| Summary: | Power domain non-orthogonal multiple access (PD-NOMA) has been widely recognized a spectrum-efficient multi-user transmission method when the channel gains across different users vary obviously. Due to the long travel distance between the space and the Earth in satellite communication scenarios, the advantages from PD-NOMA will disappear since the signals experience almost the same path loss. However, in hybrid satellite networks, terrestrial users equipped with different size antennas may lead to various receiving gains, which are equivalent to diverse channel gains. In this paper, by deeply exploiting such a characteristic, we propose a power domain multiplexing based co-carrier transmission method in a hybrid satellite network. Superposing a weak signal on a strong one, two signals are enabled to be transmitted on the same carrier with the bandwidth of the strong signal. To guarantee the signals are decodable at both sides, a user pairing strategy is investigated in detail, and the performance gain of the new method is further analyzed. Simulation results show that a carrier resource can be saved in the proposed method with the sacrifice of a marginal bit-error-rate performance.
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