الفهرس Only 14 pages are availabe for public view
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Abstract
Carrier frequency offset and Doppler frequency spread cause ICI which severely degrades the performance of OFDM based systems. This thesis proposes two new ICI cancellation schemes to reduce the frequency offset sensitivity of OFDM systems. These two systems are based on conjugate repetition of the symbols at the transmitter side and conjugate multiplication of the data symbols at the output of the FFT block of the receiver. In contrast to previous ICI cancellation schemes, these two schemes displayed a more graceful degradation of BER with the increase of the frequency offset, especially for high order modulation types. For a 256-QAM system, the proposed schemes achieved up to 7 dB improvement over the best published ICI cancellation scheme at BER of 10-1 and normalized frequency offset = 0.1. The proposed ACPA-QPSK OFDM system is implemented on Spartan3A DSP 3400 device using Xilinx System Generator tool for DSP design. As a reference system, the classical BPSK CFO- Estimation and Correction (CFO-EC) technique is implemented on the same platform. The HW needed to correct CFO errors in ACPA-QPSK scheme is less than 50% of that required for a classical BPSK (CFO-EC) scheme