Research On Cognitive Satellite Communication Architecture And Spectrum Sensing Algorithm Based On Multiple Agents

Radio is one of the main communication methods for satellite communication networks.At present,it mainly adopts time division multiplexing technique.However,this technique fails to effectively utilize the existing spectrum resources.In addition,the expansion of communication capacity depends only on high frequency bandwidth.Therefore,how to make full use of the limited spectrum resources to improve network throughput and thereby avoid the appearance of "pseudo exhaustion" problem of spectrum resources is one of the hot issues for the current study.This paper first introduces the basic knowledge of satellite communication networks and cognitive radio(CR)technology.Then,it theoretically analyzes the feasibility and advancement of applying CR technology to satellite communication networks.On this basis,this paper mainly studies the cognitive satellite communication architecture based on multiple agents and interference-based spectrum sensing algorithm.This paper is generally arranged as follows:(1)It proposes cognitive satellite communication architecture based on multiple spectrum-sensing agents(SAs).Firstly,this paper analyzes the feasible mode of cognitive satellite dynamically accessing the idle licensed frequency bands.In allusion to the challenges faced by conventional CR networks in satellite communication,this paper points out that SA can replace the cognitive user to perform spectrum sensing and the cognitive satellite communication architecture based on multiple SAs can be established.Subsequently,it specifically introduces its network framework,functional structure,spectrum sensing operation mode and frame structure.Finally,it suggests that communication throughput should be regarded as a performance index.This architecture not only reduces the hardware design complexity,cost and additional energy consumption of cognitive users,but also increases their communication time,which consequently improves the communication throughput of cognitive networks.(2)It puts forward interference-based multi-agent spectrum sensing algorithm and obtains the average achievable throughput of cognitive user and network under different situations.According to the situation that cognitive satellite uses ground licensed frequency bands for uplink communication under vertical mode,this algorithm establishes a detailed network model and a multi-agent spectrum sensing model.The probability of interference is defined by the receiving SNR threshold of primary user,and the expected interference probability of the entire network is obtained by using distance distribution function.Through interference modeling,it analyzes the possibility of cognitive users and primary users to share the same frequency bands,and finds out the average achievable throughput of cognitive users and the network under different conditions.(3)It verifies the high performance of the interference-based multi-agent spectrum sensing algorithm through simulation experiments.In accordance to the situation that cognitive satellite utilizes the ground licensed spectrum to do uplink communication,this paper compares the interference-based multi-agent spectrum sensing algorithm with the conventional CR algorithm from the perspective of average throughput under different fusion rules and various SNR thresholds.The simulation results show that the average throughput of the proposed algorithm will not decrease with the increase of sensing time.Compared with the traditional CR algorithm,it obviously improves the average throughput of the cognitive user and the network,which is conducive to the further improvement of spectrum resource utilization rate.Finally,this paper makes a conclusion,and presents some prospects of further studies on several aspects of cognitive satellite communication,such as broadband spectrum sensing technology,fusion decision algorithms as well as the dynamic management and update of database resources.