There have been numerous studies on the enhancement of the noisy speech signal. In this paper, We propose a new speech enhancement method, that is, a DFF (Dissonant Frequency Filtering) scheme combined with NR (noise reduction) algorithm. The simulation results indicate that the proposed method provides a significant gain in perceptual quality compared with the conventional method. Therefore if the proposed enhancement scheme is used as a pre-filter, the output speech quality would be enhanced perceptually.

A high permittivity LSE-NRD guide was applied to a planar antenna at 60 GHz. Emphasis was placed on compatibility between the high permittivity LSE-NRD guide and the conventionally used low permittivity LSM-NRD guide. Performance of the transition between two such types of NRD guides was optimized by using an electromagnetic simulator and the validity was experimentally demonstrated. A simple radiator, consisting of a tapered high permittivity LSE-NRD guide was fabricated and evaluated as to radiation characteristics. Since the radiator has a broad radiation pattern, it was employed in a primary radiator of a two-dimensional parabolic reflector to develop a new type of folded planar antenna at 60 GHz. This planar antenna has a double-layered structure. In the upper layer, a metalized dielectric substrate with a slotted array is excited by a rectangular-shaped oversized waveguide, and in the lower layer, an offset parabolic reflector is fed by the radiator. Measurement showed the half-power beam width of the fabricated antenna to be 2.5 degrees in the E and H planes, respectively, and the gain to be 35.3 dBi, thus indicating that a good pencil beam antenna was successfully developed in this manner.

An image NRD guide-fed dielectric rod antenna, which is suitable for use at millimeter-wave frequencies, is presented in this paper. The antenna is composed of a linearly tapered dielectric rod connected to the image NRD guide. First, radiation characteristics of the dielectric rod antenna directly protruded from the end of the image NRD guide are investigated by FDTD analysis and measurements at 30 GHz band. For this case, the degradation of the radiation pattern and the decrease of the gain, which are due to the strong radiation from the guide-to-antenna discontinuity, are observed. In order to minimize this radiation and to realize reasonable radiation characteristics, a transition from the image NRD guide-to-rod antenna is proposed. A simple procedure to determine the optimum dimensions of the transition is described. This procedure is based on parametric study of the transition's dimensions, and is performed using FDTD analysis. Based on the results, the dielectric rod antenna having a length of 10 λ0 is designed, and its performance is analyzed and measured. The results show that radiation patterns with the half power beamwidth of 22, sidelobe level of -21 dB and reasonable gain of 18.5 dBi can be realized by employing the transition having the optimum dimensions.

A fast motion estimation algorithm is proposed, which performs a tree-structured motion vector search for variable blocks in the integer-pixel unit. The proposed method is based on the inequality of sum norms to find the best estimate of the motion vectors for variable blocks. The proposed motion estimation algorithm is applied to the Joint Video Team (JVT) encoder that performs variable-block motion estimation (ME) with quarter-pixel unit. In terms of computational complexity, the proposed motion estimation algorithm searches motion vectors about 10.7 times as fast as the spiral full search with early termination and 6.6 times as fast as the fast full search using the hierarchical sum of absolute difference (SAD), while the PSNR (peak signal-to-noise ratio) of the reconstructed image is slightly degraded.

In this letter, we propose joint frequency offset and SNR estimation technique. The frequency offset may degrade the system performance greatly by deleterious effect. The proposed frequency offset estimation technique estimates frequency offset by employing the interpolation technique in the frequency domain. Also we propose SNR estimation technique using the estimated frequency offset for FFT-based system. The SNR estimated by the receiver 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 frequency offset and SNR estimator.

In this letter we suggest sets of features to classify genres of web documents. Web documents are different from textual documents in that they contain URL and HTML tags within the pages. We introduce the features specific to web documents, which are extracted from URL and HTML tags. Experimental results enable us to evaluate their characteristics and performances. On the basis of the experimental results, we implement a user interface of a web search engine that presents documents grouped by genres.

An upgrade scheme using identical sending lights and local lights for optical amplifier systems based on homodyne detection is described. Optimum receiving loss for maximizing the SNR is analytically derived for the proposed configuration where the local taped lights are low level to avoid a sending power decrease. Derived formulas describing the optimum loss condition and the maximum SNR show that 10 Gbit/s systems can be cost effectively upgraded to 40 Gbit/s systems with the same repeater spacing.

An adaptive 4-state phase-frequency detector (PFD) for clock and data recovery (CDR) PLL of non return to zero (NRZ) data is presented. The PLL achieves false-lock free operation with rapid frequency-capture and wide bit-rate-capture range. The variable bit rate operation is achieved by adaptive delay control of data delay. Circuitry and overall architecture are described in detail. A z-Domain analysis is also presented.

This letter discusses the performance of online SNR estimation including fading parameter estimation for parallel combinatorial SS (PC/SS) systems. The PC/SS systems are partial-code-parallel multicode SS systems, which have high-rate data transmission capability. Nakagami-m distribution is assumed as fading channel model to cover a wide range of fading conditions. The SNR and fading parameter estimation considered in this letter is based on only a statistical ratio of correlator outputs at the receiver. Numerical results show that SNR estimation performance with fading parameter estimation is close to the one in the case of perfect fading parameter information, if the number of transmitting PN codes is less than a half of assigned PN codes.

In this paper, we perform some experiments to show that the quantization noise caused by low-bit-rate speech coding can be characterized as a white noise process. Then, the signal-to-quantization noise ratio of the decoded speech for a given bit-rate is estimated by observing the perceptual speech quality equivalent to the artificially generated noisy speech obtained by adding a white Gaussian noise source. This information is incorporated into the parameter tuning of a noise-robust compensation algorithm for speech recognition so that the compensation algorithm can be performed better under a range of the estimated SNRs. Finally, we apply the compensation algorithm to a connected digit string recognition system that utilizes speech signals decoded by the GSM adaptive multi-rate (AMR) speech coder. It is shown that the noise-robust compensation algorithm reduces word error rates by 15% or more at low bit-rate modes of the AMR speech coder.

We have developed a high-efficiency charge-pump power supply circuit with large output current capability for mobile equipment. However, during the commercialization phase, we found that the large inrush current of 270 mA at charge-pump circuit startup-time could cause problems. In this paper we analyze the mechanism that causes this inrush current, and we propose circuitry to reduce it. We show SPICE simulation and measurement results for our proposed circuitry that confirm its effectiveness. By incorporating this circuitry, startup-time inrush current was reduced to 30 mA.

Two fast quarter-pixel motion estimation algorithms using the integer motion vector (MV) already obtained by any fast motion estimation algorithm are proposed, which perform MV search only in half-pixel and quarter-pixel unit. The proposed algorithms search MV about 4-9 times as fast as the full search in quarter-pixel unit, while the PSNR is slightly degraded.

In this letter, a concise formula for the SNR degradation of OFDM caused by carrier frequency offset is derived by approximations over a shadowed two-path channel, which explicitly shows the sensitivity of SNR degradation to various parameters including the frequency offset. It is shown that, for small frequency offset, the SNR degradation is proportional to the square of the frequency offset and the square of the number of subcarriers. It is also shown that, if Es/N0 is reasonably large, the SNR degradation becomes insensitive to Es/N0, which is contrary to the case of the AWGN channel.

Power Line Communication (PLC) is very attractive for achieving high-rate in-home networks. Noise in power lines is modeled as a cyclostationary Gaussian process. In order to achieve reliable communication using power lines, effective measures including error control techniques need to be taken against this particular noise. This paper focuses its attention on an effect of turbo codes on PLC. We adopt two noise environments for examining the effect in terms of BER performance. The result of the examination provides that turbo codes have enough capability to limit the effect of the noise. It also provides that the effect depends on size of a channel interleaver. Since an effective SNR estimation scheme should be required to apply turbo codes to PLC, we also examine the effect of two SNR estimation schemes in terms of BER performance.

This paper newly proposes a hollow ferrite waveguide which consists of a microstrip line loaded on two ferrite slabs with adjacent air gap. Dispersion relation of magnetostatic surface wave in the waveguide is derived by the two dimensional analysis, and reciprocal behavior for parallel bias magnetic field and nonreciprocal behavior for antiparallel bias magnetic field are shown. Propagation characteristic of magnetostatic surface wave in the hollow ferrite waveguide are experimentally demonstrated under both parallel and antiparallel bias magnetic field directions. Strong nonreciprocal behavior in the hollow guide was found for case of antiparallel bias field configuration. These experimental results are mostly in agreement with the dispersion diagram. A nonreciprocal four port junction is demonstrated as an application of the hollow ferrite waveguide.

A technique for the design of circular- and racetrack-shaped NRD guide ring resonators was developed based on the mode coupling theory. Besides the operating mode, a parasitic mode is generated at curved sections of the resonator as a result of the mode conversion. Resonance of the NRD guide ring resonator is derived by characteristic equations of the coupled modes and then employed in making the design diagrams, which are useful for determining the dimensions of the ring resonators. It is shown that the discrepancy between the experimental results and previous theory can be resolved by using the present theory. Low loss, small-sized ring resonators with curvature radii of less than 5.3 mm were fabricated at 60 GHz and a band rejection performance of more than 30 dB was observed. Moreover, a procedure for the design of the channel dropping filter was developed and a 2-pole filter, which has great advantages such as a low insertion loss of 1.2 dB and a compact size smaller than that of a golf ball, was successfully developed by using two racetrack-shaped ring resonators.

TCP is a reliable transport protocol tuned to perform well in traditional wired networks, where most packet losses are due to congestion. In wireless networks, however, packet losses result from wireless link loss in addition to congestion loss. Thus, TCP suffers a significant degradation in performance over wireless networks because it does not distinguish wireless link loss from congestion loss. To overcome this problem, the explicit wireless loss notification (EWLN) scheme is proposed to explicitly inform wireless link loss to the TCP sender. Previous work to deploy EWLN often lacked explicit specification of the interplay between EWLN and link-layer protocols, including error recovery mechanisms. In addition, many systems, being based on computation demanding the functionality of agents at a base station, were designed for the scenario where information is accessed from a mobile station through a wireless-to-wired connection. In this paper, we present an EWLN scheme that deploys the information from the MAC layer and takes into account the interplay with the error recovery mechanism at the link layer. The scheme does not require different implementations for mobile terminals and base stations and hence can support efficient TCP-based data transmission over wired-to-wireless and wireless-to-wired connections as well as ad-hoc networks.

Beaulieu has proposed four signal-to-noise ratio (SNR) estimators for quadrature phase shift keying (QPSK) signaling in time domain. In this letter, we propose SNR estimators for QPSK signaling in frequency domain. A discrete Fourier transform (DFT) algorithm is used for the frequency domain analysis of the received signal. The frequency spectrum enables biased SNR estimation in the frequency domain. Circular convolution is used for robust and fast SNR estimation when the received signal exhibits a frequency offset. Simulation results show that the new estimators present good performance even when the received signal exhibits a large frequency offset.

To increase the discriminating ability of the speech feature based on linear predictive coding (LPC) and increase its noise robustness, an SNR-dependent arcsin transform is applied to the autocorrelation sequence (ACS) of each analysis frame in a speech signal. Moreover, each component in the ACS is also weighted by the normalized reciprocal of the average magnitude difference function (AMDF) for emphasizing its peak structure. Experimental results for the task of Mandarin digit recognition indicate that the LPC speech feature employing the proposed scheme is more robust than some widely used LPC-based approaches over a wide range of SNR values.

Transmission characteristics of a high permittivity NRD guide were investigated. A preferable operating mode of the high permittivity NRD guide was newly identified and the wide bandwidth and low loss nature of the millimeter-wave region were observed. Moreover, a technique for construction of a millimeter-wave antenna was developed based on the high permittivity NRD guide. The novelty of the present technique lies in the use of a simple radiator, which consists of a tapered dielectric strip of simple structure which has good compatibility with millimeter wave integrated circuits. Since this radiator has a broad radiation pattern, a new type of antenna compatible with millimeter-wave integrated circuits for marine radar use was fabricated by locating the radiator at the focal point of a cylindrical parabolic reflector. Suitable beam patterns with half-power beam widths of 4in the azimuth plane and 38in the elevation plane can be obtained at 35 GHz.