are not *nderstandin/ the Alarm meanin/.
3> )ErabRelAbnoralEnbAct+e,ost"#he total number of abnormal ERAB
releases by the eNB $er cell due that the contact %ith the *E is lost %ith the $re-
condition that the (nitial Conte)t Establishment $rocedure must first ha&e been
successfully com$leted and that there %as data in either the *+ or ,+ buffer "i.e.
acti&e'.Soln: 1> Sol&e the Poor Co&era/e issue by main/ #iltA2imuth chan/e or
Parameter chan/e"Part of Sector P%rENB Po%er' for u$lin
Co&era/e"P9NominalPucchP9NominalPusch'.
> 4i/h *l (nterference issue"As $er earlier mentioned.Also mae sure Nominal
$%r Should not set &ery hi/h other%ise it %ill create interference in neib cell'.
.
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RetainAbility/SARR(Session abnormal release rate) :-
7 )ErabRelAbnoralEnb,ic"#he total number of abnormal E-RAB
Releases initiated by the RBS due to license reect "$er cell'.Soln:1. Recently this issue ( ha&e faced in ;S$rint N< Proect=.After
analysis it %as found that there %as issue %ith +0 file.nce Ne% +0 file
u$loaded issue /et resol&ed.
. (f +0 is correctly loaded then #his counter %ill Pe/ only 8hen user
ha&e crossed the ENB +icense limit.
Pls u$/rade the +icense.nce u thin that e&ery basic $timi2ation u ha&e
done.
?>)ErabRelAbnoralEnbAct.n/ail"#he total number of abnormal
ERAB releases $er cell due to S1 interface do%n @ interface do%n@ or
@#rans$ort Resource *na&ailable@ %ith the $re-condition that the (nitial
Conte)t Establishment $rocedure must first ha&e been successfullycom$leted and that there %as data in either the *+ or ,+ buffer "i.e.
acti&e'.
Soln: 1> Raise #icet to NC or (! #eam to resol&ed the issue.
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RetainAbility/SARR(Session abnormal release rate) :-
>)ErabRelAbnoralEnbAct*)r "#he total number of abnormal ERAB
releases by the eNB $er cell due to hando&er $re$aration and that there%as data in either the *+ or ,+ buffer "i.e. acti&e'.
Soln:1>!!E mi/ht be +oced5 disabled.
> !!E mismatch b5% Scource 6 #ar/et cell.
3> #ran$ort issue sus$ected.7> +icense issue sus$ected.
?> Site Confi/uration issue.
> 4i-+oad on #ar/et Cell.
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RetainAbility/SARR(Session abnormal release rate) :-
0rom dri&e test analysis it %as obser&ed that a lar/e $ortion of the
dro$ calls %ere due to $oor radio en&ironment. Dust before 4 it %as obser&ed that the *E S(NR %as $oor and this
caused the *E to dra/ the call in $oor radio en&ironment rather than
4 faster to a nei/hbour cell %ith better RSRP.
(n this o$timi2ation $roect $arameters %ere tuned A3offset and
a#resholdRsr$Prim.– A3offset : chan/e from 3 to db
– a#resholdRsr$Prim : chan/e from -19 to -119 dbm
A trial %as also conducted to e&aluate the im$act of chan/in/ the
&alues belo% for a fe% sites %ith hi/h ,CR:
– ,ataRadioBearer : dl!a)Ret)#hreshold 5 ul!a)Ret)#hreshold› F to 3
– Si/nalin/RadioBearer : dl!a)Ret)#hreshold 5 ul!a)Ret)#hreshold› F to 3
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Retainibility/SARR(Session abnormal release rate) :-
8ith current A3 settin/ A3 e&ent hando&er %ill be $erformed %hen
nei/hbour cell is /reater than a3ffset G hysteresis "RSRP' of the currentser&in/ cell.
a3ffset H 3 dB hysteresis H 1dB 4ando&er %ill only be $erformed once
Nei/hbour Cell RSRP > 7dB of Ser&in/ Cell RSRP
#hus it is im$ortant to e)$edite the 4 %ith reduction of a3ffset to dB.
After the $arameter chan/e it %as obser&ed that the dro$ calls due to call
dra//in/ %as reduced in a cluster of 9 sites.
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RetainAbility/SARR(Session abnormal release rate) :-
R+ 0ailure #imin/– t-PollRetransmit = 7?ms "SRB' ?9ms ",RB'
– (f retransmission limit increases from F 3 R+ failure due toretransmission limit reached:
› SRB: 39ms "F' 1779ms "3'
› ,RB: 799ms "F'
199ms "3'#herefore from dri&e test
analysis it is often obser&edthat the dro$ occur before
#319 time out because Re#)
hits u$$er limit first
I #319 "999ms'
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LTE Retainability Tuning
Timer is s! the "E is unable tosuccess#ully R$% the ser'ing cell(
RR% )rops - T*+ Timer
%ause, Radio Lin problem–Poor R.RP! e(g( belo/ -+0d1 can cause the up linsynch be lost(
–+ seconds later a ne/ RR% %onnection Re2uest is sent(
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LTE Retainability Tuning
RR% )rops - T*+3 Timer
%ause, ando'er 4ailure
– %hec R4 %onditions! "E T5 Po/er and missing relation 6P%78(
– 7# the issue is seen in good R4 conditions! troubleshoot /ith "ETR! tuning o#ysterisis$*! TimetoTrigger$* and 9lter%oe:cientE"traRsrp parameters(
J
Timer is s! The "E isunable to R$% the Target %ell atando'er(
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LTE Retainability Tuning
RR% )rops - T*+ Timer
The "E in RR%-%;
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LTE Retainability Tuning
RR% )rops - T* Timer
%ause, Radio Lin 6RL8 .ynchronization–"E not able to 9nd suitable cell due to poorco'erage(
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LTE Retainability Tuning
RR% )rops – Random $ccess #ailure at ando'er
%ause, R$ #ailure! "E is not able to synch to target e
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LTE Retainability Tuning
@$%AR$AProblem – Random$ccess attempt to re-sync! #orno response a#ter +retransmission 6.71B8
RR% )rops – Random $ccess #ailure at ando'er
%ause, R$ #ailure! "E is not able to synch to target e
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LTE Retainability Tuning
RR% )rops – @a>imum RL% Retransmissions
%ause, Repeated RL% Retransmissions due to unsuccess#ul RL% P)" reception6either "L or )L8(
– This occurs /hen ma>imum retransmission has occurred at RL% le'el 6$R=8(
– "LC)L inter#erence and Poor R4 conditions(
– "E /ill consider RL #ailed and initiate RR% %onnection Re-establishment(
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@;% Parameter Ret>Threshold - )ataRadio1earer .ite Le'el Parameter
E"tran%ell4)) no;#Pucch%2i"sers .ector Le'el Parameter G3+
E"tran%ell4)) no;#Pucch.r"sers .ector Le'el Parameter 0H+
E"tran%ell4)) pdcch%9@ode .ector Le'el Parameter %4A.taticA* 6*8
E"tran%ell4)) ul.rsEnable .ector Le'el Parameter TR"E
"l4ss #eature.tate"l4ss .ite Le'el Parameter
E"tran%ell4)) pIero
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RetainAbility/SARR(Session abnormal release rate) :-
Note: Any Su//estion50eedbac %ill be 4i/hly A$$reciable to (m$ro&e #hisPresentation.
T$