When great disaster occurs, many terrestrial infrastructures are seriously damaged. Thus satellite communication has important roles to keep a minimum reliable connection. Quasi-Zenith Satellite System (QZSS) is expected to provide a high accurate positioning service and allows two-way communication which includes the terminal location and short messages. We propose SS-CDMA scheme which realizes the direct access from terminals to the satellite and many users simultaneous transmission using large spreading factor SS-codes. In this system, the keeping orthogonality among users in time and fre-quency domain is the most important issue. All terminals synchronize own clock and frequency to Quasi-Zenith Satellite (QZS). In this paper, the influence of residual timing jitter and frequency offset is evaluated with computer simulation.
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When great disaster occurs, many terrestrial infrastructures are seriously damaged. Thus satellite communication has important roles to keep a minimum reliable connection. Quasi-Zenith Satellite System (QZSS) is expected to provide a high accurate positioning service and allows two-way communication which includes the terminal location and short messages. We propose SS-CDMA scheme which realizes the direct access from terminals to the satellite and many users simultaneous transmission using large spreading factor SS-codes. In this system, the keeping orthogonality among users in time and fre-quency domain is the most important issue. All terminals synchronize own clock and frequency to Quasi-Zenith Satellite (QZS). In this paper, the influence of residual timing jitter and frequency offset is evaluated with computer simulation.