9.1.15 Handover 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 dedicated channel configuration, timing adjustment needed. See table 9.1.15.1.

Message type: HANDOVER COMMAND

Significance: dual

Direction: network to mobile station

Table 9.1.15.1: HANDOVER COMMAND 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
	Handover Command Message Type	Message Type 10.4	M	V	1
	Cell Description	Cell description 10.5.2.2	M	V	2
	Description of the first channel, after time	Channel Description 2 10.5.2.5a	M	V	3
	Handover Reference	Handover Reference 10.5.2.15	M	V	1
	Power Command and Access type	Power Command and Access type 10.5.2.28a	M	V	1
D-	Synchronization Indication	Synchronization Indication 10.5.2.39	O	TV	1
02	Frequency Short List, after time	Frequency Short List 10.5.2.14	C	TV	10
05	Frequency List, after time	Frequency List 10.5.2.13	C	TLV	4-131
62	Cell Channel Description	Cell Channel Description 10.5.2.1b	C	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
69	Frequency Channel Sequence, after time	Frequency Channel Sequence 10.5.2.12	C	TV	10
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
7B	Real Time Difference	Time Difference 10.5.2.41	C	TLV	3
7D	Timing Advance	Timing Advance 10.5.2.40	C	TV	2
12	Frequency Short List, before time	Frequency Short List 10.5.2.14	C	TV	10
19	Frequency List, before time	Frequency List 10.5.2.13	C	TLV	4-131
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
76	Dynamic ARFCN Mapping	Dynamic ARFCN Mapping 10.5.2.11b	O	TLV	6-34
04	VGCS Ciphering Parameters	VGCS Ciphering Parameters 10.5.2.42b	O	TLV	3-15
51	Dedicated Service Information	Dedicated Service Information 10.5.2.59	O	TV	2
A-	PLMN Index	PLMN Index 10.5.2.81	O	TV	1
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

9.1.15.1 Synchronization Indication

If this information element does not appear, the assumed value is "non-synchronized".

9.1.15.2 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 3.4.4.1 defines cases when one or several Mode of Channel Set "X" IEs shall be included in the message.

9.1.15.3 Description of the Second Channel

These information element appear 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 IE of an ASSIGNMENT COMMAND or HANDOVER COMMAND message shall use the channel defined in the first channel description IE of the HANDOVER COMMAND message defining the new configuration.

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

9.1.15.4 Mode of the Second Channel

If the Description of the Second Channel IE is not present and the information element is present it shall be considered as an IE unnecessary in the message.

This element appears at least when the channel mode is changed for the channel defined in the Description of the Second Channel information element.

9.1.15.5 Frequency Channel Sequence, Frequency List, Frequency short list and Mobile Allocation, after time.

If at least one of the channel descriptions for after time indicates frequency hopping, one and only one of the following information elements shall be present:

– Frequency Channel Sequence, after time;

– Frequency list, after time;

– Frequency Short List, after time;

– Mobile Allocation, after time.

If neither of the Channel Description IEs indicate frequency hopping, if they are not required for the decoding of Channel Description IEs for before time, and if any of the four information elements are present they shall be considered as IEs unnecessary in the message.

The Frequency Channel Sequence information element shall not be used unless all the ARFCNs that it indicates are in the P-GSM band.

9.1.15.6 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.

The starting time information element refers to the new cell 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 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 Short list, 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.

9.1.15.7 Reference cell frequency list

If any of the mobile allocation information elements is present, then the cell channel description IE must be present. It is used to decode the mobile allocation IEs in the message.

In addition, if no information elements pertaining to before the starting time is present in the message, the frequency list defined by the cell channel description IE is used to decode the mobile allocation IEs in later messages received in the new cell until reception of a new reference cell frequency list or the new cell is left.

9.1.15.8 Real Time Difference

This information element shall appear if the Synchronization Indication information element indicates a pseudo-synchronous handover otherwise it shall be considered as an unnecessary information element.

9.1.15.9 Timing Advance

This information element shall appear if the "synchronization indication" element indicates a presynchronized handover. If not included for a presynchronized handover, then the default value as defined in 3GPP TS 45.010 shall be used. For other types of handover it shall be considered as an unnecessary information element.

9.1.15.10 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.

In the case of inter-RAT or inter-mode handover to GERAN A/Gb mode, the HANDOVER COMMAND message shall always contain the cipher mode setting IE (see sub-clause 3.4.4.1).

Only applicable for mobile stations supporting VGCS talking:

The cipher mode setting IE shall not be included if the HANDOVER COMMAND message is sent on a VGCS channel or on a dedicated channel for a handover to a VGCS channel.

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

9.1.15.11 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 if this IE is present and the channel mode is not speech.

9.1.15.12 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 the information element it 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 for after the starting time, the Multislot Allocation IE does not have to be included more than once.

9.1.15.13 MultiRateconfiguration

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 used in the serving cell.

In the case of a handover from a GERAN cell, if the Mode of the First Channel indicates a multi-rate speech codec, and this IE is not included, then the mobile station shall assume that the MultiRateconfiguration has not changed.

In the case of an intersystem handover to GERAN, if the Mode of the First Channel indicates a multi-rate speech codec, this IE shall be included. If not included in this case, the mobile station shall act as defined in sub-clause 3.4.4.1.

9.1.15.14 Dynamic ARFCN Mapping

This information element should only be included if the network supports dynamic ARFCN mapping and there is a need to define new dynamic ARFCN mapping, e.g. at handover to another PLMN or from another RAT to GSM. This information replaces any previously received information about dynamic ARFCN mapping. After returning to idle mode or packet idle mode, the mobile station shall acquire new dynamic ARFCN mapping information, except for the cases specified in sub-clause 3.2.2.1 (SI15). This mapping shall apply to any ARFCN used in the same message.

NOTE: If this information nelement is received with a value part length equal to zero or a value part that does not contain any dynamic ARFCN mapping, any previously received information about dynamic ARFCN mapping is deleted.

9.1.15.15 VGCS Target cell Ciphering information

Only mobile stations supporting "VGCS talking" have 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".

9.1.15.16 Dedicated Service Information

This information element shall only be included if the network supports dedicated mode MBMS notification and the mobile station supports MBMS.

9.1.15.17 Extended TSC Set, after time

9.1.15.18 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.