Academic
Publications
Frequency offset and I/Q imbalance compensation for OFDM direct-conversion receivers

Frequency offset and I/Q imbalance compensation for OFDM direct-conversion receivers,10.1109/ICASSP.2003.1202741,Guanbin Xing,Manyuan Shen,Hui Liu

Frequency offset and I/Q imbalance compensation for OFDM direct-conversion receivers   (Citations: 20)
BibTex | RIS | RefWorks Download
Two types of RF front-end imperfections in direct-conversion receivers, namely frequency offset and I/Q imbalance, are addressed. The I/Q imbalance not only introduces an unwanted image interference, but also degrades the accuracy of carrier estimation. We propose a pilot-based scheme for both frequency offset and I/Q imbalance compensation. A nonlinear least squares (NLS) frequency estimator, robust to the I/Q imbalance, is developed. Also derived is an I/Q compensation structure that consists of two stages: the frequency dependent imbalance is compensated with an FIR filter whereas the frequency independent part is corrected with an asymmetric phase compensator. The compensation coefficients are optimized by restoring the phase rotation embedded in the pilot symbols.
Cumulative Annual
View Publication
The following links allow you to view full publications. These links are maintained by other sources not affiliated with Microsoft Academic Search.
    • ...In [7], an algorithm for I1Q imbalance compensation in the presence CFO was proposed...
    • ...CFO and I/Q imbalance in field programmable gate array (FPGA), and then we used the algorithm in [7] as Implemented system uses the 7r/4 differential quadrature phase shift keying (7r/4DQPSK) wireless communication system...

    Takuro Yoshidaet al. FPGA implementation of joint CFO and IQ-imbalance compensator for narr...

    • ...Several articles on static and dynamic description of the imbalance effects for the modulator [2], [3] and the demodulator [4], [5], [6] can be found...
    • ...Using the same naming convention as in the foregoing section the frequency domain representation of the linear IQ-demodulator output signal is given by [4], [6]:...

    Michael E. Gadringeret al. Comparison of the imbalance effects in direct conversion transmitters ...

    • ...Fortunately, a number of methods have already been shown to reduce I/Q imbalance with varying effectivity and complexity [3-8]...
    • ...In [7], an algorithm for I/Q imbalance compensation in the presence of CFO was proposed...
    • ...In [8], an improvement was proposed based on [7] which removes the spectral search based CFO estimation...
    • ...Simulation results show that our proposed algorithm has better CFO accuracy compared to [7] and [8] and can completely remove I/Q imbalance based on its BER performance...
    • ...Details on this system model can be found in [6-8] and references therein...
    • ...This architecture is mainly to aid in the algorithm derivation and can be shown to be equivalent to the architectures in either [7] or [8]...
    • ...This compensation structure reduces the parameters estimated by letting the frequency independent I/Q imbalance parameters be absorbed by the compensating filter w .T he consequence is that compared to the compensating filter in [7], our compensating filter is complex valued...
    • ...Our proposed algorithm similar to [7] and [8] assumes that a P-length training sequence consisting of M N-length short symbols is transmitted and used to estimate CFO and I/Q imbalance...
    • ...The derivations for CFO and I/Q imbalance assumes that a minimum amount of CFO is present for stability just like [7] and [8]...
    • ...Since the bulk of the computations for all algorithms is in the compensating filter pseudo-inverse step except possibly for [7], the proposed algorithm saves a lot of complexity by having smaller matrix for this step...
    • ...Note that while the proposed algorithm operate on complex valued matrices, the added complexity is still much lower compared to [7] or [8] where the LLS matrix rank is one and two higher respectively...
    • ...It was however modified to follow (25) when used for the proposed algorithm and [8] while for [7], the preamble was modified to follow its own proposed structure...
    • ...For [7], which estimates the CFO via a line search, we limited the search to [-.48 .48] with a resolution of 0.001...
    • ...Case A � Proposed Case B � Proposed Case A � [7] Case B � [7] Case A � [8] Case B � [8]...
    • ...Case A � Proposed Case B � Proposed Case A � [7] Case B � [7] Case A � [8] Case B � [8]...
    • ...Case A � Proposed Case B � Proposed Case A � [7] Case B � [7] Case A � [8] Case B � [8] NO CFO/IQ...
    • ...Case A � Proposed Case B � Proposed Case A � [7] Case B � [7] Case A � [8] Case B � [8] NO CFO/IQ...
    • ...This is due to the different compensation structures in [7],[8], and the proposed algorithm...
    • ...It is clear from the figure that the proposed algorithm along with [8] can effectively eliminate case A and case B I/Q imbalance whereas as mentioned in [8], [7] has a high BER floor in case B due to inexact signal convolutional structure with the frequency selective I/Q imbalance...

    Leonardo Lanante Jret al. Low complexity compensation of frequency dependent I/Q imbalance and c...

    • ...1) Data-aided (DA) methods, in which special pilots and training symbols are inserted into the transmitted data [3, 4]. 2) Nondata-aided (NDA) methods, in which the transmitted data are used without any other additional information [5, 6]. 3) Adaptive FIR filter based methods, in which the received databeforetheFFTareutilizedtohandleestimation,were presented to certify for an Image RejectionRatio (IRR) of 75–97 dB after compensation...
    • ...The I/Q imbalance with filter mismatch, namely frequency-dependent I/Q imbalance, is much critical for OFDM direct-conversion receivers to make the corresponding estimation and compensation be extremely difficult [3, 9]...
    • ...Simulations of a 2×2 MIMO-OFDM system indicate that the proposed approach results in a 1.2-dB SNR loss with ideal channel estimations to achieve 50-dB IRR and 8% PER at frequency-dependent I/ Q imbalance with a gain error of 1 dB, a phase error of 10° and the worst FDI of 180° [3]...
    • ...Figure 4 displays the model of frequency-dependent I/Q imbalances [3]...
    • ...The basic model [11, 12] is a special case of HI ðf Þ¼ HQðf Þ ,w hereaðf Þ¼ 1 þ ge � jq ðÞ = 2a ndbðf Þ¼ 1 � ge jq ðÞ =2. Figure 5 plots the channel frequency response (CFR) influenced by frequency-dependent I/Q imbalance with 1-dB gain error, 10°-phase error & 20°-phase error, and 180°-filter mismatch [3], in which FDI induces high-frequency ...
    • ...c) The worst FDI: 180°-filter mismatch [3]...
    • ...Ref [3] Ref [4] Ref [5] Ref [6] Ref [7] Ref [8] Proposed work...

    Wei-Chi Laiet al. Cross-Validation Estimation for Frequency-Dependent I/Q Imbalance in M...

    • ...OFDM systems have been an active area of research [5]-[9]...
    • ...The authors claimed that this algorithm aside from providing better accuracy, it is also computationally simpler compared to the earlier proposed algorithm in [9]...

    Leonardo Lanante Jret al. A Simple Estimation Scheme for Joint Estimation of Carrier Frequency O...

Sort by: