In this paper, we propose a novel power distribution method which can be adopted in case of the nonuniform distribution for mobiles in DS/CDMA distributed power cellular system. DS/SS distributed power cellular system has been proposed for achieving RAKE reception in micro-cellular environment. In forward link of this system, optimum power distribution method which can minimize the required total transmitting power has been discussed. The performance of this system has been shown in case of the uniform distribution for mobiles. In this paper, first, we propose a novel method in case of the nonuniform distribution. In the proposed method, replacing the path and its combinations of signals from base stations successively, we can find a new condition of less power distribution which is passed over in a conventional distribution method. We adopt simple distribution models for mobiles and compare the proposed method with the other methods by computing the total transmitting power and the quantity of calculations. As a result, we show that it is possible to almost obtain optimum power distribution by using the proposed method. Next, we adopt a nonuniform distribution model, in which the difference of the number of users exists only in the center cell. Using this model, we compare the proposed method with the other methods by computing the total transmitting power, the quantity of calculations, and a probability of impossible power distribution. Finally, in order to simplify and decrease the quantity of calculations of the proposed method, we propose a modified calculation algorithm which is applicable in case of that a new mobile station has increased. And we show the performance of this algorithm.

Cellular automata (CA) implementations are expected as potential test-pattern generators (TPGs) for Built-In Self-Testing of VLSI circuits, in which highly random parallel patterns ought to be generated with simple hardware. Objective here is to design one-dimensional, binary, and linear CA implementations with cyclic boundary conditions that can operate on maximum length of period. To provide maximum period of operations, it is necessary to bring some irregularities into the configurations. It is also expected for TPGs to make maximum or sufficiently long period of operations to prevent re-initialization. Our approach is to generate transition matrices based on fast parallel implementations of LFSRs which have trinomials as characteristic polynomials and then to modify the diagonal components. Some notable properties of diagonal vectors were observed.

A random access micro-cellular system based on CSMA (RAMCS/CSMA) is proposed. On uplink in RAMCS/ CSMA, packets are transmitted by means of CSMA at the same carrier frequency in any cell. On downlink, packets are broadcast conforming to TDMA, also at the same carrier frequency in any cell. In RAMCS/CSMA, deployed microcells produce higher system capacity. Nevertheless, " handoff on a terminal " isn't required. In this paper, overview of the system, fundamental uplink performance, and two kinds of power control methods are presented. As for the control methods, one is control according to packet priority. The other is a way according to location of a mobile terminal. By means of CSMA, throughput performance on uplink becomes great and is saturated at 0. 39 per cell. And the performance strongly depends on the threshold level on carrier sense. Such a throughput performance is peculiar to RAMCS/CSMA and different from an ordinary CSMA system. The optimum threshold is also indicated here. Furthermore, it is clarified that both power control methods highly improve the throughput performance. As a result, it is found that RAMCS/CSMA is excellent for mobile communications.

In this paper, a modified multi-step SIR-based down-link power control method is proposed. The main idea is to predict the variation of Rayleigh fading from the received signal-to-interference ratio and then to track it in time. A computer program is developed to simulate the performances of this new method as well as the original multi-step SIR-based method. Simulation results show that, of the two, the former performs better than the latter, even if the bit error rate of power control command is around 0. 001.

This paper aims at developing forward link power control methods for CDMA cellular systems. The purpose is to allocate available power to as many mobiles as possible. When a power allocation in the network is fixed, the power assigned to the cell where rare mobiles communicate is wasting, and moreover, is prohibitive if other cells fall short of transmitting power. In this case, re-allocation is necessary. Power control in this paper takes the form of allocating pilot and traffic power according to the different needs from each cell. Especially, the pilot power control method tends to balance nonuniformly imposed load through the network, and hence helps the network resources be utilized equally. With the proposed pilot control method, the number of simultaneously communicating mobiles increases by 10-25% over the reference methods.

In this paper, an efficient approach to the synthesis of CA (Cellular Architecture) -type FPGAs is presented. To exploit the array structure of cells in CA-type FPGAs, logic expressions called Maitra terms which can be mapped directly to the cell arrays are generated by using ETDDs (EXOR Ternary Decision Diagrams). Since a traversal of the ETDD is sufficient to generate a Maitra term which takes O (n) steps where n is the number of nodes in the ETDD, Maitra terms are generated very efficiently. The experiments show that the proposed method generates better results than existing methods.

For the power controlled DS-CDMA reverse link, two important issues must be addressed when using a Rake combiner with a limited path diversity order (defined as the number of resolved paths used for combining): the decrease in link capacity and the increase in peak transmit power. The peak transmit power is an important design parameter of transmit power amplifiers. In this paper, expressions for the achievable capacity and required peak transmit power under an multi-cell environment are developed. Based on the developed expressions, the relative capacity and required peak transmit power are evaluated theoretically and by Monte Carlo simulations under multipath Rayleigh fading environments with uniform and exponential power delay profiles. The effects of Rake based on maximal ratio combining (MRC) and selection combining (SC) are compared. The influence of the power delay profile shapes is also discussed.

Microcellular radio direct-sequence code division multiple access (DC-CDMA) system using optical link to connect their base stations to a central station is a solution of cost-effective and efficient spectrum reuse to meet the growing demand for mobile communications. In addition to the inherent multiuser interference (MUI) of CDMA signals, the system capacity is significantly reduced by a nonlinear distortion (NLD) due to the nonlinearity of optical link. In this paper, a two-stage cancellation technique is introduced into the system to cancel both the MUI and the NLD. It is performed at the receiver of the central station where the random ingredients of all user signals are estimated, and the MUI and the NLD are rebuilt and removed from the received signal. The validity of the cancellation technique is theoretically analyzed and shown by the numerical results. The analytical method and its results are also applicable to other general nonlinear CDMA.

Recently, the spatio-temporal filter using linear analog Cellular Neural Network (CNN), called CNN filter array, has been proposed for the purpose of dynamic image processing. In this paper, we propose a design method of descrete-time cellular neural network filter which selectively extracts the particular moving object from other moving objects and noise. The CNN filter array forms a spatio-temporal filter by arranging cells with a same function. Each of these cells is a simple linear analog temporal filter whose input is the weighted sum of its neighborhood inputs and outputs and each cell corresponds to each pixel. The CNN filter is formed by new model of discrete time CNN, and the filter parameters are determined by applying backpropagation algorithm in place of the analytic method. Since the number of connections between neurons in the CNN-type filter is relatively few, the required computation in the learning phase is reasonable amount. Further, the output S/N ratio is improved by introducing nonlinear element. That is, if the ratio of output to imput is smaller than a certain value, the output signal is treated as a noise signal and ought to be rejected. Through some examples, it is shown that the target object is enhanced in the noisy environment.

Recently, the number of users utilizing mobile communication services has increased greatly in many information and communication fields. In the future, the number of mobile communication system users will increase even faster, until the rate of diffusion ultimately reaches that of telephones. The day that each person has his own portable mobile terminal is not so far off. Moreover, the systems will not only be used as telephones but also as mobile computing for multimedia information. Digitalization technologies of mobile communication systems needed to realize such mobile computing will be introduced in this paper.

In this article, a new type of diffusion template and an analogic CNN algorithm using this diffusion template for detecting some lung cancer symptoms in X-ray films are proposed. The performance of the diffusion template is investigated and our CNN algorithm is verified to detect some key lung cancer symptoms, successfully.

Macro/microcellular systems have recently been proposed to accommodate both fast and slow moving users. If macrocells and microcells reuse the same frequency band in a macro/microcellular system, the interference between both types of cells can become a critical problem and degrade system capacity, particularly in CDMA systems. In this paper, Frequency Division CDMA (FD-CDMA) is applied to CDMA macro/spot-microcellular systems and uplink capacity is evaluated. The CDMA frequency band is divided into several subbands and both macrocells and microcells reuse the same subbands simultaneously. Interference signals from both types of cells are dispersed by dividing the frequency band, and performance degradation resulting from interference is reduced at both the macrocell and microcell. By reusing the same frequency band for macrocells and microcells, the system capacities become more flexible and can be changed according to variations in traffic. This paper describes the detail of the FD-CDMA system. Uplink capacities are calculated for some cell conditions such as microcell size or location through simulation evaluations. A comparison with a non-reuse subband system as well as results of adaptive control of subbands are described.

In a radio network, while deploying microcells enhances spectral efficiency, it increases handoff in number and puts restriction on mobility of a terminal. As a solution of this contradictory matter, we propose a random access micro-cellular system (RAMCS). In the system deployed microcells produce higher system capacity, and "handoff on a terminal" isn't required. Therefore flexible mobility is given to terminals, and a terminal becomes simple. The aspect of the air interface is as follows. On uplink, packets are transmitted by means of random access (e.g., slotted ALOHA) at the same channel in any cell. On downlink, packets are broadcast at the same carrier in any cell and they are picked out conforming to TDMA. In this paper, a model of RAMCS is proposed. In addition, characters of RAMCS (e.g., throughput, system capacity, and delay) are clarified comparing it with a primary cellular system, where a spectrum can be reused repeatedly in different cells.

Dynamic Channel Assignment (DCA), which improves the efficiency of channel use in cellular mobile communication systems, requires finding an available channel for a new call after the call origination. This causes the delay which is defined as the time elapsing between call origination and completion of the channel search. For system planning, it is important to evaluate the delay characteristic of DCA because the delay corresponds to the waiting time of a call and influences service quality. It is, however, difficult to theoretically analyze the delay characteristics except its worst case behavior. The time delay of DCA has not been theoretically analyzed. The objective of this paper is analyzing the distribution and the mean value of the delay theoretically. The theoretical techniques in this paper are based on the techniques for analyzing the blocking rate performance of DCA.

We present a high performance AlGaAs/GaAs power HBT with very low thermal resistance for digital cellular phones. Device structure with emitter air-bridge is utilized and device layout is optimized to reduce thermal resistance based on three-dimensional thermal flow analysis, and in spite of a rather thick substrate (100 µm), which achieved a low thermal resistance of 23/W for a multi-finger (440 µm240 fingers) HBT. This 40 finger HBT achieved power added efficiency (PAE) of over 53%, 29.1 dBm output power (Pout) and high associated gain (Ga) of 13.5 dB with 50 kHz adjacent channel leakage power (Padj) of less than -48 dBc under a 948 MHz π/4-shifted QPSK modulation with 3.4 V emitter-collector voltage. We also investigated the difference of RF performance between two bias modes (constant base voltage and current), and found which mode is adequate for each stage in several stage power amplifier for the first time.

This paper describes novel techniques for analyzing power MOSFETs. Since the gate width of power MOSFETs is much larger than that of power MESFETs or HJFETs, an appropriate device design to suppress matching circuit losses is needed. These losses and the intrinsic device characteristics are analyzed employing the proposed techniques, which are based on large-signal simulations. Also, new formulas describing the dependence of saturated output power on gate width are derived to perform loss-minimized design. These techniques are applied to the design of power MOSFETs for GSM cellular telephones. As a result, an output power of 35.5 dBm with a power-added efficiency of 55% and a power gain of 10.5 dB at 900 MHz have been achieved.

This paper describes cellular spaces (or cellular automata) with capabilities of parallel self-reproduction and of parallel universal simulation of other cellular spaces. It is shown that there is a 1-dimensional cellular space U, called a parallel universal simulator, that can simulate any given 1-dimensional cellular space S in the sense that if an initial configuration of U has a coded information of both the local function and an initial configuration of S, then U has the same computation result that S has and the computation time of U is proportional to that of S. Two models of nontrivial parallel self-reproduction are also shown. One model is based on "state-exchange" method, and the other is based on a fixed point program of the parallel universal simulator.

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 CMOS programmable gain amplifier (PGA) with a swiched capacitor offset compensation circuit is described. The mean compensation error is 130µV at the input, and the standard deviation of the compensation error is 50µV. This PGA is applicable to a baseband amplifier for digital radio communication terminals.

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.