###### Abstract
Section 4 presents the numerical simulation. Section 5 concludes this paper. Spectrum-Sharing Method for the Integrated Wireless Multimedia Sensor and Cognitive Satellite Network  
Figure 1 depicts the architecture of the integrated multimedia wireless sensor and cognitive satellite network proposed in this work, which is composed of the sensor nodes, the sink, the LEO satellite system and the remote control host. The LEO satellite system plays the role of the auxiliary to connect the sensor nodes and the remote control host, and it shares the same frequency with the GEO system in the downlink. More details are presented as follows. Sensor nodes: Sensor nodes in the sensor field sense different dynamic physical quantities and convert the quantities into electrical signals. In addition, some are complemented by additional multimedia traffic sources (i.e., computers, cameras, smart phones and cellular phones). The electrical signals are digitalized and encapsulated into data packets and exchanged with the sink through the terrestrial wireless link. Figure 1: Architecture of the integrated wireless multimedia sensor and cognitive satellite network. LEO user (Sink): The LEO user functions as the sink which provides the interface between the satellite system and the terrestrial sensor network. It can store and retrieve multimedia data such as video, audio, and images. LEO satellite system: The LEO satellite system is regarded as the auxiliary to connect sensor nodes and the network control center. The LEO user exchanges the data with the LEO gateway through the communication link of the satellite, including video, audio, images and other data streams. Remote control host: Remote control host is connected to the LEO gateway through the Internet or the private terrestrial network. It mainly transmits and receives data packets to send and obtain the information, e.g., multimedia contents and control signalings. Figure 2 depicts the schematic of the novel spectrum-sharing method for the integrated multimedia wireless sensor and cognitive satellite network. The primary GEO system is an already deployed system, whereas the secondary LEO system adapts its frequency scheme to ensure the unobstructed operation of the primary system. Both systems provide fixed service with the same spectrum in the downlink, and the antennas of the users keep tracking their corresponding satellites precisely. The two systems deploy multibeam payloads which leverage the spatial reuse of spectrum resource. The frequency scheme of the GEO satellite is static, and the frequency reuse factor is seven [43], whereas those of the LEO satellite varies with the satellite motion. The cognition is achieved by sharing the satellite ephemeris and frequency scheme with the help of the signaling link between the gateways. The beam size of GEO is much larger than that of LEO because the satellite altitudes differ greatly. An LEO beam that is inside a GEO beam can use any frequencies except for that allocated to the GEO beam. Thus, the frequency division multiplexing can be implemented among the beams of LEO satellite, and the frequency reuse factor is smaller than seven. However, the overlap between GEO and LEO is dynamic because the LEO satellite moves relative to the ground, and the CCI occurs if the co-channel beams cover the same region. The gateways of LEO and GEO systems are connected so  
Figure 2: Schematic of the novel spectrum-sharing method. that the cognition is achieved by sharing the current frequency scheme and the satellite ephemeris. Therefore, it can be predicted when and where the interference will occur. Once the interference is imminent, the frequency allocation will be adjusted. It should be noted that, with elaborate frequency allocation, the interference can be avoided totally rather than mitigated, which implies a higher spectral efficiency.