So far, neuronal dendrites have been characterized as electrically passive cables. However, recent physiological findings have revealed complex dynamics due to active conductances distributed over dendrites. In particular, the voltage-gated calcium and calcium-activated conductances are essential for producing diverse neuronal dynamics and synaptic plasticity. In this paper, we investigate the functional significance of the dendritic calcium-activated dynamics by computer simulations. First, the dendritic calcium-activated responses are modeled in a discrete compartmental form based on the physiological findings. Second, the basic stimulus-response characteristics of the single compartment dendrite model are investigated. The model is shown to reproduce the neuronal responses qualitatively. Third, the spatio-temporal dynamics of the dendrite shafts are modeled by longitudinally connecting 10 single compartments with coupling constants which are responsible for the dendrite thickness. The thick dendrite models, corresponding to proximal dendrites, respond in a spatially cooperative manner to a localized constant or periodic current stimulation. In contrast, the highly activated compartments are forced to be localized in the neighborhood of the stimulation-site in the fine dendrite models corresponding to distal dendrites. These results suggest that dendritic activities are spatially cooperated in a site-dependent manner.

The polymer matrix for the number of N in-puts/outputs, N stages and 2x2-switches is denoted as the 1-D Spanke-Benes (SB) network. Throughout the paper, the 1-D SB-network, which equals the diamond cellular array, is extended to arbitrary dimensions by a mathematical transformation (a 1-D network provides the interconnection of 1-D data). This transformation determines the multistage architecture completely by providing size, location, geometry and wiring of the switches as well as it preserves properties of the networks, e.g., the capability of sorting. The SB-networks of dimension 3 are analysed and sorting is applied.

Quantum Cellular Automaton (QCA), which is one of the candidates for future integrable electron devices, is investigated from the viewpoint of operation temperature. The extended Hubbard model which can extract the physical essence of QCA is used to analyze the inter-cell interaction for a layered cell structure. We found that the operation energy estimated from the energy gap between the ground state and excited states of the layered structure is large enough to allow room temperature operation even if the size of quantum dot is as large as 500. The layered cell structure is found to be suitable for a memory application.

In this paper, we discuss problems in design and fault masking of multiple-valued cellular arrays where basic cells having simple switch functions are arranged iteratively. The stuck-at faults of switch cells are assumed to be fault models. First, we introduce a universal single-level array and derive the ratio of the number of single faults whose influence can be masked to the total number of single faults. Next, we propose a universal two-level array that outputs correct values even if single faults occur in it and derive the ratio of the number of double faults whose influence can be masked compared to the total number of double faults. By evaluating the universal single-level array and the universal two-level array from the viewpoints of design and fault masking, we show that the latter is superior to the former. Finally, we compare our universal two-level array with formerly presented arrays in order to demonstrate the advantages of our universal two-level array.

In this article, a new analogic CNN algorithm to extract features of postage stamps in gray-scale images Is introduced. The Gradient Controlled Diffusion method plays an important role in the approach. In our algorithm, it is used for smoothing and separating Arabic figures drawn with a color which is similar to the background color. We extract Arabic figures in postage stamps by combining Gradient Controlled Diffusion with nearest neighbor linear CNN template and logic operations. Applying the feature extraction algorithm to different test images it has been verified that it is also effective in complex segmentation problems

In this paper, Chay's bursting pancreatic β-cell model is updated to include a role for [Ca2+]ER, the luminal calcium concentration in the endoplasmic reticulum (ER). The model contains a calcium current which is activated by voltage and inactivated by [Ca2+]i. It also contains a cationic nonselective current (INS) that is activated by depletion of luminal Ca2+ in the ER. In this model, [Ca2+]ER oscillates slowly, and this slow dynamic drives electrical bursting and the [Ca2+]i oscillations. This model is capable of providing answers to some puzzling phenomena,which the previous models could not (e. g., why do single pancreatic β-cells burst with a low frequency while the cells in an islet burst with a much higher frequency ?). Verification of the model prediction that [Ca2+]ER is a primary oscillator that drives electrical bursting and [Ca2+]i oscillations in pancreatic β-cells awaits experimental testing. Experiments using fluorescent dyes such as mag-fura-2-AM could provide relevant information.

Finite-difference time-domain (FDTD) analysis is performed to evaluate the distributions of specific absorption rate (SAR) in a human head during use of a handheld portable telephone. A heterogeneous head model has been assumed which is comprised of 273 108 cubic cells 2.5 mm on a side, with the electrical properties of anatomical equivalents. A handset model has been assumed to be a metal box with either a quarter-wavelength monopole or a half-wavelength dipole operating at 900 MHz or 1.5 GHz. The maximum local SARs in the head are evaluated under various exposure conditions. The dependence of the maximum local SARs on the difference in the structures or parameters of the model, i.e. the distance between the antenna and the head, the heterogeneity of the head, the antenna type, the volume of the smoothing region of the local SAR value, skin electrical constants, and the presence or absence of auricles, are examined. It is shown that the heterogeneity of the head barely affect the maximum local SAR when the telephone is located sufficiently close to the head. It is also shown that the electrical constants of skin which has lower conductivity provide the lower maximum local SAR in the head while the maximum local SAR within the brain is not significantly affected. The auricle which lies in closest proximity to the antenna is shown to have significant effect on the maximum local SAR. It is suggested that the presence of the auricle enhances the maximum local SAR by a factor that is 1.7-2.4 larger than the model without auricles.

Spread-spectrum (SS) sharing with comb spectrum structure in a microcell/macrocell cellular architecture in order to increase spectral efficiency is proposed. Such method employs a filter in the code division multiple access (CDMA) transmitter to feature comb spectrum structure, and suppress interference with a narrowband time division multiple access (TDMA) system in using together in SS sharing. The relationship between microcellular capacity and macrocellular capacity of the system is explored and compared to those of conventional SS sharing and orthogonal sharing. To be concrete, we investigate two cases, i.e., using no power control and ideal power control in the TDMA system. In both cases, the proposed SS sharing gives better capacity results than the conventional SS sharing and in the comparison when ideal power control is used in th. TDMA system, it even has the property to oppose the orthogonal sharing in ideal condition without interference.

In this paper, after the introduction of the definition of State Controlled Cellular Neural Networks (SC-CNNs), it is shown that they are able to generate complex dynamics of circuits showing strange behaviour. Theoretical propoitions are presented to fix the templates of the SC-CNNs in such a way as to exactly match the dynamic behaviour of the circuits considered. The easy and cheap implementation of the proposed SC-CNN devices is illustrated and a gallery of experimentally obtained strange attractors are shown to confirm the practical suitability of the outlined strategy.

Various applications of cellular neural network (CNN) are reported such as a feature extraction of the patterns, an extraction of the edges or corners of a figure, noise exclusion, searching in maze and so forth. In this paper, we propose a cellular neural network whose each cell has more than two output levels. By using the output function which has several saturated levels, each cell turns to have several output states. The multiple-valued CNN enhances its associative memory function so as to express various kinds of aspects. We report an application of the enhanced asscociative memory function to a diagnosis of the liver troubles.

Microcellular systems are suitable as personal mobile communication systems because of their high channel re-use efficiency and low transmission power. To implement a microcellular system, the antennas of base stations should be low enough, compared to the buildings around them, to reduce the interference to or from other base stations. In high-speed digital mobile radio communications, the time delay spread caused by multipath propagation is a significant factor in determining the maximum data transmission rate. In the case of a low-antenna-height microcellular system, the propagation characteristics rapidly change when the mobile terminal moves from a line-of-sight (LOS) location to a non-line-of-sight (NLOS) location. In this paper, the time dealy spread characteristics under LOS and NLOS conditions are examined using a geometrical street model which has a reflecting wall at one end of the street on which the base station is located. The RMS delay spreads are calculated using optical ray theory, taking into consideration the wedge diffraction on the street corner. If a reflecting wall exists, the RMS delay spread increases as the mobile terminal moves away from the base station under LOS conditions, or away from the street corner under NLOS conditions. The calculated results agree with the experimental results if measuring equipment noise is taken into consideration.

Hybrid direct sequence/slow frequency hopping-time division duplex (DS/SFH-TDD) multiple access system has some good features of each system. However it has a problem of hit between multiple users. If the designed frequency hopping patterns are inadequate, the quality of the multiple access system is degraded due to the frequent hit. In this paper, we propose an adaptive hopping pattern control system which is able to avoid the multiple access interference of hit. The proposed system decreases the influence of hit and increases the user capacity in the cell. And this adaptive hopping pattern control is applied to both single-cell and multi-cell systems. By computer simulation to evaluate the performance of this system, we found that this system is effective in increasing the multiple access capability.

This paper considers the evaluation of the acquisition performance for an access channel preamble based on the random access procedure of direct sequence code division multiple access (DS/CDMA) reverse link. The parallel acquisition technique that employs the single-dwell and multiple-dwell (double-dwell) detection schemes is investigated. The acquisition performance for two detection schemes is compared in terms of the acquisition probablity and the mean acquisition time. The parallel acquisition is done by a bank of N parallel I/Q noncoherent correlators. Expressions on the detection, false alarm, and miss probabilities of the single-dwell and multiple-dwell (double-dwell) detection schemes are derived for the multiple H1 cells and multipath Rayleigh fading channel. Comparing the single-dwell detection scheme with the multiple-dwell (double-dwell) detection scheme in the case of employing the parallel acquisition technique in the reverse link, the numerical results show that the single-dwell detection scheme provides a better performance.

The reverse link performance of coherent multicode DS-CDMA [4], [5] under multipath Rayleigh fading environments is evaluated by computer simulation. It is demonstrated that the combined use of pilot symbol assisted (PSA)-coherent RAKE, channel coding, antenna diversity, and transmit power control is powerful in lowering the required signal energy per information bit-to-interference plus additive white Gaussian nose (AWGN) power spectrum density ratio (Eb/Io) which is an important parameter in determining the link capacity. It is also demonstrated that with slight performance degradation, high rate data transmission is realized by using multiple orthogonal spreading codes in parallel (orthogonal multicode transmission). Based on the simulated link performance, the reverse link cell capacity and link budget are also evaluated. It is found that parameter η=Io/No plays an important role in controlling the cell capacity and the maximum allowable path loss, where No is the AWGN power spectrum density.

This paper compares the performance of an indoor cellular system in terms of capacity and channel assignment delay for different Dynamic Channel Assignment (DCA) and Fixed Channel Assignment (FCA) schemes. We refer to specific group of DCAs, namely Channel Segregation and Reuse Partitioning (RP). Our main concern is to show that these DCA schemes offer better performance than FCA. Since the structure and floor layout of a building will have a major influence on the propagation and hence on the cell shape, a path loss simulator is developed for predicting the path loss which is used in evolving base station layouts. Computer simulation, based on Monte Carlo method, is carried out using the path loss values and the base station layouts. The results indicate that increased traffic capacity can be achieved with all DCAs in comparison with FCA. The highest capacity and a shorter channel assignment delay are delivered by Self-Organized Reuse Partitioning DCA scheme.

This paper presents a model for a wide-band fading channel for terrestrial mobile applications. The model is based on the results of measurements made in a heavily built-up urban environment using a 25 MHz signal centred at approximately 2.6 GHz. This paper presents measured impulse responses and details the parameter extraction process used to determine the characteristics of the channel. These parameters are used in the channel simulation package and the output of these simulations are compared to the original data.

The paper deals with the evaluation of performance of current cellular systems which are required to accommodate in an already operating system a wide range of new services, with different quality requirements (on delays, retransmission rates, etc.), and often characterised by a high burstiness (i. e. with relatively short traffic bursts, interleaved by comparatively long silence periods). To this end, an extension of packet communications is appealing for its inherent flexibility; standardisation of packet protocols for data transmission over idle GSM channels is in progress, and a similar service exploiting AMPS radio and network resources is already specified as Cellular Digital Packet Data. In both cases voice traffic retains a higher priority. The paper focuses on the evaluation of the effect of this additional traffic on existing voice traffic in a GSM Phase 2+ system. Although voice calls experience the same channel availability, their performance are worsened by the higher co-channel interference due to the higher average channel occupancy. This impairment cannot be tackled, as a matter of course, by increasing the re-use distance as this would affect the overall system capacity. The paper suggests the use of smart planning strategies capable to ease control of interference levels with a negligible impact on system complexity and signalling load.

This paper proposes Channel Reservation for Ahead Cells (CRAC)" scheme for street micro-cellular systems. The scheme enables mobiles to reserve the same channel over several cells at once. This paper analyzes both CRAC and FCA (Fixed Channel Assignment) in a ring-shaped service area where high speed mobiles and low speed mobiles move. In the analysis, the priority control which prioritizes hand-off calls and reservation calls over new calls over new calls is also taken into account. Obtained results include the blocking rate, the forced call termination rate, the average number of channel changings and the system utilization. From numerical results, CRAC is found to perform better than FCA with regard to the average number of channel changings and the forced call termination rate.

Fundamental microwave key devices used in achieving compact mobile/portable telephones (raidio units) are discussed. The historical development flow of the systems and radio units are introduced, with respect to the 800-/900-MHz and 1.5-GHz Japanese cellular radio systems. The design concept of the developed radio units is briefly described. Tehnical requirements for RF circuits are reviewed and the developed key devices are practically applied to the circuits. Key factors in the requirements are also shown. Finally. future trends fro the key devices are surveyed from the stand point of achieving a smaller and more light weight pocket radio unit.

Taking a 1.5-GHz SAW antenna duplexer for PDC, we have developed a new configuration for the transmitter final stage filter and a new weighting technique for the receiver top filter. These transmitter and receiver filters provide insertion losses as low as 0.8 and 1.6 dB, respectively. Combining the filters, we have developed a miniature antenna duplexer of which size is 1.40.60.2 cm3 , several-time smaller than that of a conventional dielectric-filter duplexer. It also ensures sufficient power-handing capabilities.