Energy Efficiency in Multiple Antenna Machine-Type Communications With Reconfigurable RF Transceivers

In machine-type communication (MTC) networks, each node is equipped with a set of radio-frequency (RF) transceivers, antennas and power source. Besides, wireless nodes are typically battery-powered, whose recharging or replacement is often not viable or even impossible. Therefore, in such systems where energy is at a premium, minimizing power consumption improves energy efficiency and increases battery lifetime. In this paper, a novel energy-saving approach includes in the communication system model the use of reconfigurable RF transceivers. More specifically, the components involved in our power minimization framework are the power amplifier (PA) at the transmitter and the low noise amplifier (LNA) at the receiver, which are the blocks responsible for RF amplification and are on top of power consuming blocks in RF transceivers. Our goal is to show that RF circuits based on multimode operation can significantly improve the energy efficiency. We perform a joint selection of the best operating modes for PA and LNA circuits in different communication scenarios. Results show that by combining PA and LNA operating modes, an improvement of more than 75% in energy efficiency is obtained for multiple antenna communications, when compared to the state-of-the-art literature of non-reconfigurable amplifiers. Besides, we show that adapting spectral efficiency contributes towards improving energy efficiency. In this case, we consider different spectral efficiency values, including the effect that the PA operates at different backed-off power levels. In addition, when comparing single-input single-output (SISO) and multiple-input multiple-output (MIMO) transmission schemes, antenna selection (AS) outperforms the others schemes in terms of energy efficiency for short and moderate distances, but singular value decomposition (SVD) allows for longer communication distances.