Based On Ieee802.11a Ofdm Baseband System With Some Modules

WLAN, a kind of local area network using wireless media, is a production of the combination ofwireless communication technology and computer networking technology. Orthogonal Frequency DivisionMultiplexing(OFDM) technology is drawing more and more attention in communication systems due toits high bandwidth efficiency and immunity to multi-path fading and it is adopted in many communicationsystems, such as Beyond-3G, WiMAX. WLAN specified by IEEE 802.11a, whose PHY adopts OFMDmodulation, can achieve a high transmit rate of 54Mbps, and IEEE802.11n, the latest draft for WLAN, canachieve a rate of 100Mbps. So it is important to research and develop a prototype which is based on OFDMtechnology.In this thesis, the principle of OFDM technology used in the WLAN standard specified byIEEE802.11a is introduced, then three practical schemes are introduced, which are based on the digitalsignal processor, FPGA or the combination of these two devices. Better performance and less cost willbe achieved by dividing the system reasonably into several modules which are implemented in the DSPand FPGA separately than by implementing in DSP or FPGA independently. Some design approaches anddesign tactics about how to design some key modules using Hardware Description Language(HDL), howto design sub-modules for TMS320C6205( a product of TI company) and the interface between DSP andFPGA. Taking the difference between DSP and FPGA into consideration, the interface and the process floware optimized for this application. The"top-down"strategy is adopted in the whole design flow.This thesis is arranged as follows: Chapter 1 briefly introduces the concept, technology and develop-ment of WLAN, as well as the history, advantages and disadvantages of OFDM technology. The basic andimportant concepts of OFDM system, including the system composition and the technologies to mitigatethe in?uence of multipath deterioration are discussed in Chapter 2. Chapter 3 introduces the standard ofIEEE802.11a. Three schemes are investigated in Chapter 4, and some design tactics, such as FFT/IFFT,Add/Remove Cyclic Prefix, influence of finite word length, are also presented in this chapter. Chapter 5describes the implementation scheme and the characteristic of TMS320C6205. Some hardware modules ofthe DSP sub-system are also introduced, then an optimization of the protocol is created. Chapter 6 givesthe simulation results of the bit error rate and the resource consumption of FPGA. In the end, Chapter 7discusses the system amelioration and some key techniques of OFDM in need of further research work.