Chaos shift keying (CSK) is a modulation method in digital communication systems using chaotically modulated signals. This paper proposes novel CSK which utilizes two types of chaotic synchronization called in-phase and anti-phase chaotic synchronization. In this method, binary signals are mapped into two phases of chaotic synchronization, and a transmitter generates a two-phase-shift-keyed chaotic signal. So it will be called chaotic phase shift keying (CPSK) in this paper. This method is simpler than that based on two pairs of different chaotic systems. We also discuss an effect of noise in transmission lines.

The dipole-dipole interaction in the quantum mechanical treatment of the matter-radiation dynamics, is shown to give rise to split energy levels reminiscent of the nonlinear coupled spectral features as well as a self-sustained coherent modes. Wiener's theory of nonlinear random processes is applied to the second harmonic generation (SHG), leading also to coupled spectral pulling and dipping features, due to the dual noise sources in the fundamental and the harmonic polarizations. Furthermore, the nonlinear spectral features are suggested to be applied to implement quantum (qubit) gates for computation.

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.

The Guaranteed Bandwidth Protocol (GBW) is an access scheme being proposed for implementation of connection oriented services in DQDB networks. Connection oriented services are expected to handle both constant bit rate (CBR) and variable bit rate (VBR) traffic that have delay and jitter constraints. It has been reported that the GBW protocol can provide guaranteed bandwidth and lower delays compared to the ordinary DQDB protocol. However, the intensity of the jitter introduced by this scheme has not been made clear. This paper compares the jitter results for the GBW scheme to those obtained by a new access method called Modified Guaranteed Bandwidth (MOD_GBW) protocol, which is proposed here. It is shown through simulation that MOD_GBW also provides guaranteed bandwidth and that its delay and jitter characteristics are significantly better than those of the GBW protocol. In the simulation model, the DQDB stations are divided into two groups: 1)Real-Time (RT) stations that generate either CBR or VBR real-time traffic; and 2)Data stations that generate memoryless type of traffic. Data stations operate according to the ordinary DQDB protocol only. The main performance measure adopted here for the real-time traffic is the interdeparture time distribution of consecutive segments from an RT-station. We define the variance of this distribution as jitter. This paper also shows the impact of GBW/MOD_GBW on the performance of the data stations by evaluating their throughput and average bus access delay. Finally, we show that the network performance is weakly related to the number of RT-stations under MOD_GBW, but it depends strongly on the overall loading.

This paper presents an overview of research activities in Japan in the field of very low bit-rate video coding. Related research based on the concept of "intelligent image coding" started in the mid-1980's. Although this concept originated from the consideration of a new type of image coding, it can also be applied to other interesting applications such as human interface and psychology. On the other hand, since the beginning of the 1990's, research on the improvement of waveform coding has been actively performed to realize very low bit-rate video coding. Key techniques employed here are improvement of motion compensation and adoption of region segmentation. In addition to the above, we propose new concepts of image coding, which have the potential to open up new aspects of image coding, e.g., ideas of interactive image coding, integrated 3-D visual communication and coding of multimedia information considering mutual relationship amongst various media.

This paper presents a configuration of circularly polarized annular-ring microstrip antenna (ARMSA) and its design method to obtain high gain and low axial ratio including the analysis of finite ground plane effect using G.T.D. for personal satellite communication use. The ARMSA excited at TM21 mode through co-planar branch-line hybrid coupler for circular polarization produces a conical pattern which has high gain in low elevation angle. The relation of gain and axial ratio versus the dielectric constant of substrate are shown and the existence of the dielectric constant which satisfies two requirements, that is, high gain and low axial ratio are clarified. For car-top application, experimental results in the L-band showed satisfactory characteristics for vehicle antenna.

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.

For mobile/personal satellite systems, an ARQ protocol with low transmitter/receiver complexity as well as high throughput performance in a long Round-Trip-Delay (RTD) and even in a bad channel condition is required. In this paper, a new Selective-Repeat (SR) ARQ with multicopy retransmission is proposed and a performance on an AWGN channel is analyzed. The proposed scheme can be viewed as a modified version for SR + Stutter (ST) Scheme 2 [6]. The basic idea of the strategy is to repeat only erroneous blocks stored in the vN block transmitter buffer multiple times, when v consecutive retransmissions in SR mode are received in error, where N denotes RTD in blocks. Numerical analysis and simuration results in the case of N block transmitter/receiver buffer show that the proposed scheme presents better performance than SR + ST scheme 2 of 2N block buffer, especially that the robustness in the high BER region is remarkable.

In this study, we analyze the system which simultaneously transmits spread-spectrum signals with different processing gains. The main purpose of this study is to give an analytical framework that describes the influence of the interfering signals with different processing gains. For this purpose, we define a crosscorrelation function between the spreading sequences with different code lengths, and discuss the effects of interaction between the signals. As the results, we show that the power of the interference component after despreading procedure, the power ratio of the desired to undesired components, and thus the bit error rate are not constant but vary symbol by symbol.

For indoor wireless communication systems, transceivers need to be placed strategically to achieve optimum communication coverage area at the lowest cost. Unfortunately the coverage region for a transceiver depends heavily on the type of building and on the placement of walls within the building. This paper proposed a slab model to simulate the wave transmission in the wall and employed this simple path loss model to predict the coverage region. This method prevents the complicated computation of wave propagation, so it could predict the coverage area real time. Numerical results show predicted path loss date are well agreed with the measurement ones.

In this paper we will propose a deterministic approach to model the radio wave propagation channels in large empty buildings. This technique applies the modified SBR method to find equivalent sources (images) in each launched triangular ray tube, and sums the receiving amplitude contributed by all images coherently. In addition, vector effective antenna height (VEH) is introduced to consider the polarization coupling effect resulting from the multiple reflection inside the buildings. We verify this approach by comparing the numerical results in three canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high frequency radio propagation inside buildings where multiple reflection is dominant. Work reported in this paper has shown that propagation loss in large empty buildings can vary considerably according to the geometrical configurations of buildings and polarizations. This SBR/image method can be enhanced by including the wall penetration and wedge diffraction effects so that more complicated indoor environments with furniture will be handled. Additional considerations, such as buildings crowded with pedestrians are left for future studies.

A binary counter circuit in the extended phase-mode logic (EPL) family is presented. The EPL family utilizes a single flux quantum as an information bit carrier. Numerical simulations show that a binary counter circuit with a Josephson critical current density of 1 kA/cm2 can operate up to a 30 GHz input signal. The circuit has been fabricated using Nb/AlOx/Nb Josephson junction technology. New interface circuits are employed in the fabricated chip. A low speed test result shows the correct operation of the binary counter.

The performance of an M-ary spread-spectrum multiple-access (M-ary/SSMA) scheme in the presence of carrier frequency offset is discussed in this paper. The influence of carrier frequency offset on the non-coherent reception of M-ary/SSMA signals is examined and it is shown that the carrier frequency offset degrades the performance remarkably, yet. this influence has a distinctive property. Making use of this property, we propose a new M-ary/SSMA scheme that can mitigate the influence of the carrier frequency offset. The scheme is based on the assignment of two distinctive Hadamard codes to in-phase and quadrature components of the transmitted signal. The effect of simultaneous transmission is evaluated in terms of bit-error-rate performance with the carrier frequency offset. As the result, it is observed that the satisfactory bit-error-rate performance can be achieved in the presence of carrier frequendy offset.

The problem of test generation for VLSI circuits computationally requires prohibitive costs. Parallel processing on a multiprocessor system is one of available methods in order to speedup the process for such time-consuming problems. In this paper, we analyze the performance of parallel test generation for combinational circuits. We present two types of parallel test generation systems in which the communication methods are different; vector broadcasting (VB) and fault broadcasting (FB) systems, and analyze the number of generated test vectors, the costs of test vector generation, fault simulation and communication, and the speedup of these parallel test generation systems, where the two types of communication factors; the communication cut-off factor and the communication period, are applied. We also present experimental results on the VB and FB systems implemented on a network of workstations using ISCAS'85 and ISCAS'89 benchmark circuits. The analytical and experimental results show that the total number of test vectors generated in the VB system is the same as that in the FB system, the speedup of the FB system is larger than that of the VB, and it is effective in reducing the communication cost to switch broadcasted data from vectors to faults.

Personal communication systems (PCS) have more signalling traffic than conventional fixed networks and require large-scale databases to manage users' profiles, which are sets of data items, such as the location the user is currently visiting and the user's authentication key, necessary for a PCS user to be provided with PCS services. This paper focuses on inter-network roaming in PCS environments. In designing a PCS supporting roaming service, it is essential to avoid increased signalling traffic and data searching time in the database. We first identify the appropriate domains for three routing schemes-Direction Routing, Redirection Routing, and Look-ahead Routing-from the viewpoints of the number of signals for inter-network roaming and roaming probability. We do this for two kinds of PCS database network architecture, Home Location Register (HLR) and Visitor Location Register (VLR), and show that Look-ahead Routing is the best scheme for the HLR network architecture (considering the number of signals for intra-network and inter-network database access) and that in the VLR network architecture, the decreasing of the roaming probability expands domains for which Redirection Routing is appropriate. We also propose a generic PCS data model that inter-network roaming interfaces can use to search effectively for a user's profile. The data model clarifies the contents of a set of data items which share certain characteristics, data items that the contents compose, and the relationships (data structures) between sets of data items. The model is based on the X. 500 series recommendations, which are applied for an Intelligent Network. We also propose a data structure between sets of data items using the directory information tree and show the ASN. 1 notations of the data model.

Introducing a mathematical model of image noise, we formalize the problem of fitting a conic to point data as statistical estimation. It is shown that the reliability of the fitted conic can be evaluated quantitatively in the form of the covariance tensor. We present a numerical scheme called renormalization for computing an optimal fit and at the same time evaluating its reliability. We also present a scheme for visualizing the reliability of the fit by means of the primary deviation pair. Our method is illustrated by showing simulations and real-image examples.

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.

Recently, there have been intensive studies on protocol methods and applications of short range inter-vehicle communication network (SR-IVCN) and systems. The purpose of the studies is to improve the safety of road traffic systems and the smooth control of the traffic flow by providing information to vehicles. Spread spectrum (SS) communication systems are able to simultaneously communicate and measure the distance between the terminals, thus it is advantageous to apply the spread spectrum technique to inter-vehicle communications. This paper assumes that the vehicles incidentally close to each other, form and manage a locally autonomous decentralized dynamic network. An R-ALOHA (Reservation-ALOHA) protocol for the spread spectrum inter-vehicle communication network using head spacing information is proposed which improve the conventional slot reservation methods. Since the near-far problem in SS communication is one reason for the degradation of system performance, this proposed scheme is shown to improve the efficiency of communication. The performance of the proposed system in the environment where the vehicles are assumed to run freely on a highway is verified by computer simulation. It is shown that inter-vehicle communication can be smoothly carried out between one vehicle and the surrounding vehicles using the propose method.

A pilot symbol-assisted coherent multistage interference canceller (PSA-COMSIC) using recursive channel estimation is proposed for DS-CDMA mobile radio cellular systems. In the proposed scheme, since the channel variation due to fading is recursively estimated at each interference canceling stage, the accuracy of channel estimation is successively improved. The bit error rate (BER) performances against average Eb/N0 (signal energy per bit-to-noise power spectral density ratio) and capacity in the isolated cell are investigated by computer simulations. The simulations demonstrate that the capacity using the PSA-COMSIC with recursive channel estimation is about 1.6 times higher than that of the conventional matched filter receiver with channel coding and bit-interleaving in the interference-limited environments.

The evolution of access networks towards Fiber-To-The-Home (FTTH) receives much attention throughout the world because FTTH has a big potential for providing future attractive services. To provide such services in terms of transmission rate, the cable network transition scenario from conventional copper cable network to optical fiber cable one in access field should be clarified. Since network transition scenario deeply depends on the service evolution scenarios (what type of service would appear at a certain time and how many customers move to the other services, for example), this paper firstly categorizes telecommunication services into four kinds of services, i.e. Basic Service (e.g. POTS), Narrowband Symmetrical Service (e.g. NISDN), Broadband Asymmetrical Services (e.g. Video-On-Demand) and Broadband Symmetrical Services (e.g. BISDN) in terms of up-and down-stream transmission rates. Based on this service categorization, it is proposed to formalize service evolution scenarios by a transition pattern of the initial demands and the penetration rates of these services. Then, the evaluation method of network transition scenarios is also proposed in terms of NPV by the service evolution scenarios. It is conclude that the network transition scenarios are deeply related to the amount and behavior of the demands moving to the other services as follows.-The scenario where the new system configuration partly replaces the old one whenever the demands appear for providing higher transmission rate services is applicable, when the demands move little or constantly move to the higher transmission rate services,-The scenario where the new system configuration totally replaces the old one at the early stage for providing all services is applicable, when the demands drastically move to the higher transmission rate services during short period.