A novel spatially modulated communication method, appropriate for wireless power transmission applications at 5.8GHz, is proposed using dual scatterers embedded with lumped elements. Analytical expression for the received wave in the spatial modulation is derived, and the characteristics are verified with simulation and measurement by varying the embedded capacitor. The maximum measured variation of the received voltage is more than 15dB and that of the phase is more than 270 degrees at 5.8GHz. The estimated amplitude modulation factor is more than 70%. Using the data obtained, we estimate the practical received waveforms modulated by the applied voltage to a varactor for the amplitude modulation scheme.

Spatial correlation is an index for evaluating performance of multi-antenna systems. Although various equations exist, the distinction remains evasive. This paper presents applicable condition of equations for spatial correlation coefficient considering propagation channels. We reveal that under Rayleigh fading environments, the spatial correlation is properly evaluated by the equation based on three-dimensional radiation patterns, however, under environments with strong direct waves, the equation based on the channel matrix should be used for the evaluation.

The classification of human motion is an important aspect of monitoring pedestrian traffic. This requires the development of advanced surveillance and monitoring systems. Methods to achieve this have been proposed using micro-Doppler radars. However, reliable long-term data and/or complicated procedures are needed to classify motion accurately with these conventional methods because their accuracy and real-time capabilities are invariably inadequate. This paper proposes an accurate and real-time method for classifying the movements of pedestrians using ultra wide-band (UWB) Doppler radar to overcome these problems. The classification of various movements is achieved by extracting feature parameters based on UWB Doppler radar images and their radial velocity distributions. Experiments were carried out assuming six types of pedestrian movements (pedestrians swinging both arms, swinging only one arm, swinging no arms, on crutches, pushing wheelchairs, and seated in wheelchairs). We found they could be classified using the proposed feature parameters and a k-nearest neighbor algorithm. A classification accuracy of 96% was achieved with a mean calculation time of 0.55s. Moreover, the classification accuracy was 99% using our proposed method for classifying three groups of pedestrian movements (normal walkers, those on crutches, and those in wheelchairs).

We evaluated the behavior of a multi-user multiple-input multiple-output (MIMO) system in time-varying channels using measured data. A base station for downlink or broadcast transmission requires downlink channel state information (CSI), which is outdated in time-varying environments and we encounter degraded performance due to interference. One of the countermeasures against time-variant environments is predicting channels with an autoregressive (AR) model-based method. We modified the AR prediction for a time division duplex system. We conducted measurement campaigns in indoor environments to verify the performance of the scheme of channel prediction in an actual environment and measured channel data. We obtained the bit-error rate (BER) using these data. The AR-model-based technique of prediction assuming the Jakes' model was found to reduce BER. Also, the optimum AR-model order was investigated by using the channel data we measured.

In this paper, we propose periodic and aperiodic security limits for compromising emanations in the VHF and UHF bands. First, we perform the electromagnetic emanation security (EMSEC)-channel measurements in the 200-1000MHz frequency bands. Second, we analyse the pathloss characteristics of the indoor EMSEC-channel based on these measurements. Through this EMSEC-channel analysis, we affirm that the total radio attenuation, which is one of the key parameters for determining the security limits for compromising emanations, follows the Rician distribution. With these results, we propose that periodic and aperiodic emission security limits can be classified into two levels depending on the total radio attenuation and the extent of required confidentiality. The proposed security limits are compared with other security limits and existing civil and military EMC standards.

The underlaying architecture of Device-to-device (D2D) communication supports direct communication between users by reusing the radio resources of the LTE-A system. Despite the co-channel interference between the conventional cellular user equipment (CUE) and the D2D communication user equipment (DUE), LTE-A system can improve the combined data rate of CUEs and DUEs through effective transmit power control and resource allocation schemes. In this paper, we propose a novel mechanism, which combines the resource allocation scheme with the transmit power control scheme to maximize the overall data rate (defined as the sum-rate in the paper). We perform system-level simulations to determine the effectiveness of the proposed mechanism in terms of increasing the sum-rate. The simulation result shows that the proposed mechanism can improve the sum-rate in an underlaying LTE-A system that supports D2D communication.

To develop an envelope-tracking (ET) amplifier for next-generation cellular base stations, we propose a wideband envelope modulator, consisting of a linear-mode class-B amplifier and a switch-mode class-D amplifier. The function of the modulator is to track the envelope signal and supply voltage to an RF amplifier. To meet the requirements of a large-current and high-voltage supply that can handle a wideband signal, an “Alexander current-feedback amplifier topology” is applied to the linear-mode class-B amplifier. The Alexander topology not only boosts the voltage but also enhances the current capacity of a commercial high-speed operational amplifier (op-amp) by means of a push-pull stage with current mirrors and a buffer amplifier at the output of the op-amp. With this topology, a linear-mode amplifier can provide several-ampere-level current to a 11-Ω load. A prototype of the wideband envelope modulator is shown to achieve the efficiency of 71% with a 20-MHz WiMAX envelope signal at output power of 72W.

This paper presents design and radiation properties of a radial line microstrip antenna array (RL-MSAA) for linear polarization. A stacked circular microstrip antenna (C-MSA) is used as a radiation element for the RL-MSAA. Radiation phase of the stacked C-MSA is controlled by tuning radii of the lower and upper patches, therefore, the desired phase distribution of the RL-MSAA can be designed. In this paper, a linearly polarized RL-MSAA with three concentric rows of the stacked C-MSAs at a spacing of 0.65 wavelengths for uniform aperture distribution is designed and tested in 12GHz. The experimental results reveal that validity of the linearly polarized RL-MSAA with the stacked C-MSAs for radiation phase control is demonstrated.

In this paper, we propose a novel baseband (BB) phase shifter (PS) using a fixed-gain-amplifier (FGA) matrix. The proposed BB PS consists of 5 stages of a vector synthesis type FGA matrix with in-phase/quadrature-phase (I/Q) input/output interfaces. In order to achieve low gain variation between phase shift states, 3rd to 5th stages are designed to have a phase shift of +φi and -φi (i=3,4,5). To change between +φi and -φi phase shift states, two FGAs with DC bias in-phase/out-phase switches are used. The two FGAs have the same gain, therefore ideally no gain variation can be achieved. Using this configuration, phase shift error and gain variation caused by process mismatch and temperature variation can be reduced. Fabricated 5-bit BB PS has 3-dB bandwidth of 1.05GHz, root-mean-square (rms) phase errors lower than 2.2°, rms gain variations lower than 0.42dB. Power consumption of the PS core and output buffer are 4.9mW and 14.3mW, respectively. 1-dB compression output power is -12.5dBm. The fabricated PS shows that the total phase shift error and gain variation are within the required accuracy of a 5-bit PS with no requirement of calibration.

In this letter, we use the saliency maps obtained by several bottom-up methods to learn a model to generate a bottom-up saliency map. In order to consider top-down image semantics, we use the high-level features of objectness and background probability to learn a top-down saliency map. The bottom-up map and top-down map are combined through a two-layer structure. Quantitative experiments demonstrate that the proposed method and features are effective to predict human fixation.

Many fatal accidents involving safety-critical reactive systems have occurred in unexpected situations, which were not considered during the design and test phases of system development. To prevent such accidents, reactive systems should be designed to respond appropriately to any request from an environment at any time. Verifying this property during the specification phase reduces the development costs of safety-critical reactive systems. This property of a specification is commonly known as realizability. The complexity of the realizability problem is 2EXPTIME-complete. We have introduced the concept of strong satisfiability, which is a necessary condition for realizability. Many practical unrealizable specifications are also strongly unsatisfiable. In this paper, we show that the complexity of the strong satisfiability problem is EXPSPACE-complete. This means that strong satisfiability offers the advantage of lower complexity for analysis, compared to realizability. Moreover, we show that the strong satisfiability problem remains EXPSPACE-complete even when only formulae with a temporal depth of at most 2 are allowed.

Quantum steganography is to send secret quantum information through a quantum channel, such that an unauthorized user will not be aware of the existence of secret data. The depolarizing channel can hide quantum information by disguising it as channel errors of a quantum error-correcting code. We improve the efficiency of quantum steganography with noisy depolarizing channels, by modifying the twirling procedure and adding quantum teleportation. The proposed scheme not only meets the requirements of quantum steganography but also has higher efficiency.

Mutual information (MI) is a standard measure of statistical dependence of random variables. However, due to the log function and the ratio of probability densities included in MI, it is sensitive to outliers. On the other hand, the L2-distance variant of MI called quadratic MI (QMI) tends to be robust against outliers because QMI is just the integral of the squared difference between the joint density and the product of marginals. In this paper, we propose a kernel least-squares QMI estimator called least-squares QMI (LSQMI) that directly estimates the density difference without estimating each density. A notable advantage of LSQMI is that its solution can be analytically and efficiently computed just by solving a system of linear equations. We then apply LSQMI to dependence-maximization clustering, and demonstrate its usefulness experimentally.

In order to employ Multiple-Input-Multiple-Output (MIMO) techniques, multiple antenna branches are necessary and as a consequence the installation space requirements are increased. Since the installation space is limited, much attention is now focused on utilizing polarization characteristics in MIMO configurations to relax the requirements. This is called Orthogonal Polarization-MIMO in this paper. To evaluate accurately the performance of Orthogonal Polarization-MIMO, a channel model that can handle the polarization dispersion characteristics of propagation paths is essential. Up to now, the spatial-temporal dispersion characteristics of paths have been investigated in detail. However, there are only a few reports on the polarization dispersion characteristics. In this paper, we propose a new power profile for the rotational polarized angle as an evaluation model for polarization dispersion, and clarify the analyzed power profile based on measurement data in an urban macrocell environment.

In this letter, we consider the global exponential stabilization problem by output feedback for a class of nonlinear systems. Along with a newly proposed matrix inequality condition, the proposed control method has improved flexibility in dealing with nonlinearity, over the existing methods. Analysis and examples are given to illustrate the improved features of our control method.

In the Knill-Laflamme-Milburn (KLM) scheme, quantum teleportation is nearly deterministically carried out with linear optics. To reconstruct an original quantum state, however, a phase shift is required for an output state. We exhibit a proper phase shift to complete quantum teleportation.

In this paper, Hermite polynomial representation is proposed as an alternative way to represent finite fields of characteristic two. We show that multiplication in Hermite polynomial representation can be achieved with subquadratic space complexity. This representation enables us to find binomial or trinomial irreducible polynomials which allows us faster modular reduction over binary fields when there is no desirable such low weight irreducible polynomial in other representations. We then show that the product of two elements in Hermite polynomial representation can be performed as Toeplitz matrix-vector product. This representation is very interesting for NIST recommended binary field GF(2571) since there is no ONB for the corresponding extension. This representation can be used to obtain more efficient finite field arithmetic.

In this paper, penetration phenomenon of an early-time (E1) high altitude electromagnetic pulse (HEMP) into dispersive underground multilayer structures is analyzed using electromagnetic modeling of wave propagation in frequency dependent lossy media. The electromagnetic pulse is dealt with in the power spectrum ranging from 100kHz to the 100MHz band, considering the fact that the power spectrum of the E1 HEMP rapidly decreases 30dB below its maximum value beyond the 100MHz band. In addition, the propagation channel consisting of several dielectric materials is modeled with the dispersive relative permittivity of each medium. Based on source and channel models, the propagation phenomenon is analyzed in the frequency and time domains. The attenuation levels at a 100m underground point are observed to be about 15 and 20dB at 100kHz and 1MHz, respectively, and the peak level of the penetrating electric field is found 5.6kV/m. To ensure the causality of the result, we utilize the Hilbert transform.

Sparse representation has been studied within the field of signal processing as a means of providing a compact form of signal representation. This paper introduces a sparse representation based framework named Sparse Probabilistic Linear Discriminant Analysis in speaker recognition. In this latent variable model, probabilistic linear discriminant analysis is modified to obtain an algorithm for learning overcomplete sparse representations by replacing the Gaussian prior on the factors with Laplace prior that encourages sparseness. For a given speaker signal, the dictionary obtained from this model has good representational power while supporting optimal discrimination of the classes. An expectation-maximization algorithm is derived to train the model with a variational approximation to a range of heavy-tailed distributions whose limit is the Laplace. The variational approximation is also used to compute the likelihood ratio score of all trials of speakers. This approach performed well on the core-extended conditions of the NIST 2010 Speaker Recognition Evaluation, and is competitive compared to the Gaussian Probabilistic Linear Discriminant Analysis, in terms of normalized Decision Cost Function and Equal Error Rate.

Recently, it has been shown that electromagnetic radiation from electrical devices leaks internal information. Some investigations have shown that information leaks through the clock frequency and higher harmonic waves. Thus, previous studies have focused on the information leakage from information processing circuits. However, there has been little discussion about information leaks from peripheral circuits. In this paper, we focus on the oscillation frequency of the integrated RC oscillators. In this paper, we use a keyboard as a device that includes a RC oscillator. Then experiments observed information leaks caused by key inputs. Our experiments show that frequency fluctuations cause information leakages and clarify what information can be acquired from the fluctuation. Then, we investigate the possibility of information leaking from peripheral circuits through modulated signals which are radiated by the peripheral circuits.