This paper proposes a 10 µm thick oxide layer structure, which can be used as a substrate for RF circuits. The structure has been fabricated by anodic reaction and complex oxidation, which is a combined process of low temperature thermal oxidation (500, for 1 hr at H2O/O2) and a rapid thermal oxidation (RTO) process (1050, for 1 min). The electrical characteristics of oxidized porous silicon layer (OPSL) were almost the same as those of standard thermal silicon dioxide. The leakage current through the OPSL of 10 µm was about 100-500 pA in the range of 0 V to 50 V. The average value of breakdown field was about 3.9 MV/cm. From the X-ray photo-electron spectroscopy (XPS) analysis, surface and internal oxide films of OPSL, prepared by complex process, were confirmed to be completely oxidized. Also the role of RTO was important for the densification of the porous silicon layer (PSL), oxidized at a lower temperature. For the RF test of Si substrate, with thick silicon dioxide layer, we have fabricated high performance passive devices such as coplanar waveguide (CPW) on OPSL substrate. The insertion loss of CPW on OPSL prepared by complex oxidation process was -0.39 dB at 4 GHz and similar to that of CPW on OPSL prepared at a temperature of 1050 (1 hr at H2O/O2). Also the return loss of CPW on OPSL prepared by complex oxidation process was -23 dB at 10 GHz which is similar to that of CPW on OPSL prepared by high temperature oxidation.

Files of 3D mesh models are often large and hence time-consuming to retrieve from a storage device or to download through the network. Most 3D viewing applications need to obtain the entire file of a 3D model in order to display the model, even when the user is interested only in a small part, or a low-resolution version, of the model. Therefore, coding that enables multiresolution and ROI (Region Of Interest) transmission of 3D models is desired. In this paper, we propose a coding algorithm of 3D models based on partitioning schemes. The algorithm actually partitions the 3D meshes into some small sub-meshes according to some geometric criteria (such as curvatures), and then codes each small sub-meshes separately to transmit it progressively to users on demand. The key idea of this paper lies in the mesh partitioning procedure prior to its LOD control, which enables good compression ratio of the mesh data as well as some other good capable properties through network transmission such as ROI coding, view-adaptive transmission, error resilient coding, etc.

In this paper, an efficient optimization algorithm for solving the inverse problem of a two-dimensional lossless homogeneous dielectric object is investigated. A lossless homogeneous dielectric cylinder of unknown permittivity scatters the incident wave in free space and the scattered fields are recorded. Based on the boundary condition and the incident field, a set of nonlinear surface integral equation is derived. The imaging problem is reformulated into optimization problem and the steady-state genetic algorithm is employed to reconstruct the shape and the dielectric constant of the object. Numerical results show that the permittivity of the cylinders can be successfully reconstructed even when the permittivity is fairly large. The effect of random noise on imaging reconstruction is also investigated.

In this paper, we propose a new predictive location management strategy that reduces the update cost while restricting the paging load optimized for mobiles roaming with traceable patterns. Enhanced with directional predictive capabilities offered by Kalman filtering, new update boundaries are assigned to better reflect the movement patterns of individual mobiles upon location registration. Thus, while complying with the required delay constraints, QoS measures such as throughput will not need to be sacrificed as a result of increasing update threshold. The contribution of this paper is two-fold: (1) to propose a distribution model that is capable of describing a wide range of movement patterns with varying correlation between traveling directions and (2) to show the capabilities (in terms of reliable performances) of the Kalman filter in predicting future movement patterns. Simulation results have successfully demonstrated the ability of the Kalman filter in assigning update boundaries capable of reflecting a mobile's roaming characteristics. The performance gains achieved mainly through a significant reduction in the number of updates indicate its potential for promoting better bandwidth conservation.

A tree 3-spanner T of a graph G is a spanning tree of G such that the distance between any two vertices in T is at most 3 times of their distance in G. Madanlal et al. have presented an O(n + m) time algorithm for finding a tree 3-spanner of a permutation graph. However, the complexity of their algorithm is not optimal, and their algorithm can not be easily parallelized. In this paper, we will propose an improved algorithm to solve the same problem in O(n) time. Moreover, our algorithm can be easily parallelized so that a tree 3-spanner of a permutation graph can be found in O(log n) time with processors on the EREW PRAM computational model.

In this paper, we introduce an analytical model of CDMA reverse link power control based on the asymptotic theory. The effect of the SIR threshold value on the transient behavior is addressed and the optimal value of the threshold to achieve the fast convergence without oscillation is derived. In addition, the usefulness of the asymptotic analysis is confirmed by simulations.

In the virtual home environment (VHE), which was proposed to offer global roaming and personal service environment portability, user's profiles and service logics are conveyed from home network to visited network to provide services at the visited network. Because user's profiles and service logics may contain confidential information, some procedures for mutual authentication among entities for offering confidence are needed. For these issues, we propose and analyze 3 party mutual authentication protocols adaptable to the VHE in 3G.

Various network resources, including wireless access services and multimedia appliances (device) are expected to be available in ubiquitous computing environments. Since resource availability can change when a user migrates from one place to another, functions to monitor the availability of resources in use and, if necessary, switch from obsolete resources to new ones are necessary for continuous service provision. This paper proposes adaptive terminal middleware called AMID that performs policy-based dynamic resource selection and host-based session management to ease network administrative tasks, and hide session failures and resource changes from applications and a user. AMID supports two kinds of mobility; session maintenance on vertical handoff and device handoff (service mobility). By AMID, a mobile host keeps entire handoff control and session state to eliminate the need for network-layer or intermediate-node mobility support, and mitigate responsibility of devices for session management. AMID realizes a Reliable Virtual Socket (RVS), on top of real sockets, which employs a seamless session handoff mechanism for resource changes, and a reliable session resume mechanism against unplanned disconnection of a wireless link. It achieves seamless session handoff through a proactive soft handoff method; to conceal setup and signaling latency, it initiates setup procedures with neighbor resources in advance of actual handoff and utilizes multiple wireless interfaces and devices redundantly. We implemented AMID and a follow-me audio application on top of it to evaluate the performance. Redirection of audio streams from built-in speakers to external ones, and handoff between 802.11b and Cellular are autonomously performed when a user migrates in the house. We confirmed that AMID achieved reliable session maintenance against wireless link failure, concealed latency of handoff management, and prevented packet loss during handoff.

As the capacity of a personal computer and workstation increases rapidly, many electromagnetic simulators solving antenna problems are widely used. In this paper, the IE3D, FIDELITY and HFSS electromagnetic simulators, which are commercial software products, are applied to the analysis of built-in antennas for handsets in the vicinity of the human body. The IE3D, FIDELITY and HFSS electromagnetic simulators are based on the methods of moment, FDTD (Finite Difference Time Domain) and FEM (Finite Element Method), respectively. Firstly, basic characteristics including the human body's effect of a popular built-in antenna for handset such as PIFA (Planar Inverted-F Antenna) are obtained by the IE3D, FIDELITY and HFSS electromagnetic simulators, and calculated results are compared with measured results. Secondly, on the basis of newly considered design concepts for a handset antenna, a folded loop antenna for handset, which we have proposed in order to reduce the influence of the human body, is taken as an example of a balance-fed antenna and is analyzed theoretically and experimentally including the influence of the human body. In a result, calculated results by these three kinds of electromagnetic simulators are in good agreement with measured results and it is confirmed that these simulators are very effective in analyzing the handset antenna in the vicinity of the human body.

We propose and demonstrate a directly modulated AM-VSB CATV system employing split-band and optical vestigial sideband (VSB) modulation techniques. Systems' performance can be improved by using optical VSB modulation and split-band techniques simultaneously. Our proposed directly modulated transmission system is simpler and more cost-effective than conventional externally modulated transmission system because of external modulator and complicated stimulated Brillouin scattering (SBS)-suppression method are not required.

The performance of a mobile ad hoc network (MANET) is related to the efficiency of the routing protocol in adapting to changes in the network topology and the link status. However, the use of many different mobility models without a unified quantitative "measure" of the mobility has made it very difficult to compare the results of independent performance studies of routing protocols. In this paper, a mobility measure for MANETs is proposed that is flexible and consistent. It is flexible because one can customize the definition of mobility using a remoteness function. It is consistent because it has a linear relationship with the rate at which links are established or broken for a wide range of network scenarios. This consistency is the strength of the proposed mobility measure because the mobility measure reliably represents the link change rate regardless of network scenarios.

This letter presents a lower bound and approximation for the coverage probability of the pilot channel that can be used for a CDMA downlink design. The approximation of a compound truncated Poisson distribution is used to obtain a closed form equation for the coverage probability of the pilot channel. Computer simulations show that our lower bound curve is truly less than the empirical curve, and our proposed approximation agrees well with the empirical result.

A special group of voice application services (VASs) are promising contents for wireless as well as wireline networks. Without a designated call admission policy, VAS calls are expected to suffer from relatively high probability of blocking since they normally require better signal quality than ordinary voice calls. In this letter, we consider a prioritized call admission design in order to reduce the blocking probability of VAS calls, which makes the users feel the newly-provided VAS in belief. The VAS calls are given a priority by reserving a number of channel-processing hardwares. With the reservation, the blocking probability of prioritized VAS calls can be evidently reduced. That of ordinary calls, however, is increasing instead. This letter provides a system model that counts the blocking probabilities of VAS and ordinary calls simultaneously, and numerically examines an adequate level of the prioritization for VAS calls.

The objective of this paper is to study the relationship between a visual stimulus and the amplitude and phase of the alpha wave as a first step to investigating a change in the background wave after a sensory stimulus and an evoked potential. We examined the effect of a single visual stimulus on the amplitude and phase of alpha waves using the complex demodulation method. The visual stimuli were generated by an LED mounted in goggles with the eyes-closed condition. The amplitude of the alpha wave decreased gradually after the stimulus, until it reached a minimum at around 300 ms after the stimulus. The alpha wave continued to increase, showing some rebound, and returning again to the pre-stimulus level. The phase variation after the stimulus tends to be considerably larger than that before the stimulus. Moreover, the average phase returned to the same slope as the pre-stimulus by 2550 ms after the stimulus. The visual stimulus has an effect on the alpha wave until about 2500 ms after the stimulus. The phase variation difference before and after stimulus is significant from 112 ms to 678 ms after the stimulus. This finding suggests there is a partially pararell time course between the change in VEPs plus ERP complex and the alpha wave.

This paper presents a novel digit-level algorithm for motion estimation (ME) and its hardware implementations. It uses the most-significant-digit-first (MSD-first) processing and on-line arithmetic ME components. A dedicated array architecture is also proposed for applications with high-throughput ME. Various fast search algorithms were presented in literatures to reduce the complexity but sacrifice the motion vector (MV) quality. Our MSD-first ME decomposes the summation of absolute differences (SAD) and comparison operations to digit level with MSD-plane first. These comparisons are interleaved into SADs to distinguish the MV as soon as possible. The algorithm precisely extracts the impossible candidates and removes their rest operations. It saves 47.4 % to 64.3 % of SAD computations in full search block matching (FSBM) ME. In the past, the high implementation cost of redundant number system prevented the practical use of on-line arithmetic. Besides, the redundant SAD removal results in irregular data flow in system-level integration. All these problems are solved by our novel architecture design. In this paper, we propose novel architecture designs to solve these problems. Besides, the architecture requires only one memory access per pixel to lower memory bandwidth by extensive data parallelism and a particular memory addressing while keeping the controller simple. A 4 4 array processor is implemented in 0.35 µm 1P4M CMOS cell library, with 2.84 ns cycle time and 1510 gates. It can support 83 M FSBM operations per second. After normalization, our implementation can support 2.67 times SAD operations per unit area (estimated in gate count) of the conventional two's complement ones. MSD-first ME can realize with other ME algorithms to improve the performance as well.

The performance enhancement technology for indoor-to-outdoor wireless communication systems is discussed in this study. In outdoor communication systems, transmitted signals may be severely degraded mainly by multipath fading effect of the channel and this problem can be overcome using conventional multiple antenna technology and array signal processing algorithms. But, since channel characteristics depend on both multipath fading and angle spread in indoor-to-outdoor communication systems, conventional algorithms which do not consider the effect caused by angle spread cannot give good results. In this letter, characteristics of indoor-to-outdoor channels are analyzed and a channel model suitable for this situation is proposed. And a new array antenna processing algorithm exploiting the concept of the mean steering vector is presented and the system performance is analyzed. It can be shown that the proposed algorithm outperforms conventional methods through computer simulations for the case in which signals sent from indoor transmitters arrive at outdoor receivers.

A high-speed 3-D camera has a future possibility of wide variety of application fields such as quick inspection of industrial components, observation of motion/destruction of a target object, and fast collision prevention. In this paper, a row-parallel position detector for a high-speed 3-D camera based on a light-section method is presented. In our row-parallel search method, the positions of activated pixels are quickly detected by a row-parallel search circuit in pixel and a row-parallel address acquisition of O(log N) cycles in N-pixel horizontal resolution. The architecture keeps high-speed position detection in high pixel resolution. We have designed and fabricated the prototype position sensor with a 12816 pixel array in 0.35 µm CMOS process. The measurement results show it achieves quick activated-position acquisition of 450 ns for "beyond-real-time" 3-D imaging and visual feedback. The high-speed position detection of the scanning sheet beam is demonstrated.

In this paper, we consider the problem of bearing estimation for spatially distributed sources in unknown spatially-correlated noise. Assumed that the noise covariance matrix is centro-Hermitian, a differential denoising scheme is developed. Combined it with the classic DSPE algorithm, a differential denoising estimator is formulated. Its modified version is also derived. Exactly, the differential processing is first imposed on the covariance matrix of array outputs. The resulting differential signal subspace (DSS) is then utilized to weight array outputs. The noise components orthogonal to DSS are eliminated. Based on eigenvalue decomposition of the covariance matrix of weighted array outputs, the DSPE null spectrum is constructed. The asymptotic performance of the proposed bearing estimator is evaluated in a closed form. Moreover, in order to improve the performance of bearing estimation in case of low signal-to-noise ratio, a modified differential denoising estimator is proposed. Simulation results show the effectiveness of the proposed estimators under the low SNR case. The impacts of angular spread and number of sensors are also investigated.

The transient phenomenon of electromagnetic waves caused by a time dependent resistive screen in a waveguide is treated. A boundary-value problem is formulated to describe the phenomena, in which the resistivity of the screen varies from one steady state to another in dependence on time. Application of Fourier analysis derives an integral equation, which is approximately solved by the method of least-squares. From the solution of the equation, the transient field is obtained by the inverse Fourier transform. By the use of the incomplete Lipschitz-Hankel integral for the computation of the field, numerical examples showing typical transient phenomenon are attached.

A high temperature performance of a W2N compound barrier in the model electrode configuration of W/W2N/poly-Si was examined. The stacked electrode was fairly stable upon annealing at 850 for 1 h. In this electrode configuration, the decomposition and outdiffusion of nitrogen, which were observed in the electrode with a WNx barrier incorporating nitrogen atoms at the interstitial sites in the bcc W lattice, were completely suppressed. We interpreted that the obtained excellent high temperature performance was attributed to the strong chemical interaction forming chemical bonds between nitrogen and W atoms in the W2N compound barrier.