  Instead of merely improving the spectral efficiency (SE), improving the
energy efficiency (EE) is another important concern for multibeam satellite
systems, due to the power constraint of satellites. However, so far there has
been no detailed work on the precoding design concerning the EE for multibeam
satellite. In this work, the EE maximization problem is investigated for
multibeam satellite systems under the total power constraint as well as the
quality of service (QoS) constraints. Precoding design algorithms based on zero
forcing (ZF) and sequential convex approximation (SCA) are presented
respectively. In particular, these algorithms are verified by the real measured
channel data of multibeam satellite systems. Numerical results show that the
precoding algorithm based on SCA outperforms that based on ZF. It is also
implied that the EE cannot be always improved by solely increasing the power of
the satellite, while reducing the satellite operation power is an effective way
for the EE improvement.
