Orthogonal frequency division multiplexing (OFDM) has been attracting much attention because of its robustness against frequency selective fading. Instead of well-known cyclic prefix (CP) insertion, known training sequence (TS) insertion can be used for OFDM block transmission (called TS-OFDM). In this paper, we propose a new receiver design, which can obtain the frequency diversity gain through the use of frequency-domain equalization (FDE) for TS-OFDM. A conditional bit error rate (BER) analysis of the proposed FDE is presented. The average BER performance of the TS-OFDM signal transmission in a frequency-selective Rayleigh fading channel is evaluated by the Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Numerical and computer simulation results show the proposed TS-OFDM with FDE improves BER and throughput performance of TS-OFDM compared to the conventional TS-OFDM receiver due to the frequency diversity gain. It is also shown that the proposed TS-OFDM with FDE is more robust against imperfect channel estimation than the conventional TS-OFDM receiver.

A compact 120-GHz-band finline orthomode transducer (OMT) with high isolation between orthogonal ports (Iop) was designed and fabricated for bidirectional wireless data transmission with polarization multiplexing. To achieve high Iop, finline OMTs normally use a resistive card to decrease unwanted resonance, that occurs on the finline, but adding a resistive card complicates the fabrication process and raises the cost of fabrication. Our proposed finline OMT uses an improved finline design in which the resonance frequency is controlled in order to expel unwanted resonance from the operation bandwidth of the 120-GHz-band wireless link. The proposed finline design enables high Iop without using a resistive card, which simplifies the fabrication process and lowers the cost of fabrication. A square horn antenna, which is attached to the finline OMT, is also designed to suppress unwanted polarization rotation of reflected waves, which further improves Iop. The proposed finline OMT has a transmission loss of less than 1.2dB, return loss of more than 12dB, cross polarization discrimination of more than 30dB, and Iop of more than 50dB across the entire occupied bandwidth of the 120-GHz-band wireless link. These characteristics are sufficient not only for 10-Gbit/s bidirectional data transmission but also for 20-Gbit/s unidirectional 2-ch data transmission by polarization-multiplexing.

A method for efficiently estimating the time-varying spectra of nonstationary autoregressive (AR) signals is derived using an indefinite matrix-based sliding window fast linear prediction (ISWFLP). In the linear prediction, the indefinite matrix plays a very important role in sliding an exponentially weighted finite-length window over the prediction error samples. The resulting ISWFLP algorithm successively estimates the time-varying AR parameters of order N at a computational complexity of O(N) per sample. The performance of the AR parameter estimation is superior to the performances of the conventional techniques, including the Yule-Walker, covariance, and Burg methods. Consequently, the ISWFLP-based AR spectral estimation method is able to rapidly track variations in the frequency components with a high resolution and at a low computational cost. The effectiveness of the proposed method is demonstrated by the spectral analysis results of a sinusoidal signal and a speech signal.

In this paper, an efficient method to reduce computational complexity for pedestrian detection is presented. Since trilinear interpolation is not used, the amount of required operations for histogram of oriented gradient (HOG) feature calculation is significantly reduced. By calculating multi-scale HOG features with integral HOG in a two-stage approach, both high detection rate and speed are achieved in the proposed method.

Traditional face swapping technologies require that the faces of source images and target images have similar pose and appearance (usually frontal). For overcoming this limit in applications this paper presents a pose-free face swapping method based on personalized 3D face modeling. By using a deformable 3D shape morphable model, a photo-realistic 3D face is reconstructed from a single frontal view image. With the aid of the generated 3D face, a virtual source image of the person with the same pose as the target face can be rendered, which is used as a source image for face swapping. To solve the problem of illumination difference between the target face and the source face, a color transfer merging method is proposed. It outperforms the original color transfer method in dealing with the illumination gap problem. An experiment shows that the proposed face reconstruction method is fast and efficient. In addition, we have conducted experiments of face swapping in a variety of scenarios such as children's story book, role play, and face de-identification stripping facial information used for identification, and promising results have been obtained.

In cognitive radio systems using TV white space, it is desirable to secure a control channel to exchange the wireless network control information and to secure minimum frequency resource for secondary user communications if TV white space is unavailable. In order to satisfy these requirements, this paper proposes guard band utilization, which aggregates the multiple guard bands between digital TV signals and uses them for a control channel and/or a communication channel. To investigate the feasibility of the proposed scheme, this paper evaluates the performance degradation of the digital TV signals when the guard band is used. Furthermore, it discusses the permissible transmitting power and occupied bandwidth of the guard band signals to avoid the harmful interference to the digital TV signals.

2-time slot cooperative relay can be used to increase the cell-edge throughput. Adaptive data modulation further improves the throughput. In this paper, we introduce adaptive modulation to single-carrier (SC) cooperative decode-and-forward (DF) relay. The best modulation combination for mobile-terminal (MT)-relay station (RS) and RS-base station (BS) links is determined for the given local average signal-to-noise power ratios (SNRs) of MT-BS, MT-RS and RS-BS links. According to the modulation combination, the ratio of time slot length of the MT-RS link (first time slot) and the RS-BS link (second time slot) is changed. It is shown by computer simulation that the use of adaptive modulation can achieve higher throughput than fixed modulation and reduces by about 9dB the required normalized total transmit SNR for a 10%-outage throughput of 0.8 bps/Hz compared to direct transmission.

In this paper, an effective per-antenna successive signal-to-leakage-plus-noise-ratio (PA-SSLNR) based precoding is proposed for multi-user multiple-input multiple-output (MIMO) broadcast channel. The signal-to-leakage-plus-noise-ratio (SLNR) of per-antenna is calculated only using the unknown leakages and the known leakages are cancelled at the transmit side by Tomlinson-Harashima Precoding (THP). The proposed scheme is different from per-user SSLNR. It does not need QR decomposition. The proposed precoding scheme is further improved by ordering antennas. Simulation results show that the proposed schemes exhibit a considerable bit error rate (BER) improvement over conventional SLNR scheme.

This paper presents an experimental evaluation of an ocean wave remote sensing system that uses bistatic GPS signal reflection to estimate wave characteristics. In our previous paper, a bistatic ocean wave remote sensing system by GPS was proposed to estimate the characteristics of sea swell near a harbor, and was also evaluated by numerical simulations. In the next phase, a prototype system has been developed and some basic experiments have been carried out in a coastal area in order to evaluate the system experimentally. In this paper, we will outline the prototype system. The system mainly consists of an array antenna, a front-end, and an estimator for ocean wave characteristics. Next, we explain that the estimator for ocean wave characteristics can identify each signal reflected from the ocean waves. Finally, the experiments show that the prototype system can receive the reflected signals from the sea-surface near the coast, and estimate the wave period and wavelength in the direction of the array antenna.

We propose a 2 × 2 space-time block code based on a trace criterion for 64-quadrature amplitude modulation (QAM). We introduce a method to easily calculate the trace norm of a space-time code for 64-QAM, and propose a new space-time code searched by this method. The error rate performance of the proposed code is compared with that of the Alamouti code. By comparison of the theoretical upper bounds, the proposed space-time code is better than the Alamouti code, when the number of receiving antennas is more than one. Moreover, bit error rate performance of the proposed code is compared with maximum likelihood decoding on perfect channel state information Rayleigh fading channels by computer simulations. These results show the proposed code almost outperforms the Alamouti code when the number of receive antennas is more than one, and the increased number of receiving antennas with our code is a decided advantage.

Multi-stage splitter configurations are often utilized in passive optical network (PON) systems to effectively accommodate widely-dispersed users. This paper introduces two types of more effective user accommodation approaches that place bidirectional optical amplifiers in several branches of the splitter inside the central office (CO); it allows a single optical line terminal (OLT) to support the coexistence of normal- and extended-distance areas and also the sharing by large numbers of optical network units (ONUs). To ease the issue of amplified spontaneous emission (ASE) noise, which is inherent in these system configurations, we propose to use a semiconductor optical amplifier (SOA)-based burst-mode optical amplifier with a fast automatic level control (ALC) circuit for upstream amplification.

In this study, a new method for Decode-Distributed Beamforming (D-DB) relaying is proposed. Each relay node decodes the source symbol by maximum likelihood detection. The detected symbol is entered into the stored Quantized Equal-gain (QE) codebook, where the label of the phase region is provided by a feedback link from the destination node. Therefore, the proposed relay network forms a Decode-Distributed QE (D-DQE) relay network. The performances of the D-DQE codebooks are examined by Monte-Carlo simulations, in which the feedback links and channel estimations are assumed to be error-free. The simulation results reveal that the symbol error rates of the D-DQE relay system improve the error performance of the QE codebooks when relay nodes are close to the source node. When error-free feedback bits are provided, the performance of the proposed D-DQE is better than that of Alamouti's Decode-Distributed Space-Time Coding (D-DSTC) relay network. The weakest relays are rejected to improve the performance of the D-DQE codebooks and reduce the number of feedback bits. This relay network is called Decode-Relay Rejection for Distributed Beamforming (D-RRDB) relay networks.

This letter presents a new image quality metric using low order discrete orthogonal moments. The moment features are extracted in a block manner and the relative moment differences (RMD) are computed. A new exponential function based on RMD is proposed to generate the quality score. The performance of the proposed method is evaluated on public databases. Experimental results and comparisons demonstrate the efficiency of the proposed method.

Recently, Yuan et al. (IEEE Infocom'13, pp.2652-2660) proposed an efficient secure nearest neighbor (SNN) search scheme on encrypted cloud database. Their scheme is claimed to be secure against the collusion attack of query clients and cloud server, because the colluding attackers cannot infer the encryption/decryption key. In this letter, we observe that the encrypted dataset in Yuan's scheme can be broken by the collusion attack without deducing the key, and present a simple but powerful attack to their scheme. Experiment results validate the high efficiency of our attacking approach. Additionally, we also indicate an upper bound of collusion-resistant ability of any accurate SNN query scheme.

This paper introduces a comparison of three automatic gait generation methods for quadruped robots: GA (Genetic Algorithm), GP (genetic programming) and CPG (Central Pattern Generator). It aims to provide a useful guideline for the selection of gait generation methods. GA-based approaches seek to optimize paw locus in Cartesian space. GP-based techniques generate joint trajectories using regression polynomials. The CPGs are neural circuits that generate oscillatory output from an input coming from the brain. Optimizations for the three proposed methods are executed and analyzed using a Webots simulation of the quadruped robot built by Bioloid. The experimental comparisons and analyses provided herein will be an informative guidance for research of gait generation method.

A fast and accurate architecture exploration for high performance and low energy VLIW data-path is proposed. The main contribution is a method to find Pareto optimal FU structures, i.e., the optimal number of FUs and the best instruction assignment for each FU. The proposed architecture exploration method is based on GA and enables the effective exploration of vast solution space. Experimental results showed that proposed method was able to achieve fast and accurate architecture exploration. For most cases, the estimation error was less than 1%.

Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems, and communication systems as they have efficient encoding and decoding algorithms compared with the linear block codes. The objective of this letter is to present a new family of ternary cyclic codes with parameters [3m-1,3m-1-2m,4], where m is an odd integer. The proposed cyclic codes are optimal in the sense that their parameters meet the Sphere Packing bound.

This paper presents the design and proof-of-concept validation of a novel network-assisted spectrum coordination (NASCOR) service for improved radio coexistence in future shared spectrum bands. The basic idea is to create an overlay network service for dissemination of spectrum usage information between otherwise independent radio devices and systems, enabling them to implement decentralized spectrum coexistence policies that reduce interference and improve spectrum packing efficiency. The proposed method is applicable to unlicensed band and shared spectrum systems in general (including femtocells), but is particularly relevant to emerging TV white spaces and cognitive radio systems which are still in need of scalable and accurate solutions for both primary-to-secondary and secondary-to-secondary coordination. Key challenges in enabling a network layer spectrum coordination service are discussed along with the description of our system architecture and a detailed case-study for a specific example of spectrum coordination: client-AP association optimization in dense networks. Performance gains are evaluated through large-scale simulations with multiple overlapping networks, each consisting of 15-35 access points and 50-250 clients in a 0.5×0.5 sq.km. urban setting. Results show an average of 150% improvement in random deployments and upto 7× improvements in clustered deployments for the least-performing client throughputs with modest reductions in the mean client throughputs.

In this paper, we present a new four parameter estimator of sampled sinusoidal signals that does not require iteration. Mathematically, the four parameters (frequency, phase, magnitude, and dc offset) of sinusoidal signals can be obtained when four data points are given. In general, the parameters have to be calculated with iteration since the equations are nonlinear. In this paper, we point out that the four parameters can be obtained analytically if the four data points given are measured using a fixed sampling interval. Analytical expressions for the four parameters are derived using the signal differences. Based on this analysis, we suggest an algorithm of estimating the four parameters from N data samples corrupted by noise without iteration. When comparing with the IEEE-1057 method which is based on the least-square method, the proposed algorithm does not require the initial guess of the parameters for iteration and avoid the convergence problem. Also, the number of required numerical operations for estimation is fixed if N is determined. As a result, the processing time of parameter estimation is much faster than the least-square method which has been confirmed by numerical simulations. Simulation results and the quantitative analysis show that the estimation error of the estimated parameters is less than 1.2 times the square root of the Cramer-Rao bounds when the signal to noise ratio is larger than 20dB.

In this letter, we present an efficient video matching-based denoising method. Two main issues are addressed in this paper: the matched points and the denoising algorithm based on an adaptive spatial temporal filter. Unlike previous algorithms, our method adaptively selects reference pixels within spatially and temporally neighboring frames. Our method uses more information about matched pixels on neighboring frames than other methods. Therefore, the proposal enhanced the accuracy of video denoising. Simulation results show that the proposed method produces cleaner and sharper images.