Fingerprint-based methods are widely adopted for indoor localization purpose because of their cost-effectiveness compared to other infrastructure-based positioning systems. However, the popular location fingerprint, Received Signal Strength (RSS), is observed to differ significantly across different devices’ hardware even under the same wireless conditions.
We derive analytically a robust location fingerprint definition, the Signal Strength Difference (SSD), and verify its performance experimentally using a number of different mobile devices with heterogeneous hardware. Our experiments have also considered both Wi-Fi and Bluetooth devices, as well as both Access-Point (AP)-based localization and Mobile-Node (MN)-assisted localization.
We present the results of two well-known localization algorithms (K Nearest Neighbor and Bayesian Inference) our proposed fingerprint is used, and demonstrate its robustness when the testing device differs from the training device.
We also compare these SSD-based localization algorithms’ performance against that of two other approaches in the literature that are designed to mitigate the effects of mobile node hardware variations, and show that SSD-based algorithms have better accuracy. SSD A Robust RF Location Fingerprint Addressing Mobile Devices’ Heterogeneity
Existing in signal strength among wireless network cards, phones and tags are a fundamental problem for location finger printing. Current solutions require manual and error-prone calibration for each new client to address this problem. This paper proposes hyperbolic location finger printing, which records fingerprints as signal strength ratios between pairs of base stations instead of absolute signal-strength values has been evaluated by extending two well-known location fingerprinting techniques to hyperbolic location finger printing. The extended techniques have been tested on ten hour-long signal-strength traces collected network cards. The evaluation shows that the proposed solution solves the signal-strength difference problem without requiring extra manual calibration and provides a performance equal to that of existing manual solutions.
Hyperbolic Location Fingerprinting (HLF) to solve the signal-strength difference problem. The key idea behind HLF is that fingerprints are recorded as signal-strength ratios between pairs of base stations instead of as absolute signal strength. A client’s location can be estimated from the fingerprinted ratios by comparing these with ratios computed from currently measured signal-strength values.
Existing of HLF is that it can solve the signal-strength difference problem without requiring any extra calibration. The idea of HLF is inspired from hyperbolic positioning, used to find position estimates from time-difference measurements. The method is named hyperbolic because the position estimates are found as the intersection of a number of hyperbolas each describing the ratio difference between unique pairs of base stations.
HLF by extending two well-known LF techniques to use signal-strength ratios: Nearest Neighbor and Bayesian Inference in the HLF-extended techniques have been evaluated on ten-hour-long signal-strength traces collected with five different IEEE 802.11 clients. The traces have been collected over a period of two months in a multi- floored building in evaluation the HLF-extended techniques are compared to LF versions and LF versions extended with a manual solution for signal-strength differences.
We proposed a robust location fingerprint, namely, Signal Strength Difference (SSD), which was shown to outperform the traditional RSS fingerprint in terms of robustness across heterogeneous mobile devices, both analytically and experimentally. We analyze the robustness of SSD more elaborately, using several off-the-shelf Wi-Fi and Bluetooth devices.
Our approaches to collect the signal strength samples, namely, AP-based, where the RSS is measured at the AP, and MN-assisted, where the RSS is actually measured at the MN itself. In order to verify SSD’s robustness, we need to consider both of these scenarios. However, we have only considered the AP-based analysis and experiments.
In this paper, we show that, regardless of whether the signal strength samples are collected at the APs or at the MN, SSD is a more robust location fingerprint compared to the traditional RSS experimental test beds for Wi-Fi and Bluetooth. The Bluetooth test bed follows the AP based approach while the Wi-Fi test bed follows the MN assisted approach.
In this paper, we also considered two different test beds for Wi-Fi and Bluetooth which emulate MN-assisted and AP-based localization, respectively. The settings and surroundings of both test beds represent an indoor environment more practically compared to our initial lecture theater test bed of which only considered an AP-based localization approach.