  As of today, large-scale wireless sensor networks are adopted for smart
building applications as they are easy and flexible to deploy. Low-power
wireless nodes can achieve multi-year lifetimes with an AA battery using
Bluetooth Low Energy (BLE) and Zig-Bee. However, replacing these batteries at
scale is a non-trivial, labor-intensive task. Energy harvesting has emerged as
a potential solution to avoid battery replacement but requires compromises such
as application specific sensor node design, simplified communication protocol
or reduced quality of service. We show the design of a battery-free sensor node
using commercial off the shelf components, and present Pible: a Perpetual
Indoor BLE sensor node that uses an ambient light energy harvesting system and
can support numerous smart building applications. We show trade-offs between
node-lifetime, quality of service and light availability and present a
predictive algorithm that adapts to changing lighting conditions to maximize
node lifetime and application quality of service.
