Theories Research And Implementation Of Modulation And Demodulation For OFDM System

In order to obtain the goal of communicating information by broadband with any manner, in any place and at any moment, the future wireless communication requires the characteristics of high quality, high reliability and high transmitting rate. OFDM system is a very promising technology since it has many advantages, such as its high-efficient spectrum and ICI interference avoidance. It can also easily connect with MIMO and access technologies like FDMA, TDMA, and CDMA. Because different subcarriers can adopt different coding and modulation methods, the capacity of the channel is able to reach the optimum value.Firstly, the paper discusses characters of the wireless channel and the basic theoretics of OFDM. Multi-path fading, Doppler frequency excursion make the wireless channel complex. They are going to be analyzed in this paper. Then the paper analyzes the basic theoretics of OFDM and the function of every module in OFDM system, and simulates the wave and spectrum of OFDM signal with MATLAB software. At last, the block diagram of OFDM system is put forward.In the following chapters, the paper discuses the key technologies of OFDM system. The key technologies are the synchronization, channel estimation, and PAPR problems. This paper mainly introduces and analyzes the domestic and overseas researches and gives some methods to resolve every problem.Finally, the paper designs the hardware structure of OFDM system. In the design of OFDM system part, the paper presents rules to choose the appropriate chips and the specialitis of them, then discusses the existed problems. The frame of OFDM system is designed according to application system requirements. After considering the sender and receiver parts, the paper gives the key algorithms of the hardware design, and gives the RTL synthesized figure and timing simulative figure. At last, this paper discusses the hardware structure of this system, and analyzes the performance of it.The paper discusses OFDM system in detail, and introduces problems that may be encountered when implementing the system.