This paper presents an alternative approach for the analysis of EM field by a rotating body with FDTD method and Overset Grid Generation method, considering Lorentz transformation for the higher velocity cases. This approach has been previously proposed for the case of linear and uniformly moving body against/to the incident wave. Here, the approach is expanded to a rotating body which includes the interpolation technique in the space and time increment along the cylindrical rotation at the fixed axis. First, the grid size ratios between the main mesh and the sub-mesh are studied. The appropriate choice of the grid size ratio is obtained. Then, the modulations of the EM field when the incident wave hits the rotating body in high velocity cases are analyzed. The relationship of the phase shift and the velocity is further observed. The observed EM fields are compared with the theoretical results and achieved good agreements in high relative velocities. The assessment of the numerical errors in a rotating environment is also highlighted. This numerical approach may have numerous situations to which it can be applied. This may be involved with the design of rotating devices such as microactuator, commutator and others.

In this paper, we propose a geographic location-based distributed routing (GDR) system. The GDR system provides information lookup based on latitude and longitude coordinates. Each node of the GDR system utilizes the coordinates as an identifier (ID), and manages an overlay routing table. An ID is generated to reflect the geographical location without using Space Filling Curve (SFC). The ID is in cartesian format (x, y), which represents the longitude x and latitude y. In a system with N nodes, each node has a routing table of size log N and a search is possible in O(log N). We evaluate the routing performance of GDR and other systems based on Chord, Kademlia and CAN. We show that in both the ID is in cartesian format and the ID is generated by using SFC, GDR, Chord and Kademlia have the same mean and the same variance of the path length, while the mean and the variance of the relay length of GDR are smaller than those of Chord and Kademlia. Furthermore, while GDR and CAN have the same mean and the same variance of the relay length, the mean and the variance of the path length of GDR are smaller than those of CAN.

The deployment of hybrid wide-area OpenFlow networks is essential for the gradual integration of OpenFlow technology into existing wide-area networks. Integration is necessary because it is impractical to replace such wide-area networks with OpenFlow-enabled ones at once. On the other hand, the design, deployment, and operation of such hybrid OpenFlow networks are often conducted intuitively without in-depth technical considerations. In this paper, we systematically discuss the technical aspects of the hybrid architecture for OpenFlow networks based on our experience so far in developing wide-area hybrid OpenFlow networks on JGN2plus and JGN-X, which are nation-wide testbed networks in Japan. We also describe the design and operation of RISE (Research Infrastructure for large-Scale network Experiments) on JGN-X, whose objective is to support a variety of OpenFlow network experiments.

The conventional Equal Gain Transmission and Maximum Ratio Combining (EGT/MRC) requires nonlinear optimization to find the optimal beamforming vector at the receiver. This study shows that the optimal beamforming vector can be easily formed by the geometrical concepts. Accordingly, a novel transmission/reception scheme, called the Scalar Equal Gain Transmission and Generalized Maximum Ratio Combining (SEGT/GMRC), is presented and examined. The Monte-Carlo simulations validate the theory and it is shown that the optimal beamforming vector formed by SEGT is the same as the one determined by the nonlinear optimizer. The closed-form analytical error performance of the SEGT/GMRC scheme is also derived for multiple input single output (MISO) communications. This study also introduces the new limited-feedback geometrical codebooks, called the Quantized Equal gain (QE) codebooks, which can be easily installed as symbol mappers. These codebooks are based on quantized SEGT/GMRC, which eliminates the need for any iterative searching scheme, such as exhaustive search at the receiver. The minimum amount of feedback bits depends on the modulation scheme, where a general M-PSK modulation requires at least log2M bits per quantized phase angle. It is also shown that BPSK modulation requires at least 2 bits per quantized phase angle for near-optimal performance.

The overall performance of multi-hop cognitive radio networks (MHCRNs) can be improved significantly by employing the diversity of orthogonal licensed channels in underlay fashion. However, the mutual interference between secondary links and primary links and the congestion due to the contention among traffic flows traversing the shared link become obstacles to this realizing technique. How to control congestion efficiently in coordination with power and spectrum allocation optimally in order to obtain a high end-to-end throughput is motivating cross-layer designs for MHCRNs. In this paper, by taking into account the problem of joint rate adaption, power control, and spectrum allocation (JRPS), we propose a new cross-layer optimization framework for MHCRNs using orthogonal frequency division multiple access (OFDMA). Specifically, the JRPS formulation is shown to be a mix-integer non-linear programming (MINLP) problem, which is NP-Hard in general. To solve the problem, we first develop a partially distributed algorithm, which is shown to converge to the global optimum within a reasonable time interval. We next propose a suboptimal solution which addresses the shortcomings of the first. Using numerical results, we finally demonstrate the efficiency of the proposed algorithms.

This study proposes an improvement to the Triangular Inequality Elimination (TIE) algorithm for vector quantization (VQ). The proposed approach uses recursive and intersection (RI) rules to compensate and enhance the TIE algorithm. The recursive rule changes reference codewords dynamically and produces the smallest candidate group. The intersection rule removes redundant codewords from these candidate groups. The RI-TIE approach avoids over-reliance on the continuity of the input signal. This study tests the contribution of the RI rules using the VQ-based, G.729 standard LSP encoder and some classic images. Results show that the RI rules perform excellently in the TIE algorithm.

This paper presents a new simple method for reducing mutual coupling between dual-element microstrip antennas (MSAs) for bistatic radar using a wave absorber. The two elements are closely placed on a substrate by the distance of λ0/4 through the wall-shaped absorber. The height and width of the absorber were optimized for minimum mutual coupling with the electromagnetic simulator. It was found that less than -60 dB minimum mutual coupling can be achieved by the impedance matching of the absorber in a near field. The influence for the reflection characteristics from the absorber is small enough, and the reduction of the antenna gain is only 1.1 dB. The rate of the lost power characteristics showed that the absorption improves the mutual couplings. Then the proposed structure for a practical configuration was investigated. The measurement results of the optimized structure tallied well with the simulation results.

Ultra wideband radar is one of the most promising techniques for non-invasive imaging in a dielectric medium, which is suitable for both medical screening and non-destructive testing applications. A novel imaging method for such an application is proposed in this brief paper, which has been extended from the advanced range points migration method to a multi-static observation model with circular arrays. One notable feature of this method is that it is applicable to either arbitrary dielectric or internal object shapes, and it can also expand the reconstructible image region compared with that obtained using the mono-static model by employing received signals after penetrating various propagation paths in dielectric medium. Numerical results for the investigation of an elliptical object, surrounded by a random dielectric surface, show the remarkable advantages of the proposed method with respect to image expansion.

Three synchronization issues, i.e., phase, frequency, and symbol time, have to be properly controlled to achieve distributed beamforming gain. In orthogonal frequency division multiplexing (OFDM) systems, frequency offset in cooperating signals is more important than other synchronization issues since it results in SNR degradation as well as inter-carrier interference (ICI). In this paper, the impact of frequency offset in distributed beamforming is analyzed for OFDM systems. ICI resulting from frequency offset between cooperating signals is also investigated and approximated. Performance degradation due to frequency offset is shown with various numbers of cooperating signals and offset values. We show that frequency offset between cooperating signals is critical in OFDM systems since it leads to interference from the other subcarriers as well as power loss in the desired signal.

A distance bounding protocol provides an upper bound on the distance between communicating parties by measuring the round-trip time between challenges and responses. It is an effective countermeasure against mafia fraud attacks (a.k.a. relay attacks). The adversary success probability of previous distance bounding protocols without a final confirmation message such as digital signature or message authentication code is at least . We propose a unilateral distance bounding protocol without a final confirmation message, which reduces the adversary success probability to .

A method of calibration for GPR responses is introduced in order to extract a target response from GPR data. This calibration procedure eliminates undesirable waveform distortion that is caused by antenna characteristics and multiple scattering effects between the antennas and the ground surface. An application result to measured GPR data shows that undesirable late-time responses caused by the antenna characteristics and multiple scattering effects are removed, and that the target response is clearly reconstructed. This result demonstrates that the waveform calibration of GPR data is significant and essential for reliable target identification.

The Linking Open Data (LOD) cloud is a collection of linked Resource Description Framework (RDF) data with over 31 billion RDF triples. Accessing linked data is a challenging task because each data set in the LOD cloud has a specific ontology schema, and familiarity with the ontology schema used is required in order to query various linked data sets. However, manually checking each data set is time-consuming, especially when many data sets from various domains are used. This difficulty can be overcome without user interaction by using an automatic method that integrates different ontology schema. In this paper, we propose a Mid-Ontology learning approach that can automatically construct a simple ontology, linking related ontology predicates (class or property) in different data sets. Our Mid-Ontology learning approach consists of three main phases: data collection, predicate grouping, and Mid-Ontology construction. Experiments show that our Mid-Ontology learning approach successfully integrates diverse ontology schema with a high quality, and effectively retrieves related information with the constructed Mid-Ontology.

This paper describes a simulation platform for use in the quantitative assessment of different respiratory motion correction techniques in Coronary MR angiography (CMRA). The simulator incorporates acquisition of motion parameters from heart motion tracking and applies it to a deformable heart model. To simulate respiratory motion, a high-resolution 3-D coronary heart reference image is deformed using the estimated linear transformation from a series of volunteer coronal scout scans. The deformed and motion-affected 3-D coronary images are used to generate segmented k-space data to represent MR data acquisition affected by respiratory motion. The acquired k-space data are then corrected using different respiratory motion correction methods and converted back to image data. The resulting images are quantitatively compared with each other using image-quality measures. Simulation experiment results are validated by acquiring CMRA scans using the correction methods used in the simulation.

Self-encoded spread spectrum (SESS) derives its spreading codes from the random information source rather than using traditional pseudo-random codes. It has been shown that the memory in SESS modulated signals not only can deliver a 3 dB gain in additive white Gaussian noise (AWGN) channels, but also can be exploited to achieve time diversity and robust bit-error rate (BER) performance in fading channels. In this paper, we propose an extension to SESS, namely coded-sequence self-encoded spread spectrum (CS-SESS), and show that it can further improve the BER performance. We describe the CS-SESS scheme and present the theoretical analysis and simulation results for AWGN and fading channels. Iterative detector is developed to exploit the inherent temporal diversity of CS-SESS modulation. The simulation results show that it can achieve the expected 4.7 dB gain with a complexity that increases linearly with the spreading sequence length under AWGN. In Rayleigh fading channel, it can effectively mitigate the fading effects by exploiting the overall diversity gain. Chip interleaving is shown to yield a performance improvement of around 4.7 dB when compared to an chip interleaved direct sequence spread spectrum (DSSS) system.

Recently, Shao et al. [M. Shao and Y. Chin, A privacy-preserving dynamic id-based remote user authentication scheme with access control for multi-server environment, IEICE Transactions on Information and Systems, vol.E95-D, no.1, pp.161–168, 2012] proposed a dynamic ID-based remote user authentication scheme with access control for multi-server environments. They claimed that their scheme could withstand various attacks and provide anonymity. However, in this letter, we will point out that Shao et al.'s scheme has practical pitfalls and is not feasible for real-life implementation. We identify that their scheme is vulnerable to two kinds of attacks and cannot provide anonymity.

In this note we suggest a new parallelizable mode of operation for message authentication codes (MACs). The new MAC algorithm iterates a pseudo-random function (PRF) FK:{0,1}m → {0,1}n, where K is a key and m,n are positive integers such that m ≥ 2n. The new construction is an improvement over a sequential MAC algorithm presented at FSE2008, solving positively an open problem posed in the paper – the new mode is capable of fully parallel execution while achieving rate-1 efficiency and “full n-bit” security. Interestingly enough, PMAC-like parallel structure, rather than CBC-like serial iteration, has beneficial side effects on security. That is, the new construction is provided with a more straightforward security proof and with an even better (“-free”) security bound than the FSE 2008 construction.

In this paper, we propose a new data association method termed the highest probability data association (HPDA) and apply it to real-time recursive nonlinear tracking in heavy clutter. The proposed method combines the probabilistic nearest neighbor (PNN) with a modified probabilistic strongest neighbor (PSN) approach. The modified PSN approach uses only the rank of the measurement amplitudes. This approach is robust as exact shape of amplitude probability density function is not used. In this paper, the HPDA is combined with particle filtering for nonlinear target tracking in clutter. The measurement with the highest measurement-to-track data association probability is selected for track update. The HPDA provides the track quality information which can be used in for the false track termination and the true track confirmation. It can be easily extended to multi-target tracking with nonlinear particle filtering. The simulation studies demonstrate the HPDA functionality in a hostile environment with high clutter density and low target detection probability.

Network slicing for wide-area coordinated packet processing has attracted attentions for improving efficiency of handling network traffic. We have recently proposed a tag-based network slicing mechanism called OpenTag, and introduced the prototype implementation of the OpenTag redirector on an evaluation board. In this paper, we investigate the integration of the OpenTag redirector into a commercial network device. Our contributions are three-fold: (1) designing the architecture aiming OpenTag-capable intermediaries embedded on commercial network devices, (2) implementing a prototype of the embedded OpenTag redirector using the Advanced Mezzanine Card (AMC) which has an OCTEON network processor, (3) showing our implementation can tolerate high bandwidth environment.

An important factor determining the performance of delay tolerant networks (DTNs) is packet delivery delay. In this paper, we study the block delivery delay of DTN with the epidemic routing scheme based on random linear network coding (RLNC). First, simulations show that the influence of relay buffer size on the delivery delay is not as strong in RLNC-based routing as it is in replica-based routing. With this observation,we can simplify the performance analysis by constraining the buffer of the relay node to just one size. Then we derive the cumulative distribution function (CDF) of block delivery delay with difference equations. Finally, we validate the correctness of our analytical results by simulations.

As one innovative research that heavily depends on the network virtualization for its realization and deployment on an Internet-scale, we propose an approach to utilize user resources in information-centric network (ICN). We try to fully benefit from the in-network cache that is one attractive feature of ICN by expanding the in-network cache indirectly based on the user resources. To achieve this, in this paper, we focus on how to encourage users to contribute their resources in ICN. Through simulations, we examine a feasibility of our approach and an effect of user participation on the content distribution performance in ICN. We also briefly discuss how the network virtualization technique can be utilized for our research in terms of its evaluation and deployment.