The dynamic channel assignment (DCA) strategy proposed here uses information on the mobile station speed and direction of motion to reduce the number of forced call terminations and channel changes in micro cellular systems. This SMD (speed and moving direction) strategy is compared with the main DCA strategies by simulating a one-dimensional service area covering a road on which there are high-speed mobile stations (HSMSs) and low-speed mobile stations (LSMSs).The simulation results show that the SMD strategy has the best performance in terms of forced call termination and channel change. The performance difference between the SMD strategy and the other DCA strategies increases as cell size decreases and as HSMS speed increases. While the SMD strategy does not yield the best total call blocking rate, its total carried load is the best when cells are small and HSMS speed is high. Also, the SMD performance improves when the HSMS offered load is small and the LSMS offered load is large. Although the SMD strategy requires information on the speed and direction of each mobile station and it increases call blockings somewhat, it reduces the number of forced call terminations and channel changes considerably, which is important in micro cellular systems.

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 novel circuit design technique for bipolar linear transconductance amplifiers is presented. A triple-tail cell, which consists of three emitter-common transistors biased by a single tail current, is exchangeable with an emitter-coupled pair in the multi-tanh cell, such as a multi-tanh doublet, a multi-tanh triplet or a multi-tanh quad. Therefore, the multi-tanh technique is further theoretically expanded to the super-multi-tanh technique. In this paper, the super-multi-tanh technique is proposed and discussed, and furthermore, a super-multi-tanh doublet is verified with bipolar transistor-arrays and discrete resistors on a breadboard.

In this study, we discuss a discrete-time cellular neural network (DTCNN) and its applications including convergence property and stability. Two theorems about the convergence condition of nonreciprocal non-uniform DTCNNs are described, which cover those of reciprocal one as a special case. Thus, it can be applied to wide classes of image processings, such as associative memories, multiple visual patterns recognition and others. Our DTCNN realized by the software simulation can largely reduce the computational time compared to the continuous-time CNN.

This paper proposes an integrated interference suppression scheme which realizes interference-resistant satellite digital signal transmission systems. It employs a notch filter in the receiving side to suppress the co-channel interference (CCI) signal. Moreover, the proposed scheme employs an adaptive equalizer combined with a forward error correction (FEC) scheme to improve the Pe (probability of error) performance degradation due to the inter-symbol interference caused by notch filtering of the desired signal. In the typical frequency modulation (FM) CCI environment with a BWi/FN of 2.3 (BWi: interference signal required bandwidth, fN: one half the Nyquist bandwidth of the desired signal), a Δf / fN of 1.05 (Δf: interference frequency offset) and a D/U of 3 dB (desired to undesired (interference) signal power ratio), the proposed scheme improves the required Eb/NO by 1.5 dB at a Pe of 10-4 compared to that without an adaptive equalizer.

We propose a novel architecture (Switched Access Star: SAS) using an optical switch for access networks and prove its operating principle experimentally. In this architecture, the multiple optical network units (ONUs) in subscriber premises are connected to one optical subscriber unit (OSU) in a central office through an optical switch. SAS can increase the number of accommodated ONUs, the transmission line length, and the capacity per ONU. Moreover, this architecture does not need encryption or ID/passwords. SAS can reduce system cost and yield flexible transmission capacities and realize easy management and maintenance of optical transmission lines.

Distributed shared memory is an attractive option for realizing functionally distributed computing in a wide area distributed environment, because of its simplicity and flexibility in software programming. However, up till now, distributed shared memory has mainly been studied in a local environment. In a widely distributed environment, latency of communication greatly affects system performance. Moreover, bandwidth of networks available in a wide area is dramatically increasing recently. DSM architecture using high performance networks must be different from the case of low speed networks being used. In this paper, distributed shared memory models in a widely distributed environment are discussed and evaluated. First, existing distributed shared memory models are examined: They are shared virtual memory and replicated shared memory. Next, an improved replicated shared memory model, which uses internal machine memory, is proposed. In this model, we assume the existence of a seamless, multi-cast wide area network infrastructure - for example, an ATM network. A prototype of this model using multi-thread programming have been implemented on multi-CPU SPARCstations and an ATM-LAN. These DSM models are compared with SCRAMNetTM, whose mechanism is based on replicated shared memory. Results from this evaluation show the superiority of the replicated shared memory compared to shared virtual memory when the length of the network is large. While replicated shared memory using external memory is influenced by the ratio of local and global accesses, replicated shared memory using internal machine memory is suitable for a wide variety of cases. The replicated shared memory model is considered to be suitable particularly for applications which impose real time operation in a widely distributed environment, since some latency hiding techniques such as context switching or data prefetching are not effective for real time demands.

In general, a time-limited signal such as a single sinusoidal waveform framed by a frame period T can be utilized for conveying a multi-level symbol in data transmission. If such a signal is analyzed by the conventional DFT (Discrete Fourier Transform) analysis, the infinite number of frequency components with frequency spacing fD = T1 is needed. This limits the accuracy with which the original frequency of the unframed sinusoidal waverform can be identified. It is especially difficult to identify two similar framed sinusoids whose frequency spacing is narrower than fD. An analytical principle for time-limited signals is therefore proposed by introducing the concept of an Extended Frame into DFT. Waveform analysis more accurate than DFT is achieved by taking into account multiple correlations between extended frames made of an input frame signal and the element frequency components corresponding to the length of each extended frame. In this approach, it is possible to use arbitrary element frequency spacing less than fD. It also allows an element frequency to be selected as a real number times of fD, rather than as an integer times of fD that is used for DFT. With this analyzing mechanism, it is verified that an input frame signal with only the frequency components which coincide with any of the element frequencies can be exactly analyzed. The disturbance caused by the input white noise is examined. As a result, it is found that the superior noise suppression function is achieved by this method over a conventional matched filter. In addition, the error caused by using a finite number of element frequencies and the A/D conversion accuracy required for sampling an input signal are examined, and it is shown that these factors need not impede practical implementation. For this reason, this principle is useful for multi-ary transmission systems, noise tolerant receivers, or systems requiring precise filtering of time limited waveforms.

One of coupling coefficients appearing in the coupled power equations describing the crosstalk in an image fiber is derived based on the coupled mode theory. Cores arranged in the cross-section of the fiber differ randomly to the degree of several percent in size and consequently modes propagating along the cores differ randomly. Random fluctuations of the propagation constants of modes cause the random transfer process of power between the cores, whereas contributions of the random fluctuations of the mode coupling coefficients to the statistical process can be neglected. The coupling coefficient is described as the ratio of the power transfer ratio to the coupling length for two cores with slightly different radii characterizing the random cores. The theoretical results are in good agreement with measurement results except near cutoff.

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.

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.

This paper describes the new analog-digital merged circuit architecture which utilizes the pulse modulation signals. By reconsidering the information representing and processing principles, and the circuit operations governed by the physical law, the new circuit architecture is proposed to overcome the limitations of existent VLSI technologies. The proposed architecture utilizes the pulse width modulation (PWM) signal which has analog information in the time domain, and be constructed with the novel PWM circuits which carry out the multi-input arithmetic operations, the signal conversions and the data storage. It has a potential to exploit the high speed switching capability of deep sub-µm devices, and to reduce the number of devices and the power dissipation to one-tenth of those of the binary digital circuits. Therefore it will effectively implement the intelligent processing systems utilizing 0.5-0.2µm scaled CMOS devices.

An ATM network design algorithm is treated as a resource allocation problem. As an effective way to facilitate a coexistence of traffic with its diverse characteristics and different quality of service (QOS) requirements in ATM networks, a virtual path (VP) concept has been proposed. In attempting to design the VP (Virtual Path)-based ATM network, it requires to consider a network topology and traffic pattern generated from users for minimizing a network construction cost while satisfying QOS requirements such as cell / call loss probabilities and cell delay times. In this paper, we propose a new heuristic design algorithm for the VP-based ATM network under QOS constraints. A minimum bandwidth required to transfer a given amount of traffic is first obtained by utilizing an equivalent bandwidth method. After all the routes of VPs are temporarily established by means of the shortest paths, we try to minimize the network cost through the alternation of VP route, the separation of a single VP into several VPs, and the introduction of VCX nodes. To evaluate our design algorithm, we consider two kinds of traffic; voice traffic as low speed service and still picture traffic as high speed service. Through numerical examples, we demonstrate that our design method can achieve an efficient use of network resources, which results in the cost-effective VP-based ATM network.

The electrical characteristics of sealed CMOSFETs with gates crossing sources/drains at 90 and 45 are experimentally investigated using test devices fabricated by an n-well CMOS process with trench isolation. Gain factors of surface-channel 90 and 45 n-MOSFETs can be estimated by a simple correction theory based on the combination of a center MOSFET and two edge MOSFETs. However, relatively large departures from the theory are observed in buried-channel 90 and 45 p-MOSFETs with widths less than the channel length. The difference between n- and p-MOSFETs is mainly due to the channel type. Other basic device parameters such as saturation drain currents, threshold voltages, subthreshold swings, maximum substrate currents and substrate-voltage dependence of threshold voltages are also measured and qualitatively explained.

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.

This letter shows that a portable visual stimulator for MEG measurements can be realized using an optical fiber bundle and a CRT display system offering high brightness and high speed raster scanning, and that MEGs with neither magnetic contamination nor jitter can be measured by the stimulator.

Shortened prime codes (SPR-codes) are presented, which can maintain the fixed code weight for any arbitrary number of codewords while still preserve the same cross and auto-correlation constraints as original prime codes. The use of SPR-codes can reduce both cost and power loss of optical encoders/decoders. Tunable all-optical SPR-code encoders are also designed, which are based on rapidly tunable optical delay lines. It is shown that using this type of encoders not only can further reduce the coding power loss, but also can achieve a very cost-effective fashion.

The degradation of I-V characteristics under constant emitter-base reverse voltage stress in advanced self-aligned bipolar transistors was analyzed. Experimental analyses have been taken the stress field effect into account when predicting hot-carrier degradation. These analyses showed that base current starts to increase when the reverse voltage stress is about 3 V. The dependence of the base current change on reverse voltages of more than 3 V was also investigated experimentally, and equations expressing hot-carrier degradation in terms of the exponential dependence of excess base current on both reverse stress voltage and stress-enhancing voltage related to emitter-base breakdown voltage were derived.

A direct gradient descent learning algorithm of energy function in Hopfield neural networks is proposed. The gradient descent learning is not performed on usual error functions, but the Hopfield energy functions directly. We demonstrate the algorithm by testing it on an analog-to-digital conversion and an associative memory problems.

This letter presents a new design method for approximate inverse systems using all-pass networks. The efficacy of approximate inverse systems for input and parameter estimation of nonminimum phase systems is well recognized. in the previous methods, only time domain design of FIR (finite impulse response) type approximate inverse systems were considered. Here, we demonstrate that IIR (infinite impulse response) type approximate inverse systems outperform the previous methods. A nonlinear optimization technique is adopted for designing the proposed system in the frequency domain. Numerical examples are also presented to show the effectiveness of the proposed method.