A multicarrier niodulation system called Discrete Multitone (DMT) was recently chosen by the American National Standards Institute ( A N I ) as a working standard for asymmetric digital subscriber line (ADSL) signaling. The DMT system use5 the inverse and forward discrete Fourier transform (DFT) for modulation and demodulation. An alternative to the classic DAlT system is to substitute a discrete wavelet transform in place of the DFT as the modulating transform. This new method is called Discrete Wavelet Multitone (DWMT) signaling. and has been shown to be superior tao the D31T system in certain channel environments. This paper illustrates that the DMT system and the DlYILIT system are both based on the theory of AI-band wavelet filter baaks. In particular. DhIT and D\l'?rlT are linked formall) through a discussion of digital niultirate filter banks and digit a1 transniultiplexers. In addition the advantages of wavelet transform-bawd t ransmultiplesers over DFThased transniult iplesers are discussed.
In this paper, we describe a new compression scheme that aims at improving the fidelity of reconstructed images through the parallel application of both lossless and lossy compression techniques. The purpose of the scheme is to obtain compression ratios higher than those obtained by lossless compression schemes and at the same time produce reconstructed images with better fidelity than those normally obtained with lossy techniques. Our tests so far have shown that the integrated losslessflossy (U) compression scheme consistently improves the fidelity of reconstructed images compared to well-known image compression algorithms. Specifically, the new scheme gives better fidelity (20% to 55% reduction in mean square error) than the DCT algorithm under equal compression ratios.
This work develops iterative algorithms for decoding cascade-coded images by Relative Entropy (RE) minimization. In cascade coding, blocks ofanimage are firsttransform-coded and then theretained coefficients are transmitted by using moment-preserving Block Truncation Coding (BTC). The BTC coding introduces a quantization error in the values of the retained coefficients. Upon reception, the distorted coefficients are used in reconstructing the image by the inverse transform, with the unretained coefficients set equal to zero. The proposed algorithms reconstruct the original image from the distorted coefficients by minimizing the RE of the image, with the coefficients used as constraints. In addition, the error introduced by the BTC coding is used as an additional constraint, since it is known to the receiver by the nature of the BTC coding. The iterative nature of the algorithm pertains to the way the algorithm uses the constraints, i.e. one at a time, with each reconstruction used as a prior for the next RE minimization. This is the first time that RE minimization with errors in the constraints has been used in image decompression even though it is common in spectrum estimation when there are errors in the correlation measurements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.