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.

This paper describes the recently developed 816 delivery and coupling switch (DC-switch) boards for constructing a 320-Gb/s throughput (2. 5 Gb/s 8 multiplexed wavelengths 16 incoming/outgoing link pairs) optical path cross-connect (OPXC) system based on wavelength path (WP) and virtual wavelength path (VWP) schemes. The DC-switch-based OPXC system, compared with conventional space division switch (SD-switch)-based OPXC system architecture, is shown to be superior in terms of; i) high link modularity, ii) upgradability from WP network to VWP network, iii) better transmission characteristics, and iv) lower total switching power consumption. Therefore, the DC-switch-based OPXC system can realize cost-effective optical path networks. The developed DC-switches exploit the silica-based planar lightwave circuit (PLC) technologies, and DC-switch board size is 300330 mm2 (one switch). The worst values of the insertion loss of the board, ON/OFF ratio, and polarization dependent loss are 14. 5 dB, 34 dB and 0. 5 dB, respectively. Moreover, even though switching is realized by thermo-optic effects, the optical output level varies by only 0. 7 dB and 0. 8 dB for ON- and OFF-state signals, respectively, when the environmental temperature is varied from 5 to 65 .

For Cable-To-The-Air network providing a seamless access network in both indoor and outdoor, direct optical switching CDMA scheme is newly proposed to multiplex any types of radio signals. In two types of connection methods, optical switch connection and optical coupler connection systems, the received carrier-to-interference-plus-noise power ratios are theoretically analyzed. It is clarified that in the optical switch connection connection system, by introducing the additional optical gain at each radio base station, the carrier-to-interference-plus-noise power ratios for all radio base stations and the connected number of radio base stations can be improved compared with the OC connection system.

We demonstrate that the frequency modulated video signals in the subcarrier multiple access optical network can be satisfactorily transmitted using our proposed method, that broadens an optical spectrum by multiplying the subcarrier signals by an additional signal and that reduces optical beat interference, even if the wavelengths of four Fabry-Perot laser diodes are very close each other.

The TMN that appears to operate the various communication networks generally and efficiently is developed under the different platform environment such as the different hardware and the different operating system. One of the main problems is that all the agents of the TMN system must be duplicated and maintain the software and the data blocks that perform the identical function. Therefore, the standard of the Q3 interface development cannot be defined and the multi-platform cannot be supported in the development of the TMN agent. In order to overcome these problems, the Farming methodology that is based on the Farmer model has been suggested. The main concept of the Farming methodology is that the software and the data components that are duplicated and stored in each distributed object are saved in the Platform Independent Class Repository (PICR) by converting into the format of the independent componentware in the platform, so that the componentwares that are essential for the execution can be loaded and used statically or dynamically from PICR as described in the framework of each distributed object. The distributed TMN agent of the personal communication network is designed and developed by using the Farmer model.

This paper presents some fundamental properties of multiple-valued logic functions monotonic in a partial-ordering relation which is introduced in the set of truth values and does not necessarily have the greatest or least element. Two kinds of necessary and sufficient conditions for monotonic p-valued functions are given with the proofs. Their logic formulas using unary operators defined in the partial-ordering relation and a simplification method for those logic formulas are also given. These results include as their special cases our former results for p-valued functions monotonic in the ambiguity relation which is a partial-ordering relation with the greatest element.

A power amplifier employing a novel linearizing technique is proposed and is applied to digital mobile communication systems. The amplifier offers both high efficiency and excellent adjacent-channel power leakage (ACP) characteristics. The power added efficiency (PAE) of the proposed amplifier is 51% with an ACP of 45 dBc, which is the PDC standard (one of the Japanese mobile communication systems standards). This amplifier can be applied to various systems merely by changing the ROM data.

Highly miniaturization technology in front-end GaAs Hybrid IC for mobile communication equipment will be presented. A combination of MBB (micro bump bonding) technology and the new GaAs IC fabrication process using high dielectric constant (εr) thin film technology has achieved a super small HIC with low cost and low power consumption. The new HIC was constructed of only a ceramic substrate in which the spiral inductors were formed on it and the GaAs IC chip that was bonded by using MBB technology. The MBB technology lead the HIC to a lower temperature process without soldering, a smaller bump diameter, at shorter intervals and the lowest parasitic in the bump. The advantage of the small bonding pad of the IC contributes to miniaturize the IC chip and reduces the chip cost. The GaAs IC process technology using high-εr thin film achieves the integration of all capacitors in the IC without increasing the chip size. Furthermore, low power consumption was achieved by 0. 5-µm LDD BP-MESFET with a high k-value. Although capacitors were integrated on the IC, all of the inductors were formed on the top of the ceramic substrate using a thin film metal process. This was used due to its large occupation area when it was integrated on the IC, and produced a low Q-factor. As a results, the chip was minimized to a size of 0. 81. 0 mm2 and achieved a low-cost chip. Two types of HICs were fabricated for 880 MHz cellular band and 1. 9 GHz PHS (Personal Handy phone System) band. The HIC at 880 MHz measures only 5. 05. 01. 0 mm3, and offered a conversion gain of 25 dB, a noise figure of 4. 2 dB and an image rejection ratio of 12 dB at 2. 7 V and at a power supply of 3. 5 mA. The HIC for 1. 9 GHz measures only 3. 54. 01. 0 mm3, and showed a conversion gain of 16. 0 dB, a II P3 of -16. 0 dBm, and an image rejection ratio of over 20 dBc at 3. 0 V and at power supply of 4. 5 mA.

For people with serious disability, it is most significant to be able to use the same communication methods, for instance a telephone and an electronic mail system (e-mail), as ordinary people do in order to get a normal life and communicate with other people for leading a social life. In particular, having communications access to an e-mail is a very effective method of communication that enables them to convey their intention to other people directly while at the same time keep their privacy. However, it takes them much time and effort to input an e-mail text on the computer. They also need much support by their attendants. From this point of view, we propose a multi-modal communication system that is composed of a voice recognizer, a pointing device, and a text composer. This system intend to improve the man-machine interface for people with physical disability. In this system, our voice recognition technology plays a key role in providing a good interface between disabled people and the personal computer. When generating e-mail contents, users access the database containing user keywords, and the guidance menu from which they select the appropriate word by voice. Our experimental results suggest that this communication system improves not only the time efficiency of text composition but also the readiness of disabled people to communicate with other people. In addition, our disabled subject on this paper is not able to move his body, legs and hands due to suffer from muscular dystrophy. And he is able to move only his fingers and speak command words with the assistance of a respirator.

Multi-recast techniques make it possible for a voter to participate in a sequence of different designated votings by using only one ticket. In a multi-recastable ticket scheme for electronic voting, every voter of a group can obtain an m-castable ticket (m-ticket), and through the m-ticket, the voter can participate in a sequence of m different designated votings held in this group. The m-ticket contains all possible intentions of the voter in the sequence of votings, and in each of the m votings, a voter casts his vote by just making appropriate modifications to his m-ticket. The authority cannot produce both the opposite version of a vote cast by a voter in one voting and the succeeding uncast votes of the voter. Only one round of registration action is required for a voter to request an m-ticket from the authority. Moreover, the size of such an m-ticket is not larger than that of an ordinary vote. It turns out that the proposed scheme greatly reduces the network traffic between the voters and the authority during the registration stages in a sequence of different votings, for example, the proposed method reduces the communication traffic by almost 80% for a sequence of 5 votings and by nearly 90% for a sequence of 10 votings.

To further increase the capacity of the DS-CDMA reverse-link, this paper investigates the effectiveness of interference rejection weight control (IRWC) for the pilot symbol-assisted coherent multistage interference canceller (PSA-COMSIC) using recursive channel estimation (RCE). First, a bit error rate (BER) expression of the serial (successive) and parallel type hard decision multistage interference canceller (MSIC) with IRWC using Gaussian approximation for multiple access interference (MAI) are presented for no fading channels. It is theoretically shown that IRWC is effective in mitigating the interference replica generation error in hard decision MSIC. Next, the BER performance of PSA-COMSIC using IRWC in a multipath Rayleigh fading channel when channel coding is applied is evaluated by computer simulations. The BER performance and capacity are evaluated not only for the conventional serial and parallel types but also for serial/parallel (S/P) hybrid type and non-linear/linear (N/L) hybrid type schemes, both of which are effective in significantly reducing the demodulation processing delay. The simulation results demonstrate that, in interference-limited channels where the back ground noise is negligible, the capacity of serial type PSA-COMSIC using IRWC is about 10% higher than that without IRWC. It is also found that if we can accept a slight capacity degradation compared to the serial type PSA-COMSIC, S/P hybrid schemes are effective in reducing the demodulation processing delay.

In a secure partially blind signature scheme, the signer assures that the blind signatures issued by him contains the information he desires. The techniques make it possible to minimize the unlimited growth of the bank's database which storing all spent electronic cash in an anonymous electronic cash system. In this paper we propose an efficient partially blind signature scheme for electronic cash. In our scheme, only several modular additions and modular multiplications are required for a signature requester to obtain and verify a signature. It turns out that the proposed scheme is suitable for mobile clients and smart-card applications because no time-consuming computations are required, such as modular exponentiation and inverse computations. Comparing with the existing blind signature schemes proposed in the literatures, our method reduces the amount of computations for signature requesters by almost 98%.

Multimedia communications often require intramedia synchronization for video data to prevent potential playout discontinuity while still retaining satisfactory playout throughput. In this paper, we propose a novel intra-video synchronization mechanism, called the Video Smoother, particularly suitable for low-end multimedia applications, such as video conferencing. Generally, the Video Smoother dynamically adopts various playout rates according to the number of frames in the playout buffer in an attempt to compensate for the delay jitter introduced from networks. In essence, if the number of frames in the buffer exceeds a given threshold (TH), the Smoother employs a maximum playout rate. Otherwise, the Smoother employs linearly or exponentially reduced rates to eliminate playout pauses resulting from the emptiness of the playout buffer. To determine optimal THs achieving a minimum of playout discontinuity and a maximum of playout throughput under various bursty traffic, we propose an analytic model assuming incoming traffic following an Interrupted Bernoulli arrival Process (IBP). As a result, optimal THs can be analytically determined resulting in superior playout quality under various arrivals and loads of networks. Finally, we display simulation results which demonstrate that, compared to the playout without intra-video synchronization (instant playout), the Video Smoother achieves superior smooth playout and compatible throughput.

Co-channel interference is a major deteriorating factor limiting the capacity of mobile communication systems. To mitigate the effect of the interference, a kind of nonlinear interference canceller named trellis-coded co-channel interference canceller (TCC) has been proposed. In TCC the trellis-coded modulation (TCM) is introduced to both the desired signal and the interference signal in order to enhance the cancelling performance. In this paper, the bit error rate (BER) performance of TCC in static channel is theoretically evaluated for the first time. An equivalent TCM (E-TCM) model is firstly established, and a BER asymptotic estimate (AE) and a BER upper bound (UB) of TCC are then evaluated respectively by analyzing E-TCM. In the evaluation of AE, the BER performance is calculated as a function of phase difference between the desired signal and the interference signal (φ), subsequently the average BER performance over φ can be evaluated. The UB of BER is calculated using a transfer function based on the matrix representation. This paper also demonstrates that AE gives higher accuracy and less calculation complexity than UB. Performance comparisons reveal the consistency of these theoretical results with that of computer simulations.

In this paper, Wavelength Division Multiple access (WDM) ring is proposed for interconnection in workstation clusters or parallel machines. This network consists of ring connected routers each of which selectively passes signals addressed in some particular wavelengths. Other wavelengths are once converted to electric signals, and re-transmitted being addressed in different wavelengths. Wavelengths are assigned to divisors of the number of nodes in the system. Using the regular WDM ring with imaginary nodes, the diameter and average distance are reduced even if the number of nodes has few divisors. It provides better diameter and average distance than that of the uni-directional torus. Although the diameter and average distance is worse than that of ShuffleNet, the physical structure of the WDM ring is simple and the available number of nodes is flexible.

In this paper, we propose a technique to synthesize a hardware circuit from a protocol specification consisting of several concurrent EFSMs with multi-rendezvous specified among their subsets. In our class, each multi-rendezvous can be specified among more than two EFSMs, and several multi-rendezvous can be specified for different combinations of EFSMs. In the proposed technique, using the information such as current states of EFSMs, input values at external gates and guard expressions, we compose a circuit to evaluate whether each multi-rendezvous can be executed. If several exclusive multi-rendezvous get executable simultaneously for some combinations of EFSMs, we select one of them according to the priority order given in advance. We compose such a circuit as a combinational logic circuit so that it works fast. By applying our technique to Abracadabra protocol specified in LOTOS, it is confirmed that the derived circuit handles multi-rendezvous efficiently.

Despite the fact that the necessity of FDT (formal description techniques) had been emphasized, many approaches to verifying feature interactions were insufficient. This paper proposes formal definitions for feature interactions which can occur when telecommunication services specified independently are operated in parallel. Seven types of feature interactions are defined formally.

In a distributed concurrent system such as a computer communication network, the system components communicate with each other via communication links in order to accomplish a desired distributed application. If the links are dynamically established among the components, the system configuration as well as its behavior becomes complex. In this paper, we give formal specification of such a dynamically reconfigurable system in which the components are modeled by communicating finite state machines executed concurrently with the communication links which are dynamically established and disconnected. We also present an algorithm to validate the safety and link-related properties in the specified behavior. Finally, we design and implement a simulator and a validator that enables execution and validation of the given specification, respectively.

Verification of responsive communication protocols is to determine whether they can recover to a normal state within a predetermined time, even when they enter an abnormal state due to any fault. In this paper, we propose a new verification method for responsive communication protocols using virtual system states, each of which represents several system states. Next, in order to evaluate the effectiveness of the new method, we develop a verification tool based on the proposed method. Then we apply the tool to a broadcasting protocol and measure several metrics on the tool. The experimental results show that (1) the number of system states, (2) the amount of memory used by the tool, and (3) the execution time of the tool, can be drastically reduced.

A system combining multicarrier modulation and adaptive modulation in which a suitable level of quadrature amplitude modulation (QAM) is selected for each subcarrier and time-slot, is proposed for high-bit-rate and high-quality digital land mobile communications. The advantages of the system are a mode in which information cannot be transmitted under adverse propagation conditions and a buffer memory to limit a transmission delay time. If the allowable delay time is small, such as in voice and video transmissions, the system tends to have a poor bit error rate (BER) because of the forcible QAM-level selection. Our new selection scheme improves the BER for small transmission delay time. Suitable distribution of the delay time among subcarriers is obtained by using the scheme where the QAM-level of each subcarrier is chosen collectively using the number of data bits stored in memory. Computer simulation of the systems BER performance showed that the system could provide a noticeable BER improvement over frequency-selective fading channels as well as flat Rayleigh fading channels. The QAM-level selection scheme was also effective for a low maximum Doppler frequency and a small memory size. The system could thus attain about 25-fold improvement in BER at Es/N030 dB compared to the multicarrier/16QAM system. It also attained about 60-fold and 3. 5-fold improvement in BER at fd=10Hz compared with the system with multicarrier/16QAM and without the QAM-level selection scheme, respectively.