We analyze the EVM performance of OFDM-based relay-assisted amplify-and-forward systems in the presence of I/Q imbalance. We show analytically that the MRC detector suffers from an error floor due to mutual interference between image subcarriers. We prove analytically that a simple zero-forcing two-tap per subcarrier equalizer eliminates this error floor. Simulation results demonstrate its significant performance gain over MRC detection for different I/Q imbalance levels, SNR levels, and relay positions.
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