Analyzing Secrecy of Delay-Constrained System in Cooperative Relay Environment Using Rateless Codes

We analyze secrecy of a dual-hop cooperative system consisting of multiple decode-and-forward relays in delay-constrained environment using rateless code, where there exists a separate time limit for both the hops. During the first hop, source carries out rateless coded transmission in the allotted time. Relay nodes which have successfully acquired target entropy forwards the information to the destination in the given time limit, using same rateless code at each node. Simultaneous transmissions by these relay nodes leads to faster accumulation of energy at the destination thereby reducing the decoding time. We have derived a closed-form expression of the average time for the first phase which allows fixed number of relays to decode the information. Analysis for achieving the time limit by these relays in the second phase has also been evaluated. Simulation results show that there exist an optimal number of decoding relays that leads to the lowest expenditure of the total time. Further, a closed-form expression for secrecy outage probability of this delay-constrained dual hop system has been derived.