SIST EN 301 841-2 V1.1.1:2006
(Main)Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF air-ground Digital Link (VDL) Mode 2; Technical characteristics and methods of measurement for ground-based equipment; Part 2: Upper layers
- Abstract
The present document applies to VDL Mode 2 ground-air digital communications using Differential Eight Phase Shift Keying (D8PSK), intended for channel increments of 25 kHz. The VDL Mode 2 system provides data communication exchanges between aircraft and ground-based systems. The scope of the present document is limited to ground-based stations. The VDL Mode 2 system is designed to be a Ground/Air sub-system of the Aeronautical Telecommunication Network (ATN) using the AM(R)S band and it is organized according to the Open Systems Interconnection (OSI) model (defined by ISO). It shall provide reliable subnetwork services to the ATN system. The present document provides functional specifications for ground-based radio equipment intended to be used for ground-air data communications. The present document is derived from the following documents:
• VDL Mode 2 SARPs version 3.0. ICAO Annex 10 Volume III part I [1].
• ED 92a [2]: "MOPS for an Airborne VDL Mode-2 Transceiver Operating in the frequency range 118-136.975 MHz" (2003), which specifies the airborne transceiver.
The present document consists of two parts:
• the first part provides functional specifications and test procedures for physical layer and MAC sub-layer;
• the second part provides functional specifications and test procedures for link and sub-network access layers.
- Status
- Published
- Publication Date
- 28-Feb-2006
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Mar-2006
- Due Date
- 01-Mar-2006
- Completion Date
- 01-Mar-2006
- Mandate
- M/239
SIST EN 301 841-2 V1.1.1:2006 is the Slovenian adoption of ETSI EN 301 841-2 for VHF air-ground Digital Link (VDL) Mode 2 ground-based equipment. It specifies the upper-layer technical characteristics and measurement methods for ground stations that use Differential Eight Phase Shift Keying (D8PSK) and 25 kHz channel increments in the Aeronautical Telecommunication Network (ATN). It is written for people who need to design, integrate, test, or assess ground equipment for VDL Mode 2 data communications.
What does SIST EN 301 841-2 V1.1.1:2006 specify?
SIST EN 301 841-2 V1.1.1:2006 specifies the upper layers of VDL Mode 2 for ground-based stations. The standard covers how the ground equipment supports link management and subnetwork services between aircraft and ground systems, and it places those functions in the ATN and OSI framework.
The document is organized as follows:
| Clause / annex | What it covers |
|---|---|
| Clause 4 | General architecture of VDL Mode 2 in the OSI model |
| Clause 5 | Link layer protocols and services, including MAC, DLS and VDL management entity functions |
| Clause 6 | Subnetwork layer protocols and services, based on SNAcP |
| Clause 7 | The VDL mobile SubNetwork Dependent Convergence Function (SNDCF) |
| Clause 8 | Link layer test cases and test summary |
| Annex A | Informative bibliography |
The scope is limited to ground-based stations. The standard is derived from VDL Mode 2 SARPs and from the airborne transceiver specification that defines the aircraft side of the system. In practice, that means the document tells a ground-station designer what the ground equipment must do, while the aircraft-side behavior is defined elsewhere.
What are the key requirements of SIST EN 301 841-2 V1.1.1:2006?
SIST EN 301 841-2 V1.1.1:2006 defines how VDL Mode 2 ground equipment exchanges frames, manages links, and supports ATN subnetwork services. The most important requirements are in clause 5 for the link layer, clause 6 for the subnetwork layer, clause 7 for SNDCF behavior, and clause 8 for conformance testing.
Link layer organization and MAC access
Clause 4 splits the link layer into a Media Access Control (MAC) sublayer, a Data Link Services (DLS) sublayer, and a Link Management Entity (LME). The MAC sublayer uses Carrier Sense Multiple Access (CSMA) to control channel access, while the DLS sublayer uses Aviation VHF Link Control (AVLC) procedures derived from High-level Data Link Control (HDLC).
This matters because a ground implementation has to separate radio access from frame control and link management. The MAC interface uses AV2M-UNITDATA and AV2M-STATUS primitives, so equipment must exchange AVLC frames without changing their contents.
Clause 5.1 also defines MAC service behavior such as multiple access and channel congestion handling, and it names the key MAC parameters: TM1, TM2, persistence p, and counter M1. In practice, these parameters control how aggressively a station retries access to a busy channel.
Frame handling, addressing, and retransmission
Clause 5.2 defines DLS behavior, including frame sequencing, error detection, transmit queue handling, and retransmission. Error detection uses the Frame Check Sequence (FCS), and the frame format follows AVLC rules based on HDLC.
The addressing rules are important for interoperability. Clause 5.2.4 defines the air-ground status bit, the Command/Response bit, DLS address structure, and broadcast addressing. The standard distinguishes aircraft addresses, ICAO-administered ground-station addresses, ICAO-delegated ground-station addresses, and broadcast forms such as all aircraft, all ground stations, and all stations.
Clause 5.2 also defines retransmission and flow-control behavior with parameters such as T1, T2, T3, T4, N1, N2, and k. In practice, these parameters determine when a frame is resent, how long the station waits for acknowledgements, and how many outstanding frames the link can carry.
Link management and XID exchange
Clause 5.3 covers the VDL Management Entity, including link provision, link change notifications, and Exchange Identity (XID) parameters. These XID exchanges carry public and private parameters that configure link establishment, handoff, modulation support, signal quality, alternative ground stations, aircraft location, timers, and connection management.
This is the part that makes VDL Mode 2 usable in moving-aircraft operations. The ground system can tell the aircraft about nearby stations, support handoff, and exchange parameters for link recovery or expedited subnetwork connection handling.
Several XID procedures are defined for different cases, including link establishment, link parameter modification, aircraft-initiated handoff, ground-based initiated handoff, broadcast handoff, commanded autotune, and expedited subnetwork connection management. For a reader, the practical point is that the ground station must respond correctly to link changes and maintain service while the aircraft moves between ground systems.
Subnetwork layer and packet services
Clause 6 defines the SubNetwork Access Protocol (SNAcP) and states that it conforms to ISO/IEC 8208 except where the standard says otherwise. It describes subnetwork connection management, packet fragmentation and reassembly, error recovery, and connection flow control.
Clause 6.4 sets the subnetwork service parameters used in Mode 2, including timers, retry counts, packet size, transmit window size, acknowledgment window size, and the channel limits LTC and HTC. These settings matter because they control the size and timing of ATN packet traffic over the VDL link.
Clause 6.6 then describes how the subnetwork connection is established and maintained, including how unsupported facilities are handled. That is the part implementers use when they need to map VDL Mode 2 behavior to packet-mode networking.
SNDCF behavior and context retention
Clause 7 defines the VDL mobile SubNetwork Dependent Convergence Function (SNDCF). The key requirement is that the SNDCF supports maintaining context, such as compression tables, across subnetwork calls, and that at least two switched virtual circuits can share a context.
This matters during handoff and reestablishment because packet ordering can change. Implementers need to preserve state carefully so that compression and higher-layer continuity remain valid across multiple calls.
Test coverage
Clause 8 gives link-layer test cases for MAC behavior, link establishment, retransmission, acknowledgements, link monitoring, illegal reception, GSIF timing, link overlap, handoff, frame collision precedence, and selective acknowledgement. It also maps the tests to observation points between the physical, MAC, data link, and subnetwork layers.
For an engineering team, this clause is the practical bridge between the specification and verification. It shows what to exercise in the implementation and where to observe the result.
What terms does SIST EN 301 841-2 V1.1.1:2006 define?
- AVLC - Aviation VHF Link Control, the frame-oriented link control protocol used for data exchange and error detection.
- DLE - Data Link Entity, the part of the link layer that handles data transfer, state machines, and retransmission.
- LME - Link Management Entity, the function that controls link establishment, maintenance, handoff, and link-related XID procedures.
- SNAcP - SubNetwork Access Protocol, the packet-mode subnetwork protocol used across the VHF air-ground subnetwork.
- SNDCF - SubNetwork Dependent Convergence Function, the function that adapts subnetwork behavior and can preserve context across calls.
- XID - eXchange ID, the frame used to exchange link and management parameters between stations.
- GSIF - Ground Station Information Frame, the frame used to send ground-station information and support link setup or handoff.
Who uses SIST EN 301 841-2 V1.1.1:2006?
SIST EN 301 841-2 V1.1.1:2006 is used by teams working on VDL Mode 2 ground stations, ATN air-ground networking, and interoperability testing. Typical users include radio equipment manufacturers, avionics and ground-system integrators, test laboratories, and technical staff responsible for conformance and acceptance checks.
It is also relevant to quality and procurement staff who need to confirm that a ground-based VDL Mode 2 solution supports the expected link, handoff, and subnetwork functions. In practice, the document helps those roles compare implementations against the same ground-station behavior.
Which standards are used with SIST EN 301 841-2 V1.1.1:2006?
- Annex 10 to the Convention on International Civil Aviation, ICAO - provides the VDL Mode 2 SARPs framework that the standard follows.
- DO-186A - gives the airborne MOPS that define the aircraft-side radio behavior referenced by this standard.
- ISO/IEC 7498-1 - supplies the OSI basic reference model used to structure the protocol layers.
- ISO/IEC 10731 - provides the OSI service-convention rules used for defining services and primitives.
- ISO/IEC 8208 - defines the packet layer behavior that the subnetwork layer follows, with Mode 2-specific adaptations.
- ISO/IEC 15802-1 - defines MAC service concepts used for the MAC sublayer model.
- ISO/IEC 13239 - defines HDLC procedures used as the basis for AVLC.
- ETSI EN 301 841-1 - covers the physical layer and MAC sublayer for the same VDL Mode 2 equipment family.
- ITU-T Recommendation X.25 - provides the packet-mode DTE/DCE interface model referenced by the subnetwork layer.
What does the SIST EN 301 841-2 V1.1.1:2006 document contain?
The document contains architecture diagrams, protocol descriptions, parameter tables, state machines, and conformance tests. Figures show the VDL Mode 2 place in the ATN/OSI model, the link-layer architecture, primitive sequences, and the main DLE and LME state diagrams.
Clause 5 contains detailed XID parameter definitions and encodings, including ground and aircraft information, address-related fields, handoff support, modulation support, and timer-related parameters. Clause 6 contains the packet-format rules and the subnetwork service parameters used for ATN packet handling.
Clause 8 contains test architectures and scenarios for MAC and DLS behavior, with expected statistical results for timing-related tests and a summary table that maps each test to its observation points. That makes the document useful both for design verification and for laboratory conformance testing.
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Frequently Asked Questions
SIST EN 301 841-2 V1.1.1:2006 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF air-ground Digital Link (VDL) Mode 2; Technical characteristics and methods of measurement for ground-based equipment; Part 2: Upper layers". This standard covers: The present document applies to VDL Mode 2 ground-air digital communications using Differential Eight Phase Shift Keying (D8PSK), intended for channel increments of 25 kHz. The VDL Mode 2 system provides data communication exchanges between aircraft and ground-based systems. The scope of the present document is limited to ground-based stations. The VDL Mode 2 system is designed to be a Ground/Air sub-system of the Aeronautical Telecommunication Network (ATN) using the AM(R)S band and it is organized according to the Open Systems Interconnection (OSI) model (defined by ISO). It shall provide reliable subnetwork services to the ATN system. The present document provides functional specifications for ground-based radio equipment intended to be used for ground-air data communications. The present document is derived from the following documents: • VDL Mode 2 SARPs version 3.0. ICAO Annex 10 Volume III part I [1]. • ED 92a [2]: "MOPS for an Airborne VDL Mode-2 Transceiver Operating in the frequency range 118-136.975 MHz" (2003), which specifies the airborne transceiver. The present document consists of two parts: • the first part provides functional specifications and test procedures for physical layer and MAC sub-layer; • the second part provides functional specifications and test procedures for link and sub-network access layers.
The present document applies to VDL Mode 2 ground-air digital communications using Differential Eight Phase Shift Keying (D8PSK), intended for channel increments of 25 kHz. The VDL Mode 2 system provides data communication exchanges between aircraft and ground-based systems. The scope of the present document is limited to ground-based stations. The VDL Mode 2 system is designed to be a Ground/Air sub-system of the Aeronautical Telecommunication Network (ATN) using the AM(R)S band and it is organized according to the Open Systems Interconnection (OSI) model (defined by ISO). It shall provide reliable subnetwork services to the ATN system. The present document provides functional specifications for ground-based radio equipment intended to be used for ground-air data communications. The present document is derived from the following documents: • VDL Mode 2 SARPs version 3.0. ICAO Annex 10 Volume III part I [1]. • ED 92a [2]: "MOPS for an Airborne VDL Mode-2 Transceiver Operating in the frequency range 118-136.975 MHz" (2003), which specifies the airborne transceiver. The present document consists of two parts: • the first part provides functional specifications and test procedures for physical layer and MAC sub-layer; • the second part provides functional specifications and test procedures for link and sub-network access layers.
SIST EN 301 841-2 V1.1.1:2006 is classified under the following ICS (International Classification for Standards) categories: 33.060.99 - Other equipment for radiocommunications; 33.100.01 - Electromagnetic compatibility in general. The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN 301 841-2 V1.1.1:2006 is associated with the following European legislation: Standardization Mandates: M/239. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
SIST EN 301 841-2 V1.1.1:2006 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2006
(OHNWURPDJQHWQD]GUXåOMLYRVWLQ]DGHYHY]YH]L]UDGLMVNLPVSHNWURP (50 ±
'LJLWDOQHSRYH]DYH9+)]UDNWODQDþLQ±7HKQLþQHNDUDNWHULVWLNHLQPHULOQH
PHWRGH]DWDOQRRSUHPR±GHO =JRUQMHSODVWL
Electromagnetic compatibility and Radio spectrum Matters (ERM); VHF air-ground Digital
Link (VDL) Mode 2; Technical characteristics and methods of measurement for ground-
based equipment; Part 2: Upper layers
Ta slovenski standard je istoveten z: EN 301 841-2 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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
European Standard (Telecommunications series)
Electromagnetic compatibility
and Radio spectrum Matters (ERM);
VHF air-ground Digital Link (VDL) Mode 2;
Technical characteristics and
methods of measurement
for ground-based equipment;
Part 2: Upper layers
2 ETSI EN 301 841-2 V1.1.1 (2004-03)
Reference
DEN/ERM-TG25-015-2
Keywords
aeronautical, radio, testing
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ETSI
3 ETSI EN 301 841-2 V1.1.1 (2004-03)
Contents
Intellectual Property Rights.10
Foreword.10
Introduction .10
1 Scope.11
2 References.11
3 Definitions and abbreviations.12
3.1 Definitions.12
3.1.1 Basic reference model definitions.12
3.1.2 Service conventions definitions .12
3.1.3 General definitions.13
3.2 Abbreviations.13
4 General architecture of VDL Mode 2.14
5 Link layer protocols and services functional specifications.15
5.1 MAC sublayer specifications .16
5.1.1 MAC services.16
5.1.1.1 Multiple access.16
5.1.1.2 Channel congestion.16
5.1.2 MAC service system parameters .17
5.1.2.1 Timer TM1 (inter-access delay timer).17
5.1.2.2 Timer TM2 (channel busy timer).17
5.1.2.3 Parameter p (persistence) .17
5.1.2.4 Counter M1 (maximum number of access attempts) .17
5.1.3 Description of procedures.17
5.1.3.1 Channel sensing.17
5.1.3.2 P-persistent CSMA access times.17
5.1.3.3 Inter-access interval.18
5.1.3.4 Channel access procedure .18
5.1.3.4.1 Purpose.18
5.1.3.4.2 Use.18
5.1.3.4.3 Procedure.18
5.1.3.5 AVLC frame reception.18
5.1.3.5.1 Purpose.18
5.1.3.5.2 Use.18
5.1.3.5.3 Procedure.18
5.2 Data link layer service protocol specifications.19
5.2.1 Interface with MAC sub layer.19
5.2.1.1 Sequence of primitives.19
5.2.2 Data Link State Machines.20
5.2.2.1 LME state machine.21
5.2.2.2 DLE top state machine .22
5.2.2.3 DLE data transfer state diagram.23
5.2.2.4 DLE selective reject state machines.24
5.2.2.4.1 SRM mode Sending SREJ.24
5.2.2.4.2 SRM mode Receiving SREJ.24
5.2.2.4.3 FRM mode.25
5.2.2.5 DLE termination state machine.26
5.2.3 Services.26
5.2.3.1 Received frame sequencing procedure.26
5.2.3.1.1 Purpose.26
5.2.3.1.2 Use.26
5.2.3.1.3 Procedure.26
5.2.3.2 Error detection procedure.26
5.2.3.2.1 Purpose.26
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4 ETSI EN 301 841-2 V1.1.1 (2004-03)
5.2.3.2.2 Use.26
5.2.3.2.3 Procedure.27
5.2.3.3 Station identification.27
5.2.3.4 Broadcast addressing.27
5.2.3.5 Data transfer.27
5.2.4 Frame format.27
5.2.4.1 Address structure.27
5.2.4.2 Address fields0.0.3.3.27
5.2.4.2.1 Air-ground status bit.28
5.2.4.2.2 Command/response status bit .28
5.2.4.2.3 Data link service addresses.28
5.2.4.2.4 Address type.28
5.2.4.2.5 Aircraft specific addresses.28
5.2.4.2.6 ICAO-administered ground station specific addresses .28
5.2.4.2.7 ICAO-delegated ground station specific addresses .28
5.2.4.3 Broadcast address.28
5.2.4.3.1 Encoding.29
5.2.4.4 Link control field .29
5.2.4.5 Information field.29
5.2.5 Transmit queues management.29
5.2.6 Data link service system parameters.30
5.2.6.1 Parameter T1 (delay before non acknowledged retransmission).30
5.2.6.2 Parameter T2 (delay before acknowledgment).31
5.2.6.3 Parameter T3 (link initialization time) .31
5.2.6.4 Parameter T4 (maximum delay between transmissions).31
5.2.6.4.1 Recommendation.31
5.2.6.5 Parameter N1 (maximum number of bits of any frame) .31
5.2.6.6 Counter N2 (maximum number of transmissions) .31
5.2.6.7 Parameter k (window size).32
5.2.7 DLE retransmission timers .32
5.2.8 Description of procedures.32
5.2.8.1 Procedure retransmission schedule .32
5.2.8.1.1 Purpose.32
5.2.8.1.2 Use.32
5.2.8.1.3 Procedure.32
5.2.8.2 Procedure frame retransmission .32
5.2.8.2.1 Purpose.32
5.2.8.2.2 Use.32
5.2.8.2.3 Procedure.33
5.2.8.3 Procedure XID frame retransmission.33
5.2.8.3.1 Purpose.33
5.2.8.3.2 Use.33
5.2.8.3.3 Procedure.33
5.2.8.4 Procedure link monitoring.33
5.2.8.4.1 Purpose.33
5.2.8.4.2 Use.33
5.2.8.4.3 Procedure.33
5.2.8.5 Procedure link recovery .33
5.2.8.5.1 Purpose.33
5.2.8.5.2 Use.33
5.2.8.5.3 Procedure.33
5.2.9 Modes of operation .34
5.2.9.1 Operational mode.34
5.2.9.2 Non-operational mode.34
5.2.9.2.1 DISC frame.34
5.2.9.2.2 DM frame.34
5.2.9.3 Frame reject mode.34
5.2.9.4 Sent selective reject mode.34
5.2.10 Use of the P/F bit .34
5.2.10.1 General.34
5.2.10.2 INFO frames.35
5.2.10.3 Recommendation.35
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5 ETSI EN 301 841-2 V1.1.1 (2004-03)
5.2.10.4 Unnumbered frames.35
5.2.11 Unnumbered command frame collisions .35
5.2.11.1 DLE procedures.35
5.2.11.2 LME procedures.35
5.2.12 XID frame.35
5.2.13 Broadcast.35
5.2.14 Information transfer.35
5.2.14.1 Void.35
5.2.14.1.1 Eliminate redundant frames.35
5.2.14.1.2 Recommendation.36
5.2.14.1.3 Recommendation.36
5.2.14.1.4 Recommendation.36
5.2.14.1.5 Procedures for transmission.36
5.2.14.1.6 Recommendation.36
5.2.14.1.7 Recommendation.36
5.2.14.1.8 Recommendation.36
5.2.14.2 SREJ frame.36
5.2.14.3 FRMR frame.37
5.2.14.4 UA frame.37
5.2.14.5 UI frame.37
5.2.14.6 TEST frame.37
5.3 VDL management entity.37
5.3.1 Services.37
5.3.1.1 Link provision.37
5.3.1.2 Link change notifications.37
5.3.2 Exchange identity (XID) parameter.38
5.3.2.1 Encoding.38
5.3.2.2 Public parameters.38
5.3.2.2.1 HDLC public parameter set identifier .38
5.3.2.2.2 Timer T1 parameter.39
5.3.2.3 VDL private parameters.39
5.3.2.4 General purpose information private parameters .39
5.3.2.4.1 VDL private parameter set identifier.39
5.3.2.4.2 Connection management parameter.39
5.3.2.4.3 Signal Quality Parameter (SQP).40
5.3.2.4.4 XID sequencing parameter .41
5.3.2.4.5 AVLC specific options parameter .41
5.3.2.4.6 Expedited subnetwork connection parameter .42
5.3.2.4.7 LCR cause parameter .42
5.3.2.5 Aircraft-initiated information private parameters .43
5.3.2.5.1 Modulation support parameter.43
5.3.2.5.2 Acceptable alternate ground station parameter.44
5.3.2.5.3 Destination airport parameter .44
5.3.2.5.4 Aircraft location parameter.44
5.3.2.6 Ground-based initiated modification private parameters .45
5.3.2.6.1 Autotune frequency parameter.45
5.3.2.6.2 Replacement ground station list .45
5.3.2.6.3 Timer T4 parameter.45
5.3.2.6.4 MAC persistence parameter .45
5.3.2.6.5 Counter M1 parameter.46
5.3.2.6.6 Timer TM2 parameter .46
5.3.2.6.7 Timer TG5 parameter .46
5.3.2.6.8 T3min parameter.46
5.3.2.6.9 Ground station address filter parameter.47
5.3.2.6.10 Broadcast connection parameter.47
5.3.2.7 Ground-based initiated information private parameters.48
5.3.2.7.1 Frequency support list .48
5.3.2.7.2 Airport coverage indication parameter .48
5.3.2.7.3 Nearest airport parameter .48
5.3.2.7.4 ATN router NETs parameter .49
5.3.2.7.5 Ground-based system mask parameter .49
5.3.2.7.6 Timer TG3 parameter .49
ETSI
6 ETSI EN 301 841-2 V1.1.1 (2004-03)
5.3.2.7.7 Timer TG4 parameter .50
5.3.2.7.8 Ground station location parameter.50
5.3.3 VME service system parameters.50
5.3.4 VME procedures.50
5.3.4.1 Minimum frequency dwell time procedure.50
5.3.4.1.1 Purpose.50
5.3.4.1.2 Use.51
5.3.4.1.3 Procedure.51
5.3.4.1.4 Recommendation.51
5.3.4.2 Maximum idle activity time procedure .51
5.3.4.2.1 Purpose.51
5.3.4.2.2 Use.51
5.3.4.2.3 Procedure.51
5.3.4.3 Maximum time between transmissions procedure .51
5.3.4.3.1 Purpose.51
5.3.4.3.2 Use.51
5.3.4.3.3 Procedure.51
5.3.4.4 Maximum time between GSIFs.52
5.3.4.4.1 Purpose.52
5.3.4.4.2 Use.52
5.3.4.4.3 Procedure.52
5.3.4.5 Maximum link overlap time procedure.52
5.3.4.5.1 Purpose.52
5.3.4.5.2 Use.52
5.3.4.5.3 Procedure.52
5.3.5 Description of LME procedures.52
5.3.5.1 Frequency management procedures.56
5.3.5.1.1 Frequency search.56
5.3.5.1.2 Frequency recovery.56
5.3.5.2 Link connectivity procedures.57
5.3.5.3 Ground station identification.57
5.3.5.4 Link establishment.57
5.3.5.4.1 Aircraft initiation.57
5.3.5.4.2 General ground response .57
5.3.5.4.3 Exceptional cases.58
5.3.5.5 Link parameter modification.58
5.3.5.5.1 Ground-based initiation.58
5.3.5.5.2 General aircraft response.58
5.3.5.5.3 Recommendation.58
5.3.5.6 Aircraft-initiated handoff.58
5.3.5.6.1 Aircraft handoff.58
5.3.5.6.2 Site selection preference.58
5.3.5.6.3 Recommendation.59
5.3.5.6.4 Interaction of LMEs.59
5.3.5.6.5 General ground response .59
5.3.5.6.6 Disconnecting old link.59
5.3.5.6.7 Exceptional cases.59
5.3.5.7 Aircraft-requested ground-initiated handoff .59
5.3.5.7.1 Aircraft action.59
5.3.5.7.2 General ground response .60
5.3.5.7.3 Exceptional cases.60
5.3.5.8 Ground-based initiated handoff0.60
5.3.5.8.1 Ground action.60
5.3.5.8.2 General aircraft response.60
5.3.5.8.3 Disconnecting old link.60
5.3.5.8.4 Exceptional cases.60
5.3.5.8.5 Recommendation.60
5.3.5.9 Ground-based requested aircraft-initiated handoff0.4.4.9.60
5.3.5.9.1 Ground action.61
5.3.5.9.2 General aircraft response.61
5.3.5.9.3 Exceptional cases.61
5.3.5.9.4 Recommendation.61
ETSI
7 ETSI EN 301 841-2 V1.1.1 (2004-03)
5.3.5.10 Ground-based requested broadcast handoff .61
5.3.5.10.1 Ground action.61
5.3.5.10.2 Aircraft response.61
5.3.5.10.3 Exceptional cases.62
5.3.5.11 Ground-based commanded autotune.62
5.3.5.11.1 Ground action.62
5.3.5.11.2 General aircraft response.62
5.3.5.11.3 Exceptional cases.62
5.3.5.12 Expedited subnetwork connection management .62
5.3.5.12.1 Initiating station of subnetwork connection management .63
5.3.5.12.2 General responder action.63
5.3.5.12.3 Exceptional cases.63
6 Subnetwork layer protocols and services functional specifications .63
6.1 Architecture.63
6.1.1 Access points.63
6.2 Services.63
6.2.1 Subnetwork connection management.64
6.2.2 Packet fragmentation and reassembly.64
6.2.3 Error recovery.64
6.2.3.1 Recommendation.64
6.2.4 Connection flow control.64
6.2.4.1 Recommendation.64
6.3 Packet format.64
6.3.1 General format identifier .64
6.3.2 Calling and called DTE addresses .64
6.3.2.1 Encoding.65
6.3.2.1.1 Address field.
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