In this paper some new results for analog hardware realization of secure communication system using chaos synchronization have been presented. In particular the effect of the use of transmission line as channel has been considered assuming practical implementation. The influence of the loss of transmission line and mismatching on synchronization has been investigated in chaotic systems based on the Pecora-Carroll concept. It has been shown that desynchronization due to loss can be checked by using an amplifier with appropriate gain. Moreover the bit error rate (BER) has been evaluated in a digital communication system based on the principle of chaotic masking.

In this paper, dependence of storage capacity of an analogue associative memory model using nonmonotonic neurons on static synaptic noise and static threshold noise is shown. This dependence is analytically calculated by means of the self-consistent signal-to-noise analysis (SCSNA) proposed by Shiino and Fukai. It is known that the storage capacity of an associative memory model can be improved markedly by replacing the usual sigmoid neurons with nonmonotonic ones, and the Hopfield model has theoretically been shown to be fairly robust against introducing the static synaptic noise. In this paper, it is shown that when the monotonicity of neuron is high, the storage capacity decreases rapidly according to an increase of the static synaptic noise. It is also shown that the reduction of the storage capacity is more sensitive to an increase in the static threshold noise than to the increase in the static synaptic noise.

To expand signal wavelength bandwidth in long-haul, large-capacity WDM transmission systems, we investigated gain-equalizers (GEQs) for Erbium doped fiber amplifiers (EDFAs). We applied GEQs using Mach-Zehnder type filters with two different free-spectral-ranges (FSRs) to accurately compensate for the EDFAs gain-wavelength characteristics. The 1st GEQ with a longer FSR was the main GEQ to compensate for the overall gain-wavelength characteristics, and the 2nd GEQ with a shorter FSR was the secondary GEQ to compensate for the resultant gain undulation after the 1st GEQ. The 2nd GEQ had low maximum loss and long period of equalization-spacing compared to the 1st GEQ. We designed that the FSR for the 1st GEQ was twice the signal wavelength bandwidth, and the FSR for the 2nd GEQ was two thirds of the signal wavelength bandwidth. To compensate for the asymmetry in the EDFAs gain-wavelength characteristics, we designed that the 2nd GEQ minimum-loss wavelength was shorter than the 1st GEQ maximum-loss wavelength. Using a circulating loop with a 21-EDFA chain, we confirmed the signal wavelength bandwidth expanded by the above GEQs. We also investigated the trade-off relationship between the signal wavelength bandwidth and the optical signal-to-noise ratio, as the parameter of the number of the 1st GEQ inserted in the EDFAs chain. The achieved signal wavelength bandwidth after 10,000-km transmission was 12 nm. We successfully transmitted 170 Gbit/s (325. 332 Gbit/s) WDM signals over 9,879 km employing high alumina codoped EDFAs and Mach-Zehnder type filters with long FSRs.

An optical communications technology roadmap leading up to the second decade of the 21st century has been investigated to provide a future vision of the optoelectronic technology in 15 to 20 years. The process whereby technology may progress toward the realization of the vision is indicated. A transmission rate of 100 Mbps for homes and a rate of 5 Tbps for the backbone network will be required in the first decade of the 21 century. Two technology roadmaps for public and business communications networks are discussed. It is concluded both WDM and TDM technology will be required to realize such an ultra-high capacity transmission. Technical tasks for various optical devices are investigated in detail.

The microwave attenuation, which is the key factor for realizing very large bandwidths Ti:LiNbO3 optical modulators is fully studied and the causes and reduction techniques are discussed in detail. Practical realization of wide-band optical modulators with low microwave attenuation and low driving voltage is also discussed.

This paper studies the routing algorithms for multi-destination connections where each destination may require different amount of data streams. This asymmetric feature can arise mostly in a large and/or heterogeneous network environment. There are mainly two reasons for this. One is that terminal equipments may have different capabilities. The other is that users may have various interests in the same set of information. We first define the asymmetric multicast problem and describe an original routing method for this type of multicast. The method is then employed in the presented routing algorithms, which can be run in multi-cluster environment. The multi-cluster architecture is considered to be effective for running routing in the networks, where a variety of operating methods might be applied in different clusters but global network performance is required. Our algorithms are designed based on some classical Steiner tree heuristics. The basic goal of our algorithms is to make routing decisions for the asymmetric multicast connections with minimum-cost purpose. In addition, we also consider delay constraint requirements in the multicast connections and propose correspondent algorithms. We compare the performance between SPT (Shortest Path Tree)-based algorithms and the presented algorithms by simulations. We show that performance difference exists among the different types of the algorithms.

An optimum filter for extracting a time-varying harmonic signal from the noise-corrupted measurement is proposed. It is derived as a solution of the least mean square estimation with consideration of the pitch estimation error even without any assumption on the filter model. We obtain a comb-like impulse response which consists of homologous and dilated distribution of weights just located periodically with a pitch interval. This remarkable structure is well suited to the proportionally expanding error of pitch repetition times. Examples of the filter design are presented, and the performance of noise suppression is examined by comparison with conventional comb filters.

By sacrificing approximately ten percent of the transmission speed, ultra-high speed optical time division multiplexed network can be fully operatable by the use of currently available electrical switches. The network utilizes dispersion managed quasi-solitons and transmits TDM packet which comprises of ATM cells that are introduced from a gateway through bit compression to match to the ultra-high speed traffics. The network can provide flexible bandwidth and bit on demand at burst rate of the maximum LAN speed.

Electrochemomechanical deformation (ECMD) of poly(o-methoxyaniline) (PoMAn) film has been studied in various acid solutions, such as Cl-, HSO4-, BF4-, and p-toluene sulfate. The magnitude of ECMD of the film depends linearly on the degree of oxidation of the film similarly to the case of polyaniline (PAn). 2. 53% of deformation ratios along the stretched direction are obtained for 30% of reduction. In contrast to that of PAn, however, the ECMDs of PoMAn do not markedly depend on the kind of anions. Transient responses of current and deformation are investigated by the potential application stepwise and the diffusion coefficient of ions in films. The results are discussed in terms of the effect of substituted methoxy group.

A communication system which attains an efficient amalgamation of base station (BS) type cellular communication and non-BS type direct communication for mobile terminals (MTs), "cellularad-hoc united communication system," is proposed. In this system, whether a cellular system or an ad-hoc communication system is chosen by distance and whether the condition is good or not between communicating MTs. In other words, when two terminals are relatively near each other and are in sufficient conditions to communicate directly, they select the ad-hoc communication, while for other cases they use the cellular system. The proposed system was confirmed to have effective channel usage and low battery consumption from the simulation results. It can be also said that this system is suited especially for MTs which tend to communicate with closer partners such as operational mobile robots and autonomous carrier vehicles.

This paper gives an overview of Turbo codes principles, performance, and design issues for practical application. As fundamentals of Turbo codes, encoder structure, interleaver, and iterative decoding are explained. The performance is analyzed through their weight distribution, and the analysis gives code design rules for component codes. Practical decoding algorithms are presented in addition to MAP algorithm. Design issues are discussed for mobile communications as an example of practical application. Finally, research trends are briefly mentioned.

Electron and hole transport in polymethylphenylsilane (PMPS) containing anthracene units in the polymer backbone (PMPS-AN) has been studied by time-of-flight and electrophotographic measurements. It is found that the hole transport of PMPS-AN is non-dispersive and exhibits thermally activated behavior. The anthracene incorporation to the polymer backbone of PMPS slightly decreases the hole drift mobility of PMPS-AN because of the increase in energetic disorder. In PMPS-AN, the electron transport, which has not been observed in organic polysilanes, is clearly seen. In contrast to the hole transport, the electron transport exhibits anomalous dispersion of the transit times and the electron drift mobility is independent of temperature. It is suggested that the electron transport is due to geometrical disorder of electron hopping sites (anthracene units). From the electrophotographic measurements, we discuss the applicability of PMPS-AN to photoreceptors and estimate the Schubweg of electrons in PMPS-AN.

Wideband wireless access based on direct sequence code division multiple access, called coherent multi-rate W-CDMA in this paper, designed for next generation mobile communications systems is introduced. It employs inter-cell asynchronous operation with a fast cell search algorithm, orthogonal multi-spreading factor (SF) forward links, and pilot symbol assisted coherent reverse and forward links. Inter-cell asynchronous cell site operation facilitates the continuous deployment of the system from outdoors to indoors. An orthogonal multi-SF forward link allows flexible offering of different multi-rate services to users without losing orthogonality. Gains in the radio link capacity and coverage are obtained from the use of coherent Rake combining and fast transmit power control (TPC) in both forward and reverse links. Computer simulation and field experiment results of the coherent multi-rate W-CDMA radio link performance are presented. Also presented are interference cancellation and adaptive antenna array techniques that can significantly improve the link capacity and coverage.

Future satellite communication systems will be developed at Ka-band (20/30 GHz) owing to the relatively wide frequency allocation and current freedom from terrestrial interference for multimedia services. A serious disadvantage of the Ka-band, however, is the very high atmospheric attenuation in rainy weather. Quasi-synchronous CDMA drastically reduces the effect of self-noise with several interesting features of CDMA for mobile communications such as flexible frequency reuse, the capability of performing soft-handover and a lower sensitivity to interference. This paper evaluates the performance of a quasi-synchronous CDMA return link for a Ka-band geostationary satellite communication system. For a fixed satellite channel whose characteristics depend on weather conditions, the signal envelope and phase for this channel is modeled as Gaussian. The bit error and outage probability, and the detection loss due to imperfect chip timing synchronization is analytically evaluated and the system capacity degradation due to the weather condition is estimated. Two cases of general and worst conditions are evaluated, in which i) rain attenuation ii) nonlinearity of transponder are considered. The two cases consist of the general case in which all users are affected by rainy weather, and the worst case in which only the user of interest, not multiple access interferers, is affected by rain attenuation. The results for the two cases of rainy weather clearly show that quasi-synchronous CDMA eases the power control requirements and has less sensitivity to imperfect power control. When dealing with the impact of the satellite transponder nonlinearity in addition to the rain attenuation, the shift of optimum amplifier operating point is shown so that [Eb/N0]sat, defined as the sum of the Eb/N0 value required to obtain a BER equal to Pb at a given output backoff (OBO) and the value of the OBO itself, tends to decrease, and higher BER impairment is given, since the rain attenuation results in the same effect as the additive input backoff (IBO) at the satellite transponder input. As the BER increases, the optimum [Eb/N0]sat and IBO decrease that result in the shift of optimum operating point.

Multicolor light emitting diodes (LEDs) which emit red (R), green (G) and blue (B) light have been realized by stacking a two-color emission part on a single-color emission part. The former part consists of two emissive layers of red and blue light, which can be selected by changing the polarity of applied field. The latter part consists of a single-color emission part which emits green light. The emission from the diode in the whole visible spectral range can be modulated by the combination of applying various voltages to the two-color and to the single-color emission parts, separately.

A RAKE combiner based on a matched filter (MF) can be relatively easily implemented since the despread signal components that have propagated along different paths appear sequentially at the MF output. An important design problem is how to accurately select the paths having sufficiently large signal-to-noise power ratios (SNRs). This paper proposes a simple path selection algorithm that uses two selection thresholds. The first threshold is to select the paths that provide largest SNRs. However, as the total received signal power (sum of the signal powers of all paths) decreases, some of the selected paths become noisy. Therefore, we introduce a second threshold that discards the noisy or noise-only paths from among those selected by the first threshold. We apply the proposed path selection algorithm to a pilot symbol-assisted coherent RAKE combiner and find by computer simulations a near optimum set of the two thresholds in frequency selective multipath Rayleigh fading channels. Several power delay profile shapes are considered. The simulation results demonstrate that the MF-based RAKE combiner with the two selection thresholds can achieve a bit-error-rate (BER) performance close to the ideal case (i. e. , the paths to be used for RAKE combining are selected for each power delay profile such that the required signal energy per information bit-to-noise spectrum density ratio (Eb/N0) is minimized).

MTDMA (Multimedia, Multimode TDMA) system has been developed for the 3rd generation mobile communications. An adaptive modulation technique is employed, which select 16 QAM or QPSK modulations fit for the O (Indoor Office)/P (Outdoor to Indoor and Pedestrian) communication environments. The maximum user rate of 4 Mbps is realized. Basic specification is described for O, P and V environments.

In order to improve the running durability of organic electroluminescent devices (OELDs), the doping sites of molecular OELDs were optimized, and the frequency responses of the optimized devices were examined for Mg-In/bis (10-hydroxybenzo[h]quinolinate) beryllium (BeBq2)/N, N'-diphenyl-N, N'-(3-methylphenyl)-1, 1'-biphenyl-4, 4'-diamine (TPD)/4, 4', 4"-tris (3-methylphenylphenylamino) triphenylamine (MTDATA)/ITO. The TPD hole transport layer was the optimum doping site for 5, 6, 11, 12-tetraphenylnaphthacene (rubrene) dopant, and a very high efficiency of 13 cd/A at 0. 13 kcd/m2 was obtained for yellow emission. Half-decay times under a constant direct current density of 1. 0 mA/cm2 from an initial luminance of 0. 13 kcd/m2 extended to longer than 26,000 hours. The luminance of the optimized device decreases lineally with respect to the logarithm of the frequency as the frequency increases in the range from 1 kHz to 0. 3 MHz when a square wave with a duty ratio of 50% and a maximum voltage of 5.0 V is applied. A new driving method involving frequency modulation is proposed. This may offer accurate control of pixel luminance, and enable simple driving circuits adapted to highly integrated digital LSI chips, or the concept of system on glass.

Personal communication systems are increasingly required to accommodate not only voice traffic, but also various types of data traffic. Generally speaking, voice traffic is symmetric between uplink and downlink, while data traffic can be highly asymmetric. It is therefore inefficient to accommodate data in a conventional TDMA/TDD system with fixed TDD boundary. In this paper, focusing on the continuous data traffic which requires multi-slots in a circuit based TDMA/TDD system, an algorithm is proposed in which the TDD boundary are moved adaptively to accommodate data traffic efficiently. Comparing with the boundary-fixed conventional algorithm, computer simulations confirm that the proposed algorithm has superior performance in the excessive transmission delay of data while maintaining the performance of voice. The intercell interference between mobiles due to different TDD boundaries is also confirmed to be negligible. Moreover, almost the similar performance improvements of the proposed algorithm are confirmed for two different average message sizes of data calls.

Recent technologies of organic film devices are reviewed. New technologies of fabrication and characterization of organic thin films, electro-mechanical conversion materials, and applications for electrical and optical devices are discussed. In this review paper, especially organic light emitting diodes, tunneling junctions using polyimide Langmuir-Blodgett films, tunneling spectroscopy and high-density recording, plastic actuators using conducting polymers, molecular self-assembly process for fabricating organic thin film devices are reviewed.