Green integrated cooperative spectrum sensing for cognitive satellite terrestrial networks.

In this paper, a two-way relay-aided cognitive satellite terrestrial network (TR-CSTN) model is proposed, where primary users are located at the edge of the base station. In the TR-CSTN, one of satellite terminal users (STUs) is selected by the fusion center as the TR to forward information between two edge primary users with power of the TR. Meanwhile, these edge primary users share the licensed frequency band with the selected TR to send information to the satellite. Then, given the limited spectrum utilization and energy efficiency (EE) of the communication system, the cooperative spectrum sensing is employed to realize green communication. Specifically, the fusion center threshold, energy detection threshold, sensing duration and number of STUs are jointly optimized to enhance EE. Furthermore, considering that the node's energy shortage results in a short network lifetime, absolute EE gets improved. In detail, a power allocation scheme named normalized power aided Levy flight trajectory-based whale optimization algorithm (NP-LWOA) is provided, which fulfills effective energy compensation among STUs to prolong the network lifetime notably. Finally, numerical results confirm the theoretical analysis and show the effectiveness of the TR-CSTN and the NP-LWOA in efficiently achieving the concept of green communication compared with other methods.