Exact SINR analysis of OFDM systems under joint Tx/RX I/Q imbalance

Özdemir, Özgür; Hamila, Ridha; Al-Dhahir, Naofal

doi:10.1109/pimrc.2013.6666216

Cited by 3 publications

(8 citation statements)

References 9 publications

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“…The augmented signal has a slightly more complicated covariance matrix than (20). Fortunately, the covariance matrix of the augmented signal model can be in general expressed as…”

Section: A Covariance Matricesmentioning

confidence: 99%

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Interference Suppression with Antenna Arrays in OFDM Systems under Transceiver I/Q Imbalance

Hakkarainen¹,

Werner²,

Dandekar³

et al. 2014

Proceedings of the 9th International Conference on Cognitive Radio Oriented Wireless Networks

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In this paper, we address the effects of radio frequency (RF) transceiver in-phase/quadrature-phase (I/Q) imbalance in transmission systems which are utilizing orthogonal frequency-division multiplexing (OFDM) waveforms. Special emphasis is on the analysis of external interference sources and their mitigation with receiver antenna array processing, assuming independent fading for the antenna elements. In addition, I/Q imbalance is assumed to be arbitrarily frequency selective and independent in different transceiver branches. We show that I/Q imbalance is especially harmful in the presence of strong interferers when conventional per-subcarrier processing is implemented on the receiver side. Based on these results, we propose a joint subcarrier processing where each of the subcarrier signals is combined with the signal at the image carrier. Such processing is shown to be very efficient in I/Q imbalance mitigation as well as in the total interference suppression.

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“…The augmented signal has a slightly more complicated covariance matrix than (20). Fortunately, the covariance matrix of the augmented signal model can be in general expressed as…”

Section: A Covariance Matricesmentioning

confidence: 99%

“…Now we obtain the covariance matrix of the augmented signal model under joint TX+RX I/Q imbalance simply by substituting (20) and (22) into (21).…”

Section: A Covariance Matricesmentioning

confidence: 99%

Interference Suppression with Antenna Arrays in OFDM Systems under Transceiver I/Q Imbalance

Hakkarainen¹,

Werner²,

Dandekar³

et al. 2014

Proceedings of the 9th International Conference on Cognitive Radio Oriented Wireless Networks

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“…This is already a well-established phenomenon in the existing literature, see e.g. [4], [7], [18], [40]. Notice, however, that if the image subcarrier c is not allocated for UE u there is no cross-talk between the subcarriers of an individual UE and the resulting transmitted signal at subcarrier c consists only of the scaled version of s u,c .…”

Section: B Uplink Mu-mimo Transmission Under I/q Imbalancementioning

confidence: 80%

Analysis and Augmented Spatial Processing for Uplink OFDMA MU-MIMO Receiver With Transceiver I/Q Imbalance and External Interference

Hakkarainen

Werner

Dandekar

et al. 2016

IEEE Trans. Wireless Commun.

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Abstract-This paper addresses receiver (RX) signal processing in multiuser multiple-input multiple-output (MU-MIMO) systems. We focus on uplink orthogonal frequency-division multiple access (OFDMA)-based MU-MIMO communications under inphase/quadrature (I/Q) imbalance in the associated radio frequency electronics. It is shown in the existing literature that transceiver I/Q imbalances cause cross-talk of mirror-subcarriers in OFDM systems. As opposed to typically reported single-user studies, we extend the studies to OFDMA-based MU-MIMO communications, with simultaneous user multiplexing in both frequency and spatial domains, and incorporate also external interference from multiple sources at RX input, for modeling challenging conditions in increasingly popular heterogeneous networks. In the signal processing developments, we exploit the augmented subcarrier processing, which processes each subcarrier jointly with its counterpart at the image subcarrier, and jointly across all RX antennas. Furthermore, we derive an optimal augmented linear RX in terms of minimizing the meansquared error. The novel approach integrates the I/Q imbalance mitigation, external interference suppression and data stream separation of multiple UEs into a single processing stage, thus avoiding separate transceiver calibration. Extensive analysis and numerical results show the signal-to-interference-plus-noise ratio (SINR) and symbol-error rate (SER) behavior of an arbitrary data stream after RX spatial processing as a function of different system and impairment parameters. Based on the results, the performance of the conventional per-subcarrier processing is heavily limited under transceiver I/Q imbalances, and is particularly sensitive to external interferers, whereas the proposed augmented subcarrier processing provides a high-performance signal processing solution being able to detect the signals of different users as well as suppress the external interference This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible.This efficiently. Finally, we also extend the studies to massive MIMO framework, with very large antenna systems. It is shown that, despite the huge number of RX antennas, the conventional linear processing methods still suffer heavily from I/Q imbalances while the augmented approach does not have such limitations.

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“…This is a well-known phenomenon, discussed e.g. in [9], [11], [13]- [15]. In general, when the image subcarrier c ′ is allocated to another UE v, this results in cross-talk between UEs at mirror subcarriers.…”

Section: A Joint Tx+rx I/q Imbalances In Mu-mimo Systemsmentioning

confidence: 98%

“…However, as discussed in Section II.B, the processing capabilities can be enhanced by processing jointly the signal at the image subcarrier. Therefore, we extend the equalizer (15) such that it can process the augmented signal r TxRxi,c directly.…”

Section: B Linear and Augmented Linear Mmse Post-processingmentioning

confidence: 99%

Precoded massive MU-MIMO uplink transmission under transceiver I/Q imbalance

Hakkarainen

Werner

Dandekar

et al. 2014

2014 IEEE Globecom Workshops (GC Wkshps)

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In massive multiple-input multiple-output (MIMO) systems, combined with digital array processing, the amount of the associated radio frequency (RF) front-ends is inevitably high. This paper addresses how imperfections in these RF front-ends affect the overall system performance in precoded massive multiuser MIMO (MU-MIMO) uplink transmission. In particular, we focus on transceiver in-phase/quadrature (I/Q) imbalances and their mitigation with RF-aware spatial processing. We first derive the essential distortion and interference models for OFDMAbased massive MU-MIMO uplink system under I/Q imbalances, and then propose augmented spatial post-processing to be carried out in the uplink receiver (RX) for mitigating the harmful effects efficiently. Numerical examples show that the augmented spatial RX processing clearly outperforms the conventional linear processing, and thus provides significant performance improvements with practical low-cost RF front-ends.Index Terms-antenna arrays, in-phase/quadrature (I/Q) imbalance, interference suppression, massive multi-user multipleinput multiple-output (MU-MIMO), orthogonal frequencydivision multiple access (OFDMA)

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Exact SINR analysis of OFDM systems under joint Tx/RX I/Q imbalance

Cited by 3 publications

References 9 publications

Interference Suppression with Antenna Arrays in OFDM Systems under Transceiver I/Q Imbalance

Interference Suppression with Antenna Arrays in OFDM Systems under Transceiver I/Q Imbalance

Analysis and Augmented Spatial Processing for Uplink OFDMA MU-MIMO Receiver With Transceiver I/Q Imbalance and External Interference

Precoded massive MU-MIMO uplink transmission under transceiver I/Q imbalance

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