9.1.5 Channel mode modify

3GPP44.018GSM/EDGE Radio Resource Control (RRC) protocolMobile radio interface Layer 3 specificationRelease 17TS

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

This message is sent on the main DCCH by the network to the mobile station to request the setting of the mode for the indicated channel(s). The message can be used to change the channel mode of a Multislot Configuration which only contains one channel set. See table 9.1.5.1.

Message type: CHANNEL MODE MODIFY

Significance: local

Direction: network to mobile station

Table 9.1.5.1: CHANNEL MODE MODIFY message content

IEI	Information element	Type / Reference	Presence	Format	length
	RR management Protocol Discriminator	Protocol Discriminator 10.2	M	V	1/2
	Skip Indicator	Skip Indicator 10.3.1	M	V	1/2
	Channel Mode Modify Message Type	Message Type 10.4	M	V	1
	Channel Description	Channel Description 2 10.5.2.5a	M	V	3
	Channel Mode	Channel Mode 10.5.2.6	M	V	1
01	VGCS target mode Indication	VGCS target mode Indication 10.5.2.42a	O	TLV	3
03	Multi-Rate configuration	MultiRate configuration 10.5.2.21aa	O	TLV	4-8
04	VGCS Ciphering Parameters	VGCS Ciphering Parameters 10.5.2.42b	O	TLV	3-15
6D	Extended TSC Set	Extended TSC Set 10.5.2.82	O	TV	2

9.1.5.1 Channel Description

This is sufficient to identify the channel in the case of a TCH/H + TCH/H configuration. If used for a multislot configuration, the IE shall describe the present channel configuration with TN indicating the main channel. The IE shall not indicate a new channel configuration when included in the Channel Mode Modify message.

9.1.5.2 VGCS target mode Indication

This information element is identified as "comprehension required". Only mobile stations supporting "VGCS talking" are required to accept the presence of the element. The presence of the element shall trigger an exception handling if received by a mobile station not supporting "VGCS talking".

This IE indicates which RR mode is to be used with the new channel mode (i.e. dedicated mode or group transmit mode). If this information element is not present, the RR mode shall be the same as with the previous channel mode.

When the RR mode of the new channel mode is group transmit mode, the IE also indicates the group cipher key number for the group cipher key to be used on the new channel or if the new channel is non ciphered. If the information element is not present, the ciphering mode shall be the same as with the previous channel mode.

NOTE: A mobile station supporting VGCS Talking shall not consider a syntactical error if this IE is present and the channel mode is not speech.

9.1.5.3 Multi Rate configuration

This information element appears if the Channel Mode IE indicates a multi-rate speech codec.

9.1.5.4 VGCS Ciphering Parameters

This information element is only applicable to a VGCS talker. It is only included if the assigned resource is ciphered using VGCS ciphering.

9.1.5.5 Extended TSC Set

If the message is sent to a mobile station that indicates support for extended TSC sets (see 3GPP TS 24.008 [79]) this information element may be included to provide TSC related information for the assigned radio resources. In the absence of this information element the TSC related information provided by the Channel Description 2 IE shall apply.