Study of the Sensitivity of the OFDM Wireless Systems to the Carrier Frequency Offset (CFO)

Mohseni, Saeed; Matin, Mohammad A.

doi:10.5121/ijdps.2013.4101

“…The CFO destroys the orthogonality relationship between the subcarriers, creating intercarrier interference (ICI) in OFDM systems. ICI is a frequency mismatch between the transmitter and receiver, and this frequency mismatch leads to severe performance degradation in OFDM wireless systems [5,6]. This problem is even more serious in the OFDM-based UWA systems.…”

Section: Introduction *mentioning

confidence: 99%

Proposal for a Doppler Shift Compensation Method Using Non-Uniform FFT with Pilot Carrier Frequency for OFDM-Based Underwater Acoustic Communication Systems

2023

JST: SSAD

0

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In this paper, we propose a method that uses the non-uniform Fast Fourier Transform (FFT) to compensate for Doppler frequency shifts in orthogonal frequency division multiplexing (OFDM) based underwater acoustic (UWA) communication systems. To estimate the Doppler frequency shift, the paper proposes using a pilot carrier frequency (PCF) that is identified by transmitting with greater power in the frequency domain compared to other subcarriers. This identifier helps estimate both the Doppler frequency shift and the channel. The paper proposes estimating and compensating for the Doppler frequency shift in two steps: Step 1 performs coarse frequency synchronization, where the Doppler frequency shift is determined by using PCF signal. The Doppler shift correction is obtained by re-sampling the received signal, and then interpolating re-sampled signal. However, the Doppler shift compensation in the step 1 cannot correct the phase distortion of the measured PCF signal. Therefore, performing step 2, known as fine frequency synchronization, is necessary. In this step, the correction for the phase distortion is determined based on the phase difference between the two consecutive OFDM signals in one frame. The remaining Doppler frequency shift is adjusted based on the phase deviation, using the non-uniform FFT. By using the non-uniform FFT, the complexity of the ICI compensation is significantly reduced, and the quality of Doppler shift compensation is improved. The experience results show that the transmitted text will be decoded correctly by using the proposed technique

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“…The CFO destroys the orthogonality relationship between the subcarriers, creating intercarrier interference (ICI) in OFDM systems. ICI is a frequency mismatch between the transmitter and receiver, and this frequency mismatch leads to severe performance degradation in OFDM wireless systems [5,6]. This problem is even more serious in the OFDM-based UWA systems.…”

Section: Introduction *mentioning

confidence: 99%

Untitled

2023

JST: SSAD

0

View full text Add to dashboard Cite

In this paper, we propose a method that uses the non-uniform Fast Fourier Transform (FFT) to compensate for Doppler frequency shifts in orthogonal frequency division multiplexing (OFDM) based underwater acoustic (UWA) communication systems. To estimate the Doppler frequency shift, the paper proposes using a pilot carrier frequency (PCF) that is identified by transmitting with greater power in the frequency domain compared to other subcarriers. This identifier helps estimate both the Doppler frequency shift and the channel. The paper proposes estimating and compensating for the Doppler frequency shift in two steps: Step 1 performs coarse frequency synchronization, where the Doppler frequency shift is determined by using PCF signal. The Doppler shift correction is obtained by re-sampling the received signal, and then interpolating re-sampled signal. However, the Doppler shift compensation in the step 1 cannot correct the phase distortion of the measured PCF signal. Therefore, performing step 2, known as fine frequency synchronization, is necessary. In this step, the correction for the phase distortion is determined based on the phase difference between the two consecutive OFDM signals in one frame. The remaining Doppler frequency shift is adjusted based on the phase deviation, using the non-uniform FFT. By using the non-uniform FFT, the complexity of the ICI compensation is significantly reduced, and the quality of Doppler shift compensation is improved. The experience results show that the transmitted text will be decoded correctly by using the proposed technique.

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“…Specifically, the CFO compromises the orthogonality between subcarriers, causing mutual interference of subchannels, i.e., the Intercarrier Interference (ICI), and so severely degrades the performance. Therefore, utmost care is given to CFO estimation and compensation in OFDM wireless systems [6][7][8][9]. However, following the CFO compensation, still some residual CFO remains, which can degrade the OFDM transmission performance [1].…”

Section: Introductionmentioning

confidence: 99%

Suppressing the OFDM CFO‐Caused Constellation Symbol Phase Deviation by PAPR Reduction

Lipovac

¹

,

Lipovac

²

,

Njemčević

³

2018

Wireless Communications and Mobile Computing

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The well-known major drawbacks of the Orthogonal Frequency-Division Multiplexing (OFDM), namely, the transmitter versus receiver Carrier Frequency Offset (CFO), and the Peak-to-Average Power Ratio (PAPR) of the transmitted OFDM signal, may degrade the error performance, by causing Intercarrier Interference (ICI), as well as in-band distortion and adjacent channel interference, respectively. Moreover, in spite of the utmost care given to CFO estimation and compensation in OFDM wireless systems, such as wireless local networks or the mobile radio systems of the fourth generation, e.g., the Long-Term Evolution (LTE), still some residual CFO remains. With this regard, though so far the CFO and the PAPR have been treated independently, in this paper, we develop an Error Vector Magnitude (EVM) based analytical model for the CFO-induced constellation symbol phase distortion, which essentially reveals that the maximal CFO-caused squared phase deviation is linear with the instantaneous (per-OFDM-symbol) PAPR. This implies that any PAPR reduction technique, such as simple clipping or coding, indirectly suppresses the CFO-induced phase deviation, too. The analytically achieved results and conclusions are tested and successfully verified by conducted Monte Carlo simulations.

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Study of the Sensitivity of the OFDM Wireless Systems to the Carrier Frequency Offset (CFO)

Cited by 6 publications

References 8 publications

Proposal for a Doppler Shift Compensation Method Using Non-Uniform FFT with Pilot Carrier Frequency for OFDM-Based Underwater Acoustic Communication Systems

Proposal for a Doppler Shift Compensation Method Using Non-Uniform FFT with Pilot Carrier Frequency for OFDM-Based Underwater Acoustic Communication Systems

Untitled

Suppressing the OFDM CFO‐Caused Constellation Symbol Phase Deviation by PAPR Reduction

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