Based On Cofdm Wireless High-speed Digital Image Transmission System Sender Studied

In recent years, OFDM (Orthogonal Frequency Division Multiplexing)--a multi-carrier modulation technology, has gradually replaced Single-carrier Spread-spectrum technology (e.g. CDMA) and become the core technology for the next generation mobile communication system. OFDM distributes high-rate data to multiple sub-channels by serials-parallel conversion and can be regarded as a kind of modulation technology as well as a kind of multiplexing technology. OFDM has many advantages: besides high bandwidth efficiency, it can combat multi-path effect, frequency selective fading, inter-symbol interference and it is easy to be implemented by applying IFFT and FFT as modulation and demodulation methods.In the Project"Wireless High-rate Transmission System for Digital Image", the efficient bandwidth of the transmission system is about 24MHz and one terminal is moving at a very high speed, which leads to the high requirements of the whole system design. COFDM (Coded Orthogonal Frequency Division Multiplexing) is applied in the project.Wireless channel is so complicated that the frame structure is crucial to the system performance. This paper designs the frame structure according to the three important parameters of OFDM system, therefore the system can adapt to the complex wireless channel. This paper will discuss the method of OFDM systems design in detail.This paper focuses on the design of base-band and IF in sending terminal. The Main functions contained in the base-band part are channel coding, sub-carrier mapping, digital modulation and OFDM modulation, etc. Based on OFDM algorithm and IEEE 802.11a standard, some designs have been modified and optimized according to the required specifications. After simulation, the design has been downloaded to chips and the whole sending terminal link has been proved to meet the design requirements. The main contents of this article are as follows:(1) The introduction of OFDM technology and FPGA hardware theory knowledge,(2) The designs method of the OFDM systems parameter and the frame structure, (3) The algorithm design and the FPGA realization of the OFDM baseband sending systems,(4) The realization of OFDM systems IF sending and receiving terminals.