| Wireless Local Area Network (WLAN) has the characteristic of both radio communication and computer network. WLAN has become an important part of personal communication, provides the demand of people with wideband wireless network anytime and anywhere, and will have widespread application in the reality and future of social life. The establishment of the IEEE802.11 standard is the milestone of WLAN. The IEEE802.11b standard has become one of the current mainstream WLAN standards, and the products according to this standard occupy a large market share.This thesis puts great emphasis on the modulation and demodulation principle of the Complementary Code Keying (CCK) and the hardware implementation based on FPGA. Being the key modulation technology in the EEEE802.11b standard, the CCK code has an excellent correlation characteristic. So the products according to this technology could not only transmit high-speed data but also overcome the multipath effects effectively. Beginning with a briefly introduction of the structure and characteristics of WLAN, the thesis researches the IEEE802.11b standard, especially the structure and specification of the physical layer in base band. Then this thesis describes the characteristics of the CCK code in detail, and it also focuses not only on the principle of the CCK modulation based on the basic CCK code word sets but also on the principle of the CCK demodulation based on Fast Walsh Translate Block (FWTB) in the mode of 11Mb/s. Moreover, by means of simulating the design scheme of the modulation and demodulation in Matlab, correct theoretical data are obtained and the feasibility of the scheme is confirmed. After that, under the ISE6.2 development environment of Xilinx, the modulation and demodulation systems are designed and programmed in hardware description language Verilog HDL in FPGA, respectively. Finally functional simulation of the whole system is carried out in ModelSim. The comparison between theoretical analysis and simulation results proves the correctness of the design work, and the system performs well.The CCK modulation and demodulation system based on FPGA owns a lot of characteristics, such as high integrity, great stability, the ability to update the software on line and so on. The research results in this thesis could provide the foundation to design higher performance and higher integrity baseband WLAN chip in the future. |
