This study investigates a low earth-orbital satellite (LEOS) communication system with cellular concept, where each satellite uses multi-beam to form cells. In terrestrial systems, the power of a received desired/interfering signal is mainly determined by the propagation loss, which is often modeled to be proportional to the fourth power of the propagation distance. On the contrary, in satellite systems, the loss varies as the square of distance and, in addition to the loss, the gain of the beam also affects the interference power. Because of this difference the superiority or inferiority of multiple access schemes discussed on terrestrial systems may not be adopted for satellite systems. Thus in this manuscript, the performance of FDMA and CDMA for LEO and terrestrial systems are compared. As a result, it is found that the well-known statement for terrestrial system, i.e., CDMA is superior to FDMA, may not always stands for LEOS systems.
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