This letter proposes an algorithm of determining the BER-minimized block delay for detection and the associated precoder design once the channel state information and limited transmission power are given. Simulation cases demonstrate the adjusting capability of the proposed algorithm for achieving best BER performance of the joint linear transceiver design.

We realized single-mode hole-assisted optical fiber (HAF) cord whose fiber has a superior bending loss characteristic that complies with ITU-T Recommendation G. 657 for use in highly reliable optical fiber distribution facilities in central offices. The cord has an excellent anti-shock characteristic, and can be scanned by a conventional optical fiber cord identifier despite its very low bending loss. Experiments show that the single-mode HAF cord and its application to optical signal distribution in a central office can provide highly service reliability.

In this letter, we consider a cognitive radio based multihop network under the spectrum sharing underlay paradigm. By taking into account the interference constraints, we present an exact closed-form expression for outage probability, which is valid for the whole signal-to-noise ratio regime. In addition, some numerical examples of interest that study the effect of the number of hops and/or the interferer threshold on primary users are illustrated and discussed. Numerical results show that multihop systems still offer a considerable gain as compared to direct transmission under the same limit of interference.

Quasi-cyclic (QC) low-density parity-check (LDPC) codes have several appealing properties regarding decoding, storage requirements and encoding aspects. In this paper, we focus on the QC LDPC codes over GF(q) whose parity-check matrices have fixed column weight j = 2. By investigating two subgraphs in the Tanner graphs of the corresponding base matrices, we derive two upper bounds on the minimum Hamming distance for this class of codes. In addition, a method is proposed to construct QC LDPC codes over GF(q), which have good Hamming distance distributions. Simulations show that our designed codes have good performance.

A novel half mode elliptic substrate integrated waveguide (HMESIW) filter with bypass coupling substrate integrated circular cavity (BCSICC) is proposed and fabricated by using standard PCB technology. Due to the use of an elliptical waveguide cavity, the tolerance sensitivity of the filter is reduced. The filter optimizing procedure is therefore simplified. The measured results demonstrate its superior performance in tolerance sensitivity and show good agreements with the simulation results.

In this paper, we propose N-Dimensional (ND) Tensor Supervised Neighborhood Embedding (ND TSNE) for discriminant feature representation, which is used for view-based object recognition. ND TSNE uses a general Nth order tensor discriminant and neighborhood-embedding analysis approach for object representation. The benefits of ND TSNE include: (1) a natural way of representing data without losing structure information, i.e., the information about the relative positions of pixels or regions; (2) a reduction in the small sample size problem, which occurs in conventional supervised learning because the number of training samples is much less than the dimensionality of the feature space; (3) preserving a neighborhood structure in tensor feature space for object recognition and a good convergence property in training procedure. With Tensor-subspace features, the random forests is used as a multi-way classifier for object recognition, which is much easier for training and testing compared with multi-way SVM. We demonstrate the performance advantages of our proposed approach over existing techniques using experiments on the COIL-100 and the ETH-80 datasets.

As supercomputers increase in size, the mean time between failures (MTBF) of a system becomes shorter, and the reliability problem of supercomputers becomes more and more serious. MPI is currently the de facto standard used to build high-performance applications, and researches on the fault tolerance methods of MPI are always hot topics. However, due to the characteristics of MPI programs, most current checkpointing methods for MPI programs need to modify the MPI library (even operating system), or implement a complicated protocol by logging lots of messages. In this paper, we carry forward the idea of Application-Level Checkpointing (ALC). Based on the general fact that programmers are familiar with the communication characteristics of applications, we have developed BC-ALC, a new portable blocking coordinated ALC for MPI programs. BC-ALC neither modifies the MPI library (even operating system) nor logs any message. It implements coordination only by the Barrier operations instead of any complicated protocol. Furthermore, in order to reduce the cost of fault-tolerance, we reduce the synchronization range of the barrier, and design WBC-ALC, a weak blocking coordinated ALC utilizing group synchronization instead of global synchronization based on the communication relationship between processes. We also propose a fault-tolerance framework developed on top of WBC-ALC and discuss an implementation of it. Experimental results on NPB3.3-MPI benchmarks validate BC-ALC and WBC-ALC, and show that compared with BC-ALC, the average coordination time and the average backup time of a single checkpoint in WBC-ALC are reduced by 44.5% and 5.7% respectively.

Optical code-division multiple-access (OCDMA) is a promising technique for multimedia transmission in fiber-optic local-area networks (LANs). Variable-weight optical orthogonal codes (OOCs) can be used for OCDMA networks supporting multiple quality of services (QoS). Most constructions for optimal variable-weight OOCs have focused on the case where the number of distinct Hamming weights of all codewords is equal to two, and the codewords of weight 3 are normally included. In this letter, four explicit constructions of optimal (υ,{4,5,6},1,Q)-OOCs are presented, and more new optimal (υ,{4,5,6},1,Q)-OOCs are obtained via recursive constructions. These improve the existing results on optimal variable-weight OOCs with at least three distinct Hamming weights and minimum Hamming weight 4.

The present status of superconducting terahertz emitter using the intrinsic Josephson junctions in high-Tc superconductor Bi2Sr2CaCu2O8+δ is reviewed. Fabrication methods of the emitting device, electrical and optical characteristics of them, synchronizing operation of two emitters and an example of applications to the terahertz imaging will be discussed. After the description of fabrication techniques by an Argon ion milling with photolithography or metal masks and by a focused ion beam, optical properties of radiation spectra, the line width, polarization and the spatial distribution of emission are presented with some discussion on the operation mechanism. For electrical properties, reversible and irreversible operations at high and low electrical currents, respectively, and electrical modulation of the radiation intensity for terahertz imaging are presented.

In this letter, we propose and analyze a cooperative transmission scheme (CTS) that uses transmission timing control for LTE enterprise femtocells. In our scheme, the user equipment (UE) can receive the desired signal from an adjacent fBS as well as its serving femtocell BS (fBS). Thus, UE achieves an improved signal to interference ratio (SIR) due to the synchronization of the two signals. Analysis and simulation results show that the proposed scheme can reduce the outage probability for enterprise femtocells compared to the conventional system. In particular, a significant performance improvement can be achieved for UEs located at cell edges.

To reconstruct low-resolution facial photographs which are in focus and without motion blur, a novel algorithm based on local similarity preserving is proposed. It is based on the theories of local manifold learning. The innovations of the new method include mixing point-based entropy and Euclidian distance to search for the nearest points, adding point-to-patch degradation model to restrict the linear weights and compensating the fusing patch to keep energy coherence. The compensation reduces the algorithm dependence on training sets and keeps the luminance of reconstruction constant. Experiments show that our method can effectively reconstruct 1612 images with the magnification of 88 and the 3224 facial photographs in focus and without motion blur.

In 3GPP (3-rd Generation Partnership Project) LTE (Long Term Evolution) system, the use of PRS (Positioning Reference Signal) for OTDOA (Observed Time Difference of Arrival) based positioning method has been agreed. However, PRSs can be overlapped at the receiver side in synchronous network because the frequency shift pattern of PRS is decided by cell ID (Identity). Moreover, in asynchronous network, the loss of orthogonality between received PRSs generates continuous interferences. Even though autonomous muting can be applied to solve the interference problems in synchronous and asynchronous networks, the muting scheme degrades the overall positioning efficiency and requires additional network complexity. Therefore, in this paper, we propose novel OTDOA based positioning methods at the receiver side to improve positioning efficiency: cancellation method of serving PRS for synchronous network, TDORS (Time Domain Orthogonal Reference Signal) generation and useful CIR (Channel Impulse Response) selection methods for asynchronous network. We verified that the proposed methods can achieve an accurate estimation and stable operation without PRS muting.

We have developed a process for the fabrication of high-quality Nb/AlOx/Nb tunnel junctions with small area and high current densities for the heterodyne mixers at millimeter and submillimeter wavelengths. Their dc I-V curves are numerically studied, including the broadening of quasiparticle density of states resulting from the existence of an imaginary part of the gap energy of Nb. We have found both experimentally and numerically that the subgap current is strongly dependent on bias voltage at temperatures below 4.2 K unlike the prediction of the BCS tunneling theory. It is shown that calculated dc I-V curves taking into account the complex number of the gap energy agree well with those of Nb/AlOx/Nb junctions measured at temperatures from 0.4 to 4.2 K. We have successfully built receivers at millimeter and submillimeter wavelengths with the noise temperature as low as 4 times the quantum photon noise, employing those high-quality Nb/AlOx/Nb junctions. Those low-noise receivers are to be installed in the ALMA (Atacama Large Millimeter/Submillimeter Array) telescope and they are going into series production now.

In the present paper, we address the problem of extrapolating group proximities from member relations, which we refer to as the group proximity problem. We assume that a relational dataset consists of several groups and that pairwise relations of all members can be measured. Under these assumptions, the goal is to estimate group proximities from pairwise relations. In order to solve the group proximity problem, we present a method based on embedding and distribution mapping, in which all relational data, which consist of pairwise dissimilarities or dissimilarities between members, are transformed into vectorial data by embedding methods. After this process, the distributions of the groups are obtained. Group proximities are estimated as distances between distributions by distribution mapping methods, which generate a map of distributions. As an example, we apply the proposed method to document and bacterial flora datasets. Finally, we confirm the feasibility of using the proposed method to solve the group proximity problem.

“Internet of Things” (IoT) requires information to be collected from “anything”, “anytime”, and “anywhere”. In order to achieve this, wireless devices are required that have (1) automatic data acquisition capability, (2) small size, (3) long life, and (4) long range communication capability. One way to meet these requirements is to adopt active Radio Frequency Identification (RFID) systems. Active RFID is more advantageous than passive RFID and enables higher data reading performance over longer distances. This paper surveys active RFID systems, the services they currently promise to provide, technical problems common to these services, and the direction in which research should head in the future. It also reports the results of EPCglobal (EPC: Electronic Product Code) pilot tests conducted on global logistics for tracking ocean/air container transportation using active RFID systems for which we developed several new types of active RFID tags. The test results confirm that our active RFID tags have sufficient capability and low power consumption to well support ocean/air transportation and logistics service.

In this paper, we propose a way to improve the classification performance of support vector machines (SVMs), especially for speech and music frames within a selectable mode vocoder (SMV) framework. A myriad of techniques have been proposed for SVMs, and most of them are employed during the training phase of SVMs. Instead, the proposed algorithm is applied during the test phase and works with existing schemes. The proposed algorithm modifies a kernel parameter in the decision function of SVMs to alter SVM decisions for better classification accuracy based on the previous outputs of SVMs. Since speech and music frames exhibit strong inter-frame correlation, the outputs of SVMs can guide the kernel parameter modification. Our experimental results show that the proposed algorithm has the potential for adaptively tuning classifications of support vector machines for better performance.

We present sampling theorems that reconstruct consistent signals from noisy underdetermined measurements. The consistency criterion requires that the reconstructed signal yields the same measurements as the original one. The main issue in underdetermined cases is a choice of a complementary subspace L in the reconstruction space of the intersection between the reconstruction space and the orthogonal complement of the sampling space because signals are reconstructed in L. Conventional theorems determine L without taking noise in measurements into account. Hence, the present paper proposes to choose L such that variance of reconstructed signals due to noise is minimized. We first arbitrarily fix L and compute the minimum variance under the condition that the average of the reconstructed signals agrees with the noiseless reconstruction. The derived expression clearly shows that the minimum variance depends on L and leads us to a condition for L to further minimize the minimum value of the variance. This condition indicates that we can choose such an L if and only if L includes a subspace determined by the noise covariance matrix. Computer simulations show that the standard deviation for the proposed sampling theorem is improved by 8.72% over that for the conventional theorem.

We have proposed a novel call admission control (CAC) for maximizing total user satisfaction in a heterogeneous traffic network and showed the effectiveness of our CAC by using an optimal threshold from numerical analysis [1]. In our previous CAC, when a new broadband flow arrives and the total accommodated bandwidth is more than or equal to the threshold, the arriving new broadband flow is rejected. In actual networks, however, users may agree to wait for a certain period until the broadband flow, such as video, begins to play. In this paper, when total accommodated bandwidth is more than or equal to the threshold, arriving broadband flows wait instead of being rejected. As a result, we can greatly improve total user satisfaction.

Let G be a connected graph in which we designate a vertex or a block (a biconnected component) as the center of G. For each cut-vertex v, let Gv be the connected subgraph induced from G by v and the vertices that will be separated from the center by removal of v, where v is designated as the root of Gv. We consider the set R of all such rooted subgraphs in G, and assign an integer, called an index, to each of the subgraphs so that two rooted subgraphs in R receive the same indices if and only if they are isomorphic under the constraint that their roots correspond each other. In this paper, assuming a procedure for computing a signature of each graph in a class of biconnected graphs, we present a framework for computing indices to all rooted subgraphs of a graph G with a center which is composed of biconnected components from . With this framework, we can find indices to all rooted subgraphs of a outerplanar graph with a center in linear time and space.

In recent years, wireless communication technology has been studied intensively. In particular, MIMO which employs several transmit and receive antennas is a key technology for enhancing spectral efficiency. However, conventional MIMO architectures require some transceiver circuits for the sake of transmitting and receiving separate signals, which incurs the cost of one RF front-end per antenna. In addition to that, MIMO systems are assumed to be used in low spatial correlation environment between antennas. Since a short distance between each antenna causes high spatial correlation and coupling effect, it is difficult to miniaturize wireless terminals for mobile use. This paper shows a novel architecture which enables mobile terminals to be miniaturized and to work with a single RF front-end by means of adaptive analog beam-forming with parasitic antenna elements and antenna switching for spatial multiplexing. Furthermore, statistical analysis of the proposed architecture is also discussed in this paper.