An innovative small planar packaging(SPP)system is described that can be combined with card-on-board(COB)packaging in high-speed asynchronous transfer mode switching systems with throughput of over 40-Gb/s. The SPP system provides high I/O pin count density and high packaging density, combining the advantages of both planar packaging used in computer systems and COB packaging used in telecommunication systems. Using a newly developed quasi-coaxial zero-insertion-force connector, point-to-point 311 Mb/s of 8-bit parallel signal transmission is achieved in an arbitrary location on the SPP systems shelf. Also about 5400 I/O connections in the region of the planar packaging system are made, thus the SPP system effectively eliminates the I/O pin count limitation. Furthermore, the heat flux management capability of the SPP system is five times higher than of conventional COB packaging because of its air flow control structure. An SPP system can easily enlarge the switch throughput and it will be useful for future high-speed, high-throughput ATM switching systems.

Exception handling is not only useful for increasing program readability, but also provides an effective means to check and locate errors, so it increases productivity in large-scale program development. Some typical and frequent program errors, such as out-of-range indexing, null dereferencing, and narrowing violations, cause exceptions that are otherwise unlikely to be caught. Moreover, the absence of a catcher for exceptions thrown by API procedures also causes uncaught exceptions. This paper discusses how the exception handling mechanism should be supported by the compiler together with the operating system and debugging facilities. This mechanism is implemented in the compiler by inserting inline check code and accompanying propagation code. One drawback to this approach is the runtime overhead imposed by the inline check code, which should therefore be optimized. However, there has been little discussion of appropriate optimization techniques and efficiency in the literature. Therefore, a new solution is proposed that formulates the optimization problem as a common assertion elimination (CAE). Assertions consist of check code and useful branch conditions. The latter are effective to remove redundant check code. The redundancy can be checked and removed precisely with a forward iterative data flow analysis. Even in performance-sensitive applications such as telecommunications software, figures obtained by a CHILL optimizing compiler indicate that CAE optimizes the code well enough to be competitive with check suppressed code.

Large-area high-temperature superconducting films and damage-free processing techniques have been developed to fabricate low insertion loss and sharp skirt filters for mobile telecommunication. An off-axis-type dc sputtering method was employed to deposit Y-Ba-Cu-O films on both sides of the substrate. The surface resistance of the films was about 0. 35 mΩ(at 70 K and 10 GHz). An 11-pole bandpass receiving filter for the IS-95 telecommunication system was designed and fabricated using 60 mm 50 mm YBCO films on a 0. 5-mm-thick MgO substrate. The passband insertion loss at 70 K was about 0. 1 dB with 0. 1 dB ripple. The third-order intercept point of the filter was 49. 5 dBm. We have assembled the filter and a low-noise amplifier in a dewar with a cryocooler. Ultralow-noise performance (noise figure: 0. 5 dB at 70 K) was presented by the cryogenic filter subsystem.

We describe several properties of very thin stacks of 10 to 20 intrinsic Josephson junctions fabricated on the surface of Bi2Sr2CaCu2O8+δ single crystals. We show that the Joule heating is significantly reduced in these stacks and that the gap structure is clearly observable in the quasiparticle current-voltage (I-V) characteristics. The I-V curves are characterized by a large subgap conductance and a significant gap suppression due to the injection of quasiparticle current. It is found that the IcRn product of these intrinsic Josephson junction stacks is significantly small compared with that expected from the BCS theory. It is also found that there is a tendency that IcRn decreases with increasing c-axis resistivity. Both Ic and the gap voltage exhibit unsaturated temperature dependence at low temperatures. The behavior presents a sharp contrast to that of Josephson junctions made of conventional superconductors. The characteristics are discussed in relation to the d-wave symmetry of the order parameter.

We have studied an in situ edge preparation process and the effect of a substrate rotation during the edge preparation in order to improve the uniformity and electrical characteristics of high-Tc edge-type Josephson junctions. The improved YBa2Cu3Ox/PrBa2Cu3Ox/YBa2Cu3Ox edge junctions showed small 1σ-critical current spreads as low as 10% for 12 junctions. We have confirmed that the spreads do not increase significantly by adding groundplane over the junctions. In this paper, we will describe these processes developed for the fabrication of high-Tc superconducting integrated circuits.

In this paper, we present a method for evaluating the minimum free Chernov distance of trellis-codes for a discrete memoryless channels (DMC). In order to design an efficient trellis-code for the DMC, we need to evaluate the minimum free Chernov distance of the target code. However, the lack of the additive property of the Chernov distance prevents a conventional branch-and-bound search for evaluating the minimum distance. To overcome the difficulty, we present a lower bound on the Chernov distance with an additive property. The lower bound plays a key role in the minimum distance evaluation algorithm presented here. By using the proposed algorithm, we have derived the minimum free Chernov distance of some binary linear convolutional codes over Z-channel.

In general, the performance of partial response maximum-likelihood (PRML) system is degraded by nonlinear distortion and high frequency noise in high-density digital magnetic recording. Conventional PRML system for single-track recording improves the performance when high order PRML systems and high rate codes are adopted. But, in general it is difficult to realize LSI circuits for high order PRML system and high rate code. In this paper, a trellis coded class four partial response maximum-likelihood (TC-PR4ML) system for high density two-track digital magnetic recording is proposed. Our two-track recording method can increase the coding rate over 1, which contributes to a decrease in both degradation effects from partial erasure, one of nonlinear distortions, and high frequency noise in high density recording. The error rate performance of the proposed system is obtained by computer simulation taking account of the partial erasure and it is compared with that of a conventional NRZ coded class four partial response maximum-likelihood (NRZ-PR4ML) system. The results show that the proposed system is hardly affected by partial erasure and keeps good performance in high density recording.

We propose a method of reducing laser-clipping-induced distortion in a subcarrier multiplexed (SCM) optical-cable TV system. This scheme reduces amplitude peaks of the SCM signal by controlling the phases of video carriers to prevent the clipping which occurs when these peaks fall below the threshold of a laser-diode. It is experimentally shown that using this method reduces the bit error rate in an AM-VSB / QAM hybrid optical-transmission system.

A key distribution system is a system in which users securely generate a common key. One kind of identity-based key distribution system was proposed by E. Okamoto. Its security depends on the difficulty of factoring a composite number of two large primes like RSA public-key cryptosystem. Another kind of identity-based key distribution system was proposed by K. Nyberg, R. A. Rueppel. Its security depends on the difficulty of the discrete logarithm problem. On the other hand, Koblitz and Miller described how a group of points on an elliptic curve over a finite field can be used to construct a public key cryptosystem. In 1997, we proposed an ID-based key distribution system over an elliptic curve, as well as those over the ring Z/nZ. Its security depends on the difficulty of factoring a composite number of two large primes. We showed that this system over an elliptic curve is more suitable for the implementation than those over the ring Z/nZ. In this paper, we apply the Nyberg-Rueppel ID-based key distribution system to an elliptic curve. It provides relatively small block size and high security. This public key distribution system can be efficiently implemented. However the Nyberg-Rueppel's scheme requires relatively large data transmission. As a solution to this problem, we improve the scheme. This improved scheme is very efficient since data transferred for the common key generation is reduced to half of those in the Nyberg-Rueppel's scheme.

This study shows the effectiveness of the simulation probability density function (p. d. f. ) based on the Bhattacharyya bound from the point of view of the twisted distribution. As a result, the simulation p. d. f. related to the Bhattacharyya bound is asymptotically optimal for the trellis coded modulation scheme under some practical conditions. And the optimality is also confirmed by a numerical example.

YBa2Cu3Ox films were grown on MgO(100) substrates by liquid phase epitaxy. Their structural and electrical properties were examined. From TEM plan-view images, it is found that the film consists of large grains whose misorientation angles are less than 1. Although the DC critical current density values decrease with increasing the film thickness, the critical current density value of 9. 3105 A/cm2 at 77 K is obtained for a 7 µm-thick film. A microstrip resonator at 10. 8 GHz with a YBCO ground plane shows Q0 values of 14200 at 77 K and 23300 at 40 K, which correspond to surface resistance values of 650 and 400 µΩ, respectively. By using a microstrip line resonator with a Ti/Au ground plane, the critical field of the film at 77 K and 10. 8 GHz is estimated to be 30 Oe. The third-order intercept of the resonator with the Ti/Au ground plane is the input power of +43 dBm and the output power of +30 dBm at 77 K.

In this paper, we propose a new conference key distribution scheme and the supervision of a conference when users are in a level-based hierarchy. In a conference key distribution system, one message is transmitted to the participants from a chairman, a legitimate member can decrypt it and reveal the common session key. The proposed scheme can be implemented without using any tamper-proof hardware. For users in a level-based hierarchy, by applying the key distribution scheme, the higher priority users can derive the conference key and supervise the lower level users' communications. Further, the users in the same level who are not members of the conference or in lower levels can not expose the conference key. To break the common session key, a malicious user has to suffer from the difficulty of factorization and discrete logarithm problems.

The development of saturation diving in civil and defense applications has enabled man to work in the sea at great depths and for long periods of time. This advance has resulted, in part, as a consequence of the substitution of helium for nitrogen in breathing gas mixtures. However, utilization of HeO2 breathing mixture at high ambient pressures has caused problems in speech communication; in turn, helium speech enhancement systems have been developed to improve diver communication. These speech unscramblers attempt to process variously the grossly unintelligible speech resulting from the effect of breathing mixtures and ambient pressure, and to reconstruct such signals in order to provide adequate voice communication. It is known that the glottal excitation is quasi-periodic and the vocal tract filter is quasi-stationary. Hence, it is possible to use an auto regressive modelisation to restore speech intelligibility in hyperbaric conditions. Corrections are made on the vocal tract transfer function, either in the frequency domain, or directly on the autocorrelation function. A spectral subtraction or noise reduction may be added to improve speech quality. A new VAD enhanced helium speech unscrambler is proposed for use in adverse conditions or in speech recognition. This system, implementable on single chip DSP of current technology, is capable to work in real time.

This paper proposes a media synchronization mechanism for live media streams. The mechanism can also handle stored media streams by changing parameter values. The authors have implemented the mechanism on a lip-synch experimental system. Live video and voice streams input at a source workstation are transferred, and then they are synchronized and output at a destination workstation. This paper also evaluates the system performance such as mean square error of synchronization, average output rate, and average delay.

In the commonsense reasoning, priorities among rules are often required to be found out in order to derive the desired conclusion as a theorem of the reasoning. In this paper, first we present the bottom-up and top-down abduction procedures to compute skeptical explanations and secondly show that priorities of circumscription to infer a desired theorem can be abduced as a skeptical explanation in abduction. In our approach, the required priorities can be computed based on the procedure to compute skeptical explanations provided in this paper as well as Wakaki and Satoh's method of compiling circumscription into extended logic programs. The method, for example, enables us to automatically find the adequate priority w. r. t. the Yale Shooting Problem to express a human natural reasoning in the framework of circumscription.

An asynchronous pulse neural network model which is suitable for VLSI implementation is proposed. The model neuron can function as a coincidence detector as well as an integrator depending on its internal time-constant relative to the external one, and show complex dynamical behavior including chaotic responses. A network with the proposed neurons can process spatio-temporal coded information through dynamical cell assemblies with functional synaptic connections.

In the IETF, discussions on the authentication method of the Dynamic Host Configuration Protocol (DHCP) message are active and several methods have been proposed. These related specifications were published and circulated as the IETF Internet-Drafts. However, they still have several drawbacks. One of the major drawbacks is that any user can reuse addresses illegally. A user can use an expired address that was allocated to a host. This kind of "illegal use" of the addresses managed by the DHCP server may cause serious security problems. In order to solve them, we propose a new access control method to be used as the DHCP message authentication mechanism. Furthermore, we have designed and developed the DAG (DHCP Access Control Gateway) according to our method. The DAG serves as a gateway that allows only network accesses from clients with the address legally allocated by the DHCP server. This provides secure DHCP service if DHCP servers do not have an authentication mechanism, which is most likely to occur. If a DHCP server has such an authentication scheme as being proposed in IETF Internet-Draft, the DAG can offer a way to enable only a specific client to access the network.

This paper presents both new analytical and new numerical solutions to the problem of generating waveforms exhibiting a low peak-to-peak factor. One important application of these results is in the generation of pseudo-white noise signals that are commonly uses in multi-frequency measurements. These measurements often require maximum signal-to-noise ratio while maintaining the lowest peak-to-peak excursion. The new synthesis scheme introduced in this paper uses the Discrete Fourier Transform (DFT) to generate pseudo-white noise sequence that theoretically has a minimized peak-to-peak factor, Fp-p. Unlike theoretical works in the literature, the method presented here is based in purely discrete mathematics, and hence is directly applicable to the digital synthesis of signals. With this method the shape of the signal can be controlled with about N parameters given N harmonic components. A different permutation of the same set of offset phases of the "source harmonics" creates an entirely different sequence.

This paper describes an efficient simulation algorithm for the spatiotemporal pattern analysis of the continuous-time neural networks with the multivalued logic (multivalued continuous-time neural networks). The multivalued transfer function of neuron is approximated to the stepwise constant function which is constructed by the sum of the step functions with the different thresholds. By this approximation, the dynamics of the network can be formulated as a stepwise constant linear differential equation at each timestep and the optimal timestep for the numerical integration can be obtained analytically. Finally, it is shown that the proposed method is much faster than a variety of conventional simulators.

This letter presents a new algorithm for improving the Signal to Noise Ratio (SNR) of complex sinusoidal signals contaminated by additive Gaussian noises using sum of Higher-Order Statistics (HOS). We conduct some computer simulations to show that the proposed algorithm can improve the SNR more than 7 dB compared with the conventional coherent integration when the SNR of the input signal is -10 dB.