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

Abstract

RF performance of fifth-generation (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 article, 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 (PoC) 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° beam steering varies from 205 000 to 6500 m2 using 16-QAM and 256-QAM modulations, respectively. Usable beamwidth (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.