Satellite communications systems, methods, and related devices are described. In one embodiment, a satellite communications system is configured to dynamically allocate bandwidth and frequencies among different beams. Bandwidth request data may be received and compiled from the terminals. The satellite may be configured with different beam coverage areas, and may dynamically allocate bandwidth and particular frequency channels to different beam coverage areas based on the requests. In each of a series of one or more epochs, and according to the bandwidth requests, there may be allocations among carrier groups, traffic classes, and particular terminals. The setup of slot structure and selection of modes for particular terminals is also addressed.