To improve the reliability and efficiency in cooperative communications, a power optimized single relay selection scheme is\nproposed by increasing the diversity effort with an improved link-adaptive-regenerative (ILAR) protocol. The protocol determines\nthe forwarding power of a relay node by comparing the signal-to-noise ratio (SNR) at both sides of the node; thus it improves the\npower efficiency. Moreover, it also proposes a single relay selection strategy to maximize the instantaneous SNR product, which\nensures the approximate best channel link quality for good relay forwarding. And the system adjusts the forwarding power in real\ntime and also selects the best relay node participated in the cooperative forwarding. In addition, the cooperation in the protocol\nis analyzed and the approximate expression of the bit-error-rate (BER) and the outage probability at high SNRs are also derived.\nSimulation results indicate that the BER and outage probability of the relay selection scheme by the ILAR protocol outperformother\ncontrast schemes of current existing protocols. At BER of 10âË?â??2, the proposed scheme with ILAR protocol outperforms those of the\ndecoded-and-forward (DF), the selected DF (SDF), and the amplify-and-forward (AF) protocols by 3.5, 3.5 and 7 dB, respectively.\nMoreover, the outage probability of the relay system decreases with the growth of the relay number.Therefore, the proposed relay\nselection scheme with ILAR strategies can be properly used in cooperative communications for good reliability and high power\nefficiency.
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