We propose using a soft decision-directed least-mean-square algorithm in a code-aided equalization scheme for fading channels. Soft-output Viterbi algorithm (SOVA) is modified and applied to strengthen the second-stage equalizer adaptation in the scheme. Simulation results are presented for bit error rate performance in a multipath environment for various normalized fade rates. The proposed equalizer scheme is shown to provide significant bit error rate improvement compared to conventional equalization schemes.

An L-band low quiescent current and low distortion SiGe heterojunction bipolar transistor (HBT) driver amplifier having a self base bias control circuit is described. Since the size of this bias circuit is small and it does not need an external control circuit, it is easy to be integrated with the driver amplifier on a single chip. According to the output power level, the self base bias control circuit, which is the combination of a constant base voltage circuit and p-metal oxide semiconductor (MOS) FET current mirror with a constant current source, automatically controls the base voltage, and allows low quiescent current at low output power level and low distortion at high output power level. The simulated results show that the driver amplifier having the self base bias control circuit achieves 1 dB power compression point (P1 dB) improvement of 2.4 dB compared with the driver amplifier having a conventional constant base voltage under the same quiescent current condition. The fabricated driver amplifier with the proposed bias circuit shows high P1 dB of 15.0 dBm with low quiescent current of 15.3 mA.

This paper elucidates the optimum bandwidth per sub-carrier in the reverse link for multicarrier (MC)/DS-CDMA using a 10 to 80-MHz bandwidth in a multipath fading channel with numerous resolved multipaths, taking into account all major effects, i.e., the improvement in the Rake time diversity effect and the degradation in the path search and the channel estimation due to multipath interference (MPI). In the paper, we assume a broadband channel model with the maximum delay time of up to approximately 1 µsec simulating a microcell with the radius of less than 1 km in an urban area. The simulation results clarify that the improvement in the radio link performance is almost saturated at a bandwidth greater than approximately 40 MHz when the spreading factor of the channel is SF=32, and the best performance is achieved at the bandwidth of approximately 20-40 MHz when SF=4, employing two-branch antenna diversity reception (an average equal power delay profile and an exponential decay power delay profile are assumed, where the number of multipaths is changed from 12 to 48 for both profiles). This is generated by the tradeoff between the improvement in the Rake time diversity effect and the increased MPI in addition to the degradation in accuracy of the path search and channel estimation associated with a lower average received signal-to-interference plus background noise power ratio. Therefore, we conclude that MC/DS-CDMA, where each sub-carrier has the bandwidth of approximately 20-40 MHz, is one of the most promising candidates for broadband packet wireless access in the reverse link.

Incremental evolution with learning (IEWL) is proposed for the development of autonomous robots, and the validity of the method is evaluated with a real mobile robot to acquire a complex task. Development of the control system for a complex task, i.e., approaching toward a target object by avoiding obstacles in an environment, is incrementally carried out in two-stage. In the first-stage, controllers are developed to avoid obstacles in the environment. By using acquired knowledge of the first-stage, controllers are developed in the second-stage to approach toward the target object by avoiding obstacles in the environment. It is found that the use of learning in conjunction with incremental evolution is beneficial for maintaining diversity in the evolving population. The performances of two controllers, one developed by IEWL and the other developed by incremental evolution without learning (IENL), are compared on the given task. The experimental results show that robust performance is achieved when controllers are developed by IEWL.

To elucidate the mechanism of topographic organization, we propose a simple topographic mapping formation model from generalized cell layer to generalized cell layer. Here generalized cell layer means that we consider arbitrary cell neighborhood relations. In our previous work we investigated a topographic mapping formation model between one dimensional cell layers. In this paper we extend the cell layer structure to any dimension. In our model, each cell takes a binary state value and we consider a class of learning principles which are extensions of Hebb's rule and Anti-Hebb's rule. We pay special attention to correlation type learning rules where a synaptic weight value is increased if pre and post synaptic cell states have the same value. We first show that a mapping is stable with respect to the correlational learning if and only if it is semi-embedding. Second, we introduce a special class of weight matrices called band type and show that the set of band type weight matrices is strongly closed and such a weight matrix can not yield a topographic mapping. Third, we show by computer simulations that a mapping, if it is defined by a non band type weight matrix, converges to a topographic mapping under the correlational learning rules.

The purpose of this study is to show the chaotic features of rhythmic joint movement. Depending on the experimental conditions, one (or both) elbow angle(s) was (were) measured by one (or two) goniometer(s). Pacing was provided for six different frequencies presented in random order. When the frequency of the pace increased, the fractal dimension and first Lyapunov exponent tended to increase. Moreover, the first Lyapunov exponent obtained positive values for all of the observed data. These results indicate that there is chaos in rhythmic joint movement and that the larger the frequency, the more chaotic the joint movement becomes.

New methods for digital image watermarking based on the characteristics of vector quantization (VQ) are proposed. In contrast with conventional watermark embedding algorithms to embed only one watermark at a time into the original source, we present one algorithm to embed multiple watermarks for copyright protection. The embedding and extraction processes are efficient for implementing with conventional VQ techniques, and they can be accomplished in parallel to shorten the processing time. After embedding, embedder would output one watermarked reconstruction image and several secret keys associated with the embedded watermarks. These secret keys are then registered to the third party to preserve the ownership of the original source in order to prevent the attackers from inserting counterfeit watermarks. Simulation results show that under no attacks, the embedded watermarks could be perfectly extracted. If there are some intentional attacks in our simulation, all the watermarks could survive to protect the copyrights. Therefore, we are able to claim the robustness, usefulness, and ease of implementation of our algorithm.

We propose a DPC-PA (Distributed Power Control with Power Assignment) algorithm to speed up the process of finding a feasible power set for multimedia CDMA wireless networks. We prove that given a feasible configuration, the power set of the DPC-PA algorithm will converge to a feasible power set which achieves equality in a set of linear equations. We also found, from numerical experiments, that the DPC-PA algorithm can find a feasible power set (if there is one) much faster than the distributed power control algorithm without power assignment.

This paper introduces the concept of hierarchical testability of data paths for delay faults. A definition of hierarchically two-pattern testable (HTPT) data path is developed. Also, a design for testability (DFT) method is presented to augment a data path to become an HTPT one. The DFT method incorporates a graph-based analysis of an HTPT data path and makes use of some graph algorithms. The proposed method can provide similar advantages to the enhanced scan approach at a much lower hardware overhead cost.

The understanding of instruction set usage in typical DOS/Windows applications plays a very important role in designing high performance x86 compatible microprocessors. This paper presents the tools to such analysis, the analysis results, and their implications on the design of a RISC-based superscalar processor for efficient x86 instruction execution. The analyzed results are used to optimize the execution of frequently executed instructions and micro operations.

In this paper, we present a new approach to the construction of a set of binary sequences with a zero-correlation zone. The set consists of n pairs of binary sequences and the length of each binary sequence is n2(m+2) for some integers m and n. The Hadamard sequences with length n are used to construct the set. Any sequence in the set has 2(m+1) subsequences, each of length 2n. The author proves that any two subsequences are orthogonal if they belong to different pairs of binary sequences in the set.

A new four-quadrant (4Q) Multiplier complementally using linear and saturation regions of MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is proposed for the wide dynamic range and superior flexibility of the input range. This multiplier operates in the region except for the threshold voltage VT to zero. The validity of the proposed circuit is confirmed through HSPICE simulation.

Carbon-gold (C-Au) film was formed by co-operation process of plasma CVD and sputtering with using methane and Ar mixture gas and gold plate discharge electrode. Refractive index of 3.1 for the film was obtained at Au atom content of 5.5 atomic%. The optical transmittance was improved significantly in the visible light wavelength range compared to the C-S-Au film reported previously. Au atom distribution in the C-Au film and the electronic polarizabilities were discussed in the relation to the refractive index.

The radix-64 encoding scheme was used to reduce the number of partial products in the 5454 CMOS parallel multiplier. The transistor counts, the chip area and the power-delay product were reduced by 28%, 22%, and 17%, respectively, compared to any of the published 5454 CMOS parallel multipliers. A redundant binary (RB) number system was used to represent any of the 65 multiplying coefficients as a RB number which consists of two of 9 fundamental multiplying coefficients and their complements. The resultant RB partial products were added by using optimized RB adders. The total transistor count of the proposed multiplier was 43,579. The chip area in 0.25 µm CMOS process with 5 metal layers was 0.99 mm2. The power consumption and the multiplication time were 111 mW and 6.9 ns, respectively.

The surface potential built across vacuum deposited phthalocyanine (Pc) films on aluminum electrode was investigated by means of electro-modulation spectroscopy. The sandwich-type cells with thin air gap, which becomes a good insulator were used in order to avoid the influence of charge injection. The existence of the surface potential at the metal/organic-material interface induced 1f referenced electro-reflectance (ER) signals. As a result, the surface potential built across vacuum deposited Pc films on aluminum electrode was estimated to be 1.25 V.

We propose a new receiver structure to mitigate interpath interference (IPI) in W-CDMA systems. We model IPI in RAKE combining as intersymbol interference (ISI) and use a two-stage receiver structure. The first stage is a RAKE receiver and the second stage is an equalizer. In cases of multi-code transmission, interference among code channels causes extra impairments which can not be modelled as ISI. Under these circumstances, they are estimated by using decisions from the first stage and then subtracted from the input of the equalizer. The residual interference is equivalent to ISI and can be mitigated by the equalizer. Simulation results show that the proposed receiver provides very promising performance in low spreading factor W-CDMA.

The optical recording on an azopolymer surface by the optical fiber probe with a 100 nm diameter aperture was demonstrated. The 150 nm diameter pit was formed by the optical fiber probe coupled with a 50 ns pulse of 10 mW and 488 nm wavelength coherent light.

A visual secret sharing scheme (VSSS) is one of secret sharing schemes for images. Droste showed the method for constructing VSSS based on basis matrices whose contrast was high. Koga, Iwamoto, and Yamamoto also proposed the method for constructing a lattice-based VSSS and its polynomial representation. It is known that many good VSSSs are not in the class of lattice-based VSSSs. In this paper, we show the well-defined polynomial representation of a VSSS based on permuting different matrices for black-white images. The necessary and sufficient condition of the existence of a VSSS based on permuting different matrices can be obtained from the proposed polynomial representation. This condition is useful for constructing a good VSSS. We also point out that without additional data, it is possible to achieve member verification by using a VSSS. Using the proposed polynomial representation, the probability of detecting a cheater is analyzed.

This paper describes a method for hands-free speech recognition, and particularly for the simultaneous recognition of multiple sound sources. The method is based on the 3-D Viterbi search, i.e., extended to the 3-D N-best search method enabling the recognition of multiple sound sources. The baseline system integrates two existing technologies--3-D Viterbi search and conventional N-best search--into a complete system. Previously, the first evaluation of the 3-D N-best search-based system showed that new ideas are necessary to develop a system for the simultaneous recognition of multiple sound sources. It found two factors that play important roles in the performance of the system, namely the different likelihood ranges of the sound sources and the direction-based separation of the hypotheses. In order to solve these problems, we implemented a likelihood normalization and a path distance-based clustering technique into the baseline 3-D N-best search-based system. The performance of our system was evaluated through experiments on simulated data for the case of two talkers. The experiments showed significant improvements by implementing the above two techniques. The best results were obtained by implementing the two techniques and using a microphone array composed of 32 channels. More specifically, the Word Accuracy for the two talkers was higher than 80% and the Simultaneous Word Accuracy (where both sources are correctly recognized simultaneously) was higher than 70%, which are very promising results.

Transmit beamforming is a promising way to increase the downlink capacity of wireless networks. Since all users are coupled via their radiation patterns, the beamforming vectors must be optimized along with power control. It is necessary to balance the signal-to-interference levels according to individual QoS requirements. This problem leads back to the minimization of the infinity-norm of a certain vector and has first been studied by Gerlach and Paulraj in [1]. It has been assumed that the optimum solution can be obtained by minimizing the 1-norm instead, thereby leading to a new problem, which is generally easier to handle. The analytical and numerical results in this paper, however, indicate that this conjecture is generally not valid. We characterize the case where the 1-norm solution also solves the infinity-norm problem. In particular, it is shown that for the special case of a 2-user scenario, both optimization problems are indeed equivalent and a closed-form solution can be given. The analytical results provide new insights into the problem of coupled downlink beamforming and offer a useful approach to the design of efficient and reliable algorithms.