Joint Weighted Least-Squares Estimation of Carrier-Frequency Offset and Timing Offset for OFDM Systems Over Multipath Fading Channels

Abstract

This paper presents an algorithm for joint estimation of carrier-frequency offset and timing offset for orthogonal frequency-division multiplexing (OFDM) systems in the tracking mode. The proposed weighted least-squares algorithm derives its estimates based on phase differences in the received pilot subcarrier signals between two symbols. Moreover, the optimal weights in two different channel conditions are derived. Both analysis and simulation show that the weighted least-squares algorithm can effectively and accurately estimate the carrier-frequency offset as well as the timing offset of OFDM signals in multipath fading channels.

Robust estimation of carrier-frequency offset and timing offset for OFDMA uplink systems over multi-path fading channels

“…Besides, interference from all users will also affect the estimation accuracy. In [6], a weighted least squares algorithm is proposed to mitigate these adverse effects. The weighted least squares estimate of B m is given bŷ…”

“…In OFDMA uplink systems, the interference from all users may significantly degrade the algorithms' performance, especially in multi-path fading channels. In [6], the authors utilized the weighted least squares algorithm to mitigate the impact of multi-path fadings. However, it is difficult to acquire the proper weights in OFDMA uplink systems, since the interference is unknown to the BS (Base Station) receiver.…”

Robust Sampling Frequency Offset Estimation for OFDM over Frequency Selective Fading Channels

“…Since the focus here is the estimation of SFO, it is assumed that the symbol timing mismatch has been perfectly recovered at the receiver and coarse CFO acquisition has been successfully applied at the beginning of the reception of OFDM frame. For this purpose, many schemes are currently available in the literature [17][18][19]. During the data section, therefore, relatively small SFO and residual CFO will be present.…”

“…Since the GRC pattern is periodical every D t + 1 OFDM symbol in time direction, (18) can not be directly applied to the DRM system. In the sequel, we assume that (18) uses the pilot symbols inserted into every OFDM symbol.…”

“…(14) and the proposed scheme when DRM mode A is used and ∆ f = 10 −2 . For the sake of fairness, N s = D t + 1 is chosen for the conventional scheme (18), which uses the pilot symbols inserted into every OFDM symbol. In order to compute (19) and (20), a perfect knowledge of the CSI is assumed in the conventional scheme D. From the figure, it is observed that a slight performance degradation of the proposed scheme relative to the conventional scheme C in low SNR regions is observed, which is due to the SNR loss induced by the squaring of the complex conjugate operation in (22).…”