Energy Harvesting Communication Using Finite Finite-Capacity Capacity Batteries With Internal Resistance
Abstract: Modern systems will increasingly rely on energy harvested from their environment. Such systems utilize batteries to smooth out the random fluctuations in harvested energy. These fluctuations induce highly variable battery charge and discharge rates, which affect the efficiencies of practical batteries that typically have non-zero zero internal resistance. In this paper, we study an energy harvesting communication n system using a finite battery with non-zero non internal resistance. We adopt a dual dual-path path architecture, in which harvested energy can be directly used, or stored and then used. In a frame, both time and power can be split between energy storage and data tran transmission. smission. For a single frame, we derive an analytical expression for the rate optimal time and power splitting ratios between harvesting energy and transmitting data. We then optimize the time and power splitting ratios for a group of frames, assuming non non-causal causal knowledge of harvested power and fading channel gains, by giving an approximate solution. When only the statistics of the energy arrivals and channel gains are known, we derive a dynamic programming programming-based based policy and propose three sub-optimal sub policies, s, which are shown to perform competitively. In summary, this paper suggests that battery internal resistance significantly impacts the design and performance of energy harvesting communication systems and must be considered.