  Full-duplex (FD) jamming transceivers are recently shown to enhance the
information security of wireless communication systems by simultaneously
transmitting artificial noise (AN) while receiving information. In this work,
we investigate if FD jamming can also improve the systems secrecy energy
efficiency (SEE) in terms of securely communicated bits-per- Joule, when
considering the additional power used for jamming and self-interference (SI)
cancellation. Moreover, the degrading effect of the residual SI is also taken
into account. In this regard, we formulate a set of SEE maximization problems
for a FD multiple-input-multiple-output multiple-antenna eavesdropper (MIMOME)
wiretap channel, considering both cases where exact or statistical channel
state information (CSI) is available. Due to the intractable problem structure,
we propose iterative solutions in each case with a proven convergence to a
stationary point. Numerical simulations indicate only a marginal SEE gain,
through the utilization of FD jamming, for a wide range of system conditions.
However, when SI can efficiently be mitigated, the observed gain is
considerable for scenarios with a small distance between the FD node and the
eavesdropper, a high Signal-to-noise ratio (SNR), or for a bidirectional FD
communication setup.
