Out-of-Band Interference in 5G mmW Multi-Antenna Transceivers: Co-Existence Scenarios

Jokinen

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

et al. 2019

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Linearization of millimeter-wave (mmW) phased arrays is one of the key enablers for improving the system performance in terms of power, efficiency and linearity. However, phased array transceiver topologies that have multiple parallel nonlinear components with a shared digital input challenge the standard digital predistortion techniques. In addition, different analogue beamforming techniques complicate the linearization even further due to the fact that the signal nonlinearity has to be observed or modelled over-the-air (OTA) together with the impacts of antennas and even the directive mmW radio channel. The best linearization strategy depends on the system level targets of linearity such as error vector magnitude and adjacent channel power ratio which have slightly different nature when observed in the radiated far-field. In this paper, we present our view and the status of the literature on the topic of phased array digital predistortion. We highlight that the nonlinear distortion have a beam shape which may be different from the linear part of the beam. We also review the antenna array figures of merit describing the nonlinearity. Finally, we show an experimental example of OTA linearization of a 28 GHz phased array transmitter.

Section: Phased Array Figures Of Merit Of Linearity a Beamformedmentioning

confidence: 99%

Digital Predistortion Concepts for Linearization of mmW Phased Array Transmitters

Jokinen

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

et al. 2019

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“…The linearity of the previous version of the receiver array with eight RX chains has been OTA measured by using 16-QAM modulated 100 MHz signal in [16]. The RX spectrum regrowth due to RX non-linearity was measured by using adjacent channel power (ACP).…”

Section: Implemented 5g Mmw Radio Supporting 28 Ghzmentioning

confidence: 99%

“…16-QAM system EVM measurement (a) single beam result with 5 degrees steering and (b) combined system EVM result over ±15 degrees.…”

mentioning

confidence: 99%

System EVM Characterization and Coverage Area Estimation of 5G Directive mmW Links

Jokinen

IEEE Trans. Microwave Theory Techn.

et al. 2019

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RF performance of 5G new radio (NR) millimeter wave (mmW) system will be characterized over-the-air (OTA) in 3GPP 5G NR performance and type approval testing. Total system Error Vector Magnitude (EVM) performance has not been standardized in 3GPP since mobile and base stations are certified separately. In this paper, we extend the OTA measured system EVM concept to cover EVM performance testing with beam steering for 5G mmW radio link. We show that the OTA measured system EVM inside of an electromagnetic compatibility (EMC) chamber can be directly converted to an expected link range, and this has been verified with outdoor measurements. The EVM measurements are performed for a set of beamforming directions to form an expected coverage area. The OTA measured system EVM results confirm that the 5G mmW Proof-of-Concept radio supports 5G NR 16-QAM and 64-QAM modulations as well as 256-QAM modulation, which is currently specified for sub-6 GHz, only. The maximum estimated range of the 5G PoC mmW link is 840 m with 16-QAM modulation and 150 m with 256-QAM modulation. The estimated cell coverage with ±15 degrees beam steering varies from 205 000 m2 to 6 500 m2 using 16-QAM and 256-QAM modulations, respectively. Usable beam width (BW) of the transceiver array is dependent on the system EVM requirement. It varies based on modulation, coding, and link distance. This phenomenon is called cell breathing, which is similar to any cellular system with adaptive coding techniques, although BW might be much narrower in 5G mmW systems.

“…This has been further discussed in [3] where the authors show that these differences can be actually utilized to compensate each other in the array far field. Hence, the standard figures of merit describing the nonlinear distortion of an array should be revised to have a right meaning from the system perspective [10].…”

Section: A Pa Array Figures Of Meritmentioning

confidence: 99%

Analyzing the Effects of PA Variations on the Performance of Phased Array Digital Predistortion

2018 IEEE 29th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

Aikio

et al. 2018

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This paper shows how digital predistortion of a phased array can benefit from the parametric variations over parallel power amplifiers (PAs). Different antenna configurations are simulated by varying the PA input drive levels by the Monte-Carlo method. The error vector magnitude (EVM) at the steering angle and total radiated adjacent channel power ratio (TRACPR) are used as performance metrics. The simulation results indicate that array predistortion can benefit from the variations between the PAs to improve the EVM significantly. However, at the same time, the TRACPR performance is reduced. This gives a new trade-off to balance between in-band and outoff-band distortion in the fifth generation beamforming systems.