High performance receiver design for OFDM based wireless communications systems

High Performance Receiver Design for OFDM Based Wireless Communications Systems Recent market analysis and predictions show that in near future the wireless internet access will be more than the wired internet access technologies currently in use. The technologies such as Voice over IP, Video on Demand systems rises a big demand on communication speeds, and therefore researchers spends a great effort to cope up with all these, in particularly the demands of multimedia and multiple access data rates. This dissertation is dedicated to study the physical layer of OFDM-based Hiperlan/2 (IEEE 802.11a) standards and develop receiver architecture to increase the physical layer performance of OFDM systems. For this purpose, frequency domain channel equalizer and its alternative method in particular CMF-DFE are examined and simulated, because time domain equalizers are more successful in combining the multi-path energy of an ISI channel. In order to increase the performance of the time domain equalizer several techniques are proposed in particular coding, the Walsh-Hadamard Transform and antenna diversity. The remaining ISI effect of the CMF-DFE is cancelled when WHT and antenna diversity are used. The study also compares the Walsh-Hadamard Transform with error correction coding techniques, which mainly concludes for coding. However, if a certain level of error is tolerated, the Walsh-Hadamard Transform would be preferred, since it does not affect the data rate. This dissertation also involves studies on frame synchronization and carrier frequency offset estimation and compensation for an OFDM receiver. For this purpose, based on time domain correlation, a method having three stages is developed and simulated. The results show that its performance and frequency offset range are better than P.H. Moose's method mentioned in literature. Key Words: OFDM, Hiperlan/2, IEEE802.11a, Wireless Network, Channel Estimation, Channel Equalization, CMF-DFE vn