Cramer-Rao Bound For Offset Timing Estimation Of Ofdm Systems

In an orthogonal-frequency-division multiplex (OFDM) system, the problem of sampling clock synchronization and channel estimation is analyzed. In such systems, when the number of sub-carriers is large, a sampling clock frequency mismatch between the transmitter and the receiver dramatically degrades the performance. Obviously, the channel-impulse response is unknown at the receiver and also needs to be estimated. Therefore, the CRB associated with this joint estimation is theoretically evaluated. When the number of sub-carriers and the channel degree are large, very compact closed-form expressions for the CRB are obtained. Furthermore, along with the maximum-likelihood (ML) estimator, sub-optimal estimation algorithms are introduced and compared with some existing approaches and with the CRB. Keywords—Channel estimation, Cramer–Rao bound (CRB),Orthogonal-frequency-division-multiplex (OFDM), sampling clock offset estimation, very high speed digital subscriber line (VDSL).