  This paper studies the performance of a downlink non-orthogonal multiple
access (NOMA) based cooperative network with maximal ratio transmission/receive
antenna selection (MRT/RAS) over Nakagami-m fading channels in the presence of
channel estimation errors (CEEs). In the system, a base station communicates
with multiple mobile users through a half duplex channel state information
based amplify-and-forward relay. All nodes are equipped with multiple antennas
and the hybrid diversity technique MRT/RAS is employed in both hops. The outage
behavior of the system is investigated by driving closed-form expression for
outage probability (OP). In addition, the corresponding lower and upper bounds
of the derived OP are obtained. Moreover, the behavior of the system is studied
in high signal-to-noise ratio region by obtaining an error floor value in the
presence of CEE as well as achieving diversity and array gains in the absence
of CEE. Finally, the analytical results in the presence and absence of the CEEs
are verified by the Monte Carlo simulations. Results show that the MRT/RAS
scheme enhances the OP significantly and is much more robust to the CEEs in
comparison with the single antenna case.
