GS-Tag: Design of a Generic Sensor Tag Based on RF Switches and COTS RFID System

With the development of the Internet of Things (IoT), substantial research efforts have been devoted to extending the sensing capability of commercial off-the-shelf (COTS) radio-frequency identification (RFID) tags. State-of-the-art approaches either demand sophisticated hardware redesign or are constrained to specific sensing capability, leading to increased costs and limited scalability. In this paper, we present the design of a generic sensor tag (GS-Tag) based on RF switches and COTS RFID system for transmission of generic sensor data. RF switches are connected in parallel with the RFID chip, and the GS-Tag modulates the sensor data by controlling the RF switches. Specifically, with the RF switches turned on, the tag’s chip is short-circuited, rendering it unreadable; conversely, turning off the RF switches makes the tag readable. The reader demodulates the data through the compatible electronic product code (EPC) protocol. A subtle dual RF switch scheme is adopted to extend the communication range. In addition to the battery-powered solution, we integrate an RF energy-harvesting module, develop a high-efficiency energy management circuit, and design an efficient task scheduling strategy to enable the GS-Tag to operate in a battery-free mode. We implement a prototype of GS-Tag with COTS RFID devices. Comprehensive experiments demonstrate that our designed GS-Tag can achieve an average packet reception rate (PRR) exceeding 99%, exhibits robustness to environmental disturbance, and facilitates coexistence of six GS-Tags with an average PRR of over 91%. Due to the dual RF switch scheme, the communication range of GS-Tag extends to 12 m. Besides, GS-Tag has an extremely low power consumption of just 3.98 μ W. A practical application is developed to accurately monitor temperature and ambient light intensity in an office environment while maintaining low power consumption. Our designed GS-Tag presents a cost-effective and compatible solution for expanding the sensing capabilities of COTS RFID system.