  Recently, it has been shown that the time-varying multiple-access channel
(MAC) with perfect channel state information (CSI) at the receiver and delayed
feedback CSI at the transmitters can be modeled as the finite state MAC
(FS-MAC) with delayed state feedback, where the time variation of the channel
is characterized by the statistics of the underlying state process. To study
the fundamental limit of the secure transmission over multi-user wireless
communication systems, we re-visit the FS-MAC with delayed state feedback by
considering an external eavesdropper, which we call the finite state
multiple-access wiretap channel (FS-MAC-WT) with delayed feedback. The main
contribution of this paper is to show that taking full advantage of the delayed
channel output feedback helps to increase the secrecy rate region of the
FS-MAC-WT with delayed state feedback, and the results of this paper are
further illustrated by a degraded Gaussian fading example.
