5 Main concepts

04.693GPPBroadcast Call Control (BCC) protocolTS

The present document describes the broadcast call control (BCC) protocol, which is one of the protocols of the Connection Management (CM) sublayer (see GSM 04.07).

There is in general more than one MS engaged in a broadcast call. Consequently, there is in general more than one MS with a BCC entity engaged in the same broadcast call, and there is one BCC entity in the network engaged in that broadcast call.

Under which conditions a BCC message is passed from lower (sub‑)layers to the BCC entity is defined in the specifications of the sub‑layers.

The MS shall ignore BCC messages that it receives which were sent in unacknowledged mode and which explicitly specify as destination a mobile identity which is not a mobile identity of the MS.

Higher layers and the MM sub‑layer decide when to accept parallel BCC transactions and when/whether to accept BCC transactions in parallel to other CM transactions.

The broadcast call may be initiated by a mobile user or by a dispatcher. Specification of a protocol for dispatchers is out of the scope of the present document. Hence, in the scope of the present document, there are:

‑ one BCC entity in the network; and

‑ one or more than one BCC entities in different MSs;

engaged in a broadcast call, and one ore none of the MSs is the originator of the broadcast call (called the originating MS in the present document).

NOTE: Whereas for the Group Call Control (GCC) protocol (see GSM 04.68), in certain situations, the GCC entity in a MS assumes to be the originator of a broadcast call without being the originator, this is not the case for the BCC protocol.

The originator of the BCC transaction chooses the Transaction Identifier (TI). A MS not assuming to be the originator of the transaction will chose the transaction identifier received from the network, setting the TI flag to 1+x mod 2 where x is the received TI flag.

The present document describes the broadcast call control protocol only with regard to two peer entities, one in a MS, the other one in the network. The call control entities are described as communicating finite state machines which exchange messages across the radio interface and communicate internally with other protocol (sub)layers. In particular, the BCC protocol uses the MM and RR sublayer specified in GSM 04.08. The BCC entity in a MS that is not the originator of the broadcast call shall not send messages to its peer entity. This description in only normative as far as the consequential externally observable behaviour is concerned. For simplicity, instead of using the terms "BCC entity in the MS" and "BCC entity in the network", the present document often uses the terms "MS" and "network" if no confusion may arise.

Certain sequences of actions of the two peer entities compose "elementary procedures" which are used as a basis for the description in the present document. These elementary procedures are defined in clause 6.

The network should apply supervisory functions to verify that the BCC procedures are progressing and if not, take appropriate means to resolve the problems. This, however, is out of the scope of the present document.