Multi-mode Wireless Videophony

A comparative s t u d y of arbitrari ly programmable, but fixed-rate videophone codecs using quar ter common intermediate format (QCIF) video sequences scanned a t 10 frames/s is offered. These codecs were designed t o allow direct replacement of mobile radio voice codecs i n second generation wireless systems, such as t h e Pan-European GSM, t h e American IS-54 a n d IS-95 a s well as t h e Japanese systems, operating at 13, 8, 9.6 a n d 6.7 kbps, respectively, although be t t e r video quality is maintained over higher-rate, 32kbps cordless systems, such as t h e Japanese P H S a n d t h e European D E C T a n d C T 2 systems. Best overall performance was achieved by our vector-quantised codecs, followed by t h e discrete cosine transformed a n d t h e quadtree-based schemes, which were characterised by t h e bitallocation schemes of Table 1. T h e associa ted video Peak Signal-to-Noise Ratio (PSNR) was around 30 dB, while t h e subjective quality can b e viewed under http: //www-mobile . ecs . sbton. ac .uk. A range of multimode wireless transceivers were also proposed, which a r e characterised by Table 2.