  Rate-Splitting Multiple Access (RSMA) is a general and powerful multiple
access framework for downlink multi-antenna systems, and contains
Space-Division Multiple Access (SDMA) and Non-Orthogonal Multiple Access (NOMA)
as special cases. RSMA relies on linearly precoded rate-splitting with
Successive Interference Cancellation (SIC) to decode part of the interference
and treat the remaining part of the interference as noise. Recently, RSMA has
been shown to outperform both SDMA and NOMA rate-wise in a wide range of
network loads (underloaded and overloaded regimes) and user deployments (with a
diversity of channel directions, channel strengths and qualities of Channel
State Information at the Transmitter). Moreover, RSMA was shown to provide
spectral efficiency and QoS enhancements over NOMA at a lower computational
complexity for the transmit scheduler and the receivers. In this paper, we
build upon those results and investigate the energy efficiency of RSMA compared
to SDMA and NOMA. Considering a multiple-input single-output broadcast channel,
we show that RSMA is more energy-efficient than SDMA and NOMA in a wide range
of user deployments (with a diversity of channel directions and channel
strengths). We conclude that RSMA is more spectrally and energy-efficient than
SDMA and NOMA.
