Based on recent results for 2-D continuous-discrete systems, this paper develops 2-D Laplace-z transform, which can be used to analyze 2-D continuous-discrete signals and system in Laplace-z hybrid domain. Current 1-D Laplace transformation and z transform can be combined into the new 2-D s-z transform. However, 2-D s-z transformation is not a simple extension of 1-D transform, in 2-D case, we need consider the 2-D boundary conditions which don't occur in 1-D case. The hybrid 2-D definitions and theorems are given in the paper. To verify the results of this paper, we also derived a numerical inverse 2-D Laplace-z transform, applying it to show the 2-D pulse response of a stable 2-D continuous-discrete system.

Group signature schemes with membership revocation have been intensively researched. However, signing and/or verification of some existing schemes have computational costs of O(R), where R is the number of revoked members. Existing schemes using a dynamic accumulator or a similar technique have efficient signing and verifications with O(1) complexity. However, before signing, the signer has to modify his secret key with O(N) or O(R) complexity, where N is the group size. Therefore, for larger groups, signers suffer from enormous costs. On the other hand, an efficient scheme for middle-scale groups with about 1,000 members is previously proposed, where the signer need not modify his secret key. However this scheme also suffers from heavy signing/verification costs for larger groups with more than 10,000 members. In this paper, we adapt the middle-scale scheme to larger groups ranging from 1,000 to 1,000,000 members. At the sacrifice of the group manager's slight cost, our signing/verification is sufficiently efficient.

We propose a new analysis technique against a class of countermeasure using randomized binary signed digit (BSD) representations. We also introduce some invariant properties between BSD representations. The proposed analysis technique can directly recover the secret key from power measurements without information for algorithm because of the invariant properties of BSD representation. Thus the proposed attack is applicable to all countermeasures using BSD representations. Finally, we give the simulation results against some countermeasures using BSD representation such as Ha-Moon method, Ebeid-Hasan method, and the method of Agagliate et al. The results show that the proposed attack is practical analysis method.

HfOxNy thin films formed by the electron cyclotron resonance (ECR) Ar/N2 plasma nitridation of HfO2 films were investigated for high-k gate insulator applications. HfOxNy thin films formed by the ECR Ar/N2 plasma nitridation (60 s) of 1.5-nm-thick HfO2 films, which were deposited on chemically oxidized Si(100) substrates, were found to be effective for suppressing interfacial layer growth or crystallization during postdeposition annealing (PDA) in N2 ambient. After 900 PDA of for 5 min in N2 ambient, it was found that HfSiON film with a relatively high dielectric constant was formed on the HfOxNy/Si interface by Si diffusion. An equivalent oxide thickness (EOT) of 2.0 nm and a leakage current density of 1.010-3 A/cm2 (at VFB-1 V) were obtained. The effective mobility of the fabricated p-channel metal-insulator-semiconductor field-effect transistor (MISFET) with the HfOxNy gate insulator was 50 cm2/Vs, and the gate leakage current of the MISFET with the HfOxNy gate insulator was found to be well suppressed compared with the MISFET with the HfO2 gate insulator after 900 PDA because of the nitridation of HfO2.

Recently, Boneh and Boyen proposed a new provably secure short signature scheme under the q-strong Diffie-Hellman assumption without random oracles. This scheme is based on bilinear map which is different from Cramer-Shoup signature scheme (which is based on the strong RSA assumption). However, Tan [17] showed that Boneh- Boyen scheme is subjected to key substitution attacks in the multi-user setting. In this paper, we propose a new signature scheme. We prove that the proposed scheme is provably secured against existential forgery under adaptive chosen message attack in the standard model and also secure against key substitution attacks.

To perform a comparative study, we experimented on two differential epitaxial structures, the conventional metamorphic high-electron-mobility-transistor (MHEMT) using the InAlAs/InGaAs/InAlAs structure and the InP-composite-channel MHEMT adopting the InAlAs/InGaAs/InP structure. Compared with the conventional MHEMT, the InP-composite-channel MHEMT shows improved breakdown performance; more than approximately 3.8 V. This increased breakdown voltage can be explained by the lower impact ionization coefficient of the InP-composite-channel MHEMT than that of the conventional MHEMT. The InP-composite-channel MHEMT also shows improved Radio Frequency characteristics of S21 gain of approximately 4.35 dB at 50 GHz, and a cutoff frequency (fT) and a maximum frequency of oscillation (fmax) of approximately 124 GHz and 240 GHz, respectively, were obtained. These are due to decreases in go and gm.

Combined input-crosspoint buffered (CICB) switches relax arbitration timing and provide high-performance switching for packet switches with high-speed ports. It has been shown that these switches, with one-cell crosspoint buffer and round-robin arbitration at input and output ports, provide 100% throughput under uniform traffic. However, under admissible traffic patterns with nonuniform distributions, only weight-based selection schemes are reported to provide high throughput. This paper proposes a round-robin based arbitration scheme for a CICB packet switch that provides 100% throughput for several admissible traffic patterns, including those with uniform and nonuniform distributions, using one-cell crosspoint buffers and no speedup. The presented scheme uses adaptable-size frames, where the frame size is determined by the traffic load.

In this letter, we propose a combined scheme of minimum mean square error (MMSE) detection and successive interference cancellation (SIC) for multiuser space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems. With the same complexity order, the proposed scheme provides significant bit error rate (BER) performance improvement over the linear MMSE multiuser detector.

Multi-context FPGAs allow very quick reconfiguration by storing multiple configuration data at the same time. While testing for FPGAs with single-context memories has already been studied by many researchers, testing for multi-context FPGAs has not been proposed yet. This paper presents an architecture of testable multi-context FPGAs. In the proposed multi-context FPGA, configuration data stored in a context can be copied into another context. This paper also shows testing of the proposed multi-context FPGA. The proposed testing uses the testing for the traditional FPGAs with single-context. The testing is capable of detecting single stuck-at faults and single open faults which affect normal operations. The number of test configurations for the proposed testing is at most two more than that for the testing of FPGAs with single-context memories. The area overhead of the proposed architecture is 7% and 4% of the area of a multi-context FPGA without the proposed architecture when the number of contexts in a configuration memory is 8 and 16, respectively.

A novel blind channel estimation scheme is proposed for OFDM systems employing PSK modulation. This scheme minimizes the number of possible channels by exploiting the constant modulus property, chooses a best fit over the possible channels by exploiting the finite alphabet property of information signals, and achieves competitive performance with low computational complexity. Results comparing the new scheme with the finite-alphabet based channel estimation are presented.

Recently with the high expectation of voice over WLAN service, to support fast inter-AP security transition in WLAN Access Point (AP) is one of the most actively investigating issues. It is also very important problem to minimize inter-AP security transition (IAPST) latency, while maintaining constantly the secure association from old AP when a station transits to new AP. With this background, this paper presents a novel association control mechanism whose objective pursues to minimize IAPST latency time and to take countermeasures against attacks of rogue transition station. Experiment shows that the proposed scheme outperforms the legacy AP over 70% with regard to the transition latency.

Affine projection algorithms perform well for acoustic echo cancellation and adaptive equalization. Although these algorithms typically provide fast convergence, they are unduly complex when updating the weights of the associated adaptive filter. In this paper, we propose a new subband affine projection (SAP) algorithm and a facile method for its implementation. The SAP algorithm is derived by combining the affine projection algorithm and the subband adaptive structure with the maximal decimation. In the proposed SAP algorithm, the derived weight-updating formula for the subband adaptive filter has a simple form as compared with the normalized least mean square (NLMS) algorithm. The algorithm gives improved convergence and reduced computational complexity. The efficiency of the proposed algorithm for a colored input signal is evaluated experimentally.

In this letter, a new addressing scheme for hexagonal networks is proposed. Using the new addressing scheme, many routing algorithms designed for networks using square-based topologies such as mesh and torus can also be applied to hexagonal networks. Methods of applying the turn model to hexagonal networks are derived, with some new minimal and partial adaptive routing algorithms obtained. Simulations of the new routing algorithms under different working conditions are carried on hexagonal networks of various sizes. The results show that the proposed algorithms can offer lower packet delay and loss rate than the popular dimension order routing algorithm.

In this paper, a 2-D iteratively reweighted least squares lattice algorithm, which is robust to the outliers, is introduced and is applied to defect detection problem in textured images. First, the philosophy of using different optimization functions that results in weighted least squares solution in the theory of 1-D robust regression is extended to 2-D. Then a new algorithm is derived which combines 2-D robust regression concepts with the 2-D recursive least squares lattice algorithm. With this approach, whatever the probability distribution of the prediction error may be, small weights are assigned to the outliers so that the least squares algorithm will be less sensitive to the outliers. Implementation of the proposed iteratively reweighted least squares lattice algorithm to the problem of defect detection in textured images is then considered. The performance evaluation, in terms of defect detection rate, demonstrates the importance of the proposed algorithm in reducing the effect of the outliers that generally correspond to false alarms in classification of textures as defective or nondefective.

Metro networks are based on SONET/SDH which uses the circuit switching technology. Circuit switching is inappropriate for the Internet traffic which is very bursty nature. Therefore, metro networks can become a bottleneck. In order to resolve this problem, the IEEE 802.17 working group has proposed the Resilient Packet Ring (RPR) technology. In order to provide fairness among stations in the RPR network, two types of RPR fairness mechanisms have been defined. However, the IEEE 802.17 RPR fairness mechanisms have the problem of inefficient use of the available bandwidth after the congestion at a node has been resolved. In this paper, we propose an improved bandwidth allocation in which, after the congestion resolution at a node, the node estimates the number of effective nodes transmitting traffic, measures the remaining bandwidth and fairly allocates the available bandwidth to effective nodes. To show the performance of our proposed mechanism, we have performed simulation and show that the proposed mechanism gives higher bandwidth utilization than the existing RPR fairness mechanisms.

In this paper, we present a novel forwarding scheme to enhance communication stability based on geographic routing in mobile ad hoc networks, which is called "Position-based Heuristic Forwarding" (PHF). For alternative solutions to traditional ad hoc routings, many geographic routing algorithms have been proposed. Most of the existing routings impose a certain restriction, planarity, on the graph structure of network for delivering messages to destination definitely. PHF achieves the guaranteed packet delivery over Unit Disk Graph, which is more widely employed graph model for the study of ad hoc networks. Accordingly, to eliminate the restriction of the routing algorithms enhances the probability to deliver messages successfully in networks with high nodes' mobility rate. In the simulation of PHF, we have evaluated the performance comparisons between PHF and its related work, Greedy Perimeter Stateless Routing (GPSR) and Dynamic Source Routing (DSR), which are the prominent geographic and conventional topology-based routing protocols, respectively. The results show that PHF provides higher packet delivery success rate indicating better communication stability and equal or less overhead than these work.

We consider the classification problem to construct a classifier c:{0,1}n{0,1} from a given set of examples (training set), which (approximately) realizes the hidden oracle y:{0,1}n{0,1} describing the phenomenon under consideration. For this problem, a number of approaches are already known in computational learning theory; e.g., decision trees, support vector machines (SVM), and iteratively composed features (ICF). The last one, ICF, was proposed in our previous work (Haraguchi et al., (2004)). A feature, composed of a nonempty subset S of other features (including the original data attributes), is a Boolean function fS:{0,1}S{0,1} and is constructed according to the proposed rule. The ICF algorithm iterates generation and selection processes of features, and finally adopts one of the generated features as the classifier, where the generation process may be considered as embodying the idea of boosting, since new features are generated from the available features. In this paper, we generalize a feature to an extended Boolean function fS:{0,1,*}S{0,1,*} to allow partial knowledge, where * denotes the state of uncertainty. We then propose the algorithm ICF* to generate such generalized features. The selection process of ICF* is also different from that of ICF, in that features are selected so as to cover the entire training set. Our computational experiments indicate that ICF* is better than ICF in terms of both classification performance and computation time. Also, it is competitive with other representative learning algorithms such as decision trees and SVM.

This paper presents a modal-expansion analysis of the electromagnetically coupled coaxial dipole antenna. The analysis of the antenna problem is initially simplified using the even-odd mode excitation and then the resultant half structure is divided into two parts; one is the characterization of a coaxial feeding network and the other is the modeling of a sleeve monopole antenna driven by a coaxial line. The formally exact modal-expansion method is employed to analyze both parts. The analysis of the sleeve monopole antenna is facilitated by introducing a perfectly conducting boundary at a distance from the monopole's top end. The current distribution and input impedance of the electromagnetically coupled coaxial dipole antenna are obtained by finding expansion coefficients through enforcing the continuity of tangential field components across regional interfaces and cascading the two parts together. Numerical results for the coaxial dipole antenna's radiation characteristics are presented and discussed.

In this letter, we discussed some properties of characteristic generators for a finite Abelian group code, proved that any two characteristic generators can not start (end) at the same position and have the same order of the starting (ending) components simultaneously, and that the number of all characteristic generators can be directly computed from the group code itself. These properties are exactly the generalization of the corresponding trellis properties of a linear code over a field.

This paper proposes a low complexity composite CDMA system based on MIMO (Multiple-Input-Multiple-Output) processing and LDPC (low-density parity-check) codec based a CDMA system, which works well even if the complicated case of multipath, multiusers and short length LDPC codes. To explore the practical application, the mobile user in the composite CDMA systems is with only two antennas and adopts short length irregular LDPC codec, each user's data has been divided two LDPC encoded substreams being sent to two transmitter antennas at base station. Since the LDPC encoded substreams of reaching the mobile user are orthogonal to each other in space and time, the CDMA system performances (BER and SINR) can be improved much, but the multipath may ruin the orthogonalilty. To solve the problems, the paper provides the algorithms of main function modules of transmitter and receivers, gives a simple method to test the girth of LDPC codes, and analyzes the performance of MIMO-LDPC CDMA systems theoretically and experimentally. The simulation results show that the hybrid CDMA systems can have better performance than the conventional CDMA systems based on single transmitted antenna at a base station.