Research And Design Of High-rate Modem Based On Ofdm

Shortwave has many significant advantages such as small transmitting power, long-distance communication without relay station, and maintenance of low-cost. It can realize not only fixed-point communication but also mobile communication at vehicles and ships with simple equipment. Shortwave communication is widely used in the military communications thanks to all of those values. However, in modern war, the information of exchange and processing is very large, and the shortwave communication is fronted to its bottlenecks in modern military communication because of its narrow-frequency band, small capacity etc. It is possible to solute this bottlenecks thanks to the development of Orthogonal Frequency Division Multiplexing (OFDM) technique.Orthogonal Frequency Division Multiplexing (OFDM) technology has been broadly applied in wireless LANs ,digital Audio/Video broadcasting and digital TV Because of its various advantages such as robust characteristic under multipath environment and high speed transmission rate. Modern shortwave communication is widely used in long distance communications, owing to its advantages such as low cost, convenience to be generated and strong resistance to damage. One development trend of shortwave communication is to increase the transmission rate in the basis of assuring a certain BER performance, in order to meet the rising requirements. Therefor, it is very signifcative to apply OFDM in high speed Shortwave communication.This paper introduced the basic principles of OFDM, and then ,studied the key technologies of OFDM .From the practical application, this thesis is to design a shortwave high-rate modem for OFDM. This system can be used to enhance the data transmission rate and anti-interference ability of shortwave communication. The scheme of DSP+FPGA is used in this design. DSP works as the core of the system to modulate and demodulate OFDM signals and deal with signal processing algorithms. FPGA is used to realize system logic control and resource allocation to provide access to peripherals for DSP. System is working in full-duplex mode. Working parameters can be configured by keyboard or serial interface and the LCD displays the work state.