Feedback Method for Estimation and Compensation of Carrier Frequency Offset in LTE Uplink

Long Term Evolution (LTE) is getting popularity among cellular service providers throughout the World and it is going to dominate cellular systems in coming years. According to 3GPP specifications, LTE adopts Orthogonal Frequency-Division Multiplexing (OFDM) as modulation scheme in the downlink. The problem of systems based on OFDM is that they are prone to Carrier Frequency Offset (CFO). In uplink, LTE uses Single-Carrier Frequency Division Multiple Access (SC-FDMA) instead of OFDM. The main reason of its use is the better peak-to-average power ratio performance in comparison to OFDM, a property required in uplink to increase the duration of the battery of the user device. As OFDM, also SC-FDMA suffers with the problem of CFO. In this paper, a CFO estimation method for LTE uplink is analyzed and simulated by using MATLAB. The proposed method, termed feedback method, uses demodulation reference signals to estimate the CFO. After estimation of CFO, its effect is compensated in time-domain by multiplication with a linear phase.