Joint Estimation of Carrier and Sampling Frequency Offsets in the Uplink of Multiuser OFDM Systems

This paper considers the joint estimation of the carrier frequency offset (CFO) and sampling frequency offset (SFO) in the uplink of multiuser orthogonal frequency division multiplexing systems, where the received signal at the base station is a mixture of all users' signals and each user is affected by different frequency offsets. Usually, users' separation is needed to cope with this challenging multi-parameter estimation problem. Conventional methods adopt the zero-forcing criterion, which will lead to noise enhancement. To overcome this problem, a novel joint CFO and SFO estimation algorithm is proposed. We use the QR decomposition to achieve users' separation, and the successive interference cancellation technique is employed to estimate the frequency offsets of different users. To further improve the estimation accuracy, the minimum variance unbiased estimator is exploited. Numerical results show that the proposed algorithm offers better performance than existing methods in terms of mean squared error and bit error rate .