We propose Direct Sequence CDMA with Optical Multicarriers and Parallel Forward Error Correcting (PFEC) coding technique. Proposed DS-CDMA with OPTICAL MULTICARRIERS, is new in lightwave systems and its alliance with PARALLEL FEC codes, makes it further unique. Optical multicarriers approach is effective to increase throughput by combating dispersion and ISI (Intersymbol Interference), whereas FEC is effective to increase reliability by diluting interactions among optical multicarriers. Till now, both the techniques in lightwave systems have been discouraged. The former because of the wandering effect of optical multicarriers owing to unstability of laser diodes and later because it involves insertion of parity bits that changes data rate and results in insertion distortion that is not desirable in optical systems. To avoid change due to spreading code we also propose to take spreading code equal to serial to parallel converted streams. It bounds initial data (before S/P conversion) to data per carrier (after S/P conversion and spreading) on one hand and relaxes the requirement of high speed electronics on the other. The alliance of optical multicarriers with suitably applied FEC that we refer as Parallel FEC (PFEC) is effective as the beneficial aspects of each mitigate the shortcomings of the other and make the system practicable. Theoretical treatment confirms that the proposed approach is fundamentally sound and holds the potential for promising network performance.

We have applied hot-carrier circuit-level simulation to memory peripheral circuits of a few thousand to over 12K transistors using a simple but accurate degradation model for reliability verification of actual memory products. By applying simulation to entire circuits, it was found that the location of maximum degradation depended greatly upon circuit configuration and device technology. A design curve has been developed to quickly relate device-level DC lifetime to circuit-level performance lifetime. Using these results in conjunction with a methodology that has been developed to predict hot-carrier degradation early in the design cycle before TEG fabrication, accurate total-circuit simulation is applied early in the design process, making reliability simulation a crucial design tool rather than a verification tool as technology advances into the deep sub-micron high clock rate regime.

Process algebras with name passing have been proposed for concurrent mobile processes. They can be suitable to describe dynamical changes of connections among processes. To describe mobile communication or mobile computing systems, however, it is necessary to consider locations at which processes run. We propose a description method to design mobile communication systems using a concurrent calculus in this paper. The concept of a field is introduced to model locality of communication. An extension of π-calculus with a field is proposed. The extension does not include locality represented by a field while most related works treat locality within their languages. A field is given when behavior of a target system is verified in a particular environment. The aim of the extension is to verify and to test connectivity between processes under various geographical constraints. This method could be design-oriented in this context. Equivalence relations with/without location in this calculus are also discussed.

Sr0. 7Bi2. 3Ta2O9(SBT) films are drawing attention as fatigue-free materials. We prepared an SBT film containing discontinuous crystals in the Bi-layered compound using a misted deposition method. In comparison to films prepared by the spin-on method, leakage current was low and spontaneous polarization is high but saturation performance was low. The low saturation performance seems attributable to the inclusion of discontinuous crystals in the Bi-layered compound, while the low leakage current may be explained by the films smaller, denser particles, which form a film without voids, resulting in higher uniformity. The misted deposition method has advantages of finer grain size and higher uniformity.

A maximal-ratio-combining (MRC) digital beamformer has been studied to attain open-loop and automatic self-beam steering towards both desired and multipath signals at the same time and diversity combining of the signals, which are made possible by spatial digital signal processing. This paper describes the performance of this beamformer under the multipath signal arrivals with various path delays using numerical simulation, aimed at application to future mobile radios with high spatial utilization efficiency. The results indicate the robustness of the MRC beamformer in a multipath environment. It features multidirectional beam steering when there is small path delay in the multipath signal and gain suppression in multipath signals when their path delay is more than about one symbol. Moreover, improvement in suppression by employing low-sidelobe amplitude distribution is discussed as a means to reduce inter-symbol interference without null-beam steering.

This paper presents experimental results obtained in indoor broad-band transmission experiments using a QPSK-100 Mbps modem in the 37 GHz band. Transmission performance is measured at many antenna locations in an office. The zone coverage, defined points where as the BER was less than 10-7, was derived in order to evaluate the possibility of high-speed transmission. It was found that adjusting the receiving antenna position a few centimeters greatly improves the zone coverage in utilizing millimeter waves. This result indicates the effectiveness in improving zone coverage of space diversity reception with an antenna spacing of several centimeters. Experimental results obtained show that zone coverage of up to 70% in the measured range is achieved by space diversity reception. Thus, the feasibility of 100 Mbps indoor wireless transmission, conventionally thought to be impossible, is experimentally confirmed.

This paper presents a routing methodology and a routing algorithm used in designing Gb/s LSIs with deep-submicron technology. A routing method for controlling wire width and spacing is adopted for net groups classified according to wire length and maximum-allowable-delay constraints. A high-performance router using this method has been developed and can handle variable wire widths, variable spacing, wire shape control, and low-delay routing. For multi-terminal net routing, a modification of variable-cost maze routing (GVMR) is effective for reducing wire capacitance (net length) and decreasing net delay. The methodology described here has been used to design an ATM-switch LSI using 0. 25-µm CMOS/SIMOX technology. The LSI has a throughput of 40 Gb/s (2. 5 Gbps/pin) and an internal clock frequency of 312 MHz.

Method schemas were proposed as a formal model of object-oriented languages. A method schema S is called consistent if, for each method invocation during the execution of S, a method definition to be bound to the invoked method name is uniquely determined. However, the consistency testing problem is known to be undecidable in general. This paper presents an algorithm which analyzes the consistency of a given method schema. The algorithm decides the consistency problem in polynomial time for monadic method schemas. We also provide an incremental algorithm for testing consistency after updates of a method schema.

FIR digital filters composed of parallel multiple subfilters are proposed. A binary expression of an input signal is decomposed into multiple shorter words, which drive the subfilters having different length. The output error is evaluated by mean squared and maximum spectra. A fast algorithm is also proposed to determine optimal filter lengths and coefficients of subfilters. Many examples confirm that the proposed filters generate smaller output errors than conventional filters under the condition of specified number of multiplications and additions in filter operations. Further, multiplier and adder structures (MAS) to perform the operations of the proposed filters are also presented. The number of gates used in the proposed MAS and its critical path are estimated. The effectiveness of the proposed MAS is confirmed.

This paper describes key technologies for implementing ATM internode signalling. The reliability of a multimedia handling network can be improved by setting multiple virtual paths(VPs)between two nodes and setting signalling links over each internode VP. A software structure appropriate for handling the signalling protocol(MTP3b)within this framework is proposed. We also propose a cost-effective and reliable way to set a signalling route between a node and the service control point(SCP), based on the associate mode structure. Evaluation by implementing a node system shows that it requires only 15% more dynamic program steps for one sending/receiving sequence of the VP signalling than the existing method for circuit-related information. Thus, we could attain highly reliable and cost-effective signalling for ATM multimedia networks.

As MOSFET sizes and wire widths become very small in recent years, influence of resistive component of interconnects on the estimation of propagation delay and power dissipation can no longer be neglected. In this paper we present formulas of output waveform at driving point and short-circuit power dissipation for static CMOS logic gates driving a CRC π load. By representing the short-circuit current and the current flowing in the resistance of a CRC π load by piece-wise linear functions, a closed-form formula is derived. On the gate delay the error of our formula is less than 8% from SPICE in our experiments. These formulas will contribute to faster estimation of circuit speed and power dissipation of VLSI chips on timing level simulators.

Contact recording systems have been studied for future magnetic recording disks with a high recording density. Tribological key technologies for ultra-low spacing and high wear performance are required for the contact systems. Particularly, a liquid lubrication system plays an important roll for reducing a mechanical spacing and improving wear performances. However, a lubrication design concept for contact recording systems is not established. In this study, molecular design of lubricants for contact systems will be discussed from a viewpoint of bouncing and wear behaviors. As a result, a minimum bouncing height of 3 nm and a high wear performance were obtained for ion-etched contact sliders by the optimization of design parameters, i. e. pad design and lubricant material.

In this paper, a new variable length code transmission technique utilizing multicode DS/SS is proposed. A common problem associated with the use of variable length codes over wireless channels is loss of synchronization due to bit inversion caused by channel noise. The loss of synchronization produces burst errors in the received source symbols. The proposed system assigns multiple spreading codes to a single user to transmit variable length codes. The number of the spreading codes is equal to the maximum bit length of the codewords. All the bits of the codeword are spread and transmitted at one time by utilizing the assigned multiple spreading codes. Therefore no synchronization of the codeword is required. This paper evaluates the performance of the proposed technique over an AWGN channel and a Rayleigh fading channel. Our results show that the proposed technique improves the symbol error rate (SER) performance by 2-3 dB on the AWGN channel and 10-20 dB on the Rayleigh fading channel as compared with a conventional transmission technique. The source-channel coding suitable for the proposed technique improves the performance by another 15 dB on the Rayleigh fading channel. The proposed transmission technique works even in a low Es/No region.

In the multipath mobile channel, the received signal suffers from both the fluctuation in the received field intensity caused by fading and waveform distortion caused by the echo. Diversity reception using multiple spaced antennas is an effective method to compensate for fading, while echo cancellation with an adaptive array is good at compensating for waveform distortion. In this paper, an adaptive switching echo cancellation/diversity reception method to compensate for both waveform distortion and fading is proposed. The proposed switching reception monitors the impacts of channel conditions on received signal and then one of an echo canceller and a diversity receiver is selected accordingly to compensate the channel. The compensation performance of the proposed switching reception in terms of both average DUR (Desired to Undesired signal Ratio) and the probability of DUR below a threshold value is investigated with computer simulation. The results show that the adaptive switching echo cancellation/diversity reception has realized the advantages of both adaptive echo cancellation and diversity reception.

We developed a glass ferrule fiber optic connector. During development, we also studied wear-resistant coating technology for preventing scratches on the surface of a glass ferrule. The method of coating was sputtering, and the material was alumina. We confirmed that a thin uniform coating could be formed on the ferrule surface to improve the durability of glass ferrule connectors.

Solder joint reliability was studied for hybrid ICs, in which chip components such as FETs, resistors and capacitors were mounted with Sn-Sb solder on an insulated Al substrate and transfer-molded with epoxy resin. Suitable resin selection for molding was also studied. The structure was estimated to have a lifetime of more than ten thousand cycles in the thermal cycling test under the condition of -55/150, for FETs and passive elements. Equivalent plastic strains generated in the soldering layer for the non-molded structure were 4. 6% for the FETs and 3.5% for the passive elements. But, these strains were approximately 1/3 to 1/2 and 1/10 for the molded structure, respectively. This was the main reason for high reliability of the molded structure. Resins with a wide range of thermal expansion coefficient(8-26 ppm/)could be put to practical use, because of the higher reliability of the molded structure. However, a thermal expansion coefficient of about 15 ppm/ was prefered to decrease stress at the interface between the substrate and the molding resin.

Surface damage of the electrical contact is a primary cause of failure in many electronic devices which use sliding contacts. Therefore, the quantitative observation of the contact surface is one of the most important subjects for improvement of contact reliability. In this study, in order to clarify the relationship between the contact resistance and the damage on the contact surface, a digital image measuring system (DIMS) was developed. A shadow image processing technique (SIPT) was applied to the damage analysis on the sliding contact surface. The damage width on the contact surface and the damaged image could be obtained with a 3-D graphic image by applying both DIMS and SIPT. Part of the relationship between the damage on the contact surface and the contact resistance could be obtained in the case when Cu is used for the moving contact and Cu and Ni are used for the static contact.

The characteristics of circular polarization from a slot with a parasitic dipole are investigated analytically. It is derived that its phase is linearly dependent upon the angle of the dipole and is independent of that of slot. This interesting behavior is also confirmed by experiments.

Repeaterless transmission system design employing remote pumping in a single fiber is clarified. The design is aimed to realize cost effective submarine transmission systems with easy maintenance. Remote pumping in a single fiber can extend repeaterless transmission distance without decreasing the system capacity per cable. It is applicable for high-count-fiber cable such as the 100-fiber submarine cable already developed. A simple but effective system configuration is presented that uses remote pumping from receiver end; both remote-pre erbium-doped fiber (EDF) amplification and backward pumping Raman amplification are employed. Stable transmission can be obtained without optical isolators, therefore the optical time domain reflectometry (OTDR) method is supported by this system. Three fiber configurations, which consist of dispersion shifted fiber (DSF), pure silica core fiber (PSCF) and a combination of DSF and PSCF, are examined to compare system performance. Remote-pre EDF is optimized in terms of length and location from receiver end by optical SNR (OSNR) calculations. Maximum signal output power is also determined through a waveform simulation based on the split-step Fourier method, in order to avoid waveform distortion caused by the combined effect of self-phase modulation (SPM) and group velocity dispersion (GVD). Through these calculations and simulations, we confirm the proposed repeaterless transmission system performance of 600Mbit/s-451 km with PSCF, 2. 5 Gbit/s-407 km with DSF + PSCF, and 10 Gbit/s-376 km with DSF+PSCF, which include system margin.

One of the ways to execute a processing algorithm in high speed is parallel processing on multiple computing resources such as processors and functional units. To identify the minimum number of computing resources, the most important is the scheduling to determine when each operation in the processing algorithm is executed. Among feasible schedules satisfying all the data dependencies in the processing algorithm, an overlapped schedule can achieve the fastest execution speed for an iterative processing algorithm. In the case of processing algorithms with operations which are executed on some conditions, computing resources can be shared by those conditional operations. In this paper, we propose a scheduling method which derives an overlapped schedule where the required number of computing resources is minimized by considering the sharing by conditional operations.