One more hash is enough: Efficient tag stocktaking in highly dynamic RFID systems

An RFID system can greatly improve the efficiency of tagged object inventory setup and update. It is necessary to periodically take stock of tags and update the inventory accordingly (i.e., deleting absent tags and adding new tags) in dynamic scenarios such as warehouses and shopping malls. Fast tag stocktaking is critical for the dynamic RFID system management. Previous work can take stock of tags by either collecting IDs of all the tags in the system, which is known to be inefficient, or broadcasting a long indicator vector to save tag identification time, which is not compatible with current commercial-off-the-shelf (COTS) tags. In this paper, we propose HARN, a protocol that can quickly take stock of tags in dynamic RFID systems but is compatible with COTS RFID tags and easily applied in a real RFID system. HARN uses only one more hash in the standard EPC C1G2 protocol. It leverages the new hash to generate the random number (RN) for a tag that can be used for both channel contention and known tag recognition, which can save the tedious ID transmission from known tags to readers and greatly speed up the stocktaking of tags. Simulation results demonstrate that HARN improves stocktaking throughput by up to 3.8x when compared to the state-of-the-art solutions in dynamic RFID systems.