9.1.2 Assignment command

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 change the channel configuration to another independent dedicated channel configuration, when no timing adjustment is needed. See table 9.1.2.1.

Message type: ASSIGNMENT COMMAND

Significance: dual

Direction: network to mobile station

Table 9.1.2.1: ASSIGNMENT COMMAND message content

IEI	Information element	Type / Reference	Presence	Format	length
	RR management Protocol Discriminator	Protocol Discriminator 10.2	M	V	½
	Skip Indicator	Skip Indicator 10.3.1	M	V	½
	Assignment command Message Type	Message Type 10.4	M	V	1
	Description of the First Channel, after time	Channel Description 2 10.5.2.5a	M	V	3
	Power Command	Power Command 10.5.2.28	M	V	1
05	Frequency List, after time	Frequency List 10.5.2.13	C	TLV	4-132
62	Cell Channel Description	Cell Channel Description 10.5.2.1b	O	TV	17
10	Description of the multislot configuration	Multislot Allocation 10.5.2.21b	C	TLV	3-12
63	Mode of the First Channel (Channel Set 1)	Channel Mode 10.5.2.6	O	TV	2
11	Mode of Channel Set 2	Channel Mode 10.5.2.6	O	TV	2
13	Mode of Channel Set 3	Channel Mode 10.5.2.6	O	TV	2
14	Mode of Channel Set 4	Channel Mode 10.5.2.6	O	TV	2
15	Mode of Channel Set 5	Channel Mode 10.5.2.6	O	TV	2
16	Mode of Channel Set 6	Channel Mode 10.5.2.6	O	TV	2
17	Mode of Channel Set 7	Channel Mode 10.5.2.6	O	TV	2
18	Mode of Channel Set 8	Channel Mode 10.5.2.6	O	TV	2
64	Description of the Second Channel, after time	Channel Description 10.5.2.5	O	TV	4
66	Mode of the Second Channel	Channel Mode 2 10.5.2.7	O	TV	2
72	Mobile Allocation, after time	Mobile Allocation 10.5.2.21	C	TLV	3-10
7C	Starting Time	Starting Time 10.5.2.38	O	TV	3
19	Frequency List, before time	Frequency List 10.5.2.13	C	TLV	4-132
1C	Description of the First Channel, before time	Channel Description 2 10.5.2.5a	O	TV	4
1D	Description of the Second Channel, before time	Channel Description 10.5.2.5	O	TV	4
1E	Frequency channel sequence before time	Frequency channel sequence 10.5.2.12	C	TV	10
21	Mobile Allocation, before time	Mobile Allocation 10.5.2.21	C	TLV	3-10
9-	Cipher Mode Setting	Cipher Mode Setting 10.5.2.9	O	TV	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, after time	Extended TSC Set 10.5.2.82	O	TV	2
6E	Extended TSC Set, before time	Extended TSC Set 10.5.2.82	O	TV	2

9.1.2.1 Mode of the First Channel (Channel Set 1) and Mode of Channel Set "X" (2=<X=<8)

If this information element is not present the channel mode of the previously allocated channel or channels for Channel Set "X" (1=<X<=8) shall be assumed.

If Channel Set "X" is not defined for the configuration, the Mode of Channel Set "X" IE shall be considered as an IE unnecessary in the message.

NOTE: Sub-clause 3.4.3.1 defines cases when one or several Mode of Channel Set "X" IEs shall be included in the message.

9.1.2.2 Description of the Second Channel

These information elements appear in the case of an assignment occurring if the mobile station carries two connections (on two dedicated channels, for the TCH/H + TCH/H configuration).

The connection using the channel previously defined in the Description of the First Channel IEs of an ASSIGNMENT COMMAND or HANDOVER COMMAND message shall use the channel defined in the Description of the First Channel IEs of the ASSIGNMENT COMMAND message defining the new configuration.

The channel described in the Description of the First Channel IEs carries the main DCCH. The SACCH used is the one associated with that channel.

9.1.2.3 Mode of the Second Channel

If no Description of the Second Channel IE is present but the information element is present it shall be considered as an IE unnecessary in the message.

This information element appears at least when the channel mode is changed for the channel defined in the second channel description information elements.

9.1.2.4 Mobile Allocation and Frequency List, after the starting time

If at least one of the channel descriptions for the starting time indicates frequency hopping, one and only one of the following information elements shall be present and apply to all assigned channels:

– Mobile Allocation, after time;

– Frequency List, after time.

If neither of the Channel Description IEs for after time indicate frequency hopping, if decoding of Channel Description IEs for before time does not require a frequency list for after time (see next sub-clause), and one or both of the two information elements are present they shall be considered as IEs unnecessary in the message.

9.1.2.5 Starting Time

The starting time information element is included when the network wants the mobile station to change the frequency parameters of the channels more or less at the moment a change of channel occurs. In this case a number of information elements may be included to give the frequency parameters to be used before the starting time.

If the starting time information element is present and none of the information elements referring to before the starting time are present, the mobile station waits and accesses the channels at the indicated time.

If the starting time information element is present and at least one of the information elements referring to before the starting time is present, the mobile station does not wait for the indicated time and accesses the channel using the frequency parameters for before the starting time.

If the starting time information element is not present and at some of the information elements referring to before the starting time is present, these information elements shall be considered as IEs unnecessary in the message.

If the description of the first channel, before time IE is not present, the channel description to apply for before the time, if needed, is given by the description of the first channel, after time IE.

If the description of the second channel, after time IE is present, the description of the second channel, before time IE not present, and a description of the configuration for before the time needed, the channel configuration before the starting time is nevertheless of two traffic channels, and the channel description to apply to the second channel before the starting time is given by the description of the second channel, after time IE.

If the starting time IE is present and at least one of the channel descriptions for before the starting time indicates frequency hopping, one and only one of the following information elements may be present and applies before the starting time to all assigned channels:

– Mobile Allocation, before time IE;

– Frequency list, before time IE;

– Frequency channel sequence, before time IE.

If the starting time IE is present and at least one of the channel descriptions for before the starting time indicates frequency hopping, and none of the above mentioned IE is present, a frequency list for after the starting time must be present (see sub-clause 9.1.2.4), and this list applies also for the channels before the starting time.

9.1.2.6 Reference cell frequency list

If any of the mobile allocation information elements is present, then the network must ensure that either the mobile station has received in a previous message the proper reference cell frequency list (CA), or that the cell channel description IE is present.

If the cell channel description IE is present, it is used to decode the mobile allocation IEs in the message, as well as in later messages until reception of a new reference cell frequency list or the cell is left.

9.1.2.7 Cell Channel Description

If present, this information element shall be used to decode the Mobile Allocation IE in the same message and in subsequent messages.

9.1.2.8 Cipher Mode Setting

If this information element is omitted, the mode of ciphering is not changed after the mobile station has switched to the assigned channel.

Only applicable for mobile stations supporting VGCS talking:

– The cipher mode setting IE shall not be included if the ASSIGNMENT COMMAND message is sent on a VGCS channel or dedicated channel in order to assign a VGCS channel.

– The cipher mode setting IE shall be included if the ASSIGNMENT COMMAND message is sent on a ciphered VGCS channel in order to assign a dedicated channel. If the information element is not present, the MS shall use ciphering mode "no ciphering" on the assigned channel.

9.1.2.9 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 mode is to be used on the new channel (i.e. dedicated mode or group transmit mode). If this information element is not present, the mode shall be the same as on the previous channel.

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 on the previous channel.

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

9.1.2.10 Description of the multislot allocation

This information element is included if so indicated by the channel type and TDMA offset field in the Channel Description information element and is used to assign channels that do not carry a main signalling link in a multislot configuration. It indicates how the used timeslots are divided into separate channel sets.

If the Channel Description IE does not require the presence of the information element the Description of the multislot allocation IE shall be considered as an IE unnecessary in the message.

If multislot configuration is indicated by the Channel Description IE but the Multislot Allocation IE is not present, all channels in the configuration belong to one channel set, "Channel Set 1".

NOTE: As a change of timeslot number cannot occur for the channel described after the starting time, the Multislot Allocation IE does not have to be included more than once.

9.1.2.11 Multi Rate configuration

This information element appears if the Mode of the First Channel indicates a multi-rate speech codec, and if the assigned configuration is new, i.e. it is different from the MultiRateconfiguration of a previously allocated channel in the cell.

9.1.2.12 VGCS Ciphering Parameters

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

9.1.2.13 Extended TSC Set, after time

9.1.2.14 Extended TSC Set, before time

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 Description of the First Channel, before time IE shall apply. If the Description of the First Channel, before time IE is not present, the TSC related information to apply for before the time, if needed, is given by the Extended TSC Set, after time IE.