Many types of adaptive algorithms based on the MMSE criterion for co-channel interference suppression in DS/CDMA systems have been studied in great detail. However, these algorithms have such a problem that the training speed is greatly dropped under the strong near-far problem. In this paper, we propose and analyze an adaptive filter based on the Maximum Signal to Interference and Noise Ratio (MSINR) criterion, called adaptive MSINR filter. This filter is basically equivalent to the adaptive filter based on the MMSE criterion. However, due to the structual difference, the convergence speed is greatly improved. Specifically, the de-spreading vector in this filter is so renewed as to maximize the Signal to Interference and Noise Ratio (SINR) by minimizing the de-spread interference and noise power under the condition that the de-spread desired signal power keeps constant. So the proposed filter uses the estimated interference and noise signal calculated by subtracting the estimated desired signal from the received signal. It is just the reason why the adaptive MSINR filter shows remarkable convergence speed. And to satisfy the constant signal power condition, the projection matrix onto the orthogonal complement of the desired signal space is used for the de-spreading vector. For the proposed filter, we analyze the convergence modes and also investigate the de-spread interfernce and noise power for calculating the theoretical SINR curve. Then, we conduct some computer simulations in order to show the difference between this filter and the conventional one in terms of the SINR convergence speed. As the result, we confirm that the adaptive filter based on the MSINR criterion achieves significant progress in terms of the SINR convergence speed.

In order to realize a future seamless high-speed road-vehicle communication system, we have proposed using code division multiplexing (CDM) radio transmission scheme by using cyclic shifted-and-extended (CSE) codes as spread codes. As the CSE codes are generated by cyclically shifting and extending a conventionally used code, the number of codes generated from a code is limited to the length of the shift interval and the tolerable period of delayed waves also depends on the length. In this paper, based on CSE codes, we propose a method to minimize the length of the shift interval and a cancellation technique with a simple calculation in order to eliminate the interference from delayed waves caused by the reduction of the length of shift interval. The concept and the BER performances in AWGN, two-paths, and multi-path fading environments are described in this paper. As a result, the maximum transmission rate of CSE-based-CDM transmission per one-code using the newly proposed transmission scheme is 3 times as large as that using conventional CSE codes and DQPSK-CDM transmission scheme.

This paper provides an overview on efficient algorithms for multicasting in optical networks supported by Wavelength Division Multiplexing (WDM) with limited wavelength conversion. We classify the multicast problems according to off-line and on-line in both reliable and unreliable networks. In each problem class, we present efficient algorithms for multicast and multiple multicast and show their performance. We also present efficient schemes for dynamic multicast group membership updating. We conclude the paper by showing possible extension of the presented algorithms for QoS provision.

This paper describes fully integrated active guard band filters for suppressing the substrate coupling noise and their noise suppression effect measured by test chip experiments. The noise cancellation circuit of the active guard band filters simply consists of an inverter and a source follower. The substrate noise suppression effect was measured by using a test chip fabricated in a 0.18 µm CMOS triple-well process for system-on-a-chip. The noise with the filter was less than 5% of that without the filter and the noise suppression effect was observed from 1 MHz to 200 MHz by the statistical measurement of the voltage comparator. The noise suppression effect was also observed for actual digital switching noise produced by digital inverters. Configuration of the active guard band filter was investigated by simulation and it is shown that high and uniform noise suppression effect is achieved by placing the guard bands in the L-shape around the target triple-well area on the p-substrate.

A number of results on the estimation of direction of arrival have been obtained based on the assumption that the signal sources are point sources. Recently, it has been shown that signal source localization can be accomplished more adequately with distributed source models in some real surroundings. In this paper, we consider modeling of three-dimensional distributed signal sources, in which a source location is represented by the center angles and degrees of dispersion. We address estimation of the elevation and azimuth angles of distributed sources based on the proposed distributed source modeling in the three-dimensional space using two linear arrays. Some examples are included to more explicitly show the estimation procedures under the model: numerical results obtained by a MUSIC-based method with two uniform linear arrays are discussed.

We propose and demonstrate a novel method to measure the polarization mode dispersion (PMD) of optical devices. The device under test (DUT) is installed in a fiber laser cavity which can operate at multiwavelength. PMD can be evaluated by the wavelength spacing of the multiwavelength laser output spectrum. In our method, the maximum extrema wavelength is easier to be identified than in the conventional fixed-analyzer (FA) method. We measure the PMD of polarization maintaining fibers (PMFs) and the ITU-T round robin KDD samples.

A receiver structure, which has linear computational complexity with the number of users, is proposed for decoding multiuser information data in a convolutionally coded asynchronous DS-CDMA system in multipath fading channels. The proposed receiver architecture consists of a multiuser likelihood calculator followed by a bank of soft-input soft-output (SISO) channel decoders. Information is fed back from SISO channel decoders to multiuser likelihood calculator, and the processing proceeds in an iterative fashion analogous to the decoding of turbo codes. A simplification to the above receiver structure is given too. Simulation results demonstrate that for both receiver structures at high signal-to-noise ratios (SNR) both multiple-access interference (MAI) and inter-symbol interference (ISI) are efficiently suppressed, and single-user performance is approached. Furthermore, the proposed iterative receiver is near-far resistant.

Fundamental EMI source that generates common-mode radiation from printed circuit boards (PCBs) is investigated here. It is done by modelling the ground lines of PCBs as imperfect ground. The radiation emission in the far zones from PCBs is obtained by regarding interconnects on PCBs as transmission lines and the far field emission is evaluated based on the current distribution of the lines. The finite size ground trace is defined as an imperfect ground, that can be viewed as an inductive reactance which, in turn, causes the ground return path to radiate as a wire antenna. For the accurate analysis of imperfect ground effect, we divide the equivalent circuit into N sections. In addition, based on transverse electromagnetic (TEM) assumption, we estimate the electromagnetic interference (EMI) of three typical PCB geometries, namely, coplanar strips, parallel-plate strips and microstrips. The quantitative value of induced current distribution along the ground return path depends on the physical size, geometry and length of ground traces. Measured data are presented to confirm the result of numerical analysis. A knowledge of EMI source mechanisms and their relationship to layout geometries is necessary to determine the essential features that must be taken into account to estimate emissions and provide direction for reducing EMI due to interconnects on PCBs.

This paper discusses a design methodology suitable for the development of software defined radio platforms. A flexible digital receiver was designed and implemented using a multi-port direct converter and an FPGA-based platform. The design starts with a hardware-oriented top-level system model. The model is built based on basic signal processing blocks connected together in a graphical tool. Carrier symbol timing recovery is implemented in the discrete-time (digital) domain with an interpolator-based synchronizer. Carrier phase and frequency are recovered using a feedback synchronization algorithm (a second-order type-II digital PLL). Experimental results of the platform and its simulation results demonstrate the effectiveness of the proposed design methodology.

We investigate dispersion compensation using dispersion-compensating fibers (DCFs) for ultrashort light pulse code division multiple access (CDMA) communication systems in a multi-user environment. We employ fiber link that consists of a standard single-mode fiber (SMF) connected with two different types of DCFs. Fiber dispersion can be effectively decreased by adjusting the length ratios of DCFs to SMF appropriately. Some criteria for dispersion compensation are proposed and their performances are compared. We theoretically derive a bit error rate (BER) of ultrashort light pulse CDMA systems including the effects of the dispersion and multiple access interference (MAI). Moreover, we reveal the mutual relations among BER performance, fiber dispersion, MAI, the number of chips, a bandwidth of a signal, and a transmission distance for the first time. As a result, we show that our compensation strategy improves system performance drastically.

A broadband RF front-end having a direct conversion architecture has been developed. The RF front-end consists of two broadband quadrature mixers, a multi-band local oscillator, and a broadband low-noise variable gain amplifier (LNVGA). The mixer achieves broadband characteristics through the incorporation of an in-phase power divider and a 45-degree power divider. The in-phase power divider achieves broadband characteristics through the addition of a compensation capacitor. The 45-degree power divider achieves broadband phase characteristics through the addition of a compensation capacitor and a compensation resistor. The local oscillator, which is composed of two VCOs, two frequency dividers, and four switches, can cover three systems including one FDD system. The LNVGA achieves its broadband characteristics without the use of reactance elements, such as inductors or capacitors. In a trial demonstration, when the RF frequency was between 900 MHz and 2.5 GHz, the mixer for a demodulator experimentally demonstrated an amplitude balance of less than 1.6 dB and a quadrature phase error of less than 3 degrees. When the RF frequency was between 900 MHz and 2.5 GHz, the mixer for a modulator demonstrated an image ratio of less than -30 dBc. The local oscillator demonstrated multi-band characteristics, which are able to cover the target frequencies for three systems (PDC, PHS, 2.4 GHz WLAN). From 900 MHz to 2.5 GHz, the amplifier shows a noise figure of less than 2.1 dB and a gain of 28 1.6 dB.

Optical near-field distributions of planar dielectric and metallic objects placed on a large dielectric substrate plate have been calculated by the volume integral equation using an iterative method called generalized minimal residual method with the fast Fourier transform technique. The basic characteristics of the near-field have been investigated in detail for large and small objects, dielectric and metallic objects and incident p-polarized and s-polarized evanescent fields.

We apply newly developed rigorous modal transmission-line theory (MTLT) to evaluate optimal design conditions on optical power coupling in grating-assisted directional couplers (GADCs) with two or three guiding channels. By defining a power distribution ratio (PDR) and coupling efficiency (CE) amenable to the rigorous analytical solutions of MTLT, we explicitly analyze the power coupling characteristics of TE modes propagating in GADCs. The numerical results reveal that the incident power is optimally coupled into the desired guiding channel if the powers of rigorous modes excited at the input boundary of grating-assisted coupler are equally partitioned.

This paper proposes a novel method to correct numerical phase velocity errors in FDTD meshes with nonuniform step size. It enables the complete compensation of the phase velocity errors introduced by the mesh grading for one frequency and one arbitrary direction of propagation independently of the mesh grading. This permits the usage of the Total-Field-Scattered-Field formulation in connection with electrically large nonuniform FDTD meshes and allows a general reduction of the grid dispersion errors. The capabilities of the proposed method are demonstrated with the help of two examples: (1) the fields in a dielectric sphere illuminated by a plane wave are calculated and (2) a patch antenna simulation demonstrates that the uncertainty in determining its resonance frequency can be reduced by about 50%.

In this letter, we address geometry coding of 3-D mesh models. Using a joint prediction, the encoder predicts vertex positions in the layer traversal order. After we apply the joint prediction algorithm to eliminate redundancy among vertex positions using both position and angle values of neighboring triangles, we encode those prediction errors using a uniform quantizer and an entropy coder. The proposed scheme demonstrates improved coding efficiency for various VRML test data.

This paper considers a reconfiguration problem on a processor array model based on single-and-half-track switches, which is proposed for a fault tolerance technique at the fabrication time. The focus of this paper is to achieve the optimal reconfigurability, which means that whenever there exists a solution for successful reconfiguration, the designed method can find the solution. The paper consists of two parts. In the first part, we show two essential constraints that have been assumed in most of the previous studies, and make four reconfiguration classes that differ in the assumed essential constraints. Then, we present some inclusion relations among the four reconfiguration classes. As a result, it becomes clear that the most restrictive class including most of the previous methods never achieves the truly optimal reconfigurability. In the second part, we present a reconfiguration method based on sequential routing (RMSR). Although the worst-case time complexity of the RMSR is exponential in the number of processing elements, the reconfigurability of the RMSR is optimal within the most restrictive reconfiguration class. The effectiveness of the RMSR is shown by a computer simulation.

We clarify the effectiveness of receiver-side compensation in offsetting fiber Bragg grating (FBG) dispersion induced-electrical signal-to-noise ratio (SNR) degradation in a 10 Gb/s 8-channel wavelength-division multiplexing (WDM) 6,400 km transmission system. The receiver-side compensation greatly improves the SNR degradation. The allowable accumulated FBG dispersion is -400 1000ps/nm for the worst arrangement, a single FBG at the transmitter, which is about half the accumulated fiber dispersion permissible with receiver-side compensation.

In this paper, we propose and describe a new synchronizer for the FFT timing applicable to multi-carrier spread-spectrum (MC-SS) communication systems. The performance of the synchronizer is evaluated in terms of false- and miss-detection probabilities in the presence of additive white Gaussian noise (AWGN) and Rayleigh fading.

In an orthogonal frequency division multiplexing (OFDM) system, the bit error performance is degraded in the presence of multiple propagation paths whose excess delays are longer than the Guard Interval (GI), because the orthogonality between subcarriers cannot be maintained. In this paper, we propose a new OFDM demodulation method with a variable-length effective symbol and a multi-stage inter-carrier interference (ICI) canceller, in order to improve the bit error performance in the presence of multipaths whose excess delays are longer than the GI. The influence of the inter-symbol interference (ISI) is eliminated by the variable-length effective symbol, and then the ICI component is reduced by the multi-stage ICI canceller. The principle of the proposed method is explained, and the performance of the proposed method is then evaluated by computer simulation. The results show that the proposed method improves the system availability under more various multipath fading environments without changing the system parameters.

A shared binary decision diagram (SBDD) represents a multiple-output function, where nodes are shared among BDDs representing the various outputs. A partitioned SBDD consists of two or more SBDDs that share nodes. The separate SBDDs are optimized independently, often resulting in a reduction in the number of nodes over a single SBDD. We show a method for partitioning a single SBDD into two parts that reduces the node count. Among the benchmark functions tested, a node reduction of up to 23% is realized.