This paper proposes a new signal peak power reduction technique, Peak Reduction based on Control Signal Insertion (PRCSI), for broadband mobile communications based on multi-channel signaling schemes. PRCSI reduces the peak power with a peak control signal that is generated symbol-by-symbol; no signal band expansion is incurred because the peak control signal is inserted into the transmission signal band. PRCSI can achieve 4 dB peak power reduction for 8-carrier signaling, while the Eb/N0 value required to achieve 10-3 average BER is 1 dB larger with PRCSI than without it. This BER performance degradation can effectively be compensated by the proper use of Trellis coding. The proposed technique is applied to OFDM transmission systems with large carrier number. The proposed technique can achieve 3-dB peak power ratio for 128-carrier OFDM signals with less than 1-dB performance degradation at the BER of 10-3.

Adaptive Battery Conservation Management (ABCM), an effective form of power conservation for mobile terminals in an always-connected environment, was proposed and evaluated in a previous published work. The ABCM method employs three states: active, dormant, and the Battery Saving Mode (BSM). The BSM is defined as a battery-saving state; in the BSM, the mobile terminal saves power by intermittently receiving paging notifications via a paging channel between the packet bursts of a session. Two control parameters, the sleep-timer and paging interval, are set up according to packet class and are the keys to the performance of a system with this method. In real-time communications, a long sleep-timer and short paging interval are selected to minimize buffering delay. In non-real-time communications, on the other hand, a short sleep-timer and long paging interval are chosen to reduce power consumption by the mobile terminal. Our previous evaluation showed that the method is effective as a means for power conservation in non-real-time communications. In real-time communications, on the other hand, the ABCM method provides shorter buffering delays and the same battery-conservation performance as the conventional method. To further improve the ABCM method's performance, we now propose an enhanced ABCM method that employs multiple BSM sub-modes, each of which has a different paging interval. As dormant periods become longer, the mobile terminal makes transition to successive sub-modes, each of which has a longer interval than the previous one. In this paper, we evaluate the battery conservation effect of the ABCM method through theoretical analysis and computer simulation. Numerical evaluation indicates that the ABCM method will be suitable for the broadband multimedia packet-radio systems of the future.

In this paper, to enhance the power efficiency a new simple space-time coding scheme is devised with application to the OFDM based Wireless LAN system. The basic idea is from the receiver's point of view and is referred to as Virtual Constellation Mapping (VCM). We designed a new combination of the channel coding (Turbo Code) along with multiple transmit antennas (Two antennas) to achieve transmit diversity and space division multiplexing transmission. Computer simulation results showed that with the same transmission data rate, our proposed scheme can achieve better bit error rate (BER) compared with the conventional space-time trellis coded OFDM scheme in high Doppler fading channels.

A field trial, within a suburban macro-cell environment, of a space-time (ST) equalizer for TDMA mobile communication systems is described. The ST equalizer was a cascade connection of two array processors for a four-antenna array and a two-branch-metric-combining maximum-likelihood sequence estimation (MLSE) that was designed to obtain full space- and path-diversity gains from first-arrival and one-symbol-delayed signals while suppressing excessively long-delayed inter-symbol interference (ISI). The radio frequency was 3.35 GHz, the transmission rate was 4.096 Mb/s, and the modulation was QPSK. The long-delayed ISI reduction and the space-path diversity effect of the ST equalizer was validated by Eb/N0 vs. bit-error-rate (BER) curves with respect to delay spread and antenna spacing as compared with the case of an array processor alone being used.

We investigate the design of an interpolation filter of a multi-frequency time division multiple access (MF-TDMA) demodulator which is applied to digital video broadcasting-return channel system via satellite (DVB-RCS). We propose two interpolation filters for symbol timing recovery in a digital receiver where the input analog to digital conversion sampling clock is not synchronized to the transmitter symbol clock. The two proposed interpolation filters are designed by the least mean-square-error at the output of the receiver. Simulation results show that a performance improvement is achieved by employing the proposed interpolation filter.

The interconnection problem of binary circuits becomes seriously as the exponential growth of the circuits complexity has been driven by a combination of down scaling of the device size and up scaling of the chip size. Motivated by the problem, there is much research of circuits based on multiple-valued logic. On the other hand, caused by the signal propagation delay, there exist hazards in binary logic circuits. To analyze hazards in binary logic circuits, many multiple-valued logics have been proposed, and studied on their mathematical properties. The paper will discuss on a multiple-valued logic which is suitable for treating static hazards in multiple-valued logic circuits. Then, the paper will show that the prime implicants expressions of r-valued logic functions realize static hazards free r-valued logic circuits.

Various optical fiber connectors have been developed during the 20 years since optical fiber communications systems were first put into practical use. As the domain of optical fiber communication systems expanded from trunk lines to subscriber lines and customer premises the main focus changed from performance improvement to miniaturization and cost reduction. This paper describes the technical background, recent trends in standard optical connectors, and recent issues related to photonic connection technologies.

This paper proposes a new multispectral image data compression algorithm that can efficiently reduce spatial and spectral redundancies by applying classified prediction, a Karhunen-Loeve transform (KLT), and the three-dimensional set partitioning in hierarchical trees (3-D SPIHT) algorithm in the wavelet transform (WT) domain. The classification is performed in the WT domain to exploit the interband classified dependency, while the resulting class information is used for the interband prediction. The residual image data on the prediction errors between the original image data and the predicted image data is decorrelated by a KLT. Finally, the 3-D SPIHT algorithm is used to encode the transformed coefficients listed in a descending order spatially and spectrally as a result of the WT and KLT. Simulation results showed that the reconstructed images after using the proposed algorithm exhibited a better quality and higher compression ratio than those using conventional algorithms.

We propose a new frequency and frame synchronization technique for orthogonal frequency division multiplexing (OFDM) systems in frequency domain by using the channel information. The proposed frequency synchronization scheme shows optimal performance. Also it is shown that the proposed frame synchronization scheme has significantly enhanced performance improvement and wide estimation range.

This paper presents a modified microwave radio-thermometer (MRTM) with material characteristic estimator and multiple temperature conversion tables to measure subcutaneous temperature of a living body. This estimator provides a temperature retrieval unit with material characteristics such as permittivity, conductivity, thickness and geometry of the living body. The temperature retrieval unit with multiple temperature conversion tables can select one of the tables and compute temperature value corresponding to measured radiation power. In the experiments, it was shown that the radio-thermometer could reduce measurement errors of about 0.82 to 7.68 for the cases of distilled water and mixed liquid # 5 with thickness of 29.5 cm and 9.5 cm at the temperature of 37.

A bi-directional and multi-channel wireless telemetry capsule, 11 mm in diameter, is presented that can transmit video images from inside the human body and receive a control signal from an external control unit. The proposed telemetry capsule includes transmitting and receiving antennas, a demodulator, decoder, four LEDs, and CMOS image sensor, along with their driving circuits. The receiver demodulates the received signal radiated from the external control unit. Next, the decoder receives the stream of control signals and interprets five of the binary digits as an address code. Thereafter, the remaining signal is interpreted as four bits of binary data. Consequently, the proposed telemetry module can demodulate external signals so as to control the behavior of the camera and four LEDs during the transmission of video images. The proposed telemetry capsule can simultaneously transmit a video signal and receive a control signal determining the behavior of the capsule itself. As a result, the total power consumption of the telemetry capsule can be reduced by turning off the camera power during dead time and separately controlling the LEDs for proper illumination of the intestine.

In this paper, we propose an efficient requantization method for transcoding of MPEG video. Transcoding is the process of converting a compressed video format to another different compressed video format. We propose an simple and efficient transcoding by requantization in which MPEG coded video at high bit-rate is converted into MPEG bitstream at lower bit-rate. To reduce a image quality degradation, we use HVS (Human Visual System). By using this effect, the part of image in high activity region is coarsely quantized without seriously degrading the image quality. Experimental results show that the proposed method can provide good performance.

This paper describes the design of a 2.7 V operational, 200 MS/s, 14-bit CMOS D/A converter (DAC). The DAC consists of 63 current cells in matrix form for an upper 6-bit sub-DAC, and 8 current cells and R-2R ladder resistors for a lower 8-bit sub-DAC. A source degeneration resistor, for which a transistor in the triode operational region is used, is connected to the source of a MOS current source transistor in a current cell in order to reduce the influence of threshold voltage (Vth) variation and to satisfy the differential nonlinearity error specification as a 14-bit DAC. In conventional high-speed and high-resolution DACs that have the same design specifications described here, spurious-free dynamic range (SFDR) characteristics commonly deteriorate drastically as the frequency of the reconstructed waveform increases. The causes of this deterioration were carefully examined in the present study, finding that the deterioration is caused in part by the input-data-dependent time-constant change at the output terminal. Unexpected current flow in parasitic capacitors associated with current sources causes the change in the output current depending on the input data, resulting in time-constant change. In order to solve this problem, we propose a new output circuit to fix the voltage at the node where the outputs of the current sources are combined. SPICE circuit simulation demonstrates that 63 dB of SFDR characteristics for the 90 MHz reconstructed waveform at the output can be realizable when the supply voltage is 2.7 V, the clock rate is 200 MS/s, and the power dissipation is estimated to be 300 mW.

An experimental equation of V-I characteristics of breaking arc was investigated in the air at atmospheric pressure. Material of the contact pair is Ag, Au, Cu and Ni. Supply voltage is set to 42, 48 and 54 V. The electrical resistance of experimental circuit is 5 Ω. The time evolutions of arc voltage, arc current and gap length were measured, simultaneously. V-I characteristics were obtained from those measured values. The dependence of the arc voltage on the gap length was represented by an approximate formula as a straight line in order to obtain the experimental equation. And the dependence of the strength of electric field of arc column on the supply voltage was approximated to a straight line. Using these approximate formulae, the experimental equation of the dependence of the arc voltage on the arc current was obtained with the gap length as a parameter. It was shown that the experimental equation agreed with experimental data in the experimental conditions for each contact material.

Arc duration of silver contacts was measured with fixed short gap under the condition of different constant gaps and different constant currents, which are close to the minimum arc current of the contact material. The results indicated that the arc occurred even at the current less than the minimum arc current. The arc duration varies in different operations at the same testing condition and it distributes exponentially in the time range up to 100 microseconds. The time constant τ and the extinction rate λ of the distribution were calculated, and related to the arc current. It was assured by silver electrode arc that, even below the so-called minimum arc current, arc ignition may occur but, in this case, the arc duration is momentary, and, as the arc current decreases, the arc extinction rate becomes large.

The interrupting characteristics of low voltage current limiting circuit breakers have directly relationship with the magnitude and distribution of magnetic field produced by contact system and splitter plates. In order to analyze the influence of configuration of contact system on current limiting characteristics, 3D magnetic field of arc chamber (including contact system, arc, splitter plates) is calculated. Furthermore, the electromagnetic repulsion force of movable contact is also calculated. The results can be used to improve configuration of arc quenching chamber. The cooperation between operating mechanism and electromagnetic repulsion force is also analyzed in this paper.

In recent years, sliding electric contacts came to be often used under very severe conditions such as high temperature, extremely low temperature, high vacuum, etc. Conventionally, solid lubricants having excellent properties in lubricating performance are generally used compositely with a metal of high electric conductivity, because of their high electrical resistivity. In the present study, we proved that more excellent sliding electrical contacts can be produced with a design made by controlling the distribution on contact surface of a solid lubricant having excellent lubricating performance and of a metal with high electric conductivity through expansion of Greenwood's theory.

The electrical characteristics of biologically active points (BAPs) compared with those of the surrounding human skins are investigated. We confirm that BAPs have lower resistance and higher capacitance than the surrounding skins have. We find that BAPs have higher characteristic frequency than surrounding skins and sometimes the impedance spectra of BAPs have two semicircles on the complex impedance plane. Therefore, we propose the skin impedance model that is proper to the BAPs. This model describes our experimental results sufficiently.

The effect of the silicone vapor on the reliability of the micro-motor was examined. Adsorbed silicone was decomposed to SiO2 by heating due to the discharge between brush and commutator surface. It was found that the operation time until the failure was extremely shortened by the formation of SiO2. The existence of the maximum operation time until the failure was found as depending on the number of revolution. For the higher revolution, many amounts of SiO2 accumulated by the decomposition of the silicone shorten the operation time. For lower revolution, as the torque of the motor reduces, the operation time also shortens. Therefore, the maximum operation time exists for optimum revolution.

Heart sound is an acoustic wave generated by the mechanical movement of the heart and blood flow, and is a complicated, non-stationary signal composed of many signal sources. It can be divided into normal heart sounds and heart murmurs. Murmurs are abnormal signals that appear over wider ranges of frequency than normal heart sounds. They are generated at random spots in the whole period of heart sounds. The recognition of heart sounds is to differentiate heart murmurs through patterns that appear according to the generation time of murmurs. In this paper, a group of heart sounds was classified into normal heart sounds, pre-systolic murmurs, early systolic murmurs, late systolic murmurs, early diastolic murmurs, and continuous murmurs. The suggested algorithm was standardized by re-sampling and then added as an input to the neural network through wavelet transform. The neural network used Error Back - Propagation algorithm, which is a representative learning method, and controlled the number of hidden layers and the learning rate for optimal construction of networks. As a result of recognition, the suggested algorithm obtained a higher recognition rate than that of existing research methods. The best result was obtained with the average of 88% of the recognition rate when it consisted of 15 hidden layers. The suggested algorithm was considered effective for the recognition of automatic diagnosis of heart sound recognition programs.