Heterojunction bipolar transistors (HBTs) are key devices for a variety of applications including L-band power amplifiers, high speed A/D converters, broadband amplifiers, laser drivers, and low phase noise oscillators. AlGaAs emitter HBTs have demonstrated sufficient reliability for L-band mobile phone applications. For applications which require extended reliability performance at high junction temperatures (>250) and large current densities (>50 kA/cm2), InGaP emitter HBTs are the preferred devices. The excellent reliability of InGaP/GaAs HBTs has been confirmed at various laboratories. At a moderate current density and junction temperature, Jc = 25 kA/cm2 and Tj = 264, no device failures were reported out to 10,000 hours in a sample of 10 devices. Reliability testing performed up to a junction temperature of 360 and at a higher current density (Jc = 60 kA/cm2) showed an extrapolated MTTF of 5 105 hours at Tj = 150. The activation energy for AlGaAs/GaAs HBTs was 0.57 eV, while the activation energy for InGaP/GaAs HBTs was 0.68 eV, which indicated a similar failure mechanism for both devices.

The Matrix-Pencil (MP) method is applied to the estimation of the undesired radiation from the microstrip line discontinuities. The Q factors are obtained from the complex resonant frequencies estimated from FDTD transient field by using MP. The number of the damped oscillations is estimated by using MDL which is widely used as an information theoretic criterion for the model order estimation.

This paper describes a novel layout optimization technique using electromagnetic (EM) simulation. Simple equivalent circuits fitted to EM simulation results are employed in this method, to present a modification guide for a layout pattern. Fitting errors are also investigated with some layout patterns in order to clarify the applicable range of the method, because the errors restrict the range. The method has been successfully adopted to an X-band low noise MMIC amplifier (LNA). The layout pattern of the amplifier was optimized in only two days and the amplifier has achieved target performances--a 35 dB gain and a 1.7 dB noise figure--in one development cycle. The effective chip area has been miniaturized to 4.8 mm2. The area could be smaller than 70% in comparison with a conventional layout MMIC.

Due to the large number of I/O's in a Ball-Grid-Array (BGA) package, routing becomes more and more an important work. A ring-based router for the BGA package is presented in this paper to interconnect each I/O pad of a chip to a corresponding ball distributed on the substrate area. The major phases for the router consist of layer assignment, topological routing, and physical routing. Using this router, we can generate an even distribution of planar and any-angle wires to improve manufacturing yield. We have also conducted various testing examples to verify the efficiency of this router. Experiments show that the router produces very good results, far better than the manual design, thus it can be applied to the practical packaging of integrated circuits.

As telecommunications companies face the rigors of competition, they soon find that their operational support systems play a critical role in providing new services faster, at lower cost and with better quality than their competitors. At TeleManagement Forum, the model for the successful service provider is 'the smooth operator' - a company whose processes and systems fully support its people to provide the best services possible at the lowest cost. Learning the importance of becoming a 'smooth operator' is hard, particularly as it requires giving up the old way of doing things - moving from an internal development environment to one that can take full advantage of 'off-the-shelf' software. The reasons for this shift include a shortage of resources, shortage of time, and the need to do business as part of a greater (and growing) global supply chain. Getting to 'smooth operator' status can be made easier with help from organizations like the TeleManagement Forum. In this paper, a twelve-step method is outlined to give pointers to service providers and their suppliers on how to make the journey successfully.

Up to now, a lot of efforts have been made for the management of telecommunication networks and equipment, but less effort has been made for the realization of higher-layer service and business management. Common Object Request Broker Architecture (CORBA) provides the infrastructure for interoperability of various object-oriented management applications in a distributed environment, and being widely used to develop distributed systems in many areas of information processing technologies. There are recently worldwide growing interests for applying CORBA technology for the realization of higher layer Telecommunication Management Network (TMN) management functions. In this paper, we propose a platform architecture for the efficient integration of CORBA technology within TMN framework, where CORBA-based management functions as well as TMN-based management functions can be realized efficiently. GDMO/ASN. 1 to IDL translator has been designed and implemented for translating TMN management information into OMG CORBA IDL interface. The CORBA/CMIP gateway has also been designed for realization of the interaction translation specification of JIDM task force with some additional extensions. Finally, we evaluate the performance of the CORBA-based network management system, and analyze the code reusability for the construction of the CORBA-based management system, in order to show the efficiency of the architecture.

RSPICE, a fast timing simulator for large digital MOS circuits, is presented in this paper. A new table-based region-wise linear MOS transistor model and the analytical solution of the generic sub-circuit primitive are applied to calculate the transient response of digital MOS circuits. The body effect of pass transistors is included in the MOS model and the floating capacitor network can be handled by this sub-circuit primitive as well. In RSPICE, MOS transistors with a DC path are grouped into a DC-connected block (DCCB), and DCCBs with a feedback path are combined as a strongly connected component (SCC). RSPICE orders SCCs by Tarjan's algorithm and simulates ordered SCCs one by one. DCCBs are basic cells in RSPICE and any DCCB can be mapped into one or more sub-circuit primitives. In order to calculate the transient response of these primitives analytically, RSPICE approximates the input signals of the primitive by piecewise linear functions. To compromise the simulation accuracy and run time, partial waveform and partial time convergent (PWPTC) combined with dynamic windowing technique is applied to simulate SCCs. Other key issues of RSPICE, such as circuit partition, pass-transistor and floating-capacitor processing, simulation-flow control and waveform modification are also discussed in detail. Compared with HSPICE , the simulation result of RSPICE is very accurate with an error less than 3%, but the speed is 1-2 orders over HSPICE.

This paper proposes a hardware/software cosynthesis system for digital signal processor cores and a hardware/software partitioning algorithm which is one of the key issues for the system. The target processor has a VLIW-type core which can be composed of a processor kernel, multiple data memory buses (X-bus and Y-bus), hardware loop units, addressing units, and multiple functional units. The processor kernel includes five pipeline stages (RISC-type kernel) or three pipeline stages (DSP-type kernel). Given an application program written in the C language and a set of application data, the system synthesizes a processor core by selecting an appropriate kernel (RISC-type or DSP-type kernel) and required hardware units according to the application program/data and the hardware costs. The system also generates the object code for the application program and a software environment (compiler and simulator) for the processor core. The experimental results demonstrate that the system synthesizes processor cores effectively according to the features of an application program and the synthesized processor cores execute most application programs with the minimum number of clock cycles compared with several existing processors.

A parallel detailed router based on the area division is one of important tools to overcome the increase of CPU time required for routing of a very large multilayer SOG. In order to conduct routing in each divided area independently, fictitious terminals are introduced on the border of each divided area, and routes connected to the fictitious terminals are concatenated to complete the final detailed routes. In this paper, we consider a problem how to position such fictitious terminals on borders, so as to make each detailed routing in a divided area easy. We formulate this problem as a minimum cost assignment problem, and propose an iterative improvement algorithm. We also give some experimental results which indicate the effectiveness of the algorithm.

Given a Petri net N=(P, T, E), a siphon is a set S of places such that the set of input transitions to S is included in the set of output transitions from S. Concerning extraction of one or more minimal siphons containing a given specified set Q of places, the paper shows several results on polynomial time solvability and NP-completeness, mainly for the case |Q| 1.

This paper describes the effectiveness of compact semiconductor optical amplifiers (SOAs) in the photonic transport system (PTS). Such amplifiers are small enough to permit high-density packaging. SOAs, having unsaturated signal gain of 10 dB and saturation output power of 10 dBm, can improve the Q-value by 3 over the SOA input power range of 10 dB. Within this range, the signal transport distance can be expanded from 360 km to 600 km by placing SOAs on individual optical channels in a PTS even though the amplified spontaneous emission (ASE) generated by individual SOAs is combined with the optical signals and delivered to the same output fiber. This result indicates that it is useful to employ compact SOAs in the PTS for enlarging the distances between nodes.

The recording of electrocardiogram (ECG) signals for the purpose of finding arrhythmias takes 24 hours. Generally speaking, changes in R-R intervals are used to detect arrhythmias. Our purpose is to develop an algorithm which efficiently detects R-R intervals. This system uses the R-wave position to calculate R-R intervals and then detects any arrhythmias. The algorithm searches for only the short time duration estimated from the most recent R-wave position in order to detect the next R-wave efficiently. We call this duration a WINDOW. A WINDOW is decided according to a proposed search algorithm so that the next R-wave can be expected in the WINDOW. In a case in which an S-wave is enhanced for some reason such as the manner in which the electrodes are installed in the system, the S-wave positions are taken to calculate the peak intervals instead of the R-wave. However, baseline wander and noise contained in the ECG signal have a deterrent effect on the accuracy with which the R-wave or the S-wave position is determined. In order to improve detection, the ECG signal is preprocessed using a Band-Pass Filter (BPF) which is composed of simple Cascaded Integrator Comb (CIC) filters. The American Heart Association (AHA) database was used in the simulation with the proposed algorithm. Accurate detection of the R-wave position was achieved in 99% of cases and efficient extraction of R-R intervals was possible.

This paper presents a performance evaluation of NAK-based reliable multicast communication protocols operating in an environment where end-to-end delay are heterogeneous. In the case of heterogeneous delay, performance of a timer-based retransmission control scheme may become worse. We show that a counter-based retransmission control scheme works well in the case of heterogeneous transmission delay. We also compare two NAK-based protocols and show that a NAK-multicasting protocol outperforms a NAK-unicasting protocol from the viewpoint of scalability even when delays are heterogeneous.

Optical Code Division Multiple Access (OCD- MA) has been emerging as an attractive scheme in fiber optic communication systems as well as in space communication systems in past few years. In OCDMA systems, M-ary Pulse Position Modulation (PPM), has been regarded as an efficient signalling format which has the capability to reduce the channel interference caused by the other users and also to increase the number of simultaneous users. We apply error control coding to improve the system performance of pulse position modulated OCDMA (PPM/OCDMA) systems and this paper investigates the performance of M-ary PPM/OCDMA systems with M-ary convolutional coding. Dual-k code is used as the M-ary convolutional code and Optical Orthogonal Codes with the maximum cross correlation value of 1 and 2 are employed as the signature sequences. We derive an expression for the bit error probability of the new system and show that combining M-ary convolutional coding and M-ary PPM results in an improved error performance. Also it is shown that the number of simultaneous users can be significantly increased with the proposed system compared to the uncoded PPM/OCDMA system with the same bit error probability and with the same information bit rate. We also analyze the system with binary convolutional coding and a comparison with the proposed system is given.

Human visual system can perceive 3-D structure of an object by binocular disparity, gradient of illumination (shading), occlusion, textures, perspective and so forth. Among them, binocular disparity seems to be the essentially important cues for the 3-D space perception and it is used widely for displaying 3-D visual circumstances such as in VR (virtual reality) system or 3-D TV. Visual illusions seem to be one of the phenomena which are purely reflecting the mechanism of human visual system. In the recent several years, the authors found several new types of 3-D visual illusions with binocular viewing. Entire 3-D illusory object including volume perception, transparency, dynamic illusions can be perceived only from the visual stimuli of disparity given by some inducing objects arranged with suitable relations. In this report, the authors introduced these newly found visual illusions and made some considerations on the human visual mechanism of 3-D perception and on their exploitation for new effective techniques in 3-D display. They introduced especially on the visual effect in two kinds of arrangement with occlusion and sustaining relationship between the illusory object and inducing objects. In the former case, the inducing objects which provide the stimuli were named as occlusion cues and classified into two types: contour occlusion cues and bulky occlusion cues. In the later case, those inducing objects were named as sustaining cues and a 3-D fully transparent illusory object was perceived. The perception was just like imagined from the scenes of the actions and positions of the pantomimists; then this phenomena was named as "Mime (Pantomime) Effect. " According to the positions of sustaining cues, they played different actions in this perception, and they are classified into three types: front sustaining cues, side sustaining cues and back sustaining cues. In addition, dynamic fusion and separation of volumetrical illusory objects were perceived when the visual stimuli were moving continuously between two structurally different conditions. Then the hysteresis was recognized in geometrical position between the fusion and separation. The authors believe that the occlusion cues and sustaining cues introduced in this paper could be effective clues for exploiting the new techniques for 3-D display.

In this paper, the use of optimal Karhunen-Loeve (KL) transform for quantization of speech line spectrum frequency (LSF) coefficients is studied. Both scalar quantizer (SQ) and vector quantizer (VQ) schemes are developed to encode efficiently the transform parameters after operating one or two-dimensional KL transform. Furthermore, the SQ schemes are also combined with entropy coding by using Huffman variable length coding (VLC). The basic idea in developing these schemes is utilizing the strong correlation of LSF parameters to reduce the bit rate for a given level of fidelity. Since the use of global statistics for generating the coding scheme may not be appropriate, we propose several adaptive KL transform systems (AKL) to encode the LSF parameters. The performance of all systems for different bit rates is investigated and adequate comparisons are made. It is shown that the proposed KL transform coding systems introduce as good as or better performance for both SQ and VQ in the examined bit rates compared to other methods in the field of LSF coding.

In this paper, we consider an integrated voice and data system over CDMA Slotted-ALOHA (CDMA S-ALOHA). We investigate its performance when multi-code CDMA (MC-CDMA) is applied as a multi-rate scheme to support users which require transmission with different bit rates. Two different classes of data users are transmitted together with voice. Performance measurement is obtained in respect of throughput for data and outage probability for voice. Moreover, we consider the Modified Channel Load Sensing Protocol (MCLSP) as a traffic control to improve the throughput of data. As a result, we show that the MC-CDMA technique is an effective one to obtain good throughput for data users at an acceptable voice outage probability. Furthermore, we show that with MCLSP, the throughput of data can be improved to reach a constant value even at a high offered load of data users.

Dynamical theory of cellular automata on groups is developed. Main results are non-Euclidean extensions of Sato and Honda's results on the dynamics of Euclidean cellular automata. The notion of the period of a configuration is redefined in a more group theoretical way. The notion of a co-finite configuration substitutes the notion of a periodic configuration, where the new term is given to it to reflect and emphasize the importance of finiteness involved. With these extended or substituted notions, the relations among period preservablity, injectivity, and Poisson stability of parallel maps are established. Residually finite groups are shown to give a nice topological property that co-finite configurations are dense in the configuration space.

In order to improve the efficiency of the feature extraction of backpropagation (BP) learning in layered neural networks, model switching for changing the function model without altering the map is proposed. Model switching involves map preserving reduction of units by channel fusion, or addition of units by channel installation. For reducing the model size by channel fusion, two criteria for detection of the redundant channels are addressed, and the local link weight compensations for map preservation are formulated. The upper limits of the discrepancies between the maps of the switched models are derived for use as the unified criterion in selecting the switching model candidate. In the experiments, model switching is used during the BP training of a layered network model for image texture classification, to aid its inefficiency of feature extraction. The results showed that fusion and re-installation of redundant channels, weight compensations on channel fusion for map preservation, and the use of the unified criterion for model selection are all effective for improved generalization ability and quick learning. Further, the possibility of using model switching for concurrent optimization of the model and the map will be discussed.

This paper demonstrates the necessity of special handling mechanisms for type (or sort) information when learning logic programs on the basis of background knowledge that includes type hierarchy. We have developed a novel relational learner RHB, which incorporates special operations to handle the computing of the least general generalization (lgg) of examples and the code length of logic programs with types. It is possible for previous learners, such as FOIL, GOLEM and Progol, to generate logic programs that include type information represented as is_a relations. However, this expedient has two problems: one in the computation of the code length and the other in the performance. We will illustrate that simply adding is_a relations to background knowledge as ordinary literals causes a problem in computing the code length of logic programs with is_a literals. Experimental results on artificial data show that the learning speed of FOIL exponentially slows as the number of types in the background knowledge increases. The hypotheses generated by GOLEM are about 30% less accurate than those of RHB. Furthermore, Progol is two times slower than RHB. Compared to the three learners, RHB can efficiently handle about 3000 is_a relations while still achieving a high accuracy. This indicates that type information should be specially handled when learning logic programs with types.