chapter  4
8 ACARS
Pages 2

European solution of reducing the channel

spacing to 8.33 kHz. VDL Mode 3 takes a 25 kHz

frequency assignment and divides it into 120 ms

frames with four 30 ms time slots (each of which

constitutes a different channel). Thus Mode 3

employs time division multiplexing (TDM)

rather than frequency division multiplexing

(FDM) used in the European system. Note that

VDL Mode 3 is the only planned VDL mode that

is designed to support voice and data traffic on

the same frequency.