Feedback Enhances Simultaneous Wireless Information and Energy Transmission in Multiple Access Channels
Abstract: In this paper, the fundamental limits of simultaneous information and energy transmission in the two-user user Gaussian multiple access channel with feedback (G(G MAC-F) F) and without feedback (G-MAC) (G MAC) are fully characterized. More specifically, all the achievable information nformation and energy transmission rates (in bits per channel use and energy-units units per channel use, respectively) are identified. Furthermore, the fundamental limits on the individual and sum sum- rates given a minimum-energy minimum rate ensured at an energy harvester harvester are also characterized. In the case without feedback, an achievability scheme based on power power-splitting splitting and successive interference cancellation is shown to be optimal. Alternatively, in the G G-MAC-F case, a simple yet optimal achievability scheme based on power-splitting power and Ozarow’s capacity achieving scheme is presented. Finally, the energy transmission enhancement induced by the use of feedback is quantified. Feedback can at most double the energy transmission rate at high SNRs when the information transmission sum-rate rate is kept fixed at the sum-capacity sum capacity of the G-MAC, G but it has no effect at very low SNRs.