Ant Colony Optimization based Relay Selection for Secrecy Enhancement in Decode-and-Forward Relay Networks

In this paper, a novel relay selection scheme based on Ant Colony optimization (ACO) is formulated to enhance the secrecy of dual hop decode-and-forward (DF) cooperative relay networks in the presence of a passive eavesdropper. According to the probability of path selection in ACO, a path is selected based on the significance of channel gain (G) and fading coefficients (h). The algorithm has the flexibility of choosing the best relay in the following wireless scenarios, when (i) both channel gain and fading coefficients are significant (ii) only fading coefficients are significant and (iii) only channel gain is significant. A practical scenario where the channels undergo independent non-identical Rayleigh fading, and direct links exist between source to destination (S-D) and source to eavesdropper (S-E) is considered. The performance is evaluated based on secrecy rate (R
_S
) for the case of randomly distributed relays and for any eavesdropper location. Analysis is done for both partial relay selection (PRS) and best relay selection (BRS) schemes. The effect of relay nodes on secrecy capacity is also analyzed. Numerical results show the performance of the proposed scheme in different wireless scenarios in comparison to traditional relay selection scheme.