Topology of a network greatly affects the network performance. Depending on the purpose of a network, a specific topology may perform much better than any other topologies. Since the ad hoc networks are formed for a specific purpose, determining, and constructing the network topology based on the application requirements will enhance system performance. This paper proposes Bluetooth scatternet forming protocol in which the network topology is determined by three parameters. The parameters affecting the topology are the number of maximum slaves in a piconet, the number of maximum piconets that a gateway Bluetooth device can service, and the number of loops needed in the formed scatternet. These parameters can be read from a script file prior to the network formation. This process of reading the important parameters from the file would give users freedom in determining the network topology. The proposed protocol also includes a role negotiation process to accommodate different capabilities of the participating devices. The negotiation process of the protocol allows the resource-limited nodes to participate in the network. Different types of scatternet topologies like star, mesh, ring and line can be formed by specifying the parameters. This paper also discusses theoretical information necessary for calculating network topologies in detail. The protocol is verified with help of simulations, and implementations using commercially available Bluetooth devices. The detailed results are also presented in this paper.

This paper presents a modification of kernel-based Fisher discriminant analysis (FDA) to design one-class classifier for face detection. In face detection, it is reasonable to assume "face" images to cluster in certain way, but "non face" images usually do not cluster since different kinds of images are included. It is difficult to model "non face" images as a single distribution in the discriminant space constructed by the usual two-class FDA. Also the dimension of the discriminant space constructed by the usual two-class FDA is bounded by 1. This means that we can not obtain higher dimensional discriminant space. To overcome these drawbacks of the usual two-class FDA, the discriminant criterion of FDA is modified such that the trace of covariance matrix of "face" class is minimized and the sum of squared errors between the average vector of "face" class and feature vectors of "non face" images are maximized. By this modification a higher dimensional discriminant space can be obtained. Experiments are conducted on "face" and "non face" classification using face images gathered from the available face databases and many face images on the Web. The results show that the proposed method can outperform the support vector machine (SVM). A close relationship between the proposed kernel-based FDA and kernel-based Principal Component Analysis (PCA) is also discussed.

Current centralized restoration schemes are unsuitable for the increase of scale and complexity of networks. A novel distributed network partition scheme is proposed in this paper. In this scheme, a large-scale network can be partitioned into some wheellike sub-networks with nuclear nodes. In wheellike sub-networks, ring links and spoke links could provide reciprocal safeguard. Based on such structure, different distributed restoration schemes can be combined for failure restoration. The proposed partition approach has been implemented through computer simulation, and it was tested on practical national-scale optical networks. The simulation result shows that this scheme is practicable and effectual.

In this letter, we show that some stream authentication schemes using hash chaining are highly vulnerable to denial of service (DoS) attacks. An adversary can disrupt all receivers of group by making use of modifying a few packets in those schemes.

We investigate strategies to improve the utterance verification performance using a 2-class pattern classification approach, including: utilizing N-best candidate scores, modifying segmentation boundaries, applying background and out-of-vocabulary filler models, incorporating contexts, and minimizing verification errors via discriminative training. A connected-digit database recorded in a noisy, moving car with a hands-free microphone mounted on the sun-visor is used to evaluate the verification performance. The equal error rate (EER) of word verification is employed as the sole performance measure. All factors and their effects on the verification performance are presented in detail. The EER is reduced from 29%, using the standard likelihood ratio test, down to 21.4%, when all features are properly integrated.

Limited energy is a big challenge for large scale wireless sensor networks (WSN). Previous research works show that modulation scaling is an efficient technique to reduce energy consumption. However, the impacts of using modulation scaling on packet delivery latency and loss are not considered, which may have adverse effects on the application qualities. In this paper, we study this problem and propose control schemes to minimize energy consumption while ensuring application qualities. We first analyze the relationships of modulation scaling and energy consumption, end-to-end delivery latency and packet loss ratio. With the analytical model, we develop a centralized control scheme to adaptively adjust the modulation levels, in order to minimize energy consumption and ensure the application qualities. To improve the scalability of the centralized control scheme, we also propose a distributed control scheme. In this scheme, the sink will send the differences between the required and measured application qualities to the sensors. The sensors will update their modulation levels with the local information and feedback from the sink. Experimental results show the effectiveness of energy saving and QoS guarantee of the control schemes. The control schemes can adapt efficiently to the time-varying requirements on application qualities.

This paper presents the analysis of the stopping maneuver of the human driver by using a new three-dimensional driving simulator that uses CAVE, which provides stereoscopic immersive vision. First of all, the difference in the driving behavior between 3D and 2D virtual environments is investigated. Secondly, a GMDH is applied to the measured data in order to build a mathematical model of driving behavior. From the obtained model, it is found that the acceleration information has less importance in stopping maneuver under the 2D and 3D environments.

In this report, we propose a tracking algorithm of speaker direction using microphones located at vertices of an equilateral triangle. The method realizes tracking by minimizing a performance index that consists of the cross spectra at three different microphone pairs in the triangular array. We adopt the steepest descent method to minimize it, and for guaranteeing global convergence to the correct direction with high accuracy, we alter the performance index during the adaptation depending on the convergence state. Through some computer simulation and experiments in a real acoustic environment, we show the effectiveness of the proposed method.

This paper presents a novel decoding algorithm for turbo codes, in which the likelihood values for redundant parts are updated in order for those values to become more reliable. A criterion for updating the redundant likelihood values is proposed, which is based on the comparisons of the channel values with the re-generated values by the soft-input and soft-output encoders. It is shown that the proposed method can improve the error correcting capabilities, i.e., the improvement of BER/BLER performance and the achievable BER limit.

In this paper, we examine oscillatory modes generated by the Hopf bifurcations of equilibrium points except for the origin in a system of coupled four oscillators. (The bifurcation analyses of the origin for many coupled oscillators were already done.) The Hopf bifurcations of the equilibrium points with strong symmetrical property and the generated oscillatory modes are classified. We observe four-phase, in-phase and a pair of anti-phase synchronized states. Even in a system of four coupled oscillators, we discover the existence of a stable three-phase oscillation. By the numerical bifurcation analysis of generated periodic oscillations we find out successive period-doubling bifurcations as the route to chaos and show some of them are symmetry-breaking bifurcations. As a result of the symmetry-breaking period-doubling bifurcations, a periodic solution with complete synchronization becomes a chaotic solution with phase synchronization.

This paper discusses performance prediction of clock generation PLLs using a ring oscillator based VCO (RingVCO) and an LC oscillator based VCO (LCVCO). For clock generation, we generally design PLLs using RingVCOs because of their superiority in tunable frequency range, chip area and power consumption, in spite of their poor noise characteristics. In the future, it is predicted that operating frequency will rapidly increase and supply voltage will dramatically decrease. Besides, rigid noise performances will be required. In this condition, it is not clear neither how performances of both PLLs will change nor the performance differences between both PLLs will change. This paper predicts and compares future performances of PLLs using a RingVCO and an LCVCO with a qualitative evaluation by an analytical approach and with design experiments based on predicted process parameters. Our discussion reveals that the relative performance difference between both PLLs will be unchanged. As technology advances, power dissipation and chip area of both PLLs favorably decrease, while, noise characteristics of both PLLs degrade, which indicates low noise PLL circuit design will be more important.

The rate-distortion optimization (RDO) method is an informative technology that improves the coding efficiency, but increases the computational complexity, of the H.264 encoder. In this letter, a fast Macroblock mode determination algorithm is proposed to reduce the computational complexity of the H.264 encoder. The proposed method reduces the encoder complexity by 55%, while maintaining the same level of coding efficiency.

This study was designed to evaluate localized muscular fatigue induced during mouse operation in a VDT task. Ten male undergraduates from 19 to 23 years old participated in the experiment. The subject performed a pointing task with a PC mouse for about 4 hours. The EMG measurements and psychological rating of fatigue were conducted before the experimental task and after each 30-minutes block during the experimental task. The changes in the Mean Power Frequency (MPF) and Percentage Maximum Voluntary Contraction (%MVC)-shift for the constant cumulative probability in the Amplitude Probability Distribution Function (APDF) with time were explored. The correspondence between the index (MPF or APDF) and the subjective rating of localized muscular fatigue was also examined. The performance was nearly constant across all blocks. The psychological rating of fatigue tended to increase with time. The MPF tended to increase with time, although the main effect of block (time) was not statistically significant. The %MVC-shift tended to increase with time. The correspondence with the perceived sensation of localized muscular fatigue was higher when using the %MVC-shift than when using the MPF. Based on the results, the effectiveness of the indexes used for evaluating localized muscular fatigue was discussed. The %MVC-shift obtained from the APDF was found to be a sensitive index of localized muscular fatigue and corresponded well with the subjective rating of localized muscular fatigue.

This paper proposes an OFDM based adaptive modulation scheme employing variable coding rate (VCR OFDM AMS), which selects optimum modulation and coding scheme (MCS) realized by combination of several modulation schemes and coding rates. The OFDM AMS with multilevel transmit power control (OFDM AMS/MTPC) can realize high data rate transmission in the dynamic parameter controlled-orthogonal frequency and time division multiple access (DPC-OF/TDMA). The employment of OFDM AMS/MTPC, however, makes transceiver design rather complex. To solve this problem, we propose to improve throughput performances of the OFDM AMS without employment of the MTPC. The simple OFDM AMS, however, does not fully utilize transmit power for throughput improvement because there is surplus transmit power which corresponds to power margin over required signal to interference plus noise power ratio (SINR). Thus, in order to improve transmit power efficiency for throughput increase, we reduce the required SINR gaps between adjacent MCSs by introducing many coding rates. Furthermore, this paper presents an effective bit loading algorithm when multiple coding rates as well as modulation schemes are used. Computer simulation confirms that the proposed VCR OFDM AMS gives sufficient throughput performances as an alternative to the OFDM AMS/MTPC.

An intermediate frequency (IF) variable gain amplifier (VGA) with exponential gain control for a radio receiver is fabricated in 0.25-µm CMOS technology. The techniques to improve the bandwidth and to reduce temperature dependence of gain are described. The complete VGA is composed of two stages of linearized transconductance VGA and three stages of fixed gain amplifier (FGA). The complete VGA provides a continuous 10 dB to 76.5 dB gain control range, an IIP3 of -11.5 dBm and an NF of 15 dB at 40 MHz.

This article describes a large bandwidth and low distortion line driver in a 0.35-µm CMOS process. The line driver drives a 75 Ω resistive load. Its power consumption is 140 mW from a 3.3 V supply. It has a relatively high -3 dB bandwidth (260 MHz) with good phase margin of about 70 degrees. It shows very low THD (-74.5 dB) when drives the load with a 3.3 V peak to peak sine wave at 10 MHz. This architecture reduces the distortion by locating the input differential pair inside the feedback loop and eliminating the distortion of the feedback transistors, which is dominant source of distortion at high frequencies. Thus, it improves the linearity of the output voltage in comparison with previous designs.

This paper presents a novel wide tuning range CMOS Voltage Controlled Oscillator (VCO). VCO uses an on-chip variable inductor as an additional variable element to extend the tuning range of VCO. The fabricated variable inductor achieves the variable range of 35%. The VCO was fabricated using 0.35 µm standard CMOS process, and can be tuned continuously from 2.13 GHz to 3.28 GHz (tuning range of 38%) without degradation of phase noise. Wide tunable LC-VCO using a variable inductor is one of the key circuits for reconfigurable RF circuit.

The multi-channel Hybrid Fiber Coaxial (HFC) network is essentially a shared medium with multi-channels. Its operation requires the use of a scheduling algorithm to manage the data transmission within each channel. The Data-Over-Cable Service Interface Specification (DOCSIS) protocol is an important standard for HFC networks. Since this protocol does not explicitly specify the scheduling algorithm to be used, many alternative algorithms have been proposed. However, none of these algorithms are applicable to the scheduling of non-Unsolicited Grant Service (UGS) data in multi-channel HFC networks. Accordingly, the present study develops a multi-channel scheduling algorithm which optimizes the scheduling delay time of each transmitted non-UGS request. This algorithm manages the amount of data transmission in each upstream channel according to the overall network load and the bandwidth available in each channel. This study constructs a mathematical model of the algorithm and then uses this model as the basis for a series of simulations in which the performance of the scheduling algorithm is evaluated.

Integrated 900-MHz ISM band transceiver LSI for analog cordless telephone has been realized by cost-effective process technology with sufficient performance. This LSI consisted of fully integrated transceiver, from RF-LNA to audio amplifier for RX chain, from microphone's amplifier to RF-PA for TX chain, and integrated RX- and TX-LO consisting of PLLs and VCOs. In view of narrow signal bandwidth with analog modulation, extremely low phase noise at low offset frequency from carrier was required for integrated VCO. Also, in view of fully duplex operations, signal isolation between TX and RX was required. Despite such a high integration and high performance, chip cost had to be minimized for low-cost applications. The 12-dB SINAD RX sensitivity was -111.2 dBm, the output power of TX was +3 dBm, and the phase noise of integrated VCO was -77 dBc/Hz at 3 kHz offset away from carrier. The current consumption at fully duplex operation was 76 mA at 3.6 V power supply. The chip was realized by 0.8 µm standard silicon BiCMOS process.

In this letter, we provide a solution to the stabilization problem of a class of Lipschitz nonlinear systems by output feedback. Via the newly proposed nonlinearity characterization function (NCF) concept, we propose an effective method in designing an output feedback controller. Under the suggested sufficient condition which is derived by using the NCF, the proposed control scheme achieves the global exponential stabilization.