SIST EN 302 842-4 V1.1.1:2006

SLOVENSKI STANDARD
01-marec-2006
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Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF air-ground and
air-air Digital Link (VDL) Mode 4 radio equipment; Technical characteristics and methods
of measurement for aeronautical mobile (airborne) equipment; Part 4: Point-to-point
functions
Ta slovenski standard je istoveten z: EN 302 842-4 Version 1.1.1
ICS:
33.060.99 Druga oprema za radijske Other equipment for
komunikacije radiocommunications
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
49.090 2SUHPDLQLQVWUXPHQWLY On-board equipment and
]UDþQLKLQYHVROMVNLKSORYLOLK instruments
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

ETSI EN 302 842-4 V1.1.1 (2005-07)
European Standard (Telecommunications series)

Electromagnetic compatibility
and Radio spectrum Matters (ERM);
VHF air-ground and air-air Digital Link (VDL)
Mode 4 radio equipment;
Technical characteristics and
methods of measurement
for aeronautical mobile (airborne) equipment;
Part 4: Point-to-point functions

2 ETSI EN 302 842-4 V1.1.1 (2005-07)

Reference
DEN/ERM-TG25-016-5-4
Keywords
aeronautical, radio, testing, VHF, digital
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ETSI
3 ETSI EN 302 842-4 V1.1.1 (2005-07)
Contents
Intellectual Property Rights.6
Foreword.6
Introduction .7
1 Scope.8
2 References.9
3 Definitions and abbreviations.9
3.1 Definitions.9
3.1.1 Basic reference model definitions.9
3.1.2 Service conventions definitions .9
3.1.3 General definitions.10
3.1.4 Definition of bit order.10
3.2 Abbreviations.10
4 General description of VDL Mode 4 mobile station point-to-point services.11
4.1 General.11
4.2 Data Link Service (DLS) and Link Management Entity (LME) .12
4.2.1 General.12
4.2.2 DLS timers.15
4.2.3 DLS counters.15
4.2.4 Toggle bit (T).15
4.2.5 State variables (T and T ) .16
t r
4.2.6 Initialize Bit (IB).16
4.2.7 More bit (M) .16
4.2.8 Priority (pr).16
4.2.9 Message fragmentation and concatenation .16
4.2.10 DLS procedures.16
4.2.10.1 Selection of DLS procedures.16
4.2.10.2 Short transmission procedures .17
4.2.10.3 Long transmission procedures.17
4.2.11 Linking transmissions.19
4.2.11.1 Types of linking .19
4.2.11.2 Combined RTS / DATA DLPDUs.19
4.2.11.3 Combined DATA / ACK DLPDUs.19
4.2.11.4 Combined RTS / ACK DLPDUs .19
4.2.11.5 Combined CTS / ACK DLPDUs .19
4.2.12 Ground-air link management.19
4.2.13 Air-air link management.20
4.3 Additional VSS services.20
5 Minimum performance specification under standard test conditions.20
5.1 DLS sublayer.20
5.1.1 General.20
5.1.1.1 Services.20
5.1.1.2 Data transfer.21
5.1.1.3 DATA DLPDU duplicate suppression and sequencing .21
5.1.1.4 Error detection.21
5.1.1.5 Station identification.21
5.1.1.6 Broadcast addressing.21
5.1.1.7 DLS Priority.21
5.1.1.8 DLS Link control DLPDUs .22
5.1.2 DLS protocol specification .22
5.1.2.1 State variables.22
5.1.2.2 DLS burst formats.22
5.1.3 DLS system parameters.26
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4 ETSI EN 302 842-4 V1.1.1 (2005-07)
5.1.4 DLS procedures.28
5.1.4.1 Setting of re-transmission parameter.28
5.1.4.2 Selection of user data packet for transmission .28
5.1.4.3 Selection of transmission procedures.30
5.1.4.4 Short transmission procedures .30
5.1.4.5 Long transmission procedures.31
5.1.4.6 No link with sender .33
5.1.4.7 User data packet reception .34
5.1.4.8 Receipt of ACK DLPDU .34
5.1.4.9 Link reset.35
5.1.4.10 Linking DLS DLPDU transmissions.36
5.1.4.11 CTRL DLPDU.36
5.1.4.12 Procedures for air-air communication.37
5.2 Link management entity sublayer.37
5.2.1 Services.37
5.2.1.1 General.37
5.2.1.2 Link provision.38
5.2.1.3 Link change notifications.38
5.2.1.4 CTRL DLPDU.38
5.2.1.5 Broadcast link management burst .39
5.2.2 Control (CTRL) parameter formats .39
5.2.2.1 Encoding.39
5.2.2.2 General purpose information parameters .39
5.2.2.3 Mobile-initiated information parameters.43
5.2.2.4 Ground-initiated modification parameters .44
5.2.2.5 Ground-initiated information parameters.47
5.2.3 LME timers and parameters.49
5.2.3.1 General.49
5.2.3.2 Counter L1 (maximum number of missed reservations) and Timer TL3 (inter-miss timer).50
5.2.3.3 Timer TL1 (maximum link overlap time) .50
5.2.3.4 Parameters TL2 (link initialization time) .51
5.2.3.5 Timer TL4 (leave generation latency).51
5.2.4 CTRL DLPDU types and procedures .51
5.2.5 CTRL transmission procedures.55
5.2.5.a Frequency management procedures.55
5.2.5.1 Link connectivity procedures.55
5.2.5.2 Ground Station Identification.55
5.2.5.3 Link establishment.56
5.2.5.4 Mobile-initiated handoff.57
5.2.5.5 Mobile-requested ground-initiated handoff.58
5.2.5.6 Ground-initiated handoff.58
5.2.5.7 Ground-requested mobile-initiated handoff.59
5.2.5.8 Ground-requested broadcast handoff .59
5.2.5.9 Ground-commanded autotune.60
5.2.6 VDL Mode 4 Mobile SubNetwork Dependent Convergence Function (SNDCF).60
5.2.6.1 Frame mode SNDCF.60
5.3 Additional VSS requirements.60
5.3.1 Additional VSS quality of service parameters.60
5.3.1.1 Parameter Q5 (VSS retransmission parameters) .60
5.3.2 Unicast request protocol specification .61
5.3.2.1 Unicast request parameters.61
5.3.2.2 Unicast request transmission procedures .62
5.3.3 Information transfer request protocol specification .62
5.3.3.1 Information transfer request parameters.62
5.3.3.2 Information transfer request transmission procedures .64
5.3.3.3 Information transfer request acknowledgement procedures.64
5.3.4 Retransmission procedures.64
6 General design requirements.65
7 Protocol test procedures.65
7.1 General.65
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5 ETSI EN 302 842-4 V1.1.1 (2005-07)
7.2 Required test rig .65
7.3 Protocol test-suite description methodology .66
7.4 Detailed protocol test procedures .66
7.4.1 Test-suite overview.66
7.4.2 Declarations.69
7.4.3 Constraints.69
7.4.3.1 Abbreviations.69
7.4.3.1.1 Subfield mnemonics.69
7.4.3.1.2 Special characters used in the subfield definitions .70
7.4.3.1.3 Station addresses and positions .70
7.4.3.1.4 VDL bursts.71
7.4.3.2 Test cases.97
7.4.3.2.1 Test case macros.98
7.4.3.2.2 Test case descriptions .100
Annex A (informative): Cross reference matrix .174
Annex B (informative): Bibliography.184
History .189

ETSI
6 ETSI EN 302 842-4 V1.1.1 (2005-07)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This European Standard (Telecommunications series) has been produced by ETSI Technical Committee
Electromagnetic compatibility and Radio spectrum Matters (ERM).
The present document is part 4 of a multi-part deliverable covering the VHF air-ground and air-air Digital Link (VDL)
Mode 4 radio equipment; Technical characteristics and methods of measurement for aeronautical mobile (airborne)
equipment, as identified below:
Part 1: "Physical layer";
Part 2: "General description and data link layer";
Part 3: "Additional broadcast aspects";
Part 4: "Point-to-point functions".
The present document is accompanied by an equivalent ground-based standard, EN 301 842 [4] parts 1 to 4, covering
the VHF air-ground Data Link (VDL) Mode 4 radio equipment; Technical characteristics and methods of measurement
for ground-based equipment.
NOTE: Minimum Operational Performance Specifications (MOPS) are also being developed for VDL Mode 4.
EUROCAE have previously published Interim MOPS for VDL Mode 4 (see bibliography) which are a
sub set of EN 302 842-1, 2, 3 and 4. EN 302 842-1, 2, 3 and 4 complies with the requirements of CEC
Mandate M/318.
National transposition dates
Date of adoption of this EN: 22 July 2005
Date of latest announcement of this EN (doa): 31 October 2005
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 April 2006
Date of withdrawal of any conflicting National Standard (dow): 30 April 2006

ETSI
7 ETSI EN 302 842-4 V1.1.1 (2005-07)
Introduction
The present document states the technical specifications for Very High Frequency (VHF) Digital Link (VDL) Mode 4
aeronautical mobile (airborne) radio transmitters, transceivers and receivers for air-ground and air-air communications
operating in the VHF band, using Gaussian Filtered Frequency Shift Keying (GFSK) modulation with 25 kHz channel
spacing and capable of tuning to any of the 25 kHz channels from 118,000 MHz to 136,975 MHz as defined in
ICAO VDL SARPs [2].
The present document may be used to produce tests for the assessment of the performance of the equipment. The
performance of the equipment submitted for type testing should be representative of the performance of the
corresponding production model.
The present document has been written on the assumption that:
• the type test measurements will be performed only once, in an accredited test laboratory and the measurements
accepted by the various authorities in order to grant type approval;
• if equipment available on the market is required to be checked it will be tested in accordance with the methods
of measurement specified in the present document or a documented alternative approved by the certifying
authority;
• equipment comply with EN 302 842-1 [5] and EN 302 842-2 [6].
NOTE: The present document has been produced with a view to maintaining consistency of numbering with the
equivalent standard for ground equipment (EN 301 842 [4]). Where requirements are the same, they have
been given the same number. Some new airborne requirements have been inserted between requirements
that were sequential in EN 301 842 [4]. This has led to a non-standard form of numbering for new
requirements in some places.
ETSI
8 ETSI EN 302 842-4 V1.1.1 (2005-07)
1 Scope
The present document provides part 4 of the technical specifications for Very High Frequency (VHF) Digital Link
(VDL) Mode 4 aeronautical mobile (airborne) radio transmitters, transceivers and receivers for air-ground and air-air
communications operating in the VHF band, using Gaussian Filtered Frequency Shift Keying (GFSK) modulation with
25 kHz channel spacing and capable of tuning to any of the 25 kHz channels from 118,000 MHz to 136,975 MHz as
defined in ICAO VDL SARPs [2].
The present document is designed to ensure that equipment certified to it will be compatible with the relevant
ICAO VDL SARPs [2] and ICAO VDL4 Technical Manual [1].
Manufacturers should note that in future the tuning range for the transmitter may also cover any 25 kHz channel from
112,000 MHz to 117,975 MHz and the receiver(s) may cover any 25 kHz channel from 108,000 MHz to 117,975 MHz.
The present document applies to "aeronautical mobile (airborne and as applicable also ground vehicles)" equipment
which will hereinafter be referred to as "mobile" equipment.
The scope of the present document is limited to mobile stations. The equivalent specification for ground stations is
EN 301 842 [4].
A description of the scope of the VDL Mode 4 system is provided in part 2 of these technical specifications
(see EN 302 842-2 [6], clause 1).
EN 302 842-1 [5] deals with tests of the physical layer, EN 302 842-2 [6] deals with core link layer functionality and
EN 302 842-3 [7] with additional broadcast functionality. The present document deals with tests of the datalink layer
(DLS) and the link layer sufficient to support point-to-point functionality. Note that, as described in EN 302 842-2 [6], a
system supporting point-to-point functionality is required to conform to EN 302 842-1 [5], EN 302 842-2 [6] and the
specification in the present document.
The present document includes:
• references, definitions and abbreviations are provided in clauses 2 and 3;
• clause 4 describes the VDL Mode 4 mobile station point-to-point functions;
• clause 5 performance specifications for the VDL Mode 4 mobile station;
• clause 6 provides general design requirements;
• clause 7 provides protocol tests for the point-to-point functions of the system;
• a document history is contained in clause 8;
• annex A provides a detailed cross-reference to the relevant requirements contained in
ICAO VDL4 Technical Manual [1].
Note that the system can support a very wide range of functions. It is not practical to provide specific tests for all
aspects of functionality. The approach used is to provide detailed tests for the core point-to-point functionality and to
provide tests of those remaining requirements which, if wrongly implemented, could cause a deterioration in the service
offered by other VDL Mode 4 stations.
Mandating and Recommendation Phrases
a) "Shall":
- The use of the word "Shall" indicates a mandated criterion; i.e. compliance with the particular procedure
or specification is mandatory and no alternative may be applied.
b) "Should":
- The use of the word "Should" (and phrases such as "It is recommended that.", etc.) indicates that though
the procedure or criterion is regarded as the preferred option, alternative procedures, specifications or
criteria may be applied, provided that the manufacturer, installer or tester can provide information or data
to adequately support and justify the alternative.
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9 ETSI EN 302 842-4 V1.1.1 (2005-07)
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
[1] ICAO 9816: "Manual on VHF Digital Link (VDL) Mode 4 - Part 2: Detailed Technical
Specifications". First Edition 2004.
[2] ICAO Annex 10 to the Convention on International Civil Aviation: "Aeronautical
Telecommunications,Volume III: Communication Systems, Part I: Digital Data Communication
Systems, Chapter 6".
[3] ICAO 9705-CD: "Manual of Technical Provisions for the Aeronautical Telecommunication
Network (ATN)".
[4] ETSI EN 301 842 (all parts): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
VHF air-ground Data Link (VDL) Mode 4 radio equipment; Technical characteristics and methods
of measurement for ground-based equipment".
[5] ETSI EN 302 842-1: "Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF
air-ground and air-air Digital Link (VDL) Mode 4 radio equipment; Technical characteristics and
methods of measurement for aeronautical mobile (airborne) equipment; Part 1: Physical layer".
[6] ETSI EN 302 842-2: "Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF
air-ground and air-air Digital Link (VDL) Mode 4 radio equipment; Technical characteristics and
methods of measurement for aeronautical mobile (airborne) equipment; Part 2: General description
and data link layer".
[7] ETSI EN 302 842-3: "Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF
air-ground and air-air Digital Link (VDL) Mode 4 radio equipment; Technical characteristics and
methods of measurement for aeronautical mobile (airborne) equipment; Part 3: Additional
broadcast aspects".
3 Definitions and abbreviations
3.1 Definitions
3.1.1 Basic reference model definitions
See EN 302 842-2 [6], clause 3.1.1.
3.1.2 Service conventions definitions
See EN 302 842-2 [6], clause 3.1.2.
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10 ETSI EN 302 842-4 V1.1.1 (2005-07)
3.1.3 General definitions
For the purposes of the present document, the terms and definitions given in EN 302 842-1 [5] clause 3.1.3,
EN 302 842-2 [6] clause 3.1.3 and the following apply:
long transmission procedure: procedure that allows transfer of DATA packets in reserved slots, avoiding the loss rates
and delays associated with random access
NOTE: This includes the ability to link sequences of DATA packets, providing continuous transfer in reserved
slots.
More bit (M): bit that controls message fragmentation and concatenation
NOTE: It is set to zero to indicate the end of a message. It is set to 1 to indicate that it is part of a fragmented
message and that there are more fragments to follow.
Network Setup Connection Oriented Protocol (NSCOP): protocol that enables a ground-air link between mobiles
priority (pr): priority of a message, or, in the case of an RTS, the priority of the requested data
short transmission procedure: procedure for the sending of a single data packet. It contains a reservation for a
subsequent acknowledgement
Toggle bit (T): bit that allows detection and rejection of duplicate DLPDUs
NOTE: The T bit is alternately set to 1 and 0 on each successive DATA transmission, except for retransmissions.
Zero-Overhead Connection-Oriented Protocol (ZOCOP): protocol that enables an air-air link between mobiles
3.1.4 Definition of bit order
In the tables included in the present document to illustrate the format of bursts, the following order is implied:
a) bit order in each burst subfield shall be indicated by subscript numbers. Bit 1 shall indicate the least significant
bit; and
b) bits shall be transmitted octet by octet, starting with the first octet in each table, and within each octet the
rightmost bit (as shown in the tables) shall be transmitted first.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ACK ACKnowledgement (burst)
ADM ADMinistration identifier
ADS-B Automatic Dependent Surveillance - Broadcast
ARS Administration Region Selector
ATN Aeronautical Telecommunication Network
CMD Command
CPR Compact Position Reporting
CRC Cyclic Redundancy Code
CTRL ConTRoL (DLPDU)
CTS Clear To Send (burst)
DLE Data Link Entity
DLPDU Data Link Protocol Data Unit
DLS Data Link Service
DM Disconnected Mode (DLPDU)
erid extended reservation ID
FRMR FRaMe Reject (DLPDU)
GFSK Gaussian Filtered Frequency Shift Keying
GSC Global Signalling Channel
GSIF Ground Station Information Frame
hex hexadecimal
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11 ETSI EN 302 842-4 V1.1.1 (2005-07)
HO Hand Off
IA-5 International Alphabet - 5
IB Initialize Bit
ICAO International Civil Aviation Organization
ID IDentity
INFO INFOrmation (DLPDU)
ISO International Organization for Standardization
IS-SME Intermediate System - System Management Entity
LCR Link Connection Refused
LE Link Establishment
lg length
LME Link Management Entity
M More bit
MAC Media Access Control
MOPS Minimum Operational Performance Specification
neg negotiation
NETs Network Entity Titles
NM Nautical Mile
NSCOP Network Setup Connection Orientated Protocol
O Optional
p priority
PCO Point of Control and Observation
PECT Peer Entity Contact Table
PI Parameter Identifier
PI Parameter Identifier
pr priority
QoS Quality of Service
Res Reserved header bits
RF Radio Frequency
rid reservation ID
RSP Response
RTS Request To Send (DLPDU)
SARPs Standards And Recommended Practices
seq sequence
SNDCF SubNetwork Dependent Convergence Function
SZOM Start Zero Overhead Mode (DLPDU)
T Toggle bit
UCTRL Unacknowledged ConTRoL data broadcast (DLPDU)
UDATA Unacknowledged DATA broadcast (DLPDU)
UINFO Unacknowledged user INFOrmation data broadcast (DLPDU)
VDL VHF Digital Link
VHF Very High Frequency
VME VDL Management Entity
VSS VDL Mode 4 Specific Services
ZOCOP Zero-Overhead Connection-Oriented Protocol
4 General description of VDL Mode 4 mobile station
point-to-point services
4.1 General
A description of VDL Mode 4 is provided in EN 302 842-2 [6]. This clause provides a description of the datalink layer
and associated services of the VSS and LME required to support point-to-point communications.
The specifications in the present document provide air-to-ground and air-to-air point-to-point services based on the
ICAO Technical Manual. The present document includes:
• Point-to-point data and control data transfer functions from the DLS.
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12 ETSI EN 302 842-4 V1.1.1 (2005-07)
• Point-to-point link control within the LME.
Note that the present document covers the mobile response to the establishment, termination and handover of links
between ground stations. Decisions made by ground stations to establish, terminate or handover links between ground
stations are local issues and beyond the scope of these specifications.
In most respects, the VDL Mode 4 mobile station follows the provisions of the ICAO standards material for VDL
Mode 4. Within the ICAO standard, there are some requirements which apply explicitly only to ground stations.
Requirements on ground stations are covered in EN 301 842 (all parts) [4].
The scope of the present document is for an mobile station supporting point-to-point applications. Hence the ability to
support broadcast communication is not included in the present document.
Note that, although certain protocols will not be used by the mobile station, the ability to recognize the use by ground
stations of these protocols and to respond in a consistent manner is an mobile station requirement and is included in the
present document.
4.2 Data Link Service (DLS) and Link Management Entity
(LME)
4.2.1 General
The Data Link Service (DLS) provides a point-to-point protocol supporting both air-to-ground and air-to-air exchanges.
For air-to-ground exchanges, connection management is handled by the LME, using a Negotiated Setup
Connection-Orientated Protocol (NSCOP). For air-to-air exchanges, the DLS defines a ZOCOP protocol with link
establishment and dis-establishment controlled by timers, allowing rapid link negotiation between aircraft.
The specifications in the present document assume that VDl Mode 4 will be used with a network based on ATN
protocols (see ICAO ATN SARPs [3]). It should be noted that, in future, it could support other network protocols.
The DLS is a simple information exchange protocol which provides:
a) Explicit acknowledgement of each DATA packet.
b) Mechanisms to provide data transfer in reserved slots, avoiding loss rates and delays associated with random
access. This includes the ability to link sequences of DATA packets, providing continuous transfer in reserved
slots.
c) Packet fragmentation, to allow long user data packets to be transferred across the link in fragments optimally
matched to the link conditions.
d) Duplicate detection and suppression via a simple toggle bit mechanism.
e) Explicit support for the 15 priority levels defined for the ATN, including the ability for high priority messages
to be sent in the middle of a fragmented low priority message.
As illustrated in figure 4.1, the DLS:
• Provides services to external users in order to support point-to-point, multi-cast and broadcast
communications.
• Provides services to the LME to support link management.
• Supports services between peer DLSs.
• Uses the services of the VSS in order to send and receive messages.
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13 ETSI EN 302 842-4 V1.1.1 (2005-07)
DLS User
LME
DLS
Peer DLS
VSS
Figure 4.1: Functions of the DLS
Figure 4.2 illustrates the use of various services provided by the DLS and VSS in supporting the DLS User and the
LME.
DLS User LME
Directed Data Broadcast Data
(INFO, CTRL) (UDATA)
Connection Management (IB/SZOM)
Message Segmentation (M-bit)
Delivery Order (T-bit)
DLS
Short Long Short Long
Acknowledged Acknowledged Unacknowledged Unacknowledged
Information
Unicast Request
Transfer
Reservation
Request
VSS
General
Response Retransmission
Protocol
Figure 4.2: Services provided by the DLS and VSS
Protocols for short unacknowledged broadcast data have already been specified in the core link layer functionality
(EN 302 842-2 [6]).
A DLS Burst consists of:
• Burst ID (fixed or variable).
• One or two DLPDUs.
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14 ETSI EN 302 842-4 V1.1.1 (2005-07)
The following DATA DLPDUs (data link protocol data units) are defined:
• CTRL: Used by the LME to establish and maintain links for NSCOP communication.
• INFO: Contains a user data field.
• UDATA: Either a UCTRL or a UINFO. Enables the broadcast of user data - it is unacknowledged.
The following RTS DLPDUs are defined:
• CTRL_RTS: Sent to request the sending of link maintenance data.
• INFO_RTS: A request to send user data (for long transmission procedures).
• UDATA_RTS: A request to send broadcast data.
The following ACK, CTS and other DLS link control DLPDUs are defined:
• UDATA_CTS: This DLPDU is a clear to send in response to a UDATA_RTS.
• INFO_ACK: An acknowledgment of the previous INFO DLPDU.
• INFO_CTS: A clear to send (for long transmission procedures).
• CTRL_ACK: An acknowledgment of the previous CTRL DLPDU.
• FRMR: Used to reset the link.
• FRMR_ACK: Sent to acknowledge receipt of FRMR.
• DM/DISC (Disconnected Mode): Used to indicate that a DLS DLPDU has been received when no link has
been initialized.
• DM/FRMR – Used to indicate that a DLS DLPDU has been received when the link is in the process of being
initialized.
• SZOM: sent in combination with an INFO, INFO_RTS or INFO_ACK to establish a link for ZOCOP
communication.
Table 4.1 shows the DLS burst types.
Table 4.1: DLPDU contents
Toggle More Bit Priority Negotiation Initialize Length
Bit (T) (M) (pr) subfield (neg) bit IB (lg)

CTRL
INFO
UDATA
CTRL_RTS
INFO_RTS
UDATA_RTS
UDATA_CTS
INFO_ACK
INFO_CTS
CTRL_ACK
CTRL_CTS
FRMR_ACK
FRMR
DM/DISC
DM/FRMR
SZOM
ETSI
15 ETSI EN 302 842-4 V1.1.1 (2005-07)
Where:
• Toggle Bit (T): This is used for duplicate detection and rejection.
• More Bit (M): This is set
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