Research Of Multi-antenna Receiving Technologies In Cognitive Radio Ad Hoc Network

High-speed mobile wireless communications environment exists multipath fading, Dopplershift and multi-user interference. These effects are constraining the development of mobilecommunications technology. Compared to OFDM wireless communication system with singleantenna, multi-antenna technology has advantages of flexible control, higher signal gain, stronginterference rejection and high spatial resolution. Thus multi-antenna leads to expand exponentiallythe capacity of communication system, maximize the use of spectrum resources effectively toovercome delay spread, multipath fading and other effects. This paper focuses on the research aboutmulti-antenna receiving techniques in the OFDM wireless communication system to decrease theinfluence of multipath fading, Doppler shift and multi-user interference.Firstly, this paper focuses on the spatial spectrum estimation of array antenna technology,including beamforming technique and direction of arrival estimation technique. Detailed guidelinesof beamforming are introduced and then the performance is analyzed and compared. The principlesand implementation steps of the direction of arrival estimation algorithms are explained, includingthe MUSIC algorithm and LS-ESPRIT algorithm. The performance of beamforming algorithms andDOA estimation algorithms are verified respectively, and then the simulation analysis andcomparison are shown.Secondly, the existence of multipath fading in OFDM wireless communication system, wepropose a multipath signal receiving method based on joint DOA estimation and beamforming. Thereceiving method uses antenna array technology in OFDM receiver, applying the techniques ofDOA estimation and beamforming to separate multipath signals and then extract the main path. Themethod is simulated in MATLAB simulation platform. Simulation results show that the OFDMreceiving end has a higher diversity gain due to eliminate the effects of multipath effectsfundamentally. Thus, the method has a better performance in OFDM wireless communicationsystem.Finally, the paper focuses on the parameter estimation in OFDM system using antenna array,including joint angle-frequency estimation algorithm and the joint angle-delay estimation algorithm.These two algorithms are simulated in MATLAB simulation platform respectively, and the analysisand comparison of the performance of the algorithm are shown.