Carrier Frequency Offset Estimation Based on Tracking Reference Signal in 5G

Abstract

In OFDM-based wireless communication systems, carrier frequency offset (CFO) has been one of the important factors that impair the communication performance. Carriers placed as orthogonal to each other lose their orthogonality by being affected from frequency shifts due to differences in crystals at the receiver and the transmitter or due to channel effects. For this reason, estimators are used to determine carrier frequency differences. To this aim, CFO is estimated using pilot signals placed in an OFDM block. In this work, the Cramer-Rao lower bound (CRLB) is derived for CFO estimation based on the tracking reference signal (TRS) used in 5G standards. In addition, maximum likelihood and least squares based CFO estimators are investigated for the TRS proposed in the literature and 3GPP contribution reports. Finally, by using these estimators, a new estimator with enhanced performance is proposed. Keywords—Carrier frequency offset, estimator, tracking reference signal, 5G