Updated: 26 October 2026 · 3 min read
VDES (VHF Data Exchange System) is a digital communication system in the maritime VHF band designed to extend AIS. It keeps AIS for identification and collision avoidance and adds much higher-capacity data channels, terrestrial and via satellite.
Why VDES?
AIS was built for collision avoidance at 9.6 kbit/s per channel. As more applications pushed data over AIS, channels became congested in busy waters, threatening the core safety function. VDES moves that data onto dedicated channels.
Components
| Component | Function | Notes |
|---|---|---|
| AIS | Identification, collision avoidance | Unchanged on AIS 1 and AIS 2 |
| ASM | Application specific messages: AtoN monitoring, weather, port information | Two dedicated channels (commonly 2027 and 2028), relieving AIS |
| VDE-TER | High-capacity ship–shore and ship–ship data | Merged VHF channels, many times AIS capacity |
| VDE-SAT | Data exchange via satellite | Coverage beyond shore VHF range |
The technical characteristics are set out in ITU-R M.2092; IALA’s G1117 – VDES Overview guides authorities.
Frequency roadmap
- WRC-15 allocated spectrum for the terrestrial components (ASM and VDE-TER).
- WRC-19 allocated spectrum for the satellite component (VDE-SAT uplink and downlink).
- Satellite VDES is now being trialled and standardised; IALA is holding a workshop on satellite VDES in Tokyo in November 2026.
VDES vs AIS
| AIS | VDES | |
|---|---|---|
| Main purpose | Identification, collision avoidance | Multi-service digital data exchange |
| Capacity | Low, congests easily | Many times higher |
| Coverage | VHF range | VHF range + global satellite |
| Authentication | No | Supports authentication and addressed messages |
| Compatibility | — | Includes AIS; legacy ships keep working |
What it means for aids to navigation
- AtoN monitoring over ASM channels instead of AIS.
- Broadcasting S-201 / S-125 AtoN data directly to ships.
- Satellite connectivity for remote offshore AtoN without mobile networks.
- Delivery of e-Navigation services such as VTS information and route exchange.
Phuc Nguyen Marine follows VDES standardisation closely and advises on AIS-to-VDES investment roadmaps. Contact us.
References: ITU-R M.2092; IALA G1117; iala.int.