EE-SE relationship in MIMO systems

Energy efficiency (EE) has been recognized as another important metric as well as spectral efficiency (SE). This paper investigates the fundamental properties of the EE-SE relationship for point-to-point MIMO transmission link. Reducing circuit power is helpful to improve EE in the low SE region while introducing more antennas benefits the EE in the high SE region. We also study the properties of EE-optimal points. It is found that reducing circuit power brings exponential EE increasing with linear SE loss at the EE-optimal points. More multiplexing gain will alleviate the speed of EE reduction with the increase of SE. More diversity gain brings a fixed EE gain. Above conclusion is also suitable to MIMO systems with active antennas. With the given number of antennas, there is an optimal number of transceivers to maximize the EE for each SE value.