Massive MIMO is a promising technology for 5G. While its advantages of increasing capacity and reducing output power are clear, understanding its SNR requirements in practical cases lacks sufficient theoretical support. This paper computes the relative power levels of the different signal, interference and noise terms in a Massive MIMO system using Maximum-Ratio Transmission (MRT). This brings light on the operational region of the system. The MRT operation is shown to support a maximum number of users, which is function of the selected modulation and coding scheme. The related expression also leads to a bound for other linear precoders. The impact of channel estimation is shown to be related to the number of orthogonal pilot sequences and users. When both are equal it leads to a 3 dB degradation. At system level, this model directly impacts output power requirements and hence system trade-offs when determining the number of antennas to use.
['Claude Desset']
Signal, noise and interference power analysis in MRT-based Massive MIMO systems