03.683GPPStage 2TSVoice Group Call Service (VGCS)
8.1 Information stored in the GCR
8.1.1 Information used for routing of service subscriber originated voice group calls
The GCR shall hold for a related MSC area for each group ID and cell from which voice group calls can be established by service subscribers the group call reference to be used for a voice group call to be established and an indication whether the originating MSC is the group call anchor MSC.
If the originating MSC is the group call anchor MSC, the GCR shall provide the group call attributes related to that group call reference as defined in subclause 8.1.2 to the originating MSC and the originating MSC shall establish the voice group call.
If the originating MSC is not the anchor MSC, the GCR shall provide the group call reference plus the routing information identifying the anchor MSC to the originating MSC and the originating MSC shall route the voice group call to the anchor MSC.
NOTE: In case the GCR function is distributed over different physical entities, each may hold only the information needed to treat requests coming from the MSCs connected to the physical GCR entity.
8.1.2 Group call attributes
Each MSC involved in a voice group call requests its proper group call attributes from its related GCR. For any group call reference the GCR shall provide the corresponding group call attributes to the requesting MSC. These lists shall be programmed by the service provider at registration of the network specific service configuration.
The contents of each list related to requests of the group call anchor MSC is as follows:
– a list of cells inside the MSC area of the group call anchor MSC into which the call is to be sent (part of the group call area), see subclause 18.104.22.168;
– a list of group call relay MSCs into which the call is to be sent;
– information on the cipher algorithm and the group key to be used for this voice group call;
– information on the codecs allowed for this voice group call;
– a list of identities of dispatchers to which a dedicated link is to be established, see subclause 22.214.171.124;
– a list of identities of dispatchers which are allowed to initiate the voice group call, see subclause 126.96.36.199;
– a list of identities of dispatchers which are allowed to terminate the voice group call, see subclause 188.8.131.52;
– the length of time over which no activity is detected before the voice group call is automatically terminated, see subclause 184.108.40.206;
– the default priority level related to the voice group call if eMLPP applies, see subclause 220.127.116.11;
– a status flag indicating if a voice group call with the related group call reference is on-going, see subclause 18.104.22.168.1.
The contents of each list related to requests of a group call relay MSC is as follows:
– A list of cells inside the MSC area of the requesting MSC into which the call is to be sent (part of the group call area), see subclause 22.214.171.124;
– Identity of the group call anchor MSC;
– A status flag indicating if a voice group call with the related group call reference is on-going, see subclause 126.96.36.199.1.
188.8.131.52 Group call area
The group call area is defined as a list of cells inside the network. The cells shall be defined by their cell identification consisting of the Location Area Code and the Cell Identity as defined in 3GPP TS 08.08 and are therefore uniquely identified in the network.
In the case the group call area extends over several MSCs, only the cells belonging to the requesting MSC are included in the group call attributes.
184.108.40.206 Dispatcher identities
Dispatcher identities shall be ISDN numbers or MSISDN numbers with the structure according to CCITT Recommendation E.164. They shall correspond both to the number to be used to establish a call toward the dispatcher and the number provided as calling line identification when the call is originated by a dispatcher.
The list of dispatcher identities is used by the anchor MSC to establish dedicated communication paths to each dispatcher and connect them to the conference bridge of the call.
The list of dispatcher identities which are allowed to initiate voice group calls is used by the anchor MSC for verification for a voice group call establishment by a dispatcher.
The list of dispatcher identities which are allowed to terminate voice group calls is used by the anchor MSC for verification for a voice group call release by a dispatcher.
220.127.116.11 No activity time
A timer in the anchor MSC used to release the voice group call because of no activity can be set to a fixed value or can be set to a value defined for each voice group call.
The timer in the anchor MSC shall be started each time an uplink release has been indicated to the MSC and no dispatcher is talking. It shall be reset each time an uplink access is indicated to the MSC or a dispatcher is talking.
When a variable timer is provided, there shall be sufficient timers such that one can be associated with each on-going group call. The corresponding time shall be stored in the GCR.
The length of the timer is not specified in the GSM technical specifications.
If the eMLPP supplementary service is applied to a voice group call, the priority level shall be stored in the GCR. For further details see 3GPP TS 03.67.
8.2 Information managed per subscriber
8.2.1 Stored in the HLR
The following additional information shall be stored in the HLR:
– the subscription option for voice group calls which can be made in the HPLMN only or also in case of roaming;
– a list of all the group IDs a service subscriber is entitled to use.
The group IDs are defined in subclause 9.1.
A service subscriber shall not be provided with more than 50 group IDs.
8.2.2 Stored in the VLR
The list of all the group IDs a service subscriber is entitled to use shall be brought forward to a VLR at the same time as other subscriber information is copied, and VLR entries shall be modified when corresponding HLR records are changed.
8.2.3 Stored in the SIM
The information detailed in subclause 8.2.1 also needs to be stored on the SIM. The service subscriber shall be able to deactivate or reactivate a group ID by MMI interaction so that the mobile station does ignore notification messages to this group ID.
For each group ID where data confidentiality may be applied, the SIM needs to store the cipher algorithm to be used and the possible group keys.
8.3 Information used for routing of dispatcher originated voice group calls
Routing of dispatcher originated calls shall be performed on the MSISDN number received at a GMSC in the Initial_Address_Message.
– Because the group call reference is included in the called MSISDN number as defined in subclause 9.2d the routing information can be derived by the routing function of the GMSC. The GMSC afterwards directly routes the call request to the group call anchor MSC without requesting an HLR.