Variable Sub-carrier in OFDM to Reduce the ICI Due to Carrier Frequency Offset and IQ Imbalance

Orthogonal frequency division multiplexing (OFDM) has become one of the promising technologies for the next-generation communication systems to support high-data-rate transmission. However, conventional OFDM systems are sensitive to both the carrier frequency offset (CFO) and the in-phase and quadrature (IQ) imbalance, which cause the inter-carrier interference (ICI) and greatly degrade the performance. In this paper, we propose a novel OFDM system using a permutated on-off-keying quadrature-phase-shift-keying (OOK-QPSK) modulation to reduce the ICI. The performance analysis and the simulation results show the proposed OFDM system performs better than conventional OFDM systems using QPSK modulation under the impact of both the CFO and the IQ imbalance.