Digital Predistortion in Large-Array Digital Beamforming Transmitters

Brihuega, Alberto; Anttila, Lauri; Abdelaziz, Mahmoud; Valkama, Mikko

doi:10.1109/acssc.2018.8645137

Cited by 21 publications

(19 citation statements)

References 15 publications

(26 reference statements)

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“…These confirm the analytical results of Section II. In general, understanding the spatial behaviour of OOB distortions is key when developing efficient digital predistortion (DPD) solutions for multiple antenna transmitters [5], [6].…”

Section: Numerical Examples and Resultsmentioning

confidence: 99%

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On Antenna Array Out-of-Band Emissions

Anttila

Brihuega

Valkama

2019

IEEE Wireless Commun. Lett.

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We substantiate and extend recent research on the behavior of the out-of-band emissions in antenna array transmitters. Specifically, with multi-user precoding, we show that the emissions are always beamformed in the directions of the intended receivers, contrary to some claims in the recent literature. Moreover, while also other spurious directions exist, we show that the emissions are always strongest in the directions of the intended receivers. We also show that power amplifiers with mutually different nonlinear phase characteristics will reduce the beamforming gain of the unwanted emissions, with the gain approaching the noncoherent combining limit as the phase deviations are increased.

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Section: Numerical Examples and Resultsmentioning

confidence: 99%

“…Referring to the definitions in Fig. 1, it is easy to see that (5) and (6) add up coherently in the respective directions defined bỹ…”

Section: A Basic Two-tone Modelmentioning

confidence: 99%

On Antenna Array Out-of-Band Emissions

Anttila

Brihuega

Valkama

2019

IEEE Wireless Commun. Lett.

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“…However, the associated computational is still unsatisfying and limits its practical application in massive MU-MIMO. In [8], authors proposed a DPD based solution that requires only one DPD component per user to linearize an arbitrary number of PAs enabling then the reduction of the complexity associated to the linearization of the different used PAs.…”

Section: Introductionmentioning

confidence: 99%

Efficient Precoding for Massive MIMO Downlink Under PA Nonlinearities

2019

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This letter investigates the compensation of the power amplifier (PA) nonlinear distortion (NLD) in large-scale multi-user (MU) multiple-input multiple-output (MIMO) downlink systems. We introduce a PA-aware precoding approach that exploits the high-dimensional degrees of freedom (DoFs), allowed by equipping the base station (BS) by a high number of antennas, and performs the precoded signals that, when amplified and passed through the channel, guarantee excellent transmission quality. Specifically, we formulate the proposed PA-aware precoding approach as a simple convex optimization problem which enables efficient, low-complexity and reliable algorithm implementations. The simulation results demonstrate the strong potential of the proposed approach in terms of improving the link quality and reducing the required computational complexity.

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“…The feedback structure enables the continuous update of the DPD coefficients for any change in the amplitude and phase weights causing a change in the input power per PA. However, this requires a rapid update of the DPD coefficients with in the coherence time of the channel [9]. This would cost high power consumption in the baseband signal processing for broadband signals and high speed ADC cost in the feedback path.…”

Section: Introductionmentioning

confidence: 99%

Average Linearization of Phased Array Transmitters Under Random Amplitude and Phase Variations

Khan

Tervo

Pärssinen

et al. 2019

2019 16th International Symposium on Wireless Communication Systems (ISWCS)

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We study the impact of amplitude and phase differences between the parallel power amplifier (PA) branches in a phased array and their impact on the performance of the digital predistortion (DPD). The DPD coefficients are estimated from the array response in the far-field. The DPD coefficients need to be updated for changes in the nonlinear behavior of the PAs due to amplitude and phase variations. We present a training mechanism which makes the DPD robust to branch specific amplitude and phase weights and can tolerate these variations without the need of adapting to individual changes in the nonlinear behavior of the PA branches. The DPD is trained for a set of random amplitude and phase weights following normal distribution and the resultant mean DPD coefficients are used for predistortion. The simulation results show that the mean DPD can achieve the same average linearity performance as the continuously trained reference DPD for 32 elements uniform array.

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Digital Predistortion in Large-Array Digital Beamforming Transmitters

Cited by 21 publications

References 15 publications

On Antenna Array Out-of-Band Emissions

On Antenna Array Out-of-Band Emissions

Efficient Precoding for Massive MIMO Downlink Under PA Nonlinearities

Average Linearization of Phased Array Transmitters Under Random Amplitude and Phase Variations

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