5G mmW Link Range Uncertainties from RF System Calculations and OTA measurements
Phased arrays in 5G millimeter wave (mmW) communication are used at both link ends to separate users and to enhance the link range. The radio hardware’s RF performance metrics vary due to part-to-part variations within component tolerances. In this paper, we derive probability density functions (PDFs) of over-the-air (OTA) transmission (TX) powers for individual transmitter (Tx) paths and total TX power of the 5G mmW array using Monte Carlo simulations based on component tolerances. The PDF of the TX power individual path of the array follows a log-normal distribution on a linear scale. Hence, the total array’s OTA TX power is a sum of independent linear scale log-normal powers when the power combination happens in OTA towards the main beam direction. We show that the Tx array’s mean power increases when multiple log-normally variated individual TX powers are summed together. Additionally, we prove that a link budget maps to a link range in a non-linear way, skewing the normally distributed link budget to a log-normally distributed link range. The link ranges based on RF system parameter analysis, RF system calculation, and OTA measured system error vector magnitude (EVM) based link range estimation had an excellent match when a 16-QAM 5G NR signal was used. The calculated link ranges are 410 and 434 meters, while the OTA measured system EVM measurement-based link range is 415 meters. For example, uncalibrated Tx array paths would increase the mean of the array’s TX power by 1.2 dB, and the link range increases from 415 to 498 meters, but simultaneously the standard deviation increases from 26 to 51 meters.