LS-based joint estimation of carrier frequency offset, I/Q imbalance and DC offset for OFDM-based WLANs

In the orthogonal frequency division multiplexing (OFDM) using a direct-conversion receiver (DCR), transmission performance can be severely degraded by analog impairments. Typically the carrier frequency offset (CFO), the direct current offset (DCO) and the In-phase and Quadrature-phase (I/Q) imbalance cannot be efficiently or entirely eliminated in the analog domain. In this paper, a novel method for estimating the CFO, DCO and I/Q imbalance in the digital baseband domain is proposed. The proposed estimator first eliminate DCO by a real projection matrix. Then, the key contribution of the paper is that based on the reconstruction of the preamble symbols of the IEEE 802.11a/g standards, we iteratively estimate the CFO and the I/Q imbalance in a least-squares (LS) optimization fashion. Simulation results show that compared to typical existing methods, the proposed joint estimator achieves superior performance.