Closed-loop power control providing maximum capacity of the multicarrier channel with frequency selective Nakagami fading is investigated. Use of the famous Gallager channel capacity (water-filling) theorem with the assumption of limited transmitter power and independent fading in partial channels leads to the algorithm for their optimal power loading. Analytical expressions for the capacity of the multicarrier channel as a function of the number of its subchannels and the fading parameters are derived for the cases of Optimal Power Distribution (OPD) and Equal Power Distribution (EPD). The dependence of the capacity gain on the OPD system order, the fading depth and the average SNR due the optimal power control is obtained. Comparison of the power efficiencies of the systems with OPD and EPD is presented.

A multi-QoS scalable-distributed-arbitration (MSDA) ATM switch is described that supports both high- and low-priority traffic under the head-of-line-priority discipline. It uses crosspoint and transit buffers, each consisting of a high- and low-priority buffer. The buffers arbitrate in a distributed manner the selection of which cellsto transmit. The MSDA switch supports multiple QoS classes while still providing the scalability of a previously described single-QoS scalable-distributed-arbitration (SSDA) switch. A problem occurs when the delay-time-based cell-selection mechanism used in the SSDA switch is applied to the low-priority traffic: it cannot achieve fairness in terms of throughput. This problem is overcome by introducing a distributed-ring-arbiter-based cell-selection mechanism at each crosspoint for the low-priority traffic. The low-priority transit buffer at each crosspoint has virtual queues, one for each upper input port. Cells for the low-priority traffic are selected by distributed-ring arbitration among the low-priority crosspoint buffer and these virtual queues. For the high-priority traffic, the same delay-time-based cell-selection mechanism is used as in the SSDA switch. Simulations show that the MSDA switch ensures fairness interms of delay time for the high-priority traffic and ensures fairness in terms of throughput for the low-priority traffic.

Medium access control (MAC) protocol is one of the key components for providing quality of service (QoS) in wireless ATM (W-ATM) networks. In this paper, we propose a hierarchical scheduling scheme coupled with fair queueing algorithms with adaptive weights. This scheme is intended to be applicable to a TDMA/TDD based MAC protocol. Specifically, the performance of the fair-queueing algorithm using fixed weights and adaptive weights is evaluated and compared. Simulation results show that the proposed hierarchical fair-queueing scheduling with adaptive weights (HAW) can yield a lower cell transfer delay and a higher channel utilization while maintaining fairness among multiple users.

Muscle based face image synthesis is one of the most realistic approaches to the realization of a life-like agent in computers. A facial muscle model is composed of facial tissue elements and simulated muscles. In this model, forces are calculated effecting a facial tissue element by contraction of each muscle string, so the combination of each muscle contracting force decides a specific facial expression. This muscle parameter is determined on a trial and error basis by comparing the sample photograph and a generated image using our Muscle-Editor to generate a specific face image. In this paper, we propose the strategy of automatic estimation of facial muscle parameters from 2D markers'movements located on a face using a neural network. This corresponds to the non-realtime 3D facial motion capturing from 2D camera image under the physics based condition.

We propose a new sampling method for 2D and 3D implicit surfaces. The method is based on a stochastic process defined by the Langevin equation with a Gaussian random-force term. Our Langevin equation describes a stochastic-dynamical particle, which develops in time confined around the sampled implicit surface with small width. Its numerically generated solutions can be easily moved onto the surface strictly with very few iteration of the Newton correction. The method is robust in a sense that an arbitrary number of sample points can be obtained starting from one simple initial condition. It is because (1) the time development of the stochastic-dynamical particle does not terminate even when it reaches the sampled implicit surface, and (2) there is non-zero transition probability from one disconnected component to another. The method works very well for implicit surfaces which are complicated topologically, mathematically, and/or in shape. It also has some advantageous features in rendering 3D implicit surfaces. Many examples of applying our sampling method to real 2D and 3D implicit surfaces are presented.

The mathematical theory of bicomplex electromagnetic waves in two-dimensional scattering and diffraction problems is developed. The Vekua's integral expression for the two-dimensional fields valid only in the closed source-free region is generalized into the radiating field. The boundary-value problems for scattering and diffraction are formulated in the bicomplex space. The complex function of a single variable, which obeys the Cauchy-Riemann relations and thus expresses low-frequency aspects of the near field at a wedge of the scatterer, is connected with the radiating field by an integral operator having a suitable kernel. The behaviors of this complex function in the whole space are discussed together with those of the far-zone field or the amplitude of angular spectrum. The Hilbert's factorization scheme is used to find out a linear transformation from the far-zone field to the bicomplex-valued function of a single variable. This transformation is shown to be unique. The new integral expression for the field scattered by a thin metallic strip is also obtained.

The use of Internet for various business applications and resource sharing has grown tremendously over the last few years. Internet security has become an important issue for both academic and industrial sectors. Much related network security research has been conducted such as user authentication, data confidentiality, and data integrity. In some applications, a critical document can be divided into pieces and allocated in different locations over the Internet for security access concern. To access such an important document, one must reconstruct the divided pieces from different locations under the given Internet environment. In this paper, a probability model for reconstructing secret sharing and algorithms to perform share assignment are presented. Also, an evaluation algorithm to measure the probability of secret sharing reconstruction is proposed. Illustrative examples and simulation results are provided to demonstrate the applicability of our method.

This paper proposes applying fast transmit power control (TPC) to the forward link of a direct sequence-code division multi-access (DS-CDMA) cellular system. Orthogonal spreading is assumed at a base station transmitter and coherent RAKE combining is assumed at a mobile station receiver. In DS-CDMA cellular mobile radio, the multiple access interference (MAI) from other cells and background noise limit the forward link capacity. Therefore, to increase the link capacity, fast transmit power control (TPC) can be introduced, which is similar to that developed for the reverse link, i. e. , the transmit powers of forward link channels are independently raised or lowered according to the instantaneous signal-to-background noise plus interference ratios (SIR's) measured at mobile stations. Fast TPC is fast enough to track the multipath fading as well as slow variations in the distance-dependence path loss and shadowing. On the average, the transmit power is increased to a user closer to the cell edge so that the effects of both other-cell MAI and background noise can be reduced while it is decreased to a user closer to the cell center. The effect of the TPC parameters (TPC interval, TPC target value, TPC step size, etc) on the forward link capacity in single- and multi-cell environments is evaluated by computer simulation. It is shown that fast TPC can almost double the forward link capacity in a multi-cell environment.

The outage probability of a forward link DS-CDMA cellular system with fast transmit power control (TPC) based on signal-to-interference ratio (SIR) is investigated. The expression for SIR at the output of RAKE receiver is developed, and the outage probability is evaluated by using Monte Carlo simulation. We consider two kinds of channel models: random delay resolvable path model and tapped delay line model which are suitable models for a few distinct paths channel and highly frequency-selective-channel model, respectively. The outage probability of a system with fast TPC based on SIR is compared to that without fast TPC. The use of orthogonal spreading codes is compared to that of the random spreading codes in terms of outage probability. The effects of the maximum and minimum transmit powers and the dispersive loss of signal power on the outage probability are also investigated.

A novel electrical gating circuit is proposed for ultrafast applications in electronics. The circuit employs a two-conductor coupled line, and does not have any active devices such as transistors or diodes. Hence, the ultimate speed of the circuit is limited only by the cutoff frequency of the lines employed. The authors describe the circuit theory and discuss the results of experiments that involved ultrafast measurement using electro-optic sampling techniques. The latter suggests the potential of the circuit to achieve the gatings of at least 80-Gbit/s.

A support system for hepatectomy that allows segmentation of the liver interactively and directly on 3D images was developed. Intuitive 3D images of the liver and its vessels and tumors were drawn with an improved volume-rendering method. Regions supplied with blood by each branch were interactively identified. 3D segments were defined directly on the images using a mouse and excisions were estimated from these interactive inputs.

We obtain the upper bound of the average bit error probability of direct-sequence code division multiple access (DS-CDMA) with trellis coded modulation (TCM) in Nakagami fading multipath channel. We show the effects of the length of the shortest error event path for the bit error rate (BER) performance of TCM for different diversity orders and fading parameters. We assume all diversity branch fadings and noises are statistically independent.

This paper is intended as an investigation of scientific discoveries from a philosophical point of view. In the first half of this century, most of philosophers rather concentrated on the logical analysis of science and set the problem of discovery aside. Logical positivists distinguished a context of discovery from a context of justification and excluded the former from their analysis of scientific theories. Although Popper criticized their inductivism and suggested methodological falsificationism, he also left the elucidation of discovery to psychological inquiries. The problem of scientific discovery was proprely treated for the first time by the "New Philosophy of Science" school in the 1960's. Hanson reevaluated the method of "retroduction" on the basis of Peirce's logical theory and analysed Kepler's astronomical discovery in detail as a typical application of it. Kuhn's theory of paradigm located discoveries in the context of scientific revolutions. Moreover, he paid attention to the function of metaphor in scientific discoveries. Metaphorical use of existing terms and concepts to overcome theoretical difficulties often plays a decisive role in developping new ideas. In the period of scientific revolution, theoretical metaphors can open up new horizons of scientific research by way of juxtapositions of heterogeneous concepts. To explicate such a complicated situation we need the "rhetoric" of science rather than the "logic" of science.

Multimedia mobile communication systems are expected to be realized in the near future. In such systems, multipath fading can cause severe degradations of the quality of the communications due to its wide bandwidth, especially in urban areas. Adaptive array antennas can be attractive solution for overcoming the multipath fading. Suppression can be achieved with the adaptive array by cophasing and combining multipath signals in the space and time domain. On the other hand, the concept of software antenna has been proposed. The software antenna recognizes radiowave environments and appropriately reconfigures itself for the signal processing required by the recognized environment. Efficient implementations can be expected if these functions are realized by the software. In this paper, we propose two types of the adaptive array systems which is reconfigurable depending on the radiowave environment as a realization of the concept of the software antenna. They recognize the environment by using the eigenvalue decomposition of space domain correlation matrices and reconfigure their structures of the signal processing. The principle and performance are examined by theoretical means and through computer simulations.

This paper examines fairness of service in the up-link of CDMA cellular slotted-ALOHA packet communication systems with site diversity reception. Site diversity rescues the packets originating mainly from near the edge of the cells, whereas packets originating near the base stations can not obtain the benefits of diversity reception. This situation causes an unfairness in packet reception that depends on location of the mobile station. Two transmission control schemes for reducing this unfairness are proposed. In the first scheme, mobile stations control the target received power for the open-loop power control based on the reception level of the pilot signals of the surrounding base stations. In the second, mobile stations control transmit permission probability. Successful packet reception rate, fairness coefficient and throughput performance are evaluated in fading environments with imperfect power control. Computer simulation shows that both schemes improve service fairness for all mobile stations and throughput performances. A performance comparison between the two schemes concludes that transmission power control outperforms transmit permission probability control as a simple technique for maintaining fairness of services.

As VLSI technology has developed, the interest in implementing an entire or significant part of a parallel computer system using wafer scale integration is growing. The major problem for the case is the possibility of drastically low yield and/or reliability of the system if there is no strategy for coping with such situations. Various strategies to restructure the faulty physical system into the fault-free target logical system are described in the literature [1]-[5]. In this paper, we propose an efficient approximate method which can reconstruct the 1 1/2 track-switch mesh arrays with faulty PEs using hardware as well as software. A logical circuit added to each PE and a network connecting the circuits are used to decide spare PEs which compensate for faulty PEs. The hardware compexity of each circuit is much less than that of a PE where the size of each additional circuit is independent of array sizes and constant. By using the exclusive hardware scheme, a built-in self-reconfigurable system without using a host computer is realizable and the time for reconfiguring arrays becomes very short. The simulation result of the performance of the method shows that the reconstructing efficiency of our algorithm is a little less than those of the exaustive and Shigei's ones [6] and [7], but much better than that of the neural one [3]. We also compare the time complexities of reconstructions by hardware as well as software, and the hardware complexity in terms of the number of gates in the logical circuit added to each PE among the other methods.

In our previous paper we presented a path-tracing method of multiple gate delay fault diagnosis in combinational circuits. In this paper, we propose an improved method that uses the ambiguous delay model. This delay model makes provision for parameter variations in the manufacturing process of ICs. For the effectiveness of the current method, we propose a timed 8-valued simulation and some new diagnostic rules. Furthermore, we introduce a preparatory process that speeds up diagnosis. Also, at the end of diagnosis, additional information from the results of the preparatory process makes it possible to distinguish between non-existent faults and undiagnosed faults.

In this paper, we show two process allocation schemes to tolerate multiple faults when the primary-backup replication method is used. The first scheme, called multiple backup scheme, is running multiple backup processes for each process to tolerate multiple faults. The second scheme, called regenerative backup scheme, is running only one backup process for each process, but re-generates backup processes for processes that do not have a backup process after a fault occurrence to keep the primary-backup process pair available. In both schemes, we propose heuristic process allocation methods for balancing loads in spite of the occurrence of faults. Then we evaluate and compare the performance of the proposed heuristic process allocation methods using simulation. Next, we analyze the reliability of two schemes based on their fault-tolerance capability. For the analysis of fault-tolerance capability, we find the degree of fault tolerance for each scheme. Then we find the reliability of each scheme using Markov chains. The comparison results of two schemes indicate that the regenerative single backup process allocation scheme is more suitable than the multiple backup allocation scheme.

The transmission quality in mobile wireless communications is affected by not only the thermal noise but also the multipass fading which changes drastically an amplitude and a phase of received signal. The paper proposes the theoretical and approximate methods for deriving an average bit error rate in DS-CDMA systems under the Rician fading environment on the assumption of the frequency non-selective fading, as parameters of the number of simultaneous access stations, the maximum Doppler frequency and so on. It is confirmed from the coincidence of theoretical and approximate results with simulation ones that the proposed approach is applicable to a variety of system parameters.

In this paper, we propose the introduction of space diversity techniques to the code acquisition of a direct-sequence spread-spectrum signal. In this scheme, both a transmitter and a receiver have multiple antennas and the signals corresponding to all the combinations of the transmitter and receiver antennas are combined at the acquisition circuit of the receiver. The performance is evaluated for an indoor packet radio communication system from the viewpoints of the average time for acquisition, the probability of success of acquisition, and the necessary preamble length. As the result, we show great performance improvements by the proposed scheme under slow and flat Rayleigh fading environment.