Power allocation strategy using node cooperation for transmit power minimization under correlated fading

Achieving security at the physical layer in the presence of eavesdropper has always remained a critical issue under adverse channel conditions. The present scenario has relay with multiple antenna to combat channel effects. We have designed system model so that the nodes cooperate among themselves for the available power, with the aim to minimize the total transmit power, under a secrecy rate constraint. Here the relay sends out a jamming signal in order to confuse the eavesdropper. We assume correlated fading in the relay channels. The channel is modeled taking into account the large scale fading and small scale fading as well, through inclusion of path loss exponent and Rayleigh fading effects. The optimal power requirements for the source and the jammers are determined subject to the constraint of secrecy rate. The power allocation also depends upon path loss exponent, distance and fading parameters. The corresponding relaying regions have been plotted for real, equal and real, unequal roots of source power. Real, equal roots of source power are independent of position of relay. From the simulations we observe that the region expands when relays are away from the source.