We clarify the effectiveness of receiver-side compensation in offsetting fiber Bragg grating (FBG) dispersion induced-electrical signal-to-noise ratio (SNR) degradation in a 10 Gb/s 8-channel wavelength-division multiplexing (WDM) 6,400 km transmission system. The receiver-side compensation greatly improves the SNR degradation. The allowable accumulated FBG dispersion is -400 1000ps/nm for the worst arrangement, a single FBG at the transmitter, which is about half the accumulated fiber dispersion permissible with receiver-side compensation.

A hybrid location system for a mobile station consists of a wireless-assisted GPS and a kind of cellular signals. This letter presents a location estimator improving the performance of the hybrid mobile station location for all terrain environments including inside or between buildings. An estimation structure eliminating non-line-of-sight propagation-delay error effectively improves location accuracy of the hybrid location system.

A blind equalizer which uses the differential constant modulus algorithm (DCMA) is introduced. An anchored FIR equalizer applied to a first-order autoregressive channel and updated according to the DCMA is shown to converge to the inverse of that channel regardless of the initial tap-weights and the gain along the direct path.

Adaptive beamforming, using the Conjugate Gradient Normal Equation Residual problem, is applied to a base station array, in the UTRA-TDD up-link. A Wideband Directional Channel Model is used, characterising specific micro-cell, street-type scenarios. These differ in the number of mobile terminals, grouped and placed along the street axis, and on their distances to the base station. Time- and angle-of-arrival spreads, and on-the-air interference content are the main parameters inherently varied and analysed. The average beamforming gain and signal-to-noise ratio are evaluated, also varying the number of array elements. The high number of arriving correlated and closely correlated signals, together with the composed nature of the correlation matrix in the algorithm's cost function, result in that other than the MMSE solutions may lead to the best interference suppression, for the tested scenarios. Among the several weighted interfering power components, the most relevant is due to the delayed signals from all the other links. The combination of the number of arriving orthogonal codes, time-of-arrival and angle-of-arrival spreads condition beamforming performance: the number of array elements affect performance, depending on the mobile terminal distance to the base station, and on the number of active links; for short distances and large number of users, larger time-of-arrival spread degrades beamformer performance, over the opposing effect of angle-of-arrival spread; the number of active users affects beamforming gain especially in the case that delay spreads are larger, i.e., for shorter mobile terminal distances to the base station.

We propose linearization techniques for MMIC amplifiers. The key points of these techniques are increased linearity of a newly-developed low-distortion MESFET (LD-FET) and maximized IP3 by combining the LD-FET with a high-gain depletion-mode MESFET (D-FET) with no increase in power consumption. The LD-FET is characterized by its unique channel dopant-profile prepared by a buried p-type ion-implantation and double n-type ion-implantations with high- and low-acceleration energies. This FET achieves flatter behavior in terms of mutual conductance (gm) compared with conventional MESFETs irrespective of changes in the gate bias voltage (Vgs). A self-alignment/selective ion-implantation process enables the LD-FET and D-FET to be fabricated simultaneously. This process encourages IP3 maximization of the multi-stage amplifier by appropriately combining the advantages of the two differently characterized MESFETs. We fabricated and tested a highly linearized two-stage MMIC amplifier utilizing the proposed techniques, and found that its third-order intermodulation ratio (IMR) performance was 8.7 dB better than that of conventional MMIC amplifiers at an input signal level of -20 dBm with no increase in current dissipation. The configuration constructed by using the proposed techniques equivalently reduces the current dissipation of the second stage to 1/2.72 times that of the conventional configuration, which requires a 2.72 times larger D-FET at the second stage to obtain an 8.7-dB IMR improvement. Furthermore, we were able to improve the IMR by 3.5 dB by optimizing the gate bias conditions for the LD-FET. These results confirm the validity of the proposed techniques.

This paper presents a rough sets-based method for clustering nominal and numerical data. This clustering result is independent of a sequence of handling object because this method lies its basis on a concept of classification of objects. This method defines knowledge as sets that contain similar or dissimilar objects to every object. A number of knowledge are defined for a data set. Combining similar knowledge yields a new set of knowledge as a clustering result. Cluster validity selects the best result from various sets of combined knowledge. In experiments, this method was applied to nominal databases and numerical databases. The results showed that this method could produce good clustering results for both types of data. Moreover, ambiguity of a boundary of clusters is defined using roughness of the clustering result.

This paper considers a reconfiguration problem on a processor array model based on single-and-half-track switches, which is proposed for a fault tolerance technique at the fabrication time. The focus of this paper is to achieve the optimal reconfigurability, which means that whenever there exists a solution for successful reconfiguration, the designed method can find the solution. The paper consists of two parts. In the first part, we show two essential constraints that have been assumed in most of the previous studies, and make four reconfiguration classes that differ in the assumed essential constraints. Then, we present some inclusion relations among the four reconfiguration classes. As a result, it becomes clear that the most restrictive class including most of the previous methods never achieves the truly optimal reconfigurability. In the second part, we present a reconfiguration method based on sequential routing (RMSR). Although the worst-case time complexity of the RMSR is exponential in the number of processing elements, the reconfigurability of the RMSR is optimal within the most restrictive reconfiguration class. The effectiveness of the RMSR is shown by a computer simulation.

Distributed Denial of Service (DDoS) attacks are a pressing problem on the Internet as demonstrated by recent attacks on major e-commerce servers and ISPs. Since the attack is highly distributed, an effective solution must be formulated with a distributed approach. Recently, some solutions, in which intermediate network nodes filter or shape congested traffic, have been proposed. These solutions may decrease the congested traffic, but they still cause "collateral victims problem," that is, legitimate packets may be discarded mistakenly. In this paper, we propose Active Countermeasure Platform to minimize traffic congestion and to address the collateral victim problem using the Active Networks paradigm, which incorporates programmability into intermediate network nodes. Our platform can prevent overloading of the target and consuming the network bandwidth of both the backbone and the protected site autonomously. In addition, it can improve the collateral victim problem based on user policy. This paper shows the concept of our platform, system design and evaluation of the effectiveness using a prototype.

The jaw movements can be measured by estimating the position and orientation of two small permanent magnets attached on the upper and lower jaws. It is a difficult problem to estimate the positions and orientations of the magnets from magnetic field because it is a typical inverse problem. The back propagation neural networks (BPNN) are applicable to solve this problem in short processing time. But its precision is not enough to apply to practical measurement. In the other hand, precise estimation is possible by using the nonlinear least-square (NLS) method. However, it takes long processing time for iterative calculation, and the solutions may be trapped in the local minima. In this paper, we propose a precise and fast measurement system which makes use of the estimation algorithm combining BPNN with NLS method. In this method, the BPNN performs an approximate estimation of magnet parameters in short processing time, and its result is used as the initial value of iterative calculation of NLS method. The cost function is solved by Gauss-Newton iteration algorithm. Precision, processing time and noise immunity were examined by computer simulations. These results shows the proposed system has satisfactory ability to be applied to practical measurement.

This paper describes high power density and low distortion characteristics of a novel InGaP channel field-modulating plate FET (InGaP FP-FET) under high voltage operation of over 50 V. The developed InGaP FP-FET exhibited an extremely high breakdown voltage of 100 V with an impact ionization coefficient about 103 times smaller than that of GaAs. These superior breakdown characteristics indicate that the InGaP FP-FET is one of the most desirable device structures for high-voltage high-power operation. The InGaP FP-FET delivered an output power density of 1.6 W/mm at 1.95 GHz operated at a drain bias voltage of 55 V. As power operation moves from class A to class AB, both 3rd-order intermodulation distortion (IM3) and power-added efficiency (PAE) at higher output-power region were improved, resulting from a suppressed gate leakage current near the power saturation point. These results promise that the developed InGaP FP-FET is suited for applications in which both high efficiency and low distortion are required.

This paper proposes a three-step cell search algorithm utilizing a synchronization channel (SCH) and common pilot channel (CPICH) in the forward link for OFCDM (Orthogonal Frequency and Code Division Multiplexing) broadband packet wireless access, and evaluates the cell search time performance by computer simulation. In the proposed three-step cell search algorithm, the OFCDM symbol timing, i.e., Fast Fourier Transform (FFT) window timing is estimated employing SCH or guard interval (GI) correlation in the first step. Then, the frame timing is detected by employing the SCH and the cell-specific scrambling code (CSSC) is identified by the CPICH in the second and third steps, respectively. Computer simulation results elucidate that the proposed three-step cell search algorithm achieves fast cell search time performance, i.e., cell detection probability of 90% within approximately 50 msec, assuming the number of CSSCs of 512 in a 19 hexagonal-cell model. We also clarify that there is no prominent difference in cell search time performance between the two employed SCH structures, time-multiplexed and frequency-multiplexed, assuming that the total transmit power of the SCH is the same. Based on the comparison of four substantial cell search algorithms, the GI-plus-SCH correlation method, in which FFT windowing timing detection, frame timing detection, and CSSC identification are performed by GI correlation, frequency-multiplexed SCH, and CPICH, respectively, exhibits the cell search time of approximately 44 msec at the detection probability of 90% with an optimized averaging parameter in each step.

We apply newly developed rigorous modal transmission-line theory (MTLT) to evaluate optimal design conditions on optical power coupling in grating-assisted directional couplers (GADCs) with two or three guiding channels. By defining a power distribution ratio (PDR) and coupling efficiency (CE) amenable to the rigorous analytical solutions of MTLT, we explicitly analyze the power coupling characteristics of TE modes propagating in GADCs. The numerical results reveal that the incident power is optimally coupled into the desired guiding channel if the powers of rigorous modes excited at the input boundary of grating-assisted coupler are equally partitioned.

In this paper, a VLSI architecture for lifting-based discrete wavelet transform (LDWT) is presented. Our architecture folds the computations of all resolution levels into the same low-pass and high-pass units to achieve higher hardware utilization. Due to the regular and flexible structure of the design, its area is independent of the length of the 1-D input sequence, and its latency is independent of the number of resolution levels. For the computations of analysis process of N-sample 1-D 3-level LDWT, our design takes about N clock cycles and requires 2 multipliers, 4 adders, and 22 registers. It is fabricated with TSMC 0.35-µm cell library and has a die size of 1.21.2 mm2. The power dissipation of the chip is about 0.4 W at the clock rate of 80 MHz.

In this letter, we address geometry coding of 3-D mesh models. Using a joint prediction, the encoder predicts vertex positions in the layer traversal order. After we apply the joint prediction algorithm to eliminate redundancy among vertex positions using both position and angle values of neighboring triangles, we encode those prediction errors using a uniform quantizer and an entropy coder. The proposed scheme demonstrates improved coding efficiency for various VRML test data.

In an orthogonal frequency division multiplexing (OFDM) system, the bit error performance is degraded in the presence of multiple propagation paths whose excess delays are longer than the Guard Interval (GI), because the orthogonality between subcarriers cannot be maintained. In this paper, we propose a new OFDM demodulation method with a variable-length effective symbol and a multi-stage inter-carrier interference (ICI) canceller, in order to improve the bit error performance in the presence of multipaths whose excess delays are longer than the GI. The influence of the inter-symbol interference (ISI) is eliminated by the variable-length effective symbol, and then the ICI component is reduced by the multi-stage ICI canceller. The principle of the proposed method is explained, and the performance of the proposed method is then evaluated by computer simulation. The results show that the proposed method improves the system availability under more various multipath fading environments without changing the system parameters.

In OFDM-CDMA down link (base-to-mobile) transmissions, each user's transmit data symbol is spread over a number of orthogonal sub-carriers using an orthogonal spreading sequence defined in the frequency-domain. The radio propagation channel is characterized by a frequency- and time-selective multipath fading channel (which is called a doubly selective multipath fading channel in this paper). Frequency-domain equalization is necessary at the receiver to restore orthogonality among different users. This requires accurate estimation of the time varying transfer function of the multipath channel. Furthermore, the noise enhancement due to orthogonality restoration degrades transmission performance. In this paper, pilot-aided threshold detection combining (TDC) is presented that can effectively suppress the noise enhancement. If the estimated channel gain is smaller than the detection threshold, it is replaced with the detection threshold in the frequency equalization. There exists an optimal threshold that can minimize the bit error rate (BER) for a given received Eb/N0. The average BER performance of OFDM-CDMA down link transmissions using the TDC is evaluated by computer simulations. It is found that TDC using optimum detection threshold can significantly reduce the BER floor and outperforms DS-CDMA with ideal rake combining.

This paper presents the theoretical analysis of subband adaptive array combining cyclic prefix transmission scheme (SBAA-CP) in multipath fading environment. The exact expressions for optimal weights, array outputs and the output signal to interference plus noise ratio (SINR) are derived. The analysis shows that use of the cyclic prefix data transmission scheme can significantly improve the performance of subband adaptive array (SBAA). An example of implementing SBAA-CP as a software antenna is also presented.

This paper devises a sophisticated approach to the performance estimation of an embedded hardware-software codesign system at the architecture level, which intends to optimize the hardware-software configuration in terms of processing time, power dissipation, and hardware cost. A distinctive feature of this approach consists in constructing a performance estimation model proper to each component of an embedded system, such as CPU core, RAM/ROM, cache memory, and application-specific hardware, by taking account of not only the functional performance but also the data transfer. The proposed estimation schemes are incorporated into an existing instruction set simulator, so that the actual performance can be estimated accurately at the architecture level. The experimental results demonstrate that the performance estimation approach enables the precise design decision at the architecture level, which greatly contributes toward enhancing the design ability dedicatedly for mobile appliances.

In ATM networks, call processing on switches can be greatly simplified by using the concept of virtual path (VP); and good resource management strategies ensure that virtual channel connections (VCC) can be rapidly and efficiently established. In order to have good system performance, several methods of constructing virtual paths and strategies of allocating and managing resources should be considered. In this paper, several multicast strategies with dynamic routing are used and applied to the metropolitan LATA network. For the VP-based network, dynamic routing is also applied, and those strategies are discussed and investigated to show the versatility of the approach. Some results using dynamic multicast routing, such as call blocking rate, VP utilization, and VP adjustment rate, are obtained for the different strategies by simulation experiments.

Scanning near-field optical microscopy (SNOM) combined with Kelvin force microscopy (KFM) using a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film as an integrated deflection sensor have been developed. We applied the frequency modulation (FM) detection method to this setup to increase the detection sensitivity of electrostatic forces between a probe tip and a sample. Latex particles dispersed in a polyvinylalcohol (PVA) thin film deposited onto a glass substrate were stably imaged with the SNOM while both local optical and electrical properties of a ferroelectric thin film were successfully investigated.