This paper presents a new Frequency Shift Keying (FSK) demodulation method using the Short Time-Discrete Fourier Transform (ST-DFT) analysis to combat large frequency offset with time variation in low earth orbit (LEO) satellite communications systems. This demodulation method can demodulate the received signal only by searching for the instantaneous spectrum energy peaks without complicated carrier recovery. In addition, it is insensitive to the signal-to-noise ratio (SNR) degradation caused by the excessively wide bandwidth of the receiver front-end band pass filter. Furthermore, the ST-DFT analysis combined with a differential encoding scheme gives FSK demodulation method a potential robustness against large and fast time-varying frequency offset.

This paper presents a three layer over-the-cell (OTC) routing algorithm for standard cells with nonuniform OTC routing capacities in standard cell design. Since the number of available routing tracks on the second metal layer of OTC varies column by column, the proposed OTC routing method can effectively utilize the OTC regions. The proposed router performs two types of OTC routing. For the OTC regions near the channel, it performs planar routing. For the OTC regions far from the channel, it performs H-V routing on the second and third layers. Combining planar and H-V routings, the router can utilize the OTC effectively, that could hardly be achieved by existing algorithms. We also formulate the problem of selecting planar routable nets on the third layer as the maximum weighted planar routable net selection problem with nonuniform routing capacity, and propose an optimal algorithm. Experimental results show that the proposed router produces small height layouts as compared to those produced by the routers based on the existing cell model with uniform OTC routing capacity.

Research in very low-bit rate coding has made significant advancements in the past few years. Most recently, the introduction of the MPEG-4 proposal has motivated a wide variety of a approaches aimed at achieving a new level of video compression. In this paper we review progress in VLBV categorized into 3 main areas. (1) Waveform coding, (2) 2D Content-based coding, and (3) Model-based coding. Where appropriate we also described proposals to the MPEG-4 committee in each of these areas.

This study clarifies the effects of network complexity and network map transformation on the ability of network managers to use graphic network displays. Maps of Japan and the United States with outlines of their respective prefectures or states were displayed on a CRT. Each map displayed a fictitious network of nodes and their interconnections. These networks were two-level hierarchical and non-meshed, meaning that each low-level node was connected to a single high-level node, but not all high-level nodes were linked together. The subjects, task was to identify a path between two low-level nodes. In each trial, two low-level nodes were highlighted, and the subject attempted to find the shortest path between these nodes. This was done by using a mouse to select intermediate nodes. Completing a path required a minimum of 4 node traversals. Three variables were manipulated. First, the number of nodes was defined as the total number of low-level nodes in a network (70, 150, or 200). The second variable was the level of transformation. Very densely populated areas of the maps were systematically transformed to reduce congestion. There were three levels of transformation. The final variable was the country map used, that is, the map of Japan and the map of the United States. Several behavioral measures were used. The most informativ. appeared to be the time required to complete a path (the response time), and how often subjects returned to previous portions of a path (back-ups). For both of these measures, the data pattern was essentially the same. Increasing the number of nodes hurts performance. This was particularly pronounced when the map of Japan was tested. However, as the level of transformation increased, this effect was substantially reduced or completely eliminated. The results are discussed in terms of engineering rules and guidelines for designing graphical network representations.

This paper presents an improved pragmatic approach to coded modulation design which provides higher coding gains especially for very noisy channels including those with Rayleigh fading. The signal constellation using four equally utilized dimensions implemented with two correlative carrier frequencies is adopted to enhance the performance of the pragmatic approach previously proposed by Viterbi et al.. The proposed scheme is shown to perform much better by analysis of system performance parameters and extensive computer simulation for practical channel conditions. The bandwidth and power efficiencies are also analyzed and discussed to provide more design flexibility for different communications environments.

Unlike the time-consuming contour tracking method of snakes [5] which requires a considerable number of iterated computations before contours are successfully tracked down, we present a faster and accurate model-based landmarks" tracking method where a single iteration of the dynamic programming is sufficient to obtain a local minimum to an integral measure of the elastic and the image energy functionals. The key lies in choosing a relatively small number of salient land-marks", or features of objects, rather than their contours as a target of tracking within the image structure. The landmarks comprising singular points along the model contours are tracked down within the image structure all inside restricted search areas of 41 41 pixels whose respective locations in image structure are dictated by their locations in the model. A Manhattan distance and a template corner detection function of Singh and Shneier [7] are used as elastic energy and image energy respectively in the algorithm. A first approximation to the image contour is obtained in our method by applying the thin-plate spline transformation of Bookstein [2] using these landmarks as fixed points of the transformation which is capable of preserving a global shape information of the model including the relative configuration of landmarks and consequently surrounding contours of the model in the image structure. The actual image contours are further tracked down by applying an active edge tracker using now simplified line search segments so that individual differences persisting between the mapped model contour are substantially eliminated. We have applied our method tentatively to portraits of a class album to demonstrate the effectiveness of the method. Our experiments convincingly show that using only about 11 feature points our method provides not only a much improved computational complexity requiring only 0.94sec. in CPU time by SGI's indigo2 but also more accurate shape representations than those obtained by the snakes methods. The method is powerful in a problem domain where the model-based approach is applicable, possibly allowing real time processing because a most time consuming algorithm of corner template evaluation can be easily implemented by parallel processing firmware.

Hybrid image coding method is one of the most promising methods for efficient coding of moving images. The method makes use of jointly motion-compensated prediction and orthogonal transform like DCT. This type of coding scheme was adopted in several world standards such as H.261 and MPEG in ITU-T and ISO as a basic framework [1], [2]. Most of the work done in motion-compensated prediction has been based on a block matching method. However, when input moving images include complicated motion like rotation or enlargement, it often causes block distortion in decoded images, especially in the case of very low bit-rate image coding. Recently, as one way of solving this problem, some motion-compensated prediction methods based on an affine transform or bilinear transform were developed [3]-[8]. These methods, however, cannot always express the appearance of the motion in the image plane, which is projected plane form 3-D space to a 2-D plane, since the perspective transform is usually assumed. Also, a motion-compensation method using a perspective transform was discussed in Ref, [6]. Since the motion detection method is defined as an extension of the block matching method, it can not always detect motion parameters accurately when compared to gradient-based motion detection. In this paper, we propose a new motion-compensated prediction method for coding of moving images, especially for very low bit-rate image coding such as less than 64 kbit/s. The proposed method is based on a perspective transform and the constraint principle for the temporal and spatial gradients of pixel value, and complicated motion in the image plane including rotation and enlargement based on camera zooming can also be detected theoretically in addition to translational motion. A computer simulation was performed using moving test images, and the resulting predicted images were compared with conventional methods such as the block matching method using the criteria of SNR and entropy. The results showed that SNR and entropy of the proposed method are better than those of conventional methods. Also, the proposed method was applied to very low bit-rate image coding at 16 kbit/s, and was compared with a conventional method, H.261. The resulting SNR and decoded images in the proposed method were better than those of H.261. We conclude that the proposed method is effective as a motion-compensated prediction method.

The importance sampling simulation technique has been exploited to obtain an accurate estimate for a very small probability which is not tractable by the ordinary Monte Carlo simulation. In this paper, we will investigate the simulation for a sample average of an output sequence from a Markov chain. The optimal simulation distribution will be characterized by the Kullback-Leibler divergence of Markov chains and geometric properties of the importance sampling simulation will be presented. As a result, an effective computation method for the optimal simulation distribution will be obtained.

There are many kinds of transmission lines such as uniform, nonuniform and nonlinear ones terminated by linear and/or nonlinear subnetworks. The nonuniform transmission lines are crucial in integrated circuits and printed circuit boards, because these circuits have complex geometries and layout between the multi layers, and most of the transmission lines possess nonuniform characteristics. On the other hand, the nonlinear transmission line have been focused in the fields of communication and instrumentation. Here, we present a new numerical method for analyzing nonuniform and nonlinear transmission lines with linear and/or nonlinear terminations. The waveforms at any points along the lines are described by the Fourier expansions. The partial differential equations representing the circuit are transformed into a set of ordinary differential equations at each frequency component, where for nonlinear transmission line, the perturbation technique is applied. The method is efficiently applied to weakly nonlinear transmission line. The nonuniform transmission lines terminated by a nonlinear subnetwork are analyzed by hybrid frequency-domain method. The stability for stiff circuit is improved by introducing compensation element. The efficiency of our method is illustrated by some examples.

Recently, there have been intensive studies on protocol methods and applications of short range inter-vehicle communication network (SR-IVCN) and systems. The purpose of the studies is to improve the safety of road traffic systems and the smooth control of the traffic flow by providing information to vehicles. Spread spectrum (SS) communication systems are able to simultaneously communicate and measure the distance between the terminals, thus it is advantageous to apply the spread spectrum technique to inter-vehicle communications. This paper assumes that the vehicles incidentally close to each other, form and manage a locally autonomous decentralized dynamic network. An R-ALOHA (Reservation-ALOHA) protocol for the spread spectrum inter-vehicle communication network using head spacing information is proposed which improve the conventional slot reservation methods. Since the near-far problem in SS communication is one reason for the degradation of system performance, this proposed scheme is shown to improve the efficiency of communication. The performance of the proposed system in the environment where the vehicles are assumed to run freely on a highway is verified by computer simulation. It is shown that inter-vehicle communication can be smoothly carried out between one vehicle and the surrounding vehicles using the propose method.

Personal communication systems (PCS) have more signalling traffic than conventional fixed networks and require large-scale databases to manage users' profiles, which are sets of data items, such as the location the user is currently visiting and the user's authentication key, necessary for a PCS user to be provided with PCS services. This paper focuses on inter-network roaming in PCS environments. In designing a PCS supporting roaming service, it is essential to avoid increased signalling traffic and data searching time in the database. We first identify the appropriate domains for three routing schemes-Direction Routing, Redirection Routing, and Look-ahead Routing-from the viewpoints of the number of signals for inter-network roaming and roaming probability. We do this for two kinds of PCS database network architecture, Home Location Register (HLR) and Visitor Location Register (VLR), and show that Look-ahead Routing is the best scheme for the HLR network architecture (considering the number of signals for intra-network and inter-network database access) and that in the VLR network architecture, the decreasing of the roaming probability expands domains for which Redirection Routing is appropriate. We also propose a generic PCS data model that inter-network roaming interfaces can use to search effectively for a user's profile. The data model clarifies the contents of a set of data items which share certain characteristics, data items that the contents compose, and the relationships (data structures) between sets of data items. The model is based on the X. 500 series recommendations, which are applied for an Intelligent Network. We also propose a data structure between sets of data items using the directory information tree and show the ASN. 1 notations of the data model.

The problem of test generation for VLSI circuits computationally requires prohibitive costs. Parallel processing on a multiprocessor system is one of available methods in order to speedup the process for such time-consuming problems. In this paper, we analyze the performance of parallel test generation for combinational circuits. We present two types of parallel test generation systems in which the communication methods are different; vector broadcasting (VB) and fault broadcasting (FB) systems, and analyze the number of generated test vectors, the costs of test vector generation, fault simulation and communication, and the speedup of these parallel test generation systems, where the two types of communication factors; the communication cut-off factor and the communication period, are applied. We also present experimental results on the VB and FB systems implemented on a network of workstations using ISCAS'85 and ISCAS'89 benchmark circuits. The analytical and experimental results show that the total number of test vectors generated in the VB system is the same as that in the FB system, the speedup of the FB system is larger than that of the VB, and it is effective in reducing the communication cost to switch broadcasted data from vectors to faults.

Recently, considerable attention has been devoted to the combination of direct sequence-code division multiple access (DS-CDMA) and multi-carrier (MC) modulation for high bit rate indoor wireless systems. In this work we consider the downlink of a cellular MC DS-CDMA system. In particular, we evaluate the performance of some detection schemes considering typical indoor radio channels. Channel estimation techniques are investigated and an effective sub-channel estimation technique is proposed. Moreover, we compare the performance of two equalization techniques combined with two space diversity combining schemes. The results show that good performance can be obtained by a post-detection diversity selection scheme combined with a MMSE equalization technique; moreover, if a proper guard time is selected, performance is almost independent of the number of paths of the channel's impulse response. Results are given in terms of BER obtained by means of analytical computations and simulations.

This paper develops an efficient mechanism for extracting primary information requests from 'Seek-Object' type query messages. The mechanism consists of three steps. The first step extracts sentences which signal that the query is 'Seek-Object' type by recognizing distinctive surface expressions. The second step, biased by the expression patterns, analyzes their internal structures. The third step integrates these fragments by a partial discourse processing and represents writers' goal-directed information request; as these sentences often include referential expressions and the referred expressions are in background goal descriptions. We claim the mechanism can extract information requests fairly accurately, by showing evaluation results.

The objective of this paper is to find a parametric representation for the vocal-tract log-area function that is directly and simply related to basic acoustic characteristics of the human vocal-tract. The importance of this representation is associated with the solution of the articulatory-to-acoustic inverse problem, where a simple mapping from the articulatory space onto the acoustic space can be very useful. The method is as follows: Firstly, given a corpus of log-area functions, a parametric model is derived following a factor analysis technique. After that, the articulatory space, defined by the parametric model, is filled with approximately uniformly distributed points, and the corresponding first three formant frequencies are calculated. These formants define an acoustic space onto which the articulatory space maps. In the next step, an independent component analysis technique is used to determine acoustic and articulatory coordinate systems whose components are as independent as possible. Finally, using singular value decomposition, acoustic and articulatory coordinate systems are rotated so that each of the first three components of the articulatory space has major influence on one, and only one, component of the acoustic space. An example showing how the proposed model can be applied to the solution of the articulatory-to-acoustic inverse problem is given at the end of the paper.

This paper discusses a massively parallel interconnection scheme for multithreaded architecture and introduces a new class of direct interconnection networks called the hierarchical Multidimensional Directed Cycles Ensemble (hMDCE). Its suitability for massively parallel systems is discussed. The network is evolved from the Multidimensional Directed Cycles Ensemble (MDCE) network, where each node is substituted by lower-level sub-networks. The new network addresses some serious problems caused by the increasing scale of parallel systems, such as longer latency, limited throughput and high implementation cost. This paper first introduces the MDCE network and then presents and examines in detail the hierarchical MDCE network. Bisection bandwidth of hMDCE is considerably reduced from its ancestor MDCE and the network performs significantly higher throughput and lower latency under some practical implementation constraints. The gate count and delay time of the compiled circuit for the routing function are insignificant. These results reveal that the hMDCE network is an important candidate for massively parallel systems interconnection.

There is a growing demand for high reliability beyond what current RAID can provide and there are various levels of user demand for data reliability. An efficient data placement scheme called RM2 has been proposed in [10], which makes a disk array system resistant to double disk failures. In this paper, we consider how to choose an optimal striping unit for RM2 particularly when no workload information is available except read/write ratio. For experimental purposes, we develop a disk array simulator incorporating RM2 as one of the data placement schemes including other schemes of RAID levels. In the case of disk read operations, it is shown that RM2 has an optimal striping unit of 4/3T for large requests and 8/3T for small requests, where T represents the size of a single track. We have also shown that, if any disk write operations are involved, an optimal striping unit becomes 1/3T for large requests and 8/3T for small requests.

The medial axis transform (MAT) is an image representation scheme. For a binary image, the MAT is defined as a set of upright maximal squares which consist of pixels of value l entirely. The MAT plays an important role in image understanding. This paper presents a parallel algorithm for computing the MAT of an n n binary image. We show that the algorithm can be performed in O(log n) time using n2/log n processors on the EREW PRAM and in O(log log n) time using n2/log log n processors on the common CRCW PRAM. We also show that the algorithm can be performed in O(n2/p2 + n) time on a p p mesh and in O(n2/p2 + (n log p)/p) time on a p2 processor hypercube (for 1 p n). The algorithm is cost optimal on the PRAMs, on the mesh (for 1 p n) and on the hypercube (for 1 p n/log n).

This paper presents a method for mechanically transforming a parallel algorithm on an original network so that the algorithm can work on a target network. It is assumed that the networks are of cube-type such as the shuffle-exchange network, omega network, and hypercube. Were those networks isomorphic to each other, the algorithm transformation is an easy task. The proposed transformation method is based on a novel graphembedding scheme <φ: δ, κ, π, ψ>. In addition to the dilating operation δ of the usual embedding scheme <φ: δ>, the novel scheme uses three primitive graph-transformation operations; κ (= δ-1) for contracting a path into a node, π for pipelining a graph, and ψ (= π-1) for folding a pipelined graph. By applying the primitive operations, the cube-type networks can be transformed so as to be isomorphic to each other. Relationships between the networks are represented by the composition of applied operations. With the isomorphic mapping φ, an algorithm in a node of the original network can be simulated in the corresponding node(s) of the target network. Thus the algorithm transformation is reduced to routine work.

THe decimation-in-time (DIT) and the decimation-in-frequency (DIF) algorithms are the most well-known fast algorithms for computing the discrete Fourier transform(DFT). These algorithms constitute the basis of the fast Fourier transform (FFT) implementations, including the pipeline implementation and other parallel configurations. This paper derives an alternative generalization of the algorithms which applies for sequences whose lengths are not a power of two. The treatment is consistent with the radix-two DIF and DIT algorithms, and the generalization is useful for utilizing the accumulated technologies of the FFT algorithm for such sequences.