System and method for downlink scheduling that optimizes downlink (DL) capacity

An illustrated embodiment disclosed herein is a method including maintaining, by a satellite, a plurality of physical data units (PDUs). Each PDU has a corresponding spreading factor (SF). The method includes selecting, by the satellite, a lowest SF, adding, by the satellite, all PDUs associated with the lowest SF to a slot, and determining, by the satellite and until the determination is affirmative, whether available capacity of the slot is less than a predetermined threshold. The method includes, responsive to determining that the available capacity of the slot is not less than the predetermined threshold, selecting, by the satellite, a greater SF and adding, by the satellite, one or more PDUs associated with the greater SF to the slot. The method includes responsive to determining that the available capacity of the slot is less than that the predetermined threshold, sending, by the satellite, the slot to an endpoint.