Abstract
Sampling Clock Offset (SCO) estimation is an important issue in Orthogonal Frequency-Division Multiplexing (OFDM) systems because sampling frequency mismatch between the transmitter and the receiver may severely degrade the system performance due to the loss of orthogonality between the subcarriers. SCO estimation in mobile environment is quite challenging since channel variation leads to an additional phase rotation that masks the SCO effects. However, most of the existing techniques rely on the assumption of a time-invariant channel and become considerably inaccurate in a mobile environment. In this paper, we propose an improvement to an existing pilot-aided SCO estimator aiming to provide robustness against channel variations. Performance was evaluated through simulations in an ISDB-T (Integrated Services Digital Broadcasting Terrestrial) compliant system and the results have shown a considerable improvement for all ranges of signal-to-noise ratios, specially for higher Doppler spread.
Highlights
Orthogonal Frequency-Division Multiplexing (OFDM) is a multi-carrier technique that achieves high spectrum efficiency by dividing data into closely spaced subcarriers which constitute parallel orthogonal data-streams
We provide in this paper a deeper and a more detailed analysis of the proposed methods, including a convergence rate assessment through simulations as well as bit error rate (BER) results, which were not evaluated in [1]
A) Fast-Fading Channel: If the channel varies within one OFDM symbol, the frequency domain received signal can be represented by zl,k = al,kHl,k + ηl,k + ηICI;l,k
Summary
Orthogonal Frequency-Division Multiplexing (OFDM) is a multi-carrier technique that achieves high spectrum efficiency by dividing data into closely spaced subcarriers which constitute parallel orthogonal data-streams. It has been adopted in several broadband communication systems such as digital TV standards DVB [2] and ISDB [3]. Pre-FFT methods have been proposed in [9], [10] They perform a non data aided estimation by relying on the statistical particularities of the time-domain OFDM signal, typically using the cyclic prefix. Based on a conventional pilot-aided SCO estimator, we propose two new algorithms that mitigates the perturbations of frequency-selective time-varying channels.
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