VHF Data Link
VHF radio data transmission , engl. VHF Datalink , or VDL for short , is a process for exchanging data between aircraft and ground stations. It is a further development of the VHF - aeronautical radio , the only analog data passes as language.
VDL Mode1 is based on the ACARS protocol, which can send very short data telegrams with a data rate of 2.4 kbps. A common standard in Europe is VDL Mode2 , often equated with the designation Controller Pilot Data Link Communication (CPDLC). It achieves a capacity of 20kbps with not too much traffic.
VDL Mode3 was developed by the FAA and is favored in America. It transmits 4 data channels that can also send out digitized speech.
The latest standard is VDL Mode4 , which is not yet in use. It is not only suitable for the transmission from aircraft to ground like the standards Mode1 to Mode3, but also from aircraft to aircraft.
| default | Modulation method | max data rate | Multiple access |
|---|---|---|---|
| VDL Mode1 | FSK | 2.4 kbps | CSMA |
| VDL Mode2 | D8PSK | 31.5 kbps | CSMA |
| VDL Mode3 | D8PSK | 31.5 kbps | TDMA |
| VDL Mode4 | GFSK | 19.2 kbps | Self-organizing TDMA |