Optimizing Location and Power of Chargers to Reduce Interference in Battery-Less WSNs

Battery-free wirelessly powered sensor networks (WPSNs) are an important step for the Internet of Things (IoT) applications mainly toward achieving an infinite lifetime of sensing infrastructure. The nodes in battery-less WPSNs harvest and store energy in super-capacitors from RF signals that are periodically transmitted by power beacons (PBs) or chargers. However, the sensor nodes covered by multiple PBs become unreliable due to overlapping signals from chargers. In this article, we minimize the number of PBs keeping a focus on the unreliability because of the interference of signals in the heterogeneous battery-less wireless sensor networks (BL-WSNs). We propose algorithms to first optimally place the power beacons [optimal power beacon location (OPBL)] and then to adapt the power of the chargers with an integer linear program (optimal power adaptation (OPA)-ILP) such that interfering nodes and data transmission time (DTT) can be reduced. Comprehensive simulation results show our proposed algorithms minimize the interfering nodes in 60% and 90% of cases, respectively. The DTT is reduced by 30% in 36% of cases by OPBL and 50% in 72% of cases by OPA-ILP in comparison to the state of the art.