A very recent contribution [33] considered PLS in a twotier
heterogeneous network with one Eve wiretapping macrocell
users. We point out that, the authors in [33] focused on the
design/optimization of secrecy beamforming, but not from the
perspective of network analysis and deployment. Their conclusions
are based on the idealized assumption that the CSI of the
Eve is perfectly available. Moreover, they considered neither
the multi-Eve wiretap scenarios, nor the random spatial positions
of network nodes and the large-scale path loss. To the
best of our knowledge, no prior work has accounted for PLS
when designing HCNs, and a fundamental analysis framework
to evaluate the secrecy performance in HCNs is lacking, which
has motivated our work.