Optimization of a Modified Orthogonal Amplify-and-Forward Pairwise User Cooperation Scheme

Motivated by some observations regarding the structure of the optimal power allocation for an existing orthogonal amplify-and-forward (AF) pairwise cooperation scheme, we propose a modified orthogonal AF cooperation scheme that uses the channel resources more efficiently and hence provides a larger achievable rate region. We consider the jointly optimal allocation of the transmission power and the channel resource for that scheme. In particular, we derive a simple efficient algorithm for determining the allocations required to operate at any point on the boundary of the achievable rate region. The algorithm is based on a closed-form solution, derived herein, for the optimal power allocation for a given channel resource allocation, and on showing that the channel resource allocation problem is quasi-convex.