Over the air-measurement investigations for 5G and beyond

Over the air (OTA) performance is one of the most critical parameters in any wireless communication system. Especially, this aspect has raised the importance of the 5G system when all radio parameters of the 5G millimeter wave (mmW) system are measured OTA manner. Thus, this is a fundamental change in the wireless system standardization since all previous wireless communication generations have been evaluated and measured with conductive testing methods using coaxial cables and appropriate connectors. The 5G mmW radios are using phased arrays with a high number of antenna elements to improve the OTA performance. The phased arrays in the mobile and base stations are highly integrated. Conductive testing is no longer possible due to cabling complexity and limited access between radio front-end components and antenna elements. Thus, OTA measurements can only verify the 5G mmW radios from a functionality, performance, calibration, and system integration point of view. The same OTA measurement-based performance testing trend will continue beyond 5G or 6G systems, as well.

Thus, the 5G systems have challenged current OTA measurement systems and methods, and improvement of these has been studied in the 5GViima project. We have performed 5G mmW radio calibrations from 24 to 28 GHz OTA manner and improved the performance of the phased array with a new calibration method. Additionally, we have applied digital predistortion to the 5G mmW antenna array radio, and the OTA system has been used for calibration feedback mechanism and performance measurements. Based on the OTA performance measurement results, we estimated 5G mmW radio link range and coverage without time-consuming and error-prone test drives. Excellent correspondence between OTA laboratory and outdoors measurements and system-level link range calculations has been reported in our publications. The mobile or base stations’ OTA performance depends on radio and antenna performances, and we have studied 5G mmW antenna arrays in the project. The primary motivation for the studies has been how we can extend the antenna frequency coverage to cover both 5G mmW bands from 24 to 28 GHz and 37 to 40 GHz with one antenna implementation. Other studied aspects of 5G mmW antennas have been integrating filtering to out-of-band frequencies into the antenna implementation without antenna performance degradation.

Beyond 5G studies, we have investigated with OTA measurements 5G mmW and potential 6G radio interoperability challenges. First steps towards the 6G OTA systems have been taken during the project by evaluating measurement system components and first OTA link blockage measurements performed at 300 GHz. More details of mentioned research topics can be found in the following publications.

Contact:

Marko Leinonen, [email protected]

(a)

(b)

Fig 1. 5G mmW OTA testing at (a) EMC-laboratory and (b) outdoors.

Fig 2. Signal blocking measurements at 300 GHz with a phantom hand.

1. N. Tervo, B. Khan, O. Kursu, J. P. Aikio, M. Jokinen, M. E. Leinonen, M. Juntti, T. Rahkonen, A. Pärssinen “Digital Predistortion of Phased Array Transmitter With Shared Feedback and Far-Field Calibration,” in Transactions on Microwave Theory and Techniques, Vol. 69, no. 1, pp. 1000-1015, Jan. 2021.
2. M. E. Leinonen, N. Tervo, M. Jokinen, O. Kursu and A. Pärssinen (2021) 5G mmW Link Range Uncertainties from RF System Calculations and OTA measurements, IEEE Access,
3. Z. Siddiqui, M. Sonkki, M. E. Leinonen, J. Chen, M. Berg and A. Pärssinen, “A Differential Dual-band Dual-polarized Antenna for 5G mmWave Communication System,” 2020 2nd 6G Wireless Summit (6G SUMMIT), Levi, Finland, 2020, pp. 1-4.
4. N. Tervo, B. Khan, O. Kursu, J. Aikio, M. Jokinen, M. E. Leinonen, M. Juntti, T. Rahkonen and A. Pärssinen (2020) Digital Predistortion of Millimeter-Wave Phased Array Transmitter with Over-the-air Calibrated Simplified Conductive Feedback Architecture, IMS2020, pp. 543-546,
5. M. E. Leinonen, M. Jokinen, N. Tervo, O. Kursu and A. Pärssinen (2020) Radio Interoperability in 5G and 6G Multiradio Base Station, VTC2020 Fall, pp. 1-5.
6. M. Leinonen, K. Nevala, N. Tervo, A. Pärssinen, ”Linearity Measurement of 6G Receiver with One Transmission Frequency Extender Operating at 330 GHz,” 96th ARFTG Microwave Measurement Conference, 17-20 January 2021, San Diego, USA, pp. 1-4.
7. Z. Siddiqui, M. Sonkki, K. Rasilainen, J. Cheng, M. Berg, M. Leinonen, A. Pärssinen, ” Dual-Polarized Filtering Antenna for Mm-Wave 5G Base Station Antenna Array,” 15th European Conference on Antennas and Propagation (EuCAP), 22-26 March 2021, Düsseldorf, Germany.
8. P. Kyösti, N. Tervo, M. Berg, M. Leinonen, K. Nevala, A. Pärssinen, ” Measured Blockage Effect of a Finger and Similar Small Objects at 300 GHz,” accepted to 15th European Conference on Antennas and Propagation (EuCAP), 22-26 March 2021, Düsseldorf, Germany.