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To deal with the spectrum demand of new low earth orbit satellite (LEO) communication component and the aggregate interference generated by incumbent terrestrial component in future integrated satellite-terrestrial system, a novel space-borne spectrum-sensing (SS) and spectrum-database assisted spectrum-sharing scheme with interweave model for LEO cognitive system was proposed.Firstly, considering the adverse impact of the sparse distribution of LEO cognitive node (CN) on SS and interference cartography (IC), the concept of cognitive node position was put forward.Secondly, the spectrum-DB was built based on dual-threshold hybrid SS and IC with LEO cognitive system.Finally, a spectrum-sharing scheme with multi-state virtual network (MSVN) was designed, which could make the coexistence between terrestrial component and uplink of LEO component available.Simulation results indicate that the spectrum-database approach based on the proposed dual-threshold hybrid SS and IC can support the spectrum awareness of high reliability with relatively low-density LEO CN, and that the proposed cooperative access scheme based on spectrum-database and interweave model for LEO component can share spectrum with terrestrial one, but not significantly increase the end-to-end delay of LEO component.

To deal with the spectrum demand of new low earth orbit satellite (LEO) communication component and the aggregate interference generated by incumbent terrestrial component in future integrated satellite-terrestrial system, a novel space-borne spectrum-sensing (SS) and spectrum-database assisted spectrum-sharing scheme with interweave model for LEO cognitive system was proposed.Firstly, considering the adverse impact of the sparse distribution of LEO cognitive node (CN) on SS and interference cartography (IC), the concept of cognitive node position was put forward.Secondly, the spectrum-DB was built based on dual-threshold hybrid SS and IC with LEO cognitive system.Finally, a spectrum-sharing scheme with multi-state virtual network (MSVN) was designed, which could make the coexistence between terrestrial component and uplink of LEO component available.Simulation results indicate that the spectrum-database approach based on the proposed dual-threshold hybrid SS and IC can support the spectrum awareness of high reliability with relatively low-density LEO CN, and that the proposed cooperative access scheme based on spectrum-database and interweave model for LEO component can share spectrum with terrestrial one, but not significantly increase the end-to-end delay of LEO component.

To solve the problem of the weak spectrum-cognitive ability caused by monitoring angle, direction resolution, limited processing ability and peak power for a low-earth-orbit (LEO) satellite, a multi-satellite cooperative spectrum cognitive method integrating Stackelberg game and federated learning was proposed.Firstly, considering the available computing resource, cognitive performance, processing and transmission delay of each spectrum cognitive satellite, a cooperative-satellite selection and computing-resource allocation algorithm was built for multiple spectrum-cognitive tasks.Secondly, based on the selected satellites and the allocated computing resources, a low-complexity multi-satellite cooperative spectrum cognitive strategy was further designed, which could automatically sense the spectrum holes, and detect interference as well as identify the modulation mode.Simulation results demonstrate that compared to the single-node cognitive method, the designed multi-satellite cooperative spectrum cognitive strategy can obtain a better cognitive performance.Moreover, comparing with the existing model, the model utilized in the designed strategy can effectively achieve 96.69% and 93.32% lower number of parameters and required floating point operations per second, whilst maintaining the performance.

To solve the problem of the weak spectrum-cognitive ability caused by monitoring angle, direction resolution, limited processing ability and peak power for a low-earth-orbit (LEO) satellite, a multi-satellite cooperative spectrum cognitive method integrating Stackelberg game and federated learning was proposed.Firstly, considering the available computing resource, cognitive performance, processing and transmission delay of each spectrum cognitive satellite, a cooperative-satellite selection and computing-resource allocation algorithm was built for multiple spectrum-cognitive tasks.Secondly, based on the selected satellites and the allocated computing resources, a low-complexity multi-satellite cooperative spectrum cognitive strategy was further designed, which could automatically sense the spectrum holes, and detect interference as well as identify the modulation mode.Simulation results demonstrate that compared to the single-node cognitive method, the designed multi-satellite cooperative spectrum cognitive strategy can obtain a better cognitive performance.Moreover, comparing with the existing model, the model utilized in the designed strategy can effectively achieve 96.69% and 93.32% lower number of parameters and required floating point operations per second, whilst maintaining the performance.

Satellite Internet has the ability of global seamless coverage, which will be an important part of the future land-sea-air-space integrated network.Firstly, the architecture of satellite Internet was discussed, which included the general composition of the system, networking mode, working process, etc.Secondly, the methods of modeling broadband and narrowband traffic were proposed to extract the uneven space-time distribution characteristics of traffic for satellite Internet.Then, the co-frequency interference of spectrum-sharing was analyzed, showing that there would be more serious co-frequency interference among different non-geostationary satellite orbit (NGSO) constellations in the future.Next, the schemes of both beamforming design for low earth orbit satellite and beam-hopping design for high orbit satellite were explored, which could significantly improve the system capacity through efficient mining of space-domain resources.Finally, the development prospect of several technologies of satellite Internet were given.

Satellite Internet has the ability of global seamless coverage, which will be an important part of the future land-sea-air-space integrated network.Firstly, the architecture of satellite Internet was discussed, which included the general composition of the system, networking mode, working process, etc.Secondly, the methods of modeling broadband and narrowband traffic were proposed to extract the uneven space-time distribution characteristics of traffic for satellite Internet.Then, the co-frequency interference of spectrum-sharing was analyzed, showing that there would be more serious co-frequency interference among different non-geostationary satellite orbit (NGSO) constellations in the future.Next, the schemes of both beamforming design for low earth orbit satellite and beam-hopping design for high orbit satellite were explored, which could significantly improve the system capacity through efficient mining of space-domain resources.Finally, the development prospect of several technologies of satellite Internet were given.

Beam-hopping technology provides a basis for flexible allocation and efficient utilization of satellite resources,and it is considered as a key technology of the new generation of high-throughput satellite.With the goal of service-driven,efficient utilization of resources and on-demand coverage of hot spots area,from the aspects of system architecture,communication system,working mechanism,resource allocation method and beam-hopping pattern design,user access strategy,air interface protocol design and system workflow,a top-down feasibility and technical foundation was provided for the design of a new generation of high-throughput satellite communication system based on beam hopping.Finally,it meet the requirements of flexible and mobile information service for the space-earth integration network,as well as the demand of the space-based backbone network with high reliability and large capacity transmission.

Beam-hopping technology provides a basis for flexible allocation and efficient utilization of satellite resources,and it is considered as a key technology of the new generation of high-throughput satellite.With the goal of service-driven,efficient utilization of resources and on-demand coverage of hot spots area,from the aspects of system architecture,communication system,working mechanism,resource allocation method and beam-hopping pattern design,user access strategy,air interface protocol design and system workflow,a top-down feasibility and technical foundation was provided for the design of a new generation of high-throughput satellite communication system based on beam hopping.Finally,it meet the requirements of flexible and mobile information service for the space-earth integration network,as well as the demand of the space-based backbone network with high reliability and large capacity transmission.