A numerical model of thin-film transistors for circuit simulation has been developed. This model utilizes three schemes. First, the spline interpolation with transformation by y=x+log(x) achieves excellent preciseness for both on-current and off-current simultaneously. Second, the square polynomial supplement solves an anomaly near the points where drain voltage equal to zero. Third, the linear extrapolation achieves continuities of the current and its derivatives as a function of voltages out of the area where the spline interpolation is performed, and improves convergence during circuit simulation.

We propose and demonstrate a novel method to measure the polarization mode dispersion (PMD) of optical devices. The device under test (DUT) is installed in a fiber laser cavity which can operate at multiwavelength. PMD can be evaluated by the wavelength spacing of the multiwavelength laser output spectrum. In our method, the maximum extrema wavelength is easier to be identified than in the conventional fixed-analyzer (FA) method. We measure the PMD of polarization maintaining fibers (PMFs) and the ITU-T round robin KDD samples.

This paper describes a rhythm pattern accuracy diagnosis system based on the rhythm pattern matching algorithm and a diagnosis feedback method by employing the SVM technique. A beat rhythm pattern is recorded by a PC and analyzed with an algorithm including cluster-analysis-based pattern matching. Rhythm performance is represented by a performance feature vector, which features note length deviation, note length instability, and tempo instability. The performance feature vector is effective for objectively evaluating the accuracy of rhythm patterns objectively. In addition, this system has the music experts' knowledge base, which is calculated from the performance feature vectors associated with the experts' subjective evaluation by listening to the performance. The system generates both an objective measuring report, and experts' comments for learners. Reproductivity of experts' comments is statistically indicated to be excellent for eight rhythm patterns, two tempo levels, and eight users. Reliability of experts' comments are also described considering the threshold of the decision function of SVM. Subjective evaluation of the system is carried out by fifteen users by a questionnaire using the SD method. As a result of factor analysis for the sixteen questions, four factors named "Audio-visual representation," "User-friendliness," "Reliability," and "Window representation," are extracted. Users' four factor scores indicate that the system is reliable and easy to use.

Jan and Tseng, in 1999, proposed two efficient digital signature schemes with subliminal channels. However, we show that a malicious subliminal receiver can forge subliminal messages that will be accepted by other subliminal receivers in Jan and Tseng's two schemes. Moreover, we also present a modification of Jan and Tseng's schemes to repair the security flaw.

This paper cryptanalyzes 128-bit block cipher Xenon, which was designed by Chang-Hyi Lee and has been recently proposed by Korea to ISO 18033-3, an ongoing activity in ISO/IEC JTC1/SC27/WG2 for standardizing block cipher algorithms. We study security of Xenon against linear cryptanalysis and show highly biased linear approximate paths that hold with probability 1/2 2-11 in the full 16-round Xenon. As a result, we can easily derive four-bit subkey information of Xenon using 223 known plaintexts with approximate success rate 84%. We also demonstrate a distinguishing attack of Xenon in a chosen plaintext scenario, which successfully reduces the number of required plaintext/ciphertext pairs of the attack. All these results were confirmed by computer experiments.

This paper describes truncated and impossible differentials of Feistel block ciphers with round functions of 2-layer SPN (Substitution and Permutation Network) transformation modules such as the 128-bit block cipher Camellia, which was proposed by NTT and Mitsubishi Electric Corporation. Our work improves on the best known truncated and impossible differentials, and has found a nontrivial 9-round truncated differential that may lead to a possible attack against a reduced-round version of Camellia without input/output whitening, FL or FL-1 (Camellia-NFL), in the chosen plain text scenario. Previously, only 6-round differentials were known that may suggest a possible attack of Camellia-NFL reduced to 8-rounds. We also show a nontrivial 7-round impossible differential, whereas only a 5-round impossible differential was previously known. We also consider the truncated differential of a reduced-round version of Camellia (Camellia-DS) whose round functions are composed of D-S (Diffusion and Substitution) transformation modules and without input/output whitening, FL or FL-1 (Camellia-DS-NFL), and show a nontrivial 9-round truncated differential, which may lead to a possible attack in the chosen plain text scenario. This truncated differential is effective for general Feistel structures with round functions composed of S-D (Substitution and Diffusion) or D-S transformation.

This paper proposes a 2-dimensional linear propagation prediction (LPP) in maximal ratio combining (MRC) transmitter diversity for orthogonal frequency division multiplexing (OFDM) time division multiple access--time division duplex (TDMA/TDD) systems in order to overcome the degradation of the transmission performance due to the fast fading or the TDD duration. In the proposed scheme, the downlink channel condition of each sub-channel is predicted by interpolating the uplink fading fluctuation with both the amplitude and phase, and the predicted downlink channel condition is used for the weighting factor to employ MRC transmitter diversity. Numerical results obtained by the computer simulation show that the proposed 2-dimensional LPP with the second-order Lagrangeis interpolation predicts the downlink channel condition accurately under the fast fading or the long TDD duration. Moreover, in such a condition, the proposed LPP provides far better performance than the conventional 1-dimensional LPP.

In the field of computer vision and computer graphics, Image-Based-Rendering (IBR) methods are often used to synthesize images from real scene. The image synthesis by IBR requires dense correct matching points in the images. However, IBR does not require 3D geometry reconstruction or camera calibration in Euclidean geometry. On the other hand, 3D reconstructed model can easily point out the occlusion in images. In this paper, we propose an approach to reconstruct 3D shape in a voxel space, which is named Projective Voxel Space (PVS). Since PVS is defined by projective geometry, it requires only weak calibration. PVS is determined by rectifications of the epipolar lines in three images. Three rectified images are orthogonal projected images of a scene in PVS, so processing about image projection is easy in PVS. In both PVS and Euclidean geometry, a point in an image is on a projection from a point on a surface of the object in the scene. Then the other image might have a correct matching point without occlusion, or no matching point because of occlusion. This is a kind of restriction about searching matching points or surface of the object. Taking advantage of simplicity of projection in PVS, the correlation values of points in images are computed, and the values are iteratively refined using the restriction described above. Finally, the shapes of the objects in the scene are acquired in PVS. The reconstructed shape in PVS does not have similarity to 3D shape in Euclidean geometry. However, it denotes consistent matching points in three images, and also indicates the existence of occluded points. Therefore, the reconstructed shape in PVS is sufficient for image synthesis by IBR.

The adaptive phase tracking scheme for orthogonal frequency division multiplexing (OFDM) signals can provide superior PER performance in channels with varying phase noise power. It is an effective technique for achieving high-rate and high quality wireless transmission. This paper proposes a new simple adaptive phase tracking scheme for OFDM signals in order to realize high-rate wireless local area networks (LANs). The proposed scheme measures the integrated phase rotation in order to appropriately set the properties of the FIR filter in the phase tracking circuits. This scheme uses the fact that the integrated phase rotation is correlated to the phase noise power. Assuming an RMS delay spread of 100 ns, computer simulations show that the proposed scheme offers superior required Eb/N0 performance (with regard to the phase noise power) compared to the conventional fixed-tap scheme, where the phase noise to signal power ratios are below -18 dB. It also offers excellent PER performance at the packet length of 1000 bytes unlike the conventional schemes, which suffer degraded PER performance.

This paper presents an effective approach for estimating of the load matching conditions for dielectric barrier discharge (DBD) load. By the simulation method proposed here, optimal working frequency and optimal applied voltage for driving of DBD load can be calculated. Estimation results for the DBD ultraviolet generation lamp as a load of series resonant inverter are presented here, together with their evaluations.

This paper proposes a space division multiplexed - coded orthogonal frequency division multiplexing (SDM-COFDM) scheme for multi-input multi-output (MIMO) based broadband wireless LANs. The proposed scheme reduces inter-channel interference in SDM transmission with a simple feed-forward canceller which multiplies the received symbols by the estimated propagation inverse matrix for each OFDM subcarrier. This paper proposes a new preamble pattern in order to improve power efficiency in the estimation of the propagation matrix. Moreover, the proposed likelihood-weighting scheme, which is based on signal-to-noise power ratio (SNR) of each OFDM subcarrier, improves the error correction performance of soft decision Viterbi decoding. Computer simulation shows that the proposed SDM-COFDM scheme with two transmitting/receiving antennas doubles the transmission rate without increasing the channel bandwidth and achieves almost the same PER performance as the conventional single-channel transmission in frequency selective fading environments. In particular, it achieves more than 100 Mbit/s per 20 MHz by using 64QAM with the coding rate of 3/4.

Many types of adaptive algorithms based on the MMSE criterion for co-channel interference suppression in DS/CDMA systems have been studied in great detail. However, these algorithms have such a problem that the training speed is greatly dropped under the strong near-far problem. In this paper, we propose and analyze an adaptive filter based on the Maximum Signal to Interference and Noise Ratio (MSINR) criterion, called adaptive MSINR filter. This filter is basically equivalent to the adaptive filter based on the MMSE criterion. However, due to the structual difference, the convergence speed is greatly improved. Specifically, the de-spreading vector in this filter is so renewed as to maximize the Signal to Interference and Noise Ratio (SINR) by minimizing the de-spread interference and noise power under the condition that the de-spread desired signal power keeps constant. So the proposed filter uses the estimated interference and noise signal calculated by subtracting the estimated desired signal from the received signal. It is just the reason why the adaptive MSINR filter shows remarkable convergence speed. And to satisfy the constant signal power condition, the projection matrix onto the orthogonal complement of the desired signal space is used for the de-spreading vector. For the proposed filter, we analyze the convergence modes and also investigate the de-spread interfernce and noise power for calculating the theoretical SINR curve. Then, we conduct some computer simulations in order to show the difference between this filter and the conventional one in terms of the SINR convergence speed. As the result, we confirm that the adaptive filter based on the MSINR criterion achieves significant progress in terms of the SINR convergence speed.

We investigated single flux quantum sinc filters with multistage decimation structure in order to realize high-speed sinc filter operation. Second- and third-order (k=2, 3) sinc filters with a decimation factor N=2 were designed and confirmed their proper operations. These sinc filters with N=2 are utilized as elementary circuit blocks of our multistage decimation sinc filters with N=2M, where M indicates the number of the stage of the decimation. As an example of the multistage decimation filter, we designed a k=2, N=4 sinc filter which was formed from a two-stage decimation structure using k=2, N=2 sinc filters, and confirmed its proper operation. The k=2, N=4 sinc filter consisted of 1372 Josephson junctions with the power consumption of 191 µW.

This paper describes fully integrated active guard band filters for suppressing the substrate coupling noise and their noise suppression effect measured by test chip experiments. The noise cancellation circuit of the active guard band filters simply consists of an inverter and a source follower. The substrate noise suppression effect was measured by using a test chip fabricated in a 0.18 µm CMOS triple-well process for system-on-a-chip. The noise with the filter was less than 5% of that without the filter and the noise suppression effect was observed from 1 MHz to 200 MHz by the statistical measurement of the voltage comparator. The noise suppression effect was also observed for actual digital switching noise produced by digital inverters. Configuration of the active guard band filter was investigated by simulation and it is shown that high and uniform noise suppression effect is achieved by placing the guard bands in the L-shape around the target triple-well area on the p-substrate.

This paper provides an overview on efficient algorithms for multicasting in optical networks supported by Wavelength Division Multiplexing (WDM) with limited wavelength conversion. We classify the multicast problems according to off-line and on-line in both reliable and unreliable networks. In each problem class, we present efficient algorithms for multicast and multiple multicast and show their performance. We also present efficient schemes for dynamic multicast group membership updating. We conclude the paper by showing possible extension of the presented algorithms for QoS provision.

In wireless communication systems, low-power metrics is becoming a burdensome problem in the portable terminal design, because of portability constraints. This paper presents design architecture of a low-power Digital Matched Filter (DMF) for the direct-sequence spread-spectrum communication system such as WCDMA or wireless LAN. The proposed approach for power savings focuses on the architecture of the reception registers and the correlation-calculating unit, which dissipate the majority of the power in a DMF. The main features are asynchronous latch clock generation for the reception registers, parallelism of correlation calculation operations and bit manipulation for chip-correlation operations. A DMF is designed in compliance with the WCDMA specifications incorporating the proposed techniques, and its properties are evaluated by computer simulations at the gate level using 0.18-µm CMOS standard cell array technology. As a result, the power consumption of the proposed DMF is estimated to be 9.3 mW (@15.6 MHz, 1.6 V), which is below 40% of the power consumed by a general DMF.

In this paper, we describe two approaches to optimize the Phase-Mode pipelined parallel multiplier. One of the approaches is reforming a data distribution for an AND array, which is named the hybrid structure. Another method is applying a Booth encoder as a substitute of the AND array in order to generate partial products. We design a 2-bit 2-bit Phase-Mode Booth encoder and test the circuit by the numerical simulations. The circuit consists of 21 ICF gates and operates correctly at a throughput of 37.0 GHz. The numbers of Josephson junctions and the pipelined stages in each scale of multipliers are reduced remarkably by using the encoder. According to our estimations, the Phase-Mode Booth encoder is the effective component to improve the performance of large-scale parallel multipliers.

Face recognition provides an important means for realizing a man-machine interface and security. This paper presents "Smartface," a PC-based face recognition system using a temporal image sequence. The face recognition engine of the system employs a robust facial parts detection method and a pattern recognition algorithm which is stable against variations of facial pose and expression. The functions of Smartface include (i) screensaver with face recognition, (ii) customization of PC environment, and (iii) real-time disguising, an entertainment application. The system is operable on a portable PC with a camera and is implemented only with software; no image processing hardware is required.

This paper proposes a new algorithm to achieve about two-times speedup of modular exponentiation which is implemented by Montgomery multiplication based on Residue Number Systems (RNS). In RNS Montgomery multiplication, its performance is determined by two base transformations dominantly. For the purpose of realizing parallel processing of these base transformations, i. e. "duplicate processing," we present two procedures of RNS Montgomery multiplication, in which RNS bases a and b are interchanged, and perform them alternately in modular exponentiation iteration. In an investigation of implementation, 1.87-times speedup has been obtained for 1024-bit modular multiplication. The proposed RNS Montgomery multiplication algorithm has an advantage in achieving the performance corresponding to that the upper limit of the number of parallel processing units is doubled.

A great deal of effort has been spent to develop strategies for allocation of resources in DS-CDMA systems in order to mitigate effects of interference between users. Here, the choice of spreading sequences and appropriate power allocation play a crucial role. When developing such strategies, CDMA system designers need to ensure that each user meets its quality-of-service requirement expressed in terms of the signal-to-interference+noise ratio. We say that a set of users is admissible in a CDMA system if one can assign sequences to the users and control their power so that all users meet their quality-of-service requirements. In [1], the problem of admissibility in a synchronous CDMA channel was solved. However, since the simplistic setting of perfect symbol synchronism rarely holds in practice, there is a strong need for investigating asynchronous CDMA channels. In this paper, we consider a K-user asynchronous CDMA channel with processing gain N and identical performance requirements for all users assuming chip synchronism. We solve the problem of admissibility of the users in such a channel if N K, and identify optimal sequences. We also show that constant power allocation is optimal. Results obtained in this paper give valuable insights into the limits of asynchronous CDMA systems.