EVM analysis of amplify-and-forward relaying under I/Q imbalance

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.