This letter presents a method for reducing power dissipation in a protocol converter. The communication protocol of a VLSI chip hierarchically consists of several sub-protocols and only one of them can be actively working at any given time. In general, protocol converters are implemented by dual protocols of the initially given protocols which are to be interfaced. If the duals of those sub-protocols are implemented in separate modules, we can separate active modules and inactive modules on the fly since only one of the modules can be active at a time. The active/inactive state of a module can be monitored by the control signals that represent the execution of the protocol corresponding to the module. Power reduction can be achieved by dynamically suppressing the clock supply to inactive modules. To trade-off the power reduction rate against the area overhead, the module granularity must be properly chosen. For this purpose, we implement the duals of the atomic protocols in the same module if their state graphs share states except the initial state. Our experimental results show that this method provides significant savings in power consumption of between 18.4% and 92.1% with a 5.3% area overhead.

Currently, the most popular model in data compression theory is that of stationary ergodic sources. But there do exist sequences each of which is not emitted from any stationary ergodic source but can be compressed sufficiently by a certain algorithm. We estimate the size of the set of such sequences in terms of Hausdorff dimension.

This paper investigates the improvement of the radiation pattern design of transmitting array antenna beamforming and transmission power control (TPC) for forward link of DS-CDMA/FDD system. Optimum transmission beamforming and TPC can be derived from the information of the propagation channel for the forward link, in terms of outage probability minimization. It is assumed that the channel is static and then all mobile stations (MS's) report channel characteristics measured in the forward link to a base station (BS) that can control signal to interference plus noise ratios (SINR's) received by individual MS's using that measured information. Then, for the multi-user environment of a single cell, goal programming (GP) is applied to derive an optimum weight vector of the transmitting array antenna and optimum TPC such that outage probability can be minimized.

We examined the creep properties and hazard rates of plastic ferrules to ensure the long-term reliablity of optical fiber connections. The endface deformation ΔL had to be smaller than 3 µm to keep the insertion-loss and return-loss fluctuation to acceptable levels in the worst case of random concatenation of similarly deformed plastic ferrules. From the fluctuation data, we estimated the time-to-failure tf at which the ΔL value became 3 µm. We estimated the acceleration parameters, median lifetimes ξ, and hazard rates λ by using tf values based on Weibull statistics. The ξ values decreased rapidly with increasing temperature and relative humidity. We found we could expect small λ values of < 0.1 FIT (FIT=10-9/hour) and of 1 FIT for 20 years in a normal atmosphere (25C/50%RH) and in a more severe case of 25C/90%RH, respectively.

Precise and quick multi-beam forming including null control will be one of the key technologies for the future satellite communication systems utilizing SDMA (Space Division Multiple Access) and DOA (Direction of Arrival) estimation. In order to realize the precise multi-beam forming, calibration procedure is indispensable since there are several unavoidable factors that degrade the multi-beam patterns of the array. Particularly amplitude and phase imbalance between RF circuits needs to be calibrated frequently and quickly when the array system exists in changeable environment since the imbalance easily occurs due to thermal characteristics of each RF circuit. This paper proposes a simple and high-speed remote calibration scheme compensating for amplitude and phase imbalance among RF circuits of a transmitting adaptive array antenna onboard satellite. This calibration is conducted at a remote station such as a gateway station on the ground in the satellite communication system, by utilizing the received signal including the temporally multiplexed orthogonal codes transmitted from the array antenna onboard satellite. Since the calibration factors for all the antenna elements can be simultaneously obtained by the parallel digital signal processing, calibration time can be drastically reduced. The accuracy of this calibration is estimated by simulation. Simulation results show that the amplitude imbalance among RF circuits can be suppressed within the range from -0.5 dB to +0.25 dB for the initial imbalance ranging from -2 dB to +3.5 dB, phase imbalance can be suppressed within the range of -3 deg. to +3 deg. for the initial imbalance ranging from -120 or +180 deg. by this method. The amplitude and phase deviations among the elements can be suppressed within 0.36 dB and 2.5 degrees, respectively, in 80% of probability. Simulation results also show that this calibration method is valid under the relatively bad carrier-to-noise conditions such as -10 dB at the receiver. Good improvement of the multi-beam patterns by this calibration is shown under the low carrier-to-noise ratio condition.

Using moment generating function (MGF) of generalized selection combining (GSC) output signal-to-noise ratio (SNR), we derive closed-form expressions for average combined SNR at the output of GSC, which optimally combines the N largest out of L available diversity signals, over Nakagami-m fading channels for N = 2, 3 and L = 4. The Nakagami-m fading statistics on each diversity branch are assumed to be independent and identically distributed (i.i.d.). The average combined SNRs at the outputs of GSC receivers are also compared with the average combined SNRs at the outputs of conventional maximal ratio combining (MRC) and selection combining (SC).

In this paper, we report on our recent work in designing and developing an optical waveguide and optical integrated circuit for optical BFN in adaptive multibeam array antenna. We introduce a new integrated Ti:LiNbO3 waveguide and prove that it is able to yield large birefringence and birefringence dispersion. We present a new technique using a microwave-modulated optical wave to measure the birefringence in integrated Ti:LiNbO3 optical waveguides. The measuring results show that the new waveguide has a birefringence of 0.08 and birefringence dispersion of 0.05 µm-1 at optical wavelength of 1.55 µm. When the new Ti:LiNbO3 is applied to form a integrated optical waveguide array in optical beamforming network, it is shown that microwave phase shifts within the range of [-180, +180] is achieved by tuning the optical wavelength 10 nm around 1.55 µm.

Conventional adaptive array antenna processing must access signals on all of the array antenna elements. However, because the low-cost electronically steerable passive array radiator (ESPAR) antenna only has a single-port output, all of the signals on the antenna elements cannot be observed. In this paper, a technique for adaptively controlling the loaded reactances on the passive radiators, thus forming both beam and nulls, is presented for the ESPAR antenna. The adaptive algorithm is based on the steepest gradient theory, where the reactances are sequentially perturbed to determine the gradient vector. Simulations show that the ESPAR antenna can be adaptive. The statistical performance of the output SIR of the ESPAR antenna is also given.

This paper proposes a 2.6 GHz low cost DBF array antenna system and reports its evaluation based on our experimental results. The proposed system is partially constructed by digital devices for the simplification of hardware, and employs some techniques for improving the resolution. The system is evaluated through the DOA estimation by the MUSIC algorithm inside a radio anechoic chamber. As a result, we found that the proposed system estimates the DOA with the highest accuracy at which MUSIC algorithm can perform. Moreover, this paper discusses the estimation errors. We also found that the estimation error is particularly affected from the inaccurate element interval.

Personal identity verification has a great variety of applications including access to computer terminals, buildings, credit card verification as well as EC. Algorithms for personal identity verification can be roughly classified into four categories depending on static/dynamic and biometric/physical or knowledge based. Finger prints, iris, retina, DNA, face, blood vessels, for instance, are static and biometric. Algorithms which are biometric and dynamic include lip movements, body movements and on-line signatures. Schemes which use passwords are static and knowledge based, whereas methods using magnetic cards and IC cards are physical. Each scheme naturally has its own advantages and disadvantages. A new algorithm is proposed for pen-input on-line signature verification incorporating pen-position, pen-pressure and pen-inclinations trajectories. A preliminary experiment is performed on a data base consisting of 293 genuine writings and 540 forgery writings, from 8 individuals. Average correct verification rate was 97.6% whereas average forgery refection rate was 98.7%. Since no fine tuning was done, this preliminary result looks very promising.

Making up a microwave simulator is tried, which has an analysis method based on the finite-element method as a solver and commercial tools as a pre- and post-processor of a graphical user interface. The platform of this simulator is Windows, but, since the codes and configuration files to be created are common on Windows, Unix, and Linux, the simulator running on any platform may be made up at the same time, except a document on which all the commands of the simulator are embedded and executable. Using the simulator, the transmission properties of a 2- and 3-D waveguide discontinuity in a microwave circuit and eigenmodes of a 2- and 3-D waveguide are analyzed, and the computed results are presented in graphs of S parameters and plots of the electric field distribution.

A gradient ascent learning algorithm of the Hopfield neural networks for graph planarization is presented. This learning algorithm uses the Hopfield neural network to get a near-maximal planar subgraph, and increases the energy by modifying parameters in a gradient ascent direction to help the network escape from the state of the near-maximal planar subgraph to the state of the maximal planar subgraph or better one. The proposed algorithm is applied to several graphs up to 150 vertices and 1064 edges. The performance of our algorithm is compared with that of Takefuji/Lee's method. Simulation results show that the proposed algorithm is much better than Takefuji/Lee's method in terms of the solution quality for every tested graph.

Personal authentication technologies will be necessary to ensure security of electronic transactions over open networks. Although biometric authentication is one of the most efficient approaches, accuracy of the biometric authentication is affected by the environment of the data acquisition, procedural parameters, and so on. There is as yet no means of giving a fair comparison of the accuracy of products of biometric vendors. Therefore, a standardization of the accuracy evaluation is necessary. This paper gives a standardization of the accuracy evaluation for the fingerprint verification system.

This paper introduces a new approach based on the geographic nearest neighbors for constructing the Delaunay triangulation (a dual of the Voronoi diagram) of a set of n sites in the plane under the L1 metric. In general, there is no inclusion relationship between the Delaunay triangulation and the octant neighbor graph. We however find that under the L1 metric the octant neighbor graph contains at least one edge of each triangle in the Delaunay triangulation. By using this observation and employing a range tree scheme, we design an algorithm for constructing the Delaunay triangulation (thus the Voronoi diagram) in the L1 metric. This algorithm takes O(n log n) sequential time for constructing the Delaunay triangulation in the L1 metric. This algorithm can easily be parallelized, and takes O(log n) time with O(n) processors on a CREW-PRAM.

Constant Modulus Algorithm (CMA) is a method that has been widely known as blind adaptive beamforming because it requires no knowledge about the signal except that the transmitted signal waveform has a constant envelope. Although CMA has the merit of this blind operation, it possesses problems in its convergence property. In this paper, problems that are inherent to this algorithm is resolved using a combination of CMA and another major adaptive algorithm SMI (Sample Matrix Inversion). The idea is to use SMI to determine the initial weights for CMA operation. Although the benefit of CMA being a blind algorithm is not fully taken advantage of, good aspects of both SMI and CMA can be introduced. By using this approach, two major problems in convergence properties of CMA can be solved. One of these problems is the reliability and this relates to the convergence performance in certain cases. When the interfering signal is stronger than the desired signal, the algorithm tends to come up with the wrong solution by capturing the interfering signal which has the stronger power. Also, the convergence time of this algorithm is slow, limiting its application in dynamic environment, although the slow convergence time of CMA has been studied previously and several methods have been proposed to overcome this defect. Using the proposed method, the deterioration due to both of these problems can be mitigated. Simulation results are shown to confirm the theory. Furthermore, evaluations are done concerning the fading characteristics. It is also confirmed from the simulation that the tracking performance of this method can be regarded as sufficient in personal mobile communication.

In this paper, we present a dynamic output feedback controller design technique for robust decentralized stabilization of uncertain large-scale systems with time-delay in the subsystem interconnections. Based on Lyapunov second method, a sufficient condition for the stability, is derived in terms of three linear matrix inequalities (LMI). The solutions of the LMIs can be easily obtained using efficient convex optimization techniques. A numerical example is given to illustrate the proposed method.

The ultrasonic wave is widely used for acquiring perceptual information necessary for indoor/outdoor navigation of mobile robots, where the system is implemented as a sound navigation and ranging system (sonar). A robot equipped with multiple ultrasonic sonars is likely to exhibit undesirable operation due to erroneous measurements resulting from cross-talk among the sonars. Each sonar transmits and receives a pulse-modulated ultrasonic wave for measuring the range and identifying its own signal. We propose a technique for generating pulse patterns for multiple concurrently operated ultrasonic sonars. The approach considers pulse-pattern generation as a combinatorial optimization problem which can be solved by a genetic algorithm (GA). The aim is to acquire a pulse pattern satisfying certain conditions in order to avoid cross-talk or keep the probability of erroneous measurement caused by cross-talk low. We provide a method of genotype coding for the generation of the pulse pattern. Furthermore, in order to avoid a futile search encountered when the conventional technique is used, we propose an improved genotype coding technique that yields considerably different results from those of the conventional technique.

This paper proposes a fast algebraic codebook search for DSVD applications. In this method, the codebook search is simplified by reducing the number of possible position combinations using a mean-based track threshold multiplied by heuristically determined optimum threshold factor. And, to guarantee a complexity requirement of DSVD, the maximum number of searching position combinations is limited to 320. The proposed method reduced computational complexity considerably, compared with G.729 with a slight degradation of SNR. Particularly, it shows better speech quality with lower complexity than G.729A.

To improve the unstable performance of the traditional keyword-based search engine due to ambiguities of a natural language such as synonymy and /or polysemy, we have developed a new advanced DLSI (differential latent semantic index) space based probabilistic information retrieval system. The new method exploits a most likelihood posteriori function providing a measure of reliability in retrieving a document in the database having a closest match with another document of a query. Our simple experiment gives a supporting evidence for the validity of the theory, which is capable of capturing the intricate variability in word usage contributing to a more robust context contingent search engine.

AAL2 technology, which will be used in 3rd generation mobile communications systems, can be used to efficiently transmit low-bit-rate traffic. Because user connections are multiplexed at virtual-channel connections in AAL2 networks, conventional ATM QoS management, which operates in units of VC connections, may be inadequate for managing the QoS of AAL2 connections. In this paper, we argue that for efficient utilization of network resources, it is advantageous to accommodate AAL2 connections with different QoS conditions in the same VC connection. We present a multiplexing configuration that enables QoS to be controlled at the AAL2-connection level. It works by matching the AAL2-packet-multiplexing timing to the cell-transmission timing. We also address the issue of AAL2-bandwidth management. To calculate the bandwidth, we evaluate the characteristics of multiplexing CPS packets into the ATM cell payload.