OFDM Interference Mitigation Algorithms for Doubly-Selective Channels

Lu, Sili; Kalbasi, Reza; Al-Dhahir, Naofal

doi:10.1109/vtcf.2006.295

Cited by 23 publications

(20 citation statements)

References 9 publications

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“…Substituting and in (6) and grouping the terms carefully, we get (7) where and . Substituting (4) in (6) and using the relations and , we obtain (8) Then, is transmitted through the channel and the received passband signal is (9) which has the baseband equivalent signal (10) where is the channel impulse response (CIR) and is additive white Gaussian noise (AWGN) with two-sided power spectral density of . The received signal is down-converted and input to the receive LPF in each branch.…”

Section: A General I/q Imbalance Modelmentioning

confidence: 99%

“…In the frequency domain, the channel matrix is no longer diagonal resulting in ICI. However, can be well-approximated by a banded matrix as discussed in Section IV-B (see, e.g., [9] and references therein) since most of the ICI energy is due to neighboring sub-carriers. …”

Section: B Mobile Ofdm With Fd Joint Tx/rx I/q Imbalancementioning

confidence: 99%

“…is not diagonal in general and this results in a computationally-complex equalizer as in (34), but, as shown in [9] and references therein, can be well approximated by a banded matrix as most of the ICI energy is from neighboring sub-carriers. The number of significant diagonals of depends on the Doppler spread.…”

Section: B Reduced-complexity Fir Mmse-feqmentioning

confidence: 99%

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Digital Compensation of Frequency-Dependent Joint Tx/Rx I/Q Imbalance in OFDM Systems Under High Mobility

Narasimhan

Wang

Narayanan

et al. 2009

IEEE J. Sel. Top. Signal Process.

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Abstract-Direct conversion orthogonal frequency division multiplexing (OFDM) systems suffer from transmit and receive analog processing impairments such as in-phase/quadrature (I/Q) imbalance causing inter-carrier interference (ICI) among sub-carriers. Another source of performance-limiting ICI in OFDM systems is Doppler spread due to mobility. However, the nature of ICI due to each of them is quite different. Unlike previous work which considered these two impairments separately, we develop a unified mathematical framework to characterize, estimate, and jointly mitigate ICI due to I/Q imbalance and high mobility. Based on our general model, we derive a closed-form expression for the degradation in signal-to-interference-plus-noise ratio (SINR) due to the impairments. Moreover, we exploit the special ICI structure to design efficient OFDM channel estimation and digital baseband compensation schemes for joint transmit/receive frequency-independent (FI) and frequency-dependent (FD) I/Q imbalances under highmobility conditions. Index Terms-Channel estimation, in-phase/quadrature (I/Q) imbalance, inter-carrier interference (ICI), minimum mean square error (MMSE) equalization, mobility, orthogonal frequency division multiplexing (OFDM), signal-to-interference-plus-noise ratio (SINR).

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Section: A General I/q Imbalance Modelmentioning

confidence: 99%

Section: B Mobile Ofdm With Fd Joint Tx/rx I/q Imbalancementioning

confidence: 99%

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Digital Compensation of Frequency-Dependent Joint Tx/Rx I/Q Imbalance in OFDM Systems Under High Mobility

Narasimhan

Wang

Narayanan

et al. 2009

IEEE J. Sel. Top. Signal Process.

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“…But for Doppler spreads of up to 20% of the subcarrier spacing, it is enough to consider only the leakage of a subcarrier to its neighbors [8]. Therefore, in G(k, m) of (8), all blocks G i,j (k, m) with |i − j| > 1 can be set to zero-matrices of appropriate dimensions.…”

Section: Modeling Of I/q Imbalance With Mobilitymentioning

confidence: 99%

Digital Baseband Compensation for Mobile SFBC-OFDM Systems with Receiver I/Q Imbalance

Narasimhan

Wang

Narayanan

et al. 2008

IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference

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Abstract-In-phase and Quadrature-phase (I/Q) imbalance is a major performance-limiting impairment for directconversion Orthogonal Frequency Division Multiplexing (OFDM) transceivers. I/Q imbalance degrades the Signal-to-Noise-Ratio in an OFDM system by causing Inter-Channel-Interference (ICI) between image subcarriers. Doppler spread due to mobility also causes ICI but mainly between adjacent subcarriers. In this work, we investigate the combined effects of mobility and I/Q imbalance in a Multiple-Input-Multiple-Output-OFDM system with the Alamouti Space-Frequency Block-Coding scheme and design an effective compensation technique. Furthermore, we propose a novel pilot allocation and channel estimation scheme, and exploit the problem structure to reduce complexity.

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“…The consequences of these phenomena on the performance of OFDM systems have been widely analyzed (see e.g. [4][5][6][7]). To overcome that problem, it is required that all channel state informations (CSIs) be estimated in each OFDM symbol duration.…”

Section: Introductionmentioning

confidence: 99%

A robust ICI suppression based on an adaptive equalizer for very fast time-varying channels in LTE-R systems

Cho

Nguyen

Nguyễn

et al. 2018

J Wireless Com Network

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High-speed railway communication implemented based on Long-Term Evolution-Railway (LTE-R) Platform has strict requirements for quality of services to support high data-rate transmission for numerous mobile users. In such environment, there often exists inter-carrier interference. In this paper, we exploit a robust channel estimation method in the time domain for very fast time-varying LTE-railway channels, and then, we propose an effective and adaptive frequency-domain equalizer that can offer a tradeoff between performance and computational complexity. The simulation results show the robustness of our proposed method compared with previous ones. The computational complexity of the proposed method retain at a decent number by exploiting specified properties of channel matrices.

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OFDM Interference Mitigation Algorithms for Doubly-Selective Channels

Cited by 23 publications

References 9 publications

Digital Compensation of Frequency-Dependent Joint Tx/Rx I/Q Imbalance in OFDM Systems Under High Mobility

Digital Compensation of Frequency-Dependent Joint Tx/Rx I/Q Imbalance in OFDM Systems Under High Mobility

Digital Baseband Compensation for Mobile SFBC-OFDM Systems with Receiver I/Q Imbalance

A robust ICI suppression based on an adaptive equalizer for very fast time-varying channels in LTE-R systems

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