A uniquely decodable code pair (C, S) is considered for the two-user binary adder channel. When the first code C is linear, a lower bound of |S| is formulated and a uniquely decodable code pair (C, S) is presented. When a rate R1 of C is less than 1/3, a rate R2of S is greater than the best rate known previously.

There are some results indicating that a quantum computer seems to be more powerful than ordinary computers. In fact, P.W. Shor showed that a quantum computer can find discrete logarithms and factor integers in polynomial time with bounded error probability. No polynomial time algorithms to find them using ordinary computers are known. In this paper, we show that the cycles in some kinds of periodic functions, e.g., functions proposed as pseudo-random generators, can be found in polynomial time with bounded error probability on a quantum Turing machine. In general, it is known that ordinary computers take exponential time to find the cycles in periodic functions.

The benefits of ATM techniques have been widely recognized and many organizations envisage the introduction of ATM techniques into their telecommunication networks. The ATM benefits can, however, be fully exploited only after effective network resource management techniques have been developed. This paper focuses on CBR-VP management techniques. The ATM transport network architecture and VP roles are summarized. Next, the issues of VP accommodation design are described. The point is how to create a design that accommodates cell loss and cell delay jitter, both of which depend on various network parameters and conditions. For this purpose, analytical procedures based on an M/D/1 queueing model are adopted. The approximation method is shown to be very effective in practical use through computer analysis. The method guarantees conservative QOSs. Finally, the proposed method is applied to several design examples to illustrate VP management issues. The proposed method will enable ATM techniques to be introduced to our telecommunication networks by the mid-1990's.

This letter propose a fast frequency domain adaptive filter algorithm (FADF) for applications in which large order adaptive filters are required. Proposed FADF algorithm reduces the block delay of conventional FADF algorithms allowing a more efficient selection of the fast Fourier Transform (FFT) size. Proposed FADF algorithm also provides faster convergence rates than conventional FBAF algorithms by using a near-optimum convergence factor derived by using the FFT. Computer simulations using white and colored signals are given to show the desirable features of proposed scheme.

This paper examines the feasibility of a high frequency (moro than 1 GHz) ring-oscillator-type CMOS VCO, able to maintain a good linearity between the oscillator output frequency and control voltage, while preserving low voltage and low power operation capabilities. A CMOS VCO circuit, with a newly developed corrent-controlled delay cell and an architecture combining the transitions of each delay cell output, with high-frequency operation, was designed and simulated using the CMOS 0.6 µm device paramenters. We analyzed the generation of unnecessary harmonics and sub-harmonics when a delay cell's propagation delay time varied. The simulation indicated that a CMOS VCO with a frequency range of 200 MHz to 1.4 GHz, a power dissipation of 8.5 mW at 900 MHz from a 3 V power supply, and an operation voltage of 1 V to 3 V can be implemented on a chip.

A filter configuration that allows configuration of any transfer function used the state variable is discribed as an application of the second generation current conveyors (CCIIs) to RC networks. The filter types discussed are low-pass filter (LPF), high-pass filter (HPF), band-pass filter (BPF), all-pass filter (APF), and band-elimination filter (BEF). The filter circuit consists of four CCIIs and allows tandem connections. The device sensitivity and CCII's sensitivity to transfer coefficient are relatively low. The filter circuit that allow simultaneous configuration wewe fabricated. An experimental result at around 10kHz was obtained for the filters. In the case, the LPF, HPF, BPF, APF, and BEF characteristics are obtained at Q value of 5.0.

A new adaptive AR spectral estimation method is proposed. While conventional least-squares methods use a single windowing function to analyze the linear prediction error, the proposed method uses a different window for each frequency band of the linear prediction error to define a cost function to be meinemized. With this approach, since time and frequency resolutions can be traded off throughout the frequency spectrum, an improvement on the precision of the estimates is achieved. In this paper, a wavelet-like time-frequency resolution grid is used so that low-frequency components of the linear prediction error are analyzed through long windows and high-frequency components are analyzed through short ones. To solve the optimization problem for the new cost function, special properties of the correlation matrix are used to derive an RLS algorithm on the order of M2, where M is the number of parameters of the AR model. Computer simulations comparing the performance of conventional RLS and the proposed methods are shown. In particular, it can be observed that the wavelet-based spectral estimation method gives fine frequency resolution at low frequencies and sharp time resolution at high frequencies, while with conventional methods it is possible to obtain only one of these characteristics.

A miniature transceiver, including highly integrated MMIC front-end, for 1.9 GHz band personal handy phone system(PHS) has been developed. The terminal, adopting direct conversion transmitter and receiver technology, consists of four high-density RF circuit modules and a digital signal processing LSI with 2.7 V power supply. The four functional modules are a power amplifier, a transmitter,a receiver, and a frequency synthesizer. Each functional module includes one IC chip and passive LCR components connected with solder bumps on module substrate. The experimental miniature PHS handset has been fabricated to verify the design concepts of the miniature transceiver. The total volume of the developed PHS terminal is 60cc, including the 12cc front-end which comprises the four RF functional circuit modules. The air interface connection with the PHS base station simulator has been confirmed.

A 1.9GHz direct conversion receiver(DCR) chip which integrates an LNA, I/Q mixers(MIX), active lowpass filters(LDF) and variable gain amplifiers(VGA) was fabricated. Because the DCR for QPSK modulation systems is sensitive to the 2nd-order nonlinearity, linearization techniques are adopted in MIX and LPF. The DCR chip was fabricated using a BiCMOS process, and the die size is 5.1 mm by 5.1mm. The chip can operate from 2.7 V supply voltage and consumes 165mW when all the functions are activated. Suppression of local signal radiation and the 2nd-order distortion indicate the feasibility of Si-based DCR for QPSK modulation systems such as PHS.

Asynchronous Transfer Mode (ATM) is a promised bearer transmission service for high speed multimedia LAN. Recently, high speed multimedia ATM LAN products have been available. Therefore, in order to interconnect them, the multimedia backbone LAN, which has the expandable high throughput over 10Gbps, supporting multicast, multi-QoS, and many interfaces including 622 Mbps, will be widely required. In this paper, the VLSI oriented input and output buffered switch architecture is proposed as the hardware architecture for multimedia backbone switch node. This paper describes that the chip set consisting of four VLSIs, that is, the switch element, the switch access, the distributor/arbiter, and the multiplexer/demultiplexer, can realize the backbone switch core, and the main specifications required to each VLSI are derived.

This paper proposes a method to predict and control noise voltage caused by electrostatic discharge (ESD) to electronic equipment. The relationship of grounding system configurations for a typical set of equipment to ESD immunity has been derived using a mechanism of ground potential variations. The equivalent circuit representing ground elements as lumped constants enables us to predict the transient ground potential differences between PCB (Printed Circuit Board) ground planes connected via signal cables and induced noise voltage at the receiving end. The calculation shows that the contribution of ground potential differences to noise voltage is comparable to that of the electromagnetic coupling between the discharge current on the enclosure and the circuit loops. The calculation also shows some characteristic results, such as; the induced noise voltage is remarkably dependent on the unbalance in ground cable lengths and on the impedance of ground conductors connecting PCBs, especially when the equipment uses a single-point grounding system. These characteristics were confirmed by measurements of induced ground potential differences, noise voltage and immunity levels. Thus the proposed method is shown to be very effective to analyze the dependency of grounding conditions on ESD immunity and to improve ESD immunity in equipment design.

Recently, ABR has been attracting attention as a new service category of ATM, and the methodology to realize ABR is being actively discussed in the ATM Forum. ABR is expected to become a suitable class for supporting LAN services on ATM networks. To this end, a technical foundation must be established in which bandwidth is effectively utilized and quality is guaranteed. In order for ABR to use a portion of the bandwidth that is not used by high-priority classes (CBR, VBR), it is necessary to appropriately estimate the unused portion of the bandwidth. Due to the fact that the unused portion of the bandwidth in ATM networks fluctuates, such fluctuations must be taken into account. This paper describes ABR connection admission control and design of the congestion detecting point in an ABR buffer using Allan variance of the unused portion of the bandwidth.

The coupling response of an external transient electromagnetic field to a transmission line is considered. An experiment has been conducted to verify the line equations for a transmission line excited externally by a transient near field. The model field is generated by a monopole antenna installed in the vicinity of the transmission line and driven by a step waveform. The waveform is analyzed into discrete spectrum components using a Fourier transform. The frequency-domain field components affecting the transmission line are estimated by the moment method, and then the induced frequency-domain voltage at the terminal load is converted into a time-domain voltage using an inverse Fourier transform. Comparison between the measured and the computed values provides verification of the line equations. The coupling mechanism is discussed from the experimental results. It seems equivalently that the transmission line picks up the field, generated at the feed point and the top point of the monopole antenna, at both terminal ends.

A new superresolution technique is proposed for high-resolution estimation of the scattering analysis. For complicated multipath propagation environment, it is not enough to estimate only the delay-times of the signals. Some other information should be required to identify the signal path. The proposed method can estimate the frequency characteristic of each signal in addition to its delay-time. One method called modified (Root) MUSIC algorithm is known as a technique that can treat both of the parameters (frequency characteristic and delay-time). However, the method is based on some approximations in the signal decorrelation, that sometimes make problems. Therefore, further modification should be needed to apply the method to the complicated scattering analysis. In this paper, we propose to apply a time-domain null filtering scheme to reduce some of the dominant signal components. It can be shown by a simple experiment that the new technique can enhance estimation accuracy of the frequency characteristic in the Root-MUSIC algorithm.

It is demonstrated with the Berlekamp-Massey shift-register synthesis algorithm that the linear complexity value of binary complementary sequences is at least 3/4 of the sequence length. For some sequence pairs the linear complexity value can be even 0.98 times the sequence length. In the light of these results strongly non-linear complementary sequences are considered suitable for information security applications employing the spread-spectrum (SS) technique.

An adaptive decoding scheme for a concatenated code used in the frequency-hopped spread-spectrum communication system in the presence of a pulse-burst jammer is proposed and its performance is analyzed. Concatenated coding schemes employing binary inner-code and Reed-Solomon outer code are investigated and the use of side information is allowed to decode both erasures and errors. The proposed scheme makes the decoder enable to adapt to the jamming level by switching between two decoding modes such that the decoded bit error rate can be reduced. The optimal threshold value for switching in this proposed scheme is derived. It has been shown that the proposed decoding scheme yields a significant performance improvement over a conventional decoding scheme. In addition, performance analysis and its variation of adaptive decoding scheme with the imperfect side information are also presented.

This paper proposes a mutual exclusion method that is unified for the parallel and distributed systems. The method partially serializes requests into partial queues of requests, which are next totally serialized into a main queue. A request in the main queue is authorized to enter the critical section (CS) when the request receives the privilege token from the previous request in the queue. In the distributed system of N sites that each is a parallel system, mutual exclusion is performed by cooperation of two algorithms based on the same method. The algorithm for the distributed system works on a logical network (that is a directed tree) of S ( N) sites. The algorithm for each site produces a local-main queue of requests. The chunk of requests in the local queue is concatenated at a time to the partial queue of the distributed system. The the cost of mutual exclusion -- the number of intersite messages required per CS entry -- is reduced to O(1) (between 0 and 3).

Based on the test method proposed by Sub-Committee G of the International Special Committee on Radio Interference, most telephone receivers in Japan have insufficient immunity to acoustic noise caused by radio-frequency fields. This is because the modulation depth of the RF signal used is too high to accurately simulate the audio-frequency components of TV video signals. Reducing the modulation depth from 80% to 5% produces a more realistic simulation.

The synergistic effects obtained by adopting both space diversity reception and adaptive equalization play a very important role in circuit outage reduction. This paper quantitatively analyzes these synergistic effects when dispersive and flat fading occur simultaneously. Analytical results show that the synergistic effects are of the same magnitude as the adaptive equalizer improvement factor when only dispersive fading causes outage. The synergistic effects gradually disappear when noise is the predominant cause of outage.

A clique of a graph G(V,E) is a subset of V such that every pair of vertices is connected by an edge in E. Finding a maximum clique of an arbitrary graph is a well-known NP-complete problem. Recently, several polynomial time energy-descent optimization algorithms have been proposed for approximating the maximum clique problem, where they seek a solution by minimizing the energy function representing the constraints and the goal function. In this paper, we propose the binary neural network as an efficient synchronous energy-descent optimization algorithm. Through two types of random graphs, we compare the performance of four promising energy-descent optimization algorithms. The simulation results show that RaCLIQUE, the modified Boltzmann machine algorithm, is the best asynchronous algorithm for random graphs, while the binary neural network is the best one for k random cliques graphs.