A new transmit permission control scheme applicable in multi-cell communication systems is proposed. In this scheme, by prohibiting the transmissions from the users with relatively high propagation loss to their connecting hub stations, level of multiple access interference is decreased, and hence throughput characteristics are improved. Moreover, we continue our discussion to propose two adaptive forms of the transmit permission control scheme, in which the prohibition condition becomes more intelligent by considering the level of the offered traffic loads to hub stations. These methods are utilized in a slotted Aloha random transmission of the spread spectrum packets, and on the uplinks of a low earth orbit satellite communication system as an example of the multi-cell systems. It is shown that the adaptive schemes exhibits significantly improved characteristics at all offered traffic loads in these systems.

A novel method has been developed to improve the dry etching selectivity of aluminum alloy with respect to photoresist by implanting ions into the patterned photoresist. The selectivity becomes 7.5, which is 5 times higher than that of the unimplanted case. Accordingly, this technology is very promising for fabricating multi-level interconnections in sub-half micron LSIs.

According as the fine LSI process technique develops, the technique to reduce power dissipation of high-frequency integrated analog circuits is getting more important. This paper describes a design of high-frequency integrator with low power dissipation for monolithic leapfrog filters. In the design of the conventional monolithic integrators, there has been a great dfficulty that a high-frequency integrator which can operate at low supply voltage cannot be realized without additional circuits, such as unbalanced-to-balanced conversion circuits and common-mode feedback circuits. The proposed integrator is based on the Miller integrator. By a PNP current mirror circuit, high CMRR is realized. However, the high-frequency characteristic of the integrator is independent of PNP transistors. In addition, it can operate at low supply voltage. The excess phase shift of the integrator is compensated by insertion of the compensation capacitance. The effectiveness of the proposed technique is confirmed by PSPICE simulation. The simulation results of the integrator shows that the common-mode gain is efficiently low and the virtual ground is realized, and that moderate phase compensation can be achieved. The simulation results of the 3rd-order leapfrog filter using the integrator shows that the 50 MHz-cutoff frequency filter is obtained. Its power dissipation in operating 2 V-supply voltage is 5.22 mW.

In this paper, a new encoding/decoding scheme of multiple-valued separable balanced codes is presented. These codes have 2m information digits and m (R - 2) check digits in radices R 4, 2m - 1 information digits and m + 1 check digits in R = 3, where code-length n = Rm. In actual use of code-lengths and radices, it is shown that the presented codes are relatively efficient in comparison with multiple-valued Berger codes which are known as optimal unordered codes. Meanwhile, the optimality of multiple-valued Berger codes is discussed.

In this paper, we give a direct proof of the result of Latteux and Turakainen that the full class of recursively enumerable languages can be obtained from minimal linear languages (which are generated by linear context-free grammars with only one nonterminal symbol) by Dyck reductions (which reduce pairs of parentheses to the empty word).

Existing edge detection methods provide unsatisfactory results when contrast changes largely within an image due to non-uniform illumination. Koch et al. developed an energy function based upon the Hopfield neural network, whose coefficients were fixed by trial and error, and remain constant for the entire image, irrespective of the differences in intensity level. This paper presents an improved edge detection method for non-uniformly illuminated images. We propose that the energy function coefficients for an image with inconsistent illumination should not remain fixed, rather should vary as a second-order function of the intensity differences between pixels, and actually use a schedule of changing coefficients. The results, compared with those of existing methods, suggest a better strategy for edge detection depending upon both the dynamic range of the original image pixel values as well as their contrast.

Recursive Diagonal Torus (RDT) is a class of interconnection network for massively parallel computers with 216 nodes. In this paper, message transfer algorithms on the RDT are proposed and discussed. First, a simple one-to-one message routing algorithm called the vector routing is introduced and its practical extension called the floating vector routing is proposed. In the floating vector routing both the diameter and average distance are improved compared with the fixed vector routing. Next, broadcasting and hypercube emulation algorithm scheme on the RDT are shown. Finally, deadlock-free message routing algorithms on the RDT are discussed. By a simple modification of the e-cube routing and a small numbers of additional virtual channels, both one-to-one message transfer and broadcast can be achieved without deadlock.

New series expressing the radiation fields from both axial and circumferential slots on a circular conducting cylinder are derived. These new series converge rapidly even for near fields. This letter includes useful figures showing characteristics of near fields calculated numerically using the new series.

A learning algorithm is presented for nearest neighbor pattern classifiers for the cases where mixed supervised and unsupervised training data are given. The classification rule includes rejection of outlier patterns and fuzzy classification. This partially supervised learning problem is formulated as a multiobjective program which reduces to purely super-vised case when all training data are supervised or to the other extreme of fully unsupervised one when all data are unsupervised. The learning, i. e. the solution process of this program is performed with a gradient method for searching a saddle point of the Lagrange function of the program.

A design of current-mode continuous-time filters for low voltage and high frequency applications using complementary bipolar current mirror pairs is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integration. Since the filters are based on the integrator type of realization, the proposed method can be used for a wide range of applications. The frequency of the filters can easily be changed by the DC controlling current. A fifth-order Butterworth and a thirdorder leapfrog filter with tunable cutoff frequencies from 20 MHz to 100 MHz are designed as examples and simulated by SPICE using standard bipolar parameters.

Throughout the paper, the proper operating of the self-routing principle in 2-D shuffle multistage interconnection networks (MINs) is analysed. (The notation 1-D MIN and 2-D MIN is applied for a MIN which interconnects 1-D and 2-D data, respectively.) Two different methods for self-routing in 2-D shuffle MINs are presented: (1) The application of self-routing in 1-D MINs by a switch-pattern preserving transformation of 1-D shuffle stages into 2-D shuffle stages (and vice versa) and (2) the general concept of self-routing in 2-D shuffle MINs based on self-routing with regard to each coordinate which is the original contribution of the paper. Several examples are provided which make the various problems transparent.

This paper introduces a new image representation method that is named the projective image representation (PIR). We consider an image as a collage of symmetric segments each of which can be well represented by its projection data of a single orientation. A quadtree-based method is adopted to decompose an image into variable sized segments according to the complexity within it. Also, we deal with the application of the PIR to the image compression and propose an efficient algorithm, the quadtree-structured projection vector quantization (QTPVQ) which combines the PIR with the VQ. As the VQ is carried out on the projection data instead of the pixel intensities of the segment, the QTPVQ successfully overcomes the drawbacks of the conventional VQ algorithms such as the blocking artifact and the difficulty in manipulating the large dimension. Above all, the QTPVQ improves the subjective quality greatly, especially at low bit rate, which makes it applicable to low bit rate image coding.

In this paper we discuss the relation between a one-way group homomorphism and a one-way ring homomorphism. Let U,V be finite abelian groups with #U=n. We show that if there exists a one-way group homomorphism f:UV, then there exists a one-way ring homomorphism F:ZnUZnImf. We also give examples of such ring homomorphisms which are one-way under a standard cryptographic assumption. This implies that there is an affirmative solution to an extended version of the open question raised by Feigenbaum and Merrit: Is there an encryption function f such that both f(x+y) and f(xy) can be efficiently computed from f(x) and f(y)? A multiple signature scheme is also given as an application of one-way ring homomorphisms.

Computer viruses, hackers, intrusions and ther computer crimes have recently become a serious security problem in information systems. Digital signatures are useful to defend against these threats, especially against computer viruses. This is because a modification of a file can be detected by checking the consistency of the originai file with its accompanying digital signature. But an executable program might have been infected with the viruses before the signature was created. In this case, the infection cannot be detected by signature verification and the origin of the infection cannot be specified either. In this paper, we propose a signature scheme in which one can sign right after the creation of an executable program. That is, when a user compiles a source program, the compiler automatically creates both the executable program and its signature. Thus viruses cannot infect the executable programs without detection. Moreover, we can specify the creator of contaminated executable programs. In our signature scheme, a signature is created from a set of secret integers stored in a compiler, which is calculated from a compiler-maker's secret key. Each compiler is possessed by only one user and it is used only when a secret value is fed into it. In this way a signature of an executable program and the compiler-owner are linked to each other. Despite these measures, an executable program could run abnormally because of an infection in prepro-cessing step, e.g. an infection of library files or included files. An infection of these files is detected by ordinary digital signatures. The proposed signature scheme together with digital signature against infection in the preprocessing step enables us to specify the origin of the infection. The name of the signature creator is not necessary for detecting an infection. So, an owner's public value is not searched in our scheme, and only a public value of a compiler-maker is required for signature verification. Furthermore, no one can use a compiler owned by another to create a proper signature.

In this communication we propose to solve the problem of reconstruction from limited data using a statistical regularization method based on a Bayesian information criterion. The minimization of the Bayesian information criterion, which is used here as an objective index to measure the goodness of an estimate, gives the optimum value of the smoothing parameter. By doing so, we could reduce the inversion problem to a simple minimization of a one-variable nonlinear function. The application of such a technique overcomes the nonuniqueness of the solution of the ill-posed problem and all shortcomings of many iterative methods. In the light of simulation and application to real data, we propose a slight modification to the Bayesian information criterion to reconstruct the wave energy distribution at the ionospheric base from the observation of radio wave electromagnetic field on the ground. The achieved results in both the inversion problem and the wave direction finding are very promising and may support other works so far suggested the use of Bayesian methods in the inversion of ill-posed problems to benefit from the valuable information brought by the a priori knowledge.

This paper presents a 15-GHz MMIC direct optical injection-locked oscillator (MMIC OILO) with very-wide locking range that uses photosensitive HBTs. The MMIC OILO consists of an HBT and a positive feedback circuit including a Q-damping variable resistor. By utilizing the high-fT/fmax photosensitive HBT, we realize both high-frequency oscillation of 15 GHz and increased equivalent electrical injection power. In addition to increasing the RF injection power, the Q-damping variable resistor effectively reduces the quality-factor of the oscillator, thus realizing the very wide locking range (f) of 567 MHz (f/fosc3.8%). The locking bandwidth of 3.8% is over 10 times wider than that of any yet reported microwave direct OILO. Furthermore, it is shown that the MMIC OILO can also work as a high-gain Q-variable filter photoreceiver by increasing a Q-damping variable resistance over the self-oscillation suppression range.

Exploitation of air interfaces for mobile communications is rapidly increasing because of diversified service demands, technology trends and radio propagation conditions. This paper summarizes the radio and optic interaction devices and systems that can solve the future problems resulting from spreading demands in mobile multimedia communications. The concept of the Virtual Free Space Network (Radio Highway Network) is proposed for universal mobile access networks that can support any mobile service or radio air-interface. As one example of the proposed network, the optical TDMA network for radio is analyzed and results of some theoretical calculations are shown.

We present a recursive algorithm for constructing linear discrete-time systems which interpolate the desired 1st-and 2nd-order information. The recursive algorithm constructs a new system and connects it to the previous system in the cascade form every time new information is added. These procedures yield a practical realization of all the interpolants.

In this paper, we propose a new method of dialogue data collection which can be used to evaluate modules of a spoken dialogue system. To evaluate the module, it is necessary to use suitable data. Human-human dialogue data have not been appropriate to module evaluation, because spontaneous data usually include too much specific phenomena such as fillers, restarts, pauses, and hesitations. Human-machine dialogue data have not been appropriate to module evaluation, because the dialogue was unnatural and the available vocabularies were limited. Here, we propose 'Hybrid method' for the collection of spoken dialogue data. The merit is that, the collected data can be used as test data for the evaluation of a spoken dialogue system without any modification. In our method a human takes the role of some modules of the system and the system, also, works as the other part of the system together. For example, humans works as the speech recognition module and the dialogue management and a machine does the other part, response generation module. The collected data are good for the evaluation of the speech recognition and the dialogue management modules. The reasons are as follows. (1) Lexicon: The lexicon was composed of limited words and dependent on the task. (2) Grammar: The intention expressed by the subjects were concise and clear. (3) Topics: There were few utterances outside the task domain. The collected data can be used test data for the evaluation of a spoken dialogue system without any modification.

This paper describes the performance of a predistorter implementation to a superluminescent diode (SLD) in fiber-optic wireless systems under the optical reflection. SLD intensity noise and 3rd-order intermodulation distortion (IM3) are experimentally compared with those of DFB-and FP-LD. It is observed that the IM3 of SLD has ideal 3rd characteristics and output noise remains unchanged against the number of optical connectors. It is also found that the predistorter reduces IM3 by 8 dB. Receiver sensitivity of the system is discussed from the view point of overall design. the BER performance of an SLD with predistorter using a π/4-QPSK signal as a subcarrier is also described theoretically and experimentally.