scope:

The present document states the minimum performance requirements for radio transmitters, receivers and transceivers for ground-based VHF Datalink mode 4 (VDL mode 4) equipment intended to be used for air-ground data communications, operating in the VHF band (117,975 MHz to 136,975 MHz and optionally 112,000 MHz to 117,975 MHz) allocated to the aeronautical mobile service. It is designed to ensure that equipment certified to it will be compatible with the relevant ICAO VHF Digital Link (VDL) Standards and Recommended Practices (SARPs) and VDL Mode 4 Technical Manual (TM) [1].

Manufacturers should note that all or part of the frequency band 108,000 MHz to 117,975 MHz might become available for aeronautical communications.

The present document applies to Gaussian-filtered Frequency Shift Keying (GFSK) systems, with channel separations of 25 kHz intended for air-ground communications. The scope of the present document is limited to ground base stations.

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

• broadcast and point-to-point communication;

• air-air and ground-air;

• operation without ground infrastructure.

VDL Mode 4 is designed to be an Air/Ground subsystem 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 provides reliable sub network services to the ATN system. Other networks can also be supported but has not been in focus for the present document.

The present document specifies functional specifications of radio transmitters, receivers and transceivers at ground-based VHF communication equipment intended to be used for air-ground and air-air data communications. The present document is derived from the specifications:

• Mode 4 standards produced under the auspices of the International Civil Aviation Organization (ICAO) [1].

• Other relevant standards as defined in clause 2.

EN 301 842-1 [4] deals with tests of the physical layer. EN 301 842-2 [5] deals with tests of the link layer sufficient to support broadcast functionality including requirements and tests sufficient to recognize and respond to transmissions associated with point-to-point communication. The present document contains additional requirements and tests sufficient to support the following specific broadcast applications

• Automatic Dependent Surveillance - Broadcast (ADS-B);

• Traffic Information Service - Broadcast (TIS-B);

• Flight Information Service - Broadcast (FIS-B);

• GNSS Augmentation Service - Broadcast (GNS-B).

The present document includes:

• references, definitions, abbreviations and symbols are provided in clauses 2 and 3;

• clause 4 describes the VDL Mode 4 ground station functionality to support ADS-B, TIS-B, FIS-B and GNS-B;

• clause 5 provides performance specifications for the VDL Mode 4 ground station supporting ADS-B, TIS-B, FIS-B and GNS-B Services;

• clause 6 provides general design requirements;

• clause 7 provide protocol tests which emphasis the ADS-B, TIS-B, FIS-B and GNS-B functions of the system;

• clause A provides a detailed cross-reference to the relevant requirements contained in reference [1];

• clause B 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 functionality. The approach used is to provide detailed tests for the core functionality to support ADS-B, FIS-B, TIS-B and GNS-B focusing on the system 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.