This paper proposes a suitable combination of the digital modulation schemes and the coding-rate of forward error correction (FEC) schemes for satellite digital video communication networks. The comparative study is carried out by computer simulation considering non-linearly amplified, narrow bandwidth satellite channels with adjacent channel interference signals. The proposed system employs an offset QPSK modulation scheme supported by the coding-rate of 7/8 convolutional encoding and Viterbi decoding to realize high-quality and compact spectrum characteristics in non-linear channels. By employing a 32Mbps DPCM video codec, the developed prototype system achieves a post demodulated S/N ratio of higher than 52dB. Moreover, it achieves high protection ratio against co-channel interference than conventional analog FM systems. The optimized digital video transmission system makes it possible to transmit high-quality NTSC video signals over non-linearly amplified narrow bandwidth satellite channels, for example 27MHz or 36MHz bandwidth transponders, with high-security digital encryption.

Under the conditions of Poisson arrivals and single copy transmission, we designed a minimum delay protocol for packet satellite communications. The approach is to assume a hybrid random-access/reservation protocol, derive its average delay and minimize the delay with respect to all tunable system parameters. We found that for minimum average delay,1) a spare reservation should normally but not always be made for each packet transmission.2) all unreserved slots (i.e. Aloha slots) should be filled with a packet rate of one per slot whenever possible. In other words, the utilization of Aloha slots should be maximized.3) an optimum balance between transmitting packets and making reservations before transmission should be maintained.

A new computer architecture using multiwavelength optoelectronic integrated circuits (OEICs) is proposed to attack the problems caused by interconnection complexity. Multiwavelength-OEIC architecures, where various wavelengths are employed as information carriers, provide the wavelength as an extra dimension of freedom for parallel processing, so that we can perform several independent computations in parallel in a single optical module using the wavelength space. This multiplex computing" enables us to reduce the wiring area required by a network and improve their complexity. In this paper, we discuss the efficient multiplexing of Batcher's bitonic sorting networks, highly parallel computing architectures that require global interconnections inherently. A systematic multiplexing of interconnection topology is presented using a binary representation of the connectivities of interconnection paths. It is shown that the wiring area can be reduced by a factor of 1/r2 using r kinds of wavelength components.

Link conditions of a low-earth orbit (LEO) satellite communications system were evaluated, to provide the information necessary for designing a broadband LEO-SAT communications system. The study was made both for optical intersatellite and user/satellite links. For the optical intersatellite link (ISL), we examined several ISL configurations in a circular polar orbit, and found that when the satellites are in the same orbital plane, the link parameters are quite stable, that is, the link between adjacent satellites can be regarded as fixed and, therefore, suitable for broadband transmission via an optical link. However, the link conditions between adjacent orbits change very quickly and over a wide range. To overcome this and extend the network path between satellites in adjacent orbital planes, we proposed intermittent use of the link between satellites in co-rotating adjacent orbital planes at the low latitude region, i.e., only during the period of stable conditions. The optical intersatellite link budget also sets link parameters that are realistic, given present optoelectronic technologies. From quantitative evaluations of the user/satellite link, we believe that both the satellite altitude and minimum elevation angle are critical, both in defining the quality of the service of the LEO-SAT system and in their impact on the other transmission parameters. The link loss, the visible period and the required number of satellites vs. satellite altitude and elevation angle are also indicated. These are important considerations for future system design.

This paper proposes a feedback-loop type transmission power control (TPC) scheme coupled with first and second order prediction methods and analyzes the optimum control period and residual control error. In order to minimize residual control error, the three main factors contributing to residual control error are analyzed. First, to detect accurately up-link rain attenuation, a channel quality detection method is proposed and analyzed experimentally for puseudo-error detection. Second, rain attenuation rates in Ka band are measured and analyzed statistically. Finally, the optimum control period of the proposed TPC scheme is analyzed. The simulation results on the prototype TPC system show a maximum of 4.5 dB residual control error is achievable with an optimum control period of about 1 second to 1.5 seconds.

The paper considers multiple-valued logic systems having the property that the ambiguity of the system increases as the ambiguity of each component increases. The partial-ordering relation with respect to ambiguity with the greatest element 1/2 and minimal elements 0, 1 or simply the ambiguity relation is introduced in the set of truth values V {0, 1/ (p1), , 1/2, , (p2) / (p1), 1}. A-monotonic p-valued logic functions are defined as p-valued logic functions monotonic with respect to the ambiguity relation. A necessary and sufficient condition for A-monotonic p-valued logic functions is presented along with the proofs, and their logic formulae using unary operators defined in the ambiguity relation are given. Some discussions on the extension of theories to other partial-ordering relations are also given.

A non-profit satellite communication network is desired to be configured by using low cost earth stations in the field of education, research and health in the Pacific region. This paper proposes the following concept as one of the tools to realize such a network: (a) A hitchhiker transponder dedicated to the network, and (b) The volunteer group prepares earth stations. A preliminary system design shows that the S band hitchhiker payload is most appropriate and has the weight of about 3kg. The feasibility of manufacturing earth stations by a volunteer group is examined through the experiment using ETS-V satellite. The parameters of the hitchhiker payload are re-examined on the basis of the experience of the experiment.

This paper describes the novel relaxation-based algorithm for the harmonic analysis of nonlinear circuits. First, we present Iterated Spectrum Analysis based on harmonic balance method, where the harmonic balance method is applied to every node independently. As a result, we can avoid dealing with large scale Jacobian matrices and reduce the total simulation time, compared with the conventional method based on Galerkin's procedure or the harmonic balance method. Next, we define the frequency domain latency. Furthermore, we refer to the possibility for exploitation of three types of latency, i.e., relaxation iteration latency, frequency domain latency and Newton iteration latency. And we propose the multirate-sampling technique based on the consideration of the frequency domain latency. Finally, we apply the present technique to the simple analog circuit simulation and verify its availability for the harmonic analysis.

We present a navigation system using ultrasonic sensors for unknown and dynamic indoor environments. To achieve the robustness and flexibility of the mobile robot, we develop a behavior-based system architecture, consisting of multi-layered behaviors. Basic behaviors required for the navigation of a mobile robot, such as, avoiding obstacles, moving towards free space, and following targets, are redundantly developed as agents and combined in a behavior-based system architecture. An extended potential filed method is developed to produce the appropriate velocity and steering commands for the behaviors of the robot. We demonstrate the capabilities of our system through real world experiments in unstructured dynamic office environments using an indoor mobile robot.

We have proposed a new omnidirectional image sensor COPIS (COnic Projection Image Sensor) for guiding navigation of a mobile robot. Its feature is passive sensing of the omnidirectional image of the environment in real-time (at the frame rate of a TV camera) using a conic mirror. COPIS is a suitable sensor for visual navigation in real world environment with moving objects. This paper describes a method for estimating the location and the motion of the robot by detecting the azimuth of each object in the omnidirectional image. In this method, the azimuth is matched with the given environmental map. The robot can always estimate its own location and motion precisely because COPIS observes a 360 degree view around the robot even if all edges are not extracted correctly from the omnidirectional image. We also present a method to avoid collision against unknown obstacles and estimate their locations by detecting their azimuth changes while the robot is moving in the environment. Using the COPIS system, we performed several experiments in the real world.

The 22 mechanical optical switch for single mode fiber (SMF) is reported. By using the precision grinding and molding techniques all-plastic multiple-fiber connector, 22 pin-referenced indirect slide switch is developed. The characteristics and the reliability test's results of this optical switch are also reported. Evaluations confirm that the switch has low insertion loss, high-speed switching, stable switching operations and reliability in practical applications.

Improvement of fatigue behavior of a fusion spliced portion on a carbon-coated fiber is achieved by recoating carbon using a thermal-CVD process with a CO2 laser as a local heat source. The fatigue parameters, so-called n-values, of 121 and 94 are obtained on the non-spliced portion and the spliced portion, respectively. Assuming a life time prediction model, these high values have been proved to have an advantage in a long-term reliability and to be sufficient in a practical submarine cable use.

Subjective quality tests have proven that embedded adaptive differential PCM (ADPCM), known to tolerate information loss through bit dropping, does not maintain sufficient speech quality when directly applied to asynchronous transfer mode (ATM) due to the fixed-length cell transmission scheme unique to ATM. We propose a coding and transmission scheme which enhances the performance by adjusting the embedded ADPCM coding rate according to input speech characteristics, thereby taking advantage of the ATM environment, where the transmission of variable rate sources is feasible. By varying the number of code bits of an embedded ADPCM coder from 6bits per sample, or 48kbps, for blocks of speech with a high prediction gain, to 2bits, or 16kbps, for silent blocks, a good compromise between coding bit rate and speech quality with gradual degradation due to information loss is achieved. The results of subjective evaluation tests showed the speech quality of the proposed scheme to be over 3.5 mean opinion score (MOS) on a scale of 1 to 5 at a cell loss rate of 10%. A prototype of the codec and the ATM cell assembly/disassembly functions were also fabricated using 3 conventional digital signal processors (DSPs) for real-time conversation tests.

We designed and fabricated a prototype 0.4-µm-gate CMOS/SIMOX PLL LSI in order to verify the potential usefulness of ultrathin-film SIMOX technology for creating an extremely low-power LSI containing high-speed circuits operating at frequencies of at least 1 GHz and at low supply voltages. This PLL LSI contains both high-frequency components such a prescaler and low-frequency components such as a shift register, phase frequency comparator, and fixed divider. One application of the LSI could be for synthesizing communication band frequencies in the front-end of a battery-operated wireless handy terminal for personal communications. At a supply voltage of 2 V, this LSI operates at up to 2 GHz while dissipating only 8.4 mW. Even at only 1.2 V, 1 GHz-operation can be obtained with a power consumption of merely 1.4 mW. To explain this low-power feature, we extensively measured the electrical characteristics of individual CMOS/SIMOX basic circuits as well as transistors. Test results showed that the high performance of the LSI is mainly due to the advanced nature of the CMOS/SIMOX devices with low parasitic capacitances around source/drain regions and to the new circuit design techniques used in the dual-modulus prescalar.

By optimizing the structure of erbium-doped fibers, high efficiency such as a gain coefficient of 6.3dB/mW, or a slope efficiency of 92.6% have been realized with very flat wavelength dependence. Though the optimized structure has high NA, the splice loss with standard fibers can be lowered by the additional arc technique. The carbon coated fiber with a fatigue parameter over 150 guarantees the reliability, even when wounded on a small coil. In-line isolators and WDM couplers have been also developed. An amplifier module has been assembled, resulting in an output power more than +16dBm owing to the high performance of each component.

Selective epitaxial growth technology has been extended to the base formation of a transistor on the basis of the SATURN (Self-Alignment Technology Utilizing Reserved Nitride) process, a high-speed bipolar LSI processing technology. The formation of a self-aligned base contact, coupled with SIC (Selective Ion-implanted Collector) fabricated by lowenergy ion implantation, has not only narrowed the transistor active regions but has drastically reduced the base width. A final base width of 800 and a maximum cut-off frequency of 31 GHz were achieved.

The evolution of Multiple-Valued Logic (MVL) circuits has been inexorably tied to the rapid technological changes induced by evolving needs and emerging developments in computing methodologies. Unfortunately for MVL, the numbers of designers of technologies and circuits whose lives are dedicated to the improvement of binary techniques, are large and overwhelming. Correspondingly, technological developments in MVL typically await the appearance of a problem or technique in the larger binary world to motivate and/or make possible some new advance. Such opportunities are inevitably quite transient since each such problem is simultaneously attacked by many others of a more conventional bent, and, as well, each technological change begets yet another, quickly. It is in the sensing of this reality that the present paper is written. Correspondingly, its thrust is two-fold: One target is the possibility of encouraging a leap ahead through modest technological projection. The other is the possibility of identifying application areas that already exist in this unbalanced competition, but which are specially suited to multiple-valued solutions. For example, it has been clear for decades that one such area is that of arithmetic. Correspondingly, we in MVL must strive quickly to concentrate our efforts on applications that exploit such demonstrable strengths. Some such applications are includes here; others are visible historically, many probably remain to be found: Search on!

This paper studies multidimensional linear periodically shift-variant digital filters (LPSV filters). The notion of a generalized multidimensional transfer function is presented for LPSV filters. The frequency characteristic of the filters is discussed in terms of this transfer function. Since LPSV filters can decompose the spectrum of an input signal into some spectral partitions and rearrange the spectrum, LPSV filters can serve as a frequency scrambler. To show the effect of multidimensional frequency scramble, 2-D LPSV filters are designed based on the 1-D Parks-McClellan algorithm. The resultant LPSV filters divide the input spectrum into some components that are permuted and possibly inverted with keeping the symmetric of the spectrum. Experimental results are presented to illustrate the effectiveness of frequency scramble for real images.

A high-speed data communication service such as inter-LAN is one of many services possible with ATM-based B-ISDN. Design objectives were to simplify the connection setup procedure, to ensure efficient utilization of network capacity, and to reduce delay in servers. These objectives were met in a B-ISDN service trial system featuring distributed connectionless servers connected by permanent virtual channels and cell-by-cell processing in the connectionless server. The system's eight connectionless servers accommodate up to 256 subscriber network interfaces. The authors discuss how multicast can be provided in ATM-based connectionless data networks for inter-LAN communications. Four possible configurations, distinguished by copy function (multicast/broadcast) and on functional arrangement in the inter-connectionless server network (centralized/distributed), are presented. The configurations are compared from perspectives of required hardware and network capacity. The distributed broadcast function is shown the most reasonable solution.

Asynchronous Transfer Mode (ATM) is an information transport technique that well supports Broadband ISDN (B-ISDN). One unsolved problem to the perfection of ATM networks is to provide a testing environment that conforms to some standardized network management scheme. From this point of view, remotely controlled virtual path testing is considered in this paper. Remotely controlled virtual path testing should be executed through the standardized Telecommunications Management Network (TMN) model, which employs the OSI systems management concept as the basis of information exchange. Thus, this paper addresses the two issues that arise when OSI systems management standards are applied to virtual path testing. One issue is to define relevant information models. The other issue is to provide test resources with a concurrency control mechanism that guarantees a consistent test environment without causing deadlocks. To resolve these issues, technical requirements are clarified for the remote control of test resources. Next, alternatives to the concurrency control mechanism are shown and compared through computer simulations. A method of defining information models is then proposed. The proposed method ensures the easy storage and retrieval of intermediate test results as well as permitting the effective provision of concurrency control for test resources. An application scenario is also derived. The scenario shows that tests can be executed by using standardized communication services. These results confirm that virtual path testing can be successfully achieved in conformance with the OSI systems management standards.