A new vector quantization scheme in discrete cosine transform domain, named DCT-VQ and its application to color image coding are described. In this scheme, DCT-domain is partitioned into vectors which are normalized and vector-quantized using universal vector quantizers designed with multidimensional Laplacian distribution. Adaptive coding scheme is also introduced to obtain better reconstruction of images. The color image coder employs the above scheme and encodes separately three components converted from R,G,B signals. The simulations have shown that adaptive DCT-VQ exhibits better performance than a conventional adaptive cosine transform coding with scalar quantization. The decomposition of DCT-block into vectors results in much less complex coder than a vector quantizer in original space domain.

A new nonlinear digital filter which separates nonstationary waves such as spikes from stationary background waves of the EEG is proposed. This filter is composed of a prediction filter and a simple nonlinear function, and separates the nonstationary waves by processing the prediction error with the nonlinear function. This filter aims at real-time analysis of EEG, hence the algorithm of this filter is deliberately kept very simple, and the parameters in it are set adaptively. Some examples of separating spikes from epileptic EEG data are shown.

This paper describes a knowledge based isolated Japanese word recognition algorithm. The program is written with Prolog/KR [4] and has two basic inference processes, i.e., a Bottom-up search and a Top-down search. In the Bottom-up process, a segmentation and a vowel decision are performed and some target word patterns are generated. The Top-down process includes a consonant decision using a score of each candidate word calculated based on the Fuzzy Set Theory [1]. In the vowel inference, a template matching is applied mainly. In the segmentation, heuristic rules based on the spectrum transition and the wave form are used. But in the consonant inference, each rule has a hierarchy structure and it is defined automatically in the form of the multi-valued threshold function from learning data. This system can treat an obscure information about the consonant classification and to select the most effective decision rule in order to simplify the understanding process. The truth rate of consonant recognition is better than using statistical method.

An efficient discrete cosine transform image coding system using the gain/shape vector quantizers (DCT-G/S VQ) is presented. In the coding system, AC transform coefficients in a subblock are partitoned into several bands according to the Schaming's method, and the normalized AC transform coefficients of each band are quantized with the gain/shape vector quantizer designed on a spherically symmetric probability model. In addition, an adaptive DCT-G/S VQ (A-DCT-G/S VQ) is presented by incorporating a modification of the recursive quantization technique in the DCT-G/S VQ. The coding systems are simulated on color images, and their performance is compared to that of previously reported discrete cosine transform coding systems using the Max-type scalor quantizers.

A new transmission scheme for channels with intersymbol interference named "matched-transmission (MT) technique" is proposed. An implementation of the MT system is presented and its relations with conventional techniques are described. It is shown that the partial response scheme is a special case of our new technique. The performance of the MT technique is discussed from the view point of the output signal-to-noise ratio and the system is shown to attain asymptotically the bound performance predicted by the information theory.

This paper reviews recent progress in communication theory in Japan, mainly in the past three years. The topics to be discussed include 1) waveform transmission in band-limited channels and active transmission lines, 2) source-coding problems such as optimal quantizing characteristics, delta modulation, and linear transformation, 3) transmission codes, where mainly multilevel codes have been discussed, 4) new information transmission and modulation schemes, and 5) theories of traffic and switchingsystem design.

In this paper, two-dimensional arrays of elements of an arbitrary finite field are examined, especially arrays having maximum-area matrices. We first define two-dimensional linear recurring arrays. In order to study the characteristics of two-dimensional linear recurring arrays, we also define two-dimensional linear cyclic codes. A systematic method of constructing two-dimensional linear recurring arrays having maximum-area matrices is given using the theory of two-dimensional cyclic codes. These arrays, here called\gamma \beta-arrays, may be said to be two-dimensional analogs ofM-sequences. A\gamma \beta-array of areaN_x \times N_yexists overGF(q)if and only ifN_x N_yis equal toq^N _ 1for some positive integerN. Many interesting characteristics of the\gamma \beta-array, such as the properties of its autocorrelation function and the properties of the characteristic arrays, are deduced and explained.

A class of binary sequences whose elements are either1or-1and whose autocorrelation function is0for all even shifts except the zero shift is discussed. These sequences will be calledEsequences. It is proved that everyEsequence is paired with anotherEsequence, its mate, so that the cross-correlation function between them is0for all even shifts including the zero shift. Using these sequences, new complete orthogonal function sets are derived. Several other important properties of these sequences are also obtained and the relations among these sequences, Golay's complementary sequences and Welti's quaternary codes are discussed.