A major step in the numerical solution of electromagnetic scattering problems involves the computation of the convolution based reaction integrals. In this paper a procedure based on the analytical Fourier transform is introduced which allows us to calculate the convolution-based reaction integrals in the spectral domain without evaluating any convolution products directly. A numerical evaluation of the computational cost is presented to show the efficiency of the method when handling electrically large problems.

In CDMA cellular systems, the frequency reuse factor equals one. Therefore, the soft-handoff technology with combining macroscopic diversity was introduced to enhance the link performance. In this work, a novel macroscopic diversity combining scheme is proposed to enhance the link performance of the forward-link. The basic concept of this scheme is to integrate error correction coding into the soft-handoff technology. According to the number of soft-handoff channels, the source information is encoded by a convolutional code with a lower code rate. The coded symbols are then equally distributed to all channels from different BSs to the MS, and each channel carries a disjointed set of coded symbols. For this proposed scheme, no extra transmission power or bandwidth is required. The only cost is a slight increase of the encoding and decoding complexity of the convolutional codes. Numerical and simulation results show that a performance gain of 1 dB in bit energy-to-total noise power density ratio can be obtained as compared with the conventional scheme in the same conditions.

A semi-supervised classification method is presented. A robust unsupervised spectral mapping method is extended to a semi-supervised situation. Our proposed algorithm is derived by linearization of this nonlinear semi-supervised mapping method. Experiments using the proposed method for some public benchmark data reveal that our method outperforms a supervised algorithm using the linear discriminant analysis for the iris and wine data and is also more accurate than a semi-supervised algorithm of the logistic GRF for the ionosphere dataset.

We describe an online method for selecting and annotating highlight scenes in soccer matches being televised. The stadium crowd noise and the play-by-play announcer's voice are used as input signals. Candidate scenes for highlights are extracted from the crowd noise by dynamic thresholding and spectral envelope analysis. Using a dynamic threshold solves the problem in conventional methods of how to determine an appropriate threshold. Semantic-meaning information about the kind of play and the related team and player is extracted from the announcer's commentary by using domain-based rules. The information extracted from the two types of audio input is integrated to generate segment-metadata of highlight scenes. Application of the method to six professional soccer games has confirmed its effectiveness.

We demonstrate single electron counting on an alkanethiol-protected Au nanodot in a double-barrier tunneling structure by noncontact atomic-force spectroscopy (nc-AFS). The Coulomb step width dependence on the Au nanodot diameter is observed. Evaluation of fractional charge Q0 and contact potential difference by nc-AFS reveals a Vd-independent voltage shift due to Q0.

In situ observations were mainly performed by using slab optical waveguide (SOWG) spectroscopy synchronized with potential step measurements to investigate the time dependent spectral change of the adsorbed heptyl viologen cation radicals (HV+) in thin deposition layer on indium-tin-oxide (ITO) electrodes. Several absorption bands, which indicated a monomer and dimer of HV+ were co-adsorbed on ITO electrode surface with a monolayer or a few layers deposition, were observed in UV-visible region. The time dependent spectra yielded some important molecular information for the adsorption phenomena of HV+ on the electrode surface. All observed absorption bands disappeared completely when the electrode potential of -200 mV vs. Ag/AgCl was applied, which indicated the adsorbed HV+ species were electrochemically reoxidized on the ITO electrode.

"Cognitive radio" and "software-defined radio" (SDR) are today an important consideration in major spectrum debates in the United States. The U.S. drafted its first SDR rules in 2001, and since has continued efforts to resolve potential regulatory concerns and facilitate the benefits of the technology. At the same time, Japan has had a very rich experience in the lab with SDR, with significant achievements on many engineering topics. However, the regulatory state of SDR in Japan has not kept pace with the United States. Likewise cognitive radio, while a topic of inquiry, betrays a different focus. The paper explores why the paths for these technologies have diverged in the U.S. and Japan.

In situ observation of the adsorption process and reduction behavior of hemoglobin adsorbed on a bare glass surface was studied using slab optical waveguide (SOWG) spectroscopy. The peak position of the absorption band of hemoglobin adsorbed on the glass surface was almost the same as that of hemoglobin in solution. This result agrees with results previously reported by our group. The adsorbed hemoglobin molecules were also reduced by sodium dithionite solution. The adsorbed hemoglobin molecules still maintained their function in this experimental condition.

It is well known that the diversity gain attained by DCA (Dynamic Channel Allocation) is generally very high over OFDM (Orthogonal Frequency Division Multiplexing)-based broadband networks. This paper introduces a numerical approach for measuring the performance gain afforded by DCA. In the mathematical analysis, the property of order statistics is adopted to derive the upper bound of the expected throughput via the use of DCA. In the simulation, it was possible to achieve a gain of 5 dB by exploiting multi-user and spectral diversities when the number of users is 16 and the total number of subcarriers is 256.

This paper presents an overview of research, development, standardization and regulation activities on ultra wideband (UWB) technologies in National Institute of Information and Communications Technology (NICT). NICT started a project on UWB technologies since 2002, and organized UWB consortium in cooperation with more than 20 companies and 7 universities in Japan. Up to now, we have been conducting numerous UWB R&D including the following main works: i) key technology development such as MMIC chips, antennas and other devices, ii) measurement and channel modeling for UWB signal propagation, iii) standardization in international activities of IEEE 802.15, ITU-R TG1/8 as well as in a national regulatory committee of Ministry of Internal Affair and Communications (MIC). The UWB systems we have studied occupy frequency bands range from microwave band (3-5 GHz) to quasi-millimeter wave band (24-29 GHz). Various prototype UWB systems including multi-functional terminals have been developed. The output of NICT has been succeeded by industrial parties with with national and international standardization and regulation.

In this paper, we propose a new projector-based display which can perform the color simulator for print industry. The proposed color simulator can change the color of print by projecting the image onto the print. A color of print can be matched to the desired color by projecting the image which is calculated to minimize the color difference between the colors of target print and current print. This current print is measured by digital camera or digital scanner. Ideally, spectral camera or scanner is expected to be used for accurate color simulation on the current print, but it costs a lot for practical application. Therefore, in this paper, we compared two methods for color matching, one is the tristimulus-based method with XYZ tristimulus values and the other is the spectral-based method with spectral values. As the result of computer simulation, the average color difference ΔE *94 was 0.27 by the spectral-based method between the reflected radiance from the color of target print and the color of current print with projector, and the average color difference ΔE *94 was 2.09 by the tristimulus-based method. The efficiency of the proposed system is verified by the subjective evaluation between the target and current print with appropriate image projection.

We have developed a spread-spectrum Phase-Locked Loop (PLL) for serial Advanced Technology Attachment (ATA) applications. We investigated the relation between the output jitter of PLLs in serial ATA applications and ΣΔ modulators in PLLs. On the basis of this study, we developed a spread-spectrum PLL for serial ATA applications and achieved a combination of small jitter and large electromagnetic interference (EMI) peak power reduction. This was achieved using two key components: multi-bit ΣΔ-controlled PLL and voltage-controlled oscillation with cross-coupled load delay cells. Using a 0.15-µm complementary metal-oxide semiconductor process, we fabricated a complete serial ATA transceiver featuring a spread-spectrum clock generator (SSCG). We achieved a spread-spectrum PLL with 10-dB EMI reduction and 8.1 ps random jitter for use in serial ATA applications. All other measured results for SSCG performance were very good and showed that the spread-spectrum generator more than satisfies serial ATA specifications.

In this paper, the performance of narrow band interference (NBI) rejection scheme for direct sequence spread spectrum (DS/SS) is analyzed. A single-tapped complex FIR filter is used for filtering a chip code to suppress NBI. In this system, the spectrum of transmitted signal has a null at an arbitrary frequency. By choosing filter coefficients, we place this null at NBI center frequency to mitigate the effect of NBI. The performance of this scheme is theoretically analyzed and validated by simulation. We also compare the effectiveness against BPSK interference between the chip code filtering and received signal filtering. The results indicate the chip code filtering is effective against single-tone and BPSK interference, and gains better performance than the received signal filtering at certain level of SNR.

This letter proposes a novel geographic channel assignment (GCA) framework for dynamic channel allocation (DCA) in broadband wireless access networks (BWANs). The proposed GCA scheme is based on the characteristics of radio propagation, which focuses on the relationship between transmission distances and communication parameters, e.g., signal-to-noise ratio (SNR) etc., and uses a signal-aware distance estimation scheme to determinate an appropriate channel for communication. This method significantly increases the capacity of the BWA system. Simulation results show that the GCA framework can yield approximate two times throughput of the IEEE 802.16 standard specifications as well as obtain significantly lower call blocking probability compared with classical channel assignment methods.

If the signal is not Gaussian, then the power spectral density (PSD) approach is insufficient to analyze signals and we resort to estimate the higher order spectra of the signal. However, estimation of the higher order spectra is even more time consuming, for example, the complexity of trispectrum is O(N 4). This problem becomes even more serious when short time Fourier transform (STFT) is computed - computation of the trispectrum is required after every shift of the window. In this paper, a method to recursively compute trispectrum has been presented and it is shown that the computational complexity, for a window size of N, is reduced to be O(N 3) and is the same as the space complexity.

Frequency-modulated clock signals are widely used in personal computers to reduce the amplitude of the clock harmonic noise, as measured using an electromagnetic interference (EMI) test receiver. However, the power of the clock harmonics is not decreased with this technique called spread spectrum clocking (SSC). Hence, the impact of the harmonics of a frequency-modulated clock on the bit error rate (BER) and packet error rate (PER) of a Bluetooth system is theoretically analyzed. In addition, theoretical analysis covers the effectiveness of a frequency hopping spread spectrum (FH-SS) scheme and forward error correction (FEC) in mitigating the degradation in the BER and PER caused by clock harmonic interference. The results indicate that the BER and PER strongly depend on the modulating frequency and maximum frequency deviation of the clock harmonic. They also indicate that radiated clock harmonics may considerably degrade the BER and PER when a Bluetooth receiver is very close to a personal computer. Frequency modulating the clock harmonics slightly reduces the BER while it negligibly reduces the PER.

In this paper, a parallel combinatory spread spectrum (PC/SS) system using a constant amplitude signaling scheme is proposed. The amplitude of the transmitted signal from multicode transmission systems such as PC/SS systems have a large dynamic range which requires that amplifiers have a wide linearity in the transmitter. From a view point of power efficiency, however, it is reasonable to use non-linear amplifiers rather than linear ones. In that case, the bit error rate performance must degrade because of non-linear distortion. The proposed system can avoid influence of the non-linear amplifiers by making the transmitted signal have a constant amplitude. The bit error rate performance and the data transmission rate performance are investigated. They prove that the proposed system is an attractive candidate among the constant amplitude signaling systems.

We extend the sliding block code in symbolic dynamics to transform J (≥2) sequences of Markov chains with time delays. Under the assumption that the chains are irreducible and aperiodic, we prove the central limit theorem (CLT) for the normalized sums of extended sliding block codes from J sequences of Markov chains. We apply the theorem to the system analysis of asynchronous spread spectrum multiple access (SSMA) communication systems using spreading sequences of Markov chains. We find that the standard Gaussian approximation (SGA) for estimations of bit error probabilities in such systems is the 0-th order approximation of the evaluation based on the CLT. We also provide a simple theoretical evaluation of bit error probabilities in such systems, which agrees properly with the experimental results even for the systems with small number of users and low length of spreading sequences.

The convergence speed of the conventional adaptive LMS algorithms for time delay estimation (TDE) is highly dependent on the spectral distribution of the desired random source signals of interest, thus the performance of TDE might be degraded, dramatically. To solve this problem, in this letter, a DCT-transform domain constrained adaptive normalized-LMS filtering scheme, referred to as the adaptive constrained DCT-LMS algorithm, is devised for TDE. Computer simulation results verify that the proposed scheme can be used to achieve desired performance, for input random signals with different spectral distributions; it outperforms the unconstrained DCT-LMS and time-domain constrained adaptive LMS algorithms.

Breaking arcs are generated between a pair of Cu electrical contacts in a DC 42 V/10.5 A circuit, and the arc voltage, the arc current and the time-resolved arc spectral intensities near contact surfaces are simultaneously measured. The arc temperature is calculated from some spectral intensities emitted from Cu neutral atoms using the Boltzmann plot method. The arc temperatures near the cathode and anode surfaces are measured, and the following experimental results were obtained. (1) Time evolutions of the spectral intensities and the calculated arc temperature have similar characteristics. (2) The arc temperature near the anode surface is higher than that near the cathode surface, and the temperature fluctuation near the anode surface is larger than that near the cathode. (3) Just before arc extinction, the arc temperature near the cathode surface is almost constant for many breaking operations but the arc temperature near the anode surface varies.