LAUSR

In directional energy transmissions, a radio frequency (RF) energy source needs to monitor each sector to achieve higher RF energy transmission efficiency. However, since the location of harvesting nodes can be dynamically changed in mobile environments, it is difficult to obtain the exact numbers of harvesting nodes and the distance between harvesting nodes and the RF energy source in all sectors within limited time. In such a situation, the operations of the RF energy source (i.e., monitoring sectors and transmitting the RF energy) can be modeled by a partially observable Markov decision process (POMDP), which has high complexity to be solved. As a practical solution, we propose an observation-based directional energy transmission algorithm (OB-DETA) that estimates the efficiency of energy transmission in sectors and transmits the RF energy to the selected sectors with high energy transmission efficiency (i.e., sectors with lots of non-fully-charged harvesting nodes around the RF energy source). Evaluation results are given to demonstrate the effectiveness of OB-DETA over the comparison schemes in terms of the RF energy transmission efficiency.