The impact and benefits of channel state information (CSI) are analyzed in terms of degrees-of-freedom (DoFs) in a K-user interference network operating over time-selective channels, where the error variance of CSI estimation is assumed to scale with an exponent of the received signal-to-noise ratio (SNR). The original interference alignment (IA) scheme is used with a slight modification in the network. Then, it is shown that the DoFs promised by the original IA can be fully achieved under the condition that the CSI quality order, represented as a function of the error variance and the SNR, is greater than or equal to 1. Our result is extended to the case where the number of communication pairs, K, scales with the SNR, i.e., infinite K scenario, by introducing the user scaling order. As a result, this letter provides vital information to the system designer in terms of allocating training resources for channel estimation in practical cellular environments using IA.

We show measurement results of variation-tolerance of an error-hardened dual-modular-redundancy flip-flop fabricated in a 65-nm process. The proposed error-hardened FF called BCDMR is very strong against soft errors and also robust to process variations. We propose a shift-register-based test structure to measure variations. The proposed test structure has features of constant pin count and fast measurement time. A 65 nm chip was fabricated including 40k FFs to measure variations. The variations of the proposed BCDMR FF are 74% and 55% smaller than those of the conventional BISER FF on the twin-well and triple-well structures respectively.

In this paper, we propose a hybrid test application in partial skewed-load (PSL) scan design. The PSL scan design in which some flip-flops (FFs) are controlled as skewed-load FFs and the others are controlled as broad-side FFs was proposed in [1]. We notice that the PSL scan design potentially has a capability of two test application modes: one is the broad-side test mode, and the other is the hybrid test mode which corresponds to the test application considered in [1]. According to this observation, we present a hybrid test application of the two test modes in the PSL scan design. In addition, we also address a way of skewed-load FF selection based on propagation dominance of FFs in order to take advantage of the hybrid test application. Experimental results for ITC'99 benchmark circuits show that the hybrid test application in the proposed PSL scan design can achieve higher fault coverage than the design based on the skewed-load FF selection [1] does.

The purpose of this paper is to present the static and dynamic characteristics and a smart design approach for the digital PID control forward type multiple-output dc-dc converter. The central problem of a smart design approach is how to decide the integral coefficient. Since the integral coefficient decision depends on the static characteristics, whatever integral coefficient is selected will not be yield superior dynamic characteristics. Accordingly, it is important to identify the integral coefficient that optimizes static as well as dynamic characteristics. In proposed design approach, it set the upper and lower of input voltage and output current of regulation range. The optimal integral coefficient is decided by the regulation range of the static characteristics and the dynamic characteristics and then the smart design approach is summarized. As a result, the convergence time is improved 50% compared with the conventional designed circuit.

In Long-Term Evolution (LTE)-Advanced, a heterogeneous network in which femtocells and picocells overlay macrocells is being extensively discussed in addition to traditional well-planned macrocell deployment to improve further the system throughput. In heterogeneous network deployment, cell selection as well as inter-cell interference coordination (ICIC) is very important to improve the system and cell-edge throughput. Therefore, this paper investigates three cell selection methods associated with ICIC in heterogeneous networks in the LTE-Advanced downlink: Signal-to-interference plus noise power ratio (SINR)-based cell selection, reference signal received power (RSRP)-based cell selection, and reference signal received quality (RSRQ)-based cell selection. The results of simulations (4 picocells and 25 sets of user equipment are uniformly located within 1 macrocell) that assume a full buffer model show that the downlink cell and cell-edge user throughput levels of RSRP-based cell selection are degraded by approximately 2% and 11% compared to those for SINR-based cell selection under the condition of maximizing the cell-edge user throughput due to the impairment of the interference level. Furthermore, it is shown that the downlink cell-edge user throughput of RSRQ-based cell selection is improved by approximately 5%, although overall cell throughput is degraded by approximately 6% compared to that for SINR-based cell selection under the condition of maximizing the cell-edge user throughput.

The digital logic rewiring technique has been shown to be one of the most powerful logic transformation methods. It has been proven that rewiring is able to further improve some already excellent results on many EDA problems, ranging from logic minimization, partitioning, FPGA technology mappings to final routings. Previous studies have shown that ATPG-based rewiring is one of the most powerful tools for logic perturbation while a graph-based rewiring engine is able to cover nearly one fifth of the target wires with 50 times runtime speedup. For some problems that only require good-enough and very quick solutions, this new rewiring technique may serve as a useful and more practical alternative. In this work, essential elements in graph-based rewiring such as rewiring patterns, pattern size and locality, etc., have been studied to understand their relationship with rewiring performance. A structural analysis on the target-alternative wire pairs discovered by ATPG-based and graph-based engines has also been conducted to analyze the structural characteristics that favor the identification of alternative wires. We have also developed a hybrid rewiring approach that can take the advantages from both ATPG-based and graph-based rewiring. Experimental results suggest that our hybrid engine is able to achieve about 50% of alternative wire coverage when compared with the state-of-the-art ATPG-based rewiring engine with only 4% of the runtime. Through applying our hybrid rewiring approach to the FGPA technology mapping problem, we could achieve similar depth level and look-up table number reductions with much shorter runtime. This shows that the fast runtime of our hybrid approach does not sacrifice the quality of certain rewiring applications.

In this study, we propose a one dimensional (1D) based successive generalized sidelobe canceller (GSC) structure for the implementation of 2D adaptive beamformers using a uniform rectangular antenna array (URA). The proposed approach takes advantage of the URA feature that the 2D spatial signature of the receive signal can be decomposed into an outer product of two 1D spatial signatures. The 1D spatial signatures lie in the column and the row spaces of the receive signal matrix, respectively. It follows that the interferers can be successively eliminated by two rounds of 1D-based GSC structure. As compared to the conventional 2D-GSC structure, computer simulations show that in addition to having significantly low computational complexity, the proposed adaptive approach possesses higher convergence rate.

The description and analysis of emergence in complex adaptive system has recently become a topic of great interest in the field of systems, and lots of ideas and methods have been proposed. A Sign-based model of Stigmergy is proposed in this paper. Stigmergy is widely used in complex systems. We pick up “Sign” as a key notion to understand it. A definition of “Sign” is given, which reveals the Sign's nature and exploit the significations and relationships carried by the “Sign”. Then, a Sign-based model of Stigmergy is consequently developed, which captures the essential characteristics of Stigmergy. The basic architecture of Stigmergy as well as its constituents are presented and then discussed. The syntax and operational semantics of Stigmergy configurations are given. We illustrate the methodology of analyzing emergence in CAS by using our model.

We have previously proposed a howling canceller which cancels howling by using a cascade notch filter designed from a distance between a loudspeaker and a microphone. This method utilizes a pilot signal to estimate the distance. In this paper, we introduce two methods into the distance-based howling canceller to improve speech quality. The first one is an adaptive cascade notch filter which adaptively adjusts the nulls to eliminate howling and to keep speech components. The second one is a silent pilot signal whose frequencies exist in the ultrasonic band, and it is inaudible while on transmission. We implement the proposed howling canceller on a DSP to evaluate its capability. The experimental results show that the proposed howling canceller improves speech quality in comparison to the conventional one.

EMV signature is one of specifications for authenticating credit and debit card data, which is based on ISO/IEC 9796-2 signature scheme. At CRYPTO 2009, Coron, Naccache, Tibouchi, and Weinmann proposed a new forgery attack against the signature ISO/IEC 9796-2 (CNTW attack) [2]. They also briefly discussed the possibility when the attack is applied to the EMV signatures. They showed that the forging cost is $45,000 and concluded that the attack could not forge them for operational reason. However their results are derived from not fully analysis under only one condition. The condition they adopt is typical case. For security evaluation, fully analysis and an estimation in worst case are needed. This paper shows cost-estimation of CNTW attack against EMV signature in detail. We constitute an evaluate model and show cost-estimations under all conditions that Coron et al. do not estimate. As results, this paper contribute on two points. One is that our detailed estimation reduced the forgery cost from $45,000 to $35,200 with same condition as [2]. Another is to clarify a fact that EMV signature can be forged with less than $2,000 according to a condition. This fact shows that CNTW attack might be a realistic threat.

In non-cooperative scenarios, the estimation of direct sequence spread spectrum (DS-SS) signals has to be done in a blind manner. In this letter, we consider the spreading sequence estimation problem for DS-SS signals. First, the maximum likelihood estimate (MLE) of spreading sequence is derived, then a semidefinite relaxation (SDR) approach is proposed to cope with the exponential complexity of performing MLE. Simulation results demonstrate that the proposed approach provides significant performance improvements compared to existing methods, especially in the case of low numbers of data samples and low signal-to-noise ratio (SNR) situations.

In this letter, a novel physical layer signaling transmission scheme is proposed, where the signaling information is conveyed by a pair of training sequences located in the odd and even subcarriers of an orthogonal frequency division multiplexing (OFDM) training symbol. At the receiver side, only a single correlator is required to detect the signaling information. Computer simulations verify the proposed signaling could outperform the S1 signaling and achieve similar robustness as the S2 signaling of the DVB-T2 standard.

A new direction of arrival (DOA) estimation method is introduced with arbitrary array geometry when uncorrelated and coherent signals coexist. The DOAs of uncorrelated signals are first estimated via subspace-based high resolution DOA estimation technique. Then a matrix that only contains the information of coherent signals can be formulated by eliminating the contribution of uncorrelated signals. Finally a subspace block sparse reconstruction approach is taken for DOA estimations of the coherent signals.

This paper presents a low-power FPGA based on mixed synchronous/asynchronous design. The proposed FPGA consists of several sections which consist of logic blocks, and each section can be used as either a synchronous circuit or an asynchronous circuit according to its workload. An asynchronous circuit is power-efficient for a low-workload section since it does not require the clock tree which always consumes the power. On the other hand, a synchronous circuit is power-efficient for a high-workload section because of its simple hardware. The major consideration is designing an area-efficient synchronous/asynchronous hybrid logic block. This is because the hardware amount of the asynchronous circuit is about double that of the synchronous circuit, and the typical implementation wastes half of the hardware in synchronous mode. To solve this problem, we propose a hybrid logic block that can be used as either a single asynchronous logic block or two synchronous logic blocks. The proposed FPGA is fabricated using a 65-nm CMOS process. When the workload of a section is below 22%, asynchronous mode is more power-efficient than synchronous mode. Otherwise synchronous mode is more power-efficient.

In this paper, a novel visual signal reliability (VSR) measure is proposed to consider video degradation at the signal level in audio-visual speaker identification (AVSI). The VSR estimation is formulated using a~ Gaussian fuzzy membership function (GFMF) to measure lighting variations. The variance parameters of GFMF are optimized in order to maximize the performance of the overall AVSI. The experimental results show that the proposed method outperforms the score-based reliability measuring technique.

A low-power low-noise intermediate-frequency (IF) circuit is proposed for Gaussian frequency shift keying (GFSK) low-IF receivers. The proposed IF circuit is realized by an all-analog architecture composed of a couple of limiting amplifiers (LAs) and received signal strength indicators (RSSIs), a couple of band-pass filters (BPFs), a frequency detector (FD), a low-pass filter (LPF) and a slicer. The LA and RSSI are realized by an optimized combination of folded amplifiers and current subtractor based rectifiers to avoid the process induced depressing on accuracy. In addition, taking into account the nonlinearity and static current of rectifiers, we propose an analytical model as an accurate approximation of RSSIs' transfer character. An active-RC based GFSK demodulation scheme is proposed, and then both low power consumption and a large dynamic range are obtained. The chip is implemented with HJTC 0.18 µm CMOS technology and measured under an intermediate frequency of 200 kHz, a data rate of 100 kb/s and a modulation index of 1. The RSSI has a dynamic range of 51 dB with a logarithmic linearity error of less than 1 dB, and the slope is 23.9 mV/dB. For 0.1% bit error ratio (BER), the proposed IF circuit has the minimum input signal-to-noise ratio (SNR) of 5 dB and an input dynamic range of 55.4 dB, whereas it can tolerate a frequency offset of -3%+9.5% at 6 dB input SNR. The total power consumption is 5.655.89 mW.

This paper deals with underwater target classification using synthesized active sonar signals. Firstly, we synthesized active sonar returns from a 3D highlight model of underwater targets using the ray tracing algorithm. Then, we applied a multiaspect target classification scheme based on a hidden Markov model to classify them. For feature extraction from the synthesized sonar signals, a matching pursuit algorithm was used. The experimental results depending on the number of observations and signal-to-noise ratios are presented with our discussions.

This paper presents and evaluates a new acoustic imaging system that uses multicarrier signals for correlation division in synthetic transmit aperture (CD-STA). CD-STA is a method that transmits uncorrelated signals from different transducers simultaneously to achieve high-speed and high-resolution acoustic imaging. In CD-STA, autocorrelations and cross-correlations in transmitted signals must be suppressed because they cause artifacts in the resulting images, which narrow the dynamic range as a consequence. To suppress the correlation noise, we had proposed to use multicarrier signals optimized by a genetic algorithm. Because the evaluation of our proposed method was very limited in the previous reports, we analyzed it more deeply in this paper. We optimized three pairs of multicarrier waveforms of various lengths, which correspond to 5th-, 6th- and 7th-order M-sequence signals, respectively. We built a CD-STA imaging system that operates in air. Using the system, we conducted imaging experiments to evaluate the image quality and resolution of the multicarrier signals. We also investigated the ability of the proposed method to resolve both positions and velocities of target scatterers. For that purpose, we carried out an experiment, in which both moving and fixed targets were visualized by our system. As a result of the experiments, we confirmed that the multicarrier signals have lower artifact levels, better axial resolution, and greater tolerance to velocity mismatch than M-sequence signals, particularly for short signals.

In the received signal strength-based ranging algorithms, distance is estimated from a path loss model, in which the path loss exponent is considered a key parameter. The conventional RSS-based algorithms generally assume that the path loss exponent is known a priori. However, this assumption is not acceptable in the real world because the channel condition depends on the current wireless environment. In this paper, we propose an accurate estimation method of the path loss exponent that results in minimizing distance estimation errors in varying environments. Each anchor node estimates the path loss exponent for its transmission coverage by the sequential rearrangement of the received signal strengths of all sensor nodes within its coverage. Simulation results show that the proposed method can accurately estimate the actual path loss exponent without any prior knowledge and provides low distance estimation error.

This letter presents a performance evaluation of wireless communications applicable into a capsule endoscope. A numerical model to describe the received signal strength (RSS) radiated from a capsule-sized signal generator is derived through measurements in which a liquid phantom is used that has electrical constants equivalent to human tissue specified by IEC 62209-1. By introducing this model and taking into account the characteristics of its direction pattern of the capsule and propagation distance between the implanted capsule and on-body antenna, a cumulative distribution function (CDF) of the received SNR is evaluated. Then, simulation results related to the error ratio in the wireless channel are obtained. These results show that the frequencies of 611 MHz or lesser would be useful for the capsule endoscope applications from the view point of error rate performance. Further, we show that the use of antenna diversity brings additional gain to this application.