In the main part of this paper, we present a systematic discussion for the optimum interpolation approximation in a shift-invariant wavelet and/or scaling subspace. In this paper, we suppose that signals are expressed as linear combinations of a large number of base functions having unknown coefficients. Under this assumption, we consider a problem of approximating these linear combinations of higher degree by using a smaller number of sample values. Hence, error of approximation happens in most cases. The presented approximation minimizes various worst-case measures of approximation error at the same time among all the linear and the nonlinear approximations under the same conditions. The presented approximation is quite flexible in choosing the sampling interval. The presented approximation uses a finite number of sample values and satisfies two conditions for the optimum approximation presented in this paper. The optimum approximation presented in this paper uses sample values of signal directly. Hence, the presented result is independent from the so-called initial problem in wavelet theory.

In orthogonal frequency-division multiplex access (OFDMA) downlink systems, the carrier-frequency offset (CFO) between the multiple transceivers introduces inter-carrier interference (ICI). In this letter, we propose an iterative precoding scheme to suppress the ICI due to CFO. This scheme is applied at the transmitter, and can jointly cancel the ICI for all the receivers. Moreover, by the studies of the convergence behavior of the iterations, a sufficient condition for the convergence is presented. The theoretical analysis and simulation results both show that this iterative scheme is equivalent to the zero-forcing (ZF) scheme in function, but with much lower complexity.

We give a centralized deterministic algorithm for constructing linear network error-correcting codes that attain the Singleton bound of network error-correcting codes. The proposed algorithm is based on the algorithm by Jaggi et al. We give estimates on the time complexity and the required symbol size of the proposed algorithm. We also estimate the probability of a random choice of local encoding vectors by all intermediate nodes giving a network error-correcting codes attaining the Singleton bound. We also clarify the relationship between the robust network coding and the network error-correcting codes with known locations of errors.

This study examines treatment of a boundary between media to simulate an acoustic field using the CIP method. The handling of spatial derivatives of fields is extremely important for CIP acoustic field analysis. We demonstrate a method of handling this boundary and report results of CIP acoustic field analysis using the present treatment.

In this paper, an ultra-low power variable-resolution sigma-delta (ΣΔ) modulator for biomedical application is presented. The resolution of proposed modulator can be adjusted by switching its sampling frequency and architecture. The architecture is switched between second-order single-loop modulator and fourth-order cascaded second stage noise shaped modulator to reach different resolution requirement. The proposed sigma-delta modulator is implemented by single phase integrators based on a fully differential switched-capacitor circuit. The digital cancellation logic is embedded in the chip so that it would easily be integrated with biomedical instrument for effective acquisition. Experimental results of the proposed variable-resolution ΣΔ modulator fabricated in standard CMOS 0.18 µm technology confirm the expected specifications from 65 dB signal-to-noise distortion to 96 dB with 1 kHz bandwidth and power consumption range from 48 µW to 360 µW with a 1.8 V battery supply.

Distortion characteristics caused by the thermal memory effect in power amplifiers were accurately predicted using a multi-stage thermal RC-ladder network derived by simplifying the heat diffusion equation. Assuming a steep gradient of heat diffusion near an intrinsic transistor region in a semiconductor substrate, the steady state temperature, as well as the transient thermal response at the transistor region, was estimated. The thermal resistances and thermal capacitances were adjusted to fit a temperature distribution characteristic and a step response characteristic of temperature in the substrate. These thermal characteristics were calculated by thermal FDTD simulation. For an InGaP/GaAs HBT, a step response characteristic for a square-wave voltage signal input was simulated using a large-signal model of the HBT connecting the multi-stage thermal RC-ladder network. The result was verified experimentally. Additionally, for an RF-amplifier using the HBT, the 3rd-order intermodulation distortion caused by the thermal memory effect was simulated and this result was also verified experimentally. From these verifications, a multi-stage thermal RC-ladder network can be used to accurately design super linear microwave power amplifiers and linearizers.

The reflection method is an accurate and simple method for measuring the radiation efficiency of a small antenna. However, it takes too long and has the disadvantage of underestimating the efficiency due to resonance in the cavity formed by the straight waveguide and two sliding shorts. To reduce the measurement time, one sliding short can be fixed while the other one is moved. To improve the accuracy of this technique, we can set the antenna to be measured at the center of the two sliding shorts or at a local anti-node of the standing wave in the waveguide. When one of the sliding shorts is fixed, the measured efficiency becomes negative at certain frequencies. We examine these reductions in efficiency using an equivalent transmission line model for the reflection method. We also derive analytical expressions for the overall efficiency in the above cases and verify new procedures that enable measurements to be performed without any drops in the measured efficiency.

In digital transmission and storage systems, sequences must have attributes that comply with the physical characteristics of the channel. These channel constraints can often be satisfied through constrained sequence coding techniques which avoid use of sequences that violate the given channel constraints. In the design of a constrained code, it is usually helpful to consider the PSD of the encoded sequence in order to ensure that PSD requirements are met, and to obtain an indication of bandwidth, response at dc, average power peaks, and other spectral characteristics of interest. In this paper, we introduce an approach for the construction of finite-state sequential machine (FSSM) modeled encoders to satisfy spectral requirements. This approach involves construction of either a Mealy or a Moore FSSM to represent the encoder, and evaluation of the state transition probabilities and codeword values such that the PSD of the designed code meets a predefined spectral shape. Examples in this paper demonstrate the usefulness of this approach.

FM converted CATV and super high frequency satellite TV signal transmission using lithium niobate Mach-Zehnder optical SSB modulator is proposed and demonstrated. Simultaneous FM-converted 40 CATV signal carriers (from 93 to 375 MHz) and 104 super high frequency satellite TV signal carriers (from 11.7 to 20.2 GHz) could be transmitted with good noise properties and distortion quality over 40 km of dispersive SMF with chromatic dispersion of 680 ps/nm. We clarify the required phase and power values by experiments on the relationship between sideband suppression ratio (SSR) and the phase/power to LN MZ optical SSB modulator. For instance, the absolute value of phase and power should be less than 5 degrees and 0.4 dB, respectively, to obtain SSR values above 35 dB.

Steganographic methods usually produce distortions in cover images due to the process of embedding secret bits. These distortions are hard to remove, and thus the cover image cannot be recovered. Although the distortions are always small, they cannot be allowed for some sensitive applications. In this paper, we propose a reversible embedding scheme for VQ-compressed images, which allows the original cover image to be completely recovered after the extraction of the secret bits. The embedded payload in the proposed method comprises the secret bits plus the restoration information. In order to reduce the size of payload, we utilized the spatial correlations in the image as the restoration information and then compressed the correlations by a lossless compression method. In addition, an alternative pairing method for codewords was proposed to improve the stegoed image quality and control the embedding capacity. Experimental results showed that the proposed method has the benefit of high efficiency of the steganographic process, high image quality, and adaptive embedding capacity compared with other schemes.

We consider the blind recovery problem such that images embedded with side information are given, and we want to obtain the side information under some prescribed constraints. In this case, the system equation becomes y=Ax+b where in addition to the unknown A and x, b also is an unknown quantity and but clearly not a noise component. We assume that several images with the same embedding side information are given, and the image processing to b is described as the perturbation of A. We formulate the optimization function to obtain A, b and x, under the constraint of some finite brightness levels i.e. finite alphabets.

Due to the limited resources of sensor nodes, an energy-efficient routing algorithm of Wireless Sensor Networks is considered as one of the most important issues in improving network lifetime. To resolve this issue, several routing algorithms have been suggested, but the published studies have mainly focused on minimizing distances between sensor nodes or the number of hops. These researches have also assumed that all the sensor nodes participate in the sensing task. In this paper, we propose a new cluster head selection algorithm focusing on both the density of sensor nodes and sensing-awareness that has not been considered yet in other existing researches on cluster-based routing scheme. In the real sensor network environment, only a part of sensor nodes participates in data reporting, so consideration of sensing-awareness in a routing algorithm will have effect on network efficiency. Moreover, the density of sensor nodes that has resulted from geographical location of sensor nodes can be an important factor in cluster head selection. The simulation results show that the proposed algorithm, by considering these 2 factors simultaneously, reduces energy consumption and enhances network lifetime.

Scheduling, an essential step in high-level synthesis, is an intractable process. Traditional heuristic scheduling methods usually search schedules directly in the entire solution space. In this paper, we propose the idea of searching within an intermediate solution space (ISS). We put forward a max-flow scheduling method that heuristically prunes the solution space into a specific ISS and finds the optimum of ISS in polynomial time. The proposed scheduling algorithm has some unique features, such as the correction of previous scheduling decisions in a later stage, the simultaneous scheduling of all the operations, and the optimization of more complicated objectives. Aided by the max-flow scheduling method, we implement the optimization of the IC power-ground integrity problem at the behavior level conveniently. Experiments on well-known benchmarks show that without requiring additional resources or prolonging schedule latency, the proposed scheduling method can find a schedule that draws current more stably from a supply, which mitigates the voltage fluctuation in the on-chip power distribution network.

This paper presents an investigation of radio-wave propagation characteristics in the 5 GHz band in a residential two-story house. We investigated the 3-D angular spectra of incident waves when a transmitter and a receiver were situated on the first and second floors, respectively. First of all, correlation in the measured "home environment" containing furniture such as beds, a sofa and tables was determined to confirm a quasi-static environment. Then, 3-D angular spectra measurements were performed by using an eight-element Yagi-Uda antenna as a receiving antenna. Furthermore, the 4-by-4 MIMO channel capacity at each elevation angle was estimated by using elevation angular spectra and the propagation characteristics between the first and second floors were evaluated. The results indicated that the channel capacity in the elevation direction was strongly influenced by the direction of the transmitting antenna.

A simple and efficient semi-supervised classification method is presented. An unsupervised spectral mapping method is extended to a semi-supervised situation with multiplicative modulation of similarities between data. Our proposed algorithm is derived by linearization of this nonlinear semi-supervised mapping method. Experiments using the proposed method for some public benchmark data and color image data reveal that our method outperforms a supervised algorithm using the linear discriminant analysis and a previous semi-supervised classification method.

DTW-based text-dependent speaker verification technology is an effective scheme for protecting personal information in personal electronic products from others. To enhance the performance of a DTW-based system, an impostor database covering all possible passwords is generally required for the matching scores normalization. However, it becomes impossible in our practical application scenario since users are not restricted in their choice of password. We propose a method to generate pseudo-impostor data by employing an acoustic codebook. Based on the pseudo-impostor data, two normalization algorithms are developed. Besides, a template compression approach based on the codebook is introduced. Some modifications to the conventional DTW global constraints are also made for the compressed template. Combining the normalization and template compression methods, we obtain more than 66% and 35% relative reduction in storage and EER, respectively. We expect that other DTW-based tasks may also benefit from our methods.

Web services (WS, hereafter) paradigm has attained such a relevance in both the academic and the industry world that the vision of the Internet has evolved from being considered as a mere repository of data to become the underlying infrastructure on which organizations' strategic business operations are being deployed [1]. Security is a key aspect if WS are to be generally accepted and adopted. In fact, over the past years, the most important consortiums of the Internet, like IETF, W3C or OASIS, have produced a huge number of WS-based security standards. Despite this spectacular growth, a development process that facilitates the systematic integration of security into all subprocesses of WS-based software development life-cycle does not exist. Eventually, this process should guide WS-based software developers in the specification of WS-based security requirements, the design of WS-based security architectures, and the deployment of the most suitable WS security standards. In this article, we will briefly present a process of this type, named PWSSec (Process for Web Services Security), and the artifacts used during the elicitation activity, which belongs to the subprocess WSSecReq aimed at producing a WS-based security requirement specification.

This paper describes a technique for controlling the degree of expressivity of a desired emotional expression and/or speaking style of synthesized speech in an HMM-based speech synthesis framework. With this technique, multiple emotional expressions and speaking styles of speech are modeled in a single model by using a multiple-regression hidden semi-Markov model (MRHSMM). A set of control parameters, called the style vector, is defined, and each speech synthesis unit is modeled by using the MRHSMM, in which mean parameters of the state output and duration distributions are expressed by multiple-regression of the style vector. In the synthesis stage, the mean parameters of the synthesis units are modified by transforming an arbitrarily given style vector that corresponds to a point in a low-dimensional space, called style space, each of whose coordinates represents a certain specific speaking style or emotion of speech. The results of subjective evaluation tests show that style and its intensity can be controlled by changing the style vector.

Previously Verifier-Local Revocation (VLR) group signature schemes from bilinear maps were proposed. In VLR schemes, only verifiers are involved in the revocation of a member, while signers are not. Thus, the VLR schemes are suitable for mobile environments. Furthermore, the previously proposed schemes satisfy the important backward unlinkability. This means that even after a member is revoked, signatures produced by the member before the revocation remain anonymous. This property is needed in case of a voluntary leave of a member or in case of a key loss. However, in the previous schemes, signatures become long, due to the adopted assumption, which should be improved in order to apply the schemes to the mobile environments. In this paper an improved VLR scheme is proposed with the shorter group signatures. This is achieved by using a different assumption, DLDH assumption, and improving zero-knowledge proofs in the group signatures. The length of the proposed group signatures is reduced to about 53% of that of the previous ones.

We prove that the Variational distance (and its positive multiples) is the only f-divergence that satisfies both the identity of indiscernibles and the triangle inequality. Therefore it is the unique f-divergence which serves as a metric. This point is interpreted as a fundamental confliction of the convexity for f(x) with the metric properties for its associated f-divergence. Therefore, we relax the convexity of f(x) and replace it with other constraints to create new metrics.