Research On Spectrum Sensing Technology For Integrated Space-ground Network

The demand for broadband wireless spectrum is increasing rapidly due to the rapid development of multimedia wireless services and high-throughput satellite technology.Time division multiplexing is widely used in satellite communications at present,but there is less research on spectrum utilization.Cognitive Radio(CR)can be an efficient technique to increase the spectrum utilization efficiency of heterogeneous wireless networks.However,how to use this technology in a hybrid network of multiple terrestrial wireless networks and satellite networks to improve the utilization rate of such networks is a hot issue.Cognitive Radio technology allows the coexistence of primary and secondary users within the same spectrum without obstructing the normal operation of the primary licensed systems.Spectrum sensing is one of the core technology in CR,but the high sampling rate has hampered the development of traditional broadband spectrum sensing seriously.Compressed Sensing(CS)can overcome the traditional restriction that sampling rate must satisfy the Nyquist sampling theory,and it is also an important technology available for the integrated space-ground network.The work of the thesis is partly supported by the Open Fund Project of Aerospace Information Application Technology Key Laboratory of China Electronics Technology Group Corporation.In view of the hot issues above,the main work of this thesis is as follows:(1)A cognitive space-ground network communication architecture based on cooperative spectrum sensing is proposed.In this thesis,we first study the feasible mode of cognitive satellite dynamic access to idle satellite authorized frequency band and terrestrial authorized frequency band.Aiming at the application of cognitive radio technology in future broadband satellites,this thesis proposes a cognitive space network communication architecture based on cooperative spectrum sensing.This communication architecture enables multiple nodes to access the satellite network fairly,while meeting the need for fast access between network nodes.In this thesis,the cooperative spectrum sensing mode and functional framework of the architecture are analyzed in detail.Finally,the performance of multi-antenna CR node cooperative sensing model is analyzed in detail.(2)A broadband compression sensing algorithm based on SGOMP is proposed.Aiming at the problem that the measurement processes of orthogonal matching pursuit(OMP)are easy to be disturbed by noise and the sparse information may not be available for realistic applications.A novel reconstruction algorithm called stochastic gradient orthogonal matching pursuit(SGOMP)is proposed in this thesis.The stochastic gradient approach is applied to replace least square process of well-known orthogonal matching pursuit(OMP)algorithm,and the early termination threshold(ETT)is added on the basis of the proposed algorithm to reduce the complexity of the algorithm.The cognitive space-ground network communication architecture proposed in the thesis reduces the complexity of the hardware design of the cognitive user terminal,increases the system noise margin,and significantly improves the system spectrum utilization rate.The simulation results reveal that the proposed algorithm has a higher success rate of original signal reconstruction in noisy environment.In addition,the use of the early termination threshold(ETT)can reduce the complexity of the proposed algorithm without affecting the success rate of algorithm reconstruction.