A peak power efficient cooperative diversity using star-QAM

In this paper, we propose a new simple relaying strategy with bit-interleaved convolutionally coded star quadrature amplitude modulation (QAM). Star-QAM is composed of multiple concentric circles of phase-shift keying (PSK). Exploiting this property, a hard limiter is used to enhance power amplifier (PA) efficiency at a relay. We analyze our proposed cooperation in terms of asymptotic pairwise error probability (PEP) and show that it can achieve the full diversity order conditioned on that the minimum free distance d
_free
of the convolutional codes is large enough. Finally, theoretical results and effectiveness of PA efficiency are confirmed by computer simulations.