Transmission of subband-coded images via mobile channels

The feasibility of a mobile video handset is investigated for Rayleigh-fading channels, where transmissions must be confined to the channel's coherence bandwidth to avoid the deployment of complex high-power-consumption channel equalizers. This necessitates the utilization of a low-bit-rate image codec error-protected by embedded low-complexity BCH codecs and spectrally efficient 16-level quadrature amplitude modulation (16 QAM). Motion-compensated nonuniform seven-band subband coding with subband-specific scanning, adaptive quantization, runlength coding, and adaptive buffering to equalize bit-rate fluctuations offer good objective and subjective image quality at moderate complexity and a bit-rate of 55 kb/s. Using a twin-class embedded-BCH error protection as well as pilot symbol 16 QAM and diversity assisted, the 22 kBd candidate system yields unimpaired image quality for average channel signal-to-noise ratios (SNRs) in excess of about 16-18 dB, when the mobile speed is 4 miles/h.<
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