Simultaneous Carrier Frequency Offset Estimation for Multi-Point Transmission in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) combining with the coordinated multi-point (CoMP) transmission technique has been proposed to improve performance of the receivers located at the cell border. However, the inevitable carrier frequency offset (CFO) will destroy the orthogonality between subcarriers and induce strong inter-carrier interference (ICI) in OFDM systems. In a multi-point transmission system, the impact of CFO is more severe because of the mismatch of carrier frequencies among multiple transmitters. To relieve the performance degradation, CFO estimation and compensation is essential. For simultaneous estimation of multiple CFOs, the performance of conventional CFO estimation schemes is significantly degraded by the mutual interference among the signals coming from multiple transmitters. In this work, we propose a maximum likelihood (ML)-based estimator for simultaneous estimation of multiple CFOs, and design the training sequences that are robust to the variation in CFOs. According to the simulations, our scheme can eliminate the mutual interference effectively, approaching the mutual interference-free performance.