8 Message functional definitions and contents

3GPP44.068Group Call Control (GCC) protocolRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

This subclause defines the structure of the messages of those layer 3 protocols defined in the present document, that is the GCC protocol.

All messages are standard L3 messages as defined in 3GPP TS 24.007.

Each definition given in the present subclause includes:

– a brief description of the message direction and use;

– a definition in which direction the message is defined;

– a table listing the information elements permitted to be in that message and their order of their appearance in the message. All information elements that may be repeated are explicitly indicated. Neither the network nor the MS is allowed to include information elements in a message which are not specified for the message or to include the information elements in the message in an order different from the specified order. ( V and LV formatted IEs, which compose the imperative part of the message, occur before T, TV, and TLV formatted IEs which compose the non-imperative part of the message, cf. 3GPP TS 24.007.) In a (maximal) sequence of consecutive information elements with half octet length, the first information element with half octet length occupies bits 1 to 4 of octet N, the second bits 5 to 8 of octet N, the third bits 1 to 4 of octet N+1 etc. Such a sequence always has an even number of elements.

For each information element the table indicates:

1) if the IE has format T, TV, or TLV, the IEI used by the IE at the indicated position in the message, in hexadecimal notation. If the IEI has half octet length, this is specified by a notation representing the IEI as a hexadecimal digit followed by a "-" (example: B-);

2) the name of the information element (which may give an idea of the semantics of the element). The name of the information element (usually written in italics) followed by "IE" or "information element" is used in 3GPP TS 24.008 as reference to the information element within a message;

3) the name of the type of the information element (which indicates the coding of the value part of the IE), and generally, the referenced subclause of clause 9 describing the value part of the information element;

4) the presence requirement indication (M or O) for the IE as defined in 3GPP TS 24.007 (Presence requirement indication C is not used in the present document);

5) the format of the information element (T, V, TV, LV, TLV) as defined in 3GPP TS 24.007;

6) the length of the information element (or permissible range of lengths), in octets, in the message. This indication is normative. However, further restrictions to the length of an IE may be specified elsewhere.

subclauses specifying, where appropriate;

– the meaning of; and

– conditions for;

absence, repeated occurrence, and/or presence for IEs with presence requirement O in the relevant message which together with other conditions specified in the present document define when the information elements shall be included or not, what presence, repeated occurrence, and absence of such IEs means.

Table 8.1 summarizes the messages for GCC. A letter D ("downlink") specifies that the message is defined in the direction network to mobile station, a letter U ("uplink") specifies that the message is defined in the direction mobile station to network.

Message Reference Direction

DATA 8.1 D,U
IMMediate Setup 8.2 no
RELEASE COMPLETE 8.3 D,U U
SETUP 8.4 D,U
SETUP ACKNOWLEDGE 8.5 D,U
RESUME 8.6 U
RESUME ACK 8.7 D

STATUS 8.8 D,U

Table 8.1

Messages for GCC

8.1 CONNECT

This message is sent by the network to the calling MS in order to indicate establishment of the requested group call.

See table 8.1.

Message type: CONNECT;

Significance: dual;

Direction: network to MS.

Table 8.1: CONNECT message content

IEI	Information element	Type / Reference	Presence	Format	Length
	Group Call control protocol discriminator	Protocol discriminator subclause 9.1	M	V	1/2
	Transaction identifier	Transaction identifier subclause 9.2	M	V	1/2
	Connect message type	Message type subclause 9.3	M	V	1
	Group call reference	Call reference subclause 9.4.1	M	V	4
	Originator indication	Originator indication subclause 9.4.4	M	V	1/2
	Talker priority used	Talker priority subclause 9.4.9	M	V	1/2
D-	SMS indications	SMS indications subclause 9.4.10	O	TV	1

8.1.1 SMS indications

This IE shall be included if the network supports the transfer of mobile originated point-to-point short messages via the group call channel. If this IE is not received the MS shall assume the default settings “SMS guaranteed privacy required” and “SMS data confidentiality required”.

8.2 GET STATUS

This message is sent by the network at any time to solicit a STATUS message from the MS in acknowledged or unacknowledged mode.

See table 8.2.

Message type: GET STATUS;

Significance: local;

Direction: network to MS.

Table 8.2: GET STATUS message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
17	mobile identity	mobile identity 3GPP TS 24.008, subclause 10.5.1.4	O	TLV	3‑10

8.2.1 mobile identity

This IE is included if the network wishes so. If the message is received by the MS in acknowledged mode, it shall be ignored by the MS. If received in unacknowledged mode, it specifies the destination MS, see clause 5.

8.3 IMMEDIATE SETUP

This message is sent by the MS to the network in order to set-up a group call immediately, i.e. without previous establishment of an MM connection. See table 8.3.

Message type: IMMEDIATE SETUP;

Significance: dual;

Direction: MS to network.

Table 8.3: IMMEDIATE SETUP message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	Talker priority requested	Talker priority subclause 9.4.9	M	V	1/2
	Ciphering key sequence number	Ciphering key sequence number 3GPP TS 24.008, subclause 10.5.1.2	M	V	1/2
	Mobile station classmark	Mobile station classmark 2 3GPP TS 24.008, subclause 10.5.1.6	M	LV	4
	Mobile identity	Mobile identity 3GPP TS 24.008, subclause 10.5.1.4	M	LV	2‑9
	Group identity	Call reference subclause 9.4.1	M	V	4

8.3.1 Mobile identity

This IE shall specify the TMSI, if available, and the IMSI else.

8.3a IMMEDIATE SETUP 2

This message is sent by the MS to the network in order to set-up a group call immediately, i.e. without previous establishment of an MM connection, and to include compressed originator-to dispatcher information. The message shall only be used if the MS has a valid TMSI. See table 8.3a.

Message type: IMMEDIATE SETUP 2;

Significance: dual

Direction: MS to network.

Table 8.3a: IMMEDIATE SETUP 2 message content

IEI	Information element	Type / Reference	Presence	Format	Length
	Protocol discriminator	Protocol discriminator subclause 9.1	M	V	1/2
	Transaction identifier	Transaction identifier subclause 9.2	M	V	1/2
	Message type	Message type subclause 9.3	M	V	1
	Talker priority requested	Talker priority subclause 9.4.9	M	V	1/2
	Ciphering key sequence number	Ciphering key sequence number 3GPP TS 24.008, subclause 10.5.1.2	M	V	1/2
	Mobile station classmark	Mobile station classmark 2 3GPP TS 24.008, subclause 10.5.1.6	M	LV	4
	TMSI	TMSI/P-TMSI 3GPP TS 44.018, subclause 10.5.2.42	M	V	4
	Group identity	Call reference subclause 9.4.1	M	V	4
	Compressed otdi	Compressed otdi subclause 9.4.8	M	V	5

8.3a.1 TMSI

The TMSI information element indicates the Temporary Mobile Subscriber Identity of the MS.

8.3a.2 Compressed otdi

This information element contains compressed originator-to-dispatcher information.

8.4. SET PARAMETER

This message is sent by the network at any time to ask the MS for setting of parameters and consequential actions. See table 8.4.

Message type: SET PARAMETER;

Significance: local;

Direction: network to MS.

Table 8.4: SET PARAMETER message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	state attributes	state attributes subclause 9.4.7	M	V	1/2
	spare half octet	spare half octet subclause 9.4.6	M	V	1/2

8.5 SETUP

This message is sent by the MS to the network in order to set-up a group call after establishment of an MM connection. See table 8.5.

Message type: SETUP;

Significance: dual;

Direction: MS to network.

Table 8.5: SETUP message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	Group identity	Call reference subclause 9.4.1	M	V	4
7E	Originator-to-dispatcher information	User-user 3GPP TS 24.008 subclause 10.5.4.25	O	TLV	3 – 35
C-	Talker priority requested	Talker priority subclause 9.4.9	O	TV	1

8.5.1 Originator-to-dispatcher information

The Originator-to-dispatcher IE specifies originator-to-dispatcher information. The coding of the IE is equal to the coding of User-user information defined in 3GPP TS 24.008 subclause 10.5.4.25.

8.5.2 Talker priority requested

This information element shall be included in the message, if the talker priority requested by the subscriber is higher than "normal priority" and the subscriber is allowed to use the requested talker priority for the respective group identity.

8.6 STATUS

This message is sent by the MS to the network at any time during a call to report certain error conditions listed in clause 8. It shall also be sent in response to a GET STATUS message. See table 8.6.

Message type: STATUS;

Significance: local;

Direction: MS to network.

Table 8.6: STATUS message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	cause	cause subclause 9.4.3	M	LV	2 ‑ 248
A-	call state	call state subclause 9.4.2	O	TV	1
B-	state attributes	state attributes subclause 9.4.7	O	TV	1

8.6.1 Call state

This IE may always be included in the message. In certain cases identified in the present document, the IE shall be included in the message, e.g.: when used in the get status procedure.

8.6.2 State attributes

This IE may always be included in the message. In certain cases identified in the present document, the IE shall be included in the message, e.g.: when used in the get status procedure.

8.7 TERMINATION

This message is sent by the network to the MS in order to indicate that the group call has been or will be terminated, e.g. as a response to a termination request. See table 8.7.

Message type: TERMINATION;

Significance: dual;

Direction: network to MS.

Table 8.7: TERMINATION message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	cause	cause subclause 9.4.3	M	LV	2 ‑ 248

8.8 TERMINATION REJECT

This message is sent by the network to the MS in order to reject a termination request, for example because the MS is not the originator of the group call. See table 8.8.

Message type: TERMINATION REJECT;

Significance: dual;

Direction: network to MS.

Table 8.8: TERMINATION REJECT message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	Reject cause	Cause subclause 9.4.3	M	LV	2 – 248

8.9 TERMINATION REQUEST

This message is sent by the MS to the network in order to request termination of a group call which it had originated. See table 8.9.

Message type: TERMINATION REQUEST;

Significance: dual;

Direction: MS to network.

Table 8.9: TERMINATION REQUEST message content

IEI	Information element	Type / Reference	Presence	Format	Length
	protocol discriminator	protocol discriminator subclause 9.1	M	V	1/2
	transaction identifier	transaction identifier subclause 9.2	M	V	1/2
	message type	message type subclause 9.3	M	V	1
	Group call reference	Call reference subclause 9.4.1	M	V	4
C-	Talker priority	Talker priority subclause 9.4.9	O	TV	1

8.9.1 Talker priority

This information element shall be included in the message if the subscriber obtained the uplink with a priority higher than "normal priority".