Such antenna arrays can create multiple signal beams. Massive MIMO can be applied in a scattering rich environment, i.e. in conditions where signals are scattered of buildings and other objects such that each user can be reached via multiple paths. At the location of the intended user signals from all these paths add constructively, enabling a high data rate. Away from the intended user the signals are not correlated and merely add to the background noise.
For operators to continue improving their services in this way, as we have come to expect, there will be a cost, particularly in the increased complexity and related power consumption of basestations and terminal equipment.
What’s the issue? Multichannel phase shifting can be done in the analog domain, by taking the transmit data stream, dividing it as many ways as there are elements in the antenna array, and then applying phase shifting to each of them (see Figure 1).