标题：RFID 3-D Indoor Localization for Tag and Tag-Free Target Based on Interference
作者：Liu M.; Wang H.; Yang Y.; Zhang Y.; Ma L.; Wang N.
作者机构：[Liu, M] School of Information Science and Engineering, Shandong University, Qingdao 266200, China.;[ Wang, H] School of Information Science and Engin 更多
来源：IEEE Transactions on Instrumentation and Measurement
关键词：Indoor localization; interference based; radio frequency identification (RFID); tagged and tag free.
摘要：Passive indoor localization has gained much attention recently. Numerous applications including storage management and somatosensory systems would benefit from accurate passive indoor localization. As a potential technology for the internet of things, radio frequency identification (RFID) has many advantages for indoor localization, such as low cost, parallel processing, and low complexity. In this paper, a passive indoor localization system, named Lobain, was proposed based on interference of ultrahigh frequency RFID tags. Using commercial off-the-shelf reader, antenna, and tags, this system, functions for tagged and tag-free item localization in 2-D and 3-D indoor environments. Small numbers of reference tags were used as sensors to improve performance and reduce cost. Unlike traditional methods, an improved propagation model and an innovative method were presented to extract a target's channel information from a complicated received signal. A relative phase wrapping integer method was presented to solve the phase wrapping problem of reference tags, and the least-squares method was used to optimize the tradeoff between number of reference tags and accuracy. A tag and tag-free items including shrimp chips, cola, and instant noodles were localized as single target in the evaluation experiments. The prototype achieved mean 2-D median localization errors of 5.9 (x-axis) and 8.2 cm (y-axis), and achieved mean 3-D median errors of 9 (x-axis), 6.7 (y-axis), and 13.3 cm (z-axis). IEEE