Link Scheduling in Rechargeable Wireless Sensor Networks With Imperfect Batteries

This paper considers the problem of generating the shortest time division multiple access (TDMA) schedule for use in rechargeable wireless sensor networks (rWSNs) with heterogeneous energy arrivals rates. This novel problem considers: 1) the time required by nodes to harvest sufficient energy to transmit/receive a packet; 2) harvest-use-store (HUS) energy harvesting and usage models, and; 3) battery imperfections, i.e., leakage, storage efficiency, and capacity. This paper shows the problem at hand, called link scheduling in harvest-use-store (LSHUS), is in general NP-Complete. Furthermore, it presents a greedy heuristic, called LS-rWSN, to solve LSHUS. Our experiments show that a longer energy harvesting time (leakage rate) from 1 to 20 (0% to 4%) increases the schedule length by up to 565.82 (44.54%) slots while reducing storage efficiency from 1.0 to 0.6 lengthens the schedule by up to 62.77%. In contrast, battery capacity has an insignificant effect, i.e., enlarging the capacity by 20 times decreases the schedule length by only 6.5%.