Outage probability evaluation for a new category of wireless access systems is discussed. Wireless access systems dealt with in this paper are links which connect a portable terminal to a base station through a line-of-sight path. It is also assumed that the terminal equipment is operated in a still atate during actual communications. This mobility restriction enables the wireless access to have a capacity as high as the Mbit-order with high quality performance. Multipath fading observed in such a system may have more moderate variations than Rayleigh distribution. This paper tentatively designates the above wireless access as relocatable systems, and attempts to analyze their error performance, approximating the fading characteristics with Gamma-distribution. Also dynamic relations between bit error rate (BER) and signal-to-noise ratio are calculated under Gamma-distribution fading. Based on the analyses prediction methods for outage probability of typical QPSK systems are given, and thus it is established to design the performance aspect of relocatable systems with different features from both fixed and mobile systems.

This paper describes the use of direct wafer bonding technique to implement the novel concept of "free-material and free-orientation integration" which we propose. The technique is applied for various wafer combinations of an In-Ga-As-P material system with lattice- and orientation-mismatches. The properties of the bonded structures are studied in terms of the crystalline and electrical characterization. The high crystalline quality of the bonded structures with those mismatches is proved by transmission electron microscopy, and good electrical conduction was attained in some bonded structures of InP and GaAs. (001) InP-based 1.55-µm wavelength lasers are fabricated on (110) GaAs substrate by direct wafer bonding. The light-current characteristics of the lasers are almost identical to those of lasers fabricated on (001) InP and (001) GaAs substrates, while the turn-on voltage is a little bit higher due to the higher barrier height at the bonded interface. The practicability in those lasers are also examined. Furthermore, we show direct wafer bonding of a (001) InP-based structure and a (110) Si substrate with a GaAs buffer layer, aligning the cleavage planes of the InP and the Si. The results demonstrate the remarkable feasibility of using the direct wafer bonding technique to obtain integrated structures of material- and orientation-mismatched wafers with satisfactory quality.

A switched-capacitor phase-shifter oscillator of low distortion is discussed. The dc voltage related to the amplitude of oscillation was made for an automatic gain controller. The distortion factor was less than 0.5% in the frequency range from 100 µHz to 1 Hz.

Butt-joint waveguide couplings are fabricated for use in InP-based photonic integration, and characterized by scanning electron microscopy and optical transmission measurements. Several parameters have been optimized in the characterization study: size and shape of the mask protecting the first waveguide layer during butt-joint regrowth, and the crystallographic direction of the butt-joint interface. The studies show that high-quality butt-joints having negligible optical loss can be made with good fabrication tolerance. Using the optimized butt-joint, DBR-type, gain-clamped SOAs have been fabricated which are free of internal excess reflections. A constant optical gain of 21 dB is obtained up to a signal output power of 25 mW. The devices show CATV grade linearity in a 77 channel CATV linearity test at a distortion level of -55 dB below carrier.

The use of selective oxidation to fabricate vertical-cavity surface-emitting lasers is described. The nativeoxide impacts the device design in two ways, the first being in the introduction of an intracavity dielectric aperture that laterally confines the mode, and the second in the formation of high contrast dielectric Bragg reflectors to shorten the effective cavity length. To date the more important has been the indexconfinement, with record low threshold currents, threshold voltages, and power conversion efficiencies being reported from several groups. However, future designs will likely also benefit from the reduced diffraction loss for a small mode size that is possible with high contrast native oxide/semiconductor mirrors. We describe some of the most important design issues in obtaining ultralow threshold operation.

A Time-Division Multiplexed (TDM) Hierarchical Switching System (HSS), proposed by Eng and Acampora [5], provides any size of bandwidth for a number of subscribers by allocating proper number of time-slots in a frame. In this paper, we present a binary time-slot assignment (TSA) algorithm by which a proper size of time-slots in the frame are allocated to each subscriber so as to meet its bandwidth requests. The time complexity of the proposed algorithm is O(NLlog2 L) in which N is the number of input/output links of the central switch and L is the number of time-slots allotted to each link in the frame. As the authors know, the most efficient algorithm proposed in the literature has time complexity of O(min(L, M2)min(N, M)M2), in which M is the number of subscribers that is larger than N in TDM/HSS system. To give a clear idea of relative efficiency between two algorithms, let us give a typical situation of M = L = O(N2). In this configuration our algorithm makes a significant improvement in time complexity by the order of O(M2/log2M).

This paper describes a novel image reconstruction algorithm and experimental results of a 3-dimensional acoustical holographic imaging system which has a limited number of transducers distributed sparsely. The proposed algorithm is based on the conjugate gradient projection onto convex sets (CGPOCS), which allows the addition of convex sets constrained by a priori information to reduce ambiguity and extract resolution iteratively. By several experiments, it is proven that the concept of the new 3-D acoustic image reconstruction algorithm has following improvements:1. the artifacts caused by the spurious lobes can be reduced under the condition that the inter-spacing of elements is larger than the wave length,2. the instability caused by the lack of information about the actual point spread function (PSF) can be reduced,3. the actual PSF can be estimated concurrently with during the image reconstruction process.

This paper compares signal classification performance of multilayer neural networks (MLNNs) and linear filters (LFs). The MLNNs are useful for arbitrary waveform signal classification. On the other hand, LFS are useful for the signals, which are specified with frequency components. In this paper, both methods are compared based on frequency selective performance. The signals to be classified contain several frequency components. Furthermore, effects of the number of the signal samples are investigated. In this case, the frequency information may be lost to some extent. This makes the classification problems difficult. From practical viewpoint, computational complexity is also limited to the same level in both methods.IIR and FIR filters are compared. FIR filters with a direct form can save computations, which is independent of the filter order. IIR filters, on the other hand, cannot provide good signal classification deu to their phase distortion, and require a large amount of computations due to their recursive structure. When the number of the input samples is strictly limited, the signal vectors are widely distributed in the multi-dimensional signal space. In this case, signal classification by the LF method cannot provide a good performance. Because, they are designed to extract the frequency components. On the other hand, the MLNN method can form class regions in the signal vector space with high degree of freedom.

Random fluctuations of the propagation constants of modes along the fiber axis are taken into consideration and the power coupling coefficient between cores of an image fiber is theoretically derived. For the fiber used for the measurement in the previous paper (A. Komiyama, IEICE, vol.E79-C, no.2, pp.243-248, 1996) it is verified that the coupling coefficient can be described in terms of statistical properties of the propagation constants in the cross-section of the fiber.

This paper optimizes a hierarchical image transmission system based on the hierarchical modulation scheme in a band-limited Rayleigh fading channel. Authors analyze relations between hierarchical parameters and the image quality, and show that the existence of optimum hierarchical parameter that maximizes the received image quality.

We study state feedback control of discrete event systems described by the Golaszewski-Ramadge model. We derive a necessary and sufficient condition for the existence of a balanced state feedback controller under partial observations.

This paper proposes a data-localization scheduling scheme inside a processor-cluster for multigrain parallel processing, which hierarchically exploits parallelism among coarsegrain tasks like loops, medium-grain tasks like loop iterations and near-fine-grain tasks like statements. The proposed scheme assigns near-fine-grain or medium-grain tasks inside coarse-grain tasks onto processors inside a processor-cluster so that maximum parallelism can be exploited and inter-processor data transfer can be minimum after data-localization for coarse-grain tasks across processor-clusters. Performance evaluation on a multiprocessor system OSCAR shows that multigrain parallel processing with the proposed data-localization scheduling can reduce execution time for application programs by 10% compared with multigrain parallel processing without data-localization.

We present a general framework with which we can evaluate the flexibility and efficiency of various replay systems for parallel programs. In our approach, program monitoring is modeled by making a virtual dataflow program graph, referred to as a VDG, that includes all the instructions executed by the program. The behavior of the program replay is modeled on the parallel interpretation of a VDG based on two basic parallel execution models for dataflow program graphs: a data-driven model and a demand-driven model. Previous attempts to replay parallel programs, known as Instant Replay and P-Sequence, are also modeled as variations of the data-driven replay, i.e. the datadriven interpretation of a VDG. We show that the demand-driven replay, i.e. the demand-driven interpretation of a VDG, is more flexible in program replay than the data-driven replay since it allows better control of parallelism and a more selective replay. We also show that we can implement a demand-driven replay that requires almost the same amount of data to be saved during program monitoring as does the data-driven replay, and which eliminates any centralized bottleneck during program monitoring by optimizing the demand propagation and using an effective data structure.

We describe the implementation of an iterative method with the goal of gaining a long vector length. The strategy for vectorization by means of multipoint stencils used for discretization of the partial differential equations is discussed. Numerical experiments show that the strategy that requires certain restrictions on the number of grid points in the x and y directions improves the performance on the vector supercomputer.

This paper proposes an adaptive coding rate and process gain control technique with channel activation function to realize a CDMA based radio subsystem for multi-media communication services that include two types of media, i.e., fixed size data such as the computer data and still image, and constant bit rate data such as voice and video. The proposed system achieves high throughput data transmission for the fixed size data by controlling the process gain and coding rate according to the variation of the channel. Moreover, to adopt the constant bit rate data, the proposed system also employs a channel activation technique. Computer simulation confirms that the proposed system is very effective for multi-media communication services.

We extend the Rabin cryptosystem to the Eisenstein and Gauss fields. Methods for constructing the complete representation class and modulo operation of the ideal are presented. Based on these, we describe the methods of encryption and decryption. This proposed cryptosystem is shown to be as intractable as factorization, and recently presented low exponent attacks do not work against it.

In this paper, we propose a handoff scheme with two-level priority for the reservation of handoff request calls in mobile cellular radio systems. We assume two types of mobile subscribers with different distributions of moving speed, that is, users with low average moving speed (e.g., pedestrians) and high average moving speed (e.g., people in moving cars). A fixed number of channels in each cell are reserved exclusively for handoff request calls. Out of these number of channels, some are reserved exclusively for the high speed handoff request calls. The remaining channels are shared by both the originating and handoff request calls. In the proposed scheme, both kinds of handoff request calls make their own queues. The system is modeled by a three-dimensional Markov chain. We apply the Successive Over-Relaxation (SOR) method to obtain the equilibrium state probabilities. Blocking probabilities of calls, forced termination probabilities and average queue length of handoff calls of each type are evaluated. We can make the forced termination probabilities of handoff request calls smaller than the blocking probability of originating calls. Moreover, we can make the forced termination probability of high speed handoff request calls smaller than that of the low speed ones. Necessary queue size for the two kinds of handoff request calls are also estimated.

A method of planar curve classification, which is invariant to rotation, scaling and translation using the zerocrossings representation of wavelet transform was introduced. The description of the object is represented by taking a ratio between its two adjacent boundary points so it is invariant to object rotation, translation and size. Transforming this signal to zero-crossings representation using wavelet transform, the minimum distance between the object and model while shifting the signals each other, can be used as classification parameter.

A factorization method for a string polynomial called the constant method is proposed. This uses essentially three operations; classification of monomials, gcrd (greatest common right divisor), and lcrm (least common rigth multiple). This method can be applied to string polynomials except that their constants cannot be reduced to zeros by the linear transformation of variables. To factorize such excluded string polynomials, the naive method is also presented, which computes simply coefficients of two factors of a given polynomial, but is not efficient.

Highly parallel scalable multiprocessing systems (HMPs) are powerful tools for solving large-scale scientific and engineering problems. However, these machines are difficult to program since algorithms must exploit locality in order to achieve high performance. Vienna Fortran was the first fully specified data-parallel language for HMPs that provided features for the specification of data distribution and alignment at a high level of abstraction. In this paper we outline the major elements of Vienna Fortran and compare it to High Performance Fortran (HPF), a de-facto standard in this area. A significant weakness of HPF is its lack of support for many advanced applications, which require irregular data distributions and dynamic load balancing. We introduce HPF +, an extension of HPF based on Vienna Fortran, that provides the required functionality.