The Design And Implementation Of Ofdm Baseband Communication System

This paper studies the basic principle of orthogonal frequency division multiplexing (OFDM), and IEEE802.11a physical layer protocol, designs OFDM baseband communication system, completes the simulation on Matlab platform and, ultimately, implements the system based on field programmable gate array (FPGA).Firstly, the key technology of the OFDM modulation and demodulation has been analyzed, and the system implementation has been proposed. OFDM baseband system is divided into two parts:a transmitter and a receiver, transmitter is responsible for completion of the data modulation, which modules the bit stream sent by the host computer into OFDM symbols, and then sends them to the RF front-end to transmit; the receiver has to complete the data demodulation, which demodulates the received OFDM symbols into bit stream, the receiver also completes symbol synchronization, that is, to find the correct location of symbols, removing the symbol frequency deviation.Secondly, the detailed design of each sub-module has been proposed. The transmitter is divided into a data-generating module, a pilot-inserting module, an IFFT and cyclic prefix-inserting module, and an OFDM-frame-making module; the receiver is mainly divided into an AGC (automatic gain control) modules, a synchronization module, a frequency-offset-compensating module, a channel-estimation module and a decoding module. Further, in order to make sure of the correction of the transmission and reception timing, the master control unit module is also designed to control the state of the transmitter and receiver.Finally, the OFDM baseband communication system has been successfully built based on the FPGA development platform. Also, this paper designs a system-test program which uses the computer to generate the data source to test the system. The test results show that the system is reliable and correct.