Routing Over Multi-Hop Fading Wiretap Networks With Secrecy Outage Probability Constraint

We consider a wireless network where two nodes (source and destination) aim at exchanging a message that must be kept secret from a third eavesdropper node. Other legitimate nodes relay the message from the source to the destination over multiple hops. Channels are subject to fading and only a partial channel state information at the transmitter is available before transmission. Assuming that each transmission has an entangled cost, e.g., delay or energy, we aim at finding the optimal routing policy that minimizes the cost with a constraint on the average secrecy outage probability. We model the problem as the search for a control policy of a stochastic dynamic system that minimizes a discounted expected cost objective, with a discounted expectation constraint. A Lagrange-multiplier based solution is proposed. Numerical results show the merits of the proposed solution over a multi-hop wireless network.