Frequency offset estimation in OFDM systems in presence of IQ imbalance
ICCS '02 Proceedings of the The 8th International Conference on Communication Systems - Volume 01
Frequency offset and I/Q imbalance compensation for direct-conversion receivers
IEEE Transactions on Wireless Communications
Impacts of I/Q imbalance on QPSK-OFDM-QAM detection
IEEE Transactions on Consumer Electronics
Broadband wireless access solutions based on OFDM access in IEEE 802.16
IEEE Communications Magazine
MIMO OFDM systems with digital RF impairment compensation
Signal Processing
Pilot designs for channel estimation of MIMO OFDM systems with frequency-dependent I/Q imbalances
IEEE Transactions on Communications
Efficient compensation of transmitter and receiver IQ imbalance in OFDM systems
EURASIP Journal on Advances in Signal Processing
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OFDM based systems are very sensitive to Radio frequency (RF) impairments such as in-phase/quadrature-phase (IQ) imbalance and carrier frequency offset (CFO). In this paper, a generally applicable joint transmitter (Tx) and receiver (Rx) RF impairment compensation scheme is proposed. It is composed of a time domain equalizer (TEQ) and two frequency domain equalizers (FEQ). The TEQ utilizes the short training symbols (STS) to estimate and compensate the frequency selective Rx IQ imbalance along with the CFO. The two FEQs then work on the specially induced phase rotated long training symbols (LTS) in order to compensate the remaining Tx or the combined Tx and Rx IQ imbalance along with the channel. A frequency-domain smoothing technique is also utilized in order to further speed up the convergence of the equalizers. The resulting cascade of equalizers provide an efficient compensation scheme in terms of both computational complexity as well as faster convergence.