Systems, methods, and devices are described for scheduling and mapping upstream communications in a satellite communications system. The disclosure includes various channelization and frequency hopping techniques. A gateway is described to perform novel allocation of time slots on upstream frequency channels to allow frequency hopping. A subscriber terminal may perform frequency hopping according to the allocation, and the range may be limited to the transition range of a digitally controlled oscillator unit at the subscriber terminal. A gateway is described to allocate time slots on different upstream frequency channels in a prioritized manner. Subscriber terminals may receive the allocation, and then control the assignment of their upstream traffic to the time slots.