A method to detect open node defects that cannot be detected by the conventional IDDQ test method has previously been proposed employing a sinusoidal wave superposed on the DC supply voltage. The present paper proposes a strategy to improve the detectability of the test method by means of frequency analysis of the supply current. In this strategy, defects are detected by determining whether secondary harmonics of the sinusoidal wave exist in the supply current. The effectiveness of the method is confirmed by experiments on two CMOS NAND gate packages (SSIs).

An improved signal-to-jamming and noise ratio (SJNR) method is proposed for the linear precoding of multiuser MIMO downlink systems. To well balance suppression of co-channel interference and suppression of noise, the proposed method modifies the noise variance term to argument of a piecewise linear function, and then enhances the suppression of noise. A dynamic power allocation scheme is also introduced to further decrease the overall average bit error rate of the system. Simulation results prove the effectiveness of the proposed scheme.

This study proposes a novel structure of index-guiding square photonic crystal fibers (SPCF) having simultaneously ultra-flattened chromatic dispersion characteristics and low confinement losses in a wide wavelength range. The finite difference method (FDM) with anisotropic perfectly matched layers (PMLs) is used to analyze the various properties of square PCF. The findings reveal that it is possible to design five-ring PCFs with a flattened negative chromatic dispersion of 0-1.5 ps/(nm.km) in a wavelength range of 1.27 µm to 1.7 µm and a flattened chromatic dispersion of 01.15 ps/(nm.km) in a wavelength range of 1.25 µm to 1.61 µm. Simultaneously it also exhibited that the confinement losses are less than 10-9 dB/m and 10-10 dB/m in the wavelength range of 1.25 µm to 1.7 µm.

A novel ratio-oriented definition based on 2T2R (Two transistors & two phase change resistors) phase change memory (PCM) cell structure is proposed to gain a high density by multilevel storage. In this novel solution, no reference is needed and good robustness remains still as conventional 2T2R, which is crucial when feature size scales to nanometer technology node. A behavioral SPICE model together with a preliminary simulation proves the idea to be feasible, and further optimization has been carried out. In addition, based on the ratio-oriented definition, a simpler and faster Error Control Coding (ECC) can be realized with n-Error-detection feasible.

IEEE 802.11 DCF is an asynchronous and distributed MAC protocol which does not require the existence of a central controller for medium access coordination. This flexibility, which is due to DCF's contention-based nature, comes at the expense of the overhead associated with contention resolution. The overhead consists of frame collision time and channel idle time, which is particularly severe when channel is saturated. In this paper, we present an enhancement of DCF which aims at reducing its contention resolution overhead by equipping it with a distributed reservation mechanism. The proposed reservation mechanism enhances collision avoidance mechanism of DCF by enforcing a partially ordered medium access through an implicit agreement between neighboring nodes. Simulation results, using ns-2 network simulator, show that the added reservation scheme 1) effectively reduces DCF's overhead and improves channel utilization particularly when node density and traffic load is high, 2) significantly enhance DCF's fairness.

In nature an unbalanced clock tree exists in a SoC because the clock sinks of IPs have distinct input capacitive loads and internal delays. The construction of a bottom-up RLC clock tree with minimal clock delay and zero skew is crucial to ensure good SoC performance. This study proves that an RLC clock tree construction always has no zero skew owing to skew upward propagation. Specifically, this study proposes the insertion of two unit-size buffers associated with the binary search for a tapping point into each pair of subtrees to interrupt the non-zero skew upward propagation. This technique enables reliable construction of a buffered RLC clock tree with zero skew. The effectiveness of the proposed approach is demonstrated by assessing benchmarks.

In this paper, we present a design method for fixed-width squarer that receives an n-bit input and produces an n-bit squared product. To efficiently compensate for the truncation error, modified Booth-folding encoder signals are used for the generation of error compensation bias. The truncated bits are divided into two groups (major and minor) depending upon their effects on the truncation error. Then, different error compensation methods are applied to each group. By simulations, it is shown that the proposed fixed-width squarers have lower error than other fixed-width squarers and are cost-effective.

Irregular LDPC codes can achieve better error rate performance than regular LDPC codes. However, irregular LDPC codes have higher error floors than regular LDPC codes. The Ordered Statistic Decoding (OSD) algorithm achieves approximate Maximum Likelihood (ML) decoding. ML decoding is effective to lower error floors. However, the OSD estimates satisfy the parity check equation of the LDPC code even the estimates are wrong. Hybrid decoder combining LLR-BP decoding algorithm and the OSD algorithm cannot also lower error floors, because wrong estimates also satisfy the LDPC parity check equation. We proposed the concatenated code constructed with an inner irregular LDPC code and an outer Cyclic Redundancy Check (CRC). Owing to CRC, we can detect wrong codewords from OSD estimates. Our CRC-LDPC code with hybrid decoder can lower error floors in an AWGN channel. In wireless communications, we cannot neglect the effects of the channel. The OSD algorithm needs the ordering of each bit based on the reliability. The Channel State Information (CSI) is used for deciding reliability of each bit. In this paper, we evaluate the Block Error Rate (BLER) of the CRC-LDPC code with hybrid decoder in a fast fading channel with perfect and imperfect CSIs where 'imperfect CSI' means that the distribution of channel and those statistical average of the fading amplitudes are known at the receiver. By computer simulation, we show that the CRC-LDPC code with hybrid decoder can lower error floors than the conventional LDPC code with hybrid decoder in the fast fading channel with perfect and imperfect CSIs. We also show that combining error detection with the OSD algorithm is effective not only for lowering the error floor but also for reducing computational complexity of the OSD algorithm.

Multiple-input multiple-output (MIMO) multiplexing is an attractive technique to achieve very high-speed transmission with a limited bandwidth. Recently, we proposed an iterative frequency-domain interference cancellation (FDIC) for single-carrier MIMO (SC-MIMO) multiplexing. In our previous work, assuming that the interference from the other antennas can be perfectly cancelled in FDIC, one-dimensional minimum mean square error (1D-MMSE) frequency-domain equalization (FDE) was used. However, the residual interference remains after performing FDIC. In this paper, to improve the transmission performance with iterative FDIC, we replace 1D-MMSE FDE by 2D-MMSE FDE, which takes the residual interference from the other antennas after FDIC into account. We investigate, by computer simulation, the throughput performance of rate compatible punctured turbo coded hybrid ARQ (RCPT-HARQ) with MIMO multiplexing in a frequency-selective Rayleigh fading channel.

This paper proposes a new blind adaptive MLSE equalizer for frequency selective mobile radio channels. The proposed equalizer performs channel estimation for each survivor path of the Viterbi algorithm (VA), and restricts the number of symbol candidates for the channel estimation in order to reduce prohibitive complexity. In such channel estimation, autocorrelation matrices of the symbol candidates are likely to become singular, which increases the estimation error. To cope with the singularity, the proposed equalizer employs a recursive channel estimation algorithm using the Moore-Penrose generalized inverse of the autocorrelation matrix. As another problem, the blind channel estimation can yield plural optimal estimates of a channel impulse response, and the ambiguity of the estimates degrades the BER performance. To avoid this ambiguity, the proposed equalizer is enhanced so that it can take advantage of the fractional sampling. The enhanced equalizer performs symbol-spaced channel estimation for each fractional sampling phase. This equalizer combines separate channel estimation errors, and provides the sum to the VA processor as the branch metric, which tremendously reduces the probability that a correct estimate turns into a false one. Computer simulation demonstrates the effectiveness of the proposed equalizers in the frequency selective fading channels.

This paper describes the explicit modeling of a state duration's probability density function in HMM-based speech synthesis. We redefine, in a statistically correct manner, the probability of staying in a state for a time interval used to obtain the state duration PDF and demonstrate improvements in the duration of synthesized speech.

In this paper, the authors propose a circularly polarized printed antenna combining a slot array antenna and a patch antenna, with dual-band operation. The proposed antenna has good isolation performance, is compact, and has simple configuration. This antenna is composed of two parts, a patch antenna (for Rx) on the top, and a slot array antenna (for Tx) on the bottom, respectively. The element layout is such that the lower radiation element is not hidden by the upper one for wide observation angle. Hence, both radiation elements can naturally radiate the targeted polarization. Both slot array and patch antenna are fed by electromagnetically coupled microstrip line feed. With such a configuration, it is possible to efficiently obtain good isolation characteristics for both frequency bands. Furthermore, this antenna can be easily composed and it is not necessary to use any feeding pin or via hole. The target of this antenna is mobile communications applications such as mobile satellite communications, base-station of wireless LAN, etc. Here, the design techniques are discussed and the numerical and experimental analyses are presented.

A novel pedestrian tracking scheme based on a particle filter is proposed, which adopts a skeleton model of a pedestrian for a state space model and distance transformed images for likelihood computation. The 6-stick skeleton model used in the proposed approach is very distinctive in representing a pedestrian simply but effectively. By the experiment using the real sequences provided by PETS, it is shown that the target pedestrian is tracked adequately by the proposed approach with a simple silhouette extraction method which consists of only background subtraction, even if the tracking target moves so complicatedly and is often so cluttered by other obstacles that the pedestrian can not be tracked by the conventional methods. Moreover, it is demonstrated that the proposed scheme can track the multiple targets in the complex case that their trajectories intersect.

In recent years, digital watermarking has become a popular technique for hiding information in digital images to help protect against copyright infringement. In this paper we develop a high quality and robust watermarking algorithm that combines the advantages of block-based permutation with that of neighboring coefficient embedding. The proposed approach uses the relationship between the coefficients of neighboring blocks to hide more information into high frequency blocks without causing serious distortion to the watermarked image. In addition, an extraction method for improving robustness to mid-frequency filter attacks is proposed. Our experimental results show that the proposed approach is very effective in achieving perceptual imperceptibility. Moreover, the proposed approach is robust to a variety of signal processing operations, such as compression (JPEG), image cropping, sharpening, blurring, and brightness adjustments. The robustness is especially evident under blurring attack.

In this paper, we derive state equations for linearized discrete-time models of forth-order charge-pump phase-locked loops. We solve the differential equations of the loop filter by using the initial conditions and the boundary conditions in a period. The solved equations are linearized and rearranged as discrete-time state equations for checking stability conditions. Some behavioral simulations are performed to verify the proposed method. By examining the stability of loops with different conditions, we also propose an expression between the lower bound of the reference frequency, the open loop unit gain bandwidth, and the phase margin.

This paper investigates the dynamic spectrum management problem for digital subscriber lines. Two new distributed dynamic spectrum management algorithms, which improve upon the existing iterative water-filling algorithm, are proposed. Unlike the iterative water-filling algorithm, in which crosstalk interference is reduced by using adaptive power backoff, the new algorithms employ full power and mitigate crosstalk interference by shifting one user's spectrum away from the other's. Simulation results show that the new algorithms achieve significant performance gains over the iterative water-filling algorithm in mixed central office/remote terminal (CO/RT) deployment asymmetric digital subscriber line (ADSL) and upstream very-high bit-rate digital subscriber line (VDSL).

This paper surveys and introduces propagation studies and models that are expected to contribute to the development of broadband wireless systems. The survey focused on theory-based propagation models, experimental measurement data useful for modeling, and transmission characteristic evaluations using propagation models. The survey did not attempt to cover all papers in the research fields, but rather took key papers for various relevant subjects and described them in some detail. The basic characteristics of multipath propagation are summarized from the viewpoints of narrow-band (NB), wide-band (WB), and ultra wide-band (UWB). Recent studies on spatio-temporal propagation models and the relationship between models and systems are introduced. To clarify the relationship between OFDM, which is a representative of wideband data transmission schemes, and wave propagation factors, problems due to large delay spread and large Doppler spread are highlighted. Finally, studies on UWB propagation measurement and propagation models are introduced.

The utilization of a high-Tc superconductor for implementing a superconducting qubit is to be expected. Recent researches on the quantum property of Josephson junctions in high-Tc superconductors indicate that the low energy quasiparticle excitation is weak enough to observe the macroscopic quantum tunneling. Therefore, a detailed study on the quantum property of high-Tc Josephson junctions becomes more important for applications. We show our experimental results of the macroscopic tunneling of current biased intrinsic Josephson junctions in Bi-2212 and its resonant activation in the presence of microwave radiation.

Recently, we proposed space-time block coded-joint transmit/receive antenna diversity (STBC-JTRD) for narrow band transmission in a frequency-nonselective fading channel; it allows an arbitrary number of transmit antennas while limiting the number of receive antennas to 4. In this paper, we extend STBC-JTRD to the case of frequency-selective fading channels and propose frequency-domain STBC-JTRD for broadband direct sequence-spread spectrum (DSSS) signal transmission. A conditional bit error rate (BER) analysis is presented. The average BER performance in a frequency-selective Rayleigh fading is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation of the signal transmission. Performance comparison between frequency-domain STBC-JTRD transmission and joint space-time transmit diversity (STTD) and frequency-domain equalization (FDE) reception is also presented.

We report on a subsystem of electromagnetic wave radiation and propagation estimation using high-Tc superconducting (HTS) receiving filters for S band. The subsystem, comprised of HTS filters, a rubidium standard signal generator (Rb SSG), a global positioning system (GPS) unit, etc., was used to evaluate the electromagnetic-wave (EMW) intensities, frequencies, the frequency interferences and the ground positions where the EM are measured. The developed subsystem showed high frequency selectivity for S band by using the HTS filters. Furthermore, we verified that the subsystem with the HTS filters operated on the moving car.