A multicarrier modulation is considered as an effective technique in high speed digital transmission under the multipath fading. In this paper, we theoretically analyze the bit error rate (BER) performance of the multicarrier modulation/differential detection scheme, and show the trade-offs between the BERs and the number of carriers or the guard period to clarify the optimum values to minimize the BER in the number of carriers and the guard period.

With rapid increase of information requirements from various application areas, there has been much research on the efficient information retrieval. A signature is an abstraction of information, and has been applied in many proposals of information retrieval systems. In this paper we evaluate the performance of various signature-based information retrieval methods and provide guidelines for the most effective usage to a given operational environment. We derive analytic performance evaluation models of these access methods based on retrieval time, storage overhead and insertion time. The relationships between various performance parameters are thoroughly investigated. We also perform simulation experiments by using wide range of parameter values and show that the performance experiments agree with those analytic models.

In this paper, we will define Kleene-Stone logic functions which are functions F: [0, 1]n[0, 1] including the intuitionistic negation into fuzzy logic functions, and they can easily represent the concepts of necessity and possibility which are important concepts of many-valued logic systems. A set of Kleene-Stone logic functions is one of the models of Kleene-Stone algebra, which is both Kleene algebra and Stone algebra, as same as a set of fuzzy logic functions is one of the models of Kleene algebra. This paper, especially, describes some algebraic properties and representation of Kleene-Stone logic functions.

Let C{c1, , cm} be a family of subsets of a finite set S{1, , n}, a subset S of S is a co-hitting set if S contains no element of C as a subset. By using an O((log n)2) time EREW PRAM algorithm for a maximal independent set problem (MIS), we show that a maximal co-hitting set for S can be computed on an EREW PRAN in time O(αβ(log(nm))2) using O(n2 m) processors, where αmax{|cii1, , n} and βmax{|djj1, , n} with dj{ci|jci}. This implies that if αβO((log(nm))k) then the problem is solvable in NC.

This paper proposes fiber optic link configurations for use in microwave and millimeter-wave transmission Higher frequencies,such as millimeter-waves, are well suited to transmission of broadband signals. Photodiodes can operate simultaneously as optical detectors and microwave frequency mixers thanks to their inherent nonlinearities. This allows us to increase the output radio frequncy. But, this also generates undesired spurious frequencies, necessitating the use of microwave filters. We discuss here two fiber optic link configurations, i.e., balanced/image canceling photodiode mixing links utilizing the combination of microwave functional components and optical devices to suppress the local/image frequency without filters. These configurations are experimentally investigated at microwave frequencies and local/image frequency suppression is successfully demonstrated.

This paper proposes and investigates an adaptive equalizer with diversity-combining over a multipath fading channel. It consists of two space-diversity antennas and a Ts/2-spaced decision-feedback-equalizer (DFE). Received signals from the two antennas are alternatively switched and fed into the feed forward-filter of DFE. We call this structure a Switched Input Combining Equalizer with diversity-combining (SICE). By using an SICE, the receiver structure for combining diversity equalization can be simplified, because it needs only two receiver sections up to IF BPF. The bit error rate (BER) performance of SICE was evaluated by both computer simulation and experiment over a multipath fading channel. We experimentally confirmed the excellent BER performance, around 1% of BER over a multipath fading channel at 160Hz of maximum doppler fading frequency. Therefore, the proposed SICE is applicable to highly reliable transmission in the 1.5-GHz-band mobile radio.

This paper presents the successful performance of an optical waveguide phase controller for microwave signals generated by heterodyne photodetection. A 22 optical waveguide structure with four optical phase shifters was fabricated on a LiNbO3 substrate. As a result of heterodyne photodetection of two optical signals from wavelength-tunable laser diodes, two microwave signals at 585 MHz were generated and phase shifted in the manner of electro-optical phase retardation. The monolithic waveguide structure allowed linear phase shifting more than 1800 degrees. Similar phase shifting performances were also confirmed over a wide microwave frequency range from 300 MHz to 1.3 GHz. The optical waveguide structure demonstrated here will be applicable to fiber-optic fed microwave systems such as a phased array antenna.

Marc Kellner proposed an example problem intending to compare modeling and describing techniques of software process. In this paper, we will describe our approach to understanding and describing the problem, from a process/product relation view, and synchronization/concurrent view. Also, we will show that a description of the problem is translated for execution and its correctness is validated.

This paper describes a fiber-optic microcell radio system with a spectral delivery switch to meet traffic demands. Optical link performance is discussed from the view points of link loss and noise figure aimed at system design. The theoretical carrier-to-noise ratio (CNR) performance is shown as a function of the input electrical power of the laser and the received optical power. Improvement of dynamic range defined by both CNR and intermodulation distortion is proposed by using the frequency modulation (FM) technique. The experimental results using the proposed technique indicate that the performance is much better than that of conventional methods. Moreover, economical diversity planning delivery methods over fibers are presented. This strategy will provide more cost effective and flexible networks.

This paper discusses the conversion of spatial resolution (pixel density) and amplitude resolution (levels of brightness) for multilevel images. A source image is sampled by an image scanner or a video camera, and a converted image is printed by a printer with the capability of higher spatial but lower amplitude resolution than the image input device. In the proposed method, the impulse response of the scanner sensor is modeled to obtain pixel values from the convolution of the impulse and the image signal. Discontinuous areas (edge) of the original image are detected locally according to the impulse model and neighbouring pixel values. The edge route is estimated which gives the pixel values for the output resolutions. Comparison of the proposed method with two conventional methods, reciprocal distance weight interpolation and pixel replication, shows higher edge quality for the proposed method.

An optimal algorithm for decomposing a special type of the Hasse diagram into a minimum set of disjoint paths is described. It is useful for testing the consistency of functional dependencies.

A coplanar-type TW electrode is analyzed for the use within a Ti:LiNbO3 optical modulator. The quasistatic analysis is developed based on the variational principle and the incremental inductance formula. The anisotropy of the LiNbO3, the effect of the SiO2 buffer layer, the overlaid conductor and the electrode thickness can be taken into consideration easily by using the extended spectral domain approach (ESDA) as the formulation procedure. It is shown numerically that the TW electrodes thickness, t, and the overlay spacing, p, are as dominant as the buffer layer thickness d, i.e., the microwave effective index and the product ΔfL is affected significantly by the electrodes thickness t and the overlay spacing, whereas the product VπL is insensitive. Therefore, the introduction of the overlaid conductor and the use of thicker electrodes can be utilized effectively to achieve higher values of the figure of merit Δf/Vπ.

We apply Fahlman and Lebiere's (FL) algorithm to network synthesis and incremental learning by making use of already-trained networks, each performing a specified task, to design a system that performs a global or extended task without destroying the information gained by the previously trained nets. Investigation shows that the synthesized or expanded FL networks have generalization ability superior to Back propagation (BP) networks in which the number of newly added hidden units must be pre-specified.

An adaptive restoration algorithm is developed for binary images degraded nonadditively with flip noises. The true image is assumed to be a realization of a Markov Random Field (MRF) and the nonadditive flip noises are assumed to be statistically independent and asymmetric. Using the Expectation and Maximization (EM) method and approximating the Baum's auxiliary function, the degraded image is restored iteratively. The algorithm is implemented as follows. First, the unknown parameters and the true image are guessed or estimated roughly. Second, using the true image estimate, the Baum's auxiliary function is approximated and then the noise and MRF parameters are reestimated. To reestimate the MRF parameters the Maximum Pseudo-likelihood (MPL) method is used. Third, using the Iterated Conditional Modes (ICM) method, the true image is reestimated. The second and third steps are carried out iteratively until by some ad hoc criterion a critical point of EM algorithm is approximated. A number of simulation examples are presented which show the effectiveness of the algorithm and the parameter estimation procedures.

This paper describes a new technique for isolated word recognition that uses both pitch information and spectral information. In conventional methods, words with similar phoneme features tend to be misrecognized even if their phonemes are accented differently because these methods use only spectral information. It is possible to improve recognition accuracy by considering pitch patterns of words. Many phonetically-similar Japanese words are classified by pitch patterns. In this technique, a pitch pattern template is produced by averaging pitch patterns obtained from a set of words which have the same accent pattern. A measure for word recognition is proposed. This measure based on a combination of the phoneme likelihood and the pitch pattern distance which is the distance between a pitch pattern of an input speech and pitch pattern templates. Speaker-dependent word recognition experiments were carried out using 216 Japanese words uttered by five male and five female speakers. The proposed technique reduces the recognition error rate by 40% compared with the conventional method using only phoneme likelihood.

Several research institutions in Europe have developed set-ups for wide-band mobile radio communication measurements. The performance and evaluation has been coordinated in the framework of the cooperation in the field of scientific and technical research within the committees COST 207 COST 231. New parameters have been defined to improve the insight into performance limits of digital radio communication systems which are caused by propagation phenomena. The definitions of these new parameters are presented in the paper. Channel sounders developed in Norway, Denmark, the United Kingdom, Switzerland, France and Germany are described. They are based on considerably different technical principles for evaluation and recording of the measured results. A few results gained in European measurement campaigns are also presented.

An information retrieval system based on a dynamic thesaurus was developed utilizing the connectionist approach. The dynamic thesaurus consists of nodes, which represent each term of a thesaurus, and links, which represent the connections between nodes. Term information that is automatically extracted from user's relevant documents is used to change node weights and generate links. Thus, node weights and links reflect a user's interest. A document retrieval experiment using the dynamic thesaurus was conducted in which both a high recall rate and a high precision rate were achieved.

A new method for interpolating boundary function values and first derivatives of a triangle is presented. This method has a relatively simple construction and involves no compatibility constraints. The polynomial precision set of the interpolation function constructed includes all the cubic polynomial and less. The testing results show that the surface produced by the proposed method is better than the ones by weighted combination schemes in both of the fairness and preciseness.

A field trial was conducted to evaluate the technical performance of land mobile message communication in different environments. The OmniTRACS system and the Ku-band JCSAT satellite were utilized as the mobile communications system and the satellite, respectively. The trial took place in September 1990 at different areas in Japan. Data collected correspond to about 65 hours of operation, during which a large number of messages were sent via the satellite. Two land mobile terminals operated simultaneously, each terminal having a function of generating messages automatically which simulates a large volume of traffic corresponding to about 50 terminals. Thus, the system was evaluated under the condition that 100 mobile terminals were in operation. Obtained data have been analyzed with a particular focus on the message transmission correlating with actual environments. The analysis was done by classifying environments into five categories: overall condition, type of roads, terrain, areas and weather conditions. The average transmission count per message experienced under all conditions is equal to 1.432 for forward messages transmitted from the hub station to mobiles, and 1.157 for return messages transmitted from mobiles to the hub station. With respect to the classification by the type of roads, for enample it becomes obvious that the performance is generally good except along roads of North-South orientation through dense urban areas. It is concluded that the message communications from/to mobiles are feasible in a wide range of environments, with the performance of success essentially depending on the visibility of satellite.

Theoretical and experimental evaluations of the horizontal rotating and tilting of the base station antenna beam show that these techniques are effective in reducing delay spread. Result show good agreement between predicted and measured values.