Joint Estimation of I/Q Imbalance and Carrier Frequency Offset for OFDMA Systems

The orthogonal frequency division multiplexing (OFDM) system and OFDM-based systems are very useful and common in modern communications. They have been adopted in many standards. However, OFDM-based systems are sensitive to some non-idealities caused by the direct-conversion receivers at analog front-end. In this thesis, we focus on two effects, carrier frequency offset (CFO) and in-phase and quadrature-phase (I/Q) imbalance. The CFO and I/Q imbalance destroy the orthogonality among subcarriers and result in inter-carrier interference(ICI), which would seriously degrade the performance of the system. So, estimation and compensation of these effects are important. In the past, the problem of CFO estimation in orthogonal frequency division multiple access (OFDMA) systems have been studied by a number of researchers. In particular, the MUSIC estimator and ESPRIT estimator have been proposed for comb-type OFDMA systems. In this thesis, based on the MUSIC and ESPRIT methods, we propose two I/Q imbalance estimators and joint estimation of I/Q imbalance and CFO. In addition, we also extend the MUSIC estimator for Hybrid OFDMA scheme, which is a combination of the comb-type and block-type OFDMA schemes. Moreover, numerical experiments are carried out to show the performance of our method.