Orthogonal Coded Modulation in Alerting Channel for GEO Mobile Satellite System

In GEO (Geostationary Earth Orbit) mobile satellite system, subscribers could not be paged when the MES (Mobile Earth Station) is normally out of coverage area due to additional propagation path losses. In this paper, an orthogonal coded modulation scheme based on BPSK (Binary Phase Shift keying) is proposed for the GEO mobile satellite system for the sake of establishing the call. Compared with the common paging channel modulation method QPSK (Quadrature Phase Shift Keying) and BPSK, the code words are mutual orthogonal, which is convenient for demodulation. And to be emphasized, the simulation results show that this scheme can increase the SNR (Signal Noise Ratio) of actual transmitted information, which is greatly more than the SNR of data in the common paging channel. It allows subscribers to be paged even when the MES is normally out of coverage area due to additional propagation path losses, and to move on an advantageous position.