Separation of multiple passive RFID signals using Software Defined Radio

TLDR

The paper presents a practical RFID reader design that enables reading multiple passive tags via joint decoding, reexamining lower‑layer opportunities. Implemented on GNU SDR, the reader uses 125 kHz MIT ID cards, rigorously analyzes physical‑layer communication, discusses extensions to HF tags, and its performance is evaluated through implementation and simulation. Rigorous physical‑layer analysis led to a complete system design that demonstrates that amplitude and phase differences enable efficient separation and decoding of multiple tags, offering opportunities to enhance industrial auto‑collision algorithms.

Abstract

We present a practical design of an RFID reader that is capable of reading multiple passive tags through joint decoding. The reader is implemented and analyzed using the GNU Software Defined Radio system. We use low frequency (LF) 125kHz commodity MIT ID cards in the experiment, and discuss extensions to decoding high frequency (HF) tags. This design reconsiders opportunities available in the lower layers of RFID design. Physical layer communication is analyzed rigorously and a complete system design is introduced as a result. We demonstrate this by exploring the differences in amplitudes and phase offsets among signal components, multiple tags can be separated and efficiently decoded using joint decoding. System performance is analyzed with both implementation and simulation. Based on these results, we summarize opportunities for improving industrial auto-collision algorithms with multiple-tag decoding capability.