A 22 K Bd mobile video telephone scheme

The complexity, image quality, bandwidth efficiency, and robustness issues of a mobile video telephone scheme for personal communications networks (PCNs) are addressed. The motion-compensated 55 kb/s subband codec using seven nonuniformly spaced active bands with bandspecific scanning and runlength coding achieves image peak signal-to-noise ratios (SNR) of around 38 dB, associated with good communications quality for monochrome common intermediate format images sampled at 10 frames per second. The motion dependent bitrate fluctuations are smoothed out by buffering with adaptive quantizer control feedback. The video bits are then sorted into two sensitivity classes and error protected by a twin-class binary BCH scheme. The separately BCH-encoded more significant bits (MSB) and less significant bits (LSB) are transmitted via separate subchannels of the 16-level quadrature amplitude modulator (16-QAM), having different integrity. The overall signaling rate becomes 22 kBd. No equalizer has to be used yet unimpaired image quality is achieved for channel SNR in excess of 20 dB