At Mobile World Congress (MWC) in Barcelona last week, there were a number of companies offering improvements to massive MIMO (multiple input multiple output) technology. Massive MIMO systems use a large number of antennas—say, 64—to transmit and receive radio frequency (RF) signals in parallel.
This huge increase in the number of antennas provides a big boost to the number of data streams that such systems can handle compared to today’s base stations. As a result, massive MIMO is now considered a foundational technology for future 5G networks, which explains its strong representation at MWC.
On a massive MIMO base station, those 64 antennas are placed in a planar arrangement (such as 8 x 8 or 4 x 12) termed the “antenna array.” As a result, at any moment, there are 64 transmit signals leaving the antenna array and 64 signals coming into the antenna array.
These massive MIMO systems come with some complications. For example: When you’re transmitting 64 signals at once, how do you ensure the signals are aligned in time and phase with respect to each other?