6 research outputs found
Constrained Secrecy Capacity of Finite-Input Intersymbol Interference Wiretap Channels
We consider reliable and secure communication over intersymbol interference
wiretap channels (ISI-WTCs). In particular, we first examine the setup where
the source at the input of an ISI-WTC is unconstrained and then, based on a
general achievability result for arbitrary wiretap channels, we derive an
achievable secure rate for this ISI-WTC. Afterwards, we examine the setup where
the source at the input of an ISI-WTC is constrained to be a finite-state
machine source (FSMS) of a certain order and structure. Optimizing the
parameters of this FSMS toward maximizing the secure rate is a computationally
intractable problem in general, and so, toward finding a local maximum, we
propose an iterative algorithm that at every iteration replaces the secure rate
function by a suitable surrogate function whose maximum can be found
efficiently. Although the secure rates achieved in the unconstrained setup are
potentially larger than the secure rates achieved in the constraint setup, the
latter setup has the advantage of leading to efficient algorithms for
estimating achievable secure rates and also has the benefit of being the basis
of efficient encoding and decoding schemes.Comment: 32 pages, 6 figure