Frequency Reuse And Interference Avoidance Algorithm In Multibeam Satellite Systems

There are lots of advantages in satellite communication,such as long distance transmission,wide coverage,etc.However,satellite communication systems are currently facing the challenge of lacking enough frequency resources.In order to solve this problem,optimizing frequency reuse and interference avoidance should be introduced to satellite communication systems.The former can provide the benefits of interference reduction as well as capacity improvement,and the latter is able to improve the efficiency of spectrum utilization by allowing the secondary system to get some frequency resources without causing interference to the primary system.Firstly,a literature review is provided and then the research gap is analyzed.Secondly,a beam coverage scheme based on users' distribution in multibeam satellite communication system is proposed.By referring to three classical frequency reuse schemes being used in cellular systems,a frequency reuse scheme based on users' distribution is put forward.Thirdly,regarding interference avoidance,this thesis proposes two spectrum sharing scenarios: one is between a geostationary orbit(GEO)satellite system and a terrestrial system,and the other is between a GEO satellite system and a low earth orbit(LEO)satellite system.The research focus on avoiding the interference of the GEO satellite system which is caused by the terrestrial system and the LEO satellite system.Apart from this,an interference avoidance scheme related to the protection zone is put forward,and the bound on the protection radius is achieved through calculation and simulation.Finally,an interference avoidance scheme based on energy detection is proposed.In the spectrum sharing scenario between a GEO satellite system and a LEO satellite system,the traditional energy detection algorithm should be modified.Due to the relative motion of the LEO satellite and the GEO earth stations,the signal power received by the spectrum sensing module is constantly changing,which leads to the performance degradation of the conventional energy detection algorithm.For solving this problem,an energy detection algorithm based on forward prediction is put forward.