Reducing communication complexity is a viable approach to multilevel logic synthesis. A communication complexity based approach was proposed previously. In the previous works, only disjoint input decomposition was considered. However, for certain types of circuits, the circuit size can be reduced by using overlapped decomposition. In this paper, we consider overlapped decompositions. Some design issues for overlapped decompositions such as detecting globals" and deriving subfunctions are addressed. Moreover, the Decomposition Don't Cares (DDC) is considered for improving the decomposed results. By using these techniques together, the area and delay of circuits can be further minimized.

We have achieved the room temperature cw lasing operation of GaInAsP/InP surface emitting lasers for the first time. By employing a buried heterostructure with 1.3 µm range active region and a MgO/Si heat sink mirror, cw operation was obtained up to 14 with the threshold current of 22 mA.

This paper describes the performance of AlGaAs/GaAs HBT's developed for power applications. Their applicability to power amplifiers used in digital mobile radio communications is examined through measurement and numerical simulation, considering both power capability and linearity. Power HBT's with carbon-doped base layers showed DC current gains over 90. A linear gain of 19.2 dB, a maximum output RF power of 32.5 dBm, and a power added efficiency of 56 percent were obtained at 950 MHz. Numerical simulations showed that the power efficiency of HBT amplifiers could be improved by using harmonic trap circuits. Intermodulation measurements showed that third-order distortions were at most 21 dBc level at the 1-dB gain compression point. RF spectrum simulations using π/4 shift QPSK modulation showed that side-band spectrum generation was less than 45 dBc level at points 50 kHz off of the carrier frequency. These properties indicate that the power handling capabilities and linearity of HBT amplifiers offer promising potentials for digital mobile radio communications.

Markov chain models are used to derive the average stationary throughput and delay performance of Idle-Signal Casting Multiple Access (ICMA), with and without Failure Detection (/FD), protocols which are suitable for use in mobile packet radio local area networks, where propagation impairments are prevalent. The models consider the effects of pure Rayleigh fading on channel access and packet transmission. Numerical results, validated by computer simulations, are obtained that enable a quantitative study of the performance of the protocols. It is found that the performance of the ICMA/FD protocol is affected more significantly by fading on the base-to-mobile channel than is the performance of the ICMA protocol. In addition, performance improves with larger packet sizes eventhough such packets are more vulnerable to failure due to fading.

Fiber-optic microcellular system has been studied actively as an excellent system for solving the equipment cost problems in microcellular systems. However, the occurrence of intermodulation distortion (IMD) arising from the nonlinearity of the laser diode used for E/O conversion which degrades the transmission quality is a serious problem in this system. In this paper, we propose a new frequency switching/IM3 reduction method, which dynamically reassigns the carrier frequencies to minimize the carrier to IMD power ratio under the hostile environment with time-varying received carrier strength, and analyze the performance improvements by the proposed method. The improvements obtained both for the worst value of the overall CNR and for the overall CNR in a specific user are numerically made clear. It is also shown that if the interval between frequency reassignings is set less than one second, a sufficient improvement in the overall CNR is achievable.

Corresponding to the development of B-ISDN, integrated services for data, voice, etc. are imperatively required for the so called third generation wireless communication networks. In this paper, I-ISMA (Idle Signal Multiple Access for Integrated services) is proposed to transmit integrated voice and data traffic from dispersed terminals to a base station. In the system, data packets and the first packets of talkspurts of conversational speeches are transmitted using ISMA protocol over a shared channel while subsequent packets of talkspurts are sent with time reservation technique. The channel capacity of I-ISMA is evaluated and compared with that of PRMA. The region in which I-ISMA has larger capacity than PRMA is figured out. Generally speaking, I-ISMA has larger capacity than PRMA when the duration for transmitting and detecting an idle signal is not too long and the channel is not too congested by the reserved voice transmissions. When we concern real time voice transmission, delay is one of the most important performance measures. Only is a qualitative discussion on delay performance given here. The quantitative evaluation is obtained by the dynamic analysis in our succeeding paper.

A new arithmetic multiple-valued algebra with functional completeness is introduced. The algebra is called Neuro-Algebra for it has very similar formula and architecture to neural networks. Two canonical forms of multiple-valued functions of this Neuro-Algebra are presented. Since the arithmetic operations of the Neuro-Aglebra are basically a weighted-sum and a piecewise linear operations, their implementations are very simple and straightforward. Furthermore, the multiple-valued networks based on the Neuro-Algebra can be trained by the traditional back-propagation learning algorithm directly.

GaSb/InAs hot electron transistors (HETs) composed of a type-II misaligned quantum well operate at room temperature. The collector current is well described by the thermionic emission from the emitter. In order to get insight of the electron transport in the HET, the base width was varied or the collector barrier was modulated. The emitter's barrier height for the thermionic emission decreases with decreasing base width. This is caused by the increase of the quantum confinement energy in the InAs base with decreasing base width. Among HETs with a GaSb collector, a GaInSb abrupt layer, or a GaInSb graded layer at the collector edge, the latter type has the largest collector current. This indicates that collector grading reduces not only the collector barrier height, but also the quantum mechanical reflection of electrons. Collector-graded HETs with a 5 nm-thick base show a current gain of 8. The sheet resistance of InAs base is one order of magnitude less than bulk InAs without doping. This reduction is partly due to the accumulation of electrons transferred from the GaSb valence band to the InAs conduction band.

This paper reports performance improvement in an optical fiber feeder for microcellular mobile radio systems. A low noise optical receiver using a transformer resonant circuit is described. With this receiver, CNR degradation due to receiver noise is suppressed to less than 0.9dB. Furthermore, two novel techniques, the use of a multiple-LD transmitter and automatic LD input level control, are proposed. The multiple-LD transmitter increases transmitter output power and reduces the transmitter noise. With a dual-LD transmitter, it is possible to increase the optical loss margin by 3.1dB, which corresponds to transmission length expansion of 6.2km, or to improve the received CNR by 2.8dB, which enables communication range expansion. Automatic LD input level control, which optimizes LD input level according to the received radio power, can expand the actual dynamic range of the up link.

This paper describes an overview of wireless communications based on fiber-radio technologies from the viewpoint of system applications, particularly in the area of microcell radio systems. Feasible fiber-radio networks design are detailed in order to increase system performance and cost effectiveness. The benefits of the evolving fiber-radio microcell system are discussed with a spectral delivery scheme to meet traffic demands. Foreseeable electronic and optic technologies are reviewed in light of the key parameters to optimize the overall system. This strategy will play a role in broadband and flexible networks.

This paper summarizes basic system design for an optical fiber feeder for microcellular mobile communication systems. The optical feeder enables compact and low cost base stations, easy radio channel control and flexible mobile communication systems. Basic transmission characteristics are investigated through optical transmission experiments. By using these results, feeder performance is estimated and optimal system parameters are designed.

The threshold characteristics of mutually coupled SQUIDs (Superconducting Quantum Interference Devices) have been analytically and numerically investigated. The mutually coupled SQUIDs investigated is composed of an rf-SQUID and a dc-SQUID. Here, the rf-SQUID is a flux quantum generator and the dc-SQUID is a flux detector. The linearization method substituting sin-1x by (π/2)x (1x1) is found valid when it is applied to the mutually coupled SQUIDs, because it is possible to obtain the superconducting regions analytically. By computer implementation of linearization method, we found this method is very effective and very quick compared to the ordinary methods. We report the internal flux on an rf-SQUID, the threshold of a dc-SQUID, and that of mutually coupled SQUIDs obtained by Lagrange multiplier formulation and linearization. The features of the threshold characteristics of the mutually coupled SQUIDs with various parameters are also reported. The discontinuous behavior of threshold of the mutually coupled SQUIDs are attractive for digital applications. We suggest three applications of the mutually coupled SQUIDs, that is, a logic gate for high-Tc superconductors (HTSs), a neuron device, and an A/D converter.

In this paper, we propose an adaptive RAKE receiver, which does not need to send the sounding signals and can track the fluctuations caused by fading. The channel estimation can be done by using a least squares method of the first and second equations suppressing additive noise and tracking the channel fluctuations. It is confirmed by computer simulations that the result has good agreement with theory and the performance is almost same as that of the conventional RAKE with the sounding signals.

An approximate equation of the odd periodic correlation distribution for the family of binary sequences is derived from the exact even periodic correlation distribution. The distribution means the probabilities of correlation values which appear among all the phase-shifted sequences in the family. It is shown that the approximate distribution is almost the same as the computational result of some family such as the Gold sequences with low even periodic correlation magnitudes, or the Kasami sequences, the bent sequences with optimal even periodic correlation properties in the sense of the Welch's lower bound. It is also shown that the odd periodic correlation distribution of the family with optimal periodic correlation properties is not the Gaussian distribution, but that of the family of the Gold sequences with short period seems to be similar to the Gaussian distribution.

The effectiveness of error-control coding in a frequency-hop radio system can be increased greatly by the use of side information that is developed in the radio receiver. The transmission of test symbols provides a simple method for the derivation of side information in a slow-frequency-hop receiver. Requirements on the reliability of the side information are presented, and their implications in determining the necessary number of test symbols are described. Other methods for developing side information are reviewed briefly, and applications of side information to routing protocols for frequency-hop packet radio networks are discussed.

The Cooper pairing interaction in high Tc oxide superconductor is discussed in terms of an empirical expression; TcDexp[1/g], gcωo which was derived in our previous investigation. The dual character of this expression consisting of the phonon Debye temperature D and electronic excitation ωo in the mid-infrared region can be interpreted on the basis of the phonon-assisted mechanism on carrier conduction and the electronic excitation. A tunneling spectrum here presented shows certain evidence of the phonon contribution. The characteristics of the long range superconductive proximity phenomena recently reported are also may be interpreted by this mechanism.

The bit error performance of a Direct Sequence Spread Spectrum Communication system in actual land mobile satellite channel is evaluated with experiments. Field test results with the ETS-V satellite in urban and suburban environments at L-band frequency show that this land mobile satellite channel of 3MHz bandwidth can be seen as a non-frequency selective Rician fading channel as well as shadowing channel. The bit error performance can be estimated from signal power measurement as in the case of narrow band modulation signals.

Concatenated coding techniques are applied to slow frequency-hop packet radio communications for channels with partial-band interference. Binary orthogonal signaling (e.g., binary FSK) is employed with noncoherent demodulation. The outer codes are Reed-Solomon codes and the inner codes are convolutional codes. Two concatenated coding schemes are compared. The first employs an interleaver between the outer Reed-Solomon code and the inner convolutional code. The second scheme employs an additional interleaver following the convolutional code. Comparisons are made between the performance of these concatenated coding schemes and the performance of Reed-Solomon codes alone.

An algorithm interpolating parallel cross-sections between CT slices is described. Contours of equiscalar or constant-density surfaces on cross-sections are directly obtained as non-intersecting loops from grayscale slice images. This algorithm is based on a general algorithm that the authors have proposed earlier, constructing triangulated orientable closed surfaces from grayscale volumes and is particularly suited for a new technique, called laser stereolithography, which creates real 3D plastic objects using UV laser to scan and harden liquid polymer. The process of laser stereolithography is executed slice by slice, and this technique really requires some interpolation of intermediate cross-sections between slices. For visualizing, surfaces are only expected to be shaded almost continuously. The local defects are invisible and not cared about if the picture resolution is rather poor. On the contrary, topological faults are fatal to construct solid models by laser stereolithography, i.e., every contour line on cross-sections must be closed with no intersection. Not a single break of a contour line is tolerated. We already have many algorithms available for equiscalar surface construction, and it seems that if we cut the surfaces, then contour lines could be obtained. However, few of them are directly applicable to solid modeling. Marching cubes algorithm, for example, does not ensure the consistency of surface topology. Our algorithm guarantee an adequate topology of contour lines.

The spread spectrum system (abbreviated as SS system) is known to be an excellent communication system which resists jamming. Recently, its application to a simplified wireless communication system has been considered to be suited for consumer communication. In Japan, SS wireless LAN system has got the approval on 2.4GHz ISM band already. A compact SS transceiver for the SS wireless LAN is realized, whose data ratio is 230kbps. The SS transceiver is based on a direct sequence for the modulation, and the demodulation is carried out by a specially developed SAW device. In the first part of this paper, the technical conditions of the SS wireless LAN are mentioned. Then the SAW device and the principle of the demodulation are discussed. Finally, the configuration of the SS transceiver and the protocol of the SS wireless LAN are presented.