Eurocontrol plans VDL-2 equipment for CPDLC and traditional radios for voice, but available radio channels have been doubled by implementing 8.33kHz channel spacing, which has not been done in the USA. Advantages: mature technology, and system ensures total separation of the voice/CPDLC modes, providing back-up if one fails; also, VDL-2 has spare capacity beyond its CPDLC role such that it can replace ACARS.
US FAA plans VDL-3 digital radio combining voice and datalink in one signal. Advantages: may have a longer service life than VDL-2 when air traffic management datalink usage expands beyond CPDLC.
Source: Flight International
