Joint Estimation of Carrier Frequency Offset and Channel Complex Gains for OFDM Systems in Fast Time-Varying Vehicular Environments

Abstract

In this paper, the physical nature of the radio-channel is considered by using an $L$-path channel model to developing an algorithm for OFDM systems operating in fast time-varying vehicular environment. Assuming the path delays are known, a novel iterative pilot-aided algorithm for joint estimation of multi-path Rayleigh channel complex gains and Carrier Frequency Offset (CFO) is introduced. Each complex gain time-variation, within one OFDM symbol, is approximated by a Basis Expansion Model (BEM) representation. An auto-regressive (AR) model is built for the parameters to be estimated (the AR model for the BEM coefficients is based on the Jakes process). The algorithm performs recursive estimation using Extended Kalman Filtering. Hence, the channel matrix is easily computed, and the data symbol is estimated with free inter-sub-carrier-interference (ICI) when the channel matrix is QR-decomposed. It is shown that only one iteration is sufficient to achieve the performance of the ideal case where knowledge of channel response and CFO is available.