Tracking systems are intended to determine the exact position of an object and are, nowadays, widespread. Objects intended to be tracked are actually tagged with bare or QR codes, have radio frequency identification (RFID) labels, or feature global positioning system (GPS) functionality, for example, smartphones with GPS receivers.

This well-written, easy-to-read paper provides a comprehensive literature review on asset tracking and ably describes the contribution of this research work throughout the description of the proposed architecture.

The great contribution of this work is the design of an innovative asset tracking system architecture aimed at maximizing smartphone battery life. The proposed architecture integrates classical tracking system technology with Bluetooth low-energy technology and smartphones. The authors provide a proof of concept for the proposed architecture and evaluate system performance. They obtain adequate results, thus showing that the proposed architecture contributes to lowering energy consumption.

I recommend reading this paper; however, the formulas from section 5 are a bit tricky.