B.1 RLC data block delimitation for GPRS

04.603GPPGeneral Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocolRelease 1999TS

B.1.1 Example 1

Figure B.1 provides an example of the use of the Length indicator in conjunction with the M and E bits. In the example, LLC PDU 1 continues from a previous RLC data block and ends in the RLC data block shown. LLC PDU 2 follows LLC PDU 1 and is completely contained within the RLC data block. LLC PDU 3 follows LLC PDU 2, beginning in the RLC data block shown, and continues into the next RLC data block.

Bit

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

PR

TFI

FBI

Octet 1

BSN

E = 0

Octet 2

Length indicator = 11

M = 1

E = 0

Octet 3

LLC PDU 1

Length indicator = 26

M = 1

E = 1

Octet 4

Octet 5

LLC PDU 1 (cont)

.

.

.

Octet 15

Octet 16

Octet 17

LLC PDU 2

.

.

.

LLC PDU 2

Octet 41

Octet 42

Octet 43

LLC PDU 3

.

.

.

LLC PDU 3

Octet N-1

Octet N

Figure B.1: Length indicator (LI) example

B.1.2 Example 2

Figure B.2 provides an example of the use of the Length indicator when the end of an LLC PDU would fit within an RLC data block but the addition of the length indicator octet (to indicate the LLC PDU boundary) causes the LLC PDU to extend into another RLC data block. In the example, LLC PDU 1 continues from a previous RLC data block and has 20 remaining octets. The first 19 octets are placed into RLC data block N, the Length Indicator is set to 0 (to indicate that the LLC PDU does not end within the current RLC data block), and the 20th octet is placed in RLC data block N+1.

RLC data block N

bit

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

PR

TFI

FBI

Octet 1

BSN

E = 0

Octet 2

Length indicator = 0

M = 0

E = 1

Octet 3

Octet 4

LLC PDU 1 (cont)

.

.

.

LLC PDU 1

Octet 22

RLC data block N + 1

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

TFI

FBI

Octet 1

BSN

E = 0

Octet 2

Length indicator = 1

M = 1

E = 1

Octet 3 (optional)

LLC PDU 1 (cont)

Octet 4

LLC PDU 2

.

.

.

LLC PDU 2

Octet 22

Figure B.2: Length indicator (LI) example

B.1.3 Example 3

Figure B.3 provides an example of the use of the Length indicator when the end of an LLC PDU fits precisely into an RLC data block. In the example, LLC PDU 1 continues from a previous RLC data block and ends in the RLC data block shown. LLC PDU 2 follows LLC PDU 1 and fills precisely the RLC data block shown.

Bit

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

PR

TFI

FBI

Octet 1

BSN

E = 0

Octet 2

LLC PDU 1

Length indicator = 7

M = 1

E = 0

Octet 3

Length indicator = 11

M = 0

E = 1

Octet 4

Octet 5

LLC PDU 1 (cont)

.

.

.

Octet 11

Octet 12

LLC PDU 2

.

.

.

LLC PDU 2

Octet 22

Figure B.3: Length indicator (LI) example

B.1.4 Example 4

Figure B.4 provides an example when the Length indicator is not used. As the example does not contain any LLC frame boundaries, no Length Indicator octets are needed. 20 octets is used for LLC data in each RLC data block.

RLC data block N

bit

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

PR

TFI

FBI

Octet 1

BSN

E = 1

Octet 2

Octet 3

.

LLC PDU 1 (cont)

.

.

.

LLC PDU 1

Octet 22

RLC data block N + 1

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

TFI

FBI

Octet 1

BSN

E = 1

Octet 2

Octet 3

LLC PDU 1

LLC PDU 1 (cont)

.

.

.

Octet 22

Figure B.4: Example when Length indicator (LI) can be omitted

B.1.5 Example 5

Figure B.5 provides an example when the final LLC PDU (FBI=1) of a downlink TBF fills the RLC data block precisely in which case the Length indicator can be omitted. In the example, LLC PDU 1 continues from a previous RLC data block and ends in and fills precisely the RLC data block shown.

Bit

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

PR

TFI

FBI=1

Octet 1

BSN

E = 1

Octet 2

LLC PDU 1

Octet 3

Octet 4

LLC PDU 1 (cont)

.

.

.

.

.

.

Octet 22

Figure B.5: Example when Length indicator (LI) can be omitted

B.1.6 Example 6

Figure B.6 provides an example when the final LLC PDU (CV=0) of an uplink TBF fills the RLC data block precisely in which case the Length indicator can be omitted. In the example, LLC PDU 1 continues from a previous RLC data block and ends in and fills precisely the RLC data block shown.

Bit

8

7

6

5

4

3

2

1

Payload Type

Countdown value = 0

SI

R

MAC header

spare

TFI

TI

Octet 1

BSN

E = 1

Octet 2

LLC PDU 1

Octet 3

Octet 4

LLC PDU 1 (cont)

.

.

.

.

.

.

Octet 22

Figure B.6: Example when Length indicator (LI) can be omitted

B.1.7 Example 7

Figure B.7 provides an example when the Length indicator can be omitted. As the LLC PDU 1 begins in the RLC data block N and continues to the next one, no Length octet is needed.

RLC data block N

Bit

8

7

6

5

4

3

2

1

Payload Type

Countdown value

SI

R

MAC header

spare

TFI

TI

Octet 1

BSN

E = 1

Octet 2

Octet 3

Octet 4

LLC PDU 1

.

.

.

LLC PDU 1

.

.

.

Octet 22

RLC data block N+1

Bit

8

7

6

5

4

3

2

1

Payload Type

Countdown value

SI

R

MAC header

spare

TFI

TI

Octet 1

BSN

E = 0

Octet 2

LI=10

M=1

E=1

Octet 3

Octet 4

LLC PDU 1 (cont)

.

Octet 13

LLC PDU 2

.

.

.

LLC PDU 2

Octet 22

Figure B.7: Example when Length indicator (LI) can be omitted