High-Accuracy Indoor Localization Based on Chipless RFID Systems at THz Band

Highly accurate indoor localization based on significantly low complex infrastructure has recently gained great interest for a variety of innovative location-based applications. In this regards, the chipless radio frequency identification (RFID) system is presented to be the low-cost solution, while time-based ranging using the ultrawide-band spectrum is promising to offer precise ranging capability. However, the current wide-band systems suffer from the spectrum and power limitations, which restrict the function of chipless RFID-based localization systems. Therefore, we propose terahertz (THz)-based chipless RFID localization system that enables a smart object localizing itself using the infrastructure composed from reference chipless tags. In more details, THz band offers huge bandwidth providing superior-resolution localization and large coding capacity. Moreover, we utilize the combination between dielectric resonator (DR) and lens to be designed as a frequency-coded chipless tag, where this combination increases the radar cross section of the chipless tags and, hence, extends their coverage zone. This cost-efficient design of the tag enables the dense deployment of low-cost infrastructure acting as reference anchors. Furthermore, we investigate the link budget of the proposed system in order to characterize the tag and distance-dependent spectral windows that are feasible for RFID-based localization. Afterward, the time-domain backscattered signal from a DR-Lens tag is analyzed in order to perform ranging and to calculate the relative distances between the DR-Lens tags and the reader leading to determining the reader position. Measurements are performed to prove the concept of the DR-Lens tag, while the numerical simulation is conducted to evaluate the proposed localization system. Simulation results show that the proposed system can reach superior accuracy of millimeter-levels.