  The frequency diverse array (FDA) based directional modulation (DM)
technology plays an important role in the implementation of the physical-layer
security (PLS) transmission of 5G and beyond communication system. In order to
meet the tremendous increase in mobile data traffic, a new design consuming
less memory for the FDA-DM-based PLS transmission is urgently demanded. In this
paper, an analytical symmetrical multi-carrier FDA model is proposed in three
dimensions, namely, range, azimuth angle, and elevation angle, which differs
from the conventional analytical approach with only range and azimuth angle
considered. Then, a single-point (SP) artificial noise (AN) aided FDA-DM scheme
is proposed, which reduces memory consumption of FDA-DM systems significantly
compared with the conventional zero-forcing (ZF) and singular value
decomposition (SVD) approaches. Moreover, the PLS performance of the proposed
low-memory-consumption FDA-DM scheme is analyzed in fluctuating two-ray (FTR)
fading channels for the first time, including bit error rate (BER), secrecy
rate (SR), and secrecy outage probability (SOP). More importantly, the
closed-form expressions for the lower bound of the average SR and the upper
bound of the SOP are derived, respectively. The effectiveness of the analytical
expressions is verified by numerical simulations. This work opens a way to
lower the memory requirements for the DM-based PLS transmission of 5G and
beyond communication system.
