Aeronautical audio broadcasting via satellite

Communications Satellite Corp., Clarksburg, MD.
01/1993; -1:33-38.


A system design for aeronautical audio broadcasting, with C-band uplink
and L-band downlink, via Inmarsat space segments is presented.
Near-transparent-quality compression of 5-kHz bandwidth audio at 20.5
kbit/s is achieved based on a hybrid technique employing linear
predictive modeling and transform-domain residual quantization.
Concatenated Reed-Solomon/convolutional codes with quadrature phase
shift keying are selected for bandwidth and power efficiency. RF
bandwidth at 25 kHz per channel, and a decoded bit error rate at 10(exp
-6) with E(sub b)/N(sub o) at 3.75 dB are obtained. An interleaver,
scrambler, modem synchronization, and frame format were designed, and
frequency-division multiple access was selected over code-division
multiple access. A link budget computation based on a worst-case
scenario indicates sufficient system power margins. Transponder
occupancy analysis for 72 audio channels demonstrates ample remaining
capacity to accommodate emerging aeronautical services.

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