Quadtree-based Re-configurable Cordless Videophone System

J. Streit, L. Hanzo

Department of Electronics and Computer Science,
Univerity of Southampton, SO17 1BJ, UK.
Tel: +44 703 593125, Fax: +44 703 593045
Email: lh@ecs.soton.ac.uk

© 1996 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to refuse any copyrighted component of this work in other works must be obtained from the IEEE.

IEEE Tr. on Circuits and Systems for Video Technology, Apr. 1996, Vol. 6, No. 2, pp 225-237


Arbitrarily programmable, but fixed-rate quad-tree (QT) decomposed, parametrically enhanced videophone codecs using quarter common intermediate format (QCIF) video sequences are proposed as a direct replacement for mobile radio voice codecs in second generation systems, such as the Pan-European GSM, the American IS-54 and IS-95 as well as the Japanese systems. The corresponding bitrates are 13, 8, 9.6 and 6.7 kbps, respectively. As an example, the proposed 11.36 kbps prototype Codec 1 and the 11 kbps Codec 2 are embedded in the adaptively re-configurable wireless videophone Systems 1-4 featured in Table~\ref{features1} and their video quality, bit rate, robustness and complexity issues are investigated. Coherent re-configurable 16 or 4-level pilot symbol assisted quadrature amplitude modulation (PSAQAM) is used and the system's robustness is improved by a combination of diversity and Automatic Repeat Request (ARQ) techniques. When using a bandwidth of 200 kHz, as in the Pan-European GSM mobile radio system, the number of videophone users supported varies between 3 and 16, while the minimum required channel Signal to Noise Ratio over Gaussian and Rayleigh channels is in excess of 6 and 8 dB, respectively, assuming a noise-limited, rather than interference-limited scenario. The salient system features are summarised in Table 1.

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