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A Note on the Simple Regenerative Repeating Process for Communication Satellites
Yamazato, Takaya,Ogawa, Akira 통신위성우주산업연구회 2005 Joint Conference on Satellite Communications Vol.2005 No.-
We have been working on a relay process of communication satellite. We omit the regenerative process at the satellite. Only routing and other necessary operation are performed at satellite. Simple configuration and signal processing may promise robust and long-lasting operations in space. We call it "simple regenerating repeater." However, an issue is how to realize the reliable transmission even if we omit the error correcting and detecting process at the satellite. To overcome this issue, we propose to place the error detection code prior to QAM mapping. Using the status of error detector, it is possible to give accuracy to the received signal so we can improve the performance by soft decoding. The FPGA experimental boards of the system are also introduced
New Error Correcting Scheme for Hard Detected QAM Signal
Yamaoka, Tomaya,Yamazato, Takaya,Okada, Hiraku,Katayama, Masaaki,Ogawa, Akira 통신위성우주산업연구회 2004 Joint Conference on Satellite Communications Vol.2004 No.-
In order to achieve high speed satellite communication, we propose a new R=m-2/m error correcting scheme for hard detected $2^m$-QAM signal, where we consider m $\geq$ 6. The main focus of the paper is to improve the performance even in the case of hard-detection. As results, we found that our proposed error=correcting scheme achieves good error performance despite the hard detection and the high coding rate.
Characterization of a simplified regenerative repeater for broadband satellite communications
Kuwamura, Hidetsugu,Ogawa, Akira,Yamazato, Takaya 통신위성우주산업연구회 2005 Joint Conference on Satellite Communications Vol.2005 No.-
This paper is concerned with performance evaluation for an experimental model of a repeater for broadband satellite communications. For the purpose of realizing a high speed and flexible internet satellite communication system, we propose a simplified configuration of satellite regenerative repeater. In this repeater, the amount of signal processing is limited so that the input signal is only AD converted and stored, but a complex function of error control is left to the earth stations. While the information data are modulated with QAM, the necessary information for the onboard routing is carried on the preamble potion placed at the top of the packet and modulated with the differential binary PSK. In this paper, measured results of the bit error rate for this simplified regenerative repeater are described
Nishihara, Kazuharu,Okada, Hiraku,Yamazato, Takaya,Katayama, Masaaki 통신위성우주산업연구회 2003 Joint Conference on Satellite Communications Vol.2003 No.-
To increase the channel efficiency, most of the Low Earth-Orbital satellite (LEOs) systems use the multibeam antenna and reuse the available channels. But in such systems, a beam handover occurs very frequently and a dropping probability becomes very high compared with the one beam systems. In this paper, we propose the nondropping handover and channel allocation scheme in the above LEOs systems. In the proposed scheme, we allocate an extra idle channel for a new call. Because of the predictable change of channel reuse distances, each user can always use the same channel as before. Furthermore, we proposed some cost functions used by channel selection and channel reassignment. For comparison, we show the lower bound of blocking probability by maximal complete dependent set (MCDS). We confirm that the proposed channel selection scheme improves the system performance by computer simulation.