The number of customers of a service for Internet access from cellular phones in Japan has been explosively increasing for some time. We analyze the relation between the number of customers and the volume of traffic, with a view to finding clues to the structure of human relations among the very large set of potential customers of the service. The traffic data reveals that this structure is a scale-free network, and we calculate the exponent that governs the distribution of node degree in this network. The data also indicates that people who have many friends tend to subscribe to the service at an earlier stage. These results are useful for investigating various fields, including marketing strategies, the propagation of rumors, the spread of computer viruses, and so on.

This paper proposes a new configuration of the Doherty amplifier by introducing digital signal processing that realizes a high efficiency over a wide range of output power. The configuration includes two branches; one branch has a class AB amplifier as the carrier amplifier and the other has two class B amplifiers in cascade as the peak amplifier. Each branch is directly controlled by the digital signal processing unit. The unit controls input power allocation to each branch by a method derived from equations characterizing the carrier and the peak constituent amplifiers. The method includes the compensation of the amplifier for degradation due to nonlinearities. The output power of each constituent amplifier is adjusted by drain DC biases. Calculated characteristics agree well with those obtained by the measurement of a fabricated proposed amplifier, whose efficiency is higher than that of the conventional class AB power amplifiers. Furthermore, a simulation for the OFDM signal specified by the radio LAN shows that the amplifier has sufficient linearity, and that the efficiency exceeds 20% at the output of 20 dBm.

This paper describes an analysis of IP-network traffic in terms of the time variation of self-similarity. To get a comprehensive view in analyzing the degree of long-range dependence (LRD) of IP-network traffic, this paper used a self-organizing map, which provides a way to map high-dimensional data onto a low-dimensional domain. Also, in the LRD-based analysis, this paper employed detrended fluctuation analysis (DFA), which is applicable to the analysis of long-range power-law correlations or LRD in non-stationary time-series signals. In applying this method to traffic analysis, this paper performed two kinds of traffic measurement: one based on IP-network traffic flowing into NTT Musashino R&D center (Tokyo, Japan) from the Internet and the other based on IP-network traffic flowing through at an interface point between an access provider (Tokyo, Japan) and the Internet. Based on sequential measurements of IP-network traffic, this paper derived corresponding values for the LRD-related parameter α of measured traffic. As a result, we found that the characteristic of self-similarity seen in the measured traffic fluctuated over time, with different time variation patterns for two measurement locations. In training the self-organizing map, this paper used three parameters: two α values for different plot ranges, and Shannon-based entropy, which reflects the degree of concentration of measured time-series data. We visually confirmed that the traffic data could be projected onto the map in accordance with the traffic properties, resulting in a combined depiction of the effects of the degree of LRD and network utilization rates. The proposed method can deal with multi-dimensional parameters, projecting its results onto a two-dimensional space in which the projected data positions give us an effective depiction of network conditions at different times.

This paper presents an efficient LSP quantizer implementation for low bit-rate coders. The major feature of the quantizer is that it uses a truncated cepstral distance criterion for the code selection procedure. This approach has generally been considered too computationally costly. We utilized the quantizer with a moving-average predictor, two-stage-split vector quantizer and delayed decision. We have investigated the optimal parameter settings in this case and incorporated the quantizer thus obtained into an ITU-T 4-kbit/s speech coding candidate algorithm with a bit budget of 21 bits. The objective performance is better than that with a conventional weighted mean-square criterion, while the complexity is still kept to a reasonable level. The paper also describes the codebook design and techniques that were employed to achieve robustness in noisy channel conditions.

An adaptive 4-state phase-frequency detector (PFD) for clock and data recovery (CDR) PLL of non return to zero (NRZ) data is presented. The PLL achieves false-lock free operation with rapid frequency-capture and wide bit-rate-capture range. The variable bit rate operation is achieved by adaptive delay control of data delay. Circuitry and overall architecture are described in detail. A z-Domain analysis is also presented.

This paper presents a methodology for optimizing the layout of on-chip spiral inductors using structural parameters and design frequency in a response surface method. The proposed method uses scattering parameters (S-parameter) to express inductor characteristics, and hence is independent of spiral geometries and equivalent circuit models. The procedure of inductor optimization is described, and a design example is presented.

In this paper, we propose a transmission method of the synchronized streaming data in digital broadcasting environment. The ancillary data that is used in the data broadcasting can be classified into three types: asynchronous, synchronous, and synchronized data. While the transmission of the asynchronous data is very simple, that of the synchronous or synchronized data is more complex because the synchronous and the synchronized data have time information for the presentation. Inaccurate transmission time without regarding the presentation time for the synchronous or synchronized data can cause a buffer overflow or delayed reception of a data in the receiver. Therefore, we propose a method to calculate the accurate transmission time of the synchronized data by using the MPEG-2 Program Clock Reference (PCR) and the Presentation Time Stamp (PTS) of the synchronized data. To verify the proposed method, we make an MPEG-2 Transport Stream (TS) by multiplexing the synchronized data with an A/V program based on the proposed method, and then analyze the multiplexed MPEG-2 TS. Also, the screen shots of the displayed synchronized data are presented in the receiver.

In this paper, we propose an advanced structure of the interface circuit, called a wrapper, for Globally Asynchronous Locally Synchronous (GALS) systems. The proposed wrapper is composed of a sender module and a receiver module. The sender module carries out data transfers in an efficient way by decoupling dependency between an external handshake protocol and an internal clock. The decoupling effect allows the external handshake protocol and the internal clock to be executed in a concurrent way and hence allows the wrapper to show better performance. We have designed our wrapper at the transistor level with 0.35-µm technology. When we compare our decoupled wrapper with two conventional wrappers based on pausible clocking scheme, our simulation results show that performance improvement is about 8-13% and 13-56%, respectively.

In this paper, we proposed the novel method for the recognition of English calling cards by using the contour tracking algorithm and the enhanced fuzzy RBF (Radial Basis Function) neural networks. The recognition of calling cards consists of the extraction phase of character areas and the recognition phase of extracted characters. In the extraction phase, first of all, noises are removed from the images of calling cards, and the feature areas including character strings are separated from the calling card images by using the horizontal smearing method and the 8-directional contour tracking method. And using the image projection method the feature areas are split into the areas of individual characters. We also proposed the enhanced fuzzy RBF neural network that organizes the middle layer effectively by using the enhanced fuzzy ART neural network adjusting the vigilance parameter dynamically according to the similarity between patterns. In the recognition phase, the proposed fuzzy neural network was applied to recognize individual characters. Our experiment result showed that the proposed recognition algorithm has higher success rate of recognition and faster learning time than the conventional RBF network based recognitions.

Applying the formerly proposed classification framework for first order line search optimization techniques we introduce novel superlinear first order line search methods. Novelty of the methods lies in the line search subproblem. The presented line search subproblem features automatic step length and momentum adjustments at every iteration of the algorithms realizable in a single step calculation. This keeps the computational complexity of the algorithms linear and does not harm the stability and convergence of the methods. The algorithms have none or linear memory requirements and are shown to be convergent and capable of reaching the superlinear convergence rates. They were practically applied to artificial neural network training and compared to the relevant training methods within the same class. The simulation results show satisfactory performance of the introduced algorithms over the standard and previously proposed methods.

This paper presents a compensating method based on Self-Organizing Map (SOM) for nonlinear distortion, which is caused by high-power amplifier (HPA) in 16-QAM-OFDM system. OFDM signals are sensitive to nonlinear distortions and different methods are studied to solve them. In the proposed scheme, the correction is done at the receiver by a SOM algorithm. Simulations are carried out considering an additive white Gaussian (AWG) transmission channel. Simulation results show that the SOM algorithm brings perceptible gains in a complete 16-QAM-OFDM system.

In 1960, the famous computer pioneer J.C.R. Licklider described a vision for human-computer interaction that he called "man-computer symbiosis. " Licklider predicted the development of computer software that would allow people "to think in interaction with a computer in the same way that you think with a colleague whose competence supplements your own. " More than 40 years later, one rarely encounters any computer application that comes close to capturing Licklider's notion of human-like communication and collaboration. We echo Licklider by arguing that true symbiotic interaction requires at least the following three elements: a complementary and effective division of labor between human and machine; an explicit representation in the computer of the user's abilities, intentions, and beliefs; and the utilization of nonverbal communication modalities. We illustrate this argument with various research prototypes currently under development at Mitsubishi Electric Research Laboratories (USA).

A post-wall waveguide-fed parallel plate slotted array is an attractive candidate for high efficiency and mass producible planar array antennas for millimeter wave applications. For the slot design of this large sized array, a periodic boundary wall model based on the assumption of infinite array size and a parallel waveguide is used. In fact, the aperture is large but still finite (10-40 wavelength) and the TEM-like wave is perturbed due to the narrow walls at the periphery of the aperture as well as the slot coupling; antenna efficiency is affected by the size and the aspect ratio of the aperture. All these observations imply the unique defects of oversized waveguide arrays. In this paper, the aperture efficiency of post-wall waveguide arrays is assessed as a function of size and aspect ratio of the aperture for the first time, both in theory and measurement. An effective field analysis for an electrically large oversized waveguide array, developed by the author, is utilized for determining the slot excitation coefficients and aperture illumination. It is predicted that the oversized waveguide array has a potential efficiency of 80-90% if the aperture is larger than 18 wavelength on a side and the gain is more than 30 dBi. A transversely wide aperture generally provides higher efficiency than a longitudinally long aperture, provided a perfectly uniform TEM wave would be launched from the feed waveguide.

A 1-V 2.4-GHz-band fully monolithic PLL synthesizer was fabricated in 0.2-µm CMOS/SOI process technology. It includes a voltage-controlled oscillator (VCO) and a 3-GHz fully differential dual-modulus prescaler on a chip. A low-off-leakage-current charge pump is used for open-loop FSK modulation. When the PLL is in the open loop mode, the frequency drift of the output is lower than 2.5 Hz/µsec. The output phase noise is -104 dBc/Hz at 1-MHz offset frequency. The power consumption of the PLL-IC core is 17 mW at 1-V supply voltage. This PLL synthesizer is suitable for a 1-V Bluetooth RF transceiver LSI.

A high-speed bipolar ECL comparator circuit with a latch is described. The spike noise generated by charging the base-to-emitter diffusion capacitor on the transition of differential transistors' switching in a sample-and-latch circuit is reduced by inserting the emitter degeneration resistors so that neither of them becomes completely cut off. The frequency bandwidth of a pre-amplifier is increased by using coupled inductors as differential loads. As a result, -3 dB frequency bandwidth of a pre-amplifier becomes 10 GHz, and 4 GS/s operation with 6-bit equivalent precision from a 3.3 V power supply is confirmed by the circuit simulation using device parameters from the 25 GHz silicon bipolar process.

In the last few years we have seen an explosion in the number of notebook computers and in the growth of the Internet. Mobile users expect to access the Internet's information resources and to communicate with other Internet users. The concept of Mobile IP is proposed to satisfy these demands. Using the base Mobile IP protocol, all datagrams destined for a mobile node are routed through that mobile node's home agent, which intercepts and tunnels each datagram to the mobile node's current location. This tunneling scheme creates a triangle routing problem, causing packets to travel through the home agent. In this paper, we propose that a Proxy Home Router (PHR) for routing performance improvement in a Mobile IP environment. One or more of Intermediate Systems (IS) on the route path between the correspondent node (CN) and the home agent (HA) are established as a PHR which then delivers packet instead of the home agent (HA). This PHR route optimization (PHR-RO) scheme has the following features. It is compatible with the base Mobile IP with existing Internet computers, and applications. Also, it is unnecessary for a CN to be modified in the proposed architecture. We also define Route Optimization messages in order to optimize route to a mobile node. Using these protocol extensions, a PHR may cache the binding information of a mobile node, and then tunnel their datagrams for the mobile node (MN) directly to the care-of address (CoA), bypassing the mobile node's home agent (HA). To analyze the performance of our PHR route optimization (PHR-RO) scheme, we propose a simulation model and show how to improve routing performance. Through this performance analysis, we conclude that the route optimization with a proxy home router (PHR) has better performance in terms of the end-to-end delay and TCP throughput.

This paper proposes a novel feature selection method for the fuzzy neural networks and presents an application example for 'personalized' facial expression recognition. The proposed method is shown to result in a superior performance than many existing approaches.

This paper addresses issues regarding to the development of teleconferencing support collaboration focusing on the realistic sensation domain. It argues that the gaze communications are the important mechanisms to enable visual channel and social presence in human-human communications. We propose a new aspect to establish multiple eye contacts and community awareness in multiparty videoconference (VC). The participants can aware of being recognized from any remote sites while they are talking with each other. Community awareness means the ability to aware of group communication in the videoconference. The participant can recognize of who is talking with whom and any communicative groups in a conference. An intelligent image arrangement through a unique position of camera is built and simulated. The systematic placement of images serves the gaze communications by utilizing the characteristic of gaze direction and image's position. The experimental results show that the proposed approach has the significant improvement in the interpersonal communication compared with the conventional VC system.

In this paper, a new method for displaying a surface deformation is proposed to provide sufficient realism in virtual environment. The approach selected in this paper is based on the fuzzy model and it is sufficient that only one additional rule be added to the fuzzy model to display a surface deformation. Furthermore, designers can easily determine which parameters should be used and how much they should be changed in order to alter shapes as required. The proposed method, thus, is a simple, but effective technique that can also be applied to real time operation and makes it possible to act on several surface points simultaneously. The results of the computer simulation are also given to demonstrate the validity of the proposed algorithm.

We compared two edge-blending methods for multi-projection displays, elliptic and rectangular blending, by simulating three common situations: (1) an inaccurately estimated calibration parameter, (2) a worn projector lamp, and (3) a shifted viewpoint. We used a two-level-of-detail display including a high-gain rear-projection screen in the simulation to demonstrate an extreme case. The comparisons showed how strongly inaccurate elements affect a composite besides affecting the appearance itself. A subjective assessment was also carried out to obtain the evaluations of actual users. The simulation results showed that in many cases elliptic blending is more effective than rectangular blending.