VDES-VHF Data Exchange System

Introduction

VDES-VHF Data Exchange System: A New Maritime Communication System: Maritime communication is essential for the safety, security and efficiency of navigation and operations at sea. However, the current maritime communication systems face some challenges, such as limited bandwidth, low data rate, high interference and congestion. To address these challenges, a new maritime communication system called VHF Data Exchange System (VDES) has been developed and is expected to be implemented in the near future.

What is VDES?

VDES is a radio communication system that operates between ships, shore stations and satellites on Automatic Identification System (AIS), Application Specific Messages (ASM) and VHF Data Exchange (VDE) frequencies in the Marine Mobile VHF band. VDES consists of three components:

• AIS: A component that uses the Gaussian Minimum Shift Keying (GMSK) modulation scheme and provides identification, position and other information of vessels and shore stations.
• ASM: A component that uses the GMSK modulation scheme and provides additional information for specific applications, such as navigational warnings, meteorological forecasts, ice charts and port information.
• VDE: A component that uses higher capacity modulation schemes, such as 16-ary Orthogonal Frequency Division Multiplexing (16-OFDM) or 16-ary Quadrature Amplitude Modulation (16-QAM), and provides high-speed data exchange for various applications, such as e-navigation, maritime cloud, remote sensing and autonomous ships.

VDES can exchange digital data in the ship-to-ship, ship-to-shore and shore-to-ship directions using both terrestrial and satellite components. The terrestrial component of VDES uses nine dedicated channels in the VHF maritime mobile band, while the satellite component of VDES uses two channels allocated by the World Radio Conference 2019. The satellite component of VDES enables global coverage and enhances the reliability and availability of the system.

What are the benefits of VDES?

VDES is seen as an effective and efficient use of radio spectrum, building on the capabilities of AIS and addressing the increasing requirements for data through the system. Some of the benefits of VDES are:

• Higher data rate: VDES can provide data rates up to 32 kbps for terrestrial VDE and up to 64 kbps for satellite VDE, which are much higher than the data rate of AIS (9.6 kbps).
• Higher capacity: VDES can support up to 200 ARPA targets (TT) and 1000 AIS targets, as well as fusion of TT and AIS targets. VDES can also support more users and applications than AIS.
• Higher reliability: VDES uses advanced techniques such as error correction coding, interleaving and diversity reception to improve the quality of service and reduce the probability of message loss². VDES also uses a network protocol that optimizes data communication so that each message is transmitted with a high confidence of reception.
• Higher security: VDES supports encryption and authentication mechanisms to protect the confidentiality and integrity of data. VDES also supports selective addressing and access control to prevent unauthorized access or misuse of data.
• Higher functionality: VDES supports various applications that enhance maritime safety, security and efficiency, such as e-navigation, maritime cloud, remote sensing and autonomous ships. VDES also supports R-Mode as a contingency navigation system that uses terrestrial or satellite signals to provide position information in case of failure or interference of GNSS signals.

What is the roadmap for VDES?

VDES will continue to be developed over the next few years in accordance with the roadmap published by IALA³. The roadmap consists of four phases:

• Phase 1: Development of technical specifications for terrestrial VDE (VDE-T) and ASM
• Phase 2: Development of technical specifications for satellite VDE (VDE-S) and R-Mode
• Phase 3: Development of performance standards for terrestrial VDE (VDE-T), satellite VDE (VDE-S) and R-Mode
• Phase 4: Development of guidelines for implementation and operation of VDES

The first phase has been completed in 2018 with the publication of ITU-R M.2092-0 Recommendation on technical characteristics for a universal shipborne automatic identification system using time division multiple access in the maritime mobile band. The second phase is expected to be completed in 2022 with the publication of ITU-R M.2092-1 Recommendation on technical characteristics for a VHF data exchange system in the maritime mobile band. The third and fourth phases are expected to be completed in 2023 and 2024 respectively.

Conclusion

VDES is a new maritime communication system that provides higher data rate, capacity, reliability, security and functionality than the current systems. VDES comprises AIS, ASM and VDE components that operate on terrestrial and satellite channels in the VHF maritime mobile band. VDES supports various applications that enhance maritime safety, security and efficiency, such as e-navigation, maritime cloud, remote sensing and autonomous ships. VDES also supports R-Mode as a contingency navigation system. VDES is expected to be implemented in the near future according to the roadmap published by IALA.