This paper proposes an optical access networks that guaranteed QoS in bidirections. Our scheme is the PON (Passive Optical Network) systems using OCDM (Optical Code Division Multiplexing) technology. For the bidirectional 100 Mbps guaranteed, we examined the simple decision circuit, code length (the number of chips), the number of simultaneously accesses and transmission distance. Furthermore, we reported the results that evaluated prototype of speed-down (4 Mbps, 16 chips) for the functional check of simple decision circuit.

A technique for the design of circular- and racetrack-shaped NRD guide ring resonators was developed based on the mode coupling theory. Besides the operating mode, a parasitic mode is generated at curved sections of the resonator as a result of the mode conversion. Resonance of the NRD guide ring resonator is derived by characteristic equations of the coupled modes and then employed in making the design diagrams, which are useful for determining the dimensions of the ring resonators. It is shown that the discrepancy between the experimental results and previous theory can be resolved by using the present theory. Low loss, small-sized ring resonators with curvature radii of less than 5.3 mm were fabricated at 60 GHz and a band rejection performance of more than 30 dB was observed. Moreover, a procedure for the design of the channel dropping filter was developed and a 2-pole filter, which has great advantages such as a low insertion loss of 1.2 dB and a compact size smaller than that of a golf ball, was successfully developed by using two racetrack-shaped ring resonators.

This paper examines the descriptive power and the limitations of a simple reinforcement learning model (REL), comparing the simulation results with the results of an economic experiment employing human subjects. Agent-based computational economics and experimental economics are becoming increasingly popular as tools for economists. A new variety of learning model using games with a unique equilibrium is proposed and examined in both of the fields mentioned above. However, little attention is given to games with multiple equilibria. We examine threshold public goods games with two types of equilibria, where each player in a five-person group simultaneously contributes the public goods from her private endowments. In the experiments, we observe two patterns of the subjects' behavior: the cooperative and non-cooperative patterns. Our simulation results show that the REL reproduces the cooperative pattern, but does not reproduce the non-cooperative pattern. However, the results suggest that the REL does reproduce the non-cooperative pattern in terms of the agents' internal states. That implies that deterministic strategies would be required to reproduce the non-cooperative pattern in the games. We show an example of the REL with deterministic strategies.

This paper proposes a method to integrate computer specifications retrieved from multiple Web sites, to extract characteristic-data of each computer based on integrated information, and to present products suitable for a user's request. The specifications written in HTML are converted into normal forms called table structure. The quantitative attributes such as speed, capacity and dimensions are extracted by comparing them with the mean or mode of all sample data, and the qualitative ones such as kind of processor and graphics chip are extracted using knowledge provided manually. The recommended products are dynamically determined from the extracted data by a user's request and relevance feedback. Experimental results show the effectiveness of our method.

In this paper, we propose a pipelined architecture for an equalizer based on the Multilevel Modified Constant Modulus Algorithm (MMCMA). We also provide the correction factor that mathematically converts the proposed pipelined adaptive equalizer into an equivalent non-pipelined conventional MMCMA based equalizer. The proposed method of pipelining uses modules with 6 filter coefficients, resulting in an overall latency of a single sampling period, along the main transmission line. The basic concept of the proposed architecture is to implement the Finite Impulse Response (FIR) filter and the algorithm portion of the adaptive equalizer, such that the critical path of the whole circuit has a maximum of three complex multipliers and three adders.

In this paper, we consider the problem of estimating the time-varying directions-of-arrival (DOAs) of coherent narrowband cyclostationary signals impinging on a uniform linear array (ULA). By exploiting the cyclostationarity of most communication signals, we investigate a new computationally efficient subspace-based direction estimation method without eigendecomposition and spatial smoothing (SS) processes. The proposed method uses the inherently temporal property of incident signals and a subarray scheme to decorrelate the signal coherency and to suppress the noise and interfering signals, while the null subspace is obtained from the resulting cyclic correlation matrix through a linear operation. Then an on-line implementation of this method is presented for tracking the DOAs of slowly moving coherent signals. The proposed algorithm is computationally simple and has a good tracking performance. The effectiveness of the proposed method is verified through numerical examples.

A new beamforming method based on simplex downhill optimaization process has been presented for the reverse link CDMA systems. The proposed system performs code-filtering at each antenna for each user. The new beamforming method gives lower computations and faster convergence properties than existing algorithms. The simulation results show that the proposed algorithm has a better BER performance in the case of the time-varing channel.

This paper studies the local Poisson property of aggregated IP traffic. First, it describes the scenario where IP traffic presents a Poisson-like characteristic within some limited range of time scales when packets from independent traffic streams are aggregated. Each of the independent traffic streams corresponds to a series of correlated IP packets such as those of a transport connection. Since the Poisson-like characteristic is observed only within some limited range of time scales, we call this characteristic the local Poisson property. The limited range of time scales of the local Poisson property can be estimated from a network configuration and characteristics of transport connections. Second, based on these observations, we seek the possibility to apply an ordinary Poisson process to evaluation of the packet loss probability in IP networks. The analytical investigation, where IP traffic is modeled by a superposition of independent branching Poisson processes that presents the local Poisson property, suggests that the packet loss probability can be estimated by a finite-buffer queue with a Poisson process when the buffer size is within a certain range. The investigation is verified by simulations. These findings expand the applicability of conventional Poisson-based approaches to IP network design issues.

In this paper, we present a technique to obtain an accurate closed-form spatial Green's function for a coplanar waveguide. The integration of the Sommerfeld integrals is performed on the real axis, and the path deformation is avoided in the sampling data. The results are in good agreement with the numerical integration over wide ranges of the signal frequency and the observation distance.

An adaptive backstepping and high order sliding modes control algorithm is proposed for output tracking of mobile robots. The controller can greatly reduce the chattering due to conventional sliding modes technique. The proposed algorithm has certain robustness with respect to the external random disturbances and good adaptability with respect to the parametric uncertainty. The effectiveness of the proposed control strategy is demonstrated by simulations studies.

This paper focuses on the investigation of RoF link noise influence in an ubiquitous antenna system, which is composed of multiple radio base stations (RBSs) deployed over the service area, central control station (CCS) and radio-on-fiber (RoF) link that connects RBSs to the CCS. The ubiquitous antenna system is capable of receiving multiple mobile terminals simultaneously operating at the same frequency channel by making effective use of joint detection. However, in the ubiquitous antenna system, since signals are transmitted from RBSs to CCS via the RoF link, the noise generated at the RoF link, such as relative intensity noise, inter modulation distortion, optical shot noise and thermal noise, may become dominant factors degrading the performance. The performance evaluations considering optical link noise is given by computer simulations. Computer simulation results show that more than 19 dB of RoF link Eb/N0 is required for achieving sufficient performance.

An attenuation measurement system, which employs a traceable inductive voltage divider (IVD) at 1 kHz as a reference standard and dual channel intermediate frequency (IF) substitution method, is developed as an attenuation standard in the frequency range of 5 GHz to 12 GHz. The basic properties of the system are experimentally investigated and the expanded standard uncertainty of the system is estimated to be 0.0018 dB for 20 dB and 0.026 dB for 80 dB attenuation.

The transmission quality in mobile wireless communication systems is affected by not only AWGN but also multi-path fading. Particularly, the Doppler frequency, the delay spread and the Rician factor have a great influence upon the quality over fading channels. This letter proposes the approximate equation for easily calculating the BER in DS-CDMA systems over multi-path fading channels. The validity of the approximate equation is confirmed from the fact that the BER calculated by the equation coincides with that by the computer simulation.

We report the investigation of major dispersion mechanisms such as self-heating, trapping, current collapse, and floating-body effects present in AlGaN/GaN HFETs. These effects are analyzed using DC/Pulsed IV, load-pull, low-frequency noise systems, and a cryogenic probe station. This study leads to a better understanding of the device physics, which is critical for accurate large-signal modeling and device optimization.

This paper addresses the routing and wavelength assignment (RWA) problem in a wavelength routed all optical network. One of the main issues is the assignment of the limited number of wavelengths over each physical fiber connection so that high aggregate capacity can be achieved. In a typical mesh topology, this problem has been shown to be NP-hard. In this paper, we propose a new heuristic based algorithm building upon one of the best known wavelength assignment algorithms proposed by Zhang and Acampora. The salient feature of the proposed algorithm is to consider the inherent multihop nature of the underlying mesh topology. We demonstrate that the proposed algorithm reduces the complexity by an order of magnitude, while at the same time achieving significantly lower blocking probability.

Recently, diverse multimedia applications with stringent multiple Quality of Service (QoS) requirements have been increasing. In particular, multicast communication has become more popular because of its availability and for efficient use of network resources. Most multicasts are point-to-multipoint, in which a source delivers data to multiple designated recipients, such as for video or audio distribution. In the near future, multipoint-to-multipoint communication services, including multimedia collaborations such as video conferencing and distant-learning, will be developed. However, when a conventional multicast routing algorithm is applied to a multipoint-to-multipoint communication service, it might result in excessive traffic concentration on some links. Therefore, we propose a new multipoint-to-multipoint routing method. It utilizes the Fallback+ algorithm to perform multicast routing for the purpose of satisfying multiple QoS requirements and alleviating traffic concentrations. Simulation experiments show that our method improves traffic load balance and achieves efficient use of network resources.

This paper defines a new kind of a mixture density model for modeling a quasi-stationary Gaussian process based on mel-cepstral representation. The conventional AR mixture density model can be applied to modeling a quasi-stationary Gaussian AR process. However, it cannot model spectral zeros. In contrast, the proposed model is based on a frequency-warped exponential (EX) model. Accordingly, it can represent spectral poles and zeros with equal weights, and, furthermore, the model spectrum has a high resolution at low frequencies. The parameter estimation algorithm for the proposed model was also derived based on an EM algorithm. Experimental results show that the proposed model has better performance than the AR mixture density model for modeling a frequency-warped EX process.

It is known that Viterbi decoding based on the code trellis and syndrome decoding based on the syndrome trellis (i.e., error trellis) are equivalent. In this paper, we show that Scarce State Transition (SST) Viterbi decoding of convolutional codes is equivalent to syndrome decoding. First, we derive fundamental relations between the hard-decision input to the main decoder and the encoded data for the main decoder. Then using these relations, we show that the code trellis module for the main decoder in an SST Viterbi decoder can be reduced to a syndrome trellis module. This fact shows that SST Viterbi decoding based on the code trellis is equivalent to syndrome decoding based on the syndrome trellis. We also calculate the SST Viterbi decoding metrics for general convolutional codes assuming an AWGN channel model. It is shown that the derived metrics are equal to those of conventional Viterbi decoding. This fact shows that SST Viterbi decoding is equivalent to conventional Viterbi decoding, and consequently to syndrome decoding.

The file sizes of on going flows are fairly disparate on the current network. In this letter, we propose an "age-based" packet discard scheme in the Traffic Conditioner (TC) of a gateway to improve the performance of file transmission. The on going flows will be grouped to three classes of priority according to their "age" as network congestion occurs and the simulation results show that the proposed model can work efficiently in most of the congestion conditions.

A problem of estimating biopotential sources in the brain based on EEG signals observed on the scalp is known as an important inverse problem of electrophysiology. Usually there is no closed-form solution for this problem and it requires iterative techniques such as the Levenberg-Marquardt algorithm. Considering the nonlinear properties of inverse problem, and signal to noise ratio inherent in EEG signals, a back propagation neural network has been recently proposed as a solution. In this paper, we investigated the properties of neural networks and its localization accuracy for single dipole source localization. Based on the results of extensive studies, we concluded the neural networks are highly feasible in single-source localization with a small number of electrodes (18 electrodes), also examined the usefulness of this method for clinical application with a case of epilepsy.