RFID Multi-hop Relay Algorithms with Active Relay Tags in Tag-Talks-First Mode
Internet of Things (IoT) has attracted much attention today. As the key component of IoT, the Radio Frequency Identification (RFID) network has been growing in usage. An RFID network is composed of a backend system (including the database), one or more readers, and several RFID tags. Most of the RFIT tags cannot transmit signals actively, except the active RFID tags. The active RFID tags may gather information from sensors and store the information for later delivery to the reader. To extend the coverage of the RFID network, some RFID multi- hop relay systems (using active RFID tag as relay tags) have been proposed. They are all designed in Reader Talks First (RTF) mode. That means multi-hop connections may be built up only when the reader queries and the tags response. On the contrary, in â€Tag Talks First (TTF)â€ mode, an active tag cannot report anything to the system if it cannot find an available reader in its sense area. It may occur when the reader is located out of the sense area of the tag, or the reader is out of service (but the tag still needs to find out another reader to join in the RFID network). If these active tags are connection-lost from the system, some emergence messages may be lost. In this paper, we propose two multi-hop relay algorithms used in TTF mode, which are designed for Free2move and 802.15.4 standard respectively. Simulation results show that with the help of the proposed algorithms, the loss performance in TTF mode is improved a lot. Besides, the energy performance and delay performance is also improved compared to not using multi-hop relay algorithms in TTF mode, but use periodical data collection in RTF modes instead.Â
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