A threshold secret sharing scheme can realize reliable delivery of important content using redundant routes through a network. Furthermore, multicast delivery of threshold secret shared content can achieve efficient resource utilization thanks to the application of multicast and network coding techniques to multiple pieces of the content. Nevertheless, a tradeoff exists between reliability and efficiency if multicast content delivery uses network coding. This paper proposes a flexible multicast delivery scheme for threshold secret shared content that can control the tradeoff between reliability and efficiency. The proposed scheme classifies all the pieces obtained from the original content into multiple groups, and each group is subjected to network coding independently. An optimization procedure is proposed for the multicast delivery scheme, which involves two different heuristic delivery route computation methods applicable to large-scale networks. Evaluation results show that the optimized multicast delivery scheme adopting an appropriate grouping method and classifying the pieces into a suitable number of groups can minimize the required link bandwidth while satisfying a specified content loss probability requirement.

The Energy-aware Multi-mode Accelerator eXtension [24],[25] (EMAX) is equipped with distributed single-port local memories and ring-formed interconnections. The accelerator is designed to achieve extremely high throughput for scientific computations, big data, and image processing as well as low-power consumption. However, before mapping algorithms on the accelerator, application developers require sufficient knowledge of the hardware organization and specially designed instructions. They also need significant effort to tune the code for improving execution efficiency when no well-designed compiler or library is available. To address this problem, we focus on library support for stencil (nearest-neighbor) computations that represent a class of algorithms commonly used in many partial differential equation (PDE) solvers. In this research, we address the following topics: (1) system configuration, features, and mnemonics of EMAX; (2) instruction mapping techniques that reduce the amount of data to be read from the main memory; (3) performance evaluation of the library for PDE solvers. With the features of a library that can reuse the local data across the outer loop iterations and map many instructions by unrolling the outer loops, the amount of data to be read from the main memory is significantly reduced to a minimum of 1/7 compared with a hand-tuned code. In addition, the stencil library reduced the execution time 23% more than a general-purpose processor.

We propose the concept of an integrated coherent photonic wireless transmitter based on the simultaneous injection locking of two monolithically integrated distributed feedback (DFB) laser diodes (LDs) using an optical frequency comb (OFC). We characterize the basic operation of the transmitter and demonstrate that two injection-locked integrated DFB LDs are sufficiently stable to generate the carrier signal using a uni-traveling-carrier photodiode (UTC-PD) for a real-time error-free (bit error rate: BER < 10-11) coherent transmission with a data rate of 10 Gbit/s at a carrier frequency of 97 GHz. In the coherent wireless transmission, we compare the BER characteristics of the injection-locked transmitter with that of an actively phase-stabilized transmitter and show that the power penalty of 8-dB for the injection-locked transmitter is due to the RF spurious components, which can be reduced by integrating the OFC generator (OFCG) and LDs on the same chip. Our results suggest that the integration of the OFCG, DFB LDs, modulators, semiconductor optical amplifiers, and UTC-PD on the same chip is a promising strategy to develop a practical real-time ultrafast coherent millimeter/terahertz wave wireless transmitter.

This paper reviews a recent progress in terahertz wireless communications enabled by photonics technologies. After briefly summarizing transceiver configurations with electronics and photonics technologies, photonics-based approaches to achieving over 100-Gbit/s data rates are discussed. Then, some of our updated results on real-time wireless transmission experiments using discrete components are shown at data rates up to 50 Gbit/s. Finally, integration technologies are described by demonstrating latest advances in integrated optical sources and transmitters.

Up to now, broadband THz time-domain system has been developed and widely used for THz inspection system; however for many THz devices for THz band wireless communication, narrow-band system would be preferred rather than typical broadband system. In this work we established a narrowband and time-domain THz radiation and detection system and characterized uncooled microbolometer-based THz imagers using that system. The central frequency of generated narrowband THz wave was 850 GHz. This system enables simultaneous measurement of pulse energy and waveform of THz pulse using a superconducting transition edge sensor for measuring energy and electro-optic sampling for measuring THz waveform. We used this system to evaluate the performance of uncooled THz imagers; IRV-T0831 and T0832 from NEC. Noise equivalent power (NEP) of approximately 0.22 pW/Hz1/2 was achieved in case of T0832 at less than 1 THz which is lower than NEP value of previous reports.

The primitive called public key encryption with non-interactive opening (PKENO) is a class of public key encryption (PKE) with additional functionality. By using this, a receiver of a ciphertext can prove that the ciphertext is an encryption of a specified message in a publicly verifiable manner. In some situation that a receiver needs to claim that a ciphertext is NOT decrypted to a specified message, if he/she proves the fact by using PKENO straightforwardly, the real message of the ciphertext is revealed and a verifier checks that it is different from the specified message about which the receiver wants to prove. However, this naive solution is problematic in terms of privacy. Inspired by this problem, we propose the notion of disavowable public key encryption with non-interactive opening (disavowable PKENO) where, with respect to a ciphertext and a message, the receiver of the ciphertext can issue a proof that the plaintext of the ciphertext is NOT the message. Also, we give a concrete construction. Specifically, a disavowal proof in our scheme consists of 61 group elements. The proposed disavowable PKENO scheme is provably secure in the standard model under the decisional linear assumption and strong unforgeability of the underlying one-time signature scheme.

A terahertz-wave communication system directly connected to an optical fiber network is promising for application to future mobile backhaul and fronthaul links. The possible broad bandwidth in the terahertz band is useful for high-speed signal transmission as well as radio-space encapsulation to the high-frequency carrier. In both cases, the low-latency feature becomes important to enhance the throughput in mobile communication and is realized by waveform transport technology without any digital-signal-processing-based media conversion. A highly precise optical frequency comb signal generated by optical modulation and the vector signal demodulation technology adopted from advanced optical fiber communication technologies help perform modulation and demodulation with impairment compensation at just the edges of the link. Terahertz wave, radio over fiber, waveform transport, coherent detection, multilevel modulation, radio on radio.

The multiterminal hypothesis testing problem with zero-rate constraint is considered. For this problem, an upper bound on the optimal error exponent is given by Shalaby and Papamarcou, provided that the positivity condition holds. Our contribution is to prove that Shalaby and Papamarcou's upper bound is valid under a weaker condition: (i) two remote observations have a common random variable in the sense of Gácks and Körner, and (ii) when the value of the common random variable is fixed, the conditional distribution of remaining random variables satisfies the positivity condition. Moreover, a generalization of the main result is also given.

Determining an effective way to reduce computation complexity is an essential task for adaptive echo cancellation applications. Recently, a family of partial update (PU) adaptive algorithms has been proposed to effectively reduce computational complexity. However, because a PU algorithm updates only a portion of the weights of the adaptive filters, the rate of convergence is reduced. To address this issue, this paper proposes an enhanced switching-based variable step-size (ES-VSS) approach to the M-max PU least mean square (LMS) algorithm. The step-size is determined by the correlation between the error signals and their noise-free versions. Noise-free error signals are approximated according to the level of convergence achieved during the adaptation process. The approximation of the noise-free error signals switches among four modes, such that the resulting step-size is as close to its optimal value as possible. Simulation results show that when only a half of all taps are updated in a single iteration, the proposed method significantly enhances the convergence rate of the M-max PU LMS algorithm.

This paper proposes a novel matching pursuit generalized approximate message passing (MPGAMP) algorithm which explores the support of sparse representation coefficients step by step, and estimates the mean and variance of non-zero elements at each step based on a generalized-approximate-message-passing-like scheme. In contrast to the classic message passing based algorithms and matching pursuit based algorithms, our proposed algorithm saves a lot of intermediate process memory, and does not calculate the inverse matrix. Numerical experiments show that MPGAMP algorithm can recover a sparse signal from compressed sensing measurements very well, and maintain good performance even for non-zero mean projection matrix and strong correlated projection matrix.

Recently in the mobile graphic industry, ultra-realistic visual qualities with 60fps and limited power budget for GPU have been required. For graphics-heavy applications that run at 30 fps, we easily observed very noticeable flickering artifacts. Further, the workload imposed by high resolutions at high frame rates directly decreases the battery life. Unlike the recent frame rate up sampling algorithms which remedy the flickering but cause inevitable significant overheads to reconstruct intermediate frames, we propose a dynamic rendering quality scaling (DRQS) that includes dynamic rendering based on resolution changes and quality scaling to increase the frame rate with negligible overhead using a transform matrix. Further DRQS reduces the workload up to 32% without human visual-perceptual changes for graphics-light applications.

Conventional localization techniques such as triangulation and multilateration are not reliable in non-line-of-sight (NLOS) environments such as dense urban areas. Although fingerprint-based localization techniques have been proposed to solve this problem, we may face difficulties because we do not know the parameters of the illegal radio when creating the fingerprint database. This paper proposes a novel technique to localize illegal radios in an urban environment by interpolating the channel impulse responses stored as fingerprints in a database. The proposed interpolation technique consists of interpolation in the bandwidth (delay), frequency and spatial domains. A localization algorithm that minimizes the squared error criterion is employed in this paper, and the proposed technique is evaluated through Monte Carlo simulations using location fingerprints obtained from ray-tracing simulations. Results show that utilizing an interpolated fingerprint database is advantageous in such scenarios.

In this paper, we investigate the security property of RSA when some middle bits of the private key d are known to an attacker. Using the technique of unravelled linearization, we present a new attack on RSA with known middle bits, which improves a previous result under certain circumstance. Our approach is based on Coppersmith's method for finding small roots of modular polynomial equations.

The present paper introduces a novel method for the construction of a class of sequences that have a zero-correlation zone. For the proposed sequence set, both the cross-correlation function and the side lobe of the auto-correlation function are zero for phase shifts within the zero-correlation zone. The proposed scheme can generate a set of sequences of length 8n2 from an arbitrary Hadamard matrix of order n and a set of 2n trigonometric-like function sequences of length 4n. The proposed sequence construction can generate an optimal zero-correlation zone sequence set that satisfies the theoretical bound on the number of members for the given zero-correlation zone and sequence period. The auto-correlation function of the proposed sequence is equal to zero for all nonzero phase shifts. The peak factor of the proposed sequence set is √2, and the peak factor of a single trigonometric function is equal to √2. Assigning the sequences of the proposed set to a synthetic aperture ultrasonic imaging system would improve the S/N of the obtained image. The proposed sequence set can also improve the performance of radar systems. The performance of the applications of the proposed sequence sets are evaluated.

Survivability is the capability of a system to provide its services in a timely manner even after intrusion and compromise occur. In this paper, we focus on the quantitative analysis of survivability of virtual machine (VM) based intrusion tolerant system in the presence of Byzantine failures due to malicious attacks. Intrusion tolerant system has the ability of a system to continuously provide correct services even if the system is intruded. This paper introduces a scheme of the intrusion tolerant system with virtualization, and derives the success probability for one request by a Markov chain under the environment where VMs have been intruded due to a security hole by malicious attacks. Finally, in numerical experiments, we evaluate the performance of VM-based intrusion tolerant system from the viewpoint of survivability.

A conventional HMM-based speech synthesis system for Hanoi Vietnamese often suffers from hoarse quality due to incomplete F0 parameterization of glottalized tones. Since estimating F0 from glottalized waveform is rather problematic for usual F0 extractors, we propose a pitch marking algorithm where pitch marks are propagated from regular regions of a speech signal to glottalized ones, from which complete F0 contours for the glottalized tones are derived. The proposed F0 parameterization scheme was confirmed to significantly reduce the hoarseness whilst slightly improving the tone naturalness of synthetic speech by both objective and listening tests. The pitch marking algorithm works as a refinement step based on the results of an F0 extractor. Therefore, the proposed scheme can be combined with any F0 extractor.

In this paper, we propose a localization algorithm that uses the time difference of arrival (TDOA) and the angle of arrival (AOA). The problem is formulated in a hybrid linear matrix equation. TDOA and AOA measurements are used for estimating the target's position. Although it is known that the accuracy of TDOA based localization is superior to that of AOA based localization, TDOA based localization has a poor vertical accuracy in deteriorated geometrical conditions. This paper, therefore, proposes a localization algorithm in which the vertical position is estimated by AOA measurements and the horizontal position is estimated by TDOA measurement in order to achieve high location accuracy in three dimensions. In addition, the Lagrange multipliers are obtained efficiently and robustly. The simulation analysis shows that the proposed constrained linear squares (CLS) algorithm is an unbiased estimator, and that it approaches the Cramer-Rao lower bound (CRLB) when the measurement noise and the sensor's location errors are sufficiently small.

In this paper, we propose a method for designing finite impulse response (FIR) filters with canonic signed digit (CSD) coefficients using particle swarm optimization (PSO). In such a design problem, a large number of local minimums appear in an evaluation function for the optimization. An updating procedure of PSO tends to stagnate around such local minimums and thus indicates a premature convergence property. Therefore, a new framework for avoiding such a situation is proposed, in which the evaluation function is modified around the stagnation point. Several design examples are shown to present the effectiveness of the proposed method.

The conventional non-negative matrix factorization (NMF)-based speech enhancement is accomplished by updating iteratively with the prior knowledge of the clean speech and noise spectra bases. With the probabilistic estimation of whether the speech is present or not in a certain frame, this letter proposes a speech enhancement algorithm incorporating the speech presence probability (SPP) obtained via noise estimation to the NMF process. To take advantage of both the NMF-based and statistical model-based approaches, the final enhanced speech is achieved by applying a statistical model-based filter to the output of the SPP weighted NMF. Objective evaluations using perceptual evaluation of speech quality (PESQ) on TIMIT with 20 noise types at various signal-to-noise ratio (SNR) levels demonstrate the superiority of the proposed algorithm over the conventional NMF and statistical model-based baselines.

A 300-GHz hetero-generous package solution with a combination of a polyimide microstrip-to-waveguide transition on low-temperature co-fired ceramic (LTCC) is presented. To assemble three parts — a metal back-short, polyimide transition, and LTCC substrate integrated waveguide (SIW) — a ridged microstructure beside the microstrip probe was implemented to reduce the air gap on the broadwall of a back-short. A back-to-back transition exhibited an insertion loss of 4.4 dB at 300 GHz and 49-GHz bandwidth with less than a 10-dB return loss. By evaluating loss of the microstrip line and SIW, we estimated the loss for a single transition, which was 0.9 dB at 300 GHz. The probe transition with ridged metal successfully suppressed the unwanted dip in transmission characteristics and eased the difficulty in assembly. The compact transition is easy to integrate in an antenna-in-package with an MMIC chip by combining suitable substrate materials for the transition and package.