| Orthogonal frequency division multiplexing with cyclic prefix(CP-OFDM)is the most widely used wireless communication system waveform.However,the insertion of CP occupies time-frequency resources and causes resource waste.The proverbial filter bank multicarrier(FBMC)system has time-frequency localization feature prototype filter,so it has higher spectral efficiency and also strong robustness against dispersive channels.Now,it's regarded as an alternative modulation scheme to CP-OFDM.In contrast to the CP-OFDM systems,the subcarrier functions in FBMC are orthogonal in the real field only,but not the complex-field orthogonality.Channel estimation is a difficult problem in FBMC system because of the intrinsic virtual part interference.Therefore,it is necessary to find a new set of real-valued zero correlation zone(ZCZ)sequences or other channel estimation methods for FBMC systems.In addition,when the amount of network data increases dramatically,multiple-input and multiple-output(MIMO)structure will be used to improve the data throughput of the system.In this thesis,there are several novel algorithms for channel estimation of MIMO-FBMC,and several improved algorithms are proposed in pilot design and receiver structure.In addition to the theoretical study of channel estimation methods for MIMO-FBMC systems,this thesis will also build a 4?4 MIMO-FBMC system on universal software defined radio(USRP)to test the system performance and verify the effectiveness of our proposed channel estimation methods that have been admitted widely.Firstly,this thesis introduces the framework and basic principles of MIMO-FBMC systems,and then describes the general steps of channel estimation.Then the existing channel estimation methods based on pilot frequency for MIMO-FBMC system are reviewed,and the shortcomings and the aspects to be improved are pointed out.Before designing the pilot frequency structure,the internal interference of the MIMO-FBMC system from the data itself was analyzed according to the characteristics of the system structure,and then the constraints of the pilot frequency design were obtained by considering the system structure,internal interference and multiple access mode.Finally,based on the above difficulties,this thesis designs a real-valued preamble structure which satisfies all the constraints.Secondly,the inherent interference of the FBMC system can not be completely eliminated from the perspective of transmitting pilot design,and more protection intervals are used to counter the inter-symbol interference,which results in a certain amount of spectrum waste.Therefore,this thesis starts with the structure of the receiver,focuses on the analysis of the inherent interference of the FBMC system,and then the channel estimation of MIMO-FBMC system is improved by designing pure real-valued pilot structure in the frequency domain and adding iterative feedback structure to the receiver to further eliminate inter-system interference.Finally,in the academic circles,there are few demonstrations on the MIMO-FBMC system testbeds,and its experimental degree is not as advanced as the theoretical research.Based on the project requirements,this thesis will build a MIMO-FBMC system experimental testbed,and verify the effectiveness of the complex training sequence decomposition(CTSD)channel estimation method proposed by our team on it. |
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