Application Research Of OFDM In Wi-Fi

With the rapid development and wide application of broadband wireless communication, own to its convenience and flexibility, Wi-Fi has become an necessary wireless access in people’s daily life. Nowadays the fifth generation Wi-Fi Who has a higher transmission rate, a larger system capacity and a wider coverage has been born. As a key technology in physical lay of IEEE 802.11 series standards, OFDM not only enhance the ability to combat multipath fading deterioration, but also realize a higher spectral efficiency. However, OFDM cannot solve the problem of radio frequency resources shortage, but MIMO technology has great potential in the term of channel capacity. So the combination of OFDM and MIMO technology is still one of the hottest areas of today’s wireless communications researches.Firstly, this paper introduces the basic principles of traditional OFDM, MIMO and MIMO-OFDM briefly. Makes a detail analysis for the physical layer of IEEE 802.11 standard in which OFDM is a key technology, and do performance simulation and analysis of single antenna and multiple antenna OFDM system respectively under different conditions consist of modulation, channel type and number of antenna by MATLAB platform, following by some views for the practical parameters choice. Secondly, a specific study on channel estimation techniques which is an important part of OFDM technology in the IEEE 802.11 has been proposed. Through the simulation analysis of each BER curves of traditional channel estimation algorithm, verifies the conclusion that DFT algorithm has better estimation accuracy compared to LS algorithm, but interior to MMSE algorithm, however, algorithm complexity reverses the order. Finally, This paper mainly introduced pilot based and training sequence based channel estimation, comes up with MIMO-OFDM channel estimation scheme suitable for IEEE 802.11 protocol, and gives related performance simulation. Then, Energy leakage in the practical application of traditional DFT algorithm which causes performance deterioration has been confirmed, so an improved DFT algorithm is put forward which uses a new threshold and verdict method to overcome this problem, its simulation proved the effectiveness of the algorithm.