inter-rat ho failure timer handling

8/9/2019 Inter-RAT HO Failure Timer Handling

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3GPP TSG-RAN WG2 Meeting #63bis R2-085058Prague, Cze! Re"ubi30t!Se"te$ber % 3r&'t(ber 2008

Agen&a ite$) *+S(ure) N(ia C(r"(rati(n, N(ia Sie$ens Net.(rs, /riss(n

Tite) Tet Pr("(sa 1(r ' 1aiure ti$er !an&ing

(u$ent 1(r) isussi(n an& eisi(n

1 Introduction

In this contribution we discuss how inter-RAT HO were handled between 2G and 3G and consider whether similar

handling should be adopted in E-UTRA!

2 Legacy timer handling

Handover GERANUTRAN

"urrentl# in the 2$!33% the handling o& HO to UTRA is handled &ollowingl#'

ote that the de&ault (alue o& T3%2 )%s* is used )i!e! not signaled in the container*! In the HO to GERA case there is

also a timer with a &i+ed (alue )T32%, &or . HO and T3%2/ &or ". HO*! I& there is a problem in the target s#stem

)de&ined in target side speci&ications*0 then the &ollowing actions ta1e place'

3GPP

8.3.6.3 Reception of Handover to UTRAN command message by the UE

The UE shall be able to receive a HANDOVER TO UTRAN COMMAND message and perform an interRAT handover! even if

no prior UE meas"rements have been performed on the target UTRAN cell and#or fre$"enc%&

The UE shall act "pon all received information elements as specified in s"bcla"se '&(! "nless specified other)ise in the

follo)ing&

The UE ma%*

+, maintain a list of the set of cells to )hich the UE has Radio -in.s if the /E 0Cell /D0 is present&

The UE shall*

+, store a URNT/ val"e 123 bits4! )hich is derived b% the /Es 05RNC identit%0 1+3 bits4 and 05RNT/ 30 1+6 bits4

incl"ded in /E 0URNT/short0& /n order to prod"ce a f"ll si7e URNT/ val"e! a f"ll si7e 05RNT/0 136 bits4 shall be

derived b% padding the /E 05RNT/ 30 )ith +6 7ero bits in the most significant positions8 and

+, initialise the variable E5TA9-/5HED:5/;NA--/N;:CONNECT/ON5 )ith the signalling connections that remains

after the handover according to the specifications of the so"rce RAT8

+, initialise the variable UE:CA


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Handover UTRANGERAN

Hando(er &rom UTRA to GERA has a similar beha(iour0 i!e! the hando(er &ailure timer is )implicitl#* gi(en &rom

the target s#stem and the (alue is 1nown also b# source RAT and UE! A&ter the e+pir# UTRA side is noti&ied and

&ollowing operation ta1es place'

Re-use of legacy behaviour

To our understanding it is possible to utilie (er# same beha(iour also in EUTRA and thus enabling e&&icient reusage

o& UTRA implementations without reuiring changes in the 2$!33% )at least in ,!3!4!$* and corresponding GERA

speci&ications0 which would be the case i& we ha(e a timer running in EUTRA side determining when HO &ails0 but

with a di&&erent e+pir# (alue! Thus we propose that HO beha(iour &rom E-UTRA would be as described in bullets %-3

in order to align beha(iour with legac# HO designs'

%! In the HO &rom EUTRA there is no &ailure timer gi(en! The de&ault HO &ailure timer (alues &rom the target

RAT speci&ications are utilied! )In the &uture the timer e+pir# (alues ma# be included in the container part0

which includes target s#stem message*

2! 5rom a UE perspecti(e the timer will be running 6in the target s#stem7 and i& it e+pires the indication is

pro(ided to 6source protocol7

3! The beha(iour in the &ailure case is de&ined in the source protocol i!e! in 34!33%

This change should also minimie ris1s o& two di&&erent timers running in two di&&erent protocol stac1s and i& the e+pir#

happens to be almost simultaneous the racing condition between protocol stac1s ma# cause some unpredicatable

beha(iour! It can be noted that T38/ could be de&ined to be used as T3%20 which also eliminates con&licts! 9ut there is

no real gain &rom this &le+ibilit# and some special rules would an#wa# need to be de&ined &or GERA T32%,:T3%2/0 so

this is no good wa# &orward!

In the other direction0 HO to EUTRA0 similar beha(iour is e+pected i!e! the target side decides the hando(er e+pir#

timer (alue! In this case T38/ is e+plicitl# gi(en in the RR""onnectionRecon&iguration message and a&ter e+pir# this is

indicated to source s#stem! It should be noted that this is the alread# the beha(iour described in 34!33%!

This change would ensure that handling would be similar to e+isting mechanism between UTRA and GERA thusenabling e&&icient reusage o& e+isting implementations and thus speeding o& EUTRA time to mar1et!

Summary of changes

3GPP

2

8.3.6.5 UE fails to perform handover

/f the UE does not s"cceed in establishing the connection to UTRAN! it shall*

+, terminate the proced"re incl"ding release of the associated reso"rces8

+, res"me the connection "sed before the handover8 and

+, indicate the fail"re to the other radio access technolog%&

Upon receiving an indication abo"t the fail"re from the other radio access technolog%! UTRAN sho"ld release the

associated reso"rces and the conte>t information concerning this UE&

8.3.7.5 UE fails to complete requested handover

/f the UE does not s"cceed in establishing the connection to the target radio access technolog%! it shall*

+, revert bac. to the UTRA config"ration8

+, =or =DD*

?

+, @hen the HANDOVER =ROM UTRAN =A/-URE message has been s"bmitted to lo)er la%er for transmission*

3, the proced"re ends&


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The changes inMobilit%=romEUTRACommand handling toe+isting 34!33% are &ollowing'

- T38/ onl# applies in case o&Mobilit%=romEUTRACommandto ""O

- T38/ started in in case o& ""O

- T38/ pro(ided to UE onl# in case o& ""O

5ailure handling is alread# de&ined e&&icientl# co(ering the &ailure in the target s#stem in the 34!33% ch! $!/!3!$'

The UE shall*

+, /f T26 e>pires 1mobilit% from EUTRA fail"re48 or

+, /f the UE does not s"cceed in establishing the connection to the target radio access technolog%*

3, /f the Mobilit%=romEUTRACommand message incl"ded the cs=allbac./ndicator*

It should be noted that &or ""O the beha(iour in UTRA and GERA is so that source s#stem gi(es the timer (alue

i!e! similar to e+isting handling o& T38/ in case o& Mobilit%=romEUTRACommand& .o no changes are reuired to this to

align inter-RAT procedures!

3 Conclusion and Proposal

It is proposed to agree on the te+t proposal attached0 which tries to align HO beha(iour to:&rom EUTRA with e+isting

HO designs between 2G and 3G! It seems that with this change there is no need to change GERA:UTRA

speci&ications as the current te+ts seems to wor1 well as in UTRA the re&erences regarding HO handling &rom other

RATs are not to particular RAT but generall# to source RAT!

9eginning of 3ndTe>t '

2; consider inter-RAT mobilit# as initiated towards the RAT indicated b# the targetRATT%peincluded in the

Mobilit%=romEUTRACommandmessaget t


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MobilityFromEUTRACommand-r&-IEs ::= SEQUENCE {

t(, ENUMERATE. {

ms1,," ms*,," ms/,," ms1,,,"

ms*,,," ms,,," ms&,,," s'ar+"

tar0tRAT-Ty' ENUMERATE. {

tra" 0ran" cdma*,,,-12RTT" cdma*,,,-$R3." s'ar"

s'ar(" s'ar*" s'ar1" 444+"

tar0tRAT-Mssa0Containr %CTET STRIN5"

csFallbac6Indicator ENUMERATE. {tr+ %3TI%NA)" -- Nd %3 'r'os C$%ICE{

7ando8r $ando8r"

cllC7an0%rdr CllC7an0%rdr

+"

nonCriticalE#tnsion SEQUENCE {+ %3TI%NA)

+

$ando8r ::= SEQUENCE {

tar0tRAT-Ty' ENUMERATE. {

tra" 0ran" cdma*,,,-12RTT" cdma*,,,-$R3." s'ar"

s'ar(" s'ar*" s'ar1" 444+"

tar0tRAT-Mssa0Containr %CTET STRIN5"

+

CllC7an0%rdr ::= SEQUENCE {

t(, ENUMERATE. { ms1,," ms*,," ms/,," ms1,,,"

ms*,,," ms,,," ms&,,," s'ar+"

+

-- ASN1ST%3

MobilityFromEUTRACommand1ie& &esri"ti(ns

t304$imer $3(4 as described in section ).3. *alue ms1(( corresponds +ith 1(( ms, ms2(( corresponds +ith 2(( ms andso on.

targetRAT-TypeIndicates the target R%$ type.

targetRAT-MessageContainer

sed to carry messages corresponding to specifications from the target R%$.csFallbackndicatorIndicates that the C" -allbacprocedure is triggered.

End of 2rdTe>t

inter-rat ho failure timer handling

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