The Design And Realization Of OFDM Baseband Modem On The Basis Of DSP

Orthogonal-Frequency-Division-Multiplexing is one of key technologies in mobile communication fields. Because of its efficient resistance on inter-symbol interference and mufti-path fading, OFDM is suitable for high rate data transmission in wireless channels, which has become an attractive technology nowadays. Because OFDM is a multiple-carriers technology supporting high rate data transmission with high spectrum efficiency, at present this technology has been used in many fields, such as wireless local network, DAB, DVB systems and so forth, which is very promising to be a core technology of the fourth generation mobile communications.The purpose of the thesis is to research the fundamental in OFDM system, to integrate and compare the current protocol of wireless communicating network, to design and implement the OFDM modem on the basis of DSP platform. The research method of this thesis is to apply and verify theory in practice, which is to take advantage of OFDM principle as guidance, to refer to the current standards of wireless networks, to establish system parameters in terms of the available environment and hardware features, to design arithmetic in baseband management, to take optimizing and simulating process, in order to evaluate the principles in theory. Eventually, by establishing OFDM modem system based on DSP evaluation platform and designing DSP software module on baseband management, to demonstrate characteristics of OFDM system and the core technologies in a further way.Firstly, the thesis analyzes fundamental and key technology of OFDM system, including arithmetical modules as IFFT/FFT modulation, convolution coding and Viterbi decoding, interleaver coding and decoding, 16QAM and QPSK coding, channel estimation method, and so forth. Then implement the overall simulating modem solution above LabVIEW platform, design modem arithmetic and estimate the capability, to deepen realization of arithmetic, to guide establishment of hardware platform and programming of DSP software codes. Eventually, by referring to current wireless network protocols, establish system parameters in terms of the available environment and hardware features, build digital intermediate frequency platform based on 6701evm with analog facilities combined, design DSP software module on baseband management, process system debugging, to realize a suite of integrated OFDM modem solution on the whole. This solution supplies OFDM arithmetics based on both 256-point IFFT/FFT and 512-point IFFT/FFT, supplies IFFT/FFT modules in both Radix-2 and Radix-4, supplies modulations according both 16QAM and QPSK, and supplies a bunch of alternative parameters in "Cosine Tapered Window". All above allow user to select and establish various OFDM systems with different performance, representing the software-in-radio concept in this solution sufficiently. All optimized modules (as IFFT/FFT, Viterbi, etc.) exploit hardware capability. Through this project we can not only realize the process of OFDM system, or the fundamental theory, but also achieve purpose of comprehending system in a further way.