The Study Of Baseband Signal Processing System Of OFDM Based On FPGA

Orthogonal Frequency Division Multiplexing(OFDM) is one of multi-carrier modulation technologies, which has advantages of high utilization and high ability of anti-multipath interference. Currently, the demand of mobilization and broad band in wireless communication is becoming greater and greater. Therefore, next-generation wireless communication system with OFDM technology as the core is drawing more attention in the industry. Physical layer based on IEEE802.11a WLAN standard is one typical application of OFDM modulation. Based on the standard, this paper does a research and design on OFDM modulation technology in the means of high-speed Ethernet linking manner.Firstly, in this work basic principles of OFDM is analysised and application of OFDM in IEEE802.11a WLAN standard is introduced.Secondly, based on IEEE802.11a and with OFDM as the core, transmitter of OFDM system is analysised and designed using hardware description language. According to the format of frame in the physical layer of IEEE802.11a WLAN standard, base-band signal processing modules such as scramble, convolutional encoding, interweaving, mapping coding, inserting pilot frequency, IFFT, cyclic protection are analysised in detail and designed. Problems of clock domain crossing and switching between different data rating are solved. Link and communication in Ethernet are implemented.In the end, the receiving module in OFDM system is analysised. Functional design and algorithm of frame synchronization and carrier synchronization and symbol synchronization are implemented. Discrete Fourier transform, discrete trigonometric function inverse transform and quantitative value computation are implemented in VHDL, and functional verification of these modules are implemented.