Spectral efficiency optimisation in amplify and forward relay network with diversity using adaptive rate and adaptive power transmission

In this study, new transmission schemes are designed for the spectral efficiency optimisation in the amplify and forward relay network with diversity. The proposed schemes utilise both adaptive rate and adaptive power transmission with individual average power constraints for the relay and the transmitter. To obtain an analytical insight into the network performance, schemes with continuous rate adaptation are designed at first. Next, transmission schemes with discrete rate and power adaptation are developed for practical systems. An amplify-forward relaying scenario with diversity is considered in which signals at the destination are received from both the transmitter and the relay. Albeit, the schemes could be simplified for the network without diversity in which there is no path for the signal from the transmitter to the receiver. Schemes with constant power transmission are also designed and analysed. Numerical evaluations show that there is a considerable performance gain in using adaptive power transmission compared to the constant power scheme at the cost of a reasonable complexity increase.