scope:

The present document states the minimum performance requirements for radio transmitters receivers and transceivers for ground VHF Datalink mode 4 (VDL mode 4) equipment intended to be used for air-ground data communications, operating in the VHF band (118,000 MHz to 137,000 MHz and optionally 113,000 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) mode 4 Standards and Recommended Practices (SARPs) [1].

Manufacturers should note that in the future, all or part of the frequency band 108,000 MHz to 117,975 MHz may 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 digital communications. The scope of the present document is limited to ground stations.

The VDL mode 4 system provides data communication exchanges between aircraft and ground systems supporting surveillance applications. The supported modes of communication for VDL mode 4 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 subnetwork services to the ATN system.

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 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.

The present document includes:

• Clause 2 provides references to relevant documents.

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

• Clause 4 provides a general description and architecture of VDL Mode 4 including reference to the OSI model, communication services, ADS-B and operational scenarios.

• Clause 5 provides functional specifications applicable to the physical layer including transmitter/receiver requirements and the modulation scheme.

• Clause 6 provides general equipment requirements.

• Clause 7 provides general design requirements.

• Clause 8 covers general test conditions, environmental tests and calibration.

• Clause 9 provides detailed test procedures for the physical layer.

The full physical layer tests are provided which correspond closely to the standard set of tests used for other VDL systems.

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.) indicate 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.