Digital cellular telecommunications system (Phase 2+) (GSM); Radio Link Protocol (RLP) for data and telematic services on the Mobile Station - Base Station System (MS - BSS) interface and the Base Station System - Mobile-services Switching Centre (BSS - MSC) interface (GSM 04.22 version 5.2.1)

This European Telecommunication Standard (ETS) specifies the Radio Lin k Protocol (RLP) for data transmission over the GSM PLMN. RLP covers t he Layer 2 functionality of the ISO OSI Reference Model (IS 7498). It is based on ideas contained in IS 3309, IS 4335 and IS 7809 (HDLC of I SO) as well as CCITT X.25 and Q.92x (LAP-B and LAP-D of CCITT, respect ively.) RLP has been tailored to the special needs of digital radio tr ansmission. RLP provides to its users the OSI Data Link Service (IS 88 86). RLP is intended for use with non-transparent data-transfer. Protocol c onversion may be provided for a variety of protocol configurations. Th ose foreseen immediately are: -   Character-mode protocols using start-stop transmission (IA5);  -   X.25 LAP-B.  For reasons of better presentation, material about protocol conversion has been placed within those Specifications concerned with the releva nt Terminal Adaptors, i.e. GSM 07.02 for the asynchronous case and GSM 07.03 for the synchronous case. Care must be taken that that material also applies to Interworking Functions; see GSM 09.04 - 09.07.

Digitalni celični telekomunikacijski sistem (faza 2+) – Protokol za radijsko povezovanje (RLP) podatkov in telematskih storitev o vmesniku sistema mobilna postaja-bazna postaja (MS-BSS) in vmesniku komutacijskega centra sistema bazne postaje-mobilne storitve (BSS-MSC) (GSM 04.22, različica 5.2.1)

General Information

Status
Published
Publication Date
30-Nov-2003
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Dec-2003
Due Date
01-Dec-2003
Completion Date
01-Dec-2003

Buy Standard

Standard
SIST ETS 300 946 E3:2003
English language
63 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
SIST ETS 300 946 E3:2003
01-december-2003
'LJLWDOQLFHOLþQLWHOHNRPXQLNDFLMVNLVLVWHP ID]D ±3URWRNRO]DUDGLMVNR
SRYH]RYDQMH 5/3 SRGDWNRYLQWHOHPDWVNLKVWRULWHYRYPHVQLNXVLVWHPDPRELOQD
SRVWDMDED]QDSRVWDMD 06%66 LQYPHVQLNXNRPXWDFLMVNHJDFHQWUDVLVWHPD
ED]QHSRVWDMHPRELOQHVWRULWYH %6606&  *60UD]OLþLFD

Digital cellular telecommunications system (Phase 2+) (GSM); Radio Link Protocol (RLP)

for data and telematic services on the Mobile Station - Base Station System (MS - BSS)

interface and the Base Station System - Mobile-services Switching Centre (BSS - MSC)

interface (GSM 04.22 version 5.2.1)
Ta slovenski standard je istoveten z: ETS 300 946 Edition 3
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
SIST ETS 300 946 E3:2003 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ETS 300 946 E3:2003
---------------------- Page: 2 ----------------------
SIST ETS 300 946 E3:2003
EUROPEAN ETS 300 946
TELECOMMUNICATION January 1998
STANDARD Third Edition
Source: SMG Reference: RE/SMG-040422QR2
ICS: 33.020

Key words: Digital cellular telecommunications system, Global System for Mobile communications (GSM)

GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
Digital cellular telecommunications system (Phase 2+);
Radio Link Protocol (RLP) for data and telematic services on the
Mobile Station - Base Station System (MS - BSS) interface
and the Base Station System - Mobile-services Switching Centre
(BSS - MSC) interface
(GSM 04.22 version 5.2.1)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: secretariat@etsi.fr
Tel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16

Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the

foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1998. All rights reserved.
---------------------- Page: 3 ----------------------
SIST ETS 300 946 E3:2003
Page 2
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998

Whilst every care has been taken in the preparation and publication of this document, errors in content,

typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to

"ETSI Editing and Committee Support Dept." at the address shown on the title page.

---------------------- Page: 4 ----------------------
SIST ETS 300 946 E3:2003
Page 3
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
Contents

Foreword .......................................................................................................................................................5

1 Scope ..................................................................................................................................................7

2 Normative references..........................................................................................................................7

2.1 Definitions and abbreviations...............................................................................................8

3 Introduction..........................................................................................................................................9

4 Frame structure.................................................................................................................................10

4.1 Basic frame structure.........................................................................................................10

4.2 RLP header........................................................................................................................10

4.3 Order of transmission ........................................................................................................10

4.4 Frame check sequence .....................................................................................................10

5 Elements and procedure ...................................................................................................................11

5.1 Modes ................................................................................................................................11

5.1.1 Asynchronous Balanced Mode (ABM) ..........................................................11

5.1.2 Asynchronous Disconnected Mode (ADM) ...................................................11

5.2 Header and parameters.....................................................................................................11

5.2.1 Generally used bits........................................................................................12

5.2.1.1 Command/response bit, C/R ...............................................12

5.2.1.2 Poll/Final bit, P/F..................................................................12

5.2.2 Unnumbered frames, U.................................................................................13

5.2.2.1 Set asynchronous balanced mode SABM (11100)..............13
5.2.2.2 Unnumbered Acknowledge. UA (00110).............................13

5.2.2.3 Disconnect, DISC (00010)...................................................13

5.2.2.4 Disconnected Mode, DM (11000)........................................13
5.2.2.5 Unnumbered Information, UI (00000)..................................13

5.2.2.6 Exchange Identification, XID (11101) ..................................13

5.2.2.7 Test, TEST (00111).............................................................14

5.2.2.8 Null information, NULL (11110) ...........................................15

5.2.2.9 REMAP (10001)..................................................................15

5.2.3 Supervisory frames, S, and numbered information transfer and

supervisory frames combined, I+S................................................................15

5.2.3.1 Numbering ...........................................................................16

5.2.3.2 Send Sequence number, N(S) ............................................16

5.2.3.3 Receive sequence number, N(R) ........................................16

5.2.3.4 L2R Status bit ......................................................................16

5.2.3.5 Receive ready, RR (00) .......................................................16

5.2.3.6 Reject, REJ (01) ..................................................................16

5.2.3.7 Receive not ready, RNR (10)...............................................17

5.2.3.8 Selective reject, SREJ (11)..................................................17

5.3 Error Recovery...................................................................................................................17

5.3.1 Improper frames............................................................................................17

5.3.2 N(S) sequence error......................................................................................17

5.3.3 N(R) error ......................................................................................................18

5.3.4 Time-out and checkpointing ..........................................................................18

5.3.4.1 Treatment of errors during link establishment, link reset

and link disconnect ..............................................................18

5.3.4.2 Treatment of errors during numbered information transfer .18

5.3.5 Contentious situations ...................................................................................18

5.4 Transitions between TCH/F9.6 and TCH/F14.4 channel codings.................18

5.5 List of system parameters..................................................................................................19

5.5.1 RLP Version N° .............................................................................................20

5.5.2 Maximum number of outstanding I frames k (Window size).........................20

5.5.3 Timer T1........................................................................................................20

---------------------- Page: 5 ----------------------
SIST ETS 300 946 E3:2003
Page 4
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998

5.5.4 Maximum number of retransmissions N2..................................................... 20

5.5.5 Data Compression Parameters .................................................................... 20

5.5.6 Re-sequencing period (Timer T4)................................................................. 21

5.6 Support for discontinuous transmission (DTX) ................................................................. 21

6 Service definitions............................................................................................................................. 21

6.1 Introduction........................................................................................................................ 21

6.2 Conventions ...................................................................................................................... 21

6.3 Queue model..................................................................................................................... 22

6.4 List of Primitives ................................................................................................................ 23

6.5 Possible RLP time sequence diagrams ............................................................................ 24

Annex A (informative): RLP SDL Diagrams ........................................................................................... 27

A.1 List of RLP entity states .................................................................................................................... 27

A.1.1 (main) states ..................................................................................................................... 27

A.1.2 state variables ................................................................................................................... 27

A.2 List of RLP entity events ................................................................................................................... 31

History......................................................................................................................................................... 63

---------------------- Page: 6 ----------------------
SIST ETS 300 946 E3:2003
Page 5
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
Foreword

This European Telecommunication Standard (ETS) has been produced by the Special Mobile Group

(SMG) of the European Telecommunications Standards Institute (ETSI).

This ETS specifies the Radio Link Protocol (RLP) for data transmission over within the digital cellular

telecommunications system.

The specification from which this ETS has been derived was originally based on CEPT documentation,

hence the presentation of this ETS may not be entirely in accordance with the ETSI rules.

Transposition dates
Date of adoption of this ETS: 2 January 1998
Date of latest announcement of this ETS (doa): 30 April 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 October 1998
Date of withdrawal of any conflicting National Standard (dow): 31 October 1998
---------------------- Page: 7 ----------------------
SIST ETS 300 946 E3:2003
Page 6
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
Blank page
---------------------- Page: 8 ----------------------
SIST ETS 300 946 E3:2003
Page 7
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
1 Scope

This European Telecommunication Standard (ETS) specifies the Radio Link Protocol (RLP) for data

transmission over the GSM PLMN. RLP covers the Layer 2 functionality of the ISO OSI Reference Model

(IS 7498). It is based on ideas contained in IS 3309, IS 4335 and IS 7809 (HDLC of ISO) as well as CCITT

X.25 and Q.92x (LAP-B and LAP-D of CCITT, respectively.) RLP has been tailored to the special needs of

digital radio transmission. RLP provides to its users the OSI Data Link Service (IS 8886).

RLP is intended for use with non-transparent data-transfer. Protocol conversion may be provided for a

variety of protocol configurations. Those foreseen immediately are:
- Character-mode protocols using start-stop transmission (IA5);
- X.25 LAP-B.

For reasons of better presentation, material about protocol conversion has been placed within those

Specifications concerned with the relevant Terminal Adaptors, i.e. GSM 07.02 for the asynchronous case

and GSM 07.03 for the synchronous case. Care must be taken that that material also applies to

Interworking Functions; see GSM 09.04 - 09.07.
2 Normative references

This ETS incorporates by dated and undated reference, provisions from other publications. These

normative references are cited at the appropriate places in the text and the publications are listed

hereafter. For dated references, subsequent amendments to or revisions of any of these publications

apply to this ETS only when incorporated in it by amendment or revision. For undated references, the

latest edition of the publication referred to applies.
[1] GSM 01.04 (ETR 350): "Digital cellular telecommunication system (Phase 2+);
Abbreviations and acronyms".
[2] GSM 04.21 (ETS 300 945): "Digital cellular telecommunication system; Rate
adaption on the Mobile Station - Base Station System (MS - BSS) interface".
[3] GSM 07.02 (ETS 300 914): "Digital cellular telecommunication system
(Phase 2+); Terminal Adaptation Functions (TAF) for services using
asynchronous bearer capabilities".
[4] GSM 07.03 (ETS 300 584): "Digital cellular telecommunication system
(Phase 2); Terminal Adaptation Functions (TAF) for services using synchronous
bearer capabilities".
[5] GSM 09.04: "Digital cellular telecommunication system; Interworking between
the Public Land Mobile Network (PLMN) and the Circuit Switched Public Data
Network (CSPDN)".
[6] GSM 09.05: "Digital cellular telecommunication system; Interworking between
the Public Land Mobile Network (PLMN) and the Packet Switched Public Data
Network (PSPDN) for Packet Assembly/Disassembly facility (PAD) access".
[7] GSM 09.06 (ETS 300 975): "Digital cellular telecommunication system
(Phase 2+); Interworking between a Public Land Mobile Network (PLMN) and a
Packet Switched Public Data Network/Integrated Services Digital Network
(PSPDN/ISDN) for the support of packet switched data transmission services".
[8] GSM 09.07 (ETS 300 976): "Digital cellular telecommunications system
(Phase 2+); General requirements on interworking between the Public Land
Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or
Public Switched Telephone Network (PSTN)".
[9] CCITT Recommendation I.440 (Redbook): "ISDN user-network interface data
link layer - General aspects".
---------------------- Page: 9 ----------------------
SIST ETS 300 946 E3:2003
Page 8
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
[10] CCITT Recommendation I.441 (Redbook): "ISDN user-network interface, data
link".
[11] CCITT Recommendation Q.920 (Redbook): "ISDN user-network interface data
link layer - General aspects".
[12] CCITT Recommendation Q.921 (Redbook): "ISDN user-network interface - data
link".
[13] CCITT Recommendation Q.921bis: "Abstract test suites for LAPD conformance
tests".
[14] CCITT Recommendation Q.922: "ISDN data link layer specification for frame
mode bearer services".
[15] CCITT Recommendation V.42bis: "Data Compression for Data Circuit
Terminating Equipment (DCE) using Error Correction Procedures".
[16] CCITT Recommendation X.25 (Redbook): "Interface between Data Terminal
Equipment (DTE) and Data Circuit Terminating Equipment (DCE) for terminals
operating in Packet Mode and connected to Public Data Networks by dedicated
Circuit".
[17] ISO/IEC Recommendation 4335: "Information technology - Telecommunications
and information exchange between systems - High level data link control
(HDLC) procedures - Elements of procedures".
[18] ISO Recommendation 3309: "Information technology - Telecommunications and
information exchange between systems - High level data link control (HDLC)
procedures - Frame structure".
[19] ISO Recommendation 7498: "Information processing systems - Open Systems
Interconnection - Basic Reference Model".
[20] ISO Recommendation 8885: "Information technology - Telecommunication and
information exchange between systems - High-level data link control (HDLC)
procedures - General purpose XID frame information field content and format".
[21] ISO Recommendation 8886: "Information technology - Telecommunication and
information exchange between systems - Data link service definitions for Open
Systems interconnection".
[22] ISO Recommendation 8509: "Information processing systems - Open Systems
Interconnection - Service conventions".
[23] ISO/IEC Recommendation 7809: "Information technology - Telecommunication
and information exchange between systems - High-level data link control
(HDLC) procedures - Classes of procedures".
[24] ISO Recommendation 7776: "Information processing systems - High-level data
link control procedures - Description of the X.25 LAPB-compatible DTE data link
procedures".
2.1 Definitions and abbreviations
Abbreviations used in this ETS are listed in GSM 01.04 [1].
For the purposes of this ETS, the following definitions apply:

backwards compatibility: RLP defines several backwards-compatible versions. That means that a

newer version can interwork with an older one without changing the older one. This is realized by a fall

back mechanism during XID exchange.
---------------------- Page: 10 ----------------------
SIST ETS 300 946 E3:2003
Page 9
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998

command: An instruction represented in the RLP header, causing the receiving RLP entity to execute a

specific function.

frame check sequence: A field of redundant information based on a cyclic code, used for error detection.

I + S frame: An RLP frame that is used for user information transfer, carrying supervisory information

piggyback.

improper frame: An RLP frame having an FCS error or having a header the contents of which is

inconsistent with this Specification.

non-transparent: In PLMN data transmission, a configuration where at layer 2, protocol information of the

fixed network is mapped on RLP elements, and vice versa.

piggybacking: Means by which one and the same frame can carry both user information and RLP related

supervisory information.

response: A reply represented in the RLP-header, by which the sending RLP entity reports back about its

status.

RLP frame: A sequence of contiguous bits, representing an RLP procedural element.

RLP header: That part of an RLP frame that encodes either a command or a response, located at the

beginning of the RLP frame.

S frame: An RLP frame that contains supervisory information in the absence of user information.

transparent: In PLMN data transmission, a configuration where at layer 2 (and also at the layers above)

no protocol conversion takes place.
U frame: An RLP frame that contains unnumbered protocol control information.
3 Introduction
Three versions of RLP are defined:
- RLP version 0: single-link basic version;

- RLP version 1: single-link extended version (e.g. extended by data compression);

- RLP version 2: multi-link version

RLP uses one (single-link) or from 1 up to 4 (multi-link) physical links. However, the RLP multi-link version

is designed to be able to support up to 8 physical links. If, in the call setup signalling, either end indicates

that it cannot support multilink operation, neither end shall require usage of RLP-versions higher than 1.

RLP makes use of an underlying FEC (Forward Error Correction) mechanism. For RLP to perform

adequately it is assumed that the basic radio channel together with FEC provides for a block error rate of

less than 10 %, where a block consists of 240 or 576 bits (Further study on the BLER for 576-bit blocks is

needed). Furthermore, it is assumed that in case of multi-link RLP the difference of the delay between all

physical links is less than timer T4.

RLP frames are sent in strict alignment with the radio transmission. (For details, see GSM 04.21). RLP

frames are of a fixed size of 240 (TCH/F9.6 channel coding) or 576 bits (TCH/F14.4 channel coding)..

Whenever a frame is to be sent, the RLP entity has to provide the necessary protocol information to be

contained in it. Provision is made for discontinuous transmission (DTX).

RLP spans from the Mobile Station (MS) to the interworking function (IWF), located at the nearest Mobile

Switching Centre (MSC), or beyond. Depending on the exact location of the IWF, handover of the MS may

result in link-reset or even total loss of the connection.

In the terminology of HDLC, RLP is used in a balanced configuration, employing asynchronous operation,

i.e. either station has the right to set-up, reset, or disconnect a link at any time. Procedural means are

provided for to deal with contentious situations, should they ever occur.

RLP is full-duplex in the sense that it allows for information to be transferred in both directions

simultaneously.
---------------------- Page: 11 ----------------------
SIST ETS 300 946 E3:2003
Page 10
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
4 Frame structure
4.1 Basic frame structure

An RLP-frame has a fixed length of either 240 or 576 bits consisting of a header, an information field, and

an FCS (frame check sequence) field. The size of the components depends on the RLP version and on

the RLP frame. As a benefit of using strict alignment with underlying radio transmission there is no need

for frame delimiters (like flags etc.) in RLP. In consequence, there is no "bit-stuffing" necessary in order to

achieve code transparency. Frames cannot be aborted while being transmitted.
Header Information FCS
version 0 and 1, version 2 (U frames 16/24 bit 200/192 bit 24 bit
only)
version 2 (S and I+S frames only) 24 bit 192 bit 24 bit
b) 576 bit frame size
Header Information FCS
version 0, 1, and version 2 (U frames 16 bit 536 bit 24 bit
only)
version 2 (S and I+S frames only) 24 bit 528 bit 24 bit
Figure 1: Frame structure
4.2 RLP header

An RLP-header carries one of three types of control information, the first being unnumbered protocol

control information (U frames), the second being supervisory information (S frames), the third being user

information carrying supervisory information piggybacked (I + S frames).
4.3 Order of transmission

The header, as defined in clause 5.2, shall be transmitted from left to right. The FCS shall be transmitted

commencing with the highest order term. The order of bit transmission for the information field is from left

to right.
4.4 Frame check sequence
The FCS shall be the ones complement of the modulo 2 sum of:
a) the remainder of:
For 9.6/4.8 kbit/s channel coding:
216 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4

x (x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x +

3 2
x + x + x + 1)
For 14.4kbit/s channel coding:
552 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7
x (x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x + x
6 5 4 3 2
+ x + x + x + x + x + x + 1
divided modulo 2 by the generator polynomial:
24 23 21 20 19 17 16 15 13 8 7 5 4 2
x + x + x + x + x + x + x + x + x + x + x + x + x + x + 1
---------------------- Page: 12 ----------------------
SIST ETS 300 946 E3:2003
Page 11
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
and
b) the remainder of the division modulo 2 by the generator polynomial:
24 23 21 20 19 17 16 15 13 8 7 5 4 2
x + x + x + x + x + x + x + x + x + x + x + x + x + x + 1

of the product of x by the content of the frame, excluding the FCS field. (The first bit transmitted

corresponds to the highest order term.)

Implementation note: As a typical implementation, at the transmitter, the initial content of the register of

the device computing the remainder of the division is pre-set to all ones and is then modified by division by

the generator polynomial (as described above) of the header and information field; the ones complement

of the resulting remainder is transmitted as the 24 bit FCS sequence.

At the receiver, the initial content of the register of the device computing the remainder is pre-set to all

ones. The final remainder after multiplication by x and then division (modulo 2) by the generator

polynomial:
24 23 21 20 19 17 16 15 13 8 7 5 4 2
x + x + x + x + x + x + x + x + x + x + x + x + x + x + 1
of the serial incoming protected bits and the FCS will be:
23 0
0 1 1 0 1 1 0 1 1 0 0 0 1 0 0 1 0 0 1 1 0 0 0 0 (x to x , resp.)
in the absence of transmission errors.
5 Elements and procedure
5.1 Modes
An RLP entity can be in one of two modes:
- Asynchronous Balanced Mode (ABM)
- Asynchronous Disconnected Mode (ADM)
5.1.1 Asynchronous Balanced Mode (ABM)

In ABM, which is the data link operational mode, either RLP entity may send commands at any time and

may initiate response frame transmission without receiving explicit permission to do so from the other

RLP-station. In ABM, frames shall be used for information field transfer and/or to indicate status changes

in the RLP-station.
5.1.2 Asynchronous Disconnected Mode (ADM)

In ADM, which is the data-link non-operational mode, the RLP entity shall be logically disconnected from

the data link and shall, therefore, neither transmit nor accept numbered information frames.

The RLP entity shall, however, be permitted to transmit and accept NULL, DM, UI, TEST and XID frames.

Either RLP entity can issue an SABM command at any time, in order to terminate the ADM state. In that

case, entrance of the ABM state will be indicated by a UA response from the opposite station. If the

opposite station is not able to enter ABM, it will indicate this by a DM response. All commands other than

those mentioned above and any unsolicited response will be ignored in ADM under all circumstances.

5.2 Header and parameters
The formats defined for the header are listed in figure 2.
---------------------- Page: 13 ----------------------
SIST ETS 300 946 E3:2003
Page 12
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998
5.2.1 Generally used bits
NOTES: C/R = COMMAND/RESPONSE BIT
P/F = POLL/FINAL BIT
X = DON'T CARES
M M M M M
1 2 3 4 5
1 1 1 0 0 S A B M
0 0 1 1 0 U A
0 0 0 1 0 D I S C
S S 1 1 0 0 0 D M
1 2
0 0 R R 1 1 1 1 0 NULL
0 1 R E J 0 0 0 0 0 U I
1 0 R N R 1 1 1 0 1 X I D
1 1 S R E J 0 0 1 1 1 T E S T
1 0 0 0 1 REMAP
Versions 0 and 1:
NOTES: N(S) : Bit 4 low order bit
N(R) : Bit 11 low order bit
U C/R X X 1 1 1 1 1 1 P/F M1 M2 M3 M4 M5 X
______________ ______________
S C/R S1 S2 01 11 11 P/F N (R)
______________ ______________ ______________ ______________
I+S C/R S1 S2 N (S) P/F N (R)
bit 1 2 3 4 5 6 7 8 9 1011 1213 141516
Version 2:
NOTES: S = L2R Status Bit
N(S) : Bit 1 low order bit
N(R) : Bit 14 low order bit
U C/R X X 111111 P/FM1M2M3M4M5 X
______________ ______________
S X X X 011111 P/FC/RS1S2 N(R) XX
______________ ______________ ______________ ______________
I+S N(S) P/F C/R S1 S2 N(R) SX
bit 1 23456789 10 11 12131415161718192021222324
Figure 2: Header formats
5.2.1.1 Command/response bit, C/R

The C/R-bit is used to indicate whether the frame is a command or response frame and whether the

P/F-bit is to be interpreted as a poll or final bit, resp. For commands, the C/R bit shall be set to "1", for

responses it shall be set to "0".
5.2.1.2 Poll/Final bit, P/F

The P/F-bit is used to mark a special instance of command/response exchange. With a command, it is

called the P-bit, with a response, it is called the F-bit. In any one direction, only one P/F-bit exchange may

be outstanding at any time. A response with the F-bit set to "1" shall always reflect the latest receive status

of the RLP entity.

A P/F-bit exchange always starts with a command frame with the P-bit set to "1", which shall be answered

by a response frame with the F-bit set to "1" at the earliest response opportunity.

---------------------- Page: 14 ----------------------
SIST ETS 300 946 E3:2003
Page 13
ETS 300 946 (GSM 04.22 version 5.2.1): January 1998

No unsolicited F-bit = "1" is allowed. Such a frame shall be considered "improper" (see subclause 5.3.1).

In ABM, the use of the P/F-bit with numbered information exchange is only allowed for checkpoint-

recovery (see subclause 5.3.3).
5.2.2 Unnumbered frames, U
5.2.2.1 Set asynchronous balanced mode SABM (11100)

The SABM encoding is used as a command only. It is always used with the P-bit set to "1".

The SABM command is used either to initiate a link for numbered information transfer, i.e. to go from

ADM to ABM, or to reset a link already established for numbered information transfer. With an SABM

command, no information transfer is allowed.

When issuing an SABM, the RLP entity has set to zero its internal variables for sending and receiving

numbered information. The other RLP entity, on receiving an SABM command, will either confirm it by

setting to zero its internal variables for sending and receiving numbered information and then issuing an

UA (unnumbered acknowledgement) response or reject it by sending a DM (disconnected mode)

response. In the former case, both entities have entered ABM and numbered information transfer may

commence. In the latter case, both entities are in ADM.

When an SABM command is issued, a loss of information may occur. Appropriate action is in the

responsibility of the layers above.
5.2.2.2 Unnumbered Acknowledge. UA (00110)

The UA encoding is used as a response only. It is used to positively acknowledge an SABM or D

...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.