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Satellite Communication System for Multi-Point Data Gathering over Ultra-Wide Area
Tanaka, Hiroshi,Inoue, Satoshi,Tsuchida, Toshihiro,Kazama, Hiroshi 통신위성우주산업연구회 2004 Joint Conference on Satellite Communications Vol.2004 No.-
In this paper, we propose a stellite communications system for gathering data from a lot of observation points scattered over an ultra-wide area. The system configuration takes into account the requirements for a practical data gathering system. The main target of our system is reduced communication cost by using a narrow frequency band and the main feature os an economical data gathering using a group-modem composed of a multi-carrier multi-rate filter bank. We describe our system investigation for channel assignment methods, data gathering sequences, and channel interference suppression between narrow band carries.
Polymer structure and properties in micro- and nanomolding process
Hiroshi Ito,Hajime Suzuki,Kunihiko Kazama,Takeshi Kikutani 한국물리학회 2009 Current Applied Physics Vol.9 No.2
Injection molding of thin-wall parts with micro/nano-scale patterns using various polymers was performed to clarify the processability and surface replication of molded parts. Effects of process conditions on processability, higher-order structure and surface properties of molded parts were evaluated. The optical anisotropy in the vicinity of the gate became higher than at any other positions. The height replication ratio of surface patterns increased with increasing injection speed, holding pressure, injection temperature and mold temperature. In the case of nanomolding, negative birefringence toward the flow direction appeared higher than at the skin–shear region from the observation of skin–shear and core structure inside molded parts. Thus, the molecular orientation axis was oriented along the thickness direction because of deformation during the demolding process. Thermal stability of nano-surface patterns was influenced by the size of surface features and internal higher-order structure.
REDUCTION OF PREVIEW DISTANCE IN LANE-KEEPING CONTROL
Keisuke Kazama,Kohei Nishizaki,Yuta Shirayama,Hiroyuki Furusho,Hiroshi Mouri 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.4
Lane marker detection is indispensable for a lane-keeping-control algorithm. However, it is impossible to detect lane markers when the curvature of the lane the vehicle is travelling on is large or when there is another car in front of the vehicle with short distance. For lane marker detection, it is desirable to set a preview point close to the vehicle. Therefore, by analyzing the block diagram of driver-vehicle system, we propose a method to reduce preview distance without lane tracking performance deterioration by increasing preview points from the conventional one point to two points. Furthermore, it is revealed that driving along a corner with constant curvature without steady-state deviation and arbitrary design of tracking dynamic characteristics become possible by increasing preview points.
Fundamental Characteristics of Onboard Bandwidth-Variable FFT Filter Bank
Yamashita, Fumihiro,Kazama, Hiroshi,Nakasuga, Yoshinori,Ueba, Masazumi 통신위성우주산업연구회 2000 Joint Conference on Satellite Communications Vol.2000 No.-
Voice service is currently the main service in mobile satellite communications, but in the future, there will be a demand for high-data rate services offering multimedia contents. Therefore, an onboard processor capable of handling services of various data rates is required. In the present study, it is assumed that a non-regenerative onboard processor will be used. The onboard processor must have functions to filter signals and convert their frequencies in a channel-by-channel manner. An FFT filter bank satisfies these requirements. However, the conventional onboard FFT filter bank is only applicable to signals of constant bit rate. Hence, the onboard bandwidth-variable filter bank that can handle many signals of various bit rates is proposed. The principle of operation of the bandwidth-variable FFT filter bank is described, then the BER performance of an FPGA-implemented design is evaluated.
Direct-multicasting Satellite Communications System
Masaaki, Tabata,Toshihiro, Tsuchida,Hiroshi, Kazama 통신위성우주산업연구회 2004 Joint Conference on Satellite Communications Vol.2004 No.-
Satellite communications is a promising medium for multicasting services such as streaming media delivery. However, most of the current satellite multicasting systems use a star-type network with one transmitting earth station called a bub, which is generally located in an urban area. Therefore, it is difficult for small businesses located in rural areas to send their contents by using satellite multicasting network. To meet these demands, we developed the direct-multicasting satellite communications system (DMSCS), which can provides a full-mesh type satellite network easily and cost-effectively. DMSCS uses our newly developed multi-carrier/multi-rate modem called the group modem and a highly effective channel assignment control program. The group modem is an FDMA (Frequency Division Multiple Access) modem. It is composed of a control module, user interface modules, a multi-carrier/multi-rate modem (MCMRM) module, and IF up/down-converter module. Its features include simultaneous connections with 32 different points, communication at an arbitrary rate, and the use of a dispersed and discontinuous spectrum. The highly effective channel assignment control program is the operation program for DMSCS. It has scale flexibility and high functionality. This paper described the features of DMSCS, the architecture and performance evaluation of the group modem, and example of new services making the best use of the advantages of DMSCS.
Toshinaga, Hideki,Kobayashi, Kiyoshi,Ohata, Kohei,Kazama, Hiroshi 통신위성우주산업연구회 2000 Joint Conference on Satellite Communications Vol.2000 No.-
This paper proposes an interference cancellation scheme for multimedia satellite communication systems, and presents results of hardware experiments on the scheme. In order to achieve higher frequency utilization efficiency, the high-speed TDM forward link signal and the low-speed spread spectrum FDMA return link signals are superposed. The conventional interference cancellation scheme utilizes a replica signal whose amplitude, phase and timing are fixed. It is virtually impossible to adjust them properly because factors such as equipment performance and propagation conditions vary irregularly. The proposed scheme is able to generate an accurate replica by utilizing a delay variation compensator and an adaptive filter. The results of a hardware experiment show that the proposed interference cancellation scheme holds the degradation in the return link signal to less than 3dB, when D/U is greater than -37dB.
Multi-Carrier Multi-Rate Modem for Universal FDMA/TDMA system
Yamashita, Fumihiro,Tabata, Masaaki,Kobayashi, Kiyoshi,Kazama, Hiroshi 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-
We introduce a new multi-carrier multi-rate modem (MCMRM) module designed to support Universal FDMA/TDMA systems. Universal FDMA/TDMA is a new system that flexibly supports MF-TDMA and TDMA as well as multi-rate FDMA. We believe that the Universal FDMA/TDMA system will allow both system operators and customers to utilize frequency and/or time resources more efficiently than is possible with conventional systems. To implement this system, we have developed a new MCMRM module. This module has advanced functions such as a novel frequency multiplexer/demultiplexer, multi-carrier frequency decomposition/regeneration, and multi-carrier burst demodulation. This paper provides a detailed outline of the recently developed functions and an experimental evaluation of their performance. Measured results from the experiments demonstrate the feasibility of developed MCMRM module.