Audio coding and transmission for aeronautical broadcasts via satellite

A system design for aeronautical audio broadcasts, with a C-band uplink and an L-band downlink, via Inmarsat space segments is presented. Near-transparent-quality compression of 5-kHz bandwidth audio at 17 kbit/s is achieved based on a hybrid technique that employs linear predictive modeling and transform-domain residual quantization. High-resolution spectral modeling, block-size adaptation, and adaptive bit allocation are key components of the design. Concatenated Reed-Solomon/convolutional codes with quadrature phase shift keying are selected for bandwidth and power efficiency. An RF bandwidth of 20 kHz per channel, and a decoded bit error rate of 10^-6 with an E _b/N₀ of 4.5 dB are obtained. 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. The transponder occupancy analysis for 72 audio channels reveals ample remaining capacity for emerging aeronautical services