We propose a novel short-range wireless communications technology that uses quasi-static electric fields; it enables data communication between devices separated by up to 10 cm via dielectric media at a speed of 10 Mbps. It is considered to be a secure wireless technology since communication area is restricted to below about 10 cm. To suppress electromagnetic radiation, we adopted a baseband transmission scheme in which the quasi-static electric field is directly modulated by 10 BASE-T data signals. Since the spectra of the data signals are concentrated to below 20 MHz, the amplitude of the electric field rapidly decreases outside the communication area. This contributes to enhancing security of the communications system. In this paper, we explain a basic principle of the short-range wireless communications technology. Since baseband data signals are carried by the quasi-static electric field, the quality of the communication is easily degraded by the existence of the earth ground. To isolate the communications system from the earth ground, we introduce a novel electro-optic sensor to receive the quasi-static electric field. With the electro-optic sensor, stable data communication is possible at 10 Mbps via dielectric materials, such as a wooden table.

A circuit technique to correct Vdd/PM distortion and improve efficiency as supply modulation of cascode class-E PAs has been proposed. The experimental result shows that the phase distortion can be improved from 20 degrees to 5 degrees. Moreover, a system co-simulation result demonstrated that the EVM can be improved from -17 dB to -19 dB.

Since scan testing is not based on the function of the circuit, but rather the structure, it is considered to be both a form of over testing and under testing. Moreover, it is important to test VLSIs using the given function. Since the functional specifications are described explicitly in the FSMs, high test quality is expected by performing logical fault testing and timing fault testing. This paper proposes a fault-dependent test generation method to detect specified fault models completely and to increase defect coverage as much as possible under the test length constraint. We present experimental results for MCNC'91 benchmark circuits to evaluate bridging fault coverage, transition fault coverage, and statistical delay quality level and to show the effectiveness of the proposed test generation method compared with a stuck-at fault-dependent test generation method.

We present a 60-GHz wireless through-repeater system based on self-heterodyne transmission scheme with the potential to optimize the carrier-to-interference and noise ratio (CINR) performance according to the transmission distance. The phase-noise degradation through a 60-GHz repeater link is not a serious concern when we employ the self-heterodyne transmission scheme. Multichannel interferences caused by third-order intermodulation distortions are efficiently suppressed by setting a high power ratio of LO carrier to RF signals in the self-heterodyne transmission. However, this high power ratio results in a lower carrier-to-noise ratio (CNR) and becomes unsuitable for improving link performance if the transmission distance increases. In order to facilitate a solution, we propose and make an embodiment of 60 GHz self-heterodyne transmitters that provide flexible control over the power ratio of LO to RF in a range of 10 dB ranges. With them, we successfully demonstrate terrestrial digital broadcasting signals on five channels and optimize their performance for wireless through-repeater applications.

A CMOS current-mode nth-switchable-root circuit composed of a compact logarithm circuit, a divide-by-n circuit, and a compact exponential circuit is proposed. The n can be selected from 5 values by three switches. Simulation results indicate that the compact nth-switchable-root circuit has a wide input-current range for relative errors less than 3%, low power dissipations below 630 µW, and high bandwidth over 330 MHz.

A number of inter-cell interference coordination schemes have been proposed to mitigate the inter-cell interference problem for orthogonal frequency division multiple access (OFDMA) systems and among them, partial frequency reuse is considered one of the most promising approaches. In this paper, we propose an inter-cell interference mitigation scheme for an OFDMA downlink system, which makes use of both partial frequency reuse and soft handover. The basic idea of this hybrid scheme is to dynamically select between a partial frequency reuse scheme and a soft handover scheme to provide better signal quality for cell edge users. Compared with the standard partial frequency reuse scheme, simulation results show that approximately one quarter of cell edge users can get improvements in signal quality as well as link spectral efficiency from using the proposed hybrid scheme. We also observe that by using our approach, there is a significant cell edge throughput gain over the standard partial frequency reuse scheme. Furthermore, based on a well defined data rate fairness criterion, we show that our method achieves higher overall system capacity as compared with the standard partial frequency reuse scheme.

Phase information on wave scattering is not unique and greatly depends on a choice of the origin of coordinates in the measurement system. The present paper argues that the center of scattering for polygonal cylinders should not be a geometrical center of the obstacle such as a center of gravity but be a position that acts as a balance to the electrostatic field effects from edge points. The position is exactly determined in terms of edge positions, edge parameters and lengths of side of polygons. A few examples are given to illustrate a difference from the center of geometry.

An analog circuit testing scheme is presented. The testing technique is a sinusoidal fault signature characterization, involving the measurement of DC offset, amplitude, frequency and phase shift, and the realization of two crossing level voltages. The testing system is an extension of the IEEE 1149.4 standard through the modification of an analog boundary module, affording functionalities for both on-chip testing capability, and accessibility to internal components for off-chip testing. A demonstrating circuit-under-test, a 4th-order Gm-C low-pass filter, and the proposed analog testing scheme are implemented in a physical level using 0.18-µm CMOS technology, and simulated using Hspice. Both catastrophic and parametric faults are potentially detectable at the minimum parameter variation of 0.5%. The fault coverage associated with CMOS transconductance operational amplifiers and capacitors are at 94.16% and 100%, respectively. This work offers the enhancement of standardizing test approach, which reduces the complexity of testing circuit and provides non-intrusive analog circuit testing.

Cooperative communication provides a new way of introducing spatial diversity to wireless systems. In order to increase the spectral efficiency of coded cooperative relaying system, the adaptive modulation technique is presented under Rayleigh fading channel in this paper. The source and relay adapt their modulation schemes based on the channel condition of all three links, i.e. source to relay, source to destination and relay to destination. Furthermore, since the available channel knowledge of the source to relay link is usually non-ideal at the destination in practice, a simplified estimation of this link quality is also given. Simulation demonstrates the effectiveness of the proposed technique in improving the data throughput.

Recently, a new multi-carrier CDMA (MC-CDMA) system with cyclic-shift orthogonal keying (CSOK) has been proposed and shown to be more spectral and power efficient than conventional MC-CDMA systems. In this paper, a novel extension called the multiplexed CSOK (MCSOK) MC-CDMA system is proposed to further increase the data rate while maintaining a low peak-to-average power ratio (PAPR). First, the data stream is divided into multiple parallel substreams that are mapped into QPSK-CSOK symbols in terms of cyclic shifted Chu sequences. Second, these sequences are repeated, modulated, summed, and placed on IFFT subcarriers, resulting in a constant-modulus multiplexed signal that preserves the desired orthogonality among substreams. The receiver performs frequency-domain equalization and uses efficient demultiplexing, despreading, and demapping schemes to detect the modulation symbols. Furthermore, an alternate MCSOK system configuration with high link quality is also presented. Simulations show that the proposed MCSOK system attains lower PAPR and BER, as compared to conventional MC-CDMA system using Walsh codes. Under a rich multipath environment, the high link quality configuration exhibits excellent performance with both diversity gain and MCSOK modulation gain.

A space-time and multipath diversity combining algorithm is presented for STBC single carrier block transmission system with two transmit and one receive antennas. The initial solution is achieved by an STBC-based frequency domain equalizer, and the multipath components in the received signal are decoupled by this initial solution and channel state information. Finally, STBC combining is carried out on each decoupled multipath component separately, and then the single carrier output branches are combined further using the maximal ratio combining (MRC) algorithm.

A method was developed for deriving the approximate global optimum of a nonlinear objective function with multiple local optimums. The objective function is expanded into a linear wave coefficient equation, so the problem of maximizing the objective function is reduced to that of maximizing a quadratic function with respect to the wave coefficients. Because a wave function expressed by the wave coefficients is used in the algorithm for maximizing the quadratic function, the algorithm is equivalent to a full search algorithm, i.e., one that searches in parallel for the global optimum in the whole domain of definition. Therefore, the global optimum is always derived. The method was evaluated for various objective functions, and computer simulation showed that a good approximation of the global optimum for each objective function can always be obtained.

In this paper, we propose a rapid model adaptation technique for emotional speech recognition which enables us to extract paralinguistic information as well as linguistic information contained in speech signals. This technique is based on style estimation and style adaptation using a multiple-regression HMM (MRHMM). In the MRHMM, the mean parameters of the output probability density function are controlled by a low-dimensional parameter vector, called a style vector, which corresponds to a set of the explanatory variables of the multiple regression. The recognition process consists of two stages. In the first stage, the style vector that represents the emotional expression category and the intensity of its expressiveness for the input speech is estimated on a sentence-by-sentence basis. Next, the acoustic models are adapted using the estimated style vector, and then standard HMM-based speech recognition is performed in the second stage. We assess the performance of the proposed technique in the recognition of simulated emotional speech uttered by both professional narrators and non-professional speakers.

Designing NURBS surfaces by manipulating control points directly requires too much trial and error for immersive VR applications. A more natural interface is provided by deforming a NURBS surface so that it passes through a given target point; and by repeating such deformations we can make the surface follow one or more target curves. These deformations can be achieved by modifying the pseudo-inverse matrix of the basis functions, but this matrix is often ill-conditioned. However, the application of a modified FE approach to the weights and control points provides controllable deformations, which are demonstrated across a range of example shapes.

This paper describes an adaptive feature extraction method that exploits category-specific information to overcome both image degradation and deformation in character recognition. When recognizing multiple fonts, geometric features such as directional information of strokes are often used but they are weak against the deformation and degradation that appear in videos or natural scenes. To tackle these problems, the proposed method estimates the degree of deformation and degradation of an input pattern by comparing the input pattern and the template of each category as category-specific information. This estimation enables us to compensate the aspect ratio associated with shape and the degradation in feature values and so obtain higher recognition accuracy. Recognition experiments using characters extracted from videos show that the proposed method is superior to the conventional alternatives in resisting deformation and degradation.

This paper is concerned with the estimation of radio communication distance when both the transmitter and receiver are arbitrarily distributed on a random rough surface such as desert, terrain, sea surface and so on. First, we simulate electromagnetic wave propagation along the rough surface by using the discrete ray tracing method (DRTM) proposed by authors recently. Second, we determine three parameters by conjugate gradient method (CGM) combined with the method of least-squares. Finally, we derive an analytical expression which can estimate the maximum communication distance when the input power of a transmitter and the minimum detectable electric intensity of a receiver are specified. Random rough surfaces are assumed to be Gaussian, pn-th order power law or exponential distributions.

In this letter, we propose a novel sparse channel estimation method for orthogonal frequency division multiplexing (OFDM) systems. The proposed method uses a discrete Fourier transform (DFT)-based technique for channel estimation and a sorted generalized Akaike information criterion (GAIC) to estimate the channel length and tap positions. Simulation results demonstrate that an improved channel estimation performance is obtained due to the reduction of signal space.

In this paper, a motion field representation algorithm based on directional edge information has been developed. This work is aiming at building an ego-motion detection system using dedicated VLSI chips developed for real time motion field generation at low powers . Directional edge maps are utilized instead of original gray-scale images to represent local features of an image and to detect the local motion component in a moving image sequence. Motion detection by edge histogram matching has drastically reduced the computational cost of block matching, while achieving a robust performance of the ego-motion detection system under dynamic illumination variation. Two kinds of feature vectors, the global motion vector and the component distribution vectors, are generated from a motion field at two different scales and perspectives. They are jointly utilized in the hierarchical classification scheme employing multiple-clue matching. As a result, the problems of motion ambiguity as well as motion field distortion caused by camera shaking during video capture have been resolved. The performance of the ego-motion detection system was evaluated under various circumstances, and the effectiveness of this work has been verified.

This letter describes the importance of transition regions, e.g. at phoneme boundaries, for automatic speaker recognition compared with using steady-state regions. Experimental results of automatic speaker identification tasks confirm that transition regions include the most speaker distinctive features. A possible reason for obtaining such results is described in view of articulation, in particular, the degree of freedom of articulators. These results are expected to provide useful information in designing an efficient automatic speaker recognition system.

We present a BPSK coherent optical wireless link in a multiple-beam, multiple-aperture configuration. The data are recovered using the signal obtained by the coherent addition of a set of maximum likelihood optical phase estimates and a select-largest stage. The proposal offers higher performance than the combining methods commonly used in optical wireless systems with diversity transmission and coherent detection.