A communication system consists of a satellite constellation including a number of NGSO satellites, one or more gateways and a control center. The satellites facilitate communication for multiple user terminals. Each gateway communicates with the satellites and user terminals and provides connectivity to the terrestrial networks, and the control center controls operation of the satellites, the gateways and the user terminals. The satellites, the user terminals, the gateways and the control center include hardware that may be software-defined network (SDN) enabled to ensure efficient admission control, precision handover management and quality-of-service (QoS) enforcement algorithms.