Secrecy Analysis in Wireless Network With Passive Eavesdroppers by Using Partial Cooperation

This paper proposes a new location-based multicasting technique, for dual phase amplify-and-forward (AF) large networks, aiming to improve the security in the presence of non-colluding passive eavesdroppers. These eavesdroppers could also be part of this cooperative network as relays. In order to reduce the impact of these eavesdroppers on the network security, we propose a new transmission strategy where, for the first hop of each transmission time, while the destination is jamming, the source randomly chooses a different subset <inline-formula><tex-math notation="LaTeX">$K$</tex-math></inline-formula> of the total <inline-formula><tex-math notation="LaTeX">$T$</tex-math></inline-formula> relays, to transmit its message toward the destination. For practical implementation, sectoral transmission can be achieved with analog beamforming at the source's side. In the second hop, using the distributed beamforming technique, the <inline-formula><tex-math notation="LaTeX">$K$</tex-math></inline-formula> AF relays retransmit the received signal to the destination. We analytically demonstrated that the proposed technique decreases the probability of choosing the same sector that has certain eavesdroppers again, for each transmission time, to <inline-formula><tex-math notation="LaTeX">$K/T$</tex-math></inline-formula>. Moreover, we also show that the secrecy capacity scaling of our technique is still the same as for broadcasting. Hereafter, the lower and upper bounds of the secrecy outage probability are calculated, and it is shown that the security performance is remarkably enhanced, compared to conventional multicasting technique.