A Feasibility Study of Digital Beamforming for 5G mmWave Massive MIMO Base Station Receivers

The future 5G network is promising a performance increase by a factor of 100 to 1000 compared to the previous generation. The foreseen technical solutions to provide this gain are multiple. One of them is to use the large available or under-utilized spectrum in the millimeter wave domain combined with large antenna array beamforming systems in a dense deployment of small cells, the so called massive MIMO. Many previous works have performed system analysis evaluating the performances of the three different architectures, analog, hybrid and digital beamforming, and the impact of design parameters. In this work, in order to evaluate the feasibility of DBF, we propose a simplified methodology to derive, from the 5G key performance indicators, a circuit level specification for such systems. In particular the proposed method takes into consideration, in the presence of strong out of band interferers (OoBI), the impact of the Rx nonlinearity and the local oscillator noise floor. The OoBIs power level is evaluated based on a multiple operator scenario. The resulting specifications were compared to the state of the art to perform a power consumption evaluation and demonstrate the feasibility of digital architectures.