Software-Defined Network (SDN) and network function virtualization (NFV) technologies are emerging paradigms and enablers for the progress towards service delivery in satelliteterrestrial networks. In This Paper, we propose a significant improvement of our previous proposal, which consists of a downlink scheduling strategy in heterogeneous satellite-LTE-A network, while leveraging SDN and NFV and their role in network slicing. Thus, the main goal of this improved scheduler is to profit from slice isolation to boost the effectiveness of radio resources management. So, as slices are fully independent, we propose adaptive scheduling metric strategies specified according to the network conditions and traffic types. Performance evaluation shows that reliability can be enhanced by reducing the packet of loss ratio achieved via isolation between slices. Results show that the QoS degradation may decrease the metrics of traffic however, this cannot influence the quality of experience in the other slices.