Realization For Physical Layer Of IEEE802.11a Based Hardware

With the fast growing of computer network, the research and application of wireless network connection has now come into more widespread use.IEEE802.11a, as the mainstream international standard of WLAN application, provides a unified physical access method for various kinds of mobile terminals.IEEE802.11a adopts Orthogonal Frequency Division Multiplexing(OFDM) method, which has now become the first choice for high-speed wireless communication because of its good anti-multipath performance and higher frequency spectrum utilization. The research on OFDM has too become one of the hot areas in communication science and technology.With the development of large-scale integrated circuit, software defined radio(SDR) has become the primary method for system design and development.DSP and FPGA chips are the main hardware platforms for SDR design. The application range of DSP and FPGA chips varies due to their distinctive characteristics.DSP chip is more suitable for computing intensive environment in order to realize complex algorithm while FPGA chip is more suitable for control intensive environment to realize lots of repeated and simple control and calculation, especially for bit level calculation. The combination of DSP and FPGA chips becomes a more efficient method for large-scale system design.This paper studies the physical layer function's hardware implementation based on IEEE802.11 standard. On the hardware development platform of integrating DSP, FPGA and USB controller chip, we have designed the function of data encoding in physical layer and OFDM modulation required by 802.11a standard using combination of C language and Verilog hardware development language. System is comprised of DSP chip as core controller, FPGA and USB chip .DSP completes the data input in physical layer and configuration of system register. The FPGA chip completes the data encoding in physical layer and OFDM modulation. USB chip works as the communication module of development platform and personal computer to complete communication with PC. The whole process can be described like that DSP chip completes the establishment of communication with PC through USB chip and waiting for the request of PC to send data. When DSP receives the sending request from PC, it starts to input data and activates the processing module of FPGA. After the completion of data processing by FPGA, the processed data will be sent to PC by USB chip.We use the comparison of operation results of hardware and software to verify the system function. Thus, C language is adopted to complete software realizing of data encoding in physical layer and OFDM modulation in the DSP simulator environment. This software works as test software of hardware system to verify whether the test results are correct or not. Through the verification results, I have found that error exists between operation results of software and operation results of hardware. After some analysis, the author believes that the error is not a functional error caused by system hardware, but a reasonable one. The hardware functionality of this system is accurate.