An experimental latch circuit is fabricated by using a 0.35µm MT-CMOS technology. This latch circuit has a volume smaller by 30%, a delay time shorter by 10%, and has an active power consumption smaller by 10% over those of a conventional MT-CMOS circuit. Furthermore, at a operation frequency of 100 MHz, an SRAM employing this IPS scheme has a standby current which is 0.4% of SRAM's without using IPS scheme.

We consider the situation that plural degraded images are obtained. When no prior knowledge about original images are known, these images are individually restored by an optimum restoration filter, for example, by Wiener Filter or by Projection Filter. If correlations between original images are obtained, some restoration filters based on Wiener Filter or Projection Filter are proposed. In this paper, we deal with the case that some pixels or some parts of original images overlap, and propose a restoration method using a formulae for overlapping. The method is based on Partial Projection Filter. Moreover, we confirm an efficacy of the proposed method by numerical examples.

Pre-decorrelation is a method of achieving orthogonalization between multiple signals on the forward link. This technique can achieve orthogonalization in a flat fading channel, however, the orthogonality does not clearly appear in a multipath fading channel because of interchip interference. In order to eliminate the effect of multipath and prevent interchip interference, multicarrier modulation can be employed. In this paper we propose a multicarrier pre-decorrelation technique which combines multicarrier modulation with pre-decorrelation. Computer simulation results show that the proposed technique can achieve orthogonalization in a multipath fading channel.

This paper is concerned with CDMA applied to personal and mobile communications on a global basis using multiple low earth orbital satellites (LEOS). We focus our attention on some unique aspects of LEOS systems and discuss their influences on the CDMA system performance as well as the techniques for coping with these aspects. We deal with three kinds of important items that are unique to LEOS systems; Doppler frequency shift due to satellite movement, propagation delay affecting packetized data transmission and geographical nonunifomity in traffic.

This paper presents a method to examine the effect of introducing data application services on existing wireless CDMA networks where conventional voice communications service is being provided. Since the total number of channels used in a cell is limited in the interfering cellular environments, some voice-traffic channels should be sacrificed when an additional channel is introduced for data services. We investigate this trade-off by analyzing the interference the forward link channels generate. It is also an objective of this paper to examine the forward link capacity in terms of the numbers of paging and voice-/data-traffic channels so as to determine the impact of introducing data services via paging and traffic channels. Different capacity regions are plotted for various cellular environments.

It is well known that M-ary/spread spectrum (M-ary/SS) system is superior to direct-sequence spread spectrum system under AWGN, and can achieve high spectral efficiency. On the other hand, however, the main drawback of this system is that the synchronization acquisition is difficult. In this paper, we propose a new synchronization acquisition method of M-ary/SS system. This method acquires the code synchronization by introducing a symmetrical property in spreading sequences, and detecting this property with the differential decoding technique. As spreading sequences, a set of orthogonal sequences and a set of non-orthogonal sequences are considered. The strong features of proposed systems are that the systems can acquire the code synchronization in carrier band and can reduce the complexity of calculation greatly. Among the comparison results of the systems with newly proposed orthogonal and some specific non-orthogonal spreading sequences, it is especially noted that the latter can reduce the mean acquisition time and calculation complexity much greater than the former.

This paper proposes an analysis method of scaling-factor-quantization error in fractal image coding using a state-space approach with the statistical analysis method. It is shown that the statistical analysis method is appropriate and leads to a simple result, whereas the deterministic analysis method is not appropriate and leads to a complex result for the analysis of fractal image coding. We derive the output error variance matrix for the measure of error and define the output error variance by scalar quantity as the mean of diagonal elements of the output error variance matrix. Examples are given to show that the scaling-factor-quantization error due to iterative computation with finite-wordlength scaling factors degrades the quality of decoded images. A quantitative comparison of experimental scaling-factor-quantization error with analytical result is made for the output error variance. The result shows that our analysis method is valid for the fractal image coding.

We propose concepts of Paley-Wiener multiresolution analysis and Paley-Wiener wavelet frame based on general, not limited to dyadic, dilations of functions. Such a wavelet frame is an extension both of the Shannon wavelet basis and the Journe-Meyer wavelet basis. A concept of "natural" Paley-Wiener wavelet frame is also proposed to clarify whether a Paley-Wiener wavelet frame can naturally express functions from the point of view of the multiresolution analysis. A method of constructing a natural Paley-Wiener wavelet frame is given. By using this method, illustrative examples of Paley-Wiener wavelet frames with general scales are provided. Finally, we show that functions can be more efficiently expressed by using a Paley-Wiener wavelet frame with general scales.

The efficiency and reliability of an ultrasonic motor, operating in longitudinal-torsional degenerate-mode, are investigated. It is essential to miniaturize both longitudinal and torsional mode piezoelectric ceramic elements, in order to produce low-cost ultrasonic motors, and to realize a motor with low battery power consumption. The ultrasonic motor is designed with an accurate mechanical equivalent circuit, which can produce high design precision notwithstanding low computation cost. It is important in this design that the resonant frequencies of longitudinal mode and torsional mode coincide with each other under the pertinent rotor pressing force and longitudinal and torsional mode piezoelectric ceramic elements are located in the vibration nodes for the longitudinal mode and the torsional mode, respectively. As a result, the fabricated motor, whose rotor diameter was 12 mm, produced 480 r.p.m. no-load revolution speed, 0.55 kgfcm maximum torque, 50% maximum efficiency, 2.5 W consumed power and a lifetime over 1000 hours with continuous rotation.

This letter proposes and investigates a method of estimating the direction of arrival (DOA) of wideband signals such as spread spectrum signals, in a multipath channel. The DOA estimation method can reduce the effect of signal distortion due to bandwidth of signals by creating a spatial spectrum wihch satisfies the sampling theory in the time domain. The DOA estimate calculated from this spatial spectrum is robust against signal distortion due to multipath. Computer simulations numerically evaluate the proposed method. In comparison with conventional MUSIC algorithm, the proposed method achieves superior performance in a multipath channel.

Considering that the application of the direct-sequence slotted spread ALOHA communications system to access/control channel is effective in communications systems with traffic channels operating at CDMA mode, the spread ALOHA communications system is discussed in terms of the system configuration and transmission efficiency. The transmission efficiency of the spread ALOHA communications system using a unified spread code is derived by means of two methods. One is based on the simulation of demodulation algorithm, and the other is based on the approximation by modeling. It becomes obvious from quantitative evaluation in terms of the probability of packet success and the throughput performance that the approximated results coincide with the simulated results, and that the modeling is very effective to estimate the transmission efficiency of the spread ALOHA communications system.

In this paper, we discuss the use of convolutional codes with a multi-antenna transmission scheme for DS/CDMA systems. The binary input data to a rate 1/M encoder produces M coded bits, which, in turn, are assigned to M different antennas and transmitted from each antenna simultaneously. An intentional delay of several chips duration is introduced at each antenna before transmission, which enables a receiver to distinguish the signals from different antennas. Because the proposed scheme utilizes spatial and time domains for coding, it can achieve not only implicit time-diversity through the use of coding with interleaving, but also space-diversity through the transmission from multiple antennas. Multi-antenna schemes with convolutional codes can perform better than conventional single antenna schemes with the same codes and transmission diversity technique with the same number of transmitting antennas, especially when a fading is relatively slow and interleaving size is limited.

In this paper, we present orthogonal multi-code CDMA systems with the constant amplitude transmission. In general, the dynamic range of the amplitude of the transmitting signal is very large in the case of orthogonal multi-code CDMA systems. In order to realize the constant amplitude transmission for orthogonal multi-code CDMA systems, we propose a constant amplitude coding. First, we show the basic concept of the constant amplitude coding. And then, we show that the constant amplitude transmission can be realized by the combination of the conventional orthogonal multi-code CDMA and the constant amplitude coding. Finally, the effectiveness of the proposed method is evaluated in terms of the bit error rate performance and it is shown that the proposed method is robust to the non-linear distortion caused by a high power amplifier (HPA).

This paper extends left-incompatible term rewriting systems defined by Toyama et al. It is also shown that the functional strategy is normalizing in the class, where the functional strategy is the reduction strategy that finds index by some rule selection method and top-down and left-to-right lazy pattern matching method.

This paper presents a proportional-share CPU scheduler which can support multimedia applications in a general-purpose workstation environment. For this purpose, we have extended the stride scheduler which is designed originally for conventional tasks. New scheduling parameters are introduced to specify timing requirements of multimedia applications. Through the use of the rate regulator, the accuracy error of the scheduling is reduced to 0 (1). Separate task groups are proposed to represent both relative shares and absolute shares. The proposed scheduler is evaluated using a simulation study. The results show that the proposed scheduler achieves improved accuracy and adaptability as well as flexibility.

A processor allocation scheme for mesh computers greatly affects their system utilization. The performance of an allocation scheme is largely dependent on its ability to detect available submeshes. We propose a new type of submesh, called a link-disjoint submesh, for processor allocation in mesh computers. This type of submesh increases the submesh recognition capability of an allocation scheme. A link-disjoint submesh is not a contiguous submesh as in the previous scheme, but this submesh still has no common communication link with any other submesh. When wormhole routing or circuit switching is used, the communication delay caused by non-contiguous processor allocation is minor. Through simulation, the performance of our scheme is measured and compared to the previous schemes in terms of such parameters as finish time and system utilization. It is shown through simulation that the link-disjoint submesh increases the performance of an allocation scheme.

This paper propeses advanced multi-stage interference canceller systems (MSICS) wihch can estimate radio channels with precision in the direct sequence code division multiple access (DS-CDMA) systems. For the accurate channel estimations, we propose a novel radio channel estimation method specified by the following two signal processing methods. One is the radio channel estimation using both pilot and information signals. The other is the correction of estimated radio channels using adaptation algorithm based on the least mean square method (LMS). The results of our computer simulation indicate that the cell capacity of the advanced MSICS in serial and parallel structure can be increased by about 1.8 and 1.3 times over that of a receiver which does not has a canceller, respectively. Moreover, the advanced MSICS in serial and parallel structure can reduce the required Eb/No by about 1.2 dB and 1.6 dB at a BER of 10-3 compared to the Eb/No of a basic MSICS, respectively.

In this paper, a simple frame synchronization method for the SS-CSC syytem is proposed, and the synchronization performance is analyzed. There have been growing interests in the M-ary/SS communication system and the bi-orthogonal modulation system because these systems can achieve the high frequency utilization efficiency. However, the frame synchronization is difficult. We proposed the SS-CSC system, and evaluated the bit error rate (BER) performance of the SS-CSC system under the completed synchronization. The BER performance of the SS-CSC system is much the same as that of the bi-orthogonal modulation system. In this paper, a frame synchronization method using the differential detector and racing counters is proposed. In particular, the lose lock time, the recovery time and the BER performance considering the synchronizing performance are analyzed. In consequence, the BER performance considering the synchronization performance can approach the lower bound of the SS-CSC system by tuning the number of the stages in racing counters.

This paper proposes high-speed similitude retrieval schemes for a viewpoint-based similarity discrimination system (VB-SDS) and presents analytical and experimental performance evaluations. The VB-SDS, which contains a huge set of semantic definitions of commonly used words and computes semantic similarity between any two words under a certain viewpoint, promises to be a very important module in analogical and case-based reasoning systems that provide solutions under uncertainty. By computing and comparing similarities for all words contained in the system, the most similar word for a given word can be retrieved under a given viewpoint. However, the time this consumes makes the VB-SDS unsuitable for inference systems. The proposed schemes reduce search space based on the upper bound of a similarity calculation function to increase retrieval speed. An analytical evaluation shows the schemes can achieve a thousand-fold speedup and confirmed through experimental results for a VB-SDS containing about 40,000 words.

Fast and low-power circuit techniques suitable for size-configurable SRAM macrocells are described. An SRAM cell architecture using virtual-GND lines along bitlines is proposed; each virtual-GND line switches the potential by inner read-enable and column-address-decoded signals. Reducing the active power dissipation in the memory array and shortening the time for writing data are simultaneously accomplished. The range of available supply voltages is enhanced by adoptive higher virtual-GND level control with a simple voltage limiter. An SRAM-macrocell test chip is designed and fabricated with 0.5-µm CMOS technology. A 4K-word6-bit organization SRAM demonstrates 186-MHz operation at a 3.3-V typical power supply. Its power dissipation at a practical operating frequency, 100-MHz, is reduced to 29% (25-mW) by the proposed virtual-GND line techniques.