—Energy Efficiency (EE) has become one of the main challenges for the development of wireless communication systems. Thus, many researchers are investigating new solutions to save power. For this reason, in this paper we apply a method based on modulation and coding scheme (MCS) for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) systems. The MCS scheme is a powerful method known by its ability to improve the spectral efficiency. Our goal in this paper is to investigate the performance of MCS mechanism to diminish the transmitted power under some assumptions. Computer results show the throughput behavior in function of signal to noise ratio (SNR) for different selection of modulation and coding rate. Then, we draw the plot of bit error rate (BER) versus SNR and versus the energy per bit to noise power spectral density ratio (E b /N o).