Comprehensive Evaluation of VHF Digital Link Mode 3 System

KITAORI Jun and MATSUKUBO Yuji

Abstract:
VDL (VHF Digital Link) Mode 3 is a digital communication system for ATS (Air Traffic Services). Mode architecture is based on TDMA (Time Division Multiple Access) technology and has various useful functions for ATS such as simultaneous communications of both digital voice and data, voice anti-blocking, urgent downlink request and so on.

We have developed a Mode 3 experimental system consist of four radio stations and a central station, which is compliant with ICAO (International Civil Aviation Organization) VDL Mode 3 SARPs (Standards and Recommended Practices) and technical manual. In this paper, we report comprehensive evaluation results for the system such as flight experiments, interoperability tests with the Mode 3 system of FAA (Federal Aviation Administration) and subjective evaluations for operation. Main results are summarized as follows;
- Data communication of Mode 3 can reach to the line of sight distance around. The limit of digital voice communication is a little farther than the line of sight since powerful error correction is implemented on voice coder.
- The voice quality and the functionalities of Mode 3 are better than traditional analog voice communication.
- Some defects which affect the datalink operation on ATN (Aeronautical Telecommunication Network) are found. We have reported the defects and countermeasures to ICAO.