The Design And Research Of An OFDM Data Transmission System Based On Software Defined Radio

Because of the advantages of moderate transmitting power consumption, reasonable equipment cost and good anti-destructibility, UHF wireless communication has been used in the military communication widely. The broad-band wireless data transmission must handle the effect brought by the multi-path time-delay extending and the Doppler Shift. These negative effects are produced by time dispersion and frequency dispersion of the mobile radio channel. In recent years, Orthogonal Frequency Division Multiplexing (OFDM),as a multiplexed modulating technology, has been researched attentively for a long time since OFDM features with high efficiency of data transmission and the ability of anti time selective fading as well as frequency selective fading. Having good flexibility, the Software Defined Radio (SDR) is kernel technology in military communication fields where numerous complicated communication standards exist. This paper presents the design and research of an OFDM UHF wireless image transmission system based on the SDR technology.The OFDM is sensitive to the synchronization of the OFDM symbol and the carriers' frequency excursion. This will result in the Inter Carrier Interference (ICI), and the synchronization error of the OFDM symbols will bring the Inter Symbol Interference (ISI). The channel state estimation will also be affected seriously.A scheme of an OFDM image data transmission system based on SDR is offered going with the basic theories of SDR and OFDM introduction. And the frame of the system is also presented. In the light of the research on the channel characteristics of the mobile communication, the synchronization, the frequency excursion estimation and the channel state estimation of the OFDM technology are analyzed. Each module of the OFDM system base-band is simulated and validated.