This paper discusses factorization of bent function type complex Hadamard matrices of order pn with a prime p. It is shown that any bent function type complex Hadamard matrix has symmetrical factorization, which can be expressed by the product of n matrices of order pn with pn+1 non-zero elements, a matrix of order pn with pn non-zero ones, and the n matrices, at most. As its application, a correlator for M-ary spread spectrum communications is successfully given, which can be simply constructed by the same circuits with reduced multiplicators, before and behind.

An integrated slider-suspension system was designed and prototyped. The structure of this system has a full flying air-bearing surface in the leading part with a contamination-resistant feature, and it accommodates a slider with a 5-15 nm head-disk spacing at the trailing part. Performance analysis and simulation were conducted to validate the high performances of the design. Two key issues, the rigid motions (vibrations) and the elastic motions of the slider, were investigated systematically. For the rigid motions, it was found that the natural frequencies of the slider system are dependent on the disk contact stiffness and that the slider vibrations under excitation exhibit various nonlinear resonance. For the elastic motions, the average elastic response of the slider body under the random interaction of the interface was derived and characterized.

A method of evaluating the gas viscous friction force acting on head/disk interface has been developed. In the past, the effect of the gas viscous friction force has been almost negligible, due to its small value compared with the contact friction force. Recently the gas viscous friction force has tended to increase with the decrease in spacing and the increase in relative speed between the slider and the disk, therefore it is becoming necessary to consider its effect on motor load or slider posture. Few experimental studies of the gas viscous friction force, however, have been performed. In this study, the measurement of the gas viscous friction force has been realized by developing a sensitive friction force sensor. Furthermore a method of evaluating the gas viscous and contact friction forces separately has been also established.

A head-disk spacing tester that includes the effect of lubricant will be necessary if the slider-disk interaction is to be considered. The interaction and interaction induced spacing variation can be quantitatively characterized by optical method and by replacing the functional disk media with a glass disk covered with a carbon layer and a lubricant layer of the same materials and the same layer thickness as the functional disk media. This paper reports a tester configuration based on that concept. Experimental investigations into the nanometer spaced head-disk interface with such a setup are presented also. Results indicate that the lubricant plays an important role in slider-disk interaction and the vibration of the slider-disk interface. Two types of interface vibration were noticed: contact vibration and bouncing vibration. For the bouncing case, the natural frequency of air-bearing and its fold frequencies will be excited and air-bearing plays more important role in the determination of the slider vibration, comparing with the contact-vibration case.

Recent attractive high-speed networks require network file servers with high-speed read performance to deliver huge multimedia files, like voice or movie files. This paper proposes new design and implementation techniques that yield high-speed file servers based on UNIX. The techniques are request reduction, in which contiguous blocks on UNIX file system (UFS) are gathered for reducing the number of command requests from the file system to the device driver, and a direct access method for cutting through the buffer cache mechanism. A file server prototype based on a general-purpose personal computer (PC) is constructed and its performance is evaluated. The preliminary results show that the prototype achieves high-speed file read performance in excess of 100 Mbytes/s even on an OpenBSD PC-UNIX system with 3 RAID controllers and 9 hard drives in RAID level 0 configuration.

This paper proposes a coherent detection scheme that can reduce the estimation errors of the carrier phase due to Gaussian noise in communication systems where pilot symbol assisted modulation is employed to compensate for Rician fading distortion. This paper introduces two functions in addition to conventional fading estimation methods using Wiener interpolation, etc. The first is the weighted average function for reducing the estimation errors of the fading distortion detected by pilot symbols. The second is the moving average function for estimating the phase errors that are residual after being compensated for by the estimated fading distortion. This paper evaluates the bit error rate (BER) performance for the proposed method in both Rician fading channel and additive white Gaussian noise (AWGN) channel by computer simulation. Simulation results verify that the BER performance of the proposed method is superior to that of a conventional method in both Rician fading channel and AWGN channel. Simulation results also confirm that the degradation of the BER performance of the proposed method is only 0.1 dB in AWGN channel and only 0.3 dB in Rician fading channel compared with the theoretical curves even if we reduce the number of computations by simplifying the calculation of interpolation coefficients optimized for Wiener interpolation.

This paper proposes a short delay, error-resilient video transmission scheme for mobile radio channels. Compressed video data are sensitive to channel error. Video coding schemes such as H. 263 use variable length coding so channel error can cause synchronization failure in the decoder and fatally degrade the reconstructed video sequence by triggering intra- and inter-frame error propagation. ARQ prevents all forms of error propagation but significantly increases the transmission delay of the video frame. We propose a new error control scheme to reduces the delay incurred by ARQ; the receiving buffer can transmits the video frame data to the video decoder even if not all ARQ frames containing the video frame are received. The encoder transmits additional information, the Macro Block (MB) size, in the video frame header. Upon receiving this information, the receiving buffer can determine MB length which allows MB de-synchronization to be prevented. For example, if an ARQ frame is lost, the decoder determines the position of the missing MB and replace this MB with the equivalent block in the previous video frame; this prevents intra-frame error propagation. When all ARQ frames are received and decoded correctly, the video frame in the reference video memory is replaced with the correctly decoded one. Simulation results show that the proposed scheme can minimize the delay and the reduction in frame rate caused by retransmission control without intra- and inter-error propagation.

This paper proposes a novel DS/CDMA system with code-diversity techniques constituted by a simple system to suppress multiple access interference (MAI) without estimating the PN sequence of interference at the receiver. In the transmitter, the data signal is modulated with a sum of several PN sequences, and, two types of code- diversity reception are proposed, (1) maximal-ratio combining (MRC) code-diversity by autocorrelation, and (2) MRC code-diversity by anti-crosscorrelation. By computer simulations, it is shown that MRC code-diversity by anti-crosscorrelation is superior to the other one. It is also shown that MRC code-diversity by anti-crosscorrelation can improve BER more effectively for the interference which takes the phase to degrade BER at the worst. Next, to design the optimum number of branches for code-diversity, average BERs are calculated for several combinations of codes in code-diversity. As a result, the optimum number of branches varies for each combination of codes, however, it is decided from 3 to 7 branches. Finally, the effectivity of the proposed system in a near-far problem is presented.

To improve frequency efficiency or user capacity in multi-path fading environments, we introduce and investigate an orthogonal multi-carrier frequency hopping-code division multiple access (FH-CDMA). These improvements are achieved by combining the orthogonal frequency division multiplexing (OFDM) and FH-CDMA schemes. The basic idea has been previously proposed by the authors. The aim of study in this paper is to evaluate the performance of this scheme in various environments. The theoretical analysis of bit error rate (BER) performance in this paper includes the effects of frequency selective fading in land mobile communications and of nonlinear amplification in satellite communications. A modified scheme of controlling transmission power to be controlled according to the number of simultaneously accessing users is also discussed. This modified scheme improves BER performance for frequency selective fading when the number of simultaneously accessing users in a cellular zone is small. Furthermore, an error-correcting code and its erasure decoding are applied in order to reduce errors due to hits in asynchronous FH/CDMA for reverse link as well as errors due to fading and noise.

In this paper, a type of multi-carrier direct sequence code division multiple access (MC-DS-CDMA) system which uses frequency spread coding is proposed and investigated for the down-link. An MC-DS-CDMA system is a combined system of CDMA and multi-carrier modulation. This system is often categorized as a "serial to parallel (S/P) type" system because serial to parallel converted data symbols are transmitted. They use different sub-carriers which are narrow-band DS waveforms. In this system, benefits of path or frequency diversity can not be obtained because of the narrow-band transmission of each data symbol. In order to benefit from the diversity, we propose to adopt frequency spread coding in an MC-DS-CDMA system. The proposed system exploits frequency diversity without additional redundancy, i. e. , no frequency or time redundancy is required to improve the performance. Computer simulation is carried out in a frequency selective fading channel and the results show its effectiveness in terms of average bit error rate (BER). Furthermore, the proposed system is compared with a multi-carrier (MC-) CDMA system which is often categorized as a "copy type" system and a single-carrier (SC-) DS-CDMA system using a RAKE receiver.

We propose a model for fault tolerant 3D processor arrays using one-and-half track switches. Spare processors are laid on the two opposite surfaces of the 3D array. The fault compensation process is performed by shifting processors on a continuous straight line (called compensation path) from a faulty processor to a spare on the surfaces. It is not allowed that compensantion paths are in the near-miss relation each other. Then, switches with only 4 states are needed to preserve the 3D mesh topology after compensating for faults. We give an algorithm in a convenient form for reconfiguring by hardware the 3D mesh arrays with faults. The algorithm can reconfigure the 3D mesh arrays in polynomial time. By computer simulation, we show the survival rates and the reliabilities of arrays which express the efficiencies of reconfiguration according to the algorithm. The reliabilities are compared with those of the model using double tracks for which the near-miss relation among compensation paths is allowed, but whose hardware overhead is almost double of that of the proposed model using one-and-half track. Finally, we design a logical circuit for hardware realization of the algorithm. Using the circuit, we can construct such a built-in self-reconfigurable 3D mesh array that the reconfiguration is done very quickly without an aid of a host computer.

A. Chatterjee et al. proposed tests with linearity property for gate delay faults to determine, at a required clock speed, whether a circuit under test is a marginal chip or not. The latest transition time at the primary output is changed linearly with the size of the gate delay fault when the proposed test is applied to the circuit under test. To authors' knowledge, no reports on an algorithmic method for generating tests with linearity property have been presented before. In this paper, we propose a method for generating tests with linearity property for gate delay faults. The proposed method introduces a new extended timed calculus to calculate the size of a given gate delay fault that can be propagated to the primary output. The method has been applied to ISCAS benchmark circuits under the unit delay model.

In this paper, an effective method of system modeling and dynamic scheduling to improve operation and control for the Back-End process of semiconductor manufacturing is developed by using Colored Timed Petri-Nets (CTPNs). The simulator of a CTPNs model was utilized to generate a new heuristic scheduling method with genetic algorithm(GA) which enables us to obtain the optimal values of the weighted delay time and standard deviation of lead time.

For backup of failed VPs (Virtual Paths) in ATM (Asynchronous Transfer Mode) networks, many self-healing algorithms have already been proposed. However, since the existing algorithms recover each failed VP with a single backup VP, a problem arises in that those algorithms cannot necessarily provide a failed VP having a higher recovery priority with a larger recovery ratio, which is the ratio of the bandwidth of a backup VP to that of a failed VP. For a solution to the problem, this paper proposes a new self-healing algorithm which recovers each failed VP with one or more backup VPs. We also evaluate its availability by comparing with an existing algorithm through simulations.

In this paper, a method of Transmission Power Control (TPC) for Orthogonal Frequency Division Multiplexing Direct Sequence Code Division Multiple Access (OFDM-DS-CDMA), in order to compensate for power attenuation at each subcarrier, is proposed. Instead of assigning same power levels for all-subcarriers, different transmission power levels are assigned to different subcarriers, according to the attenuation of the subcarriers. System performance, in terms of Bit Error Rate (BER), has been evaluated by Monte Carlo simulation. The simulation results presented significant improvement, the proposed system performed much better than the system without TPC. It is shown that the Each Carrier TPC performs better than All Carriers TPC, which all carriers are controlled uniformly, hence Each Carrier TPC is more suitable for OFDM-DS-CDMA system.

In this letter, the probability of error performance improvements by rain fade countermeasure techniques is analyzed in a Ka-band geostationary satellite communication system using synchronous CDMA scheme, when power control and macrodiversity are used as rain fade countermeasures. Numerical results show that the composite power control plus macroscopic selection diversity system is better than that of utilizing only one technique as a countermeasure of rain fading.

Simple approximate formulas are obtained for the mutual impedance and admittance by using a product of radiation patterns of antennas. The formulas come from a stationary expression of the reaction integral between two antennas where far-field approximations are employed. The theory deals with antennas in free space as well as under the presence of a wedge. Two applications are given for microstrip antennas with experimental verifications.

Millimeter-wave systems increasingly are entering into commercial systems, both for communication and sensors for traffic or industrial applications. In many cases, circuit technology of the involved front-ends includes monolithic and hybrid integrated circuits and even waveguide components like filters or antenna feeds. In addition to the standard technical and environmental requirements, these front-ends have to be fabricated in large quantities at very low cost. After a short review of the problems and some general interconnect and packaging techniques for mm-wave front-ends, achievements of a research program will be presented at the example of components for a 28 GHz communication front-end. Emphasis is put on a novel feed-through structure using multilayer carrier substrates for mm-wave circuits, some advances in electromagnetic field coupling for interconnects to mm-wave MMICs, and the realization of packages including waveguide components by plastic injection molding and electroplating. Results of filters and a diplexer produced in this way are shown, including pretuning of the filters to compensate the shrinking of the plastic parts during cooling.

RSPICE, a fast timing simulator for large digital MOS circuits, is presented in this paper. A new table-based region-wise linear MOS transistor model and the analytical solution of the generic sub-circuit primitive are applied to calculate the transient response of digital MOS circuits. The body effect of pass transistors is included in the MOS model and the floating capacitor network can be handled by this sub-circuit primitive as well. In RSPICE, MOS transistors with a DC path are grouped into a DC-connected block (DCCB), and DCCBs with a feedback path are combined as a strongly connected component (SCC). RSPICE orders SCCs by Tarjan's algorithm and simulates ordered SCCs one by one. DCCBs are basic cells in RSPICE and any DCCB can be mapped into one or more sub-circuit primitives. In order to calculate the transient response of these primitives analytically, RSPICE approximates the input signals of the primitive by piecewise linear functions. To compromise the simulation accuracy and run time, partial waveform and partial time convergent (PWPTC) combined with dynamic windowing technique is applied to simulate SCCs. Other key issues of RSPICE, such as circuit partition, pass-transistor and floating-capacitor processing, simulation-flow control and waveform modification are also discussed in detail. Compared with HSPICE , the simulation result of RSPICE is very accurate with an error less than 3%, but the speed is 1-2 orders over HSPICE.

Human visual system can perceive 3-D structure of an object by binocular disparity, gradient of illumination (shading), occlusion, textures, perspective and so forth. Among them, binocular disparity seems to be the essentially important cues for the 3-D space perception and it is used widely for displaying 3-D visual circumstances such as in VR (virtual reality) system or 3-D TV. Visual illusions seem to be one of the phenomena which are purely reflecting the mechanism of human visual system. In the recent several years, the authors found several new types of 3-D visual illusions with binocular viewing. Entire 3-D illusory object including volume perception, transparency, dynamic illusions can be perceived only from the visual stimuli of disparity given by some inducing objects arranged with suitable relations. In this report, the authors introduced these newly found visual illusions and made some considerations on the human visual mechanism of 3-D perception and on their exploitation for new effective techniques in 3-D display. They introduced especially on the visual effect in two kinds of arrangement with occlusion and sustaining relationship between the illusory object and inducing objects. In the former case, the inducing objects which provide the stimuli were named as occlusion cues and classified into two types: contour occlusion cues and bulky occlusion cues. In the later case, those inducing objects were named as sustaining cues and a 3-D fully transparent illusory object was perceived. The perception was just like imagined from the scenes of the actions and positions of the pantomimists; then this phenomena was named as "Mime (Pantomime) Effect. " According to the positions of sustaining cues, they played different actions in this perception, and they are classified into three types: front sustaining cues, side sustaining cues and back sustaining cues. In addition, dynamic fusion and separation of volumetrical illusory objects were perceived when the visual stimuli were moving continuously between two structurally different conditions. Then the hysteresis was recognized in geometrical position between the fusion and separation. The authors believe that the occlusion cues and sustaining cues introduced in this paper could be effective clues for exploiting the new techniques for 3-D display.