scope:

The present document applies to the following radio equipment types:

• 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 [i.2].

The present document provides part 2 of the technical specifications.

The present document is designed to ensure that equipment certified to it will be compatible with the relevant ICAO VDL SARPs [i.2] and ICAO VDL4 Technical Manual [i.1].

NOTE: In clause 5.1.4, Tertiary time, as described by the ICAO VDL4 Technical Manual [i.1], has not been included as a requirement in the present document due to the opinion of the ETSI Working Group that insufficient evidence was available to be able to verify correct operation of a "floating network" of stations operating on tertiary time.

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 in some cases 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 [10], [11], [12] and [13].

The VDL Mode 4 system provides digital communication exchanges between aircraft and ground based systems and other aircraft supporting surveillance and communication applications. The supported modes of communication include:

• broadcast and point-to-point communication;

• broadcast services including Automatic Dependent Surveillance - Broadcast (ADS-B), Traffic Information Service - Broadcast (TIS-B), Flight Information Service - Broadcast (FIS-B) capabilities and GNSS Augmentation Service - Broadcast (GNS-B);

• air-air and ground-air services;

• operation without ground infrastructure.

VDL Mode 4 is designed to be an Air/Ground subsystem of the Aeronautical Telecommunication Network (ATN) (see ICAO ATN SARPs [i.3]) using the AM(R)S band and it is organized according to the Open Systems Interconnection (OSI) model (defined by ISO). It provides reliable sub network services to the ATN system. Other networks can also be supported but have not been the focus of the present document.

The present document is derived from the standards and specifications in:

• ICAO VDL4 Technical Manual [i.1] produced under the auspices of the International Civil Aviation Organization (ICAO).

• Other relevant standards as defined in clause 2.

It is envisaged that manufacturers may provide equipment supporting:

• broadcast services only;

• point-to-point services only;

• both broadcast and point-to-point services.

EN 302 842-1 [2] deals with tests of the physical layer. The present document defines the core link layer requirements for the VDL Mode 4 mobile station necessary to support all types of equipment. This includes a simple position broadcast functionality.

The present document deals with tests of the link layer sufficient to support core link layer functionality, and it also includes requirements and tests sufficient to recognize and respond to transmissions associated with point-to-point communication. The present document does not address requirements for the full ADS-B message set, or for other broadcast applications that can be supported by the VDL Mode 4 equipment. These are covered by EN 302 842-3 [6]. Detailed requirements for point-to-point communication are beyond the scope of the present document, but can be found in EN 302 842-4 [7]. EN 302 842-4 [7] also includes the interface to the Aeronautical Telecommunication Network (ATN) as defined in ICAO ATN SARPs [i.3].

As the measured values of equipment performance may be a function of the method of measurement, standard test conditions and methods of test are recommended in the present document.

The present document is organized as follows:

• Clause 2 provides references to relevant documents.

• Clause 3 provides general definitions, abbreviations and symbols used.

• Clause 4 describes the VDL Mode 4 mobile station link layer.

• Clause 5 provides performance specifications for the VDL Mode 4 mobile station and any additional mobile functions necessary to support ground station co-ordination.

• Clause 6 provides general design requirements.

• Clause 7 provides protocol tests for core link layer functions.

• Annex A provides a detailed cross-reference to the relevant requirements contained in ICAO VDL4 Technical Manual [i.1];

• Annex B provides a description of the ISO/IEC 9646 [5] test methodology;

• Annex C provides a Bibliography;

• A document history.

Note that the system can support a very wide range of functions. It is not practical to provide specific tests for all aspects of its functionality. The approach used is to provide detailed tests for the core link layer 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. Therefore:

• a detailed set of protocol tests are provided for the core link layer functionality necessary to support broadcast functions;

• a detailed test of position encoding and decoding is provided because of the importance of position in the management of the VDL Mode 4 link specifically and the need to support ADS-B applications in general.

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.