In this solution the MSC Server enhanced for ICS performs a special IMS registration on behalf of the UE. Thus, the MSC Server enhanced for ICS shall use a Private User Identity and Temporary Public User Identity that are different to those defined in clause 13
(see TS 23.292
, clause 4.6.2 for more information). Furthermore, the MSC Server enhanced for ICS derives a Conference Factory URI that is known to the home IMS. These are defined in the following clauses.
The home network domain name shall be in the form of an Internet domain name, e.g. operator.com, as specified in RFC 1035
and RFC 1123
. The home network domain name consists of one or more labels. Each label shall consist of the alphabetic characters (A-Z and a-z), digits (0-9) and the hyphen (-) in accordance with RFC 1035
. Each label shall begin and end with either an alphabetic character or a digit in accordance with RFC 1123
. The case of alphabetic characters is not significant.
The MSC Server enhanced for ICS shall derive the home network domain name from the subscriber's IMSI as described in the following steps:
Take the first 5 or 6 digits, depending on whether a 2 or 3 digit MNC is used (see TS 31.102) and separate them into MCC and MNC; if the MNC is 2 digits then a zero shall be added at the beginning.
Use the MCC and MNC derived in step 1 to create the "mnc<MNC>.mcc<MCC>.3gppnetwork.org" domain name.
Add the label "ics." to the beginning of the domain.
An example of a home network domain name is:
IMSI in use: 234150999999999;
MCC = 234;
MNC = 15; and
MSIN = 0999999999,
which gives the home network domain name: ics.mnc015.mcc234.3gppnetwork.org
The Private User Identity shall take the form of an NAI, and shall have the form "username@realm" as specified in clause 2.1 of IETF RFC 4282
The MSC Server enhanced for ICS shall derive the Private User Identity from the subscriber's IMSI as follows:
Use the whole string of digits as the username part of the private user identity; and
convert the leading digits of the IMSI, i.e. MNC and MCC, into a domain name, as described in clause 20.3.2.
The result will be a Private User Identity of the form "<IMSI>@ics.mnc<MNC>.mcc<MCC>.3gppnetwork.org". For example if the IMSI is 234150999999999 (MCC = 234, MNC = 15), the private user identity then takes the form email@example.com
The Public User Identity shall take the form of a SIP URI (see RFC 3261
), and shall have the form "sip:username@domain".
The MSC Server enhanced for ICS shall derive the Public User Identity from the subscriber's IMSI. The Public User Identity shall consist of the string "sip:" appended with a username and domain portion equal to the IMSI derived Private User Identity described in clause 20.3.3. An example using the same example IMSI from clause 20.3.3 can be found below: