Optimal Power Control and Error Performance for Full-Duplex Dual-Hop AF Relaying Under Residual Self-Interference

This paper investigates optimal power allocation schemes at the relay and their impact on the error performance for a full-duplex, dual-hop, amplify-and-forward system using finite constellations and under residual self-interference. The variance of the interference is assumed to be proportional to the λ-th power of the transmitted power. The worst-case pairwise error probability (PEP) is considered as the performance criterion. To find the optimal power allocation, we first derive a closed-form expression for the derivative of the PEP. A simple bisection method is then applied to obtain the optimal scheme. An asymptotically optimal allocation in closed form is also obtained assuming high power regions. From this analysis, it is shown that power allocation leads to a better diversity performance than full power transmission. In addition, the error floor behavior observed in previous works can be eliminated through power allocation. Numerical results are finally presented to illustrate the advantage of the proposed scheme over full power usage.