This paper describes the design of a programmable QAM transceiver for VDSL applications. A 12-b DAC with 64-dB spurious-free dynamic range (SFDR) at 75-MS/s and an 11-b ADC with 72.3-dB SFDR at 70-MS/s are integrated in this complete physical layer IC. A digital IIR notch filter is included in order to not interrupt existing amateur radio bands. The proposed dual loop AGC adjusts the gain of a variable gain amplifier (VGA) to obtain maximum SNR while avoiding saturation. Using several low power techniques, the total power consumption is reduced to 300-mW at 1.8-V core and 3.3-V I/O supplies. The transceiver is fabricated in a 0.18-µm CMOS process and the chip size is 5-mm 5-mm. This VDSL transceiver supports 13-Mbps data rate over a 9000-ft channel with a BER < 10-7.

In this paper, we present a group communication protocol that achieves total ordering message delivery for mobile computing systems with multiple overlapping groups. Our mechanism is an efficient adaptation of the propagation-tree technique to the mobile computing environments. It takes advantages of the capability of stationary mobile support stations to overcome the deficiencies associated with mobile devices. We construct the propagation tree based on the stationary stations, rather than the mobile hosts. As a result, mobile hosts are relieved of the excessive load of forwarding messages and communications on wireless channels are confined to transmitting messages to destination processes. This is important considering that the bandwidth of the wireless channels is limited. Moreover, the proposed protocol employs a mechanism to synchronize transmissions within a wireless cell. This serves to avoid redundant transmissions of a message in a wireless network in an attempt to achieve better utilization of the network bandwidth. Our mechanism relies on a handoff operation to deal with mobility of mobile devices. The handoff procedure ensures a smooth integration of a mobile host into a new cell, while preserving reliability of communication and the total ordering property of message delivery.

We propose a new method to introduce the Minimum Description Length (MDL) criterion to the automatic generation of non-uniform, context-dependent HMM topologies. Phonetic decision tree clustering is widely used, based on the Maximum Likelihood (ML) criterion, and only creates contextual variations. However, the ML criterion needs to predetermine control parameters, such as the total number of states, empirically for use as stop criteria. Information criteria have been applied to solve this problem for decision tree clustering. However, decision tree clustering cannot create topologies with various state lengths automatically. Therefore, we propose a method that applies the MDL criterion as split and stop criteria to the Successive State Splitting (SSS) algorithm as a means of generating contextual and temporal variations. This proposed method, the MDL-SSS algorithm, can automatically create adequate topologies without such predetermined parameters. Experimental results for travel arrangement dialogs and lecture speech show that the MDL-SSS can automatically stop splitting and obtain more appropriate HMM topologies than the original one.

Breaking arcs occurring between Ag or Cu electrical contact pairs in DC 56 V/7 A resistive circuit are observed with a high-speed camera (1000 frames/s). As a result, the increase of brightness of the arc-emitted light synchronizes with the increase of arc current in the latter half of arc duration. For the case of Ag contacts, the brightness increases in entire region of the breaking arc with sudden increase of the arc current. On the other hand, the increase of the intensity for Cu contacts occurs in not only entire discharge region but also anode spot region significantly.

In this article, we will present a modification attack and a dictionary attack to subvert the security of the Tseng scheme and the Ku-Wang scheme. As we know, no existing schemes of simple authenticated key agreement protocols can successfully withstand our modification attack.

We measured the optical propagation characteristics during rainfall over a 72-m propagation distance at the wavelengths of 0.78, 1.55, and 2.0 µm. In addition to the common attenuations, we observed sudden drops (dips) in the received optical power, which affect communication errors. The temporal interval of most dips is approximately 1 ms.

Decentralized and unstructured peer-to-peer (P2P) networks such as Gnutella are attractive for large-scale information retrieval and search systems because of their scalability, fault-tolerance, and self-organizing nature. Because of this decentralized architecture, however, traditional P2P keyword search systems are difficult to globally share useful semantic knowledge among nodes. As a result, traditional P2P keyword search systems cannot support semantic search (support only naive text-match search). In this paper, we describe a design of the semantic P2P keyword search system. We exploit the semantics of correlation among keywords rather than synonym. The key mechanism is query expansion, where a received query is expanded based on keyword relationships. Keyword relationships are improved through search and retrieval processes and each relationship is shared among nodes holding similar data items. This semantic P2P search system has two main advantages. First, expanding search results through query expansion increases the possibility of locating desired data items which would not be found by traditional P2P search systems due to the keywords' textual mismatch. Second, keyword relationships originally introduced for query expansion, can be used for result ranking. Our main challenges are 1) managing keyword relationships in a fully decentralized manner and 2) maintaining the quality of search results, while suppressing result implosion. We also describe the prototype implementation and evaluation of the semantic P2P search system.

A chaotic neural network consisting of chaotic neurons exhibits such rich dynamical behaviors as nonperiodic associative memory. But it is difficult to distinguish the stored patterns from others, since the chaotic neural network shows chaotic wandering around the stored patterns. In order to apply the nonperiodic associative memory to information search or pattern identification, it is necessary to control chaotic dynamics. In this paper, we propose a delay feedback control method for the chaotic neural network. Computer simulation shows that, by means of the control method, the chaotic dynamics in the chaotic neural network are changed. The output sequence of the controlled network wanders around one stored pattern and its reverse pattern.

Techniques for automatic program recognition, at the algorithmic level, could be of high interest for the area of Software Maintenance, in particular for knowledge based reengineering, because the selection of suitable restructuring strategies is mainly driven by algorithmic features of the code. In this paper an automated hierarchical concept parsing recognition technique, and a formalism for the specification of algorithmic concepts, is presented. Based on this technique, the design and development of ALCOR, a production rule based system for automatic recognition of algorithmic concepts within programs, aimed at support of knowledge based reengineering for high performance, is presented.

In this paper we consider the Feedback-Guided Dynamic Loop Scheduling (FGDLS) method that was proposed by Bull. The method uses a feedback-guided mechanism to schedule a parallel loop within a sequential outer loop. The execution times and the scheduling bounds at a outer iteration are used to find the scheduling bound of the next outer iteration. In this way FGDLS achieves an optimal load balance. Two algorithms have been proposed so far by Tabirca et al. In this article we will review these two algorithms and will give a comparison between their performances.

A new excitation enhancement technique based on a harmonic model is proposed in this paper to improve the speech quality of low-bit-rate speech coders. This technique is employed only in the decoding process of speech coders and improves high-frequency components of excitation. We develop the procedure of harmonic model parameters estimation and harmonic generation and apply the technique to a current state-of-art low bit rate speech coder. Experiments on spectrum reading and spectrum distortion measurement show that the proposed excitation enhancement technique improves speech quality.

Cluster computation has been used in the applications that demand performance, reliability, and availability, such as cluster server groups, large-scale scientific computations, distributed databases, distributed media-on-demand servers and search engines etc. In those applications, multicast can play the vital roles for the information dissemination among groups of servers and users. This paper proposes a set of novel efficient fault-tolerant multicast routing algorithms on hypercube interconnection of cluster computers using multicast shared tree approach. We present some new algorithms for selecting an optimal core (root) and constructing the shared tree so as to minimize the average delay for multicast messages. Simulation results indicate that our algorithms are efficient in the senses of short end-to-end average delay, load balance and less resource utilizations over hypercube cluster interconnection networks.

Traditional Web cache servers based on HTTP and ICP infrastructure tend to have higher hardware and management cost, have difficulty in availability, automatic and dynamic reconfiguration, and may have slow links to some users. We find that peer-to-peer technology can help solve these problems. The peer cache service (PCS) we proposed here leverages each peer's local cache, similar access patterns, fully distributed coordination, and fast communication channels to enhance response time, scale of cacheable objects, and availability. Moreover, incorporating goals and strategies such as making the protocol lightweight and mutually compatible with existing cache infrastructure, supporting mobile devices, undertaking dynamic three-level caching, and exchanging cache meta-information further improve the effectiveness and differentiate our work from other similar-at-first-glance P2P Web cache systems.

Interconnection networks play a crucial role in the performance of massively parallel computers. Hierarchical interconnection networks provide high performance at low cost by exploring the locality that exists in the communication patterns of massively parallel computers. A Hierarchical Torus Network (HTN) is a 2D-torus network of multiple basic modules, in which the basic modules are 3D-torus networks that are hierarchically interconnected for higher level networks. The static network performance of the HTN has already been studied and has been shown to be good. Dynamic communication performance has been evaluated under uniform traffic pattern but not under non-uniform traffic patterns. In this paper, we present a deadlock-free routing algorithm for the HTN using 3 virtual channels and evaluate the network's dynamic communication performance under three non-uniform traffic patterns, using the proposed routing algorithm. We evaluate the dynamic communication performance of HTN, H3D-mesh, H3D-torus, TESH, and mesh networks by computer simulation. We find that the dynamic communication performance of HTN is better than that of the H3D-mesh, H3D-torus, TESH, and mesh networks.

We developed a new millimeter-wave plastic chip size package (CSP) to operate up to 100 GHz by using a thin-film substrate. It has a flip-chip distributed amplifier with inverted microstrip lines and the amplifier has a bandwidth of beyond 110 GHz. The transmission line on the substrate consists of grounded coplanar waveguides that yield low insertion loss and high isolation characteristics in coupled lines even in mold resin in comparison with conventional microstrip lines. The CSP amplifier achieved a gain of 7.8 dB, a 3-dB bandwidth of 97 GHz, and operated up to 100 GHz. To the best of our knowledge, this value is the highest operating frequency reported to date for a distributed amplifier sealed in a plastic CSP. We also investigated the transmission characteristics of lead-free solder bumps through experiments by assemblying CSPs on printed circuit boards and modeling them so that we could design the packages accurately.

This paper proposes the use of the ratio of wavelet extrema numbers taken from the horizontal and vertical counts respectively as a texture feature, which is called aspect ratio of extrema number (AREN). We formulate the classification problem upon natural and synthesized texture images as an optimization problem and develop a coevolving approach to select both scalar wavelet and multiwavelet feature spaces of greater discriminatory power. Sequential searches and genetic algorithms (GAs) are comparatively investigated. The experiments using wavelet packet decompositions with the innovative packet-tree selection scheme ascertain that the classification accuracy of coevolutionary genetic algorithms (CGAs) is acceptable enough.

In this paper, we propose a statistical method of evaluating the pronunciation proficiency of English words spoken by Japanese. We analyzed statistically the utterances to note a combination that has a high correlation between an English teacher's score and certain acoustic features. We obserbed that the phoneme recognition rates (correct rate and accuracy) were the best measure of pronunciation proficiency, and the likelihood ratio of English phoneme acoustic models to phoneme acoustic models adapted by Japanese was the second best measure. The effective measure which was highly correlated with the English teacher's score was the combination of the likelihood for American native models, likelihood for English models adapted by Japanese, the best likelihood for arbitrary sequences of acoustic models, phoneme recognition rate and the rate of speech. We obtained a correlation coefficient of 0.81 with an open data for vocabulary and 0.69 with open data for speaker at the five words set level, respectively. The coefficient was higher than the correlation between humans' scores, 0.65. In the 15 words set level which corresponds to one or two sentences, we obtained the correlation coefficient of 0.86 with open data for the speaker.

In ad-hoc on-demand routing algorithm, when a route is broken a relay node must perform error transaction and the source node must do rerouting to discover an alternate route. It is important to construct a stable route when route discovery occurs. In this paper, we use relative speeds among nodes as a measure of node mobility. Our routing algorithm chooses nodes of lower relative speed as relay nodes. As a result of our simulation, when there is one session in the network, our proposing algorithm can reduce the number of route breaks: about 3 times smaller than DSR. And our proposing algorithm can deliver more packets than DSR: 18% higher rate. However, in the congested traffic situation our algorithm should be improved.

The development of multi-channel digital broadcasting has generated a demand not only for new services but also for smart and highly functional capabilities in all broadcast-related devices. This is especially true of TV receivers on the viewer's side. With the aim of achieving a friendly interface that anybody can use with ease, we built a prototype spoken dialogue interface for TV operation based on data collected by using Wizard of Oz method. At the current stage of our research, we are using this system to investigate the usefulness and problem areas of an interactive voice interface for TV operation.

Recent growth in computer communications has led to an increased requirement for high-speed backbone networks. In such high-speed networks, the principle adopted for a time-sensitive flow control mechanism should be that of autonomous decentralized control. In this mechanism, each node in a network manages its local traffic flow only on the basis of the local information directly available to it, although it is desirable that the individual decisions made at each node lead to high performance of the network as a whole. In our previous studies, we have investigated the behavior of local packet flows and the global performance achieved when a node is congested, and proposed the diffusion-type flow control model. However, since we used a simple and homogeneous network model in the evaluation, the results cannot be generalized. In this paper, we propose an extension of the diffusion-type flow control model in order to apply it to networks with inhomogeneous configurations. We show simulation results for two cases: different propagation delays and multiple bottlenecks. Both results show that the proposed diffusion-type flow control achieves high and stable performance even if the network is congested.