  Exchange of crucial and confidential information leads to the unprecedented
attention on the security problem in wireless networks. Though the security has
been studied in a number of works, the joint optimization of the physical layer
security and the end-to-end delay management, which requires a meticulous
cross-layer design, has seldom been evaluated. In this work, by combining the
tools from stochastic geometry and queueing theory, we analyze the tradeoff
between the delay and the security performance in large wireless networks. We
further propose a simple transmission mechanism which splits a message into two
packets and evaluate its effect on the mean delay and the secrecy outage
probability. Our numerical results reveal that the security performance is
better for larger path loss exponent when the density of legitimate nodes is
large, and it is reverse when the density is small. Moreover, it is observed
that by introducing the simple mechanism of message split, the security
performance is greatly improved in the backlogged scenario and slightly
improved in the dynamic scenario when the density of legitimate transmitters is
large. In summary, this work provides an understanding and a rule-of-thumb for
the practical design of wireless networks where both the delay and the security
are key concerns.
