Broadband Wireless Access (BWA) systems have gained a lot of attention in the industry for providing flexible and easy deployment solutions to high-speed wireless communications technology such as WiMAX. Orthogonal Frequency Division Multiplexing (OFDM) system is one of the technologies that can offer BWA efficiently. However, there are certain problems with the OFDM system that need to be solved. In this thesis, a system based on OFDM scheme and principles has been designed to deliver high-speed mobile broadband services with great efficiency and reliability, with emphasis on resolving the problems that current OFDM systems face.  A comprehensive investigation of OFDM systems are performed. We highlight and analyze in detail the current problems with channel estimation, synchronization and resource allocation of OFDM systems. We propose a new efficient channel estimation technique for the OFDM technology. Furthermore, we present an enhanced synchronization technique to mitigate frequency errors from which OFDM systems normally suffer in certain multipath environment