Backscatter Tag Positioning With PRS-Based RTT Measurement

The tag device uses backscatter modulation to communicate passively by modulating the reflected signal from the reader's transmission. The tag harvests energy from the reader's signal and uses it to modulate the backscatter, eliminating the need for an active transmitter. This self-service approach allows the tag to perform positioning measurements without consuming significant power from its own battery.

The system uses periodic positioning reference signals (PRS) transmitted by the reader at specific intervals. The tag responds to these periodic signals with backscatter measurements, allowing positioning to be performed at scheduled times rather than continuously. This periodic approach maintains positioning accuracy while significantly reducing overall power consumption compared to continuous active transmission.

The patent segments the communication function into two distinct parts: the reader handles all network communication and signal processing, while the tag only performs passive backscatter measurements. This segmentation allows multiple tags to operate simultaneously without their signals directly interfering with each other or the network, as each tag's backscatter signal is processed independently by its associated reader.

The reader acts as an intermediary that manages all communications for multiple tags. Instead of multiple tags communicating directly with the network (which would cause interference and congestion), each tag communicates only with its reader, and the reader aggregates and manages all network communications. This intermediary approach enables scalable deployment of multiple tags without proportionally increasing network interference or congestion.