Characterization of error in a Near-Field Electromagnetic Ranging (NFER) Real-Time Location System (RTLS)

Abstract

We provide results and error analysis for over four hundred individual measurements of a Near-Field Electromagnetic Ranging (NFER®) Real-Time Location System (RTLS). The system operated over ranges from 1.41m to 23.4m and the bulk of the points were taken "through wall" in a nonline-of-sight configuration. We break the error down into orthogonal range and transverse components in order to assess the relative impact of range versus bearing errors in the system. We found an average range error of 34.0cm, an average transverse error of 35.5cm, and a corresponding total location error of 55.1cm. These error values are on a per receiver basis, and will tend to reduce by 1 / N as measurements from N receivers are combined to yield a solution.

Wideband Signal Based Near-Field Electromagnetic Ranging for Indoor Localizatio

“…Therefore, the center frequency band signal is less affected by the noise. As shown in Figure 5a, the phase difference calculation results at (3,4,5,6) MHz have less variance than those at other frequencies. For the multisines, the signal power at all frequencies is almost the same.…”

“…In the near field, the signal strength suffers greater attenuation compared to the far field and the noise intensity is higher in the low frequency band [5]. Therefore, the low signal-to-noise ratio (SNR) seriously impacts the ranging accuracy of NFER system when the ranging distance is longer than 25m [6]. In order to improve the ranging accuracy, multiple frequencies approach is proposed in [7].…”

Capacitive User Tracking Methods for Smart Environments

“…That is why there has been so much research into real-time location systems (RTLS) [18] and other alternative, wireless, positioning and activity sensing methods for monitoring people in indoor environments [3,16]. These include ultrasonic [24], radio frequency [37,38,44], optical [9,22] and inertial-sensor [15,55] based techniques that require the person to actively carry a device. However, from the occupant's point of view these techniques are neither practical nor user-friendly because the user must always carry a tag or small electronic device on their person.…”

Adaptive time delay estimation algorithm for indoor near‐field electromagnetic ranging

“…Additionally, the signalto-noise ratio (SNR) will seriously impact phase accuracy. The system becomes rapidly unusable and the ranging error increases significantly when the SNR decreases [5]. Considering the aforementioned reasons, we need to find a better method to detect the phase difference.…”