In this paper, we present a new numerical method for the complex approximation of FIR digital filters. Our objective is to design FIR filters with equiripple magnitude and phase errors. The proposed method solves the least squares (LS) problem iteratively. At each iteration, the desired response is updated so as to have an equiripple error. The proposed methods do not require any time-consuming optimization procedure such as the quasi-Newton methods and converge to equiripple solutions quickly. We show some examples to illustrate the advantages of our proposed methods.

This paper provides a computational method to construct a Lyapunov function to prove a stability of hybrid automata that can have nonlinear vector fields. Algebraic inequalities and equations are formulated, which are solved via LMI optimization. Numerical examples are presented to illustrate the proposed method.

A low-power high-frequency sinusoidal quadrature oscillator is presented through a new RC technique using only CMOS current mirrors. The technique is relatively simple based on (1) internal capacitances of CMOS current mirrors and (2) a resistor of a CMOS current mirror for a negative resistance. Neither external capacitances nor inductances are required. As a particular example, a 2.4 GHz-0.4 mW, 0.325-fT, CMOS sinusoidal quadrature oscillator has been demonstrated. The power consumption is very low at approximately 0.4 mW. Total harmonic distortions (THD) are less than 0.3%. The oscillation frequency is current-tunable over a range of 540 MHz or 22%. The amplitude matching and the quadrature phase matching are better than 0.035 dB and 0.15, respectively. A figure of merit called a normalized carrier-to-noise ratio (CNRnorm) is 158.79 dBc/Hz at the 2 MHz offset from 2.46 GHz. Comparisons to other approaches are also presented.

This paper presents a model-based study of SET (Single-Electron-Transistor) logic gate family for synthesizing binary, MV (Multiple-Valued) and mixed-mode logic circuits. The use of SETs combined with MOS transistors allows compact realization of basic logic functions that exhibit periodic transfer characteristics. The operation of basic SET logic gates is successfully confirmed through SPICE circuit simulation based on the physical device model of SETs. The proposed SET logic gates are useful for implementing binary logic circuits, MV logic circuits and binary-MV mixed-mode logic circuits in a highly flexible manner. As an example, this paper describes design of various parallel counters for carry-propagation-free arithmetic, where MV signals are effectively used to achieve higher functionality with lower hardware complexity.

Next generation wireless networks are expected to support multimedia applications (audio phone, video on demand, video conference, file transfer, etc.). Multimedia applications make a great demand for bandwidth and impose stringent quality of service (QoS) requirements on the wireless networks. In order to provide mobile hosts with high QoS, efficient and better bandwidth reservation is necessary in multimedia wireless networks. This paper presents a novel hybrid dynamic-grouping bandwidth reservation scheme to support QoS guarantees in the next generation wireless networks. The proposed scheme is based on probabilistic resource estimation to provide QoS guarantees for multimedia traffic in cellular networks. We establish several reservation time-sections, called groups, according to the mobility information of mobile hosts (MHs) of each base station (BS). The amount of reserved bandwidth for each BS is dynamically adjusted for each reservation group. We use the hybrid dynamic-grouping bandwidth reservation scheme to decrease the connection-dropping probability (CDP) and connection-blocking probability (CBP), while increasing the bandwidth utilization. The simulation results show that the hybrid dynamic-grouping bandwidth reservation scheme provides less CDP and less CBP, and achieves high bandwidth utilization.

A finite impulse response (FIR) core based on the cascoded class AB SI technique is presented for low power wireless transceivers. Accomplished through both architectural and circuit developments, the filter's features include high speed, low power consumption, small silicon area and compatibility with standard CMOS process. For feasibility and performance assessments, an 8-tap 16 MS/s SI FIR filter with 5-bit coefficients and a 31-tap 80 MS/s SI matched filter (MF) for despreading task in future WCDMA receivers are demonstrated via simulations.

Direct digital frequency synthesizers (DDFS) provide fast frequency switching with high spectral purity and are widely used in modern spread spectrum wireless communication systems. ROM-based DDFS uses a ROM lookup table to store the amplitude of a sine wave. A large ROM table is required for high spectral purity. However, a larger ROM uses more area and consumes more power. Several ROM compression methods, including Sunderland technique based on simple trigonometric identities and quantization & error compensation techniques, have been reported. In this paper, we suggest several new techniques to reduce the ROM size. One new technique uses more number of hierarchical levels in ROM structures. Another technique uses simple interpolation techniques combined with hierarchical ROM structures. Experimental results show that the new proposed techniques can reduce the required ROM size up to 24%, when compared to that of a resent approach.

In this paper, we consider a blind channel estimation and equalization for single input multiple output (SIMO) channels. It is based on the one-step forward multichannel linear prediction error method. The derivation of the existing method is based on the noiseless assumption, however, we analyze the effects of additive noise at the output of the one-step forward multichannel linear prediction error filters. Moreover, we derive analytical results for the error in the blind channel estimation and equalization using linear prediction.

A high accuracy numerical technique based on the Finite Difference Time Domain (FDTD) method for a long dipole antenna analysis is presented. An improvement of the accuracy can be achieved without reducing the cell size by incorporating a quasi-static field behavior into the FDTD update equations. A closed form of the quasi-static field is obtained from a low frequency limit of a sinusoidal current distribution. The validity of the proposed algorithm is confirmed even when the length of dipole antenna is longer than half wavelength by comparing the results with the Method of Moment.

A new circuit technique based on pass-gate logic with dynamic supply-voltage and clock-frequency control is proposed for a low-power motion-vector detection VLSI processor. Since the pass-gate logic style has potential advantages that have small equivalent stray capacitance and small number of short-circuit paths, its circuit implementation makes it possible to reduce the power dissipation with maintaining high-speed switching capability. In case the calculation result is obtained on the way of calculation steps, additional power saving is also achieved by combining the pass-gate logic circuitry with a mechanism that dynamically scales down the supply voltage and the clock frequency while maintaining the calculation throughput. As a typical example, a sum of absolute differences (SAD) unit in a motion-vector detection VLSI processor is implemented and its efficiency in power saving is demonstrated.

Overall picture quality of a liquid crystal display (LCD) is changed by viewing conditions. An evaluation method of overall picture quality was proposed for LCDs. However, the estimation values calculated by the evaluation method differed from the subjective evaluation values, when viewing angle changed in the vertical direction. In this study, the coefficients of impairment in the evaluation equation were obtained by the multiple regression analysis using subjectively evaluated data. The evaluation method of overall picture quality was improved by weighting factors using these coefficients. As the result, the good estimation accuracy was obtained even if the viewing angle was changed both in the horizontal and vertical directions individually.

In this paper, we propose an optimal power control algorithm with fast convergence rate for CDMA cellular systems. The new power control algorithm is based on linear quadratic control theory (LQR). Using the state feedback control designed to minimize an objective function, each mobile performs a successful transmission with optimal power. Simulation results show a fast convergence rate to target SIR with less power consumption, and an augmented channel capacity through decreased outage probability.

Masqueraders who impersonate other users pose serious threat to computer security. Unfortunately, firewalls or misuse-based intrusion detection systems are generally ineffective in detecting masqueraders. Anomaly detection techniques have been proposed as a complementary approach to overcome such limitations. However, they are not accurate enough in detection, and the rate of false alarm is too high for the technique to be applied in practice. For example, recent empirical studies on masquerade detection using UNIX commands found the accuracy to be below 70%. In this research, we performed a comparative study to investigate the effectiveness of SVM (Support Vector Machine) technique using the same data set and configuration reported in the previous experiments. In order to improve accuracy of masquerade detection, we used command frequencies in sliding windows as feature sets. In addition, we chose to ignore commands commonly used by all the users and introduce the concept of voting engine. Though still imperfect, we were able to improve the accuracy of masquerade detection to 80.1% and 94.8%, whereas previous studies reported accuracy of 69.3% and 62.8% in the same configurations. This study convincingly demonstrates that SVM is useful as an anomaly detection technique and that there are several advantages SVM offers as a tool to detect masqueraders.

We have investigated the pretilt angle of liquid crystal (LC) molecules induced by photo-alignment films of polyimide (Azo-PI) containing azobenzene in the backbone structure. To generate finite pretilt angles, the Azo-PI film with inclined alignment of the backbone structure was prepared by a double light-exposure method. In this method the corresponding polyamic acid (Azo-PAA) film was first exposed to linearly polarized ultraviolet/visible (UV/VIS) light (LP-light) at normal incidence, and then oblique angle irradiation of unpolarized UV/VIS light (UP-light) was performed in the plane of incidence perpendicular to the polarization direction of the LP-light. Repeated photo-isomerization reactions of azobenzene induce the alignment of the Azo-PAA backbone structure. By thermally imidizing the photo-treated film we obtained a thermally and optically stable Azo-PI film. The orientational distribution of the Azo-PI backbone structure was determined by measuring the polarized infrared absorption spectra as a function of the sample rotation angle and the angle of incidence. The pretilt angle of LC molecules was determined by a crystal rotation method. We found that the average inclination angle of the Azo-PI backbone structure increased with the UP-light exposure. The pretilt angle of LC molecules, measured from the surface plane, also increased with the UP-light exposure. We succeeded in generating a pretilt angle of 3. The relation between the LC pretilt angle and the average inclination angle of the Azo-PI backbone structure is discussed.

The relation between resonant frequency of micromirror with vertical combdrives and applied voltage between the upper and lower comb teeth was analyzed. Resonant frequency of the micromirror was controlled by stiffness of the torsion hinge. Resonant frequency of the mirror was proportional to the applied voltage between the upper and lower comb teeth at the same tilt angle.

With iterative turbo decoding, the reliability of each bit in a frame is not same after some iterations. We propose novel bit-level hybrid automatic repeat request (HARQ) schemes with turbo codes in which only the unreliable bit and its neighboring bits are retransmitted based on the decoding reliability. The proposed bit-level HARQ schemes improve error performance compared with conventional HARQ schemes.

In this paper we propose an inter-block evaluation method to further reduce evaluation numbers in GA-based image halftoning technique. We design the algorithm to avoid noise in the fitness function by evolving all image blocks concurrently, exploiting the inter-block correlation, and sharing information between neighbor image blocks. The effectiveness of the method when the population and image block size are reduced, and the configuration of selection and genetic operators are investigated in detail. Simulation results show that the proposed method can remarkably reduce the entire evaluation numbers to generate high quality bi-level halftone images by suppressing noise around block boundaries.

The block-based fast transmission scheme, which is one of typical stored video delivery schemes, is reasonable in terms of its bandwidth efficiency and tolerance to the delay jitter, etc. However, it causes packet loss because of its burst data transmission method. Thus, we propose a slotted multicast scheme for MPEG video based on the block transmission scheme to maintain a higher quality and to include time constraints. We define two delivery units, the "GoPs Group" and the "Frame Type," on the basis of the MPEG characteristics with periodical NACK feedback from the clients. The former is tolerant to burst packet loss, and the latter gives priority to important frames. Our block multicast has two phases: a "Transmission Phase" and a "Retransmission Phase." In the former, a server multicasts a block, and in the latter, a server retransmits lost packets using multicast according to the proper delivery unit. We evaluate our proposal from some viewpoints with a computer simulation. We also measure the quality of the video reflected the result of a computer simulation. From these results, we confirm performance effectiveness of our proposal.

To improve the DS-CDMA signal transmission performance in a frequency-selective fading channel, the frequency-domain equalization (FDE) can be applied, in which simple one-tap equalization is carried out on each subcarrier component obtained by fast Fourier transform (FFT). Equalization weights for joint FDE and antenna diversity combining based on maximal ratio combining (MRC), zero-forcing (ZF), and minimum mean square error (MMSE) are derived. The conditional bit error rate (BER) is derived for the given set of channel gains in a frequency-selective multipath fading channel. The theoretical average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Performance comparison between DS- and multi-carrier (MC)-CDMA both using FDE is also presented.

An antenna with a wide bandwidth is required for ultra-wideband (UWB) system of the future. Several types of wideband antenna that cover the whole frequency range have been proposed. Since the UWB system would cover from 3.1 to 10.6 GHz, it is necessary to suppress the interference from other systems using some of this frequency band. This paper presents two types of novel planar monopole antenna: one consists of two connected rectangular plates and another one is an orthogonal type. The return loss characteristics, radiation pattern, and current distribution of these antennas were simulated by using the FDTD method. The proposed antennas had dual frequency and broad bandwidth characteristics at both resonant frequencies. The return loss level at the eliminated frequency between the resonant frequencies was almost 0 dB. The radiation patterns for the whole frequency range were almost omni-directional in the horizontal plane. The current distributions at each frequency were similar to that of a planar rectangular monopole. The radiation patterns thus were omni-directional in the horizontal plane at each resonant frequency. Therefore, the results showed that wide bandwidth characteristics could be achieved with such antennas.