On the Outage Probability of MIMO Full-Duplex Relaying : Impact of Antenna Correlation and Imperfect CSI

This paper analyzes the performance of multipleinput
multiple-output (MIMO) full-duplex (FD) relaying systems,
where the source and destination nodes are equipped with
single antenna and communicating via a dual-hop amplify-andforward
(AF) relay with multiple receive and transmit antennas.
The system performance due to practical wireless transmission
impairments of spatial fading correlation and imperfect channel
state information (CSI) is investigated. At the relay, the loopback
self-interference (LI) is mitigated by using receive zero-forcing
(ZF) precoding scheme, then steering the signal to the destination
by using maximum-ratio transmission (MRT) technique. To this
end, new exact closed-form expressions for the outage probability
are derived, where the case of arbitrary, exponential, and no
correlations are considered. Meanwhile, for a better system
performance insights, simpler outage probability lower-bound
expressions are also included, through which the acheiveable
diversity order of the receive ZF/MRT scheme is shown to be
min (NR 􀀀 1; NT ), where NR and NT are the number of relay
receive and transmit antennas, respectively. Numerical results
sustained by Monte Carlo simulations show the exactness and
tightness of the proposed closed-form exact and lower-bound
expressions, respectively. In addition, it is seen that the outage
probability performance of FD relaying outperforms that of the
conventional half-duplex (HD) relaying at low to medium signalto-
noise ratio (SNR). However, at high SNR, the performance of
HD relaying outperforms that of the FD relaying. Furthermore, in
the presence of channel estimation errors, an outage probability
error floor is seen at high SNR. Therefore, for optimum outage
performance, hybrid relaying modes is proposed which switches
between HD and FD relaying modes.