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Wireless relay networks have caught a lot of attention recently due to their potential to enhance performance by combating fading effects. Numerous strategies have been proposed in the literature to enable cooperative diversity. Among them, decode-and-forward protocol has been well adopted because of its low implementation complexity. However, most decode-and-forward based schemes assume that the relay node has perfect error detection or has feedback information from the destination. In this paper, we design power profiles at the relay which enable diversity at the destination without any feedback or coding assumptions at the relay and source. Furthermore, the diversity orders enabled by any general power profile are quantified. We then summarize necessary and sufficient conditions on the power profiles to guarantee full diversity at the destination. The theoretical analysis is corroborated with numerical simulations.