In this paper, we propose a spatio-temporal equalizer for the space-time block coded transmission over the frequency selective fading channels with the presence of co-channel interference (CCI). The proposed equalizer, based on the tapped delay line adaptive array (TDLAA), performs signal equalization and CCI suppression simultaneously using the minimum mean square error (MMSE) method. It is to show that our scheme outperforms the previous two-stage combined adaptive antenna and delayed decision feedback sequence estimator (DDFSE) approach. We also show that performance can be further improved if the synchronization between the preceding and delayed paths is achieved.

In this letter, we propose the SNR estimator for multipath fading channels. We employ the least squares estimator for estimating the channel and estimate the SNR using the estimated noise variance. The SNR estimation can be used to adapt the demodulation algorithm to enhance its performance, as well as to provide the channel quality information. Simulation results show the performance of SNR estimator.

Ryu et al.'s recent paper proposed a multiple target angle-tracking algorithm without data association. This algorithm, however, shows degraded performance on evasive maneuvering targets, because the estimated signal subspace is degraded in the algorithm. In this paper, we propose a new algorithm where, VFF-PASTd (Variable Forgetting Factor PASTd) algorithm is applied to the Ryu's algorithm to effectively handle the evasive target tracking with better time-varying signal subspace.

In this paper, we propose a multiple-input multiple-output (MIMO) beamforming scheme for a multiuser system in frequency-selective fading channels. The maximum signal-to-noise and interference ratio (MSINR) is adopted as a criterion to determine the transmit and receive weight vectors. In order to maximize the output SINR over all users, two algorithms for base station are considered: the first algorithm is based on the receive weight vector optimization and the second algorithm is based on an iterative update of both transmit and receive weight vectors. Based on the result of single user MIMO beamforming, we analyze the interference channels cancellation ability of multiuser MIMO system. The first algorithm is a simple method and the second algorithm is a performative solution. Through computer simulations, it is shown that multiuser communication system is achievable using the proposed methods in frequency-selective fading condition.

In this paper, we propose an advanced location-based service that we call a direction-based service, which utilizes both the position and direction of a user. The direction-based service enables a user to point to an object of interest for command or investigation. We also describe the design, implementation and evaluations of a direction-based service system named Azim. With this system, the direction of the user can be obtained by a magnetic-based direction sensor. The sensor is also used for azimuth-based position estimation, in which a user's position is estimated by having the user point to and measure azimuths of several markers or objects whose positions are already known. Because this approach does not require any other accurate position sensors or positive beacons, it can be deployed cost-effectively. Also, because the measurements are naturally associated with some degree of error, the position is calculated as a probability distribution. The calculation considers the error of direction measurement and the pre-obtained field information such as obstacles and magnetic field disturbance, which enables robust position measurements even in geomagnetically disturbed environments. For wide-area use, the system also utilizes a wireless LAN to obtain rough position information by identifying base stations. We have implemented a prototype system for the proposed method and some applications for the direction-based services. Furthermore, we have conducted experiments both indoors and outdoors, and exemplified that positioning accuracy by the proposed method is precise enough for a direction-based service.

We have fabricated a multilayer structure for single flux quantum (SFQ) circuit application using a high-temperature superconductor (HTS). La0.2-Y0.9Ba1.9Cu3Ox (La-YBCO) base electrode layers were prepared by a dc or rf magnetron sputtering method. The reproducibility of film quality for dc-sputtered La-YBCO films was better than that for rf-sputtered films, and the dc sputtered films exhibited the average surface roughness Ra less than 1.0 nm and a Tc zero value of 88 K. By using the dc-sputtered La-YBCO films, a multilayer structure of SrSnO3/La-YBCO/SrSnO3/La-YBCO on MgO substrate with Ra below 2.0 nm was obtained. Interface-modified ramp-edge junctions with La0.2-Yb0.9Ba1.9Cu3Ox (La-YbBCO) counter electrodes have been fabricated by using this multilayer structure with dc-sputtered films. The fabricated junctions exhibited RSJ-type I-V characteristics with IcRn products of about 3 mV at 4.2 K. We also obtained a 1-σ Ic spread of 8% for a 1000-junction series-array. The sheet inductance values at 4.2 K for the base and counter electrodes on La-YBCO ground planes were 0.8 pH and 0.7 pH per square, respectively. Operation of several types of elementary SFQ circuits has been successfully demonstrated by using this multilayer structure.

This study was designed to evaluate localized muscular fatigue induced during mouse operation in a VDT task. Ten male undergraduates from 19 to 23 years old participated in the experiment. The subject performed a pointing task with a PC mouse for about 4 hours. The EMG measurements and psychological rating of fatigue were conducted before the experimental task and after each 30-minutes block during the experimental task. The changes in the Mean Power Frequency (MPF) and Percentage Maximum Voluntary Contraction (%MVC)-shift for the constant cumulative probability in the Amplitude Probability Distribution Function (APDF) with time were explored. The correspondence between the index (MPF or APDF) and the subjective rating of localized muscular fatigue was also examined. The performance was nearly constant across all blocks. The psychological rating of fatigue tended to increase with time. The MPF tended to increase with time, although the main effect of block (time) was not statistically significant. The %MVC-shift tended to increase with time. The correspondence with the perceived sensation of localized muscular fatigue was higher when using the %MVC-shift than when using the MPF. Based on the results, the effectiveness of the indexes used for evaluating localized muscular fatigue was discussed. The %MVC-shift obtained from the APDF was found to be a sensitive index of localized muscular fatigue and corresponded well with the subjective rating of localized muscular fatigue.

In the Multi Carrier (MC)-CDMA system, the frequency diversity gain is obtained by its being spread in the frequency domain. The frequency interleaving technique can improve the frequency diversity gain. In this paper, the bit error rate (BER) performance in the MC-CDMA system which adopts the frequency interleaving scheme in the frequency selective fading channel is evaluated by computer simulation. In this simulation, orthogonal restoration combining (ORC) and minimum mean square error combining (MMSEC) are considered as frequency equalization combining techniques. This paper shows that BER performance with the frequency interleaver is better than without it in various environments.

Multi-carrier code division multiplexing (MC-CDM) is one of promising multiplexing techniques for fourth-generation mobile downlink communications systems, where high data rate services should be provided even for high speed-cruising mobiles. For MC-CDM-based packet communication, a frequency scheduling method, which adaptively assigns different sub-carriers to different users, is proposed. This paper proposes a frequency scheduling method, which utilizes pre-assignmented subcarriers in the frequency domain for the MC-CDM scheme. Furthermore, the performance of the proposed system in frequency selective fading channels is compared with that of a no-scheduled MC-CDM scheme by computer simulation in both single- and multi-cell environments. From the results, it is found that the proposed system achieves better bit error rate performance than the no-scheduled MC-CDM scheme and can control quality of service (QoS) for active users.

The Generalized Max-Min Fairness policy (GMM) allocates in a fair way the available bandwidth among elastic calls by taking into account their minimum and maximum rate requirements. The GMM has been described in a five-step procedure, which has the advantage of an easy presentation, but does not come into details, as far as its computer implementation is concerned, and fails to describe the policy in a clear mathematical way. We propose a new algorithm for the GMM policy, in a clear mathematical way, based on Linear Programming (LP). The new algorithm is directly convertible into software. Numerical examples clarify our algorithm.

A new technique based on the auto-correlation function is described for the estimation of the Doppler spread in mobile communication systems. We first propose to divide a uncertainty region of Doppler spread into multiple frequency bins. Based on the given multiple bins the correlator compares the estimated value at a certain time index to the theoretical exact value and then decides which bin the Doppler spread is estimated in. The certain time index can be optimized to give the largest decision region among multiple bins. We derive the optimum time index algorithm to give the largest decision region for each bin based on Rayleigh fading channel. We also apply the same Doppler spread estimator to the Rician case with the slight transformation of the received signal. We show that the proposed technique is not affected significantly by the Rician factor and the SNR degradation with the reasonable number of samples for estimation which is not the case of other estimators given in the literature.

In this paper, we improve the performance analysis of the Rake receiver for the DS-CDMA forward link using long random spreading sequences (RSS's) by more accurately evaluating the correlation between the various interference terms. We also extend the analysis to the case of short (periodic) RSS. The accuracy of the expressions obtained in our analysis is verified by computer simulation. We show that for a given normalized spreading factor, the bit error rate (BER) performance of the Rake receiver is the same for BPSK and QPSK data modulation. We also show that when the channel delay spread is smaller than a data symbol duration, the CDMA receiver has similar BER performance for long and short RSS's. However, for large delay spread, the employment of short RSS's may result in severe performance degradation.

This paper proposes a novel auto-reset forward DC-DC converter with inductor-switching technique to obtain the high performance by means of zero voltage switching and the fast transient response at steep load variations. The performance of the forward converter is strongly depending on the transformer reset-method. The Auto-reset method is used to recover the energy stored in leakage inductances of the transformer to the power supply and makes sure the zero voltage switching. Furthermore fast transient response is achieved by applying the inductor-switching technique, which keeps the output voltage constant in case of heavy burden load changes. The design of the proposed concept is verified by experiment of 12 V input and 1.8 V/12 A output.

This paper presents a novel method to speed up neural network (NN) based face detection systems. NN-based face detection can be viewed as a classification and search problem. The proposed method formulates the face search problem as an integer nonlinear optimization problem (INLP) and expands the basic particle swarm optimization (PSO) to handle it. PSO works with a population of particles, each representing a subwindow in an input image. The subwindows are evaluated by how well they match a NN based face filter. A face is indicated when the filter response of the best particle is above a given threshold. Experiments on a set of 42 test images show the effectiveness of the proposed approach. Moreover, the effect of PSO parameter settings on the search performance was investigated.

Polynomial cancellation coding (PCC) was proposed to mitigate the sever inter-carrier-interference (ICI) in an orthogonal frequency division multiplexing (OFDM) system caused by frequency offset. In this paper, we consider the effectiveness of PCC under time-variant multi-path Rayleigh fading analytically and by simulations. We first consider an analytical expression of the signal-to-interference plus noise power ratio (SINR) and then derive an approximation of the bit-error-rate (BER) of the OFDM-PCC system under the assumption that ICI is well approximated by a white Gaussian noise. Since the bandwidth efficiency of OFDM-PCC is half of that of normal OFDM, we compare the BER performance of the scheme with the normal OFDM system of the same bit-rate when low, medium, and high level modulations are used. Our results show that OFDM-PCC performs well even for high modulation level under time-varying multi-path fading.

This letter derives and computes the detection probability for timing synchronization in an orthogonal frequency division multiplexing (OFDM) system encountered with a multipath Rayleigh fading channel. OFDM timing synchronization using constant amplitude zero auto-correlation (CAZAC) training symbols and correlation techniques is adopted. With this provision, we focus on the numerical analysis for OFDM timing synchronization scheme employing a preadvancement technique to reduce the inter-symbol interference (ISI). For measuring system performance, the sync detection performance derived in the considered system is presented in a multipath Rayleigh fading channel.

In downlink MC-CDMA, orthogonal variable spreading factor (OVSF) codes can be used to allow multirate communications while maintaining the orthogonality among the users with different data rates. In this paper, we point out that simple selection of the OVSF codes results in degraded performance. We show that this happens because simple code selection results in power concentration over certain consecutive subcarriers; severe power loss in the received signal occurs when these subcarriers experience a deep fade in a frequency selective fading channel. In addition, we show two effective techniques to avoid the performance degradation: random code selection and frequency interleaving; which technique provides a better performance depends on modulation level, code multiplexing order, and presence of channel coding.

The facility layout problem is one of the most fundamental quadratic assignment problems in operations research. In this paper, we present an improved genetic algorithm for solving the facility layout problem. In our computational model, we propose several improvements to the basic genetic procedures including conditional crossover and mutation. The performance of the proposed method is evaluated on some benchmark problems. Computational results showed that the improved genetic algorithm is capable of producing high-quality solutions.

Efficient extraction of interconnect parasitic parameters has become very important for present deep submicron designs. In this paper, the improved boundary element method (BEM) is presented for 3-D interconnect resistance extraction. The BEM is accelerated by the recently proposed quasi-multiple medium (QMM) technology, which quasi-cuts the calculated region to enlarge the sparsity of the overall coefficient matrix to solve. An un-average quasi-cutting scheme for QMM, advanced nonuniform element partition and technique of employing the linear element for some special surfaces are proposed. These improvements considerably condense the computational resource of the QMM-based BEM without loss of accuracy. Experiments on actual layout cases show that the presented method is several hundred to several thousand times faster than the well-known commercial software Raphael, while preserving the high accuracy.

Existence of a surface wave along the boundary between the semi-infinite materials, one of which is a free-space and the other is a material with either negative permeability or negative permittivity, is theoretically investigated. Surface waves exist in only limited combination of negative and positive signs of the material parameters. In addition, by analyzing the surface wave in a finite-thickness slab with negative permeability, its mode profile has been obtained for two different types of symmetry. From these results, the present paper predicts the possibility of a surface wave directional coupler based on a single slab transmission along its top and bottom surfaces.