4 Description

02.693GPPRelease 1999Stage 1TSVoice Broadcast Service (VBS)

The VBS is defined in the following. Figure 1 gives an explanation of the logical concept of the VBS.

a) The VBS enables a calling service subscriber or calling dispatcher to send speech unidirectional and simultaneously to all entitled dispatchers and to destination service subscribers belonging to a predefined group call area who have a subscription to the applicable group ID.

b) The calling service subscriber may be any service subscriber which has subscribed to the related group ID and is entitled to establish a voice broadcast call by his subscription. The calling dispatcher may be any dispatcher who is entitled to originate VBS calls to the related call reference.

The destination subscriber may be any service subscriber which has subscribed to the related group ID or any dispatcher who is entitled for it by his identity which is registered in the network.

c) The broadcast call shall be established in a group call area which is comprised of one or a cluster of cells. Group call areas shall be predefined in the network by the service provider, co-ordinated by the network operator.

In case of a calling service subscriber initiating a VBS call, the group call area is uniquely identified by the actual cell in which the service subscriber resides at the moment of VBS call initialization and by the called group ID.

A calling dispatcher initiating a VBS call will be connected to a related predefined group call area. The entitlement of the dispatcher is checked by the network element responsible for the voice broadcast call management by verification of the calling identity. Since a dispatcher may be registered to more than one group call area and group ID an indication of the wanted group call area and group ID has to be given in form of a dedicated address called by the dispatcher.

d) Destination subscribers are all destination service subscribers or a group of destination service subscribers identified by the called group ID which have their present location in the group call area, and preregistered destination dispatchers. Destination service subscribers shall be notified with the group ID, not by paging the service subscriber individually. Destination dispatchers shall be called individually with their identity.

Service subscribers which leave the group call area during an on going VBS call cease to be destination subscribers. Service subscribers which enter the group call area during an on going VBS call shall become destination subscribers within 500 ms after reception of the first notification message related to the VBS call.

  1. The calling service subscriber shall remain within the voice broadcast call until she terminates the call, loses contact with the network or leaves the group call area. The VBS call shall be terminated by the network as soon as the network has determined that the calling service subscriber has left the VBS call area.

f) The calling service subscriber or calling dispatcher shall be informed by the network with a suitable indication about the successful establishment of the voice broadcast call so that he can start to speak.

NOTE: A successful establishment means that all broadcast downlink channels are allocated, with the restrictions mentioned in clause 6, whether somebody is listening or not, and the related dispatchers are alerted.

g) Authentication is mandatory at GSM call set up. To allow fast call set up in VBS authentication of the calling service subscriber or calling dispatcher at invocation may optionally be delayed.

Authentication of the destination subscriber, who has no uplink connection, is not required.

Confidentiality on the radio path is optional.

h) Different levels of priority and pre-emption shall be applied as defined in the corresponding stageĀ 1 description on the enhanced Multi-Level Precedence and Pre-emption service (eMLPP), TSĀ 02.67.

i) A number of voice broadcast calls may exist simultaneously intended for different groups of destination subscribers in the same group call area.

Parallel voice broadcast calls are possible to the same group of destination subscribers in different, possibly overlapping group call areas.

j) VBS shall also be provided in case of roaming. For this, certain group Ids shall be defined as supra-PLMN group Ids which have to be co-ordinated between the network operators and which shall be known in the networks and in the SIM. A service subscriber which is entitled by his subscription to establish voice broadcast calls while roaming shall only be able to use supra-PLMN group Ids in case of roaming.

k) For certain levels of priorities an acknowledgement of receipt of a voice broadcast call can be required as an application option (e.g. for railway emergency calls) from all or from nominated destination service subscribers (the nomination is recorded on the SIM). The acknowledgement itself shall be performed at the end of the voice broadcast call. The acknowledgement shall indicate the time the reception started and the time the reception terminated. The acknowledgement has to be given to a predefined recipient.

l) It shall be possible for a service subscriber to activate or deactivate the voice broadcast reception for different group Ids. The selection list is stored on the SIM corresponding to the subscribed group Ids. It shall be possible to prohibit the deactivation of group Ids used for high priority voice broadcast calls.

Mobile users that are configured as dispatchers and which are registered in the network for a certain voice broadcast call and which have also a subscription for VBS with the same group ID as the voice broadcast call for which they are dispatcher shall deactivate this group ID when they are located in the corresponding group call area in order to avoid conflicts between paging for the dispatcher and notifications for the group ID.

NOTE: VBS1, VBS2, VBS3 = particular voice broadcast calls with the attributes preregistered in the network.

A, B, C, D = service subscriber with group ID a, b, c or d, respectively.

I. II, III, IV = group call areas.

w, x, y, z = dispatchers connected via normal GSM links or external networks.

Figure 1: Logical concept of the VBS