TY - EJOU
AU - Tian, Zengshan
AU - Yang, Weiqin
AU - Jin, Yue
AU - Xie, Liangbo
AU - Huang, Zhengwen
TI - MFPL: Multi-Frequency Phase Difference Combination Based Device-Free Localization
T2 - Computers, Materials \& Continua
PY - 2020
VL - 62
IS - 2
SN - 1546-2226
AB - With the popularity of indoor wireless network, device-free indoor
localization has attracted more and more attention. Unlike device-based localization
where the target is required to carry an active transmitter, their frequent signal scanning
consumes a large amount of energy, which is inconvenient for devices with limited
energy. In this work, we propose the MFPL, device-free localization (DFL) system
based on WiFi distance measurement. First, we combine multi-subcarrier characteristic
of Channel State Information (CSI) with classical Fresnel reflection model to get the
linear relationship between the change of the length of reflection path and the
subcarrier phase difference. Then we calculate the Fresnel phase difference between
subcarrier pairs with different spacing from CSI amplitude time series. Finally, we get
the change of the length of the reflection path caused by target moving to achieve
distance measurement and localization. Using a combination of subcarriers with
different spacing to achieve distance measurement effectively broadens the maximum
unambiguous distance of the system. To solve the complex non-linear problem of the
intersection of two elliptic equations, we introduce Newton's method to transform the
non-linear problem into a linear one. The effectiveness of our approach is verified
using commodity WiFi infrastructures. The experimental results show our method
achieves a median error of 0.87 m in actual indoor environment.
KW - Indoor localization
KW - WiFi
KW - channel state information
KW - fresnel phase difference
KW - reflection path length
DO - 10.32604/cmc.2020.07297