We consider the problem of deciding whether a query can be rewritten by a nondeterministic view. It is known that rewriting is decidable if views are given by single-valued non-copying devices such as compositions of single-valued extended linear top-down tree transducers with regular look-ahead, and queries are given by deterministic MSO tree transducers. In this paper, we extend the result to the case that views are given by nondeterministic devices that are not always single-valued. We define two variants of rewriting: universal preservation and existential preservation, and discuss the decidability of them.

Based on the completeness of the real-valued discrete Gabor transform, a new biorthogonal relationship between analysis window and synthesis window is derived and a fast algorithm for computing the analysis window is presented for any given synthesis window. The new biorthogonal relationship can be expressed as a linear equation set, which can be separated into a certain number of independent sub-equation sets, where each of them can be fast and independently solved by using convolution operations and FFT to obtain the analysis window for any given synthesis window. Computational complexity analysis and comparison indicate that the proposed algorithm can save a considerable amount of computation and is more efficient than the existing algorithms.

MUltiple SIgnal Classification (MUSIC) is a standard technique for direction of arrival (DOA) estimation with high resolution. However, MUSIC cannot estimate DOAs accurately in the case of underdetermined conditions, where the number of sources exceeds the number of microphones. To overcome this drawback, an extension of MUSIC using cumulants called 2q-MUSIC has been proposed, but this method greatly suffers from the variance of the statistics, given as the temporal mean of the observation process, and requires long observation. In this paper, we propose a new approach for extending MUSIC that exploits higher-order moments of the signal for the underdetermined DOA estimation with smaller variance. We propose an estimation algorithm that nonlinearly maps the observed signal onto a space with expanded dimensionality and conducts MUSIC-based correlation analysis in the expanded space. Since the dimensionality of the noise subspace is increased by the mapping, the proposed method enables the estimation of DOAs in the case of underdetermined conditions. Furthermore, we describe the class of mapping that allows us to analyze the higher-order moments of the observed signal in the original space. We compare 2q-MUSIC and the proposed method through an experiment assuming that the true number of sources is known as prior information to evaluate in terms of the bias-variance tradeoff of the statistics and computational complexity. The results clarify that the proposed method has advantages for both computational complexity and estimation accuracy in short-time analysis, i.e., the time duration of the analyzed data is short.

This paper presents a novel data compression method for testing integrated circuits within the selective dictionary coding framework. Due to the inverse value of dictionary indices made use of for the compatibility analysis with the heuristic algorithm utilized to solve the maximum clique problem, the method can obtain a higher compression ratio than existing ones.

In this paper, we consider the stack layout of the bubble-sort graph. The bubble-sort graph is a type of Cayley graph on a symmetric group; the bubble-sort graph has an important role for the study of Cayley graphs as interconnection networks. The stack layout and the queue layout problem that are treated in this paper have been studied widely. In this paper, we show that the stack number of the bubble-sort graph BS(n) is either n-1 or n-2. In addition, we show that an upper bound of the queue number of BS(n) is n-2.

This paper proposes the proportional static-phase-error reduction (SPER) for the frequency-multiplier-based delay-locked-loop (DLL) architecture. The frequency multiplier (FM) can synthesize a combined clock to solve the high operational frequency of DLL. However, FM is sensitive to the static phase error of DLL. A SPER loop adopts a timing amplifier and a coarse-fine tuning technique to enhance the deterministic jitter of FM. The SPER loop proportionally reduces the static phase error and can extend the operating range of FM.

A single-flux-quantum (SFQ) arithmetic logic unit (ALU) was designed and tested to evaluate the effectiveness of introducing dynamically reconfigurable logic gates in the design of a superconducting logic circuit. We designed and tested a bit-serial SFQ ALU that can perform six arithmetic/logic functions by using a dynamically reconfigurable AND/OR gate. To ensure stable operation of the ALU, we improved the operating margin of the SFQ AND/OR gate by employing a partially shielded structure where the circuit is partially surrounded by under- and over-ground layers to reduce parasitic inductances. Owing to the introduction of the partially shielded structure, the operating margin of the dynamically reconfigurable AND/OR gate can be improved without increasing the circuit area. This ALU can be designed with a smaller circuit area compared with the conventional ALU by using the dynamically reconfigurable AND/OR gate. We implemented the SFQ ALU using the AIST 2.5kA/cm2 Nb standard process 2. We confirmed high-speed operation and correct reconfiguration of the SFQ ALU by a high-speed test. The measured maximum operation frequency was 30GHz.

This article proposes a versatile model of a multiservice queueing system with elastic traffic. The model can provide a basis for an analysis of telecommunications and computer network systems, internet network systems in particular. The advantage of the proposed approach is a possibility of a determination of delays in network nodes for a number of selected classes of calls offered in modern telecommunications networks.

One of the fundamental problems in many-pixel detectors implemented in cryogenics environments is the number of bias and read-out wires. If one targets a megapixel range detector, number of wires should be significantly reduced. One possibility is that the detectors are serially connected and biased by using only one line and read-out is accomplished by on-chip circuitry. In addition to the number of pixels, the detectors should have fast response times, low dead times, high sensitivities, low inter-pixel crosstalk and ability to respond to simultaneous irradiations to individual pixels for practical purposes. We have developed an equivalent circuit model for a serially connected superconducting strip line detector (SSLD) array together with the read-out electronics. In the model we take into account the capacitive effects due to the ground plane under the detector, effects of the shunt resistors fabricated under the SSLD layer, low pass filters placed between the individual pixels that enable individual operation of each pixel and series resistors that prevents the DC bias current flowing to the read-out electronics as well as adjust the time constants of the inductive SSLD loop. We explain the results of investigation of the following parameters: Crosstalk between the neighbor pixels, response to simultaneous irradiation, dead times, L/R time constants, low pass filters, and integration with the SFQ front-end circuit. Based on the simulation results, we show that SSLDs are promising devices for detecting a wide range of incident radiation such as neurons, X-rays and THz waves in many-pixel configurations.

Radio frequency over fiber (RoF) advanced technology is already integrated into current 3G and 4G radio access networks in which the digital unit and remote radio head equipped with nonlinear high power amplifiers (HPAs) are connected through the RoF-based fronthaul links. In this study, we investigated the degradation in the adjacent channel leakage ratio (ACLR) of equipment with the adaptive linearizer RF HPA when both the direct and feedback paths of the transmitting system include RoF links. We show that an ACLR exceeding -57dBc @ 5-MHz offset, which completely satisfies the requirements of the 3GPP technical specifications, can be achieved for a 20-W-class Doherty power amplifier linearized through commercial RoF links. Experiments showed that the achieved ACLR strongly depends on the RoF-link noise figure and that most of the nonlinear distortions caused by RoF can be completely suppressed with the proposed joint linearization approach for simultaneous linearization of RoF and HPA nonlinearities with a single common “joint” linearizer. Experimental results confirm significant ACLR performance enhancements as a result of RoF noise floor reduction, which is achieved under RoF driving conditions optimized together with joint RoF and HPA linearization. Our joint linearization approach via RoF links is confirmed to be applicable for next-generation mobile fronthaul architectures.

Coordinate interleaved orthogonal design (CIOD) using four transmit antennas provides full diversity, full rate (FDFR) properties with low decoding complexity. However, the constellation expansion due to the coordinate interleaving of the rotated constellation results in peak to average power ratio (PAPR) increase. In this paper, we propose two signal constellation design methods which have low PAPR. In the first method we propose a signal constellation by properly selecting the signal points among the expanded square QAM constellation points, based on the co-prime interleaving of the first coordinate signal. We design a regular interleaving pattern so that the coordinate distance product (CPD) after the interleaving becomes large to get the additional coding gain. In the other method we propose a novel constellation with low PAPR based on the clipping of the rotated square QAM constellation. Our proposed signal constellations show much lower PAPR than the ordinary rotated QAM constellations for CIOD.

Quantum key distribution (QKD), a cryptography technology providing information theoretic security based on physical laws, has moved from the research stage to the engineering stage. Although the communication distance is subject to a limitation attributable to the QKD fundamentals, recent research and development of “key relaying” over a “QKD network” is overcoming this limitation. However, there are still barriers to widespread use of QKD integrated with conventional information systems: applicability and development cost. In order to break down these barriers, this paper proposes a new solution for developing secure network infrastructure based on QKD technology to accommodate multiple applications. The proposed solution introduces 3 functions: (1) a directory mechanism to manage multiple applications hosted on the QKD network, (2) a key management method to share and to allocate the keys for multiple applications, and (3) a cryptography communication library enabling existing cryptographic communication software to be ported to the QKD network easily. The proposed solution allows the QKD network to accommodate multiple applications of various types, and moreover, realizes applicability to conventional information systems easily. It also contributes to a reduction in the development cost per information system, since the development cost of the QKD network can be shared between the multiple applications. The proposed solution was implemented with a network emulating QKD technology and evaluated. The evaluation results show that the proposed solution enables the infrastructure of a single QKD network to host multiple applications concurrently, fairly, and effectively through a conventional application programming interface, OpenSSL API. In addition, the overhead of secure session establishment by the proposed solution was quantitatively evaluated and compared.

Single-carrier (SC) transmission with space-time block coded (STBC) transmit diversity can achieve good bit error rate (BER) performance. However, in a high mobility environment, the STBC codeword orthogonality is distorted and as consequence, the BER performance is degraded by the interference caused by the orthogonality distortion of STBC codeword. In this paper, we proposed a novel frequency-domain equalization (FDE) for SC-STBC transmit diversity in doubly selective fading channel. Multiple FDE weight matrices, each associated with a different code block, are jointly optimized based on the minimum mean square error (MMSE) criterion taking into account not only channel frequency variation but also channel time variation over the STBC codeword. Computer simulations confirm that the proposed robust FDE achieves BER performance superior to conventional FDE, which was designed based on the assumption of a quasi-static fading.

Given a set of positive-weighted points and a query rectangle r (specified by a client) of given extents, the goal of a maximizing range sum (MaxRS) query is to find the optimal location of r such that the total weights of all points covered by r is maximized. In this paper, we address the problem of processing MaxRS queries over road network databases and propose two new external memory methods. Through a set of simulations, we evaluate the performance of the proposed methods.

In quasi-synchronous frequency-hopping multiple access (QS-FHMA) systems, relative delays are allowed to vary in a domain around the origin. Under such condition, the low hit zone (LHZ) frequency-hopping sequence (FHS) set is more propitious than the conventional FHS set to be applied by the systems. In this paper, a construction based on the interleaving techniques of FHS set with LHZ is proposed. Besides the requirement for this constructed LHZ FHS set to get the optimality or the near optimality with respect to the Peng-Fan-Lee bound is also given. It turns out that the constructed LHZ FHS set has new parameters not covered in the literature, thus it does have great significance in practice.

In recent years, multiple-input multiple-output (MIMO) channel models for crowded areas, such as indoor offices, shops, and outdoor hotspot environments, have become a topic of significant interest. In such crowded environments, propagation paths are frequently shadowed by moving objects, such as pedestrians or vehicles. These shadowing effects can cause time variations in the delay and angle-of-arrival (AoA) characteristics of a channel. In this paper, we propose a method for modeling the shadowing effects of pedestrians in a cluster-based channel model. The proposed method uses cluster power variations to model the time-varying channel properties. We also propose a novel method for estimating the cluster power variation properties from measured data. In order to validate our proposed method, channel sounding in the 3GHz band is conducted in a cafeteria during lunchtime. The results for the K parameter, delay spreads, and AoA azimuth spreads are compared for the measured data and the channel data generated using the proposed method. The results indicate that the time-varying delay-AoA characteristics can be effectively modeled using our proposed method.

A Field Programmable Sequencer and Memory (FPSM), which is a programmable unit exclusively optimized for peripherals on a micro controller unit, is proposed. The FPSM functions as not only the peripherals but also the standard built-in memory. The FPSM provides easier programmability with a smaller area overhead, especially when compared with the FPGA. The FPSM is implemented on the FPGA and the programmability and performance for basic peripherals such as the 8 bit counter and 8 bit accuracy Pulse Width Modulation are emulated on the FPGA. Furthermore, the FPSM core with a 4K bit SRAM is fabricated in 0.18µm 5 metal CMOS process technology. The FPSM is an half the area of FPGA, its power consumption is less than one-fifth.

Novel constructions of inter-group complementary (IGC) sequences are proposed based on Z-periodic complementary (ZPC) sequences and uncorrelated sequence set by taking advantages of interleaved operation. The presented methods can get IGC sequences from interleaving ZPC sequence set. The proposed methods not only can get polyphase IGC sequence set, but also can obtain binary and ternary IGC sequence set. In particular, with the aid of uncorrelated sequence, the number of available groups of IGC sequences from interleaving ZPC sequence set can be chosen with flexibility compared to the existed IGC sequences. The IGC sequences based code division multiple access (CDMA) systems may perform better on bit error rates than conventional sequences based interference-limited CDMA systems. Moreover, the novel IGC sequences may work well in both synchronous and asynchronous operational modes.

The automatic transcription of out-of-vocabulary words into their corresponding phoneme strings has been widely adopted for speech synthesis and spoken-term detection systems. By combining various methods in order to meet the challenges of grapheme-to-phoneme (G2P) conversion, this paper proposes a phoneme transition network (PTN)-based architecture for G2P conversion. The proposed method first builds a confusion network using multiple phoneme-sequence hypotheses generated from several G2P methods. It then determines the best final-output phoneme from each block of phonemes in the generated network. Moreover, in order to extend the feasibility and improve the performance of the proposed PTN-based model, we introduce a novel use of right-to-left (reversed) grapheme-phoneme sequences along with grapheme-generation rules. Both techniques are helpful not only for minimizing the number of required methods or source models in the proposed architecture but also for increasing the number of phoneme-sequence hypotheses, without increasing the number of methods. Therefore, the techniques serve to minimize the risk from combining accurate and inaccurate methods that can readily decrease the performance of phoneme prediction. Evaluation results using various pronunciation dictionaries show that the proposed model, when trained using the reversed grapheme-phoneme sequences, often outperformed conventional left-to-right grapheme-phoneme sequences. In addition, the evaluation demonstrates that the proposed PTN-based method for G2P conversion is more accurate than all baseline approaches that were tested.

This paper claims to use a new question expansion method for question classification in cQA services. The input questions consist of only a question whereas training data do a pair of question and answer. Thus they cannot provide enough information for good classification in many cases. Since the answer is strongly associated with the input questions, we try to create a pseudo answer to expand each input question. Translation probabilities between questions and answers and a pseudo relevant feedback technique are used to generate the pseudo answer. As a result, we obtain the significant improved performances when two approaches are effectively combined.