The string analysis is a static analysis of dynamically generated strings in a target program, which is applied to check well-formed string construction in web applications. The string analysis constructs a finite state automaton that approximates a set of possible strings generated for a particular string variable at a program location at runtime. A drawback in the string analysis is imprecision in the analysis result, leading to false positives in the well-formedness checkers. To address the imprecision, this paper proposes an improvement technique of the string analysis to make it perform more precise analysis with respect to input validation in web applications. This paper presents the improvement by annotations representing screening of a set of possible strings, and empirical evaluation with experiments of the improved analyzer on real-world web applications.

Cyclic Redundancy Check (CRC) is a well known error detection scheme used to detect corruption of digital content in digital networks and storage devices. Since it is a compute-intensive process which adversely affects performance, hardware acceleration using FPGAs has been tried and satisfactory performance has been achieved. However, recent extended usage of networks and storage systems require various correction capabilities for various CRC standards. Traditional hardware designs based on the LFSR (Linear Feedback Shift Register) tend to have fixed structure without such flexibility. Here, fully-adaptable CRC accelerator based on a table-based algorithm is proposed. The table-based algorithm is a flexible method commonly used in software implementations. It has been rarely implemented with the hardware, since it is believed that the operational speed is not enough. However, by using pipelined structure and efficient use of memory modules in FPGAs, it appeared that the table-based fixed CRC accelerators achieved better performance than traditional implementation. Based on the implementation, fully-adaptable CRC accelerator which eliminate the need for many non-adaptable CRC implementations is proposed. The accelerator has ability to process arbitrary number of input data and generates CRC for any known CRC standard, up to 65 bits of generator polynomial, during run-time. Further, we modify Table generation algorithm in order to decrease its space complexity from O(nm) to O(n). On Xilinx Virtex 6 LX550T board, the fully-adaptable accelerators occupy between 1 to 2% area to produce maximum of 289.8 Gbps at 283.1 MHz if BRAM is deployed, or between 1.6 - 14% of area for 418 Gbps at 408.9 MHz if tables are implemented in logic. Proposed architecture enables further expansion of throughput by increasing a number of input bits M processed at a time.

This paper deals with delay faults on clock lines assuming the launch-on-capture test. In this realistic fault model, the amount of delay at the FF driven by the faulty clock line is such that the scan shift operation can perform correctly even in the presence of a fault, but during the system clock operation, capturing functional value(s) at faulty FF(s), i.e. FF(s) driven by the clock with delay, is delayed and correct value(s) may not be captured. We developed a fault simulator that can handle such faults and using this simulator we investigate the relation between the duration of the delay and the difficulty of detecting clock delay faults in the launch-on-capture test. Next, we propose test generation methods for detecting clock delay faults that affect a single or two FFs. Experimental results for benchmark circuits are given in order to establish the effectiveness of the proposed methods.

In this letter, a novel adaptive detector that combines DFE and QRD-M is proposed for MIMO-OFDM system. QR decomposition (QRD) is commonly used in many MIMO detection algorithms. In particular, sorted QR decomposition (SQRD) is an advanced algorithm that improves MIMO detection performance. The proposed detector uses SQRD to achieve better performance. To reduce the computational complexity, the received layers of each subcarrier are ordered by using the post SNR and are detected by DFE and QRD-M detector based on the order. Therefore, the proposed detector structure is varied according to the channel state. In other words, the proposed detector achieves a good tradeoff between complexity and performance. A simulation confirms the substantial performance improvements of the proposed adaptive detector with only slightly greater complexity than the conventional detector.

Super resolution (SR) reconstruction is the process of fusing a sequence of low-resolution images into one high-resolution image. Many researchers have introduced various SR reconstruction methods. However, these traditional methods are limited in the extent to which they allow recovery of high-frequency information. Moreover, due to the self-similarity of face images, most of the facial SR algorithms are machine learning based. In this paper, we introduce a facial SR algorithm that combines learning-based and regularized SR image reconstruction algorithms. Our conception involves two main ideas. First, we employ separated frequency components to reconstruct high-resolution images. In addition, we separate the region of the training face image. These approaches can help to recover high-frequency information. In our experiments, we demonstrate the effectiveness of these ideas.

As the demand for high-throughput communications in wireless LANs (WLAN) increases, the need for expanding channel bandwidth also increases. However, the use of wider band channels results in a decrease in the number of available channels because the total available bandwidth for WLAN is limited. Therefore, if multiple access points (APs) are in proximity and the cells overlap, it is difficult for each AP to use an orthogonal channel and competition increases between APs using the same channel. Coordination of APs is one promising approach; however, it is impractical to control all APs in WLAN systems. To cope with this problem, we proposed to analyze throughput performances of a multibandwidth channel selection by the coordinating APs at Nash equilibria, which can be considered as operating points for independent channel selection by APs. To clarify the effect of coordinating APs, we assume a simple scenario where the cells of three or more APs overlap, and each AP can select multibandwidth channels to maximize their own throughput. Through game-theoretic analysis, we find that the coordinated APs are able to select channels more effectively than if each AP independently selects channels. Consequently, the total throughput of the coordinated APs at Nash equilibria is significantly improved.

We have seen a rapid increase in mobile data traffic in cellular networks, especially in densely populated areas called “hotspots.” In order to deal with this trend, heterogeneous networks (HetNet) are attracting much attention as a method of effectively accommodating such traffic increases using the Long Term Evolution (LTE)-Advanced system in the 3rd Generation Partnership Project (3GPP). This paper first presents an overview of HetNet, where various wireless nodes can be deployed over the coverage area formed by macro base stations (BSs). Next, various evaluation results are provided for HetNet, where pico BSs (“Pico-BSs”) are deployed over the coverage area of macro BSs (“Macro-BSs”). Then, this paper presents a comprehensive analysis, not only of the effect of overlaying Pico-BSs but also a detailed analyses of the techniques called “cell range expansion (CRE)” and “enhanced inter-cell interference coordination (eICIC)” for facilitating the offloading of user terminals (UEs) from Macro-BSs to Pico-BSs and mitigating interference, respectively, for both downlink and uplink. Noteworthy outcomes found through the comprehensive study are that CRE provides throughput improvements for uplinks, especially for UE connected to Pico-BSs. In addition, this paper demonstrates that CRE contributes to improving downlink throughput especially for low traffic loads. The outcome regarding eICIC is that eICIC provides improvements in total throughput, in spite of the fact that eICIC causes unfairness between UE connected to the Pico-BSs and those with Macro-BSs.

Adverse weather, such as rain or snow, can cause difficulties in the processing of video streams. Because the appearance of raindrops can affect the performance of human tracking and reduce the efficiency of video compression, the detection and removal of rain is a challenging problem in outdoor surveillance systems. In this paper, we propose a new algorithm for rain detection and removal based on both spatial and wavelet domain features. Our system involves fewer frames during detection and removal, and is robust to moving objects in the rain. Experimental results demonstrate that the proposed algorithm outperforms existing approaches in terms of subjective and objective quality.

The self-improvement of static random access memory (SRAM) cell stability by post-fabrication high-voltage stress is experimentally demonstrated and its mechanism is analyzed using 4k device-matrix-array (DMA) SRAM test element group (TEG). It is shown that the stability of unbalance cells is automatically improved by merely applying stress voltage to the VDD terminal of SRAM. It is newly found that | VTH| of the OFF-state pFETs in the SRAM cell is selectively lowered which improves the cell stability and contributes to the self-improvement.

This paper presents an independent sleep scheduling protocol for energy-efficient wireless body area networks. We designed the proposed protocol based on the IEEE 802.15.6 standard that is flexible to cover various application requirements for WBAN. The target of the proposed protocol is applications that generate aperiodic and intermittent traffic. Thus, the node providing these applications wakes up only when a new event occurs. We perform the numerical analysis and the simulation to compare the IEEE 802.15.6 without and with the independent sleep scheduling protocol. The results show that the proposed protocol increases energy-efficiency in case of large data size as well as long data occurrence interval.

In this paper, we study the problem of joint resource allocation in the two-way relay system, where a pair of multi-antenna users wish to exchange information via multi-antenna amplify-and-forward relay under orthogonal frequency-division multiplexing (OFDM) modulation. We formulate a sum-rate maximization problem subject to a limited power constraint for each user and relay. Our resource allocation strategy aims at finding the best pairing scheme and optimal power allocation over subchannels in frequency and space domains. This turns out to be a mixed integer programming problem. We then derive an asymptotically optimal solution though the Lagrange dual decomposition approach. Finally, simulation results are provided to demonstrate the performance gain of the proposed algorithms.

Recently, probabilistic topic models have been applied to various types of data, including text, and their effectiveness has been demonstrated. Latent Dirichlet allocation (LDA) is a well known topic model. Variational Bayesian inference or collapsed Gibbs sampling is often used to estimate parameters in LDA; however, these inference methods incur high computational cost for large-scale data. Therefore, highly efficient technology is needed for this purpose. We use parallel computation technology for efficient collapsed Gibbs sampling inference for LDA. We assume a symmetric multiprocessing (SMP) cluster, which has been widely used in recent years. In prior work on parallel inference for LDA, either MPI or OpenMP has often been used alone. For an SMP cluster, however, it is more suitable to adopt hybrid parallelization that uses message passing for communication between SMP nodes and loop directives for parallelization within each SMP node. We developed an MPI/OpenMP hybrid parallel inference method for LDA, and evaluated the performance of the inference under various settings of an SMP cluster. We further investigated the approximation that controls the inter-node communications, and found out that it achieved noticeable increase in inference speed while maintaining inference accuracy.

In this letter, we present a joint blind adaptive scheme to suppress inter-block interference and estimate a carrier frequency offset (CFO) in downlink OFDMA systems. The proposed scheme is a combination of a channel shortening method and a CFO estimator, both based on the carrier nulling criterion. Simulation results demonstrate the effectiveness of the proposed scheme.

To mitigate the inter-cell interference in multicell downlink systems, this letter consider the robust precoder design for multicell cooperation where the knowledge of channel state available at the base station is imperfect. Assuming that imperfect channel state information (CSI) can be exchanged among cells but with no data sharing, we investigate the worst-case performance optimization problem with bounded CSI error. Our objective is to minimize the weighted sum mean-square-error (MSE) subject to per-base-station power constraints. A distributed solution is obtained by reformulating the upper bound of MSE and exploiting the Lagrangian method for the optimal problem. Simulation results demonstrate that the proposed algorithm is robust to guarantee the worst-case sum rate performance and has lower computational complexity than the SINR-based design.

In this paper, several spiral inductors with various ground clearance structures and turns were investigated to achieve noise suppression up to the fourth harmonic (3.2 GHz) regime of DDR3-1600. Their performances were characterized in terms of their capability to effectively suppress simultaneous switching noise (SSN) in the frequency region of interest. For a wider noise suppression bandwidth, a spiral inductor with large ground clearance, which provides a high self resonance frequency (SRF) as well as high inductances, was implemented. The proposed spiral inductor exhibited good noise suppression characteristics in the frequency domain and achieved 50% voltage fluctuation reduction in the time domain, compared to the identical 4-turn spiral without pattern ground structure.

A modified modeling of residue effect on nano-electro-mechanical nonvolatile memory (NEMory) is presented for considering wet etching process. The effect of a residue under the cantilever is investigated for the optimization. The feasibility of the proposed model is investigated by finite element analysis simulations.

In this paper, we consider the XPath satisfiability problem under restricted DTDs called “duplicate free”. For an XPath expression q and a DTD D, q is satisfiable under D if there exists an XML document t such that t is valid against D and that the answer of q on t is nonempty. Evaluating an unsatisfiable XPath expression is meaningless, since such an expression can always be replaced by an empty set without evaluating it. However, it is shown that the XPath satisfiability problem is intractable for a large number of XPath fragments. In this paper, we consider simple XPath fragments under two restrictions: (i) only a label can be specified as a node test and (ii) operators such as qualifier ([]) and path union (∪) are not allowed. We first show that, for some small XPath fragments under the above restrictions, the satisfiability problem is NP-complete under DTDs without any restriction. Then we show that there exist XPath fragments, containing the above small fragments, for which the satisfiability problem is in PTIME under duplicate-free DTDs.

Reliable broadcasting in vehicular ad-hoc networks is challenging due to their unique characteristics including intermittent connectivity and various vehicular scenarios. Applications and services in intelligent transportation systems need an efficient, fast and reliable broadcasting protocol especially for safety and emergency applications. In our previous work, we have proposed DECA, a new reliable broadcasting protocol which suits such characteristics. To address the issue of various vehicular scenarios, our protocol performs beaconing to gather local density information of 1-hop neighbors and uses such information to adapt its broadcasting decision dynamically. Specifically, before broadcasting a message, a node selects a neighbor with the highest density and adds the selected neighbor's identifier to the message. Upon receiving of a broadcast message, each node checks whether or not it is the selected neighbor. If so, it is responsible for rebroadcasting the message immediately. This mechanism can raise the data dissemination speed of our protocol so that it is as fast as simple flooding. To address the issue of intermittent connectivity, identifiers of broadcast messages are added into beacons. This helps nodes to check if there are any broadcast messages that have not yet been received. In this paper, we propose DECA with a new beaconing algorithm and a new waiting timeout calculation, so-called DECA-bewa. Our new protocol can reduce redundant retransmissions and overall overhead in high density areas. The protocol performance is evaluated on the network simulator (NS-2). Simulation results show that DECA-bewa outperforms existing protocols in terms of reliability, overhead and speed of data dissemination.

We have investigated the impact of O2 annealing after SiOx deposition on the switching behavior to gain a better understanding of the resistance switching mechanism, especially the role of oxygen deficiency in the SiOx network. Although resistive random access memories (ReRAMs) with SiOx after 300 annealing sandwiched with Pt electrodes showed uni-polar type resistance switching characteristics, the switching behaviors were barely detectable for the samples after annealing at temperatures over 500. Taking into account of the average oxygen content in the SiOx films evaluated by XPS measurements, oxygen vacancies in SiOx play an important role in resistance switching. Also, the results of conductive AFM measurements suggest that the formation and disruption of a conducting filament path are mainly responsible for the resistance switching behavior of SiOx.

MIMO two-way multi-hop networks are considered in which the radio resource is fully reused in all multi-hop links to increase spectrum efficiency while the adjacent interference signals are cancelled by MIMO processing. In addition, the nodes in the multi-hop network optimize their transmit powers to mitigate the remaining overreach interference. Our main contribution in this paper is to investigate an efficient relay placement method with power allocation in such networks. We present two formulations, namely QoS-constrained optimization and SINR balancing, and solve them using a sequential geometric programming method. The proposed algorithm takes advantage of convex optimization to find an efficient configuration. Simulation results show that relay placement has an important impact on the effectiveness of power allocation to mitigate the interference. Particularly, we found that an uniform relay location is optimal only in power-limited scenarios. With optimal relay locations, significant end-to-end rate gain and power consumption reduction are achieved by SINR balancing and QoS-constrained optimization, respectively. Furthermore, the optimal number of hops is investigated in power or interference-limited scenarios.