A spectrally efficient nonorthogonal amplify-and-forward protocol for cooperative wireless networks

In wireless systems where half duplex transceivers are employed, most existing practical cooperative protocols achieve a spectral efficiency of 0.5 symbols per channel use (pcu). Recently a decode-and-forward protocol was developed to achieve a spectral efficiency of 2/3 symbols pcu. But there is no practical amplify-and-forward (AF) protocol that can achieve a spectral efficiency higher than 0.5 symbols pcu. In this paper, we develop a nonorthogonal AF protocol which achieves a spectral efficiency of 2/3 symbols pcu and provides almost the same bit error rate as the traditional orthogonal AF which has a spectral efficiency of 0.5 symbols pcu.