Minimum Sum-Power Design of a Cooperative System using the Amplify and Forward Protocol

In this paper, based on amplify-and-forward protocol, we design both transmitters and receiver of a cooperative network, such that the equivalent communication link achieves a given target rate using the minimal overall transmit sum power. In particular, since the problem is not convex, the design method makes use of an iterative procedure which determines the power allocation by the best eigenvector of a suitable channel matrix which in turn depends on the power allocate at the previous iteration. Based on this solution, we compare, in terms of consumed energy, the cooperative communication and the direct communication. From this comparison, we determine the condition that makes cooperative communications, based on amplify-and-forward protocol, more convenient than direct communications.