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Effects of Channel Estimation Error in the Presence of CFO on OFDM BER in Frequency-Selective Rayleigh Fading Channels
"... Abstract — In this paper, we study the effects of channel estimation error on the bit-error-rate (BER) of orthogonal frequency division multiplexing (OFDM) systems in frequency-selective slowly Rayleigh fading channels. Due to the additive white Gaussian noise (AWGN) and the intercarrier interferenc ..."
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Abstract — In this paper, we study the effects of channel estimation error on the bit-error-rate (BER) of orthogonal frequency division multiplexing (OFDM) systems in frequency-selective slowly Rayleigh fading channels. Due to the additive white Gaussian noise (AWGN) and the intercarrier interference (ICI) caused by the residual carrier frequency offset (CFO), the channel estimation based on the training symbols is not perfect. We characterize the performance degradation resulting from imperfect channel state information (CSI) by deriving the BER formulas for BPSK, QPSK, 16-QAM, and 64-QAM modulation schemes. The derived BER formulas contain no numerical integrals and can be evaluated easily and accurately. Simulation results validate the correctness of our theoretical analysis. Index Terms — Orthogonal frequency division multiplexing, channel estimation, carrier frequency offset, frequencyselective Rayleigh fading, bit-error-rate, performance analysis I.
Phase Noise and Carrier Frequency Offset in OFDM systems: Joint Estimation and Hybrid Cramér-Rao Lower Bound
"... Abstract—In this paper, a new iterative pilot-aided algorithm based on expectation conditional maximization (ECM) for joint estimation of Wiener phase noise (PHN) and carrier frequency offset (CFO) in orthogonal frequency division multiplexing (OFDM) systems is proposed. Next, a new expression for t ..."
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Abstract—In this paper, a new iterative pilot-aided algorithm based on expectation conditional maximization (ECM) for joint estimation of Wiener phase noise (PHN) and carrier frequency offset (CFO) in orthogonal frequency division multiplexing (OFDM) systems is proposed. Next, a new expression for the hybrid Cramér-Rao lower bound (HCRB) for joint estimation of PHN and CFO in OFDM systems is derived. Numerical results show that the proposed estimator outperforms existing algorithms in terms of mean square error while performing close to the derived HCRB at moderate PHN variances. Moreover, the proposed estimator is found to be computationally more efficient than existing algorithms since it jointly estimates PHN and CFO in a few iterations. I.
Channel, Phase Noise, and Frequency Offset in OFDM Systems: Joint Estimation, Data Detec- tion, and Hybrid Cramér-Rao Lower Bound
"... Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely impact the performance of orthogonal frequency division multiplexing (OFDM) systems, since they can result in inter carrier interference and rotation of the signal constellation. In this paper, we propose an expectation co ..."
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Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely impact the performance of orthogonal frequency division multiplexing (OFDM) systems, since they can result in inter carrier interference and rotation of the signal constellation. In this paper, we propose an expectation conditional maximization (ECM) based algorithm for joint estimation of channel, PHN, and CFO in OFDM systems. We present the signal model for the estimation problem and derive the hybrid Cramér-Rao lower bound (HCRB) for the joint estimation problem. Next, we propose an iterative receiver based on an extended Kalman filter for joint data detection and PHN tracking. Numerical results show that, compared to existing algorithms, the performance of the proposed ECM-based estimator is closer to the derived HCRB and outperforms the existing estimation algorithms at moderate-to-high signal-to-noise ratio (SNR). In addition, the combined estimation algorithm and iterative receiver are more computationally efficient than existing algorithms and result in improved average uncoded and coded bit error rate (BER) performance.