QUADTREE-BASED RECONFIGURABLE CORDLESS VIDEOPHONE SYSTEMS

Arbitrarily programmable, but fixed-rate quadtree (QT) decomposed, par ametrically enhanced videophone codecs using quarter common intermedia te format (QCIF) video sequences are proposed as a direct replacement for mobile radio voice codecs in second generation systems, such as th e Pan-European GSM, the American IS-54 and IS-95, as well as the Japan ese systems. The corresponding bit rates are 13, 8, 9.6 and 6.7 kb/s, respectively, As an example, the proposed 11.36 kb/s prototype Codec 1 and the 11 kb/s Codec 2 are embedded in the adaptively reconfigurable wireless videophone Systems 1-4 featured in Table IV and their video quality, bit rate, robustness, and complexity issues are investigated, Coherent reconfigurable 16 or four-level pilot symbol assisted quadra ture amplitude modulation (PSAQAM) is used and the system's robustness is improved by a combination of diversity and automatic repeat reques t (ARQ) techniques, When using a bandwidth of 200 kHz, as in the Pan-E uropean GSM mobile radio system, the number of videophone users suppor ted varies between three and 16, while the minimum required channel si gnal to noise ratio over Gaussian and Rayleigh channels is in excess o f 6 and 8 dB, respectively, assuming a noise-limited, rather than inte rference-limited scenario. The salient system features are summarized in Table IV.