In this paper, a new explicit transformation method between Bezier and polynomial representation is proposed. An expression is given to approximate (n + 1) Bezier control points by another of (m + 1), and to perform simple and sufficiently good approximation without any additional transformation, such as Chebyshev polynomial. A criterion of reduction is then deduced in order to know if the given number of control points of a Bezier curve is reducible without error on the curve or not. Also an error estimation is given only in terms of control points. This method, unlike previous works, is more transparent because it is given in form of explicit expressions. Finally, we discuss some applications of this method to curve-fitting, order decreasing and increasing number of control points.

The reverse link performance of coherent multicode DS-CDMA [4], [5] under multipath Rayleigh fading environments is evaluated by computer simulation. It is demonstrated that the combined use of pilot symbol assisted (PSA)-coherent RAKE, channel coding, antenna diversity, and transmit power control is powerful in lowering the required signal energy per information bit-to-interference plus additive white Gaussian nose (AWGN) power spectrum density ratio (Eb/Io) which is an important parameter in determining the link capacity. It is also demonstrated that with slight performance degradation, high rate data transmission is realized by using multiple orthogonal spreading codes in parallel (orthogonal multicode transmission). Based on the simulated link performance, the reverse link cell capacity and link budget are also evaluated. It is found that parameter η=Io/No plays an important role in controlling the cell capacity and the maximum allowable path loss, where No is the AWGN power spectrum density.

It is shown that most of the binary images of generalized algebraic-geometric codes meet the Varshamov-Gilbert bound from the viewpoint of the average binary weight enumerator.

The importance sampling simulation technique has been exploited to obtain an accurate estimate for a very small probability which is not tractable by the ordinary Monte Carlo simulation. In this paper, we will investigate the simulation for a sample average of an output sequence from a Markov chain. The optimal simulation distribution will be characterized by the Kullback-Leibler divergence of Markov chains and geometric properties of the importance sampling simulation will be presented. As a result, an effective computation method for the optimal simulation distribution will be obtained.

Microcellular systems are suitable as personal mobile communication systems because of their high channel re-use efficiency and low transmission power. To implement a microcellular system, the antennas of base stations should be low enough, compared to the buildings around them, to reduce the interference to or from other base stations. In high-speed digital mobile radio communications, the time delay spread caused by multipath propagation is a significant factor in determining the maximum data transmission rate. In the case of a low-antenna-height microcellular system, the propagation characteristics rapidly change when the mobile terminal moves from a line-of-sight (LOS) location to a non-line-of-sight (NLOS) location. In this paper, the time dealy spread characteristics under LOS and NLOS conditions are examined using a geometrical street model which has a reflecting wall at one end of the street on which the base station is located. The RMS delay spreads are calculated using optical ray theory, taking into consideration the wedge diffraction on the street corner. If a reflecting wall exists, the RMS delay spread increases as the mobile terminal moves away from the base station under LOS conditions, or away from the street corner under NLOS conditions. The calculated results agree with the experimental results if measuring equipment noise is taken into consideration.

Viterbi decoding is known as a decoding scheme that can realize maximum likelihood decoding. However, it is impossible to continue it without re-synchronization even if only an insertion/deletion error occurs in a channel. In this paper, we show that Levenshtein distance is suitable for the metric of Viterbi decoding in a channel where not only symbol errors but also insertion/deletion errors occur under some conditions and we propose a kind of Viterbi decoding considering insertion/deletion errors.

There are many kinds of transmission lines such as uniform, nonuniform and nonlinear ones terminated by linear and/or nonlinear subnetworks. The nonuniform transmission lines are crucial in integrated circuits and printed circuit boards, because these circuits have complex geometries and layout between the multi layers, and most of the transmission lines possess nonuniform characteristics. On the other hand, the nonlinear transmission line have been focused in the fields of communication and instrumentation. Here, we present a new numerical method for analyzing nonuniform and nonlinear transmission lines with linear and/or nonlinear terminations. The waveforms at any points along the lines are described by the Fourier expansions. The partial differential equations representing the circuit are transformed into a set of ordinary differential equations at each frequency component, where for nonlinear transmission line, the perturbation technique is applied. The method is efficiently applied to weakly nonlinear transmission line. The nonuniform transmission lines terminated by a nonlinear subnetwork are analyzed by hybrid frequency-domain method. The stability for stiff circuit is improved by introducing compensation element. The efficiency of our method is illustrated by some examples.

C1 class smooth interpolation by a fuzzy reasoning for a small data set is proposed. The drafting technique of a human expert is implemented by using a set of fuzzy rules. The effectiveness of the present method is verified by computer simulations and by applications to the practical interpolation problem in a power system.

Recently, the high-speed data transmission techniques that have been developed for communication systems have in turn necessitated the implementation of high-speed error correction circuits. Parallel processing has been found to be an effective method of speeding up operarions, since the maximum achievable clock frequency is generally bounded by the physical constraints of the circuit. This paper presents a parallel encoder and decoder architecture which can be applied to both binary and nonbinary cyclic codes. The architecture allows H symbols to be processed in parallel, where H is an arbitrary integer, although its hardware complexity is not proportional to the number of parallel symbols H. As an example, we investigate hardware complexity for a Reed-Solomon code and a binary BCH code. It is shown that both the hardware complexity and the delay for a parallel circuit is much less than that with the parallel operation of H conventional circuits. Although the only problem with this parallel architecture is that the encoder's critical path length increases with H, the proposed architecture is more efficient than a setup using H conventional circuits for high data rate applications. It is also suggested that a parallel Reed-Solomon encoder and decoder, which can keep up with optical transmission rates, i.e., several giga bits/sec, could be implemented on one LSI chip using current CMOS technology.

In this paper we will propose a deterministic approach to model the radio wave propagation channels in large empty buildings. This technique applies the modified SBR method to find equivalent sources (images) in each launched triangular ray tube, and sums the receiving amplitude contributed by all images coherently. In addition, vector effective antenna height (VEH) is introduced to consider the polarization coupling effect resulting from the multiple reflection inside the buildings. We verify this approach by comparing the numerical results in three canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high frequency radio propagation inside buildings where multiple reflection is dominant. Work reported in this paper has shown that propagation loss in large empty buildings can vary considerably according to the geometrical configurations of buildings and polarizations. This SBR/image method can be enhanced by including the wall penetration and wedge diffraction effects so that more complicated indoor environments with furniture will be handled. Additional considerations, such as buildings crowded with pedestrians are left for future studies.

Direct sequence code division multiple access (DS-CDMA) is a promising candidate for 3rd generation mobile communications systems. We recently proposed a coherent multicode DS-CDMA (CM-CDMA) scheme that uses pilot symbol-aided coherent RAKE, interference power measurement based transmit power control, orthogonal multicode transmission, and concatenated channel coding. We have implemented a CM-CDMA test-bed for a series of laboratory and field tests using the 2 GHz band. This paper describes the test-bed system and experimental results are presented. It is confirmed that pilot symbol-aided coherent RAKE can reduce the required signal energy per bit-to-interference plus background noise spectrum density ratio (Eb/Io) by 2-3 dB from that achievable with differential detection. Also shown is that by using both RAKE combining and SIR-based power control the transmit power of mobile stations can be significantly reduced. Measurement results show that the required Eb/Io degrades only slightly when 24 code-channels (768 kbps) are used since orthogonal Gold sequences are used as short spreading codes.

In this study, we analyze the system which simultaneously transmits spread-spectrum signals with different processing gains. The main purpose of this study is to give an analytical framework that describes the influence of the interfering signals with different processing gains. For this purpose, we define a crosscorrelation function between the spreading sequences with different code lengths, and discuss the effects of interaction between the signals. As the results, we show that the power of the interference component after despreading procedure, the power ratio of the desired to undesired components, and thus the bit error rate are not constant but vary symbol by symbol.

Throughput analysis of CDMA Unslotted ALOHA with channel load sensing protocol (CLSP) is presented in consideration of the effect of the access timing delay. The access timing delay is defined as the sum of the process time and the propagation time for the packet access control. As CLSP is the scheme to control packet generation by the channel state information from the hub station, the effect of the access timing delay is significant. In our analysis, we extend a continuous-time Markov chain model and queueing systems. As a result, we found degradations of the throughput performance due to the access timing delay. For the value of CLSP threshold, we show that it is smaller than the case without the access timing delay in order to achieve satisfactory throughput. Furthermore, for a large access timing delay, CLSP makes no sense and the throughput is worse than the system without employing CLSP.

BaSnO3 is proposed as a new insulating material with good surface coverage of the lower superconductor electrode for superconductor/insulator/superconductor (SIS) tunnel junctions made of high-Tc superconductor YBa2Cu3Ox (YBCO). This paper reports on investigation of the epitaxial nature of BaSnO3 on YBCO thin films and YBCO/BaSnO3 /YBCO trilayer formation that are grown in situ by reactive co-evaporation in oxygen radicals. Investigation was done by reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), and X-ray diffraction (XRD). these observations confirm that (001)-oriented YBCO and (100)-oriented BaSnO3 thin films with atomically smooth surfaces grow epitaxially on each other. In addition, cross-sectional transmission electron microscopy (TEM) observation reveals that an approximately 4-nm-thick layer of BaSnO3 perfectly covers the lower YBCO thin film surface steps to a height of 1 to 2 unit cells of YBCO. The zero-resistance critical temperature Tc zero of both the upper and the lower YBCO thin films is higher than about 86 K.

Resonant properties of resistance shunted tunnel junctions have been investigated using the RLCSJ model. We found that an increase in dc current resulted from an increase in impedance of the shunted tunnel junctions. The static and dynamic properties of the shunted tunnel junctions were described in detail by numerical simulations and experiments. The simulated and measured results showed good agreement in I-V characteristics. A Josephson array oscillator has been proposed using the resonant properties for increasing oscillator output impedance. We designed and fabricated the oscillator with 20 shunted tunnel junctions. The output power of the oscillator delivered to the load resistor was estimated to be about 0.5µW at 312 GHz.

Several two-dimensional largest common subpatterns (LCP) between pictures are defined and their computing methods are proposed. The time and space complexities of the computing methods are O(IJMN) to obtain the size of LCPs between a picture with IJ pixels and a picture with MN pixels. These LCPs can be used as similarity measures between pictures and can be applied to texture recognition and classification.

A pilot symbol-assisted coherent multistage interference canceller (PSA-COMSIC) using recursive channel estimation is proposed for DS-CDMA mobile radio cellular systems. In the proposed scheme, since the channel variation due to fading is recursively estimated at each interference canceling stage, the accuracy of channel estimation is successively improved. The bit error rate (BER) performances against average Eb/N0 (signal energy per bit-to-noise power spectral density ratio) and capacity in the isolated cell are investigated by computer simulations. The simulations demonstrate that the capacity using the PSA-COMSIC with recursive channel estimation is about 1.6 times higher than that of the conventional matched filter receiver with channel coding and bit-interleaving in the interference-limited environments.

In this paper we propose a class of byte-error-correcting codes derived from algebraic curves which is a generalization on the Reed-Solomon codes, and present their fast parallel decoding algorithm. Our algorithm can correct up to (m + b -θ)/2b byte-errors for the byte length b, where m + b -θ + 1dG for the Goppa designed distance dG. This decoding algorithm can be parallelized. In this algorithm, for our code over the finite field GF (q), the total complexity for finding byte-error locations is O (bt(t + q - 1)) with time complexity O (t(t + q - 1)) and space complexity O(b), and the total complexity for finding error values is O (bt(b + q - 1)) with time complexity O (b(b + q - 1)) and space complexity O (t), where t(m + b -θ)/2b. Our byte-error-correcting algorithm is superior to the conventional fast decoding algorithm for randomerrors in regard to the number of correcting byte-errors in several cases.

A method for the recognition of handprinted Thai characters input using an image scanner is presented. We use methods of edge detection and boundary contour tracing algorithms to extract loop structures from input characters. The number of loops and their locations are detected and used as information for rough classification. For fine classification, local feature analysis of Thai characters is presented to discriminate an output character from a group of similar characters. In this paper, four parts of the recognition system are presented: Preprocessing, single-character segmentation, loop structure extraction and character identification. Preprocessing consists of pattern binarization, noise reduction and slant normalization based on geometrical transformation for the forward (backward) slanted word. The method of single-character segmentation is applied during the recognition phase. Each character from an input word including the character line level information is subjected to the processes of edge detection, contour tracing and thinning to detect loop structures and to extract topological properties of strokes. The decision trees are constructed based on the obtained information about loops, end points of strokes and some local characteristics of Thai characters. The proposed system is implemented on a personal computer, and a high recognition rate is obtained for 1000 samples of handprinted Thai words from 20 subjects.

A new 19-channel SQUID magnetometer system has been developed for research use in order to measure the neuromagnetic fields originating from cortices of the human brain.The system could function for 6 days with a one-time supply of about 25 L of liquid helium. The system consists of Nb/Al-oxide/Nb SQUID sensors with 2nd-order gradiometers, tank circuits, readout electronics, a liquid helium dewar, a gantry, and a prefabricated shielded room. The gradiometers cover a circular area of 15 cm radius. We used fine stainless steel leads for electric connection between the sensors and room-temperature electronics with low thermal conduction in a low helium consumption dewar. The system could function for 6 days with a one-time supply of about 25L of liquid helium. The system can be thermally cycled for repeated measurements, with an intervening nonusage period at room temperature. The noise characteristics, for both the time and frequency domains, of all channels were measured. From an analysis of the voltage output at the phase-sensitive detector, the flux-origin noise which is generated by external sources was dominant in the white noise frequency. The power spectra of the noise field were below 10 fT/Hz1/2 at 10-100 Hz and below 18 fT/Hz1/2 at 1-10 Hz. Some other peaks of power line frequencies such as 50 Hz and 150 Hz were observed at several channels. Sound-evoked magnetic fields were measured from the temporal area of the head upon application of tone bursts. The evoked fields were recorded with the amplitude of about 250 fTpp. The isofield contours of the peak response showed that the measurement area is large enough to estimate current dipoles. It is confirmed that the system has the ability to measure magnetic fields from the human brain.