Wonder: Efficient Tag Identification for Large-Scale RFID Systems

Efficient tag identification is fundamentally required in large-scale RFID systems. Tag signal collision degrades identification efficiency as tag IDs involved in collision cannot be decoded. The situation becomes even worse in large-scale RFID systems when tag cardinality booms. Existing anti-collision protocols focus on either reducing collision probability or adopting spread spectrum techniques. Unfortunately, the former approach cannot resolve collision radically and the latter one occupies extra bandwidth resources. To address these issues, we propose to resolve tag collision using orthogonal Walsh code, in which tags map their IDs to a group of Walsh codes and transmit them sequentially. The reader can retrieve tag IDs by inverse mapping even under collision circumstances. We further design a new efficient tag identification protocol, Wonder, which reduces identification time without spreading the bandwidth. We conduct extensive simulations to examine its effectiveness and the results show that our protocol significantly improves identification efficiency over previous anti-collision protocols.