6 GA-RC elementary procedures for Registration

3GPP44.318Generic Access Network (GAN)Mobile GAN interface layer 3 specificationRelease 17TS

6.1 Purpose of GAN Registration

The Registration procedure is performed between the MS and the GANC (Default or Serving GANC). The purpose of this procedure is to allow the MS to register for GAN services on the most suitable GANC for the network. The MS as part of the Registration procedure provides the GANC with information relating to the current connectivity of the MS. The GANC, as part of a successful Registration, indicates the GAN mode (i.e., GAN A/Gb mode or GAN Iu mode) that the MS shall operate in while registered with the GANC and provides the MS with the "System Information" message content that is applicable in GAN mode. The Registration procedure is performed using the IPsec tunnel that is established between the MS and the Default or the Serving GANC-SEGW as defined in sub-clause 4.2.

6.2 Registration procedure

Figure 6.2.1: Registration procedure

6.2.1 Registration initiation by the MS

This procedure shall be triggered by the MS under the following conditions:

– the MS has gained IP connectivity (i.e. an IP address is allocated to the MS in the "transport IP" layer); and

– the MS has stored information about a Default GANC.

The Registration procedure is initiated towards the Default GANC after a successful Discovery procedure or after a failed Registration towards a Serving GANC, where no GAN PLMN list was provided to the MS from the Default GANC. The Registration procedure is also initiated towards the Default GANC when no more PLMNs can be selected from the GAN PLMN List received from the Default GANC.

As part of the Registration procedure, the MS may receive a list of PLMN identities when trying to register towards the Default GANC. This list of PLMN identities is passed to the GANC selection process. Following PLMN selection by the GANC selection process, and if registered to a Serving GANC, the MS shall first deregister from the current Serving GANC as defined in sub-clause 6.4.1, and then attempt the registration procedure towards the Serving GANC-SEGW and GANC associated with the selected PLMN.

This procedure is also triggered towards the Default GANC, if the MS at any time wishes to perform manual PLMN selection or "User reselection" irrespective of whether the MS is in manual or automatic PLMN selection mode. If the MS is already successfully registered to a Serving GANC, and a manual PLMN selection or "User reselection" is initiated, the MS shall first deregister from the current Serving GANC as defined in sub-clause 6.4.1 and then initiate registration towards the Default GANC and include an indication that a list of PLMN identities is requested for manual PLMN selection or user reselection. After receiving the requested PLMN list from the Default GANC the MS shall then re-register on the last registered Serving GANC.

GANC information required to initiate the Registration procedure consists of a GANC-SEGW address, a GANC address and a GANC TCP port number. The MS shall initiate the Registration procedure towards a Serving GANC if the corresponding GANC information is available in the stored Serving GANC table. If successful, the stored Serving GANC table in the MS may be updated to contain address information of the successfully registered Serving GANC and the corresponding GSM-CGI, UTRAN cell identity or E-UTRAN cell identity, if available, or AP-ID, if no GSM CGI, UTRAN cell identity or E-UTRAN cell identity is available (see sub-clause 6.2.3.1). UTRAN cell identity consists of the Location Area Identity (LAI) and Cell Identity (defined in [40]). E-UTRAN cell identity consists of the Tracking Area Identity (TAI) and Cell Identity (defined in [55]). The Default GANC is in control of whether or not the MS is allowed to store GANC information in the stored Serving GANC table.

If the MS is in GERAN, UTRAN or E-UTRAN coverage, it shall check if it has stored Serving GANC information for the current GSM CGI in case of GERAN coverage, UTRAN cell identity in case of UTRAN Coverage, or E-UTRAN cell identity in case of E-UTRAN coverage, or if the MS is not in GERAN/UTRAN/E-UTRAN coverage, it shall check if it has stored Serving GANC information for the current AP-ID:

– if found, the MS shall initiate the GAN Registration procedure towards the stored Serving GANC

– if not found, the MS shall initiate the GAN Registration procedure towards the Default GANC

The Location Exclude List contains information about forbidden Locations acquired while attempting GAN registration and is only valid if the MS is in GERAN or UTRAN coverage. It can contain Location information on 3 different levels: Country (i.e. MCC), PLMN (i.e. MCC and MNC) and Location Area (i.e. MCC, MNC and LAC). If the MS is in a location identified by an entry in the Location Exclude List, the MS shall not initiate the GAN Registration procedure. The Location Exclude List shall be deleted upon power cycle.

The AP Exclude List contains information about denied APs. If the MS is being provided IP connectivity by an AP that is on the AP Exclude List, the MS shall not initiate discovery or GAN registration, until the relevant AP has been removed from the AP Exclude List. The AP Exclude List shall be deleted upon power cycle.

To initiate the GAN registration procedure the MS shall:

– If the MS has stored an IP address of the GANC-SEGW, and the MS does not already have an established secure connection to this GANC-SEGW, the MS establishes a secure connection towards the GANC-SEGW according to sub-clause 4.2;

– If the MS has stored a FQDN of the GANC-SEGW, the MS performs a public DNS query to retrieve the IP-address of the GANC-SEGW, if the MS does not already have an established secure connection to this GANC-SEGW, the MS establishes the secure connection towards the GANC-SEGW according to sub-clause 4.2. The MS shall not store the IP address retrieved from DNS for subsequent procedures (apart from DNS resolver caching).

Following successful establishment of secure tunnel:

– If the MS holds an IP address of the GANC, the MS establishes a TCP connection to the GANC at the stored TCP port to be used for Registration with this GANC. If no TCP port has been stored for this GANC, the default TCP port (see sub-clause 12.2.1) shall be used;

– If the MS holds a FQDN of the GANC, the MS performs a DNS query "inside the secure tunnel" to retrieve the IP-address of the GANC. The MS establishes a TCP connection to the GANC at the stored TCP port to be used for Registration with this GANC. If no TCP port has been stored for this GANC, the default TCP port (see sub-clause 12.2.1) shall be used. The MS shall not store the retrieved IP address for subsequent procedures (apart from DNS resolver caching);

– The MS shall only establish a single TCP connection to the GANC over the IPsec tunnel.

After successful establishment of a secure connection to the SEGW and a TCP connection to the GANC, the MS sends a GA-RC REGISTER REQUEST message to the GANC on the TCP connection, including the following information elements:

– The Geographical Location IE, if available;

– AP Location IE, if available;

– Required GAN Services IE, if required;

– If a GAN PLMN list was received during the last registration attempt with the Default GANC and the GANC selection process is finished unsuccessfully (i.e. the MS was not successfully registered to a Serving GANC and to the associated PLMN in the GAN PLMN List IE), then the MS includes the received GAN PLMN List information in the GAN PLMN List IE in the GA-RC REGISTER REQUEST message;

– Else if the MS failed to register during the last registration it attempted with a GANC (Default or Serving), then Register reject Cause IE, Redirection Counter IE and address information (i.e. IP Address or the Fully Qualified Domain/Host Name IE) of the last GANC and last GANC-SEGW;

– Else if the MS was redirected during the last registration it attempted with a GANC (Default or Serving):

– Redirection Counter IE and address information (i.e. IP address or FQDN) of the last GANC and last GANC-SEGW

When GA-RC layer has submitted the GA-RC REGISTER REQUEST message to the TCP layer, it shall start a timer TU3904

6.2.2 Registration processing by the network

6.2.2.1 General

When receiving the GA-RC REGISTER REQUEST message the GANC may either accept or reject the Registration request from the MS. The GANC may also redirect the MS to another GANC or provide a list of PLMN identities that may provide GAN service to the MS.

The GANC should verify that the binding (IMSI, inner IP address) as received in the GA-RC REGISTER REQUEST is the same as the one that the MS used during authentication to the GANC-SEGW.

6.2.2.2 Registration accepted

If the GANC accepts the Registration request from the MS, it shall send the GA-RC REGISTER ACCEPT message to the MS and store information relating to the GAN service requirements of the mobile station.

If the Default GANC indicator is included in the GA-RC REGISTER REQUEST message received from the MS, then the GANC shall include the Serving GANC Table indicator to indicate to the MS whether or not the MS is allowed to store the GANC information in the stored Serving GANC table.

The GANC shall include the IE "GAN Mode Indicator" if the IE "GAN Classmark" received by the GANC in the GA-RC REGISTER REQUEST message included the GAN Mode Support Indicator field with value other than Unspecified. The IE "GAN Mode Indicator" indicates the GAN mode (i.e., GAN A/Gb mode or GAN Iu mode) that the MS shall operate in while registered with the GANC.

6.2.2.3 Registration redirected

If the GANC decides to redirect the MS to another GANC, the network shall send the GA-RC REGISTER REDIRECT message to the MS and act as follows:

– If the MS attempts to register with the Default GANC as indicated by the presence of the Registration Indicators IE in the GA-RC REGISTER REQUEST message and the MS is not in manual PLMN selection mode, user reselection was not triggered and the MS is being redirected to a Serving GANC in the HPLMN, the GANC shall not include the GAN PLMN List information element.

– If the MS attempts to register with the Default GANC as indicated by the presence of the Registration Indicators IE in the GA-RC REGISTER REQUEST message, and the MS is not in manual PLMN selection mode, user reselection was not triggered and based on the current MS location and operator policies, the MS needs to perform a GANC selection, the GANC shall include the GAN PLMN List information element.

– If the MS attempts to register with the Default GANC as indicated by the presence of the Registration Indicators IE in the GA-RC REGISTER REQUEST message and that the MS is in manual PLMN selection mode or user reselection was triggered and requests a list of PLMNs, the GANC shall include the GAN PLMN List information element.

– If the MS attempts to register with a Serving GANC as indicated by the absence of the Registration Indicators IE in the GA-RC REGISTER REQUEST message, the GANC shall not include the GAN PLMN List information.

When the GA-RC layer in the network has submitted the GA-RC REGISTER REDIRECT message to the TCP layer, it may initiate release of its half of the bidirectional TCP connection.

The GANC can send this message at any time, but it shall not be sent to an MS in GA-CSR-DEDICATED or GA-PSR-ACTIVE state.

The GANC may use the Redirect Counter IE, Register Failure Cause IE, Register Reject Cause Value IE and Last GANC IE to detect a problem and redirect the MS to a different Serving GANC.

If the Default GANC indicator is included in the GA-RC REGISTER REQUEST message received from the MS, then the GANC may include the Serving GANC Table indicator to indicate to the MS whether or not the MS is allowed to store the GANC information in the stored Serving GANC table.

6.2.2.4 Registration rejected

If the GANC decides to reject the registration from the MS, it shall send the GA-RC REGISTER REJECT message to the MS. When the GA-RC layer in the network has submitted the GA-RC REGISTER REJECT message to the TCP layer and the value of the Register Reject Cause IE included in the message was not ‘Network Congestion’, it may initiate release of its half of the bidirectional TCP connection.

The GANC may use the Redirect Counter IE, Register Failure Cause IE, Register Reject Cause Value IE and Last GANC IE to detect a problem and reject the MS.

6.2.3 Registration response processing by the MS

6.2.3.1 Registration accepted

When the MS receives GA-RC REGISTER ACCEPT message, it shall:

– stop the timer TU3904,

– reset the Redirection Counter,

– retrieve the GAN Mode Indicator IE (if included) and:

– if no GAN Mode Indicator IE is included or if the GAN Mode Indicator IE is included and indicates that the MS shall operate in GAN A/Gb mode, and the MS supports GAN A/Gb mode, then the MS shall operate in GAN A/Gb mode while registered with the GANC.

– if the GAN Mode Indicator IE is included and indicates that the MS shall operate in GAN Iu mode, and the MS supports GAN Iu mode, then the MS shall operate in GAN Iu mode while registered with the GANC.

– if GAN A/Gb mode is selected, then retrieve the GAN System Information parameters and:

– send the contents of GAN Cell Description IE (if received) to the GSM RR layer or UTRAN RRC to be used for Measurement Reports in GSM RR dedicated mode or GSM RR packet transfer mode or UTRAN RRC connected mode

– store the received GAN System Information and when GA-RC becomes the serving layer send the following information to the upper layers either immediately or upon entering the GA-CSR-IDLE state if the MS is currently in GA-CSR-DEDICATED state:

– from GAN Control Channel Description IE
– Network Mode of Operation,
– GPRS availability Indicator,
– Dual Transfer Mode Indicator,
– IMSI Detach/Attach indicator,
– MSC Release Indicator,
– SGSN Release Indicator,
– T3212 timer value,
– Routing Area Code,
– Emergency Call Mode Preference and
– Emergency Call indicator.

– GAN Location Area Identity.

– Store the Early Classmark Sending Indicator from GAN Control Channel Description IE.

– Store the Call Re-establishment bit from GAN Control Channel Description IE.

– if GAN Iu mode is selected, then retrieve the GAN System Information parameters and:

– send the contents of GAN Iu Mode Cell Description IE (if received) to the GSM RR layer or UTRAN RRC to be used for Measurement Reports in GSM RR dedicated mode or GSM RR packet transfer mode or UTRAN RRC connected mode

– store the received GAN System Information and when GA-RC becomes the serving layer send the following information to the upper layers either immediately or upon entering the GA-RRC-IDLE state if the MS is currently in GA-RRC-CONNECTED state:

– from GAN Control Channel Description IE
– Network Mode of Operation,
– IMSI Detach/Attach indicator,
– MSC Release Indicator,
– SGSN Release Indicator,
– T3212 timer value,
– Routing Area Code,
– Emergency Call Mode Preference and
– Emergency Call indicator.

– GAN Location Area Identity.

– Store the Call Re-establishment bit from GAN Control Channel Description IE.

– Start Keep alive mechanism as defined in sub-clause 6.5 using the received TU3906 Timer IE.

– Use the received TU3910 Timer value as follows:

– When the MS roves out (i.e. leaves GAN mode and enters GERAN/UTRAN mode), it shall start timer TU3910 and shall not rove in (i.e. leave GERAN/UTRAN mode and enter GAN mode) until this timer has expired, unless the MS has detected loss of GERAN or UTRAN coverage.

– If timer TU3910 is running and MS is in GA-RC-REGISTERED state and;

– MS receives GA-RC REGISTER UPDATE DOWNLINK message, the MS shall restart the timer TU3910 using the new value if included in the message.

– If the GA-RC REGISTER ACCEPT was received from the Default GANC, the MS shall store the received Serving GANC table indicator and shall consider the Default GANC to be the Serving GANC.

– If the stored Serving GANC Table indicator is set to "store", update the stored Serving GANC table as follows (the SEGW and GANC address information type, i.e. FQDN or IP address, stored depends on the address type held by the MS when initiating registration i.e. if the MS held an IP address, then that IP-address shall be stored and if the MS held an FQDN, then that FQDN shall be stored):

– If the MS is in GERAN/UTRAN/E-UTRAN coverage and this was indicated in the GA-RC REGISTER REQUEST by including a current GSM CGI, UTRAN cell identity (i.e., LAI and Cell Identity which is defined in [40]), or E-UTRAN cell identity (i.e., TAI and Cell Identity which is defined in [55]):

– if the stored Serving GANC table does not contain the GSM CGI, UTRAN cell identity, or E-UTRAN cell identity, add the GSM CGI, UTRAN cell identity or E-UTRAN cell identity to the table with the information about the Serving GANC: SEGW FQDN or IP-address, GANC FQDN or IP-address and the TCP port to be used (if received in the message, otherwise the TCP port for Registration as defined in sub-clause 12.2.1).

– if the stored Serving GANC table contains the GSM CGI, UTRAN cell identity or E-UTRAN cell identity, update the information about the Serving GANC for this GSM CGI, UTRAN cell identity or E-UTRAN cell identity: SEGW FQDN or IP-address, GANC FQDN or IP-address and the TCP port to be used, as described above.

– If the MS is not in GERAN/UTRAN/E-UTRAN coverage and this was indicated in the GA-RC REGISTER REQUEST:

– if the stored Serving GANC table does not contain the AP-ID, add the AP-ID with the information about the Serving GANC: SEGW FQDN or IP-address, GANC FQDN or IP-address and the TCP port to be used (if received in the message, otherwise the TCP port for Registration as defined in sub-clause 12.2.1).

– if the stored Serving GANC table contains the AP-ID, update the information about the Serving GANC for this AP-ID: SEGW FQDN or IP-address, GANC FQDN or IP-address and the TCP port to be used, as described above.

– If the stored Serving GANC Table indicator is set to "Do not store", the MS should not store the new registered serving GANC information in the stored Serving GANC table but should still maintain the related serving GANC information, if existing in the stored Serving GANC table.

6.2.3.2 Registration redirected

When the MS receives GA-RC REGISTER REDIRECT message, it shall:

– stop the timer TU3904,

– Increment the Redirection counter,

– release the TCP connection towards the GANC,

– if timer TU3910 is running and MS is in GA-RC-REGISTERED state the MS shall stop the timer TU3910,

– if the GA-RC REGISTER REDIRECT was received from the Default GANC, the MS shall;

– store the received Serving GANC table indicator;

– if the GA-RC REGISTER REDIRECT contains the GAN PLMN List information element;

– store the information received in the GAN PLMN List information element ,

– pass the received list of PLMN identities to the GANC selection process;

– release the secure connection towards SEGW of the Default GANC as defined in sub-clause 4.5; and;

– following PLMN selection by the GANC selection process, initiate the registration procedure towards the GANC associated with the selected PLMN as defined in sub-clause 6.2. Each GANC selected in this manner shall be considered as a Serving GANC by the MS;

– if the returned SEGW is the same as the one used for the connection towards the previous GANC,

– if the GA-RC-REGISTER REDIRECT was received from the Default GANC, then:

– if the stored Default GANC-SEGW address information is in an IP address format and the received GA-RC REGISTER REDIRECT message contains the Serving GANC-SEGW IP address IE, and these two IP addresses match, the MS shall reuse the secure connection;

– or if the stored Default GANC-SEGW address information is a FQDN and the received GA-RC REGISTER REDIRECT message contains the Serving GANC-SEGW FQDN IE, and these identifiers match, the MS shall reuse the secure connection.

– if the GA-RC-REGISTER REDIRECT was received from a Serving GANC, then:

– if the MS held a Serving GANC-SEGW IP address for the current Serving GANC (either in the Serving GANC store or received in a previous GA-RC REGISTER REDIRECT) and the received GA-RC REGISTER REDIRECT contains the Serving GANC-SEGW IP address IE, and these two IP addresses match, the MS shall reuse the secure connection, or

– if the MS held a Serving GANC-SEGW FQDN identifier (either in the Serving GANC store or received in a previous GA-RC REGISTER REDIRECT) and the received GA-RC REGISTER REDIRECT contains the Serving GANC-SEGW FQDN IE, and these identifiers match, the MS shall reuse the secure connection

– otherwise release the secure connection towards SEGW of the previous GANC as defined in sub-clause 4.5

– initiate the registration procedure towards the returned GANC as defined in sub-clause 6.2.

6.2.3.3 Registration rejected

When the MS receives GA-RC REGISTER REJECT message it shall:

– stop the timer TU3904,

– if the MS is in the process of GANC selection;

– ignore the received Register Reject Cause Information Element; and;

– proceed as defined in sub-clause 6.2.4.5.

– else extract the Register Reject Cause information element and act as following depending on the value of the Reject Cause IE:

– ‘Network Congestion’
– create a random value between zero and the received value in IE ‘TU3907 Timer’ and
– add this value to the received value in IE ‘TU3907 Timer’, and use this as the new value for TU3907
– start timer TU3907 according to the new calculated value and wait for it to expire.

– ‘AP not allowed’
– release the TCP connection established to the GANC, if still established,
– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5
– store the AP-ID in the AP Exclude List and not initiate a new Register Request from this AP, until the AP-ID is removed from the AP Exclude List i.e. as a result of power-cycle.

– ‘Location not allowed’
– release the TCP connection established to the GANC, if still established,
– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5
– update the Location Exclude List according to the received information elements Location Exclude List indicator and Location Area Identification (i.e. the same as that included in the GA-RC REGISTER REQUEST message) and not initiate a new Register Request from the locations indicated by the updated Location Exclude List, until they are removed from the Location Exclude List i.e. as a result of power-cycle.

– ‘IMSI not allowed’
– release the TCP connection established to the GANC, if still established.
– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5
– not initiate a new GAN Registration procedure until the next power-on.

– ‘Invalid GANC’ or ‘Unspecified’
– release the TCP connection established to the GANC, if still established.
– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5
– act as defined in sub-clause 6.2.4.5

– ‘Geo Location not known’
– release the TCP connection established to the GANC, if still established.
– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5
– not retry registration from this AP until the location is provided or until the next power-on.

The MS shall also:

– Update the stored Serving GANC table as follows if the received Reject cause was not ‘Network Congestion’ or ‘Geo Location not known’:

– If the MS is in GERAN/UTRAN/E-UTRAN coverage it shall remove information related to the current GSM CGI, UTRAN cell identity or E-UTRAN cell identity, if it exists in the table.

– If the MS is not in GERAN/UTRAN/E-UTRAN coverage it shall remove information related to the AP-ID, if exists in the table.

6.2.4 Abnormal cases

6.2.4.1 TU3904 expiry

If timer TU3904 expires in the MS, the MS shall:

– release the TCP connection towards the GANC,

– release the secure connection towards SEGW of the GANC as defined in sub-clause 4.5,

– If GAN registration is unsuccessful after a number of attempts defined by the MS parameter "Up Register Max Retries" (defined in sub-clause 12.2.3), the MS shall act as defined in sub-clause 6.2.4.5.

– Otherwise, if GAN Registration can be re-attempted according to the MS parameter "Up Register Max Retries", start timer TU3905 and wait for it to expire.

6.2.4.2 Lower layer failure in the MS

Lower layer failure in the MS can be for example related to DNS, IPsec or TCP. If any lower layer failure happens in the MS, the MS shall:

– release the TCP connection towards the current GANC, if established,

– Stop timer TU3904 if running,

– release the secure connection towards SEGW of the current GANC, if established, as defined in sub-clause 4.5, and

– If registration is still unsuccessful after a number of attempts defined by the MS parameter "Up Connect Attempt Count" (defined in sub-clause 12.2.3), the MS shall act as defined in sub-clause 6.2.4.5.

– otherwise, stop timer TU3907 if running and

– start timer TU3905 and wait for it to expire.

6.2.4.3 TU3905 expiry

If timer TU3905 has expired in the MS, the MS shall restart the Registration procedure as defined in sub-clause 6.2.1.

6.2.4.4 TU3907 expiry

If timer TU3907 expires in the MS, the MS shall:

– If GAN registration is unsuccessful after a number of attempts defined by the MS parameter "Up Register Max Retries" (defined in sub-clause 12.2.3), the MS shall act as if a "Lower layer failure in the MS" has occurred as defined in sub-clause 6.2.4.2

– else, if the TCP connection to the GANC is still established,

– send a GA-RC REGISTER REQUEST that includes information elements as described in sub-clause 6.2.1 and

– start timer TU3904

– else, restart the GAN Registration procedure towards the GANC as defined in sub-clause 6.2.1

6.2.4.5 Registration Failure

The MS shall;

– If the GANC selection is ongoing:

– act on upper layer indications as follows;

– If no more PLMNs/GANCs are available for GANC selection or the GANC selection is finished unsuccessfully;

– stop all ongoing registration procedures;

– release the TCP connection towards the current GANC, if established,

– release the secure connection towards SEGW of the current GANC, if established, as defined in sub-clause 4.5

– initiate registration towards the Default GANC as defined in sub-clause 6.2.1;

– else if the GANC selection process indicates new PLMN/GANC selection:

– initiate registration procedure towards the GANC associated with the selected PLMN as defined in sub-clause 6.2.

– else if the MS attempted the registration towards the Default GANC

– delete the stored information about the Default GANC,

– delete the contents of the stored Serving GANC table

– Increment Redirection Counter

– initiate Discovery Procedure as defined in sub-clause 5.3

– else if the MS attempted the registration towards current GANC is a Serving GANC

– Update the stored Serving GANC table as defined in the end of sub-clause 6.2.3.3 (i.e. delete information about this Serving GANC in the table) and

– Increment Redirection Counter

– initiate Registration Procedure towards the Default GANC as defined in sub-clause 6.2.1

6.2.4.6 GAN mode selection related failures

If no GAN Mode Indicator IE is included in the GA-RC REGISTER ACCEPT message or if the GAN Mode Indicator IE is included and indicates that the MS shall operate in GAN A/Gb mode, but the MS does not support GAN A/Gb mode, then the MS shall immediately initiate GAN deregistration per sub-clause 6.4.1 and then proceed according to the registration reject procedures defined for the case of ‘Invalid GANC’ in sub-clause 6.2.3.3.

If the GAN Mode Indicator IE is included in the GA-RC REGISTER ACCEPT message and indicates that the MS shall operate in GAN Iu mode, but the MS does not support GAN Iu mode, then the MS shall immediately initiate GAN deregistration per sub-clause 6.4.1 and then proceed according to the registration reject procedures defined for the case of ‘Invalid GANC’ in sub-clause 6.2.3.3.

6.3 Registration Update procedure

After the MS has successfully registered to a GANC, the MS shall update the GANC as a result of the conditions described in sub-clause 6.3.1: This update is performed using the Registration Update procedure.

The GANC may also use the Registration Update procedure towards the MS.

Figure 6.3.1: Registration Update procedure initiated by the MS

Figure 6.3.2: Registration Update procedure initiated by the network

6.3.1 Register Update initiation by the MS

MS initiates this procedure when it has registered successfully to GANC and any of the following occurs:

– The MS acquires GERAN/UTRAN/E-UTRAN coverage for the first time after reporting no coverage during its last GAN registration.

– An MS registered for GAN Iu mode establishes a new UTRAN serving cell as a result of Intra-RAT handover while in GERAN/UTRAN/E-UTRAN mode and the UARFCN of the new UTRAN serving cell is different from the UARFCN indicated during its last GAN Registration or GAN Registration Update.

– An MS registered for GAN Iu mode establishes a new serving cell as a result of Inter-RAT handover to UTRAN while in GERAN/UTRAN/E-UTRAN mode.

– An MS registered for GAN Iu mode enters connected mode in a UTRAN cell while in GERAN/UTRAN/E-UTRAN mode and the UARFCN of the serving UTRAN cell is different from the UARFCN indicated during its last GAN Registration/GAN Registration Update or a UARFCN was not provided during its last GAN Registration/GAN Registration Update.

– An MS operating in GERAN/UTRAN/E-UTRAN preferred mode and registered for GAN Iu mode enters dedicated/Packet Transfer mode in a GERAN cell while in GERAN/UTRAN/E-UTRAN mode and the GERAN serving cell is different from the one indicated during its last GAN Registration/GAN Registration Update. 

– An MS operating in GERAN/UTRAN/E-UTRAN preferred mode and registered for GAN A/Gb mode establishes a new GERAN serving cell as a result of Intra-RAT/inter-RAT handover while in GERAN/UTRAN/E-UTRAN mode. 

– An MS operating in GERAN/UTRAN/E-UTRAN preferred mode and registered for GAN A/Gb mode establishes a new UTRAN serving cell as a result of intra-RAT/inter-RAT handover while in GERAN/UTRAN/E-UTRAN mode.

– An MS operating in GERAN/UTRAN/E-UTRAN preferred mode and registered for GAN A/Gb mode enters dedicated/Packet Transfer mode in a GERAN cell, or enters connected mode in a UTRAN cell or enters connected mode in a E-UTRAN cell while in GERAN/UTRAN/E-UTRAN mode and the GERAN/UTRAN/E-UTRAN serving cell is different from the one indicated during its last GAN Registration/GAN Registration Update. 

– Changes to the generic IP access network point of attachment (i.e. a new radio link is established).

– When the mobile station requires a change to the list of GAN services previously requested within the Required GAN Services IE of a GAN Registration.

The MS shall:

– send a GA-RC REGISTER UPDATE UPLINK message to the GANC on the established TCP connection and include the changed information in the message.

6.3.2 Register Update processing by the network

When receiving the GA-RC REGISTER UPDATE UPLINK message, the network may either accept or reject the Registration Update. The network may also redirect the MS to another GANC.

6.3.2.1 Register Update Accepted

If the network accepts the Registration Update, no message is returned to the MS.

6.3.2.2 Register Update Rejected

If the network rejects the Registration Update, it shall send the GA-RC DEREGISTER message to the MS. This message shall contain the Register Reject Cause information element.

6.3.2.3 Register Update results in redirection

If the network decides to redirect the MS to another GANC, it shall send the GA-RC REGISTER REDIRECT message to the MS. This message shall contain valid information about another GANC, so that the MS is able to initiate the Registration procedure towards that GANC.

The GANC can send the GA-RC REGISTER REDIRECT message at any time, but it shall not be sent to an MS in GA-CSR-DEDICATED or GA-PSR-ACTIVE state.

6.3.3 Register Update Response handling in the MS

6.3.3.1 Register Update Rejected

When the MS receives the GA-RC DEREGISTER message, it shall act as defined in sub-clause 6.4.4 "Reception of GA-RC DEREGISTER by MS".

6.3.3.2 Register Update results in redirection

When the MS receives GA-RC REGISTER REDIRECT message, it shall act as defined in sub-clause 6.2.3.2 "Registration redirected".

6.3.4 Register Update initiation by the network

The network may at any time send the GA-RC REGISTER UPDATE DOWNLINK message to a MS that is registered. This could happen e.g. because of change in the GANC System Information. The network may include all information in this message (i.e. not necessarily only the changed information).

6.3.5 Register Update handling in the MS

When the MS receives GA-RC REGISTER UPDATE DOWNLINK message, it shall process the received information elements as defined in sub-clause 6.2.3.1.

6.4 MS deregistration

The MS should attempt to perform deregistration procedure before leaving the AP. Optionally, the network could also initiate deregistration of a MS.

Figure 6.4.1: Deregistration procedure initiated by the MS

Figure 6.4.2: Deregistration procedure initiated by the network

6.4.1 Deregistration initiated by the MS

When the MS is leaving or about to leave the GAN coverage and the MS has successfully registered with a GANC, it should:

– send the GA-RC DEREGISTER message (with Register Reject Cause = Unspecified) using the currently established TCP-connection,

– release the TCP connection towards the GANC,

– release the secure connection towards the SEGW, as defined in sub-clause 4.5 and

– release all resources related to GAN

6.4.2 Reception of GA-RC DEREGISTER by GANC

When the network receives the GA-RC DEREGISTER message, it shall release all resources associated with the MS.

6.4.3 Deregistration initiated by the network

The GANC may at any time initiate the deregistration of a successfully registered MS by sending the GA-RC DEREGISTER message to the MS. When the GA-RC layer in the network has submitted the GA-RC DEREGISTER message to the TCP layer, it may initiate release of its half of the bidirectional TCP connection.

6.4.4 Reception of GA-RC DEREGISTER by MS

When the MS receives the GA-RC DEREGISTER message, it shall:

– if the MS is in the process of PLMN selection;

– ignore the received Register Reject Cause Information Element, and

– proceed as defined in sub-clause 6.2.4.5.

– else extract the Reject Cause information element and act as following depending on the value of the Reject Cause IE:

– ‘Network Congestion’

– release all local GAN resources (e.g. MS is in active call over GAN)

– release the TCP connection towards the current GANC and

– release the secure connection towards the GANC-SEGW, as defined in sub-clause 4.5

– create a random value between zero and the received value in IE ‘TU3907 Timer’ and

– add this value to the received value in IE ‘TU3907 Timer’, and use this as the new value for TU3907

– start timer TU3907 according to the new calculated value

– ‘AP not allowed’

– release the TCP connection established to the GANC, if still established,

– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5,

– store the AP-ID in the AP Exclude List of and not initiate a new Register Request from this AP, until the AP-ID is removed from the AP Exclude List i.e. as a result of power-cycle.

– ‘Location not allowed’

– release the TCP connection established to the GANC, if still established,

– release the secure connection towards the SEGW associated with the GANC, as defined in sub-clause 4.5,

– update the Location Exclude List according to the received information elements Location Exclude List indicator and Location Area Identification and not initiate a new Register Request from that Location, until the Location is removed from the Location Exclude List i.e. as a result of power-cycle.

– ‘IMSI not allowed’

– release the TCP connection established to the GANC, if still established.

– release the secure connection towards the SEGW associated with the GANC as defined in sub-clause 4.5,

– not initiate a new Registration procedure until the next power-on.

– ‘Unspecified’

– release the TCP connection established to the GANC, if still established.

– release the secure connection towards the SEGW associated with the GANC as defined in sub-clause 4.5,

– act as if a "Lower layer failure in the MS" has occurred as defined in sub-clause 6.2.4.2

– ‘Invalid GANC’

– release the TCP connection established to the GANC, if still established.

– release the secure connection towards the SEGW associated with the GANC as defined in sub-clause 4.5,

– act as defined in sub-clause 6.2.4.5 "Registration Failure"

– ‘Geo Location not known’

– release the TCP connection established to the GANC, if still established.

– release the secure connection towards the SEGW associated with the GANC as defined in sub-clause 4.5,

– not retry registration from this AP until the location is provided or until the next power-on.

The MS shall also,

– Update the stored Serving GANC table as following if the received Reject cause was not ‘Network Congestion’ or ‘Geo Location not known’

– If the MS is in GERAN/UTRAN/E-UTRAN coverage

– Remove information related to the current GSM CGI, UTRAN cell identity or E-UTRAN cell identity, if exists in the table

– If the MS is not in GERAN/UTRAN/E-UTRAN coverage

– Remove information related to the AP-ID, if exists in the table.

6.5 Keep alive mechanism and TU3906 handling

When the MS receives the GA-RC REGISTER ACCEPT message, it shall initiate the GA-RC Keep Alive -mechanism by starting timer TU3906 using the TU3906 Timer value received in that message.

When timer TU3906 expires in the MS, the MS shall send the GA-RC KEEP ALIVE -message to the GANC and start timer TU3906.

If the MS releases the TCP connection (e.g. because of receiving GA-RC REGISTER REDIRECT, GA-RC REGISTER REJECT and GA-RC DEREGISTER message), then it shall stop timer TU3906.

Figure 6.5.1: Keep Alive procedure

If the MS detects, that it is not able to send the GA-RC KEEP ALIVE message to the network due to lower layer failure, it shall act according to sub-clause 9.5.

6.6 MS Initiated Synchronization after TCP connection reestablishment

When MS receives TCP RST after TCP connection failure, it shall try to re-establish the signalling connection using GA-RC Synchronization procedure. The following message flow depicts the messages associated with this procedure:

Figure 6.6.1 MS initiated synchronization procedure

6.6.1 Initiation of the Synchronization Procedure by the MS

When MS receives TCP RST indicating a TCP connection failure, it shall attempt to re-establish TCP connection once. After successfully re-establishing TCP connection, the MS shall send GA-RC SYNCHRONIZATION INFORMATION to the GANC to synchronize the state information. If TCP connection re-establishment is unsuccessful, the MS shall release the related local GA-CSR and GA-PSR resources (if the MS is operating in GAN A/Gb mode) or GA-RRC resources (if the MS is operating in GAN Iu mode), and continue as per section 9.5 as if a TCP failure other than TCP RST has occurred.

6.6.2 Processing of the Synchronization Information message by the GANC

Upon receiving the GA-RC SYNCHRONIZATION INFORMATION message from the MS, the GANC updates the MS state information as specified in the request.

Moreover, the GANC should verify that the binding (IMSI, inner IP address) as received in the GA-RC SYNCHRONIZATION INFORMATION is the same as the one that the MS used as identity for authentication to the GANC-SEGW.

6.7 Transmission of Cell Broadcast Information

If the GANC has previously received the indication that the mobile station requires to receives the CBS, the GANC may pass the GA-RC CELL BROADCAST INFO message to a mobile station including one or more pages of Cell Broadcast messages.

Figure 6.7.1: Transmission of Cell Broadcast Information by the network