EE-SE relationship for large-scale antenna systems

In large-scale antenna systems (LSAS), both energy efficiency (EE) and spectral efficiency (SE) have been recognized as important metrics for future communication system design. This paper investigates the fundamental properties of the EE-SE relationship in LSAS. Both single-user and multi-user cases are studied and different channel state information (CSI) conditions are considered. Analysis and simulation results demonstrate that the slope of the EE-SE curve only depends on the circuit power and bandwidth when the SE approaches zero, and it depends on the number of data streams, when the SE approaches infinity. Reducing circuit power brings exponential EE increase with linear SE loss. The CSI and increasing the number of transmit antennas help to reduce the SE loss to keep the same EE in the single-user case. In the multi-user case, increasing the number of users will alleviate the speed of EE reduction with the increase of SE.