Non-Linearities Study and EVM Characterization of a Sub-6 Frequency Testbed for 5G Communication

The first deployment of 5G will be on the 4G frequency bands (frequency bands below 3 GHz) and the new Sub-6 frequency bands above 3 GHz. The use of a large bandwidth and new high frequencies requires a preliminary study of the signal quality in this band. The Testbed is an ideal tool to simulate the transmission on real networks and to analyze its performance. In this paper, we setup a Sub-6 Testbed, present its architecture, study the origins of the signal degradation such as phase noise and signal power variations, and evaluate its performance by measuring the Error Vector Magnitude (EVM). The measurements are performed on a cable transmission as well as on an Over-The-Air (OTA) transmission. The results obtained show that the system has a phase noise of -84 dBc/Hz and a power reduction of 1 dBm/ GHz when the frequency increases. Besides, with 64QAM modulation, a minimum EVM of -41 dB is obtained for cable transmission and -35 dB for OTA transmission at a distance equal to 0.5 meter respectively. Moreover, the system EVM limited by the 3GPP group is achieved at a distance equal to 4, 4.3 and 5.9 meters for a 64QAM, 16QAM and QPSK OFDM signal respectively.