In this paper, we propose an efficient method (called DIRIC algorithm) to allocate carrier frequencies so as to minimize intermodulation products in two-level SCPC systems in which Hub station and many Remote stations communicate each other through satellite transponder. We also present a very efficient method to evaluate intermodulation products with substantially reduced CPU time in two-level SCPC systems. We compare and analyze the performance of several frequency allocation methods to extend DELINS-INSDEL algorithm (which is proposed by Okinaka) to two-level SCPC systems. When the proposed algorithm is applied to systems with modulated carrier, it is verified that this algorithm has the same efficiency as the unmodulated carrier. It is also shown heuristically that certain initial assignment algorithms perform better than random assignment.

In this paper, we demonstrate how Yamakawa's chaotic chips and Chua's circuits can be used to implement a secure communication system. Furthermore, their performance for the secure communication is discussed.

A scalable and flexible ASIC CIM system distributed on UNIX workstations, ORCHARD , has been developed. It is designed from three viewpoints: (1) cost and TAT reduction in system construction, (2) flexibility in data management for quality control, and (3) precise and quick scheduling and effective lot tracking to control TAT for each lot. The concept of a "virtual machine" is introduced to connect equipment having various protocols to a host system. The virtual machine is automatically generated at an average automatic generation ratio of as high as 89%, which leads to a reduction in cost and TAT in system construction. Data for quality control is managed by changing flexibly the "data processing recipe." This recipe defines screen format, data collected from equipment, and data transfered from various databases. Precise scheduling of lots with various levels of priority is achieved by introducing a priority evaluation function, thereby reducing scheduling time to 1/20 that for manual scheduling.

This paper describes an efficient slew rate enhancement technique especially suitable for an operational amplifier used in an LCD driver IC. This technique employs an input-dependent biasing without directly monitoring an input; instead, monitoring an output of the first stage of the amplifier. This enhancement technique is easily applied to a conventional two-stage operational amplifier and requires only 8 additional transistors to increase slew rates for both rising and falling edges. The bias currents of the first and the second stages are simultaneously controlled by this biasing. Experimental operational amplifiers with and without this enhancement have been fabricated to demonstrate the improvement of slew rate. Slew rates of 12.5V/µsec for the rising edge and 50V/µsec for the falling edge with a 100 pF load capacitance have been achieved by this technique, compared with slew rates of 0.3V/µsec for the rising edge and 5V/µsec for the falling edge in the conventional amplifier.

It has become very important to study the lightning surges that were induced in subscriber telecommunication equipment because of the increase of susceptible circuits to the over voltage. The test generator is desire to be developed evaluating the resistibility of equipments against lightning surges. This paper proposes a new lightning-test method for subscriber telecommunication equipment. The waveform of the test generator simulates that of the induced lightning surge voltage caused by a nearby return stroke. The output impedance of the surge generator is determined to match the common-mode impedance of telecommunication lines. The damaged condition of circuit parts and the trouble occurrence rate estimated by using this method agree well with actual observations.

Electromagnetic environments generated by power transmission system, possibilities of the interference and its mitigation method was introduced. In the frequency region below 10kHz, concern for DC and AC electric and magnetic field are described. In the frequency range above 10kHz, concern for discharges on power apparatus, electromagnetic emvironments generated by carrier system and fault locating system and passive interference are described. Electromagnetic environment caused by load equipments, that is harmonics, and undesirable electromagnetic emission from power converting units are described finally.

Long-wavelength 1.3 µm GaInAsP/InP vertical cavity surface-emitting lasers (VCSELs) have been demonstrated in an array configuration. With the strong current confinement by a buried heterostructure and the efficient optical feedback by a dielectric cavity, five VCSEL elements in a 24 array operated at room temperature with 5 mW total power output and wavelength error within 5%. The stacked planar optics including the VCSEL array is a promising optical transmitter in ultra large scale parallel optical communication systems.

This paper presents improvement of data error rate against burst noise by using both chip interleaving and hard limiter in direct sequence spread spectrum (DS/SS) communication systems. Chip interleaving, which is a unique method of DS/SS systems, is effective when burst noise power is small. However, when the burst noise power is large, date error rate is degraded. While, though hard limiter suppresses burst noise power, it gives little effectiveness when the burst noise length is long. Using chip interleaving and hard limiter together, as they work complementary, stable and considerable improvement of data error rate is achieved.

A system for measuring the low frequency amplitude and phase noises was set-up, with employing a phase sensitive detector and phase-shifter. It is noted that both noises were partly correlated. The phase noise was explained by the transit time fluctuation due to the fluctuating diffusion coefficient. The amplitude noise reduction was demonstrated by applying the inverted output of the phase noise to the amplitude noise.

Although electromagnetic analysis tools can provide good numerical data about the effects of electromagnetic interference, measurements are the method of choice for obtaining quantitative, accurate data on electromagnetic noise problems. Furthermore, since electromagnetic interference measurements often provide the only data accepted by most regulatory agencies, the measurements and their accuracies have recently become a very important issue in order to regulate and harmonize various electromagnetic compatibility emission and immunity standards. The measurement techniques and instrumentations of most use for making accurate electromagnetic interference measurements are presented in this paper.

GaAs-based micromachining is a very attractive technique for integrating mechanical structures and active optical devices, such as laser diodes and photodiodes. For monolithically integrating mechanical parts onto laser diode wafers, the micromachining technique must be compatible with the laser diode fabrication process. Our micromachining technique features three major processes: epitaxitial growth (MOVPE) for both the structural and sacrificial layers, reactive dry-etching by chlorine for high-aspect, three-dimensional structures, and selective wet-etching by peroxide/ammonium hydroxide solution to release the moving parts. These processes are compatible with laser fabrication, so a cantilever beam structure can be fabricated at the same time as a laser diode structure. Furthermore, a single-crystal epitaxial layer has little residual stress, so precise microstructures can be obtained without significant deformation. We fabricated a microbeam resonator sensor composed of two laser diodes, a photodiode, and a micro-cantilever beam with an area of 400700 µm. The cantilever beam is 3 µm wide, 5 µm high, and either 110µm long for a 200-kHz resonant frequency or 50 µm long for a 1-MHz resonant frequency. The cantilever beam is excited by an intensity-modulated laser beam from an integrated excitation laser diode; the vibration signal is detected by a coupled cavity laser diode and a photodiode.

Broadband antennas such as biconical antennas and log-periodic dipole antennas are generally used in automatic EMC measurements. However, these broadband antennas have not been used for accurate measurement because accurate specifications for them are lacking. Therefore, more accurate analysis is urgently required by the CISPR (International Special Committee on Radio Interference), to establish the specifications for broadband antennas for EMC measurements. In this paper, the AF of biconical antennas is calculated by using Moment Methods. The frequency characteristics and antenna height dependency of AF are presented. AF is also measured and compared to the data obtained by the calculations. Good agreement between the calculations and measurements is achieved, indicating the usefulness of our computation method. In addition, the effect of antenna separation distance and transmitting antenna height on AF is investigated. The calculated AF deviation from the reference value is nearly 0dB except for certain antenna arrangements. In these antenna arrangements, the field becomes null at the receiving antenna and widely varies in magnitude and phase around the null points. Therefore, the antenna is immersed in a non-uniform field, while the AF is defined on the assumption of a uniform field. Consequently, the erroneous AF will be derived from measurements around these null points and it will be greatly different from that obtained at other antenna heights. Thus, it is better to avoid these conditions during actual measurements. The effect of the ground plane on AF is also evaluated. AF is shown to be seriously affected by the ground plane especially at frequencies around 90MHz. It should be noted that AF deviation has crests corresponding to the null field at 300MHz. The obtained data will be useful in establishing specifications of biconical antennas for EMC measurements.

Telecommunications management activities have mostly been supported by operators; however, machines are gradually playing more important roles in the management arena by utilizing computing technology. Additionally, management systems can now be networked by using standard interface specifications. The study of human and machine integration is thus essential for achieving the sophisticated management objectives of telecommunications. This paper proposes the principles for a telecommunications management integration network (TMIN), which integrates human and machine management networks, and proposes a source text description method for transferring management communication knowledge from human to machine. First, reference models are proposed for the management process and management communication. These models cover network management activities of both humans and machines. Second, the contents of the source text are clarified. Source text presents human management knowledge in a form suitable for machine-machine communication. Third, an efficient source text description method is proposed that reduces redundancy and proliferation. Finally, a means of harmonizing management information definitions with TMIN is suggested to facilitate human-machine cooperation.

Managed Objects (MOs) can be specified by the combination of a static information model and a dynamic process model. First, this paper presents a mapping of attributes from a process model diagram to an information model diagram. Then, it introduces a concept of topology into these two models and proposes a hypothesis about the relationship of topology in these two models. To explicitly explain the hypothesis, it can be stated that all attributes of incoming or outgoing data related to a process in a process model are mapped to an information model where these attributes are interconnected by an explicit relationship which corresponds to a specific meaning, such as physical containment or logical connection. From an intuitive perspective, it can be said that if two attributes have a close topological relationship in a process model, the mapped attributes also have a close topological relationship in an information model. This hypothesis provides clues for determining whether there is an error in an attribute either in the process model or in the information model. By examining the way attributes of incoming or outgoing data related to a process are mapped to an information model, we can detect whether there is an error with respect to the process. The error correction is performed with the assistance of probability analysis. The method of error detection and correction can be implemented in a computer aided tool. Then, error detection on the attribute level becomes automatic, and error correction on the attribute level becomes interactive through the computer aided tool. Finally, the validity of the hypothesis is confirmed by analyzing ITU-T Recommendation M.3100. The specification of the fabric object class defined in M.3 100 is transformed into these two models and the hypothesis is validated for the analysis of the mapping between these two models.

This paper proposes a method for constructing an interface between an operations system and a workstation (OpS-WS interface) in a telecommunications management system based on TMN. To construct this interface, an appropriate communication protocol must be selected to perform management through efficient message exchange. The human machine interface provided by the WS should specify the managed objects. The interface also needs to be implemented so as to minimize the software revisions needed when the computer or its associated window system, or both, are changed. The proposed method addresses all these requirements. GUI components for realizing the HMI function are defined as Managed Objects as are communication network resources. Therefore, the communication protocol in TMN is defined as unique and it is possible to separate the HMI Interface from the OpS. CMIP is employed as the communication protocol to provide efficient message exchange. Software components that realize the human machine interface are selected so as to satisfy functional requirements specific to telecommunications management. The managed objects (MOs) and their relationships are investigated in order to represent these components appropriately. In the proposed method, the CMIP-based OpS-WS interface allows the OpS to take the manager role and the WS take the agent role. An implementation technique for MOs is also presented. The technique enables the software that implements MO behaviour to be coded easily. A prototype is built to confirm the correct operation of the proposed OpS-WS interface, and it is shown that CMIP requires fewer message exchanges to indicate alarms on the WS than other protocols. The proposed method is also advantageous because of its flexibility. That is, the WS software can be updated with little effort when the computer or its associated window system, or both, are changed.

This paper proposes a multi-fisheye distortion method which can show a large-scale telecommunication network in a single window on the display of a workstation or personal computer. This distortion method has three advantages over the conventional single-fisheye distortion method. First, the focus area is magnified smoothly by the fisheye distortion method, and the peripheral area coordinates are calculated linearly to avoid unnecessary distortion. Second, multiple focus areas are magnified smoothly by using an average of the coordinates calculated for the individual focuses. Third, the scale of unnecessary areas is reduced to provide sufficient space for magnification. The effectiveness of this method is demonstrated by applying to the display of large-scale networks. The effect of the resulting network map distortion on the user is tested by a subjective evaluation experiment.

Coding scheme is discussed for M-Choose-T communication in which at most T active users out of M potential users simultaneously transmit their messages over a common channel. The multiple-access channel considered in this paper is assumed to be a time-discrete noiseless adder channel without feedback with T binary inputs and one real-valued output, and is used on the assumption of perfect block and bit synchronization among users. In this paper a new class of uniquely decodable codes is proposed in order to realize error-free M-Choose-T communication over the adder channel described above. These codes are uniquely decodable in the sense that not only the set of active users can be specified but also their transmitted messages can be recovered uniquely as long as T or fewer users are active simultaneously. It is shown that these codes have a simple decoding algorithm and can achieve a very high sum rate arbitrarily close to unity if exactly T users are active.

This paper proposes an electronic retail payment system to provide flexible and efficient funds transfers with adequate security, reliability, circulativity, and anonymity even in large-scale applications. Funds are represented by a portable intelligent device called a card issued by a supervising organization, the system provider. Funds can be transferred from a card to another at an intelligent terminal called a mediator. To update the balance of each card, two digital signatures are generated by a three-party protocol conducted by the cards and mediator, and are encoded and appended to a write-once separate memory in the card. Old signatures are simultaneously nullified. Through a wired or radio non-real-time link, the generated signatures are periodically reported to the system provider to systemically manage possible abuses.

Telecommunications management is essentially an aggregation of a wide range of activities, including operations and management (O & M) of telecommunications services and customers as well as the network and network elements. During the period of rapid growth in telecommunications, the highest priority was to meet increasing market demand and to construct a telecommunications network infrastructure. Therefore, research and development in telecommunications management were subordinated to the evolution of telecommunications services and systems. Recently, customers have been demanding higher quality services, as a variety of new, advanced services have been introduced. This has led to the need to integrate telecommunications services and O & M services. This paper first reviews the history of the development of telecommunications O & M in parallel with the progress of telecommunications in Japan and clarifies specific features in each step of this progress. This analysis identifies urgent problems and their solutions. The results suggests that telecommunications O & M and O & M services should be considered as a key to making future services possible and to the value of those services in a multi-media telecommunications services environment. Based on these studies, the future direction of O & M is then shown, focusing on cooperative O & M involving the customer in the multi-media, multidomain telecommunications environment.

Mobile communication networks need public key cryptosystems that offer both low computation cost and user authentication. Tatebayashi et al. showed a key distribution protocol for such networks at Crypto'89 based on low exponent RSA. This paper shows that their protocol is not secure. We also present two types of secure and efficient key distribution protocols.