A novel ICI cancellation scheme to reduce both frequency offset and IQ imbalance effects in OFDM

The performance of orthogonal frequency division multiplexing (OFDM) system degrades due to intercarrier interference (ICI). Recently, a simple ICI self-cancellation scheme has been proposed to reduce ICI due to frequency offset errors. Despite its 50% throughput loss, it is very effective in cancelling ICI. However, it does not remove the constant phase error, which has a considerable influence on the error performance of the OFDM system depending on the modulation scheme used. We propose new cancellation schemes, namely adjacent conjugate symbol repetition (ASSR) and symmetric conjugate symbol repetition (SCSR), to eliminate this phase error while reducing ICI. The proposed SCSR also eliminates the in-phase and quadrature (IQ) imbalance effects completely. Analytical results show that SCSR offers an average carrier-to-interference ratio (CIR) gain of 10 dB for the normalized frequency offset of 0.1 over that of conventional scheme. We evaluate the error performance of 16-QAM with various frequency offset and IQ-imbalance impairments and demonstrate SCSR´s robustness to these impairments.