6.3 Mapping in time of logical channels onto physical channels

05.023GPPMultiplexing and Multiple Access on the Radio PathTS

6.3.1 Mapping in time of circuit switched logical channels onto physical channels

6.3.1.1 General

The mapping in time of circuit switched logical channels is defined in the tables of clause 7, which also defines the relationship of the air interface frames to the multiframe.

6.3.1.2 Key to the mapping table of clause 7

The following relates to the tables of clause 7. The columns headed:

i) "Channel designation" gives the precise acronym for the channel to which the mapping applies.

ii) "Sub‑channel number" identifies the particular sub‑channel being defined where a basic physical channel supports more than one channel of this type.

iii) "Direction" defines whether the mapping given applies identically to downlink and uplink (D&U), or to downlink (D) or uplink (U) only.

iv) "Allowable timeslots assignments" defines whether the channel can be supported on, or assigned to, any of the timeslots, or only on specific timeslots.

v) "Allowable RF channel assignments" defines whether the channel can use any or all of the radio frequency channels in the cell allocation (CA), or only the BCCH carrier (C0). It should be noted that any allocated channel Cx within CA could be any radio frequency channel, and that no ordering of radio frequency channel number is implied. For example, allocated channel C0 need not have the lowest radio frequency channel number of the allocation.

vi) "Burst type" defines which type of burst as defined in clause 5.2 is to be used for the physical channel.

vii) "Repeat length in TDMA frames" defines how many TDMA frames occur before the mapping for the interleaved blocks repeats itself e.g. 51.

viii) "Interleaved block TDMA frame mapping" defines, within the parentheses, the TDMA frames used by each interleaved block (e.g. 0..3). The numbers given equate to the TDMA frame number (FN) modulo the number of TDMA frames per repeat length; Therefore, the frame is utilized when:

TDMA frame mapping number = (FN)mod repeat length given.

Where there is more than one block shown, each block is given a separate designation e.g. B0, B1. Where diagonal interleaving is employed then all of the TDMA frames included in the block are given, and hence the same TDMA frame number can appear more than once (see GSM 05.03). Also, for E-TCH/F28.8, E-TCH/F32.0 and E-TCH/F43.2, the same frame number appears for the inband signalling message and for several interleaved blocks. It should be noted that the frame mapping for the SACCH/T channel differs according to the timeslot allocated in order to lower the peak processing requirements of the BSS.

6.3.1.3 Mapping of BCCH data

In order to facilitate the MS operation, it is necessary to transmit some System Information messages in defined multiframes and defined blocks within one multiframe, as follows (where TC = (FN DIV 51) mod (8)). Also for some System Information messages, the position where they are transmitted is contained in other System Information messages:

System Information Message

Sent when TC =

Allocation

Type 1

0

BCCH Norm

Type 2

1

BCCH Norm

Type 2 bis

5

BCCH Norm

Type 2 ter

5 or 4

BCCH Norm

Type 2 quater

5 or 4
or

5

BCCH Norm

BCCH Ext

Type 3

2 and 6

BCCH Norm

Type 4

3 and 7

BCCH Norm

Type 7

7

BCCH Ext

Type 8

3

BCCH Ext

Type 9

4

BCCH Norm

Type 13

4

or

0

BCCH norm

BCCH Ext

Type 16

6

BCCH Ext

Type 17

2

BCCH Ext

Type 18

Not fixed

Not fixed

Type 19

Not Fixed

Not Fixed

Type 20

Not fixed

Not fixed

This clause defines requirements on minimum scheduling: the network may send any System Information message when sending of a specific System Information message is not required. The following rules apply:

i) BCCH Ext may share the resource with PCH and AGCH (see clause 6.5.1).

ii) System Information Type 1 need only be sent if frequency hopping is in use or when the NCH is present in a cell. If the MS finds another message when TC = 0, it can assume that System Information Type 1 is not in use.

iii) System information type 2 bis or 2 ter messages are sent if needed, as determined by the system operator. If only one of them is needed, it is sent when TC = 5. If both are needed, 2bis is sent when TC = 5 and 2ter is sent at least once within any of 4 consecutive occurrences of TC = 4. A SI 2 message will be sent at least every time TC = 1. System information type 2 quater is sent if needed, as determined by the system operator. If sent on BCCH Norm, it shall follow the same rules as System information type 2 ter. If sent on BCCH Ext, it is sent at each occurrence of TC = 5.

iv) The definitions of BCCH Norm and BCCH Ext are given in clause 7 table 3 of 5.

v) Use of System Information type 7 and 8 is not always necessary. It is necessary if System Information type 4 does not contain all information needed for cell selection and reselection.

vi) System Information type 9 is sent in those blocks with TC = 4 which are specified in system information type 3 as defined in GSM 04.08.

vii) System Information type 13 is only related to the GPRS service. System Information Type 13 need only be sent if GPRS support is indicated in one or more of System Information Type 3 or 4 or 7 or 8 messages. These messages also indicate if the message is sent on the BCCH Norm or if the message is transmitted on the BCCH Ext. In the case that the message is sent on the BCCH Norm, it is sent at least once within any of 4 consecutive occurrences of TC=4.

viii) System Information type 16 and 17 are only related to the SoLSA service.

ix) System Information type 18 and 20 are sent in order to transmit non-GSM broadcast information. The frequency with which they are sent is determined by the system operator. System Information type 9 identifies the scheduling of System Information type 18 and 20 messages.

x) System Information Type 19 is sent if COMPACT neighbours exist. If System Information Type 19 is present, then its scheduling shall be indicated in System Information Type 9.

All the allowable timeslot assignments in a frame (see table 3 of 7 in clause 7) shall contain the same information.

6.3.1.4 Mapping of SID Frames

When the DTX mode of operation is active, it is required to transmit Silence Descriptor (SID) information, or equivalent dummy information, during the SACCH/T block period (104 TDMA frames). As the SID frames do not constitute a logical channel and their use is specific to DTX operation, the mapping of SID frames onto the TDMA frames is specified in GSM 05.08.

6.3.2 Mapping in time of packet logical channels onto physical channels

6.3.2.1 General

A physical channel allocated to carry packet logical channels is called a packet data channel (PDCH). A PDCH shall carry packet logical channels only.

Packet switched logical channels are mapped dynamically onto a 52-multiframe.

For the PDCH/F the 52-multiframe consists of 12 blocks of 4 consecutive frames, 2 idle frames and 2 frames used for the PTCCH (see GSM 05.10 and 03.64), as shown in Figure 9. Table 6 in clause 7, indicates the frame numbers for each of the blocks (B0…B11) transmitted in the multiframe. The ordered list of block is defined as B0, B6, B3, B9, B1, B7, B4, B10, B2, B8, B5, B11.

For PDCH/H, the 52-multiframe consists of 6 blocks of 4 frames each, and two idle frames. Table 6 in clause 7 indicates the frame numbers for each of the blocks (B0…B5) transmitted in the multiframe.

A block allocated to a given logical channel comprises one radio block, or in the case of uplink only, 4 random access bursts. The type of channel may vary on a block-by-block basis.

In the downlink direction, the logical channel type shall be indicated by the message type contained in the block header part.

In the uplink part for channels other than PACCH transmitted as access bursts or PRACH or CPRACH, the logical channel type shall be indicated by the message type contained in the block header part. For PACCH transmitted as access bursts, the logical channel type is indicated by the corresponding polling message on the downlink (see 04.60). For the PRACH or CPRACH case the logical channel type is indicated by the USF (See GSM 04.60), set on the downlink on a block by block basis.

For COMPACT, timeslot mapping and rotation of the control channels is used such that control channels belonging to a serving time group are rotated over odd timeslot numbers as follows: 7, 5, 3, 1, 7, 5  . The rotation occurs between frame numbers (FN) mod 52 = 3 and 4. The mapping of the control channels on timeslot numbers is defined by the following formula:

– for 0  FN mod 52  3, TN = ((6 x ((FN div 52) mod 4)) + 1 + (2 x TG)) mod 8;

– for 4  FN mod 52  51, TN = ((6 x ((FN div 52) mod 4)) + 7 + (2 x TG)) mod 8.

Packet switched logical channels PDTCH, PACCH, and PTCCH are never rotated.

6.3.2.2 Mapping of the uplink channels

6.3.2.2.1 Mapping of uplink packet traffic channel (PDTCH/U) and PACCH/U

The PDCH’s where the MS may expect occurrence of its PDTCH/U(s) or PACCH/U for a mobile originated transfer is indicated in resource allocation messages (see GSM 04.60). PACCH/U shall be allocated respecting the resources allocated to the MS and the MS multislot class. For each PDCH allocated to the MS, an Uplink State Flag (R0… R7) is given to the MS.

The occurrence of the PDTCH/U and/or the PACCH/U at given block(s) Bx (where Bx = B0…Bn; n=5 for the PDTCH/HU and n=11 for the PDTCH/FU) in the 52-multiframe structure for a given MS on a given PDCH shall be indicated by the value of the Uplink State Flag (USF) contained in the header of the preceding block transmitted in the downlink of the same PDCH, that is to say B(x-1) in the same multiframe if x1 or B(n) in the previous multiframe if x=0. If the USF in block B(x‑1) indicates that block B(x) shall be used by an MS for which the USF_GRANULARITY is set to 1 (corresponding to 4 blocks) in the last assignment message, that MS shall also use the three following blocks. The USF corresponding to the last three blocks shall be set to an unused value. The MS may transmit a PDTCH block or a PACCH block on any of the uplink blocks used by the MS. The occurrence of the PACCH/U associated to a PDTCH/D shall be indicated by the network by polling the MS (see GSM 04.60).

NOTE 1: This clause specifies how the network shall signal that the MS is allowed to use the uplink. The operation of the MS is specified in GSM 04.60. In particular cases of fixed allocation, extended dynamic allocation or exclusive allocation, the MS may not need to monitor the USF on all allocated PDCHs.

NOTE 2: The PDCH/HU is only assigned in exclusive allocation (see GSM 04.60).

For COMPACT, USF_GRANULARITY should be set to 0 (corresponding to 1 block) for dynamic allocation for the following cases:

i) for odd timeslot numbers (TN) 1, 3, 5, and 7 in nominal and large cells;

ii) for even timeslot numbers (TN) 0, 2, 4, and 6 in large cells.

6.3.2.2.2 Mapping of the Packet Timing Advance Control Channel (PTCCH/U)

The PDCH carrying the PTCCH/U of one MS is defined in the resource allocation message (see GSM 04.60). PTCCH/U shall be mapped to one of the time slots where PDTCH(s) are allocated to the MS. PTCCH/U shall be allocated respecting the resources allocated to the MS and the MS multislot class. An MS shall be allocated a sub-channel of the PTCCH/U (0…15) as defined in clause 7 table 6, where the sub-channel number is equal to the Timing Advance Index (TAI) indicated in the resource allocation message (see GSM 04.60).

6.3.2.2.3 Mapping of the uplink PCCCH i.e. PRACH

The mapping of the PRACH is defined in clause 7 table 6, where the possible blocks are indicated. The PRACH is dynamically allocated in groups of four PRACH blocks By (y=4x+i, i=0 ,.., 3) corresponding to one PDCH block Bx (x=0,…,11), indicated by USF=FREE in the same way as defined for PDTCH/U (see clause 6.3.2.2.1).

Optionally, a subset of the blocks Bx can be allocated to PRACH in a fixed way. The number of allocated blocks is indicated by the parameter BS_PRACH_BLKS broadcast on the PBCCH, where BS_PRACH_BLKS=0…12. The blocks are allocated according to the ordered list defined in clause 6.3.2.1. The blocks shall also be indicated by the USF=FREE. The MS may choose to use the BS_PRACH_BLKS or USF to determine the fixed allocated part of PRACH.

6.3.2.2.3a Mapping of the COMPACT uplink CPCCCH i.e. CPRACH

The CPRACH is dynamically or fixed allocated in the same way as defined for PRACH (see clause 6.3.2.2.3. USF should be set equal to FREE for downlink block B0 on a serving time group when 4 time groups are assigned. Uplink blocks (other than block B1 on a serving time group) that are preceded by CPBCCH and CPCCCH blocks should be prioritized for use as CPRACH.

See Annex D for examples based on sixteen prioritized CPRACH blocks.

6.3.2.3 Mapping of the downlink channels

6.3.2.3.1 Mapping of the (PDTCH/D) and PACCH/D

The PDCH where the MS may expect occurrence of its PDTCH/D(s) for a mobile terminated transfer or its PACCH/D, for both mobile originated and mobile terminated transfer are indicated in resource allocation messages (see GSM 04.60). The logical channel type shall be indicated in the block header. The mobile owner of the PDTCH/D or PACCH/D shall the indicated by the TFI (Temporary Frame Identifier) (see GSM 04.60).

6.3.2.3.2 Mapping of the PTCCH/D

The PTCCH/D is mapped as defined in Clause 7 table 6. The PTCCH/D carries signalling messages including timing advance information for MSs sharing the PTCCH/U on the same PDCH.

6.3.2.3.3 Mapping of the PBCCH

The PBCCH is mapped onto one PDCH only, indicated in the BCCH. The PBCCH is mapped on BS_PBCCH_BLKS blocks (where 1BS_PBCCH_BLKS4) per multiframe, according to the ordered list described in clause 6.3.2.1. The blocks allocated are specified in Clause 7 table 6. The parameter BS_PBCCH_BLKS is broadcast on PBCCH in block B0 (see clause 3.3.2.4).

6.3.2.3.3a Mapping of the COMPACT CPBCCH

The CPBCCH is mapped onto a primary COMPACT carrier on the time group indicated by TG on CSCH (see clause 3.3.2.2). This time group is known as the serving time group and rotates over odd timeslot numbers (see clause 6.3.2.1). The CPBCCH is mapped on BS_PBCCH_BLKS blocks (where 1BS_PBCCH_BLKS4) per multiframe, according to the ordered list described in clause 6.3.2.1. The blocks allocated are specified in clause 7 table 9. The parameters BS_PBCCH_BLKS is broadcast on CPBCCH in block B0 (see clause 3.3.2.4).

See Annex D for examples based on one CPBCCH block.

When USF=FREE in downlink block B0 on a serving time group, the CPRACH is allocated in uplink block B1 after timeslot rotation. When USF has any other value in downlink block B0 on a serving time group, the uplink allocation of B1 is valid for the same timeslot, irrespective of timeslot rotation.

6.3.2.3.4 Mapping of the PCCCH

The PCCCH and its different logical channels (PAGCH, PPCH, PNCH) and the PDTCH and PACCH can be mapped dynamically and are identified by the message header. The configuration is partly fixed by some parameters broadcast by the PBCCH and defined in clause 3.3.2.4:

a) BS_PBCCH_BLKS, that defines the number of PBCCH blocks per multiframe, according to the ordered list described in clause 6.3.2.1, on the PDCH that carries PBCCH;

b) BS_PAG_BLKS_RES, that defines the number of blocks in addition to BS_PBCCH_BLKS, according to the ordered list described in clause 6.3.2.1, where paging shall not occur on every PDCH that carries PCCCH.

If PBCCH is allocated on timeslot k, PCCCHs shall be allocated only on timeslots n where n>k-4 and 0£n£7 in order to provide time for the MS to switch from PBCCH to PCCCH.

6.3.2.3.4a Mapping of the COMPACT CPCCCH

The CPCCCH and its different logical channels (CPAGCH, CPPCH, CPNCH) and the PDTCH and PACCH can be mapped dynamically and are identified by the message header. The configuration is partly fixed by some parameters broadcast by the CPBCCH and defined in clause 3.3.2.4:

a) BS_PBCCH_BLKS, that defines the number of CPBCCH blocks per multiframe, according to the ordered list described in clause 6.3.2.1, on the radio frequency channel that carries CPBCCH;

b) BS_PAG_BLKS_RES, that defines the number of blocks in addition to BS_PBCCH_BLKS, where paging shall not occur on every radio frequency channel that carries CPCCCH. These blocks without paging are allocated after CPPCH blocks according to the ordered list described in clause 6.3.2.1.

For primary COMPACT carriers, CPCCCHs shall be allocated on the same time group as CPBCCH. CPCCCHs on secondary COMPACT carrier(s) shall be allocated on same time group as for primary COMPACT carrier.

See Annex D for examples based on three CPCCCH blocks.

6.3.2.4 Mapping of PBCCH data

In order to facilitate the MS operation, the network is required to transmit certain types of Packet System Information (PSI) messages in specific multiframes and specific PBCCH blocks within the multiframes. The occurrence of the PSI1 message is defined by TC = (FN DIV 52) mod PSI1_REPEAT_PERIOD, where PSI1_REPEAT_PERIOD (range 1 – 16) is indicated in the SI13 message on BCCH, the PSI 1 message on PBCCH and, if present, in the Neighbour Cell parameters in PSI3 and PSI3bis messages sent on serving cell PBCCH.

The PSI1 message is transmitted at TC = 0 according to rule i) and ii) below.

The PSI messages other than the PSI1 message are divided into two groups of PSI messages. One group of PSI messages is transmitted with a low repetition rate and a second group is transmitted with a high repetition rate.

The number of PSI message instances sent with high repetition rate is indicated by the parameter PSI_COUNT_HR (range 0 to 16) in the PSI1 message. The PSI messages in this group are sent according to rule iii) below.

The number of PSI message instances sent with low repetition rate is indicated by the parameter PSI_COUNT_LR (range 0 to 63) in the PSI1 message. The PSI messages in this group are sent according to rule iv) below.

The following rules apply:

i) PSI1 shall be sent in block B0 when TC = 0;

ii) if the value of the parameter BS_PBCCH_BLKS is greater than 1, the PSI1 shall also be sent in block B6 when TC = 0;

iii) the PSI messages in the group sent with high repetition rate shall be sent in a sequence determined by the network and starting at TC = 0, using the PBCCH blocks within each multiframe, in the order of occurrence, which are not occupied according to rule i) or ii). The sequence of these PSI messages shall be repeated starting at each occurrence of TC = 0;

iv) the PSI messages in the group sent with low repetition rate shall be sent in a sequence determined by the network and continuously repeated, using the PBCCH blocks within each multiframe, in the order of occurrence, which are not occupied according to rules i) to iii) . The sequence of these PSI messages shall be restarting at FN = 0.

If there are multiple instances of a particular type of PSI message (See GSM 04.60), they shall all be sent within same group of PSI messages according to either rule iii) or iv) above. They shall be sent in a single sequence in the ascending order of the message instance number of that type of PSI message.

The same PSI message shall not occur twice within the lists defined by PSI_COUNT_LR and PSI_COUNT_HR

A full set of Packet System Information messages contains one consistent set of the messages included in PSI_COUNT_LR and one consistent set of the messages included in PSI_COUNT_HR plus the PSI1 message.

NOTE: The parameters BS_PBCCH_BLKS and PSI1_REPEAT_PERIOD_shall be selected by the network such that all PSI message present in the cell can be sent according to rules i) to iv) above. It is the responsibility of the network to optimise the broadcast of the PSI messages so that the MS can find the important parameters for cell re-selection and access as fast as possible without unnecessary power consumption. The PSI mapping scheme information can be utilised by the MS to estimate the actual minimum cell reselection time.

6.3.2.4a Mapping of COMPACT CPBCCH data

See clause 6.3.2.4, with the exception that the CPBCCH is a stand-alone packet control channel for COMPACT.

6.3.3 Mapping in time of CTS control channels onto physical channels

The mapping in time of CTS control channels is defined in the table 8 of clause 7, which also defines the relationship of the air interface TDMA frames to the multiframe.

The timeslot assignment of the CTS control channel is defined hereafter.

6.3.3.1 CTSBCH timeslot assignment

For the CTSBCH, a procedure of timeslot shifting from one 52-multiframe to another is defined. The usage of this procedure is mandatory in CTS idle mode and optional in CTS dedicated mode. When the shifting procedure is not applied, the CTSBCH timeslot number shall be equal to the TNC broadcast in the current 52-multiframe CTSBCH-SB.

The following parameters are required for the timeslot shifting procedure.

Parameters broadcast in the CTSBCH-SB:

a) TNI: initial timeslot number (0 to 7, 3 bits), defined by the three LSBs (BN3, BN2, BN1) of the FPBI (specified in GSM 03.03);

b) TNSCN: timeslot number series couple number (0 to 31, 5 bits), defined by the 5 bits (BN8, …, BN4) of the FPBI. Defines the couple of timeslot number circular series (TNSTNSCN,0, TNSTNSCN,1) to be used to form the timeslot shifting sequence. See timeslot number series (TNS) definition in table below.

Table 1 (clause 6.3.3): TNSi,j definition

TNSCN

TNSTNSCN,0

TNSTNSCN,1

TNSCN

TNSTNSCN,0

TNSTNSCN,1

0

( 0, 1, 2, 4, 7, 5, 6, 3 ),

( 0, 3, 5, 7, 6, 2, 1, 4 )

16

( 0, 1, 5, 6, 7, 4, 3, 2 ),

( 0, 4, 7, 6, 2, 5, 1, 3 )

1

( 0, 1, 2, 5, 3, 6, 7, 4 ),

( 0, 4, 1, 5, 7, 6, 3, 2 )

17

( 0, 2, 1, 3, 6, 7, 5, 4 ),

( 0, 3, 7, 4, 1, 5, 6, 2 )

2

( 0, 1, 2, 6, 5, 3, 7, 4 ),

( 0, 3, 6, 7, 5, 2, 4, 1 )

18

( 0, 2, 1, 5, 6, 7, 4, 3 ),

( 0, 4, 7, 5, 1, 3, 6, 2 )

3

( 0, 1, 2, 6, 7, 5, 4, 3 ),

( 0, 3, 7, 4, 6, 2, 5, 1 )

19

( 0, 2, 3, 4, 7, 6, 5, 1 ),

( 0, 3, 1, 5, 2, 6, 7, 4 )

4

( 0, 1, 3, 2, 5, 6, 7, 4 ),

( 0, 4, 7, 6, 2, 1, 5, 3 )

20

( 0, 2, 3, 6, 7, 5, 1, 4 ),

( 0, 4, 7, 6, 3, 5, 2, 1 )

5

( 0, 1, 3, 6, 7, 5, 2, 4 ),

( 0, 3, 7, 4, 2, 6, 5, 1 )

21

( 0, 2, 3, 7, 5, 6, 4, 1 ),

( 0, 3, 6, 2, 1, 5, 7, 4 )

6

( 0, 1, 4, 2, 5, 6, 7, 3 ),

( 0, 2, 6, 3, 7, 5, 4, 1 )

22

( 0, 2, 4, 7, 3, 6, 5, 1 ),

( 0, 3, 5, 6, 7, 4, 1, 2 )

7

( 0, 1, 4, 2, 5, 7, 6, 3 ),

( 0, 4, 7, 3, 5, 6, 2, 1 )

23

( 0, 2, 5, 3, 6, 7, 4, 1 ),

( 0, 3, 7, 6, 5, 1, 2, 4 )

8

( 0, 1, 4, 2, 6, 5, 7, 3 ),

( 0, 2, 1, 5, 3, 6, 7, 4 )

24

( 0, 2, 5, 3, 7, 6, 4, 1 ),

( 0, 3, 5, 1, 2, 6, 7, 4 )

9

( 0, 1, 4, 5, 7, 3, 6, 2 ),

( 0, 3, 7, 6, 5, 2, 4, 1 )

25

( 0, 2, 6, 3, 1, 5, 7, 4 ),

( 0, 3, 4, 7, 6, 5, 1, 2 )

10

( 0, 1, 4, 6, 5, 7, 3, 2 ),

( 0, 4, 7, 5, 1, 2, 6, 3 )

26

( 0, 2, 6, 5, 1, 4, 7, 3 ),

( 0, 4, 5, 7, 6, 3, 1, 2 )

11

( 0, 1, 4, 7, 3, 5, 6, 2 ),

( 0, 4, 2, 1, 5, 7, 6, 3 )

27

( 0, 2, 6, 5, 3, 7, 4, 1 ),

( 0, 3, 6, 7, 5, 1, 2, 4 )

12

( 0, 1, 4, 7, 6, 3, 5, 2 ),

( 0, 4, 2, 1, 5, 6, 7, 3 )

28

( 0, 3, 5, 1, 2, 6, 7, 4 ),

( 0, 4, 7, 6, 5, 2, 3, 1 )

13

( 0, 1, 5, 2, 4, 7, 6, 3 ),

( 0, 3, 7, 5, 1, 4, 6, 2 )

29

( 0, 3, 5, 2, 6, 7, 4, 1 ),

( 0, 4, 7, 3, 6, 5, 1, 2 )

14

( 0, 1, 5, 2, 6, 4, 7, 3 ),

( 0, 3, 4, 5, 7, 6, 2, 1 )

30

( 0, 3, 6, 7, 4, 2, 5, 1 ),

( 0, 4, 1, 2, 6, 5, 7, 3 )

15

( 0, 1, 5, 6, 2, 4, 7, 3 ),

( 0, 3, 7, 6, 4, 5, 2, 1 )

31

( 0, 3, 7, 5, 6, 2, 4, 1 ),

( 0, 4, 7, 6, 3, 5, 1, 2 )

Parameters sent on a dedicated connection during the CTS-MS attachment:

a) TNSCO: TNS couple order (1 bit), defines together with TNSCN the ordered couple (TNS1, TNS2).

if TNSCO = 0 then (TNS1, TNS2) = (TNSTNSCN,0, TNSTNSCN,1)

if TNSCO = 1 then (TNS1, TNS2) = (TNSTNSCN,1, TNSTNSCN,0)

b) parameters to be used to form the timeslot shifting sequence.

x0 : 0 to 7, 3 bits

x1 : 0 to 7, 3 bits

x2 : 0 to 7, 3 bits

x3 : 0 to 7, 3 bits

For a given set of parameters, a unique timeslot shifting sequence of length of 8 x 51 52-multiframes is defined. The shifting sequence is repeated 128 times over the duration of a GSM hyperframe. It is divided into 8 sets of 51 52-multiframes. The structure of a set is explicitly shown on figure below:

Figure 1 (clause 6.3.3): Structure of timeslot shifting sequence

A set is formed by interleaving segments of TNS1 and TNS2. The mapping of TNS1 and TNS2 segments onto a set is defined by the parameters x0, x1, x2, x3 as follows :

for (FN div 52) mod 51 = 0 to 7 a TNS1 segment is used

for (FN div 52) mod 51 = 8 to 7+x3 a TNS2 segment is used

for (FN div 52) mod 51 = 8+x3 to 7+x3+x2 a TNS1 segment is used

for (FN div 52) mod 51 = 8+x3+x2 to 7+x3+x2+x1 a TNS2 segment is used

for (FN div 52) mod 51 = 8+x3+x2+x1 to 7+x3+x2+x1+x0 a TNS1 segment is used

for (FN div 52) mod 51 = 8+x3+x2+x1+x0 to 15+x3+x2+x1+x0 a TNS2 segment is used

for (FN div 52) mod 51 = 16+x3+x2+x1+x0 to 23+x3+x2+x1 a TNS1 segment is used

for (FN div 52) mod 51 = 24+x3+x2+x1 to 31+x3+x2 a TNS2 segment is used

for (FN div 52) mod 51 = 32+x3+x2 to 39+x3 a TNS1 segment is used

for (FN div 52) mod 51 = 40+x3 to 47 a TNS2 segment is used

for (FN div 52) mod 51 = 48 to 50 a TNS1 segment is used

The TNS1 and TNS2 segments are extracted from TNS1 and TNS2 according to the following rules :

a) The first CTSBCH TN used in a shifting sequence shall be the TNI.

b) Two consecutive CTSBCH TN shall be separated by single circular shifts along TNS1 and TNS2.

c) When changing from a TNSi segment to a TNSj segment, the last timeslot obtained from TNSi shall be followed by its immediate successor in TNSj.

NOTE: The first timeslot of a set is obtained by three circular shifts in TNS1 with regard to the first timeslot of the previous set.

An example of the mapping of TNS1 and TNS2 onto the first set of the generated shifting sequence is given in annex C.

6.3.3.2 CTSPCH, CTSARCH and CTSAGCH timeslot assignment

For the CTSPCH, CTSARCH and CTSAGCH, the timeslot shall be assigned by the CTS-FP for each 52-multiframe. The timeslot number used for CTSPCH, CTSARCH and CTSAGCH shall be the TNC broadcast in the previous 52‑multiframe CTSBCH-SB.