In order to obtain higher diversity gain, the use of additional resources such as time, frequency, and/or antennas are necessary. The aim of this study is to achieve adequate temporal diversity gain without needing additional resources beyond decoding delay and decoding complexity. If the channel state information (CSI) is not available at the transmitter side, the transmitter sends information at a given constant transmission rate while the channel capacity varies according to the channel state. If the instantaneous channel capacity is greater than the given transmission rate, the system can successfully transmit information but it does not exploit the entire available channel capacity. We focus on this extra channel capacity to transmit other information based on a joint network-channel coding in order to obtain higher diversity and coding gains. This paper provides the basic concept of the transmit diversity with the joint network-channel coding and investigates its performances in terms of outage probability, additional decoding delay and complexity, and frame-error rate (FER).

A method of frame synchronization between the color video and depth-map video for depth based 3D video using edge coherence is proposed. We find a synchronized pair of frames using edge coherence by computing the maximum number of overlapped edge pixels between the color video and depth-map video in regions of temporal frame difference. The experimental results show that the proposed method can be used for synchronization of depth-based 3D video and that it is robust against Gaussian noise with σ = less than 30 and video compression by H.264/AVC with QP = less than 44.

The authors have developed a mechanism that applies real vibration to electrical contacts by hammering oscillation in the vertical direction similar to that in real cases, and they have studied the effects of micro-oscillation on the contacts using the mechanism. It is shown that the performance of the hammering oscillation mechanism (HOM) for measuring acceleration and force is superior to that of other methods in terms of the stability of data. Using the mechanism, much simpler and more practical protocols are proposed for evaluating acceleration, force, and mass using only the measured acceleration. It is also indicated that the relationship between the inertial force generated by the hammering oscillation mechanism and the frictional force in electrical devices attached on a board is related to one of the causes of the degradation of electrical contacts under the effect of external micro-oscillation.

This paper introduces two schemes to put the decoding of the convolutional network code (CNC) into practice, which are named the Intermittent Packet Transmission Scheme (IPTS) and the Redundancy Packet Transmission Scheme (RPTS). According to the decoding formula of the sink nodes, we can see that, at the time k+δ in order to decode the source packet generated at time k, the sink node should know all the source packets generated before k-1. This is impractical. The two schemes we devised make it unnecessary. A construction algorithm is also given about the RPTS networks. For the two schemes, we analyze the strengths and weaknesses and point out their implemented condition.

In this paper, we point out that Yoon et al.'s gateway-oriented password-based authenticated key exchange (GPAKE) protocol is inefficiently and incorrectly designed to overcome the undetectable on-line dictionary attack. To remedy these problems, we propose a new GPAKE protocol and prove its security in the random oracle model. Performance analysis demonstrates that our protocol is more secure and efficient than previous protocols.

Wireless sensor network (WSN) using network coding is vulnerable to pollution attacks. Existing authentication schemes addressing this attack either burden the sensor node with a higher computation overhead, or fail to provide an efficient way to mitigate two recently reported attacks: tag pollution attacks and repetitive attacks, which makes them inapplicable to WSN. This paper proposes an efficient hybrid cryptographic scheme for WSN with securing network coding. Our scheme can resist not only normal pollution attacks, but the emerging tag pollution and repetitive attacks in an efficient way. In particular, our scheme is immediately suited for distributing multiple generations using a single public key. Experimental results show that our scheme can significantly improve the computation efficiency at a sensor node under the two above-mentioned attacks.

We address the problem of processing graph pattern matching queries over a massive set of data graphs in this letter. As the number of data graphs is growing rapidly, it is often hard to process such queries with serial algorithms in a timely manner. We propose a distributed graph querying algorithm, which employs feature-based comparison and a filter-and-verify scheme working on the MapReduce framework. Moreover, we devise an efficient scheme that adaptively tunes a proper feature size at runtime by sampling data graphs. With various experiments, we show that the proposed method outperforms conventional algorithms in terms of scalability and efficiency.

This paper presents a new adaptive peak-to-average power ratio (PAPR) reduction method based on clipping and filtering (CF) for precoded orthogonal frequency division multiplexing (OFDM)-multiple-input multiple-output (MIMO) transmission. While the conventional CF method adds roughly the same interference power to each of the transmission streams, the proposed method suppresses the addition of interference power to the streams with good channel conditions. Since the sum capacity is dominated by the capacity of the streams under good channel conditions and the interference caused by the PAPR reduction process severely degrades the achievable capacity for these streams, the proposed method significantly improves the achievable sum capacity compared to the conventional CF method for a given PAPR. Simulation results show the capacity gain by using the proposed method compared to the conventional method.

As the LSI process technology advances and the gate size becomes smaller, the signal delay on interconnect becomes a significant factor in the signal path delay. Also, as the size of interconnect structure becomes smaller, the interconnect process variations have become one of the dominant factors which influence the signal delay and thus clock skew. Therefore, controlling the influence of interconnect process variations on clock skew is a crucial issue in the advanced process technologies. In this paper, we propose a method for minimizing clock skew fluctuations caused by interconnect process variations. The proposed method identifies the suitable balance of clock buffer size and wire length in order to minimize the clock skew fluctuations caused by the interconnect process variations. Experimental results on test circuits of 28nm process technology show that the proposed method reduces the clock skew fluctuations by 30-92% compared to the conventional method.

This letter introduces innovative VAD based on horizontal spectral entropy with long-span of time (HSELT) feature sets to improve mobile ASR performance in low signal-to-noise ratio (SNR) conditions. Since the signal characteristics of nonstationary noise change with time, we need long-term information of the noisy speech signal to define a more robust decision rule yielding high accuracy. We find that HSELT measures can horizontally enhance the transition between speech and non-speech segments. Based on this finding, we use the HSELT measures to achieve high accuracy for detecting speech signal form various stationary and nonstationary noises.

In this letter, a distributed TDMA-based data gathering scheme for wireless sensor networks, called DTDGS, is proposed in order to avoid transmission collisions, achieve high levels of power conservation and improve network lifetime. Our study is based on corona-based network division and a distributed TDMA-based scheduling mechanism. Different from a centralized algorithm, DTDGS does not need a centralized gateway to assign the transmission time slots and compute the route for each node. In DTDGS, each node selects its transmission slots and next-hop forwarding node according to the information gathered from neighbor nodes. It aims at avoiding transmission collisions and balancing energy consumption among nodes in the same corona. Compared with previous data gathering schemes, DTDGS is highly scalable and energy efficient. Simulation results show high the energy efficiency of DTDGS.

In this paper, for an odd prime p such that p≡3 mod 4, odd n, and d=(pn+1)/(pk+1)+(pn-1)/2 with k|n, the value distribution of the exponential sum S(a,b) is calculated as a and b run through $mathbb{F}_{p^n}$. The sequence family $mathcal{G}$ in which each sequence has the period of N=pn-1 is also constructed. The family size of $mathcal{G}$ is pn and the correlation magnitude is roughly upper bounded by $(p^k+1)sqrt{N}/2$. The weight distribution of the relevant cyclic code C over $mathbb{F}_p$ with the length N and the dimension ${ m dim}_{mathbb{F}_p}mathcal{C}=2n$ is also derived.

In this paper, a method is introduced that can detect the number of incident signals (NIS) even there are fewer antennas than NIS. Previous works on NIS detection methods assumed that the number of antennas always exceeded NIS. In the DOA estimation field, the DOA estimation is possible, even if NIS exceeds the number of antennas, by extending the degrees of freedom of array (DOFA) using a modified array configuration, such as a nested array (NA). The information of NIS is required in advance to accurately estimate DOA, however, it has not been investigated deeply when NIS is larger than the number of antennas. In this paper, a NIS detection method based on the DOFA extending process using NA is proposed. One of the important issues in NIS detection is the detection metric. As one of the simple metrics, the ratio of adjacent eigenvalues (RAE) has been used. However, the direct application of RAE may not achieve adequate NIS detection performance. Therefore, we propose a metric based on the modified ratio of adjacent eigenvalues (MRAE) avoids the issue of RAE. Numerical results show that the metric based on MRAE can achieve proper NIS detection performance even if NIS is larger than the number of antennas.

A CAM-based matching system for fast exact pattern matching is implemented on a hardware system with FPGA and ASIC. The system has a simple structure, and does not employ any Central Processor Unit (CPU) as well as complicated computations. We take advantage of Content Addressable Memory (CAM) which has an ability of parallel multi-match mode for designing the system. The system is applied to fast pattern matching with various required search patterns without using search principles. In this paper, the authors present a CAM-based system for fast exact pattern matching on 2-D data.

With the proliferation of smart grids and the construction of various electric IT systems and networks, a next-generation substation automation system (SAS) based on IEC 61850 has been agreed upon as a core element of smart grids. However, research on security vulnerability analysis and quantification for automated substations is still in the preliminary phase. In particular, it is not suitable to apply existing security vulnerability quantification approaches to IEC 61850-based SAS because of its heterogeneous characteristics. In this paper, we propose an IEC 61850-based SAS network modeling and evaluation approach for security vulnerability quantification. The proposed approach uses network-level and device groupings to categorize the characteristic of the SAS. In addition, novel attack scenarios are proposed through a zoning scheme to evaluate the network model. Finally, an MTTC (Mean Time-to-Compromise) scheme is used to verify the proposed network model using a sample attack scenario.

Reducing the time complexity of character matching is critical to the development of efficient Japanese Optical Character Recognition (OCR) systems. To shorten the processing time, recognition is usually split into separate pre-classification and precise recognition stages. For high overall recognition performance, the pre-classification stage must both have very high classification accuracy and return only a small number of putative character categories for further processing. Furthermore, for any practical system, the speed of the pre-classification stage is also critical. The associative matching (AM) method has often been used for fast pre-classification because of its use of a hash table and reliance on just logical bit operations to select categories, both of which make it highly efficient. However, a certain level of redundancy exists in the hash table because it is constructed using only the minimum and maximum values of the data on each axis and therefore does not take account of the distribution of the data. We propose a novel method based on the AM method that satisfies the performance criteria described above but in a fraction of the time by modifying the hash table to reduce the range of each category of training characters. Furthermore, we show that our approach outperforms pre-classification by VQ clustering, ANN, LSH and AM in terms of classification accuracy, reducing the number of candidate categories and total processing time across an evaluation test set comprising 116,528 Japanese character images.

Many applications of wireless sensor networks (WSNs) require secure communication. The tree-based key management scheme, which is a symmetric key scheme, provides backward and forward secrecy. The sensor nodes in the communication group share a secret key for encrypting messages. When the sensor nodes are added to or evicted from the group, the group key has to be updated by sending rekeying messages. In this paper, we propose a method of key tree structure (KTS) generation by considering the addition and eviction ratio of sensor nodes to reduce the number of rekeying messages, which is influenced by the structure of the tree. For this, we define an extension of an existing tree structure such as a binary or ternary tree and generate KTS using an A* algorithm. To reduce the energy consumed by the message transmission, we also exploit genetic algorithm (GA) to build a secure communication group by considering the KTS. In the paper, we show the effectiveness of the proposed method compared with the existing structure via the simulation in terms of memory usage, the number of rekeying messages and energy consumption.

This paper introduces open-wire fault-resilient multiple-valued codes for reliable asynchronous point-to-point global communication links. In the proposed encoding, two communication modules assign complementary codewords that change between two valid states without an open-wire fault. Under an open-wire fault, at each module, the codewords don't reach to one of the two valid states and remains as “invalid” states. The detection of the invalid states makes it possible to stop sending wrong codewords caused by an open-wire fault. The detectability of the open-wire fault based on the proposed encoding is proven for m-of-n codes. The proposed code used in the multiple-valued asynchronous global communication link is capable of detecting a single open-wire fault with 3.08-times higher coding efficiency compared with a conventional multiple-valued code used in a triple-modular redundancy (TMR) link that detects an open-wire fault under the same dynamic range of logical values.

NROM is one of the emerging non-volatile-memory technologies, which is promising for replacing current floating-gate-based non-volatile memory such as flash memory. In order to raise the fabrication yield and enhance its reliability, a novel test and repair flow is proposed in this paper. Instead of the conventional fault replacement techniques, a novel fault masking technique is also exploited by considering the logical effects of physical defects when the customer's code is to be programmed. In order to maximize the possibilities of fault masking, a novel data inversion technique is proposed. The corresponding BIST architectures are also presented. According to experimental results, the repair rate and fabrication yield can be improved significantly. Moreover, the incurred hardware overhead is almost negligible.

A compact DC-DC convertor is proposed and fabricated by LTCC technology. Multilayer packaging structure is utilized for size reduction. Measured results are provided to show good performance and validate proposed structure. With the inductor embedded into ferrite substrate, the convertor exhibits advantages of both miniature size and high reliability compared with conventional ones.