Performance of Energy Harvesting Receivers With Power Optimization

Abstract

The difficulty of modeling energy consumption in communication systems leads to challenges in energy harvesting (EH) systems, in which nodes scavenge energy from their environment. An EH receiver must harvest enough energy for demodulating and decoding. The energy required depends upon factors, like code rate and signal-to-noise ratio, which can be adjusted dynamically. We consider a receiver which harvests energy from ambient sources and the transmitter, meaning the received signal is used for both EH and information decoding. Assuming a generalized function for energy consumption, we maximize the total number of information bits decoded, under both average and peak power constraints at the transmitter, by carefully optimizing the power used for EH, power used for information transmission, fraction of time for EH, and code rate. For transmission over a single block, we find there exist problem parameters for which either maximizing power for information transmission or maximizing power for EH is optimal. In the general case, the optimal solution is a tradeoff of the two. For transmission over multiple blocks, we give an upper bound on performance and give sufficient and necessary conditions to achieve this bound. Finally, we give some numerical results to illustrate our results and analysis. Index TermsEnergy harvesting communication systems, Simultaneous energy and information transfer, Timeswitching, Joint power and rate optimization

Optimizing Energy Harvesting Decode-and-Forward Relays With Decoding Energy Costs and Energy Storage

“…In fact, due to the low energy consumption of an EH device in IoT, the decoder is the dominant source of energy consumption during reception [35]. Several papers have discussed the model of the decoding energy cost for receiving information, such as [35]- [37], which model the decoding power as an increasing convex function of the reception rate. Though there are some papers investigating relay systems considering the decoding cost, such as [21], [38]- [44], most of them discuss the situation when the random harvested energy arriving at the source, relay, and destination are independent of each other and are uncontrollable by the nodes [38]- [44].…”

“…However, they do not consider the energy harvested from ambient RF sources other than the dedicated TX. Some papers in our research group have discussed the energy decoding cost at the EH receiver in a point-to-point communication system, and have drawn many conclusions on the system design [34], [36], [37]. Ni et al [36] optimize the reception rate and time fraction of energy harvesting with different schemes.…”

“…Ni et al [36] optimize the reception rate and time fraction of energy harvesting with different schemes. Ni et al [37] extend the work in [36] to joint optimization of transmission power at the transmitter, reception rate and the time fraction for EH at the receiver in a point-to-point communication system. Ni et al [34] further discuss the dual-path structure of EH receivers considering both the internal resistance of the battery and the decoding cost, which constitutes a complex and difficult problem to deal with.…”

“…Ni et al [34], [36], [37] have studied the optimal TS optimization problems, accounting for decoding energy cost at an EH receiver in a point-to-point communication system; When it comes to a relay, which forwards the received information from the transmitter to the destination without a direct link, it is a very different problem. This is because the harvested energy must be carefully divided into two parts respective for decoding and forwarding the information and the process of EH also takes up part of the total processing time, in an EH system where EH and information transceiving share one antenna and one RF front-end.…”