This paper proposes a circular bit-vector-mismatches (CBVM) algorithm for approximate circular string matching with k-mismatches. We develop the proposed CBVM algorithm based on the rotation feature of the circular pattern. By reusing the matching information of the previous substring, the next substring of the input string can be processed in parallel.

Majority logic is quite important for various applications such as fault tolerant systems, threshold logic, spectrum spread coding, and artificial neural networks. The circuit implementation of majority logic is difficult when the number of inputs becomes large because the number of transistors becomes huge and serious delay would occur. In this paper, we propose a new majority circuit with large fan-in. The circuit is composed of ordinary CMOS transistors and the total number of transistors is approximately only 4N, where N is the total number of inputs. We confirmed a correct operation by using HSPICE simulation. The yield of the proposed circuit was evaluated with respect to N under the variations of device parameters by using Monte Carlo simulation.

NoSQL systems have become vital components to deliver big data services due to their high horizontal scalability. However, existing NoSQL systems rely on experienced administrators to configure and tune the wide range of configurable parameters for optimized performance. In this work, we present a configuration management framework for NoSQL systems, called xConfig. With xConfig, its users can first identify performance sensitive parameters and capture the tuned parameters for different workloads as configuration policies. Next, based on tuned policies, xConfig can be implemented as the corresponding configuration optimiaztion system for the specific NoSQL system. Also it can be used to analyze the range of configurable parameters that may impact the runtime performance of NoSQL systems. We implement a prototype called HConfig based on HBase, and the parameter tuning strategies for HConfig can generate tuned policies and enable HBase to run much more efficiently on both individual worker node and entire cluster. The massive writing oriented evaluation results show that HBase under write-intensive policies outperforms both the default configuration and some existing configurations while offering significantly higher throughput.

Silver electrical contacts are separated at constant speed and break arcs are generated between them in a 200V-450VDC and 10A resistive circuit. The motion of the break arcs is restricted by some surrounding alumina plates. Transverse magnetic field of a permanent magnet is applied to the break arcs. Changing the supply voltage and the height of a wall located at the upper side of the break arcs, the arc lengthening time and motion of the break arcs are investigated. As a result, the higher supply voltage causes an increase of the arc lengthening time. The arc lengthening time increases significantly when the break arcs expand into the whole of the surrounding walls.

Negative group delay characteristics can be used to improve signal-integrity performance such as equalizer for compensation of the group delay of transmission line (TL). This brief-paper newly attempts to propose a concept of the embedded Folded-Stepped Impedance Resonator (F-SIR) structure with open-stub resonator, for negative group delay and slope characteristics at high-frequency as well as low-insertion loss. The concept of the proposed TL is based on the combination of resonance and anti-resonance due to open-stub resonator in order to establish wideband negative group delay and negative slope characteristics. The proposed TL is fabricated on PCB, and then the concept is validated by measurement and simulation.

We investigate a phased array-fed dual reflector antenna applying one-dimensional beam-scanning of the center-fed type, using an elliptical aperture to provide wide area observation. The distinguishing feature of this antenna is its elliptical aperture shape, in which the aperture diameter differs between the forward satellite direction and the cross-section orthogonal to it. The shape in the plane of the forward satellite direction, which does not have a beam-scanning function, is a ring-focus Cassegrain antenna, and the shape in the plane orthogonal to that, which does have a beam-scanning function, is an imaging reflector antenna. This paper describes issues which arose during design of the elliptical aperture shape and how they were solved, and presents design results using elliptical aperture dimensions of 1600 mm × 600 mm, in which the beam width differs by more than two times in the orthogonal cross-section. The effectiveness of the antenna was verified by fabricating a prototype antenna based on the design results. Measurement results confirmed that an aperture efficiency of 50% or more could be achieved, and that a different beam width was obtained in the orthogonal plane in accordance with design values.

Wireless sensor and actuator networks (WSANs) are required to achieve both energy-efficiency and low-latency in order to prolong the network lifetime while being able to quickly respond to actuation commands transmitted based on the real-time sensing data. These two requirements are in general in a relationship of trade-off when each node operates with well-known duty-cycling modes: nodes need to make their radio interfaces (IFs) frequently active in order to promptly detect the communication requests from the other nodes. One approach to break this inherent trade-off, which has been actively studied in recent literature of wireless sensor networks (WSNs), is the introduction of wake-up receiver that is installed into each node and used only for detecting the communication requests. The main radio IF in each node is woken up only when needed, i.e., in an on-demand manner, through a wake-up message received by the wake-up receiver. In this paper, we introduce radio-on-demand sensor and actuator networks (ROD-SAN) where the concept of wake-up receiver is applied to realize on-demand WSANs. We first evaluate data collection rate, packet delivery latency, and energy-efficiency of ROD-SAN and duty-cycling modes defined in IEEE 802.15.4e by computer simulations. Then, we present our test-bed implementation of ROD-SAN including all protocols from the lowest layer of wake-up signaling to the application layer offering the functionalities of information monitoring and networked control. Finally, we show experimental results obtained through our field trial in which 20 nodes are deployed in an outdoor area with the scale of 450m × 200m. The numerical results obtained by computer simulations and experiments confirm the effectiveness of ROD-SAN to realize energy-efficient and high-response WSANs.

In this paper, we study the spectral efficiency of the uplink multi-user large-scale distributed antenna systems (DAS) with imperfect channel state information. We propose the system model of multi-user DAS and illustrate the necessity of pilot reuse. Then, we derive the sum-rate of the system under pilot contamination. Furthermore, we investigate the asymptotical performance when the number of antennas goes to infinity. To reduce the pilot contamination, we present two novel pilot assignment algorithms to improve the spectral efficiency. Finally, we evaluate our proposed strategies through extensive simulations which show that compared with random pilot reuse, the min-max algorithm shows impressive performance with low complexity.

Global navigation satellite system (GNSS) receivers equipped with the frequency domain interference suppression (FDIS) filter can operate in environments with harsh interference. The FDIS will not cause tracking error bias for an ideal analog receiver channel as its magnitude response and phase response are constant. However, the analog receiver channel distortion is induced by RF cables, amplifiers, and mixers. The distortion of the channel caused asymmetry correlation function. The correlation function is further deformed by the FDIS filter. More seriously, since the FDIS filter is adaptive, the bias will vary with the jamming pattern, especially when the frequency of interference is varying. For precision navigation applications, this bias must be mitigated. Fortunately, to prevent power loss, the analog receiver channel filter is a real function or the imaginary part is negligible. Therefore, the magnitude response and the phase response are even functions. Based on these channel features, a new FDIS filter based on mirror frequency amplitude compensation (MFAC) method is proposed in this paper. The amplitude of the symmetry position of the notch frequency is doubled in the MFAC method in order to mitigate the tracking bias. Simulation results show that the MFAC-based FDIS method is capable of reducing the bias error to less than 0.1ns, which is significant smaller than that achieved by the traditional FDIS method.

This paper considers a massive multiple-input-multiple-output (MIMO) relaying system with multi-pair single-antenna users. The relay node adopts maximum-ratio combining/maximum-ratio transmission (MRC/MRT) stratagem for reception/transmission. We analyze the spectral efficiency (SE) and power scaling laws with respect to the number of relay antennas and other system parameters. First, by using the law of large numbers, we derive the closed-form expression of the SE, based on which, it is shown that the SE per user increases with the number of relay antennas but decreases with the number of user pairs, both logarithmically. It is further discovered that the transmit power at the source users and the relay can be continuously reduced as the number of relay antennas becomes large while the SE can maintains a constant value, which also means that the energy efficiency gain can be obtained simultaneously. Moreover, it is proved that the number of served user pairs can grow proportionally over the number of relay antennas with arbitrary SE requirement and no extra power cost. All the analytical results are verified through the numerical simulations.

This paper investigates target detection, barrier coverage, and path coverage with randomly deployed sensors and analyzes the performance of target detection, barrier coverage, and path coverage using integral geometry. Explicit formulas of their performance are derived. The optimal convex sensing area shape with a power consumption constraint is derived from the explicit formulas. Surprisingly, the optimal convex sensing area for target detection in a convex surveillance area can be different from that for barrier coverage. A slender sensing area is optimal for the former, but a disk-shaped sensing area can be optimal for the latter. Similar results are obtained with the Boolean and probabilistic detection models. A slender sensing area is optimal for the Boolean detection model and one of the probabilistic detection models, whereas the disk-shaped sensing area is optimal for another probabilistic detection model. This paper also derives the most difficult path and target to be detected.

Energy harvesting wireless sensor networks (EH-WSNs) are being actively studied in order to solve the problems faced by battery-operated WSNs, namely the cost for battery replacement and the negative impact on the environment. In EH-WSNs, each node harvests ambient energy, such as light, heat, vibration, and uses it for sensing, computations, and wireless communications, where the amount of harvested energy of each node varies depending on their environments. MAC protocols for EH-WSNs need to be designed to achieve high throughput and fairness, however, the conventional MAC protocols proposed for EH-WSNs do not adapt to the harvesting rate of each node, resulting in poor fairness. In this paper, we propose a fair MAC protocol based on polling scheme for EH-WSNs. The proposed scheme adjusts contention probability of each node according to its harvesting rate, thereby increasing the throughput of nodes with low harvesting rate. We evaluate throughput and fairness of the proposed fair polling scheme by theoretical analysis and computer simulations, and show that the proposed scheme can improve fairness with little degradation of the overall network throughput.

DDoS remains a major threat to Software Defined Networks. To keep SDN secure, effective detection techniques for DDoS are indispensable. Most of the newly proposed schemes for detecting such attacks on SDN make the SDN controller act as the IDS or the central server of a collaborative IDS. The controller consequently becomes a target of the attacks and a heavy loaded point of collecting traffic. A collaborative intrusion detection system is proposed in this paper without the need for the controller to play a central role. It is deployed as a modified artificial neural network distributed over the entire substrate of SDN. It disperses its computation power over the network that requires every participating switch to perform like a neuron. The system is robust without individual targets and has a global view on a large-scale distributed attack without aggregating traffic over the network. Emulation results demonstrate its effectiveness.

In the early phases of the system development process, stakeholders exchange ideas and describe requirements in natural language. Requirements described in natural language tend to be vague and include logical inconsistencies, whereas logical consistency is the key to raising the quality and lowering the cost of system development. Hence, it is important to find logical inconsistencies in the whole requirements at this early stage. In verification and validation of the requirements, there are techniques to derive logical formulas from natural language requirements and evaluate their inconsistencies automatically. Users manually chunk the requirements by paragraphs. However, paragraphs do not always represent logical chunks. There can be only one logical chunk over some paragraphs on the other hand some logical chunks in one paragraph. In this paper, we present a practical approach to detecting logical inconsistencies by clustering technique in natural language requirements. Software requirements specifications (SRSs) are the target document type. We use k-means clustering to cluster chunks of requirements and develop semantic role labeling rules to derive “conditions” and “actions” as semantic roles from the requirements by using natural language processing. We also construct an abstraction grammar to transform the conditions and actions into logical formulas. By evaluating the logical formulas with input data patterns, we can find logical inconsistencies. We implemented our approach and conducted experiments on three case studies of requirements written in natural English. The results indicate that our approach can find logical inconsistencies.

In this paper, the integration of dynamic plant-wide optimization and distributed generalized predictive control (DGPC) is presented for serially connected processes. On the top layer, chance-constrained programming (CCP) is employed in the plant-wide optimization with economic and model uncertainties, in which the constraints containing stochastic parameters are guaranteed to be satisfied at a high level of probability. The deterministic equivalents are derived for linear and nonlinear individual chance constraints, and an algorithm is developed to search for the solution to the joint probability constrained problem. On the lower layer, the distributed GPC method based on neighborhood optimization with one-step delay communication is developed for on-line control of the whole system. Simulation studies for furnace temperature set-points optimization problem of the walking-beam-type reheating furnace are illustrated to verify the effectiveness and practicality of the proposed scheme.

A map-reduce framework is popular for big data analysis. In the typical map-reduce framework, both master node and worker nodes can use hard-disk drives (HDDs) as local disks for the map-reduce computation. However, because of the inherit mechanical problems of HDDs, the I/O performance is a bottleneck for the map-reduce framework when I/O-intensive applications (e.g., sorting) are performed. Replacing HDDs with solid-state drives (SSDs) is not economical, although SSDs have better performance than HDDs. In this paper, we propose a virtualization-based hybrid storage system for the map-reduce framework. The objective of the paper is to combine the advantages of the fast access property of SSDs and the low cost of HDDs by realizing an economical design and improving I/O performance of a map-reduce framework in a virtualization environment. We propose three storage combinations: SSD-based, HDD-based, and a hybrid of SSD-based and HDD-based storage systems which balances speed, capacity, and lifetime. According to experiments, the hybrid of SSD-based and HDD-based storage systems offers superior performance and economy.

In the near future, many sensors and terminals will be connected to the public network to provide various convenient IoT/M2M services. In order to connect many sensors to the network efficiently, wireless communication systems in the 920MHz band are seen as attractive solutions. We are focusing on the 920MHz band to research and develop high-capacity protocols that can accommodate many terminals, and low power consumption technologies for battery-driven terminals. In this paper, we describe the following three concrete wireless systems that use our proposals. (1) A physical distribution pallet management system that can handle thousands of pallet-embedded sensors and a wireless module with a battery lifetime of about ten years. (2) Water leakage monitoring system for underground pipes by using sensors and a wireless module in each valve box. (3) A wide-area and high-capacity radio relay system for smart metering services like the reading of gas meters. The radio relay system can accommodate various sensors and terminals and has large potential for providing various IoT/M2M services in conjunction with smart metering services.

Technological developments in wireless communication have led to an increasing demand for radio frequencies. This has necessitated the practice of spectrum sharing to ensure optimal usage of the limited frequencies, provided this does not cause interference. This paper presents a framework for managing an unexpected situation in which a primary user experiences harmful interference with regard to database-driven secondary use of spectrum allocated to the primary user towards 5G mobile networks, where the primary user is assumed to be a radar system. In our proposed framework, the primary user informs a database that they are experiencing harmful interference. Receiving the information, the database updates a primary exclusive region in which secondary users are unable to operate in the licensed spectrum. Subsequent to the update, this primary exclusive region depends on the knowledge about the secondary users when the primary user experiences harmful interference, knowledge of which is stored in the database. We assume a circular primary exclusive region centered at a primary receiver and derive an optimal radius of the primary exclusive region by applying stochastic geometry. Then, for each type of knowledge stored in the database for the secondary user, we evaluate the optimal radius for a target probability that the primary user experiences harmful interference. The results show that the more detailed the knowledge of the secondary user's density and transmission power stored in the database, the smaller the radius that has to be determined for the primary exclusive region after the update and the more efficient the spatial reuse of the licensed spectrum that can be achieved.

Considering an uncertain multi-objective optimization system with interval coefficients, this letter proposes an interval multi-objective particle swarm optimization algorithm. In order to improve its performance, a crowding distance measure based on the distance and the overlap degree of intervals, and a method of updating the archive based on the acceptance coefficient of decision-maker, are employed. Finally, results show that our algorithm is capable of generating excellent approximation of the true Pareto front.