A wireless transceiver power consumption model and two-hop vs. single-hop energy efficiency ratio

The energy efficiency [bit/J] of wireless communications can be improved by reducing transmitter power consumption per successfully transmitted bit. This power consumption depends on the transmit power (delivered to antenna) which is adjusted according to the channel conditions and performance metrics. We review a novel transceiver power consumption model for Class A, AB and B (linear) power amplifiers. The model is a better fit in the least squares sense than the existing affine model of the total transmitter power consumption as a function of the transmit power, within transmit power upper- and lower-bound. Using adaptive transmission power control, the total transmitter power consumption becomes dependent on channel loss, while received power margin allows link adaptation. For improved energy efficiency, we consider two-hop supportive relay. We review the border, in the space of channel losses of each link, which separates the regions of higher energy efficiency for two-hop and single-hop, respectively, and show its dependence on the model parameters. On the border, the channel losses of the first and second link in two-hop may shrink by more than 5 dB because of the model non-linearity. We present energy efficiency evaluation for a given energy consumption ratio between two-hop and single-hop transmissions in the space of channel losses. This ratio is a generalization of the border between regions of better energy efficiency of two-hop and single-hop, respectively. It is useful in estimating required channel estimation accuracy and feedback data rate. Acknowledgement: This work is a result of the projects TR32043 and III43002, funded by the Ministry of Education and Science of the Republic of Serbia, and has been discussed at the IC1004 COST Action in its Transmission Aspects Working Group.