It is well-known that massive multiple-input
multiple-output (MIMO) systems have high potential for future wireless broadband systems. Requirements such as high
spectral and power efficiency are also crucial in 5G. Based
on a multi-amplifier structure it is possible to define a double
layered structure where each amplification branch is connected to an antenna array to achieve both constellation
and power directivies, assuring at same time similar performances to systems using transmitters with 2-dimensional
antenna arrays. Thus, a different path can be followed to
improve energy efficiency of power amplification where the
usage of parallel amplification branches is combined with big
arrays of antennas and multi-stream communication systems.
These systems can be combined with single-carrier with frequency domain equalization (SC-FDE) schemes to improve
the power efficiency in uplink due to the low envelope fluctuations.