CSI-Based Indoor Localization

Abstract

Abstract-Indoor positioning systems have received increasing attention for supporting location-based services in indoor environments. WiFi-based indoor localization has been attractive due to its open access and low cost properties. However, the distance estimation based on received signal strength indicator (RSSI) is easily affected by the temporal and spatial variance due to the multipath effect, which contributes to most of the estimation errors in current systems. In this work, we analyze this effect across the physical layer and account for the undesirable RSSI readings being reported. We explore the frequency diversity of the subcarriers in OFDM systems and propose a novel approach called FILA, which leverages the channel state information (CSI) to build a propagation model and a fingerprinting system at the receiver. We implement the FILA system on commercial 802.11 NICs, and then evaluate its performance in different typical indoor scenarios. The experimental results show that the accuracy and latency of distance calculation can be significantly enhanced by using CSI. Moreover, FILA can significantly improve the localization accuracy compared with the corresponding RSSI approach.

Indoor detection of passive targets recast as an inverse scattering problem

“…The channel properties are represented in the form of the CSI. More in detail, the received signal can be defined as [12]  Only the CSI amplitude has been exploited for detection purposes. The phase information is fundamental but the calibration procedure has been avoided in this work to reduce as much as possible the computational complexity of the method.…”

“…The main challenge is to identify the components of the perturbations that are target-dependent. Toward this end, the PCA method [12] has been adopted to select the orthogonal components of the p-values not belonging to the noise subspace. The computed principal components…”

Localization based on standard wireless LAN infrastructure using MIMO-OFDM channel state information

“…Although many studies have investigated localization [2][3][4][5][6], it is not straightforward to apply their results to the problem of interest without requiring dedicated infrastructure or affecting the WLAN protocol structure. A few localization methods based on the IEEE 802.11 standards have been proposed in the literature [7][8][9] and implemented commercially. However, most of these methods use the received signal strength indicator (RSSI) as data for location determination [7,8].…”

“…The use of the RSSI usually requires a disincentive process of measurement-based training for adaptation to ever-changing environments because the RSSI is very sensitive to both large-scale shadowing and small-scale multipath fading prevalent in indoor environments. Recently, a method that uses channel state information (CSI) available through a network interface card [10] has been proposed [9]. Compared to the RSSI, the CSI is less sensitive to multipath fading.…”

“…Compared to the RSSI, the CSI is less sensitive to multipath fading. Nevertheless, the method proposed in [9], which is based on single-antenna APs, requires a disincentive measurement-based training process. The method proposed in the present paper uses the CSI obtained by the MIMO-OFDM receiver of each AP as data for location determination, without any measurement-based training process for adaptation to ever-changing environments.…”