We consider the transmission of video over wireless direct-sequence code-division multiple access (DS-CDMA) channels. A layered (scalable) video source codec is used. The layers may be time-multiplexed and transmitted over a single CDMA channel or each layer can be transmitted over a different CDMA channel. For the latter case, spreading codes of different length are allowed for each CDMA channel (multirate CDMA). Thus, a different number of chips per bit can be used for the transmission of each scalable layer. For a given fixed energy value per chip and chip rate, the selection of a spreading code length affects the transmitted energy per bit and bit rate for each scalable layer. An MPEG-4 source encoder is used to provide a two-layer signal-to-noise-ratio (SNR) scalable bitstream. Each of the two layers is channel-coded using rate-compatible punctured convolutional (RCPC) codes. Then, the data are interleaved, spread, carrier-modulated and transmitted over the wireless channel. A multipath Rayleigh fading channel model is assumed. At the other end, the signal is collected by an antenna array front. After carrier demodulation, multiple-access-interference (MAI) suppressing despreading is performed using adaptive space-time auxiliary-vector (AV) filters. The choice of the AV space-time receiver is dictated by realistic channel fading rates that limit the data record available for receiver adaptation and redesign. Indeed, short-data-record AV filter estimators have been shown to exhibit superior bit-error-rate performance in comparison with least-mean-squares (LMS), recursive-least-squares (RLS), sample-matrix-inversion (SMI), or ``multistage nested Wiener'' adaptive filter implementations. Our experimental results demonstrate the effectiveness of such a multirate DS-CDMA system for wireless video transmission.

Lisimachos P. Kondi received the Diploma degree in electrical engineering from the Aristotle University of Thessaloniki, Greece, in 1994 and the M.S. and Ph.D. degrees in electrical and computer engineering from Northwestern University, Evanston, IL, USA, in 1996 and 1999, respectively. During the 1999-2000 academic year, he was a post-doctoral research associate at Northwestern University. Since August 2000, he is an Assistant Professor of electrical engineering at the State University of New York at Buffalo, USA. During the summer of 2001, he was a U.S. Navy/ASEE Summer Faculty Fellow at the U.S. Naval Research Laboratory, Washington, DC, USA. His current research interests include image and video processing and compression, wireless communications and wireless video transmission, image restoration and super-resolution, and shape coding.