Carrier frequency offset estimation for OFDM systems with time-varying DC Offset

Liu, Tao; Li, Hanzhang

doi:10.1186/1687-6180-2012-156

Cited by 5 publications

(3 citation statements)

References 33 publications

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“…The other distortion effects are out of the design scope of this paper. For the future research issue of time-varying DC, i.e., adopting the time-varying DC model in [20], [21], the parameters of the time-varying DC offset can be estimated and calibrated by the proposed design flow in this paper. For the purpose of training sequence design in this paper, the frequency offset BPSK and QPSK training signals are designed for the RF calibrations of the receiver and transmitter sides, respectively, which can achieve the TX/RX loopback calibration.…”

Section: Discussionmentioning

confidence: 99%

Self-Calibration of Joint RF Impairments in a Loopback Wideband Transceiver

Deng

Lee

et al. 2020

IEEE Access

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This research studied transmitter/receiver (TX/RX) wideband (WB) RF impairments, namely frequency-dependent, frequency-independent I/Q imbalances and DC I/Q offsets. A real-based parallel structure is proposed to estimate and calibrate TX/RX WB RF impairment factors. RX impairment estimation and compensation are performed first using a frequency offset BPSK training signal. Then, the TX impairments are calibrated using a QPSK training signal. The proposed methods exhibited the following successes. First, a commercial off-the-shelf (COTS) AD9371 RF module with impairments was calibrated. After TX/RX calibration, the improvement of error vector measurement (EVM) of an OFDM 64QAM test signal was approximately 9.42 dB. Second, for the Taiwan Industrial Technology Research Institute's WB RF module with impairments, the EVM of an OFDM 16QAM test signal was calibrated and increased by about 20 dB. In summary, the proposed techniques can overcome WB RF impairments and enable high-quality WB communication. INDEX TERMS Calibration procedures, DC I/Q offsets, frequency-dependent I/Q imbalance, frequency-independent I/Q imbalance, RF impairment. I. INTRODUCTION Direct up/down RF chipsets are commonly used in wideband (WB) communication systems such as the 5G mobile communication system and digital video broadcasting systems. These chipsets have advantages such as low cost, simple design, and small area. However, for direct up/down conversion, multiple RF chips and oscillation circuits induce the different impairments including I/Q imbalance, DC offset, transmitter and receiver nonlinearities, phase noise, and coupling effects. In these impairments, many studies have extensively discussed I/Q imbalance. WB communication systems incur two I/Q imbalance effects: frequency-independent and frequency-dependent I/Q imbalances. Specifically, RF local oscillators generate I and Q carriers with amplitude and phase imbalance effects, resulting in so-called frequency-independent I/Q imbalance. In WB systems, the I and Q channels have the different impulse response effects and exhibit frequency-selective distortion, which is called frequency-dependent I/Q imbalance. The associate editor coordinating the review of this manuscript and approving it for publication was Nagendra Prasad Pathak.

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Section: Discussionmentioning

confidence: 99%

Self-Calibration of Joint RF Impairments in a Loopback Wideband Transceiver

Deng

Lee

et al. 2020

IEEE Access

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“…It combines OFDM and code division multiple access (CDMA) to give advantages of both, including high data rate, high spectral efficiency, robustness to frequency selective fading, multiple access capability and narrow band interference rejection among others [2][3][4]. However, due to carrier frequency offset (CFO) both OFDMA and MC-CDMA systems suffer from inter-carrier interference (ICI) and multiple access interference (MAI), [5][6][7][8][9]. The CFO appears due to frequency difference of local oscillators in transmitter and receiver, and the Doppler shift in frequency due to motion of transmitter and/or receiver.…”

Section: Introductionmentioning

confidence: 99%

Spectral Efficiency Comparison of OFDM and MC-CDMA with Carrier Frequency Offset

Ahmed¹

2017

RADIOENGINEERING

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“…Besides, a significant spectral leakage is resulted according to the rectangular profile of fast Fourier transform filters [14]- [15], and as a consequence, extra guard bands at the edges of the spectrum are required to avoid the high out-of-band emission. Moreover, in real transmission, the impact of imperfect synchronization based on OFDM signalling, drives the system to be more sensitive to channel frequency offset (CFO) and symbol timing offset (STO) [16]- [17].…”

Section: Motivation Of This Thesismentioning

confidence: 99%

Novel 5G-Modulation Formats and Their Application in Optical Wireless Communications

Bahaaelden

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Carrier frequency offset estimation for OFDM systems with time-varying DC Offset

Cited by 5 publications

References 33 publications

Self-Calibration of Joint RF Impairments in a Loopback Wideband Transceiver

Self-Calibration of Joint RF Impairments in a Loopback Wideband Transceiver

Spectral Efficiency Comparison of OFDM and MC-CDMA with Carrier Frequency Offset

Novel 5G-Modulation Formats and Their Application in Optical Wireless Communications

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