A new fast and reliable image objective quality evaluation technique is presented in this paper. The proposed method takes image structure into account and uses a low complexity homogeneity measure to evaluate the intensity uniformity of a local region based on high-pass operators. We experimented with monochrome images under different types of distortions. Experimental results indicate that the proposed method provides better consistency with the perceived image quality. It is suitable for real applications to control the processed image quality.

In this letter, we aim at the study of an OFDM system that employs adaptive modulation techniques to achieve efficient transmission service. In adaptive modulation techniques, a banded AM technique can reduce the number of adaptive modulation information bits and signaling overhead. We evaluate the banded AM technique and compare with Subcarrier AM technique. Moreover, to evaluate the channel condition, we apply the SNR estimation method. Furthermore, to increase the performance of OFDM system, frequency domain pre-equalization is applied. The simulation results have been shown that the OFDM system with adaptive schemes can achieve the efficient transmission for multi-media services.

This paper treats transmission characteristics of periodic structure of ferrite gyrator circuit with both theory and experiment, which is loaded into usual distributed constant line with and without lumped capacitor. Following three types of periodic structure of gyrator circuit are proposed: basic structure of periodic gyrator circuit, quasi-LH gyrator circuit with series capacitance loading, and quasi-LH gyrator circuit with parallel capacitance loading. Moreover, replacing the parallel capacitance with a resistance, a periodic structure of isolator circuit is proposed. Scattering parameters of gyrator circuit are derived with help of equivalent circuit model. Left handed transmission behavior of backward wave is discussed from dispersion curves. Experiments were undertaken using periodic structure of dielectric microstrip line and gyrator circuit fabricated on the ferrite substrate. Experimental results having wide band nonreciprocal characteristics are discussed with theory.

A nonreciprocal left-handed transmission line is proposed and investigated, which is composed of a normally magnetized ferrite microstrip line periodically loaded with inductive stubs but without capacitive loading. The circuit configuration becomes simpler than that of a nonreciprocal left-handed transmission line with both shunt inductive and series capacitive loadings. In the proposed structure, ferrite medium is employed as the substrate not only for the nonreciprocal characteristics but also for negative effective permeability that is essential to establish the left-handedness. After calculations of dispersion curves using equivalent circuit model, scattering parameters along with field patterns are estimated numerically with the help of electromagnetic simulation, and the experiments are also carried out. It is found that the band width of the proposed left-handed transmission line is relatively narrow but the structure still has the high isolation ratio of more than 30 dB.

In this letter, we provide a performance evaluation of a Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) with adaptive modulation in a multipath fading channel. The MB-OFDM system in conjunction with adaptive modulation technique can be considered as one of the solutions for severely degraded channels such as those common in frequency selective fading environments.

In this letter, we propose an FFT-based SNR estimation method for wireless OFDM systems, and analyze the impact of the proposed SNR estimation method on adaptive OFDM performance in slow Rayleigh fading channels. Numerical and simulation results show that the proposed method is effective and feasible for adaptive modulation in slow Rayleigh fading channels.

In this paper, we describe a bootstrapped nMOS switch that is modified to reduce leakage current for nMOS reversible energy recovery logic (nRERL) [1]. Conventional bootstrapped switches are not suitable for nRERL because they have nonadiabatic loss due to leakage current that flows while boosted. Therefore, we lowered the gate voltage of the isolation transistor in each bootstrapped switch to reduce this leakage current. With detailed analysis and simulation, we determined the range of the bias voltage, in which the switches can transfer full-swing input signals. We implemented a simple 8-bit nRERL microprocessor into silicon and measured its energy consumption to confirm our analysis. For the supply voltage of 1.8 V and the operating frequency of 880 kHz, we found that the microprocessor consumed about 8.5 pJ/cycle for 1.3 V < Vbias <1.6 V, which was just about a half of its energy consumption when Vbias = 1.7 V.

In closed-loop multiple-input and multiple-output space-division multiplexing (MIMO-SDM) systems, allocating power among multiple transmit data streams improves the channel capacity. However, the optimum power allocation values are not always available in closed-form. For instance, when we use transmission and reception schemes that do not transfer the MIMO channel into parallel orthogonal channels (e.g., eigen-mode SDM), the signal to interference plus noise ratio (SINR) of each data stream at the output of the receiver is not proportional to its corresponding transmit power. This feature makes it difficult to obtain the optimal closed-form power allocation value for each data stream. Thus, in this paper, we propose an iterative power allocation scheme for MIMO-SDM systems where the SINR is not proportional to the transmit power. Furthermore, we incorporate a transmit antenna selection scheme into the proposed power allocation scheme in order to attain further capacity enhancement. Computer simulation results are provided to show the effectiveness of the proposed power allocation schemes.

MIMO spatial multiplexing systems are attracting a lot of attention because of their high spectral effiencies. Maximum Likelihood Detection (MLD) is known to be the optimal signal detection method for MIMO spatial multiplexing systems in terms of bit error rate (BER). However, the main drawback of MLD is its high complexity. In this paper, to reduce the computational complexity of MLD and to attain good BER in MIMO spatial multiplexing systems, we propose the minimum mean square error (MMSE)-MLD that combines MMSE detection and MLD according to the estimated SINR from each transmit antenna. We also propose the ordered successive MMSE detection (OSD)-MLD that combines OSD and MLD according to the estimated SINR from the transmit antennas. Simulation results show that the proposed MMSE-MLD and OSD-MLD can attain almost identical BER to that of MLD but with less complexity.

A transition between an NRD guide, suitable for construction of high performance millimeter-wave integrated circuits, and a microstrip line, being used to mount semiconductor devices such as HEMT, HBT, and MMIC, was developed at 60 GHz. The main emphasis was placed on the manner of field matching between the NRD guide and the microstrip line. We propose adoption of this a new transition structure employing a vertical strip line, which can be easily coupled to the NRD guide, and a coaxial line connected to the microstrip line. Moreover, we applied a packaging structure with a choke circuit for the microstrip line to prevent undesired leakage between the NRD guide and the microstrip line. The insertion loss of the fabricated transition was measured to be less than 0.5 dB in the bandwidth of 3 GHz at a center frequency of 60.5 GHz. The transition was applied to MMIC amplifier integration in the NRD guide at 60 GHz. The forward and reverse gains were measured to be 15 dB and -20 dB, respectively, at 60 GHz.

A NRD guide fed dielectric lens antenna with high gain and low sidelobe characteristics is proposed for millimeter wave applications. The measured results showed very good performance at 60 GHz. It exhibited a gain of 24.9 dBi, 27 dB sidelobe level suppression.

A technique to control the radiation pattern of an NRD-guide-compatible pyramidal horn antenna, which consists of a tapered dielectric rod inserted into the horn, was developed for multiple access LAN applications at 60 GHz. By using this simple technique, the half-power beamwidth can be controlled from 11to 40.

Conventional WDM systems multiplex channels with different signal bandwidths using fixed and equal channel spacing. As a result, their spectral efficiency is rather poor. If the wavelength and the bandwidth of each channel in a WDM system could be freely changed as needed, a variety of services with different signal bandwidths could be accommodated efficiently. This is expected to yield high spectral efficiency. For this purpose, this paper proposes a WDM optically amplified system that combines optical power splitting with homodyne detection; its use in three configurations, point to point, ring (center to remote nodes), and peer to peer, is described. Coherent optical systems generally need a frequency stable local light source in addition to a sending light source in each WDM channel. We improve cost effectiveness by proposing that the output of one light source be divided to yield the local light for frequency selection by homodyne detection and the sending light source whose output is externally modulated by transmission signal. In this configuration, the local light level is low to permit high levels of sending power. The key problem is how to get high SNR with limited low-level local lights. This paper derives the optimum receiving loss condition that can maximize the SNR with local light levels as low as -20 dBm for the point to point configuration. For the ring configuration, the system overcomes the optical power loss created by splitting numbers over 1,000 even if the local lights are as low as 0 dBm. The ring configuration can, therefore, flexibly accommodate many users and services. We also elucidate the relation between SNR and BER for DPSK homodyne detection in a bandwidth-flexible system.

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.

In this paper, we discuss the construction of a large in-car spoken dialogue corpus and the result of its analysis. We have developed a system specially built into a Data Collection Vehicle (DCV) which supports the synchronous recording of multichannel audio data from 16 microphones that can be placed in flexible positions, multichannel video data from 3 cameras, and vehicle related data. Multimedia data has been collected for three sessions of spoken dialogue with different modes of navigation, during approximately a 60 minute drive by each of 800 subjects. We have characterized the collected dialogues across the three sessions. Some characteristics such as sentence complexity and SNR are found to differ significantly among the sessions. Linear regression analysis results also clarify the relative importance of various corpus characteristics.

A mode transformer between the NRD guide and the vertical strip line was developed and applied to the right angle corner, T-junction, and 3-port junction at 60 GHz. Emphasis was placed on a fully CAD-based design procedure by using an electromagnetic field simulator. Agreement between the simulated and measured performances of the junction circuit was obtained, and thus the validity of the design procedure was confirmed. A well-balanced transmission coefficient of the 3-port junction, found to be 4 0.5 dB, was observed in the bandwidth of 2 GHz around a center frequency of 60 GHz.

It is known that a high permittivity NRD guide suffers from irregular transmission phenomena. In this study, we clarified that this problem is caused by a mode coupling phenomenon between the operating and parasitic modes due to a small remaining asymmetrically air gap between the metal plates and high permittivity dielectric materials.

A flexible transmission line, consisting of a thin ceramic-compounding Teflon strip, was devised by using a high permittivity LSE-NRD guide. This transmission line has the advantage of changeable shape. Low-loss performance was confirmed by measuring the transmission loss of the 180 degree bend and the S-shaped curve in the 60 GHz frequency band.

This paper is concerned with improving noise-robustness of a multi-SNR multi-band speaker identification system by introducing automatic adjustment of subband likelihood recombination weights. The adjustment is performed on the basis of subband power calculated from the noise observed just before the speech starts in the input signal. To evaluate the noise-robustness of this system, text-independent speaker identification experiments were conducted on speech data corrupted with noises recorded in five environments: "bus," "car," "office," "lobby," and "restaurant". It was found that the present method reduces the identification error by 15.9% compared with the multi-SNR multi-band method with equal recombination weights at 0 dB SNR. The performance of the present method was compared with a clean fullband method in which a speaker model training is performed on clean speech data, and spectral subtraction is applied to the input signal in the speaker identification stage. When the clean fullband method without spectral subtraction is taken as a baseline, the multi-SNR multi-band method with automatic adjustment of recombination weights attained 56.8% error reduction on average, while the average error reduction rate of the clean fullband method with spectral subtraction was 11.4% at 0 dB SNR.

This paper proposes a SNR estimation scheme based on Gibbs sampler. This scheme can estimate SNR using a very short received sequence, and does not require any prior information of the transmitted symbol. Compared with the existing estimators, the performance of this method is better when real SNR is larger than 5 dB in both single path channel and multi-path channel.