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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.
Satellite experiments on Variable Polarization/Frequency Division Multiplexing(VPFDM)
Yamashita, Fumihiro,Kobayashi, Kiyoshi,Ueba, Masazumi,Zakouji, Takaaki 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-
We report the results of satellite experiments on Variable Polarization/Frequency Division Multiplexing (VPFDM) and its operational principles. VPFDM is a new multiple access method that enables each user to freely utilize dual polarization and frequency resources. No BER degradation was observed in VPFDM satellite experiments, meaning that the VPFDM modem can demodulate received signals as expected regardless of the polarization rotation angle or dynamic polarization rotation. Because of this performance, we expect VPFDM to be applied to the maritime satellite communications service called Earth Station onboard Vessel (ESV)[l][2], to which Ku band is allotted as a primary band in the WRC 2003.
A proposal on the configuration of AFC applicable to a wide range of frequency offset
Yamashita, Fumihiro,Nakasuga, Yoshinori,Mitsugi, Jin,Ueba, Masazumi 통신위성우주산업연구회 2002 Joint Conference on Satellite Communications Vol.2002 No.-
Future mobile satellite communications systems will provide services to fast vehicles. Thus, the signal received by the user terminals may experience a wide frequency shift away from the assigned frequency that is caused by the Doppler shift and insufficient precision of the Oscillator. This paper presents a new auto-frequency control (AFC) configuration that is capable of removing a large amount of frequency offset (about ${\pm}$0.6 fs, where fs means symbol rate of signal). The operational principle of the AFC is described, and its BER performance and initial acquisition time are evaluated via computer simulation.
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.