The next-generation IP-based mobile network must accommodate various kinds of wireless access technologies, including W-CDMA. Although the soft handover technique should be supported if W-CDMA is used, redundant paths will be created by the soft handover scheme employed by the 3rd generation mobile communication system. This paper proposes the Network Distributed Soft Handover (NDSHO) method, which achieves soft handover control in an IP network but without any redundant paths. NDSHO continuously optimizes all routing paths by relocating the data copy point dynamically during communication according to the movement of the mobile terminal. To achieve the proposed method, this paper introduces a copy point seamless relocation method and an optimal point selection method which takes advantage of OSPF. Furthermore, we show quantitatively that NDSHO makes more efficient use of system resources than the 3rd generation system.

Even in embedded processors, the accuracy in a branch prediction significantly affects the performance. In designing a branch predictor, in addition to accuracy, microarchitects should consider area, delay and power consumption. We propose two techniques to reduce the power consumption; these techniques do not requires any additional storage arrays, do not incur additional delay (except just one MUX delay) and never deteriorate accuracy. One is to look up two predictions at a time by increasing the width (decreasing the depth) of the PHT (Prediction History Table). The other is to reduce unnecessary accesses to the BTB (Branch Target Buffer) by accessing the PHT in advance. Analysis results with Samsung Memory Compiler show that the proposed techniques reduce the power consumption of the branch predictor by 15-52%.

The scattering problem by metallic gratings has become one of fundamental problems in electromagnetics. In this paper, a thin metallic grating placed in conical mounting is treated as a lossy dielectric grating expressed by complex permittivity and thickness. The solution of the metallic grating by using the matrix eigenvalue calculations is compared with that of the plane grating by using the resistive boundary condition and the spectral Galerkin procedure, and the availability of the resistive boundary condition for thin metallic gratings in conical mounting is investigated. In order to improve the convergence of the solutions of thin metallic gratings, the spatial harmonics of flux densities which are continuous function instead of electromagnetic fields are used.

With the explosive growth of the Internet system, demands for broadband communication networks have rapidly increased to provide high quality network services. For this purpose, the IEEE 802.6 MAC standard protocol defines the distributed-queue dual bus (DQDB) for metropolitan area networks (MANs). The isochronous channel reuse problem (ICRP) has been studied for efficient use of DQDB by finding proper channel assignments to incoming connection requests. In this paper, we first define the generalized isochronous channel reuse problem (GICRP) as a generalization of ICRP, to afford demands of simultaneously satisfying plural connection requests such as for multicast applications, where certain sets of connection requests must be assigned channels simultaneously. We prove the NP-completeness of its decision problem. Then, we propose a minimum dead space (MDS) algorithm as a heuristic approach to GICRP. The extensive simulation results show that with shorter computation time, our MDS algorithm can always find better channel assignments reducing the waiting time for packet transmissions than the best existing algorithm for conventional ICRP.

In this paper, we propose a robust adaptive algorithm for impulsive noise suppression. The perturbation of the input signal as well as the perturbation of the estimation error are restricted by M-estimation. The threshold used in M-estimation is obtained from the proposed adaptive variance estimation. Simulations show that the proposed algorithm is less vulnerable to the impulsive noise than the conventional algorithm.

In this paper, we study a work-conserving multicast scheduling with fanout splitting in a switch, which routes incoming packets asynchronously without fragmentation into cells. A new switch architecture is proposed, which distributes the input links to P variable length packet switching fabrics (VPS) with every G input links sharing GR inlets of the VPS. The system performance is analyzed by queueing analysis to express the maximum throughput and packet delay in terms of the system parameters and traffic characteristics. A practical switch design is also proposed to realize almost the same scheduling as the work-conserving one. We have surveyed how the fanout distribution affects the performance of the switch through Fanout Function, which is defined and studied to help the design of a multicast switch. We show how Fanout Function determines the maximum throughput and packet delay. Various fanout distributions are compared. The mixed fanout distribution exhibits better performance while the deterministic fanout can be used as a bound in the design of a multicast switch. We optimize R and P to attain 100% maximum throughput under limited switch complexity. When the mean fanout size is large, we can use less hardware to achieve the optimal performance by using our architecture. The proposed realization of this switch can be implemented easily due to its modular design. It is scalable because distributed output contention resolution and routing are used instead of a central arbitrator. Its performance is verified by simulation. The result matches the theoretical work-conserving scheduling very well.

Whereas the autocorrelation is frequently used for pitch estimation, the resultant estimates usually suffer from inaccuracy. Instead of upsampling, we can improve the accuracy of the estimates by applying polynomial interpolation to the autocorrelation directly. For that purpose, four kernels, which are interpolating quadratic, quadratic-B spline, cubic-B spline, and cubic convolution kernels respectively, have been compared. Experiments show that the cubic B spline kernel shows the best performance, a little inferior to the computationally intensive upsampling procedure. The quadratic B spline kernel shows also reasonable performance with the merit of the further reduced computational complexities compared with the cubic B spline kernel.

Digital watermarks on pictures must have the ability to survive various image processing operations while not causing degradation of picture quality. Random geometric distortion is one of the most difficult kinds of image processing for a watermark to survive, and this problem has become a central issue in watermarking research. Previous methods for dealing with random geometric distortion have been based on searches, special watermark patterns, learning, or additional data such as original pictures. Their use, however, is accompanied by large computational overhead or by operational inconvenience. This paper therefore proposes a method based on embedding watermark patterns in two of the three color planes constituting a color picture so that these two planes have a specific covariance. The detection of the embedded information is based on the covariance between these two planes. Random geometric distortion distorts all the constituent color planes of a picture in the same way and thus does not affect the covariance between any two. The covariance-based detection is therefore immune to the distortion. The paper clarifies that detection error would occur whenever the inherent covariance (the covariance in the original picture) overrides the covariance made by watermarking. The two constituent planes having the minimum inherent covariance are therefore selected and their inherent covariance is reduced by shifting one of them and using a noise-reduction preprocess. Experimental evaluations using StirMark confirmed that 64 bits embedded in 256256-pixel pictures can be correctly detected without using searches, special patterns, learning, or additional data.

This paper deals with an on-line identification method based on a radial basis function (RBF) network model for continuous-time nonlinear systems. The nonlinear term of the objective system is represented by the RBF network. In order to track the time-varying system parameters and nonlinear term, the recursive least-squares (RLS) method is combined in a bootstrap manner with the genetic algorithm (GA). The centers of the RBF are coded into binary bit strings and searched by the GA, while the system parameters of the linear terms and the weighting parameters of the RBF are updated by the RLS method. Numerical experiments are carried out to demonstrate the effectiveness of the proposed method.

In this paper, we propose the Synchronized Mobile Multicast (SMM) scheme for the real-time multimedia service to achieve three most important characteristics that the traditional Home Subscription (HS) and Remote Subscription (RS) mobile schemes cannot support. First, the SMM scheme supports the scalable one-to-many and many-to-many synchronized multimedia multicast on mobile IP networks to achieves seamless playback of continuous media streams even when both the mobile sender and receivers handoff simultaneously. Second, it analyzes the minimal buffer requirements of the mobile sender, the core router, the foreign agents and the mobile receivers in the multicast tree and formulates the initial playback delay within a handoff Guarantee Region (GR). Further, combined with the fine granularity scalability (FGS) encoding approach in the MPEG-4 standard, the SMM scheme achieves superior multimedia QoS guarantees and unlimited numbers of handoffs of the mobile sender and receivers only at the cost of degraded video quality for a short period after handoff with minimal extra bandwidth.

We propose a robust edge detection method based on independent component analysis (ICA). It is known that most of the basis functions extracted from natural images by ICA are sparse and similar to localized and oriented receptive fields, and in the proposed edge detection method, a target image is first transformed by ICA basis functions and then the edges are detected or reconstructed with sparse components only. Furthermore, by applying a shrinkage algorithm to filter out the components of noise in the ICA domain, we can readily obtain the sparse components of the original image, resulting in a kind of robust edge detection even for a noisy image with a very low SN ratio. The efficiency of the proposed method is demonstrated by experiments with some natural images.

In this letter, we analyze blocking probabilities for prioritized multi-classes in optical burst switching (OBS) networks. The blocking probability of each traffic class can be analytically evaluated by means of class aggregation and iteration method. The analytic results are validated with results garnered from simulation tests.

Three representative protocols are proposed to support mobility for IPv6 in IETF: Mobile IPv6, Hierarchical Mobile IPv6, and Fast Handovers for Mobile IPv6. Recently, IEEE 802.11 network has been widely deployed in public areas for mobile Internet services. In the near future, IPv6 mobility support over IEEE 802.11 network is expected to be a key function to actualize the pure IP-based mobile multimedia service. The IPv6 mobility support protocols have their characteristics in terms of signaling, handover latency, lost packets, and required buffer size. In this paper, we analyze the performance of the protocols over IEEE 802.11 network. We define a packet-level traffic model and a system and mobility model. Then, we construct a framework for the performance analysis. We also make cost functions to formalize each protocol's performance. Lastly, we investigate the effect of varying parameters used to show diverse numerical results.

A novel parallel acceleration technique is proposed based on intrinsic parallelism characteristics of shooting-and-bouncing ray launching (SBR) algorithm, which has been implemented using the MPI parallel library on common PC cluster instead of dedicated parallel machines. The results reveal that the new technique achieves very large speedup gains and could be the efficient and low-cost propagation prediction solution.

In this paper we consider an approximation method of a formal linearization which transform time-varying nonlinear systems into time-varying linear ones and its applications. This linearization is a kind of a coordinate transformation by introducing a linearizing function which consists of the Chebyshev polynomials. The nonlinear time-varying systems are approximately transformed into linear time-varying systems with respect to this linearizing functions using Chebyshev expansion to the state variable and Laguerre expansion to the time variable. As applications, nonlinear observer and filter are synthesized for time-varying nonlinear systems. Numerical experiments are included to demonstrate the validity of the linearization. The results show that the accuracy of the approximation by the linearization improves as the order of the Chebyshev and Laguerre polynomials increases.

Novel high-frequency asymptotic solutions for the scattered fields by a dielectric circular cylinder with a radius of curvature sufficiently larger than the wavelength are presented in this paper. We shall derive the modified UTD (uniform Geometrical Theory of Diffraction) solution, which is applicable in the transition regions near the geometrical boundaries produced by the incident ray on the dielectric cylinder from the tangential direction. Also derived are the uniform geometrical ray solutions applicable near the geometrical boundaries and near the caustics produced by the ray family reflected on the internal concave boundary of the dielectric cylinder. The validity and the utility of the uniform solutions are confirmed by comparing with the exact solution obtained from the eigenfuction expansion.

Point-to-point optical and millimeter wave communication has recently been of interest, especially in urban areas. Its benefits include simpler and easier installation compared with a land-based line. However, this technology suffers when adverse weather conditions are present, such as rain, fog and clouds, which induce scattering and absorption of the optical wave. The effects of scattering and absorption degrade the quality of the communication link resulting in increase of bit-error-rate. Therefore, there exists a need for accurate channel characterization in order to understand and mitigate the problem. In this paper, radiative transfer theory is employed to study the behavior of amplitude modulated signal propagating through a random medium. We show the effect of the medium to a modulated signal and relate the outcome on the quality of the communication link.

High frequency (HF) diffraction is known as local phenomena, and only parts of the scatterer contribute to the field such as the edge, corner and specular reflection point etc. Many HF diffraction techniques such as Geometrical Theory of Diffraction (GTD), Uniform Theory of Diffraction (UTD) and Physical Theory of Diffraction (PTD) utilize these assumptions explicitly. Physical Optics (PO), on the other hand, expresses the diffraction in terms of radiation integral or the sum total of contributions from all the illuminated parts of scatterers, while the PO currents are locally defined at the point of integration. This paper presents PO-based visualization of the scattering and diffraction phenomena and tries to provide the intuitive understanding of local property of HF diffraction as well as the relations between PO and the ray techniques such as GTD, UTD etc. A weighting named "eye function" is introduced in PO radiation integrals to take into account of local cancellation between rapidly oscillating contributions from adjacent currents; this extracts important areas of current distribution, whose location moves not only with the source but also with the observation point. PO visualization illustrates both local property of HF scattering and defects associated with ray techniques. Furthermore, careful examination of visualized image reminds us of the error factor in PO as applied for curved surfaces, named fictitious penetrating rays. They have been scarcely recognized if not for visualization, though they disturb the geometrical shadow behind the opaque scatterer and can be the leading error factors of PO in shadow regions. Finally, visualization is extended to slot antennas with finite ground planes by hybrid use of modified edge representation (MER) to assess the significance of edge diffraction.

This study proposes a 3 dB branch-line coupler using radial stubs to achieve reduced coupler size and simplified stub arrangement. As the electrical lengths of stubs used here are less than 90at center frequency, a method of comparing input impedances to obtain radial stubs that are equivalent to straight stubs is discussed. The frequency characteristics of the proposed coupler are derived by combining classical transmission line theory with the computed data of radial stub input impedances. The methods presented here increase possibilities for realizing reduced branch-line couplers by means of stub design. Experimental results agree well with theoretical results except for slight differences in the high frequency region.

In this paper, the magnetic field properties around household appliances are investigated with the single coil model and equivalent source model, which are used as main source models in the European standard EN50366 (CENELEC). The accuracy of the field properties is conducted for the coil model (defined in the EN50366), by comparing with the results of the equivalent source model, which allow the reproduction of the complicated inhomogeneous magnetic field around the appliance with full generality (i.e. supports three dimensional vector fields).