Pilot-Aided Joint Estimation of Doubly Selective Channel and Carrier Frequency Offsets in OFDMA Uplink With High-Mobility Users

In this paper, we propose a novel pilot-aided joint channel and carrier frequency offset (CFO) estimation method for orthogonal frequency-division multiple access (OFDMA) uplink systems with users operating in time- and frequency-selective (doubly selective) fading environments. We use Bernstein basis polynomials (BBPs) to capture rapid time variations of the channel, which avoids the identifiability issue in estimating large number of actual channel coefficients. We make use of space-alternating generalized expectation-maximization maximum a posteriori probability (SAGE-MAP) algorithm for the joint estimation of CFOs and channel coefficients. The convergence properties of the proposed method is assessed and proved analytically. The exact Bayesian Cramér-Rao bound (BCRB) for the MAP estimation problem is also derived and is shown to be comparable to the mean squared error (MSE) of the proposed technique.