ESPRIT-Based Carrier Frequency Offset Estimation for OFDM Direct-Conversion Receivers

Over the last years, there has been growing interest in making user terminals more efficient in terms of cost, size, and power consumption. A step forward in this direction is represented by direct-conversion receiver (DCR) architectures, which directly convert the received waveform from the radio frequency (RF) to baseband, thereby avoiding any intermediate frequency (IF) stage. One major issue of DCR devices is the presence of RF impairments, which greatly complicate fundamental receiver functions, including the synchronization task. In this paper we propose a carrier frequency offset (CFO) recovery scheme for OFDM DCRs plagued by frequency-selective In-phase/Quadrature (I/Q) imbalances. Our approach is based on the ESPRIT algorithm and relies on the transmission of a typical OFDM training preamble having a repetitive structure in the time domain. Numerical simulations indicate that the proposed scheme outperforms existing state-of-the-art alternatives at the price of a certain increase of the processing load.