Abstract
Recently, orthogonal frequency division multiplexing (OFDM) has widely applied in wireless communications. There are many advantages in using OFDM systems such as the high effciency of bandwidth utilization and the avoidance of ISI and ICI. IEEE 802.11a provides a high rate physical layer (PHY) for operation on 5GHz band basing on the OFDM structure. In this thesis, we apply the sum-product algorithm on the structure of IEEE 802.11a to derive more reliable communications between transciver without increasing complexity in the structure. The factorization of the global function of FFT seems to be pretty complex. By visualizing the factorization with a factor graph, we can easily translate the factorization to a more simpler one. Iteratively applying sum-product algorithm in FFT to �曝d likelihood of all inputs, switching the messages by interleaver and performing the BCJR algorithm in the trellis of the convolutional code, we can decode the messages more accurately.