Transmission of Subband-Coded Images via Mobile Channels

The feasibility of a mobile video handset is investigated via 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 Bose-Chaudhuri-Hocquenghem (BCH) codecs and spectrally efficient 16-level quadrature amplitude modulation (16-QAM). Motion-compensated nonuniform 7-band subband coding (SBC) with subband-specific scanning, adaptive quantization (Q), run-length coding (RLC), and adaptive buffering to equalize bit-rate fluctuations offer good objective and subjective image quality at moderate complexity and a bit rate of 55 kbit/s. Using a twin-class embedded-BCH error protection as well as pilot symbol and diversity-assisted 16-QAM, our 22-kBd candidate system yields unimpaired image quality for average channel signal-to-noise ratios (SNR) in excess of about 16-18 dB, when the mobile speed is 4 mi/h, an SNR value readily maintained in personal-communications mobile systems characterized by small cells.