Abstract
This paper presents a novel low-complexity sequential, blind, pilot-assisted estimator for the sampling frequency offset (SFO) and the carrier frequency offset (CFO), for orthogonal frequency-division multiplexing (OFDM) communications. The proposed algorithm processes the received subcarriers to obtain a cost function which depends only on a single unknown parameter at a time, either the SFO or the CFO, as well as on a specifically designed auxiliary parameter, while ignoring the noise. Then, by computing the cost function at a few selected values of the auxiliary parameter, an explicit estimator for each unknown parameter is derived, thereby avoiding the need for a search. To the best of our knowledge, this is the first time such a deterministic approach is applied to the joint estimation of the SFO and the CFO. Moreover, the proposed estimator does not require knowledge of the channel coefficients at the pilot subcarriers, and achieves good performance with a relatively small number of pilot symbols, which results in a low computational complexity. Simulation results show that at low computational complexity, there are many scenarios in which the new estimator achieves smaller estimation errors compared to other existing methods.
Highlights
Orthogonal frequency-division multiplexing (OFDM) is a multicarrier modulation scheme which is widely used in current wireless and wireline communications standards, and is a major candidate for future communications networks [1], [2]
The work in [6] derived an efficient blind carrier frequency offset (CFO) estimator using three values of a cost function obtain by oversampling a single OFDM symbol and applying a time-shift followed by downsampling, which results in two separated OFDM symbols with which the cost function is generated
The processing applies designed phase shifts to the processed samples, modifying and extending the idea of [6] for CFO estimation, which originally used a cost function obtained from a single OFDM symbol, which sums over all frequency domain values of a function of the oversampled received symbol and a test signal, to joint sampling frequency offset (SFO) and CFO estimation using only specific subcarriers over two subsequent symbols
Summary
Orthogonal frequency-division multiplexing (OFDM) is a multicarrier modulation scheme which is widely used in current wireless and wireline communications standards, and is a major candidate for future communications networks [1], [2]. The processing applies designed phase shifts to the processed samples, modifying and extending the idea of [6] for CFO estimation, which originally used a cost function obtained from a single OFDM symbol, which sums over all frequency domain values of a function of the oversampled received symbol and a test signal, to joint SFO and CFO estimation using only specific subcarriers over two subsequent symbols. Our cost functions are completely different from those used in previous joint SFO/CFO estimation works, e.g., in [9], as is evident from the numerical evaluations: There are many channels in which our newly proposed estimator is superior to the baseline scheme of [9] and there are channels in which the baseline scheme is superior to our proposed estimator It follows that the main novelty lies in the proposed processing which facilitates a simple extraction of the SFO and the CFO, while maintaining an overall low computational complexity. For an arbitrary set A, we use |A| to denote its cardinality
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