16 Support of transparent bearer services

08.203GPPRate Adaptation on the Base Station System - Mobile Service Switching Centre (BSS-MSC) InterfaceTS

16.1 TCH/F9.6 and TCH/F4.8 channel codings

16.1.1 User rate adaptation on the A interface, AIUR less than or equal to 38,4 kbit/s

The ITU-T V.110 80 bit frame shall be used for transparent data on the A interface. These frames are transmitted on up to four substreams multiplexed into one stream sent over the A interface. The split/combine function is applied on the substreams as specified in clause 5 of this GSM TS. The relation between the AIUR and the number of channels is specified in table11.

The 64 kbit/s consists of octets, bits 1 through 8, with bit 1 transmitted first.

For a 9 600 bit/s radio interface user rate the V.110 frame is carried with a 16 kbits/s stream which occupies bit positions (1,2).

For radio interface user rates of either 4 800 bit/s, 2 400 bit/s, 1 200 bit/s or 300 bit/s the V.110 frame is carried with a 8 kbits/s stream which occupies bit position (1). For user rates < 1 200bit/s asynchronous characters are padded with additional stop elements by the RA0 function (in the MSC/IWF) to fit into 600 bit/s synchronous RA1 rate prior to rate adaptation to 64 kbits/s.

No use of 4 kbit/s stream is foreseen.

In a given V.110 frame on the A interface:

– for 9 600 bit/s there is no repetition of bits D within the 16 kbit/s stream ;

– for 4 800 bit/s there is no repetition of bits D within the 8 kbit/s stream ;

– for 2 400 bit/s each bit D is repeated twice within the 8 kbit/s stream (D1 D1 D2 D2 etc) ;

– for 1 200 bit/s each bit D is repeated four times within the 8 kbit/s stream (D1 D1 D1 D1 D2 D2 D2 D2 etc) ;

– for 600 bit/s each bit D is repeated eight times within the 8kbit/s stream (D1 D1 D1 D1 D1 D1 D1 D1 D2 D2 D2 D2 D2 D2 D2 D2 etc);

16.1.2 User rate Adaptation on the A-interface, AIUR greater than 38,4 kbit/s

For AIUR of 48 kbit/s, 56 kbit/s and 64 kbit/s one stream consisting of ITU-T V.110 32 bit frames or 64 bit frames, as specified in 3GPP TS 04.21 shall be transmitted over the A-interface. Splitting/Combining which occurs in the BSS, is as specified in 3GPP TS 04.21.

Table 11 gives the relation between the User Rate, Substream Rate Channel Coding and the Intermediate Rate.

16.1.3 Relation between AIUR and the number of channels

Table11: Relationship between the AIUR, substream rate, channel coding, intermediate rate and number of channels

AIUR

Number of channels x Substream Rate

Channel Coding

(Multislot) intermediate Rate (Note1)

2,4 kbit/s

2-8 times duplication of each bit to reach 4,8 kbit/s

TCH/F4.8

8 kbit/s

4,8 kbit/s

4,8 kbit/s

TCH/F4.8

8 kbit/s

9,6 kbit/s

2X4,8 kbit/s

2XTCH/F4.8

8 kbit/s

9,6 kbit/s

9,6 kbit/s

TCH/F9.6

16 kbit/s

14,4 kbit/s

3X4,8 kbit/s

3XTCH/F4.8

8 kbit/s

14,4 kbit/s

2X9,6 kbit/s w/ padding

2XTCH/F9.6

16 kbit/s

19,2 kbit/s

4X4,8 kbit/s

4XTCH/F4.8

8 kbit/s

19,2 kbit/s

2X9,6 kbit/s

2XTCH/F9.6

16 kbit/s

28,8 kbit/s

3×9,6 kbit/s

3XTCH/F9.6

16 kbit/s

38,4 kbit/s

4X9,6 kbit/s

4XTCH/F9.6

16 kbit/s

48 kbit/s

5X9,6 kbit/s

5XTCH/F9.6

64 kbit/s

56 kbit/s

5X11,2 kbit/s

5XTCH/F9.6

64 kbit/s

64 kbit/s

66×11,2 kbit/s w/padd.

6XTCH/F9.6

64 kbit/s

NOTE: For AIURs  38,4 kbit/s this column indicates the multislot intermediate rate: for higher AIURs it indicates the intermediate rate.

16.1.4 Handling of status bits X, SA, SB

In the single slot case, status bit SA shall be coded repeatedly as S1, S3, S6, S8, and SB is coded repeatedly as S4 and S9 in Figure 2. In the multislot case, status bit SA is coded repeatedly as S6, S8 and SB is coded as S9 in figures 2, 5 and 6.

The handling of the status bits shall comply with the synchronisation procedures for transparent services which are as described in 3GPP TS 29.007 (MSC), 3GPP TS 04.21 (BSS), 3GPP TS 27.001 (MS).

16.1.5 Handling of bits E1 to E7

Bits E1 to E3 shall be used according to 04.21.

Bits E4 to E7 may be used for network independent clocking as indicated in 3GPP TS 04.21.

16.2 TCH/F14.4, TCH/F28.8, and TCH/F32.0 channel codings

16.2.1 User rate adaptation on the A interface, AIUR less than or equal to 56 kbit/s

The A-TRAU frame shall be used for transparent user data rates other than 32 kbit/s on the A interface. The A-TRAU frames are transmitted on up to four substreams multiplexed into one stream sent over the A interface. The split/combine function is applied on the substreams as specified in clause 7 of this TS. The relation between the AIUR and the number of channels is specified in table 12.

In a given A-TRAU frame on the A interface:

– for 14 400 bit/s there is no repetition of bits D within the 16 kbit/s stream in a given A-TRAU frame on the A interface.

The ITU-T I.460 rate adaptation is used for the transparent 32 kbit/s user rate on the A interface, i.e. four bits of each octet in the 64 kbit/s time slot are used for transporting the 32 kbit/s user data.

16.2.2 User Rate Adaptation on the A-interface, AIUR greater than 56 kbit/s

For AIUR of 64 kbit/s one stream consisting of ITU-T V.110 32 bit frames or 64 bit frames, as specified in 3GPP TS 04.21 shall be transmitted over the A-interface. Splitting/Combining which occurs in the BSS, shall be as specified in 3GPP TS 04.21.

Table 12 gives the relation between the User Rate, Substream Rate Channel Coding and the Intermediate Rate.

16.2.3 Relation between AIUR and the number of channels

Table 12: Relationship between the AIUR, AIUR per substream, channel coding, intermediate rate and number of substreams

AIUR

Number of substreams x
AIUR per substream

Channel Coding

Multislot intermediate Rate (note 1)

14,4 kbit/s

14,4 kbit/s

TCH/F14.4

16 kbit/s

28,8 kbit/s

2X14,4 kbit/s

TCH/F14.4

TCH/F28.8

16 kbit/s

32 kbit/s

1×32 kbit/s

TCH/F32.0

32 kbit/s

38,4 kbit/s

3X14,4 kbit/s w/padding

TCH/F14.4

16 kbit/s

48 kbit/s

4X14,4 kbit/s w/padding

TCH/F14.4

16 kbit/s

56 kbit/s

4X14,4 kbit/s w/padding

1×64.0 kbit/s (Note 2)

TCH/F14.4

TCH/F32.0

16 kbit/s

64 kbit/s

64kbit/s

5X14,4 kbit/s w/padding

1×64.0 kbit/s (Note 2)

TCH/F14.4

TCH/F32.0

64 kbit/s

NOTE 1: For AIURs  56 kbit/s this column indicates the multislot intermediate rate: for higher AIURs it indicates the intermediate rate.

NOTE 2: One substream over two air interface timeslots. No multislot intermediate rate.

16.2.4 Handling of status bits X and SB

The X and SB bits shall be carried over the A interface in a multiframe structure as described in subclause 8.1.1.1 of 3GPP TS 04.21. SA bit is not carried over the A interface.

The handling of the status bits shall comply with the synchronisation procedures for transparent services which are as described in 3GPP TS 29.007 (MSC), 3GPP TS 04.21 (BSS), 3GPP TS 27.001 (MS).