This paper discusses energy-efficient power control for device-to-device (D2D) communication in 5G networks, focusing on the uplink of an OFDMA system involving both cellular users and D2D pairs. The authors employ fractional programming and non-cooperative game theory to optimize power allocation, demonstrating improved energy and spectral efficiency through various methods, including closed-form expressions. Simulations validate the advantages of the proposed algorithms over existing ones in terms of execution time and efficiency gains.