The paper is concerned with an identification-based predistortion scheme for compensating nonlinearity of high power amplifiers (HPA). The identification algorithms for the Wiener-Hammerstein nonlinear model are developed in the frequency domain. By approximately modeling the nonlinear distortion part in HPA by polynomial or spline functions, and introducing linear distortion parts in the input and output of the nonlinear element, the iterative identification schemes are proposed to estimate all the uncertain parameters and to construct an inverse system for the predistortion.

A heterogeneous parallel computing environment consisting of different types of workstations and communication links plays an important role in parallel computing. In many applications on the system, collective communication operations are commonly used as communication primitives. Thus, design of the efficient collective communication operations is the key to achieve high-performance parallel computing. But the heterogeneity of the system complicates the design. In this paper, we consider design of an efficient gather operation, one of the most important collective operations. We show that an optimal gather schedule is found in O(n2k-1) time for the heterogeneous parallel computing environment with n processors of k distinct types, and that a nearly-optimal schedule is found in O(n) time if k=2.

This paper proposes a gradient ascent learning algorithm for the elastic net approach to the Traveling Salesman Problem (TSP). The learning model has two phases: an elastic net phase, and a gradient ascent phase. The elastic net phase is equivalent to gradient descent of an energy function, and leads to a local minimum of energy that represents a good solution to the problem. Once the elastic net gets stuck in local minima, the gradient ascent phase attempts to fill up the valley by modifying parameters in a gradient ascent direction of the energy function. Thus, these two phases are iterated until the elastic net gets out of local minima. We test the algorithm on many randomly generated travel salesman problems up to 100 cities. For all problems, the systems are shown to be capable of escaping from the elastic net local minima and generating shorter tour than the original elastic net.

We have classified parenchymal echo patterns of cirrhotic liver into four types, according to the size of hypo echoic nodular lesions. The NN (neural network) technique has been applied to the characterization of hepatic parenchymal diseases in ultrasonic B-scan texture. We employed a multilayer feedforward NN utilizing the back-propagation algorithm. We extracted 1616 pixels in the two-dimensional regions. However, when a large area is used, input data becomes large and much time is needed for diagnosis. In this report, we used DCT (discrete cosine transform) for the feature extraction of input data, and compression. As a result, DCT was found to be suitable for compressing ultrasonographic images.

In a previous study about a combinatorial optimization problem solver using neural networks, since the Hopfield method, convergence to the optimum solution sooner and with more certainty is regarded as important. Namely, only static states are considered as the information. However, from a biological point of view, dynamical systems have attracted attention recently. Therefore, we propose a "dynamical" combinatorial optimization problem solver using hysteresis neural networks. In this paper, the proposed system is evaluated by the N-Queen problem.

The main purpose of our method is to obtain realistic worst-case delay in statistical timing analyses. This paper proposes a method of statistical delay calculation based on measured intra-chip and inter-chip variabilities. We present a modeling and extracting method of transistor characteristics for the intra-chip variability and the inter-chip variability. In the modeling of the intra-chip variability, it is important to consider a gate-size dependence by which the amount of intra-chip variation is affected. This effect is not captured in a statistical delay analysis reported so far. Our method proposes a method for modeling of the device variability and statistical delay calculation with consideration of the size dependence, and uses a response surface method (RSM) to calculate a delay variation with low processing cost. We evaluate the accuracy of our method, and we show some experimental results the variation of a circuit delay characterized by the measured variances of transistor currents.

Several lifting implementation techniques for invertible deniterlacing are proposed in this paper. Firstly, the invertible deinterlacing is reviewed, and an efficient implementation is presented. Next, two deinterlacer-embedded lifting architectures of discrete wavelet transforms (DWT) is proposed. Performances are compared among several architectures of deinterlacing with DWT. The performance evaluation includes dual-multiplier and single-multiplier architectures. The number of equivalent gates shows that the deinterlacing-embedded architectures require less resources than the separate implementaion. Our experimental evaluation of the dual-multiplier architecture results in 0.8% increase in the gate count, whereas the separate implementation of deinterlacing and DWT requires 6.1% increase from the normal DWT architecture. For the proposed single-multiplier architecture, the gate count is shown to result in 4.5% increase, while the separate counterpart yields 10.7% increase.

The 2-vertex-connectivity augmentation problem for specified vertices (2VCA-SV) is defined as follows: Given an undirected graph G=(V,E), a subgraph G0=(V,E') of G, a specified set of vertices S V and a weight function w:E R^+ (nonnegative real numbers), find a set E" E-E' with the minimum total weight, such that G0+E"=(V,E' E") has at least two internally disjoint paths between any pair of vertices in S. In this paper, we propose an O(|V||E|+ |V|2 log |V|) time algorithm 2-ABIS, whose performance ratio is 2 (3, respectively), for 2VCA-SV if G0 has a connected component containing S (otherwise).

MRAM-writing circuitry to compensate for the thermal variation of the magnetization-reversal current is proposed. The writing current of the proposed circuitry is designed to decrease in proportion to an increase in temperature. This technique prevents multiple-write failures from degrading 1 Gb MRAM yield where the standard deviation of magnetization-reversal current variation from other origins is less than 5%.

Intelligent paging uses the sequential paging technique with additional user information in order to reduce the paging delay cost and the paging load cost. Our proposed paging scheme uses distribution density information of users as required additional user information. This letter addresses an optimal paging sequence and introduces formulas to calculate the paging costs. These formulas are necessary to evaluate the performance of location management. The paging delay cost and the paging load cost for the proposed paging scheme and two other paging schemes are calculated and numerical analyses for these paging schemes are performed. Results show how the paging delay cost and the paging load cost vary as either the paging request arrival rates or the number of cells in an LA increases. The proposed paging scheme is more efficient in view of both the paging delay cost and the paging load cost.

The present paper addresses the design of manufacturing systems. A resource planning and task allocation problem is proposed, and a multi-agent system for this problem is discussed. In the multi-agent system, an agent exists for each resource and for each operation. The proposed multi-agent system improves the quality of resulting plans by the learning of these agents.

We propose a new algorithm for blind source separation (BSS), in which frequency-domain independent component analysis (FDICA) and time-domain ICA (TDICA) are combined to achieve a superior source-separation performance under reverberant conditions. Generally speaking, conventional TDICA fails to separate source signals under heavily reverberant conditions because of the low convergence in the iterative learning of the inverse of the mixing system. On the other hand, the separation performance of conventional FDICA also degrades significantly because the independence assumption of narrow-band signals collapses when the number of subbands increases. In the proposed method, the separated signals of FDICA are regarded as the input signals for TDICA, and we can remove the residual crosstalk components of FDICA by using TDICA. The experimental results obtained under the reverberant condition reveal that the separation performance of the proposed method is superior to those of TDICA- and FDICA-based BSS methods.

A formula-based approach for extracting the inductance of on-chip VLSI interconnections is presented. All of the formulae have been previously proposed and are well-known, but the degrees of accuracy they provide in this context have not previously been examined. The accuracy of the equations for a 0.1 µm technology node is evaluated through comparison of their results with those of 3-D field solvers. Comprehensive evaluation has proven that the maximum relative error of self- and mutual inductances as calculated by the formulae are less than 5% for parallel wires and less than 13% for angled wires, when wire width is limited to no more than 10 times the minimum. When applied to a realistic example with 43 wire segments, a program using the formula-based approach extracts values more than 60 times faster than a 3-D field solver.

This paper presents a BER performance derivation considering imperfect channel estimation for a pilot-aided coherent forward link of W-CDMA system under multipath Rayleigh fading channels. In the forward link of the W-CDMA system, pilot signal is usually used for coherent demodulation. In this paper, the maximum likelihood estimator, Wiener filter, and moving average filter are applied to estimate the channel effect due to mobile speed and frequency offset. Then, we concentrate on determining optimal parameter values of the estimators such as the observation length, delay parameters for causal/non-causal filter, and filter resolution. Also it is verified that these parameters are closely associated with the performance, hardware complexity, and characteristics of OVSF code. In particular, effect of data rate and filter resolution on the BER performance is analyzed in more detail. In addition, we show the performance comparison between the estimators considering various imperfections. Finally, we verify the derived BER by using an extensive Monte-Carlo computer simulation.

In this paper, we propose two channel allocation schemes for supporting voice and multimedia traffic in hierarchical cellular systems. They are guaranteed to satisfy the required quality of service for multimedia traffic in accordance with their characteristics such as a mobile velocity for voice calls and a delay tolerance for multimedia calls. In the first, only slow-speed voice calls are allowed to overflow from macrocell to microcell and only adaptive multimedia calls can overflow from microcell to macrocell after reducing their bandwidth to the minimum channel bandwidth. In the second, in addition to the first scheme, non-adaptive multimedia calls can occupy the required channel bandwidth through reducing the channel bandwidth of adaptive multimedia calls. The proposed schemes are analyzed using the 2-dimensional Markov model. Through computer simulations, it is shown that the proposed schemes yield a significant improvement in terms of the forced termination probability of handoff calls. In particular, the second decreases the blocking probability of new calls as well as the forced termination probability of handoff calls.

In this paper, we propose a new IEEE 802.11 based multichannel MAC protocol, which satisfies a single transceiver constraint and which is still compatible with the IEEE 802.11 standard. Our proposed protocol does not need any additional transceivers, and we can make use of the current IEEE 802.11 hardware for the implementation of our multichannel protocol. We propose and investigate two kinds of channel selection algorithms, these are, the sender based channel selection scheme and the receiver based channel selection scheme. We evaluate the TCP performance over our proposed multichannel MAC protocol by the simulations taking account of the overhead, the time taken by changing the frequency channel and the time taken by the carrier sense in each channel. It is shown that our proposed scheme improves the performance significantly with a single transceiver. It is shown that the overhead costs are quite large in the multichannel MAC protocol, and the sender based channel selection scheme achieves better performance than that of the receiver based channel selection scheme in most cases. It is also shown that there exists a break-even value of the PLL synthesizer lockup time if we compare with the single channel IEEE 802.11 MAC protocol.

Following the developments in the use of ID-based schemes and smart cards, Yang and Shieh proposed two password authentication schemes to achieve two purposes: (1) to allow users to choose and change their passwords freely, and (2) to make it unnecessary for the remote server to maintain a directory of passwords or a verification table to authenticate users. Recently, Chan and Cheng showed that Yang and Shieh's timestamp-based password authentication scheme is insecure against forgery. In this paper, we point out that Chan and Cheng's forgery attack can not work. Thus, we further examine the security of Yang and Shieh's password authentication schemes and find that they are insecure against forgery because one adversary can easily pretend to be a valid user and pass the server's verification which allows the adversary to login to the the remote server.

Mirroring of network servers has been considered to be effective for load balancing. However, the cost of setting up new mirror servers is enormously high. In this paper, we propose a dynamic file allocation model with a simple mirroring function for handling significant changes of network traffic in the Internet. According to the load fluctuation, we can dynamically reallocate files using this model. We show that our model accomplishes satisfactory performance and reduces cost by adding a simple mirroring function to all existent servers instead of setting up mirror servers afresh.

Existing routing protocols for mobile ad hoc networks assume that all nodes have the same transmission range. In other words, the mobile ad hoc network has symmetric links, which means that two neighboring nodes A and B are within the transmission range of one another. However, since nodes consume battery power independently according to their computing and communication load, there exist asymmetric links, which means that node A is within node B's transmission range, but not vice versa. In this paper, two approaches are presented to support routing in the existence of asymmetric links: GAHA (GPS-based Hop-by-hop Acknowledgment) and GAPA (GPS-based Passive Acknowledgment) schemes. Both GAHA and GAPA can be applied to any routing protocols by utilizing GPS (Global Positioning System) location information. Simulation results reveal that both GAHA and GAPA protocols cope well in the presence of asymmetric wireless links and nodes' mobility.

This paper proposes a gesture recognition method which uses higher order local autocorrelation (HLAC) features extracted from PARCOR images. To extract dominant information from a sequence of images, we apply linear prediction coding technique to the sequence of pixel intensities and PARCOR images are constructed from the PARCOR coefficients of the sequences of the pixel values. From the PARCOR images, HLAC features are extracted and the sequences of the features are used as the input vectors of the Hidden Markov Model (HMM) based recognizer. Since HLAC features are inherently shift-invariant and computationally inexpensive, the proposed method becomes robust to changes in the person's position and makes real-time gesture recognition possible. Experimental results of gesture recognition are shown to evaluate the performance of the proposed method.