A novel method is presented to the symbolic computation of Noise Figure (NF) of transistor circuits. Several computationally efficient macromodels of BJTs and MOSFETs by using nullors, are introduced. To demonstrate the suitability of the proposed method, the fully-symbolic expression of NF of a CMOS current-mirror is computed, and the total output noise-voltage is compared with HSPICE simulations. The calculated NF and the simulated noise are in good agreement. Finally, the method is extended to compute NF of a CMOS translinear circuit biased in weak inversion.

Even in embedded processors, the accuracy in a branch prediction significantly affects the performance. In designing a branch predictor, in addition to accuracy, microarchitects should consider area, delay and power consumption. We propose two techniques to reduce the power consumption; these techniques do not requires any additional storage arrays, do not incur additional delay (except just one MUX delay) and never deteriorate accuracy. One is to look up two predictions at a time by increasing the width (decreasing the depth) of the PHT (Prediction History Table). The other is to reduce unnecessary accesses to the BTB (Branch Target Buffer) by accessing the PHT in advance. Analysis results with Samsung Memory Compiler show that the proposed techniques reduce the power consumption of the branch predictor by 15-52%.

In this paper, we propose a new parallel algorithm for cellular radio channel assignment problem that can help the expanded maximum neural network escape from local minima by introducing a transient chaotic neurodynamics. The goal of the channel assignment problem, which is an NP-complete problem, is to minimize the total interference between the assigned channels needed to satisfy all of the communication needs. The expanded maximum neural model always guarantees a valid solution and greatly reduces search space without a burden on the parameter-tuning. However, the model has a tendency to converge to local minima easily because it is based on the steepest descent method. By adding a negative self-feedback to expanded maximum neural network, we proposed a new parallel algorithm that introduces richer and more flexible chaotic dynamics and can prevent the network from getting stuck at local minima. After the chaotic dynamics vanishes, the proposed algorithm then is fundamentally reined by the gradient descent dynamics and usually converges to a stable equilibrium point. The proposed algorithm has the advantages of both the expanded maximum neural network and the chaotic neurodynamics. Simulations on benchmark problems demonstrate the superior performance of the proposed algorithm over other heuristics and neural network methods.

In uplink multicarrier code division multiple access (MC-CDMA), the inter-code interference (ICI) caused by the independent and frequency-selective fading channel of each user and the inter-carrier interference caused by the asynchronous reception of each user's OFDM symbols result in multiple access interference (MAI). This paper evaluates the ICI in frequency-selective Rayleigh fading channels for uplink MC-CDMA. We derive theoretical expressions for the desired-to-undesired signal power ratio (DUR) as a quantitative representation of ICI, and validate them by comparison with computer simulations using a Walsh-Hadamard (WH) code. Based on the analytical results, we obtain the optimum spreading sequence that minimizes the ICI (in short, maximizes the multiplexing performance); this sequence appears to be orthogonal. Three equalization combining methods are examined; equal gain combining (EGC), orthogonality restoring combining (ORC), and maximum ratio combining (MRC).

A vertically connected wireless link (VCWL) using the 60-GHz band has been proposed for reliable and economical transmission of various satellite media to individual building units. This paper describes a prototype of such a VCWL that employs a self-heterodyne scheme. The CNR performance of the prototype was evaluated in a real environment. The results showed that signals transmissions of the required quality could be delivered to the units of a five-story apartment. For the placement of multiple transmitters in close proximity, the prototype required 12 dB of CIR.

Software rejuvenation is a preventive and proactive solution that is particularly useful for counteracting the phenomenon of software aging. In this paper, we consider both the periodic and non-periodic software rejuvenation policies under different dependability measures. As is well known, the steady-state system availability is the probability that the software system is operating in the steady state and, at the same time, is often regarded as the mean up rate in the system operation period. We show that the mean up rate should be defined as the mean value of up rate, but not as the mean up time per mean operation time. We derive numerically the optimal software rejuvenation policies which maximize the steady-state system availability and the mean up rate, respectively, for each periodic or non-periodic model. Numerical examples show that the real mean up rate is always smaller than the system availability in the steady state and that the availability overestimates the ratio of operative time of the software system.

The effect of the structure with difference on cross-section for the enlarged models that simulates signal transmission line (STL) in the magnetic head of HDD is discussed. The experimental results suggested that strip and shield structure are effective for suppression of EMI.

This paper proposes the design and implementation of a real-time image compressor using 2-Dimensional Discrete Wavelet Transform (2DDWT), which targets an FPGA as its platform. The image compressor uses Daubechies' bi-orthogonal DWT filters (9, 7) and 16-bit fixed-point data formats for wavelet coefficients in the internal calculation. The target image is NTSC 640240 pixels per field whose color format is Y:Cb:Cr = 4:2:2. We developed for the 2DDWT a new structure with four Multipliers and Accumulators (MACs) for real-time operations. We designed and used a linear fixed scalar quantizer, which includes the exceptional treatment of the coefficients whose absolute values are larger than the quantization region. Only a Huffman entropy encoder was included due to the hardware overhead. The quantizer and Huffman encoder merged into a single functional module. Due to the insufficient memory space of an FPGA, we utilized external memory (SDRAM) as the working and memory storage space. The proposed image compressor maps into an APEX20KC EP20K600CB652-7 from Altera and uses 45% of the Logic Array Block (LAB) and 9% of the Embedded System Block (ESB). With a 33 MHz clock frequency, the proposed image compressor shows a speed of 67 fields per second (33 frames per second), which is more than real-time operation. The resulting image quality from reconstruction is approximately 28 dB in PSNR and its compression ratio is 29:1. Consequently, the proposed image compressor is expected to be used in a dedicated system requiring an image-processing unit.

We propose a novel wavelength assignment algorithm that can establish lightpaths requiring the least wavelength conversions by chaining a minimum number of wavelength-continuous segments. Simulations show that our algorithm outperforms both first-fit and most-used schemes with large margins. Besides, moderate computational requirement and insignificant signaling overhead are also advantages of our algorithm.

An analog neurochip for independent component analysis (ICA) is designed with on-line learning capability. Due to the limited dynamic range of analog device, the nonholonomic ICA algorithm is adopted. In order to accommodate the offsets due to device mismatches, a modified algorithm is developed with 2-quadrant multipliers and self-adjusting biases. Performance of the developed system was demonstrated by Monte-Carlo simulation.

The purpose of this paper is to present a rapid prototyping flow for the development of a wireless LAN system. The proposed system flow that was used for the development of the prototype is based on the use of UML (Unified Modeling Language). The UML and its real-time extensions are used to help the development phases of the prototype, mainly in the specification, co-simulation and validation of the design. The target of the development that was carried out with the application of the UML-based methodology is the implementation of an access point for a HIPERLAN/2 wireless network. Apart from the presentation of the UML-based system design methodology the paper also presents the application of the methodology for the implementation of the system prototype, the detailed software development and the results of the development.

Arrival of the packet data is acknowledged by detecting the preambles of the received bursty packets. To increase system throughput and reduce transmission latency, a simple and robust signal detection algorithm is required. Furthermore, the threshold for signal detection must be set adaptively for different channel conditions. In this paper, we design and compare three signal detection algorithms for bursty packet systems.

Various effective and draft legislations and rules in Europe (WEEE--Waste Electrical and Electronic Equipment ROHS--Restrictions on the use of certain substances and ELV--End of life of vehicles) and Japan (Recycling Law for Home Electric Appliances) have either targeted restrictions or fully banned on the use of lead, to be enforced from 2001, 2003 and 2006 onwards. Up to now, mainly tin-lead alloys have been used in electronics. The process temperatures usually applied have been in the range of 230. All currently discussed lead-free alternatives for professional electronics need process temperatures which are at least 20 higher. In addition, the process duration is significantly longer. The combination of higher process temperatures and longer duration results in significant thermal stress on electromechanical devices. In particular the precision mechanics of electromechanical relays must withstand the solder process with maximum process temperatures of 255 without dimensional changes. During the transition from tin-lead to lead-free solder processes all combinations of component surfaces and solder must be possible. The selection of pure Sn100 or SnCu0.7 as terminal surface allows mixed assemblies with tin-lead as well as lead-free solders. All tested combinations of terminal surface, PCB surface and solder showed good results. From these results it can be concluded that mixed assemblies are possible during the transition time without any negative impact on the reliability of the electronic devices.

This paper discusses the orbital motion and elevation properties of a quasi-zenith satellite system using circular orbits. The satellites are deployed on inclined geosynchronous orbits with identical sub-satellite loci on earth. The satellites trace the locus at even intervals. This satellite system can provide mobile satellite communications and navigation services at very high elevations to middle-latitude regions. In general, the orbital parameters of the satellite system are determined by numerical simulation to maximize the minimum elevation angle in areas where satellite services are to be provided. However, an understanding of the properties of the orbit and consequent elevation properties are important for efficient constellation design. This paper formulates the orbital motion of inclined geosynchronous circular orbits, including the relative motion to the rotating earth. Although elliptical orbit constellations are also possible and can gain higher elevation, only circular orbits, which can be accurately formulated without using an analytically unsolvable Kepler's equation, are discussed in this paper. Elevation properties are evaluated using the geocentric angle between the sub-satellite point and an arbitrary point in the intended service area. This angle is a typical parameter that can be derived as a single-valued function of the elevation at a specific point. Optimum orbital parameters for an intended service area can be easily estimated without numerical simulation using the results of the evaluation described in this paper. These results can also be used to infer whether a circular-orbit constellation is applicable to an intended service area.

The authors present a multiparty signature generation (MSG) scheme of the Digital Signature Algorithm (FIPS 186-1). The scheme is based on a simple idea, however, it is much more convenient in usability in the real world than existing MSGs. The scheme has the following properties: (1) valid signatures are generated with odd n split private keys, (2) broadcast messages between the key holders are hidden from them, so that the n key holders do not need to process signature generation simultaneously, (3) even if up to t (= ) split keys are stolen, the adversary can get no information on the private key, (4) the scheme is as secure as the original signature algorithm against chosen message attack, and (5) the scheme is efficient in the sense that an implementation on smart card has demonstrated practical performance for interactive use with human user.

This paper provides a novel signal processing for detecting defects based on the spatio-temporal gradient analysis over the Lamb-wave field. The proposed processing classifies the wave field through the rank of the covariance matrix which is defined by the four-dimensional vector with following components: a vertical displacement, its vertical velocity, and a pair of out-of-plane shearing strains. The covariance matrix provides the information about defects. Its determinant, therefore, is proposed as the inhomogeneity-index of the object surface. In this study, the physical meanings of the proposed index are shown, the computational process in the Lamb-wave field near the defects is discussed and their behaviors are investigated through FDTD-simulations and acoustic experiments.

The configuration and operation of an all-optical 3R-regenerator for high-speed data transmission are described. An all-optical 3R-regenerator using a fiber-based optical switch is proposed and successfully demonstrated in a 160 Gbit/s 3R-regenerating transmission experiment.

In 1987, Ito, Saito and Nishizeki proposed a secret sharing scheme realizing general access structures, called the multiple assignment secret sharing scheme (MASSS). In this paper, we propose new MASSS's which are perfect secret sharing schemes and include Shamir's (k,n)-threshold schemes as a special case. Furthermore, the proposed schemes are more efficient than the original MASSS from the viewpoint of the number of shares distributed to each participant.

All optical regenerations or wavelength conversions using SOA-based polarization discriminated switch injected by an assist light were investigated. First of all, cross gain modulation (XGM) and cross phase modulation (XPM) in a SOA injected by an external assist light were quantitatively analyzed. A simple measurement technique of XGM and XPM was shown to confirm that the injection of assist light could reduce a gain recovery time with some sacrifice for XGM and XPM efficiency. All-optical 3R regeneration using two-stage SOA-based polarization discriminated switch at 40 Gbit/s and its tolerances for some degradation against intensity deviation and optical signal-to-noise ratio (OSNR) were also shown. Finally, regeneration capability was evaluated through a dispersion shifted fiber (DSF)-based re-circulating loop transmission experiment. Those results indicate that the SOA-based polarization discriminated switch is a promising candidate for all-optical regenerator from the practical point of view.

Mobile agent systems are essential in the next generation of electronic commercial applications. However, existing solutions for mobile agents to sign documents without user intervention are problematic because there is no restriction on who can generate the signatures. In this paper, we present a modified version of undetachable signature scheme with which the power to generate digital signatures can be designated to a neutral party. We also give a transaction model to support the scheme. Discussions regarding the security of the signature scheme as well as some attacks on its application in our model are presented too.