The transmission of 8-bit µ-law PCM signals using 16-level weighted QAM over Gaussian channels is examined. The weighting process modifies the positions of the QAM constellation points so that the overall distortion in the recovered information-bearing source signal is reduced. The PCM bits are mapped to the weighted QAM points such that the most significant bits have a lower probability of being in error than the least significant bits. The weighted QAM systems have been optimized for the same energy signal energy per transmitted symbol as for unweighted QAM. Also, the erasure zone is established at the detector, such that if the output falls into the erasure zone, the regenerated sample is replaced by interpolation. The theoretical results indicates that 16-level weighted QAM have a gain of 5dB over unweighted QAM.

Based on the Fornasini-Marchesini second local state-space (LSS) model, the coefficient sensitivities of two-dimensional (2-D) digital filters are analyzed in conjunction with frequency weighting functions. The overall sensitivity called the frequency-weighting sensitivity is then evaluated using the 2-D generalized Gramians that are newly introduced for the Fornasini-Marchesini second LSS model. Next, the 2-D filter structures that minimize the frequency-weighting sensitivity are synthesized for two cases of no constraint and scaling constraints on the state variables. Finally, an example is given to illustrate the utility of the proposed technique.

This study proposes a new training method for hidden Markov model with separate vector quantization (SVQ-HMM) in speech recognition. The proposed method uses the correlation of two different kinds of features: cepstrum and delta-cepstrum. The correlation is used to decrease the number of reestimation for two features thus the total computation time for training models decreases. The proposed method is applied to Japanese language isolated dgit recognition.

This letter discusses the quality improvement of reconstructed images in diffraction tomography. An efficient iterative procedure based on the modified Newton-Kantorovich method and the Gerchberg-Papoulis algorithm is presented. The simulated results demonstrate the property of high-quality reconstruction even for cases where the first-order Born approximation fails.

Based on the Fornasini-Marchesini second model, an efficient algorithm is developed to derive the characteristic polynomial and the inverse of the system matrix from the state-space parameters. As a result, the external description of the Fornasini-Marchesini second model is clarified. A technique for designing 2-D recursive digital filters in the frequency domain is then presented by using the Fornasini-Marchesini second model. The resulting filter approximates both magnitude and group delay specifications and its stability is always guaranteed. Finally, three design examples are given to illustrate the utility of the proposed technique.

This paper discusses the bit-rate compression of super high definition still images with subband coding. Super high definition (SHD) images with more than 20482048 pixels or resolution are introduced as the next generation imaging system beyond HDTV. In order to develop bit-rate reduction algorithms, an image evaluation system for super high definition images is assembled. Signal characteristics are evaluated and the optimum subband analysis/synthesis system for the SHD images is clarified. A scalar quantization combined with run-length and Huffman coding is introduced as a conventional subband coding algorithm, and its coding performance is evaluated for SHD images. Finally, new coding algorithms based on block Huffman coding and entropy coded vector quantization are proposed. SNR improvement of 0.5 dB and 1.0 dB can be achieved with the proposed block Huffman coding and the vector quantization algorithm, respectively.

In this paper, we present an automatic implementation method by which executable communication programs in C can be generated from protocol specifications in LOTOS. The implementation method consists of two parts: 1) An implementation strategy and 2) a set of translation rules. The first part consists of the basic ideas on how to realize the primary mechanisms in LOTOS specifications. The second part formulates the implementation method by way of the translation rules based on the implementation strategy. The characteristics of our method can be summarized as follows: We formulate our implementation method by way of translation rules. These rules are defined topdown in the form of syntax-directed translation function. The mechanism for controlling concurrency and communication among the user processes corresponding to the processes in LOTOS specification is easily realized by using UNIX operating system functions. The translation rules have been implemented on the AS 3000 (SUN3) workstation. An application of this implementation method is demonstrated by a simplified token-ring-protocol.

A novel coding scheme using orthonormal wavelet transform is proposed. Various forms of transform coding and subband coding are first reviewed. Then a wavelet coding method is proposed adopting a new approach similar to the one used for transform coding. The approach differs to conventional ones which considers wavelet coding as a class of subband coding. Simulation work is carried out to evaluate the proposed coding method. Significant improvement is obtained in subjective quality, and some improvement is also obtained in signal to noise ratio. Wavelet coding is still in its early stage of development, but can be considered to be a promising technique for image coding.

One of the problems with subband image coding is the increase in image sizes caused by filtering. To solve this, it has been proposed to process the filtering by transforming input sequence into a periodic one. Then filtering is implemented by circular convolution. Although this technique solves the problem, there are very strong restrictions, i.e., limitation on the filter type and on the filter bank structure. In this paper, development of this technique is presented. Consequently, any type of linear phase FIR filter and any structure of filter bank can be used.

We consider the role of equivalence queries in learning unknown concepts using membership and equivalence queries. Equivalence queries have the following two roles: (R1) indicating whether a learning algorithm has succeeded to learn the unknown concept and (R2) providing counterexamples. In this paper, we consider the learning using membership and equivalence queries but using only the (R2) part of equivalence queries. In order to gain an insight into the learning membership and equivalence queries but using only the (R2) part of equivalence queries, we define equivalence-detecting problem". Let C be a representation class which is polynomial time learnable using membership and equivalence queries. We show that if the equivalence-detecting problem for C is polynomial time solvable then C is polynomial time learnable using membership and equivalence queries without using (R1). Moreover, we show that under certain conditions, the two notions, polynomial time solvability of equivalence-detecting problem" and polynomial time learnability using membership and equivalence queries without using (R1)", are equivalent. For concrete examples, we prove that dfas are polynomial time learnable using membership and equivalence queries without using (R1) in the learning situation where the algorithm is informed the number of states of the minimum states dfa accepting the target set in advance. On the other hand, we show that the equivalence-detecting problem for dfas are not solvable in the learning situation where the algorithm can use no additional information. This result together with our main result shows that, in this learning situation, the (R1) part of equivalence queries are necessary to learn dfas using membership and equivalence queries.

Bifurcations of the periodic solutions of the space-clamped Hodgkin-Huxley equations for the muscle membrane are studied regarding the chloride conductance as a parameter. A limit cycle appears at a Hopf bifurcation and disappears at a homoclinic orbit. With high sodium permeability, a subcritical period doubling bifurcation occurs before it disappears.

Optimal static load balancing problems in open BCMP queueing networks with state-independent arrival and service rates are studied. Their examples include optimal static load balancing in distributed computer systems and static routing in communication networks. We refer to the load balancing policy of minimizing the overall mean response (or sojourn) time of a job as the overall optimal policy. We show the conditions that the solutions of the overall optimal policy satisfy and show that the policy uniquely determines the utilization of each service center, the mean delay for each class and each path class, etc., although the solution, the utilization for each class, the mean delay for all classes at each service center, etc., may not be unique. Then we give tha linear relations that characterize the set whose elements are the optimal solutions, and discuss the condition wherein the overall optimal policy has a unique solution. In parametric analysis and numerical calculation of optimal values of performance variables we must ensure whether they can be uniquely determined.

This paper discusses and evaluates, from the viewpoints of definition, analysis, and performance, frequency assignment schemes that enable the efficient assignment of multiple-bandwidth carriers on the transponder in SCPC/FDMA systems with demand assignment operation. The system considered handles carriers of two different bandwidths, and assigns only consecutive slots on the transponder band to broadband carriers. Three types of frequency assignment schemes are proposed, each of which incorporates one or both of two assignment concepts: (1) pre-establishment of assignment priorities on the transponder band, and (2) establishment of broadband slots to guide broadband carrier assignment. Following a definition of the schemes, equations are derived to theoretically analyze performance factors such as call loss for the narrowband and broadband carriers, and system utilization efficiency. Finally, theoretical performance calculated for various traffic and system conditions are presented and evaluated, for the purpose of comparison between the three schemes. Computer simulation results are also presented, to demonstrate the accuracy of the derived equations and to supply data for models too large for theoretical computation. Main results obtained are as follows. (1) Regardless of traffic or system conditions, the assignment scheme incorporating both assignment priorities and broadband slots shows the best performance in terms of broadband call loss and system utilization efficiency. (2) The establishment of broadband slots improves performance when the ratio of broadband traffic to the total traffic volume is high, but worsens performance when the narrowband traffic ratio is higher. (3) All aspects of performance improve with the increase of the total number of assignable slots on the transponder band.

The selection method of the moment of inertia of the flywheel in a digital measurement system of torque-speed curve plotting for a kind of motor is presented. The selection standards of the moment of inertia and the map displaying the operating ranges of the measurement system are shown. The selection procedure of the moment of inertia is also shown.

General estimation technique using covariance information is proposed for white Gaussian and white Gaussian plus coloured observation noises in linear stationary stochastic systems. Namely, autocovariance data of signal and coloured noise appear in a semi-degenerate kernel, which represents functional expression of the autocovariance data, in the current technique. Then the signal is estimated by directly using autocovariance data of signal and coloured noise. On the other hand, in the previous technique, the covariance information is expressed in the form of a semi-degenerate kernel, but its elements do not include any autocovariance data.

We introduce new computer algorithm of multiple alignment as an application of "Simulated Annealing" method. Simulated Annealing has been applied to some combinational optimization problems such as travelling salesman problem. After giving short mathematical explanation of this method, we construct genetic distance and matrix corresponding to the object function in the annealing theory for the multiple alignment. Our method is better than other alignment in the sense that we obtain a result having a smaller value for the genetic distance. We discuss further development along on new method.

Quadrature Amplitude Modulation (QAM) schemes are attractive in terms of bandwidth efficiency and offer a number of subchannels with different integrities via both Gaussian and Rayleigh-fading channels. Specifically, the 16-QAM phasor constellation has two, while the 64-QAM possesses three such subchannels, which become dramatically different via Rayleigh-fading channels. The analytically derived bit error rate (BER) formulae yield virtually identical curves with simulation results, exhibiting adequate BERs for the highest integrity subchannels of both 16-QAM and 64-QAM to be further reduced by forward error correction coding (FEC). However, the BERs of the lower integrity subchannels require fading compensation to reduce their values for FEC techniques to become effective. This property creates ground for a variety of carefully matched, embedded mobile transmission schemes of different complexities. The practical implementation of such an embedded scheme is demonstrated by a low-cost, low-complexity and low-consumption 50KBd mobile video telephone scheme offering adequate speech and image quality for channel SNRs in excess of about 20dB via Rayleigh-fading channels.

A study on the limitation of optical communication systems has received much attention. A method to overcome the standard quantum limit is to apply non-standard quantum state, especially squeezed state. However, the advantage of the non-standard quantum state is degraded by the transmission energy loss. To cope with this problem, we have proposed a concept of the received quantum state control (RQSC), but the realization has some difficulties. In this paper, we propose a new system to realize the received quantum state control system, employing injection locked laser (ILL) system. Then we show that our new system can overcome the standard quantum limit.

An extremely accurate and very wide-band quadrature modulator IC fabricated on a single chip using bipolar technology is presented. The characteristics of this quadrature modulator IC are much superior to conventional ones (modulation phase error and deviation from quadrature is about 1/10), and this IC is applicable to high modulation schemes such as 256 QAM. In this circuit, the phase difference between local signals input to each of two balanced modulators is detected by a phase detector, and a variable phase shifter in the local port is controlled automatically by the detected signals. This, along with the use of a wide-band variable phase shifter, enables the phase difference between the local signals input to the balanced modulators to be adaptively controlled to 90 degrees in wide frequency bands. In addition, a design method for the balanced modulators to obtain small modulation phase error is described. Based on this design method, a highly accurate quadrature modulator IC was fabricated, in which two balanced modulators, the phase detector, and the variable phase shifter were integrated on a single chip. Phase deviation from quadrature in the local signals was reduced to less than 0.3 degrees in the wide frequency bands of more tham 60 MHz. The modulation phase error of the balanced modulators wes less than 0.2 degrees at 140 MHz, and less than 2.5 degrees at up to 1.3 GHz.

Noise characteristics of InAlAs/InGaAs HEMT's passivated by SiN are investigated to ascertain their suitability for practical applications in circuit such as MMIC's. A 0.18-µm-gate-length device with 125-µm-gate width and 8-gate fingers showed the lowest minimum noise figure of 0.43 dB at 26 GHz with an associated gain of 8.5 dB of any passivated device ever reported. This value is also comparable to the lowest reported minimum noise figure obtained by bare InAlAs/InGaAs HEMT's in spite of increased parasitic capacitances due to the SiN passivation. Thes excellent noise performance was achieved by employing non-alloyed ohmic contact, a T-shaped gate geometry and a multi-finger gate pattern. To reduce the contact resistance of the non-alloyed ohmic contact, a novel n+-InGaAs/n+-InAlAs cap layer was used resulting in a very low contact resistance of 0.09 Ωmm and a low sheet resistance for all layers of 145 Ω/sq. No increase in these resistances was observed after SiN passivation, and a very low source resistance of 0.16 Ωmm was obtained. An analysis of equivalent circuit parameters revealed that the T-shaped gate and multi-finger gate pattern drastically decrease gate resistance.