Closed Subscriber
Group identifies a group of subscribers who are permitted to access one or
more CSG cells of the PLMN.
To make a CSG call UE
should send CSG Id to which it belongs and its access
type in Attach request.
MME then performs UE
authentication with the HSS and then exchanges Update Location Request and Answer.
In Update Location Answer HSS sends CSG
Information(CSG Id, Subscription timer) in
Subscription data.
MME then verifies the CSG
Id with the CSG received in Attach request
if it matches then UE proceed the CSG call
and sends Create session request with CSG
Information IE to SGW. Upon receiving of successful response from SGW, MME
sends Attach Accept message with Member status as ‘member’. After expiry of the Subscription timer for which UE is
subscribed to attach with CSG cell, MME
initiate PDN connection deletion.
What if CSG Id receive in
Attach Request is not same as received in Subscription Data from HSS?
MME still make a successful
call but for the specific time(300 sec) and send Attach Accept message to UE
with Member status as ‘non-member’.
After expiry of non-member timer MME
initiates PDN Connection deletion.
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