For suppressing inter symbol interference, the support vector machine mutliuser detector (SVM-MUD) was adopted as a nonlinear method in direct sequence code division multiple access (DS-CDMA) signals transmitted through multipath channels. To solve the problems of the complexity of SVM-MUD model and the number of support vectors, based on recursive least squares support vector machine (RLS-SVM) and Riemannian geometry, a new algorithm for nonlinear multiuser detector is proposed. The algorithm introduces the forgetting factor to get the support vectors at the first training samples, then, uses Riemannian geometry to train the support vectors again and gets less improved support vectors. Simulation results illustrated that the algorithm simplifies SVM-MUD model at the cost of only a little more bit error rate and decreases the computational complexity. At the same time, the algorithm has an excellent effect on suppressing multipath interference.

This paper proposes a disjoint path selection scheme for Generalized Multi-Protocol Label Switching (GMPLS) networks with Shared Risk Link Group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the total number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many SRLG members is rarely selected as the shortest path. Simulation results show that WSRLG finds more disjoint paths than the conventional k-shortest path algorithm. In addition, since WSRLG searches for the weight of the SRLG factor by using a modified binary search algorithm while satisfying the required number of disjoint paths between source and destination nodes, it can find cost-effective disjoint paths.

The tectonic activities that precede significant earthquakes release electromagnetic (EM) waves that can be used as earthquake precursors. We have been observing EM radiation in the ELF (extremely low frequency) band at about 40 observation stations in Japan for predicting significant earthquakes. The recorded signals contain, however, several noise components generated from the ionosphere, human activity, and so on. Most background noise in observed signal is attributed to lightning in the tropics. This paper proposes method based on PCA (principal component analysis) to extract signals from large data sets. The good performance of the proposed method is confirmed.

In this paper, we consider the problem of estimating the time-varying directions-of-arrival (DOAs) of coherent narrowband cyclostationary signals impinging on a uniform linear array (ULA). By exploiting the cyclostationarity of most communication signals, we investigate a new computationally efficient subspace-based direction estimation method without eigendecomposition and spatial smoothing (SS) processes. The proposed method uses the inherently temporal property of incident signals and a subarray scheme to decorrelate the signal coherency and to suppress the noise and interfering signals, while the null subspace is obtained from the resulting cyclic correlation matrix through a linear operation. Then an on-line implementation of this method is presented for tracking the DOAs of slowly moving coherent signals. The proposed algorithm is computationally simple and has a good tracking performance. The effectiveness of the proposed method is verified through numerical examples.

This paper first presents an active integrated antenna configuration designed for broadband mobile wireless access systems using the 25-GHz band. This active integrated antenna comprises a microstrip antenna array and RF front-end circuits adopting spatial power combining schemes for reduced power consumption of the power amplifiers. Furthermore, the antenna and RF circuits are integrated into each side of a thick copper backing plate and both are connected through microstrip line /slot transitions. The developed active integrated antenna achieves the output power of 14.6 dBm and a noise figure of less than 5 dB. The wireless system using the developed active integrated antenna achieves a 6-dB improvement in the packet error rate compared to that using a passive antenna with the same array design as the active integrated antenna. Furthermore, we obtained the first license of the active integrated antenna for commercial use in high-speed wireless communication systems in Japan.

A constant voltage/constant current (CV/CC) parallel operation heterojunction bipolar transistor (HBT) power amplifier (PA) configuration is presented, and its design method is described. A resistor base feed (CC mode) HBT is connected to an inductor base feed (CV mode) HBT in parallel, and compensates the gain expansion of the CV mode HBT due to near class-B operation. By adding CC mode HBT, the total quiescent current can be decreased from 32 mA to 23 mA with adjacent channel leakage power ratio (ACPR) < -40.0 dBc. At the maximum output power region, the fabricated PA achieves output power (Pout) of 26.8 dBm and power added efficiency (PAE) of 42.0% with ACPR of -40.0 dBc, and shows the comparable performances with a conventional PA using CV mode HBT.

The present letter introduces a new approach to the construction of a set of ternary arrays having a zero-correlation zone. The proposed array set has a zero-correlation zone for both periodic and aperiodic correlation functions. As such, the proposed arrays can be used as a finite-size array having a zero-correlation zone. The proposed array sets can be constructed from an arbitrary Hadamard matrix. The member size of the proposed array set is close to the theoretical upper bound.

Adaptive arrays have been recognized as an attractive mean for overcoming multipath fading and interference rejection in the field of mobile communications. In, an adaptive array applicable to single-user spread spectrum (SS) systems has been proposed. In this system, any a priori information concerning incoming signal, even the spreading code and synchronization, is not necessary while it achieves equalizing, beamforming and despreading of a received signal, simultaneously. In this paper, we propose a multistage blind adaptive array antenna based on the above-mentioned adaptive algorithm in order to realize blind signal processing that is applicable to multi-user SS systems. Behavior and performance of the proposed multistage system are examined through computer simulations.

In this paper, a spatio-temporal error concealment method of transmission errors for improving visual quality over the wireless channel is proposed, which makes use of geometric information extracted from the surrounding blocks. The geometric information is an isophote that is curves of constant intensity of image. To improve visual quality during video communication, the proposed method smoothly connects the isophotes disconnected due to transmission error using a genetic algorithm (GA) with an isophote constraint. In the proposed method, the error concealment problem is modeled as an optimization problem, which in our case, is solved by a cost function with isophotes constraint that is minimized using a GA. Experimental results shows more visually realistic than other error concealment methods.

We newly propose a stable algorithm for blind source separation (BSS) combining multistage ICA (MSICA) and linear prediction. The MSICA is the method previously proposed by the authors, in which frequency-domain ICA (FDICA) for a rough separation is followed by time-domain ICA (TDICA) to remove residual crosstalk. For temporally correlated signals, we must use TDICA with a nonholonomic constraint to avoid the decorrelation effect from the holonomic constraint. However, the stability cannot be guaranteed in the nonholonomic case. To solve the problem, the linear predictors estimated from the roughly separated signals by FDICA are inserted before the holonomic TDICA as a prewhitening processing, and the dewhitening is performed after TDICA. The stability of the proposed algorithm can be guaranteed by the holonomic constraint, and the pre/dewhitening processing prevents the decorrelation. The experiments in a reverberant room reveal that the algorithm results in higher stability and separation performance.

This paper proposes a traffic-driven optical IP networking architecture for service provider networks. Its design is derived from the optical GMPLS architecture, which provides high performance but is not scalable since both optical paths and IP routes need to be arranged in a mesh topology. To improve scalability, we first modified the configuration so that paths and routes can be arranged in a tree topology. However, this approach may degrade performance due to traffic concentration at each tree's root. To prevent such performance degradation, we further modified the architecture so that both cut-through optical paths and cut-through IP routes can be assigned reactively, according to traffic demand, and these can work together in cooperation. As a result, our architecture achieves both high performance and scalability, in that the whole network performance can be maintained without a massive increase in the number of optical paths and IP routes, even if the number of customer networks grows.

This paper focuses on the investigation of RoF link noise influence in an ubiquitous antenna system, which is composed of multiple radio base stations (RBSs) deployed over the service area, central control station (CCS) and radio-on-fiber (RoF) link that connects RBSs to the CCS. The ubiquitous antenna system is capable of receiving multiple mobile terminals simultaneously operating at the same frequency channel by making effective use of joint detection. However, in the ubiquitous antenna system, since signals are transmitted from RBSs to CCS via the RoF link, the noise generated at the RoF link, such as relative intensity noise, inter modulation distortion, optical shot noise and thermal noise, may become dominant factors degrading the performance. The performance evaluations considering optical link noise is given by computer simulations. Computer simulation results show that more than 19 dB of RoF link Eb/N0 is required for achieving sufficient performance.

The first implementations of X-band AlGaN/GaN HEMT single-ended frequency doublers are presented in this paper. Two types of fundamental frequency signal reflector schemes have been demonstrated for the frequency doubler application. Open-circuited quarter-wavelength microstrip line at the fundamental frequency is utilized for the reflector in a conventional way. In the other architecture a printed antenna is employed as a radiator as well as a novel fundamental frequency reflector. A microstrip rectangular patch antenna operating at the second harmonic frequency of the doubler was designed and integrated with AlGaN/GaN HEMT based on active integrated antenna design concept. Using AlGaN/GaN HEMT with 1 mm gate periphery, two 4 to 8 GHz frequency doublers were designed by the described design methodologies, fabricated, and tested. For the conventional frequency doubler, a conversion gain of 0.6 dB and with an output power of 15 dBm was observed. A conversion gain of 5 dB and an output power of 25 dBm with embedded antenna gain were achieved at a drain voltage of 12 V for the doubler integrated with the patch antenna.

A new approach to correcting the array amplitude failure by a combination of B-spline techniques and genetic algorithms is proposed. Some array elements indicate the control knots for a B-spline curve by their nominal positions and amplitudes; others distribute the excitation amplitudes according to the sampling points on the curve. The inherent smoothness of the B-spline curves reduce the effect of excessive coupling between adjacent elements. Genetic algorithms are used to search for a quasi-optimized B-spline curve to produce the ultimate amplitude distribution for correcting the array failure. To demonstrate the method's effectiveness, simulation results for correcting failures with three- and four-element failures are presented.

In this letter, we take advantage of both types of Interactive and Batch services by considering a hybrid multimedia-on-demand (MOD) system which provides both services. Also, we propose two serving methods with an incentive charging scheme to optimize the coexistence of both services. Numerical results show that the proposed hybrid system outperforms both individual systems. In particular, the system provider receives more revenue by serving more users concurrently, while the users have a better viewing experience due to higher availability of contents.

This paper presents an algorithm for fingerprint image restoration using Digital Reaction-Diffusion System (DRDS). The DRDS is a model of a discrete-time discrete-space nonlinear reaction-diffusion dynamical system, which is useful for generating biological textures, patterns and structures. This paper focuses on the design of a fingerprint restoration algorithm that combines (i) a ridge orientation estimation technique using an iterative coarse-to-fine processing strategy and (ii) an adaptive DRDS having a capability of enhancing low-quality fingerprint images using the estimated ridge orientation. The phase-only image matching technique is employed for evaluating the similarity between an original fingerprint image and a restored image. The proposed algorithm may be useful for person identification applications using fingerprint images.

In this letter, we propose a new error protection technique for JPEG2000-coded images and also present its evaluation over an OFDM channel. The method exploits the layer structure of the JPEG2000 codestream, a data embedding technique and a forward error correcting code. The main header and data in the top layer are duplicated and protected by the error correcting code. These data are then embedded into the bottom layer for error recovery purposes. Our method offers several features: preserves the same codestream structure as the one in the JPEG2000 part 1 standard, provides multilevel error protection, and can be combined with the existing error resilience technique. Hence, the method accommodates the new requirements for wireless JPEG2000 (JPWL/JPEG2000 part 11).

Multiple access interference and near-far effect cause the performance of the conventional single user detector in DS/CDMA systems to degrade. Due to high complexity of the optimum multiuser detector, suboptimal multiuser detectors with less complexity and reasonable performance have received considerable attention. In this paper we apply the classic and a new modified genetic algorithm for multiuser detection of DS/CDMA signals. It is shown that the classic genetic algorithm (GA) reaches an error floor at high signal to noise ratios (SNR) while the performance of proposed modified GA is much better than the classic one and is comparable to the optimum detector with much less complexity. The results hold true for AWGN and fading channels. We also describe another GA called as meta GA to find the optimum parameters of the modified GA. We compare the performance of proposed method with the other detectors used in CDMA.

User authentication is necessary on the Internet and in mobile communications to protect the legal user's rights. One-time password authentication methods change the verifier every time by sending the present verifier along with the next verifier. However, such methods risk impersonation attacks because those protocols use two verifiers every session. The OSPA (Optimal Strong-Password Authentication) method is a one-time password method which prevents stolen-verifier problems, replay attacks, and denial of service attacks. In this letter, we devise an impersonation attack on the OSPA method and discuss how to break down the OSPA method.

The present paper introduces a new approach to the construction of a class of ternary sequences having a zero-correlation zone. The cross-correlation function of each pair of the proposed sequences is zero for phase shifts within the zero-correlation zone, and the auto-correlation function of each proposed sequence is zero for phase shifts within the zero-correlation zone, except for zero-shift. The proposed sequence set has a zero-correlation zone for periodic, aperiodic, and odd correlation functions. As such, the proposed sequence can be used as a finite-length sequence with a zero-correlation zone. A set of the proposed sequences can be constructed for any set of Hadamard sequences of length n. The constructed sequence set consists of 2n ternary sequences, and the length of each sequence is (n+1)2m+2 for a non-negative integer m. The periodic correlation function, the aperiodic correlation function, and the odd correlation function of the proposed sequences have a zero-correlation zone from -(2m+1-1) to (2m+1-1). The member size of the proposed sequence set is of the theoretical upper bound of the member size of a sequence having a zero-correlation zone. The ratio of the number of non-zero elements to the the sequence length of the proposed sequence is also .