In this paper, we develop a VCASS substitution system (S-VCASS) using a personal mobile terminal in order to improve the effectiveness of VCASS in an environment comprising both VCASS and non-VCASS vehicles. We propose three new pedestrian state judgment algorithms that can be implemented on a personal mobile terminal for inter-vehicle communications. We evaluate the performances of the three proposed algorithms with real vehicles. Finally, we show that the proposed algorithms can recognize vehicles without VCASS.

Recently, pairing-based cryptographic application sch-emes have attracted much attentions. In order to make the schemes more efficient, not only pairing algorithm but also arithmetic operations in extension field need to be efficient. For this purpose, the authors have proposed a series of cyclic vector multiplication algorithms (CVMAs) corresponding to the adopted bases such as type-I optimal normal basis (ONB). Note here that every basis adapted for the conventional CVMAs are just special classes of Gauss period normal bases (GNBs). In general, GNB is characterized with a certain positive integer h in addition to characteristic p and extension degree m, namely type-⟨h.m⟩ GNB in extension field Fpm. The parameter h needs to satisfy some conditions and such a positive integer h infinitely exists. From the viewpoint of the calculation cost of CVMA, it is preferred to be small. Thus, the minimal one denoted by hmin will be adapted. This paper focuses on two remaining problems: 1) CVMA has not been expanded for general GNBs yet and 2) the minimal hmin sometimes becomes large and it causes an inefficient case. First, this paper expands CVMA for general GNBs. It will improve some critical cases with large hmin reported in the conventional works. After that, this paper shows a theorem that, for a fixed prime number r, other prime numbers modulo r uniformly distribute between 1 to r-1. Then, based on this theorem, the existence probability of type-⟨hmin,m⟩ GNB in Fpm and also the expected value of hmin are explicitly given.

We present cryptanalyses of the original version of AURORA-512 hash function, which is a round-1 SHA-3 candidate. Our attack exploits weaknesses in a narrow-pipe mode of operation of AURORA-512 named "Double-Mix Merkle-Damgård (DMMD)." The current best collision attack proposed by Joux and Lucks only gives rough complexity estimations. We first evaluate its precise complexity and show its optimization. Secondly, we point out that the current best second-preimage attack proposed by Ferguson and Lucks does not work with the claimed complexity of 2291. We then evaluate a complexity so that the attack can work with a high success probability. We also show that the second-preimage attack can be used to attack the randomized hashing scheme. Finally, we present a key-recovery attack on HMAC-AURORA-512, which reveals 512-bit secret keys with 2257 queries, 2259 AURORA-512 operations, and negligible memory. The universal forgery on HMAC-AURORA-384 is also possible by combining the second-preimage and inner-key-recovery attacks.

This paper proposes a new kind of communication system for air traffic control over the oceans; it is particularly effective at handling high air traffic loads due to many oceanic flights. In this system, each aircraft position report is sent to its relevant ground station by forwardly relaying them via a multi hop ad-hoc network that is formed by the aircraft between this aircraft and the ground station. In addition, an effective multiple access scheme with optimal values is also proposed. This scheme enables the various aircraft involved in relaying the signal to operate autonomously in a flight-route airspace. Furthermore, two useful schemes are proposed for efficient timeslot reuse and timeslot assignment in cases of low aircraft densities: the position aided timeslot reuse (PATR) and distance based timeslot assignment (DBTA), respectively. Finally, another scheme is proposed to improve the achievable relayed packet rate under low aircraft densities, which is called interference-based node selection (IB-NS). In all, the proposed system combined with those three schemes show the availability to utilize this system for air traffic control communications, specifically on high traffic ocean routes.

This paper presents an unsupervised learning-based method for selection of feature points and object category classification without previous setting of the number of categories. Our method consists of the following procedures: 1)detection of feature points and description of features using a Scale-Invariant Feature Transform (SIFT), 2)selection of target feature points using One Class-Support Vector Machines (OC-SVMs), 3)generation of visual words of all SIFT descriptors and histograms in each image of selected feature points using Self-Organizing Maps (SOMs), 4)formation of labels using Adaptive Resonance Theory-2 (ART-2), and 5)creation and classification of categories on a category map of Counter Propagation Networks (CPNs) for visualizing spatial relations between categories. Classification results of static images using a Caltech-256 object category dataset and dynamic images using time-series images obtained using a robot according to movements respectively demonstrate that our method can visualize spatial relations of categories while maintaining time-series characteristics. Moreover, we emphasize the effectiveness of our method for category classification of appearance changes of objects.

In this letter, an improved channel estimator for MIMO-SCBT systems is proposed. Pilot blocks are constructed using quadriphase complementary sequences (QCSs) which enable both one-sided (OSD) and two-sided (TSD) channel estimation (CE). And OSD-CE and TSD-CE are combined to provide improved performance in frequency-selective fast and slow fading channels and to maintain low-complexity implementations. Simulation results demonstrate the performance merits of the proposed scheme.

This paper presents an architecture and a circuit design of readout address compression for a high-speed 3-D range-finding image sensor using the light-section method. We utilize a kind of variable-length code which is modified to suit the 3-D range-finder. The best compression rate by the proposed compression technique is 33.3%. The worst compression and the average compression rate is 56.4% and 42.4%, respectively, when we simulated the effectivity by using the example of measured sheet scans. We also show the measurement result of the fabricated image sensor with the address compression.

In this paper, we study the decentralized coverage control problem for an environment using a group of autonomous mobile robots with nonholonomic kinematic and dynamic constraints. In comparison with standard coverage control procedures, we develop a combined controller for Voronoi-based coverage approach in which kinematic and dynamic constraints of the actual mobile sensing robots are incorporated into the controller design. Furthermore, a collision avoidance component is added in the kinematic controller in order to guarantee a collision free coverage of the area. The convergence of the network to the optimal sensing configuration is proven with a Lyapunov-type analysis. Numerical simulations are provided approving the effectiveness of the proposed method through several experimental scenarios.

Owing to the high expressiveness of regular expression, it is frequently used in searching and manipulation of text based data. Regular expression is highly applicable in processing Latin alphabet based text, but the same cannot be said for Hangeul*, the writing system for Korean language. Although Hangeul possesses alphabetic features within the script, expressiveness of regular expression pattern using Hangeul is hindered by the absence of syllable decomposition. Without decomposition support in regular expression, searching through Hangeul text is limited to string literal matching. Literal matching has made enumeration of syllable candidates in regular expression pattern definition indispensable, albeit impractical, especially for a large set of syllable candidates. Although the existing implementation of canonical decomposition in Unicode standard does reduce a pre-composed Hangeul syllable into smaller unit of consonant-vowel or consonant-vowel-consonant letters, it still leaves quite a number of the individual letters in compounded form. We have observed that there is a necessity to further reduce the compounded letters into unit of basic letters to properly represent the Korean script in regular expression. We look at how the new canonical decomposition technique proposed by Kim can help in handling Hangeul in regular expression. In this paper, we examine several of the performance indicators of full decomposition of Hangeul syllable to better understand the overhead that might incur, if a full decomposition were to be implemented in a regular expression engine. For efficiency considerations, we propose a semi decomposition technique alongside with a notation for defining Hangeul syllables. The semi decomposition functions as an enhancement to the existing regular expression syntax by taking in some of the special constructs and features of the Korean language. This proposed technique intends to allow an end user to have a greater freedom to define regular expression syntax for Hangeul.

In OFDM systems, in-phase and quadrature (I/Q) imbalances generated in the analog front-end introduce inter-channel interference and, consequently, error performance degradation. This letter provides an exact expression involving the two-dimensional (2-D) Gaussian Q-function for the error probability of an arbitrary 2-D modulated OFDM signal with I/Q imbalances. The effects of I/Q imbalances on the distribution of an AWGN and the error performance are analyzed.

In this paper, a new adaptive online price control scheme is formalized based on the Stackelberg game model. To provide the most desirable network performance, the proposed scheme consists of two different control mechanisms; user-based and operator-based mechanisms. By using the hierarchical interaction strategy, control decisions in each mechanism act cooperatively and collaborate with each other to satisfy conflicting performance criteria. With a simulation study, the proposed scheme can adaptively adjust the network price to approximate an optimized solution under widely diverse network situations.

In this paper, we design a practical time-reversal quasi-orthogonal space-time block code (TR-QO-STBC) system for broadband multi-input multi-output (MIMO) communications. We first modify the TR-QO-STBC encoding structure so that the interference between the transmitted blocks can be completely removed by linear processing. Two low complex decision-feedback equalization (DFE) schemes are then proposed. One is built from the frequency-domain decision-feedback equalization (FD-DFE). The derived bi-directive FD-DFE (BiD-FD-DFE) cancels the interference among the successive symbols along the time axis. The other one is the enhanced V-BLAST, which cancels the interference between the real and imaginary parts of the spectral components. They have distinct performance characteristics due to the different interference-cancellation strategies. The underlying orthogonal and symmetric characters of TR-QO-STBC are exploited to reduce the computational complexity. Computer simulations confirm that the proposed equalizers can achieve better performance than the existing schemes.

The objective of this study is to investigate the feasibility of an ultra wideband (UWB) impulse radio system for in-body to off-body wireless communication for biomedical applications. At first, a UWB antenna is designed in the UWB low band for implant use in the chest. Then the channel model is extracted and established based on the finite difference time domain (FDTD) simulation with an anatomical human body model. The established channel model consists of a small set of parameters for generating discrete time impulse responses. The generated model shows good agreement with the FDTD-calculated result in terms of key communication metrics. For effective communication over the multipath-affected channel, the pulse position modulation is employed and a 2-finger RAKE structure with a constant temporal delay is proposed in the receiver. The bit error rate performance has shown the validity of the system in the in-body to off-body chest channel.

We revisit the double-pipe construction introduced by Lucks at Asiacrypt 2005. Lucks originally studied the construction for iterated hash functions and showed that the approach is effective in improving security against various types of collision and (second-)preimage attacks. Instead, in this paper we apply the construction to the secret-key setting, where the underlying FIL (fixed-input-length) compression function is equipped with a dedicated key input. We make some adjustments to Lucks' original design so that now the new mode works with a single key and operates as a domain extension of MACs (message authentication codes). Though more than twice as slow as the Merkle-Damgård construction, the double-piped mode enjoys security strengthened beyond the birthday bound. More specifically, when iterating an FIL-MAC whose output size is n-bit, the new double-piped mode yields an AIL-(arbitrary-input-length-)MAC with security up to O(2n) query complexity. This bound contrasts sharply with the birthday bound of O(2n/2), which was the best MAC security accomplished by earlier constructions.

In this paper, the performance of the soft-decision-and-forward (SDF) protocol in the cooperative communication network with one source, one relay, and one destination, where each node has two transmit and receive antennas, is analyzed in terms of the bit error rate (BER) obtained from the pairwise error probability (PEP). Using the moment generating function and Q-function approximation, the PEP of SDF protocol is calculated and we confirm that the SDF with two antennas achieves the full diversity order. For the slow-varying Rayleigh fading channel, the optimal power allocation ratio can be determined so as to minimize the average PEP (or BER). Due to the difficulty of deriving the optimal value analytically, an alternative strategy of maximizing the product signal-to-noise ratio (SNR) of direct and relay links, which we call the suboptimal power allocation, is considered. Through a numerical analysis, we show that the performance gap between the suboptimal and optimal power allocation strategies is negligible in the high SNR region.

Transmission coordination mechanism (TCM) aids opportunistic routing (OR) to reduce the total number of packet transmissions and improve end-to-end throughput. Existing paradigms based on batch map partitions packets of communication session into segments, and transmit packet segments in batch mode sequentially. However, the rate of successful transmission coordination oscillates due to the oscillation of the number of packets batch transmitted. In this paper, we propose batch sliding window-based TCM to improve the performance of OR. By transmitting packets in continuous batch mode, batch sliding window-based TCM can hold the rate of successful transmission coordination steady. Simulation results show the average end-to-end throughput gain of the proposed TCM is 15.4% over existing batch map-based TCM.

Context-aware applications are a key aspect of pervasive computing. The core issue of context-aware application development is how to make the application behave suitably according to the changing context without coupling such context dependencies in the program. Several programming paradigms and languages have been proposed to facilitate the development, but they are either lack of sufficient flexibility or somewhat complex for programming and deploying. A reference programming model is proposed in this paper to make up inadequacy of those approaches. In the model, virtual tables constructed by system and maintained by space manager connect knowledge of both developer and space manager while separating dependency between context and application logic from base program. Hierarchy and architecture of the model are presented, and implementation suggestions are also discussed. Validation and evaluation show that the programming model is lightweight and easy to be implemented and deployed. Moreover, the model brings better flexibility for developing context-aware applications.

Due to the difficulty of test pattern generation for sequential circuits, several design-for-testability (DFT) approaches have been proposed. An improvement to these current approaches is needed to cater to the requirements of today's more complicated chips. This paper introduces a new DFT method applicable to high-level description of circuits, which optimally utilizes existing functional elements and paths for test. This technique, called F-scan, effectively reduces the hardware overhead due to test without compromising fault coverage. Test application time is also kept at the minimum. The comparison of F-scan with the performance of gate-level full scan design is shown through the experimental results.

This paper proposes a further improved technique on the stochastic functional approach for randomly rough surface scattering. The original improved technique has been established in the previous paper [Waves in Random and Complex Media, vol.19, no.2, pp.181-215, 2009] as a novel numerical-analytical method for a Wiener analysis. By deriving modified hierarchy equations based on the diagonal approximation solution of random wavefields for a TM plane wave incidence or even for a TE plane wave incidence under large roughness, large slope or low grazing incidence, such a further improved technique can provide a large reduction of required computational resources, in comparison with the original improved technique. This paper shows that numerical solutions satisfy the optical theorem with very good accuracy, by using small computational resources.

It is known that traditional water-filling provides a closed form solution for capacity maximization in frequency-selective channels or fading channels with adaptive modulation. However, the solution is derived from a maximum mutual information argument with a single total power constraint. Motivated by the new technology of coordinated multiple point transmission (CoMP), this paper considers a novel power allocation scheme for a frequency-selective fading channel with multiple coordinated transmission points (CTP) transmission, in which each CTP has a power constraint and an individual channel state information (CSI). In order to maximize the channel's throughput, closed form solutions are obtained by solving a non-convex constrained optimization problem. The solution turns out to take the form of traditional WF and also combined with some regular cooperative feature. Based on the derived solution, we firstly investigate a joint water-filling (Jo-WF) power allocation scheme and a new iterative Jo-WF algorithm. Numerical results are presented to verify the optimality of the derived scheme and to show throughput gains over traditional non-coordinated water-filling (WF) and equal power allocation (EPA). Considering the flexibility of CTP's category, e.g., base station or relay station, it is known that the derived Jo-WF power allocation scheme can be valid for any coordinated networks such as next-generation cellular networks or ad-hoc networks.