VoLTE Performance Issue

VoLTE call setup failure while performing S1 handover  Detailed flow When the the UE is performi performing ng the the S1 handov handover er while while the the user is trying trying to to make the volte volte call. PGW PG W init initia iate ted d ear earer er rel relat ated ed re! re!ue uest sts s ""E may may re#ect re#ect the the re!uest re!uest with with the cause-i cause-id d of reason reason unspeci unspecified. fied. $lead $lead to to the ripple ripple effec effectt towards the upstream forcing each node on the path to release the corresponding resources%. &an ando dov ver is su succ cces ess sfu full. ''(-U ''(U with (ES) (ES)U(' U('E E *++)' *++)'*, *,) ) /*+ /*+U(E U(E -0 -0 P'(/ -0*S -0*S( ( with (ES)U (ES)U('E ('E ), ),  **+*2  * *+*2+E. +E. ,he process process ends up up with with sending sending the the 345 Servi Service ce Unavail Unavailale ale y y the P-'S P-'S'/ '/.. Upon receiv receiving ing the the 345 Serv Service ice Unavai Unavailale lale66 the UE releas releases es all the resourc resources es for for the call.

In the 3GPP TS29.274(r9), the 3GPP has specifed the proper cause value o !Te"poraril# re$ected due to handover in pro%ress! and in the 3GPP  TS29.274(r&&),  TS29.274(r&&), !Te"poraril# !Te"poraril# re$ected re$ected due to handover'T handover'T'* '*  procedure procedure in pro%ress!. This cause+id value is used # the -- re$ectin% the earer related re/uest 0hen the handover results in the relocation o the Servin% G1 and'or --. The P G1 0hich initiated the earer related re/uest 0ill e ale to consider this error cause value to handle the re$ection.

Handing of Rejected bearer related request & The P G1 "a# "a# retr# retr# the rea reate te 5earer 5earer *e/ue *e/uest st ased ased on the operato operator6s r6s polic#. 7 I there is no need o relocation o -- and'or Servin% G1, the -- does not need to respond 0ith the cause+id, rather it can  perform store-andstore-andforward 0a# forward 0a# o "essa%e handlin%.