Orthogonal frequency division multiplexing (OFDM) is a kind of multi-carrier modulation (MCM) schemes. OFDM allows overlapping of adjacent frequency bins called subchannels with orthogonality between them. It results in higher spectral efficiency and a long symbol period compared to single-carrier schemes. OFDM uses a cyclic-prefix (CP), so OFDM is an effective transmission technique for coping with the typical impairments present in multi-path fading channels. Since residual carrier frequency error and frame offset of the OFDM system degrade the overall system performance, exact synchronization is very important to obtain better system performance.
In this thesis work, we propose a frequency offset compensation algorithm for the 16QAM OFDM system and simulate the OFDM system. To maintain the correct timing of a frame and compensate for residual carrier frequency error, we employ energy and correlation peak detection for symbol timing recovery (frame synchronization) using repeated symbols. And to correct the carrier frequency offset, we employ correction schemes using repeated symbols and CPs. For channel equalization and channel coding, we use the least mean square (LMS) equalizer, the RS-coder and the convolutional coder. For burst-mode transmission, the acquisition time of the system is very important. For fast acquisition of the equalizer we employ phase rotator. And for fast acquisition of synchronization we employ special counter for symbol timing recovery and adaptive algorithm for carrier frequency recovery. With these synchronization algorithms, we analyze the synchronization performance of system over the LMDS channel. Then we consider implementation issues for the synchronization algorithm of the OFDM system.