This document proposes two power optimization techniques for wireless fronthauls in cloud radio access networks (C-RAN) that minimize energy consumption at remote radio heads while satisfying quality of service constraints. It derives a closed-form upper bound on system block error rate via union bound analysis. Then, it proposes adaptive transmission schemes and practical power optimizations based on both block error rate and pair-wise error probability to reduce energy use at remote radio heads while meeting a predefined non-zero block error rate quality of service requirement.