6 Elementary procedures for Broadcast Call Control

04.693GPPBroadcast Call Control (BCC) protocolTS

6.1 Overview

6.1.1 General

The elementary procedures may be broadcasted into the following classes:

‑ broadcast call establishment procedures;

‑ broadcast call termination procedures;

‑ broadcast call information phase procedures;

‑ miscellaneous procedures.

6.1.2 Broadcast call control states

6.1.2.1 Broadcast call control states at the MS side of the interface

The BCC entity of the MS is described as an extended finite state machine. It performs transitions between states. It has certain parameters and attributes, e.g. configuration parameters and behaviour parameters, which it sets and changes based on interaction with higher and lower (sub‑)layers and on message exchange with its peer entity. If a configuration parameter is set to a certain value, the MS shall also adapt the configuration accordingly. Behaviour parameters decide on (part of) the behaviour of the BCC entity. When the BCC entity in the MS receives a message, it shall first analyse whether it shall ignore the message, see clauses 5 and 7.

6.1.2.1.1 Attributes and Parameters of BCC in the MS

For the following behaviour parameters, the description is informative.

Parameter

Description

ORIG

Depending on the context, the MS assumes to be the originator of the call (ORIG=T) or not to be the originator of the call (ORIG=F).

COMM

Depending on the context, the MS assumes that communication with its peer entity is enabled in both directions (COMM = T) or not (COMM = F).

For the following configuration parameters the MS shall adapt its configuration according to the parameter value and parameter definition.

Parameter

Definition

D‑ATT

D‑ATT = T means that the MS attaches the user connection for the broadcast call in the downlink.

D‑ATT = F means that the MS does not attach the user connection for the broadcast call in the downlink.

U‑ATT

U‑ATT = T means that the MS attaches the user connection for the broadcast call in the uplink.

U‑ATT = F means that the MS does not attach the user connection for the broadcast call in the uplink.

6.1.2.1.2 NULL (U0)

No broadcast call exists for the BCC entity. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = F, COMM = F, D‑ATT = F, U‑ATT = F.

6.1.2.1.3 MM CONNECTION PENDING (U0.p)

The BCC entity has requested the explicit establishment of an MM connection. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = T, COMM = F, D‑ATT = F, U‑ATT = F.

6.1.2.1.4 BROADCAST CALL INITIATED (U1)

The BCC entity has requested the peer entity in the network to establish a broadcast call. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = T, COMM = T, D‑ATT = F, U‑ATT = F.

6.1.2.1.5 BROADCAST CALL ACTIVE (U2)

The broadcast call is established at least in one cell. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = T, COMM = T, D‑ATT = T, U‑ATT = T.

6.1.2.1.6 BROADCAST CALL PRESENT (U3)

The MS has received a notification about an ongoing broadcast call. Higher layers are requested to accept or reject the call. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = F, COMM = F, D‑ATT = F, U‑ATT = F.

6.1.2.1.7 BROADCAST CALL CONNECTION REQUESTED (U4)

The MS has received a notification about an ongoing broadcast call. Higher layers have decided to accept the call. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = F, COMM = F, D‑ATT = F, U‑ATT = F.

6.1.2.1.8 TERMINATION REQUESTED (U5)

The MS which is the originator of the broadcast call has been in state U1 or U2 and has sent a TERMINATION REQUEST message to the network. When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = T, COMM = T, D‑ATT = T, U‑ATT = T.

6.1.2.1.9 RECEIVE MODE ACTIVE (U6)

The BCC entity in the MS in state U4, BROADCAST call connection requested, has got an indication from lower (sub‑)layers that RR has entered group receive mode (see GSM 04.08). When entering the state, parameters shall be set to the following values, and configuration shall be adapted to the new values of configuration parameters: ORIG = F, COMM = F, D‑ATT = T, U‑ATT = F.

6.1.2.1.10 BCC TIMERS IN THE MS

Table 6.1 specifies the timers used in BCC. The denotation of columns is defined as follows:

timer ::= name of the timer;

set ::= under which conditions the timer is set (i.e., started);

stopped ::= under which conditions the timer is stopped;

running in state(s) ::= in which state(s) the timer may be running;

action at expiry ::= which actions the BCC entity shall perform at expiry;

value ::= the duration between setting the timer and expiry of the timer ("s" denotes

"second(s)" "xx ‑ yy" means that any value between xx and yy is permitted).

Table 6.1: Specification of timers used in BCC

timer

set

stopped

running in state(s)

action at expiry

value

Tno channel

in state U6 on receipt of an indication from lower (sub‑)layers that no channel is currently available

when leaving U6 or when receiving in U6 an indication from lower (sub‑)layers that a channel is available

in U6, depending on further conditions

see subclause 6.3.1

3 s

TMM‑est

when entering U0.p using the set‑up procedure

when entering U1 using the immediate set‑up procedure

when leaving U0.p or U1

U0.p, U1

see subclause 6.2.1

5 s

Tterm

when sending a TERMINATION REQUEST

when receiving a TERMINATION or TERMINATION REJECT

U5

abort broadcast call

10 s

Tconn req

when entering state U4

when leaving state U4

U4

abort broadcast call

10‑30 s

6.1.2.1.11 CONSISTENCY OF PARAMETERS AND STATES

The MS shall consider the following parameter values as inconsistent with the state or sub‑state:

ORIG = T is inconsistent with states U3, U4, and U6.

COMM = T is inconsistent with states U0, U3, U4, and U6.

All other values of parameters ORIG, COMM, D‑ATT, and U‑ATT shall not be considered by the MS as inconsistent with a state.

6.1.2.2 BROADCAST CALL CONTROL STATES AT THE NETWORK SIDE OF THE INTERFACE

6.1.2.2.1 NULL (State N0)

No broadcast call exists for the BCC entity.

6.1.2.2.2 BROADCAST CALL INITIATED (N1)

The BCC entity has received the indication that a peer entity in a MS wants to establish a broadcast call for a certain broadcast identity.

6.1.2.2.3 BROADCAST CALL ACTIVE (N2)

The broadcast call is established in at least one cell; there may be a MS which has seized the uplink or not; there may be talking dispatchers or not.

6.1.2.2.4 BROADCAST CALL ESTABLISHMENT PROCEEDING (N3)

The BCC entity wants to accept the broadcast call, has initiated establishment of corresponding broadcast call channels, and, if there is a calling user. has sent a CONNECT message to the calling user.

6.1.2.2.5 TERMINATION REQUESTED (N4)

The BCC entity has asked lower sub‑layers to terminate the broadcast call in all cells and waits for a confirmation that the broadcast call has been terminated in all cells.

6.2 Procedures for establishment of a broadcast call

6.2.1 Activation of a broadcast call by the network

The BCC entity in the network may initiate the activation of a broadcast call with a certain broadcast call reference and priority in a list of cells by asking lower layers to establish the broadcast call with that broadcast call reference and priority in those cells. It then waits until it is informed by lower (sub‑)layers that resource activation was sufficiently successful, and enters state N2, BC ACTIVE,

6.2.2 Mobile originated establishment

Higher layers in the MS may ask the BCC entity in state U0, NULL, to establish a broadcast call, either using the immediate set‑up procedure or using the set‑up procedure. The request contains a group‑id and may contain a priority indication.

On request of higher layers to establish a broadcast call using the set‑up procedure, the BCC entity of the MS builds an appropriate SETUP message and asks lower (sub‑)layers to establish an MM connection explicitly (i.e. by use of a CM SERVICE REQUEST message) and to transmit the SETUP message. It then enters state U0.p, MM CONNECTION PENDING. In state U0.p, when informed by lower sub‑layers that an MM connection has been established, the BCC entity in the MS shall stop timer TMM‑est and enter state U1, BC INITIATED.

On request of higher layers to establish a broadcast call using the immediate set‑up procedure, the BCC entity of the MS builds an appropriate IMMEDIATE SETUP message and asks lower (sub‑)layers to establish an MM connection implicitly (see GSM 04.08) and to transmit the IMMEDIATE SETUP message. It sets timer TMM‑est and then enters state U1, BC INITIATED.

The network BCC entity in state NULL may receive a set‑up message from its peer entity in the originating MS. This set‑up message is either a SETUP message or an IMMEDIATE SETUP message. The network enters state N1, BC INITIATED.

In state N1, the network decides whether:

a) the establishment is accepted; or

b) the establishment rejected.

In case a), the BCC entity in the network considers the peer entity in the MS having sent the set‑up message to be the calling user and asks lower layers to activate the appropriate resources. It then:

1) waits until it is informed by lower (sub‑)layers that resource activation was sufficiently successful, then sends a CONNECT message to the calling user, and enters state N2, BC ACTIVE; or

2) sends a CONNECT message to the calling user and enters N3, BC ESTABLISHMENT PROCEEDING. In state N3, the BCC entity is informed by lower layers whenever the status of resources for the broadcast call is changed. When informed that activation of resources was sufficiently successful, the BCC entity in the network enters state N2, ACTIVE.

The CONNECT message specifies the broadcast call reference of the broadcast call and indicates that the MS is the originator of the broadcast call.

In case b), the further proceeding is as defined in subclause 6.2.2.1.

In state U0.p or U1, the BCC entity in the MS shall, on receipt of a CONNECT message, establish the conditions defined for state U2, ACTIVE and the suitable sub‑state (see subclause 6.1.2.1), stop timer TMM‑est (if running) and enter state U2, ACTIVE. If the immediate set‑up procedure has been used, the BCC entity in the MS shall inform lower sub‑layers that the MM connection has been implicitly established.

6.2.2.1 Termination during mobile originated establishment

At any time during the mobile originated establishment of a broadcast call, the network may decide to terminate the connection between the two peer entities in the network and MS. In this case the network sends a TERMINATION message to the MS specifying the appropriate cause; it may ask lower (sub‑)layers to release associated resources. The further actions are specified in subclause 6.4.

During mobile originated establishment of a broadcast call, the MS may abort the broadcast call, see subclause 6.4.

6.2.2.2 Abnormal cases

At expiry of TMM‑est, or radio link failure (see GSM 04.08), the BCC entity in the MS requests lower sub‑layers to abort the MM connection establishment and returns to state U0, NULL(this includes clearing of the context related to the broadcast call establishment).

On receipt of an indication of lower sub‑layers that the MM connection establishment was unsuccessful, the BCC entity in the MS returns to state U0, NULL (this includes clearing of the context related to the broadcast call establishment).

6.2.3 Mobile terminating broadcast call establishment in the MS

The BCC entity in the MS, being in state U0, NULL, may receive an indication of lower layers that a broadcast call exists. This indication specifies the broadcast‑id and a priority. It shall then inform higher layers and enter state U3, BC present. This state may be supervised by a timer at expiry of which the BCC entity clears the context and returns to state U0, NULL.

In state U3, on request of higher layers to join the broadcast call, the BCC entity in the MS stops any running timer, asks lower sub‑layers to join the broadcast call, starts timer Tconn req, and enters state U4, BC CONNECTION REQUESTED.

In state U4, on indication of lower sub‑layers that the broadcast call has been joint (this indication specifies the mode of the RR connection), the BCC entity in the MS stops any running timer, enters state U6, RECEIVE MODE ACTIVE, establishes the appropriate configurations (see subclause 6.1) and informs higher layers (this includes information about the sub‑state).

6.3 Procedures during the active state and receive mode active state of a broadcast call

6.3.1 Mobile station procedures in the active state

In the active state, the BCC entity in the MS performs, on receipt of messages from its peer entity, on request of higher layers, and on indication of lower sub‑layers, actions as defined below.

On request of higher layers, the MS initiates abort or termination of the broadcast call, see subclause 6.4.

If the network initiates broadcast call abortion or termination, the MS reacts as specified in subclause 6.4.

On radio link failure, the MS aborts the broadcast call, see subclause 6.4.

6.3.2 Network procedures in the active state

In the active state the BCC entity in the network performs supervisory functions, maintenance functions and resource modifications which are not further specified. (This includes through‑connection of the application data stream(s), which is defined in GSM 03.69).

The network may initiate abort or termination of the broadcast call, see subclause 6.4.

If the MS initiates broadcast call abortion or termination, the network reacts as specified in subclause 6.4.

The network may send a SET PARAMETER message to the MS in order to ask the MS to set parameters to certain values and to take consequential actions.

6.3.3 Mobile station procedures in the RECEIVE MODE ACTIVE state

In state U6, RECEIVE MODE ACTIVE, the BCC entity in the MS performs, on receipt of messages from its peer entity, on request of higher layers, and on indication of lower sub‑layers, actions as defined below.

On request of higher layers, the MS initiates abort of the broadcast call, see subclause 6.4.

If the network initiates broadcast call abortion or termination, the MS reacts as specified in subclause 6.4.

Upon indication from lower layers that no channel is available, the BCC entity in the MS informs higher layers and starts timer Tno channel. Then:

if Tno channel expires, the BCC entity in the MS informs higher layers, asks lower sub‑layers to abort resources and enters the idle state

upon indication from lower layers that a channel is available, the BCC entity in the MS informs higher layers and stops timer Tno channel.

6.4 Procedures for release, abortion, and termination of a broadcast call

6.4.1 Termination procedure

The MS being the originator of the broadcast call (ORIG = T) shall, on request of higher layers,

initiate the termination procedure by sending a TERMINATION REQUEST message to its peer entity in the network and setting timer Tterm.

The network either accepts the termination by sending a TERMINATION or rejects termination by sending a TERMINATION REJECT. These messages indicate an appropriate cause.

In state U5, on receipt of a TERMINATION REJECT message, the BCC entity in the MS informs higher layers and stops Tterm.

In state U5, on Tterm expiry, the BCC entity in the MS informs higher layers, asks lower sub‑layers to abort the broadcast call, clears the context related to the broadcast call, and returns to state U0, NULL.

In any state, on receipt of a TERMINATION message, the BCC entity in the MS informs higher layers, asks lower sub‑layers to release the broadcast call, clears the context related to the broadcast call, and returns to state U0, NULL.

At any time during a broadcast call, the network may decide to terminate the connection between the two peer entities in the network and MS. In this case the network sends a TERMINATION message to the MS specifying the appropriate cause; it may ask lower (sub‑)layers to release associated resources. The further actions are specified above in this subclause 6.4.

6.4.2 Abort and release procedures

The network may ask lower sub‑layers to abort or release the broadcast call. The MS will detect abort of the broadcast call by detecting the abort of RR resources, and a broadcast call release by detecting the release of RR resources. The BCC entity in the MS shall then inform higher layers, ask lower sub‑layers to abort the broadcast call, clear the context related to the broadcast call, and return to state U0, NULL.

The MS shall, on request of higher layers, initiate the release procedure by asking lower sub‑layers to release the broadcast call, clearing the context related to the broadcast call, and returning to state U0, NULL.

The BCC entity in the MS shall when required by the BCC protocol, abort the broadcast call by requesting lower layers to abort the broadcast call, informing higher layers, clearing the context related to the broadcast call, and returning to state U0, NULL.

6.5 Miscellaneous procedures

6.5.1 Status procedures

6.5.1.1 Get status procedure

Upon receipt of a GET STATUS message, the MS shall:

‑ if COMM = T, respond with a STATUS message, reporting the current call state, the current values of configuration and behaviour parameters and cause value # 30 "Response to GET STATUS";

‑ if COMM = F, ignore the message.

6.5.1.2 Set parameter procedure

Upon receipt of a SET PARAMETER message the MS shall set the parameters to the indicated values and the configuration shall be adapted to the new values of configuration parameters, if they are consistent with the current BCC state and sub‑state (see subclause 6.1.2). If they are not:

‑ if COMM , before the message was received, is equal to T, it shall send a STATUS message specifying error cause "message incompatible with protocol state", the state and, if applicable, sub‑state, and the state attributes IE;

‑ if COMM , before the message was received, is equal to F, it shall ignore the message.