Abstract
Sensitivity to carrier frequency offset (CFO) is one of the biggest drawbacks of orthogonal frequency division multiplexing (OFDM) system. A lot of CFO estimation algorithms had been studied for compensation of CFO in OFDM system. However, with the adoption of direct-conversion architecture (DCA), which introduces additional impairments such as dc offset (DCO) and in-phase/quadrature (I/Q) imbalance in OFDM system, the established CFO estimation algorithms suffer from performance degradation. In our previous study, we developed a blind CFO, I/Q imbalance and DCO estimation algorithm for OFDM systems with DCA. In this article, we propose an alternative algorithm with reduced computation complexity and better accuracy. Performance of the proposed algorithm is demonstrated by simulations.
Highlights
As one of the most popular technologies for wireless communications, orthogonal frequency division multiplexing (OFDM) [1], on the one hand, has attractive advantages such as high spectrum efficiency, robustness to multi-path fading and efficient implementation based on fast Fourier transform, which make it suitable for wide-band wireless communications
It improves accuracy of I/Q imbalance estimation within the whole signal to noise ratio (SNR) range of interest. It significantly improves accuracy of dc offset (DCO) estimation with low-to-medium SNR. These improvements are achieved by compensation of DCO before estimation of carrier frequency offset (CFO) and I/Q imbalance, and validation of estimated I/Q imbalance according to its practical range
3 Eigen-decomposition based estimator (EDE) In our recent study [13], we proposed an eigen-decomposition based blind estimator (EDE) for joint estimation of CFO, I/Q imbalance and DCO in OFDM systems
Summary
As one of the most popular technologies for wireless communications, orthogonal frequency division multiplexing (OFDM) [1], on the one hand, has attractive advantages such as high spectrum efficiency, robustness to multi-path fading and efficient implementation based on fast Fourier transform, which make it suitable for wide-band wireless communications. We further study joint estimation of CFO, I/Q imbalance and DCO in OFDM systems and propose an alternative blind algorithm, EDE with time domain average (TDA-EDE). The cost function in (3) is the same as that proposed in [5] except that the received signal rN (m) is replaced by the combination R3(m)a3 It had been illustrated in [13] that fEDE(ν, a3) achieves its minimum when ν = ± ε and a3 = g3 with g3 being the optimal weighting vector that can completely cancel the I/Q imbalance and DCO in received signal [13]. Based on the constructed cost function, estimation of CFO and optimal weighting factor can be achieved by the following optimization approach as (ε, g 2) = arg min fTDA−EDE(ν, a2). G2 obtained under such case has little influence of average performance
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