Spectral Efficiency Analysis of Downlink Cell-Free Massive MIMO

The rapid advancement of communication technologies is connecting the world faster than ever before. However, this has resulted in a scarcity of frequency spectrum as the available communication bandwidth is limited. To maximize data transmission rates while using a fixed bandwidth, a mechanism is needed to improve spectral efficiency. Distributed massive multiple input multiple output (MIMO) systems involve deploying a large number of transmitting antennas around user equipment (UEs) to achieve this goal. However, in cellular massive MIMO, signal interference around cell edges can present a problem. To address interference issues around cell edges in cellular massive MIMO, cell-free massive MIMO was introduced, which incorporates both massive MIMO and distributed MIMO principles. Cell-free massive MIMO is advantageous as it places users closer to access points (APs), enabling higher spectral efficiency. While cell-free massive MIMO improves spectral efficiency, signal processing techniques such as precoding are needed to maximize it further.