Will COTS RF Front-Ends Really Cope With 5G Requirements at mmWave?

In this paper, the real-time over-the-air multi-gigabit wideband wireless orthogonal frequency division multiplexing (OFDM) system performance, using two distinct radio frequency (RF) front-ends designed for the millimetre frequency band (mmWave), is evaluated. A thorough comparative analysis between 60-GHz cutting-edge commercial off-the-shelf and reference RF front-ends, taking into account their intrinsic RF impairments and their impact on the overall system performance degradation, is presented. With this, it is possible to verify whether system on chip technology for RF circuits is ready for 5G systems. Due to the large available bandwidth, the mmWave band is very attractive for future 5G wireless communication systems, which might provide transmission data rates over 10 Gb/s and network latency below 1 ms. However, non-linearities of RF front-ends, at these frequencies, severely affect the performance of transmission schemes. In fact, this is the main cause for performance degradation on OFDM systems. It causes significant limitation on both maximum spectral efficiency and data rate of the wireless communication link. Therefore, the OFDM performance degradation due to the non-linearities from both analogue stages of upconversion/downconversion is evaluated considering important key performance indicators for quality of service in digital communications considering 4-, 16-, 64- and 256-quadrature amplitude modulation. Furthermore, based on the results obtained from appropriate RF measurements, a practical EVM link budget formulation for mmWave systems, which takes into account both PA and PN impairment effects, is proposed.