Ambient radio signals, such as commercial FM radio broadcasts, provide an attractive opportunity of infrastructure-free indoor positioning with global coverage. While feasibility of FM-based indoor positioning has already been demonstrated in several studies, they provided little insight into the long-term performance of the ambient approach and its sensitivity to environment changes. This paper presents a year-long experimental evaluation of FM indoor positioning, using a multi-testbed dataset collected bi-weekly over the course of 12 months. Moreover, we improve the accuracy of classical receiver signal strength (RSS) fingerprinting by introducing a number of novel multipath-sensitive signal features. Finally, we analyze the robustness of FM signal features to human presence and weather conditions.

The increasing accuracy of indoor positioning systems makes their evaluation an increasingly challenging task. A number of factors are already known to affect performance of fingerprint-based systems: hardware diversity, device orientation, environment dynamics.This paper presents a new butterfly-like effect in localization experiments. The effect is caused by minor ground truth (GT) errors - that is, small deviations between calibration and test positions. While such deviations are widely considered as purely additive and thus negligible, we demonstrate that even centimeter-scale GT errors are amplified by small-scale radio fading and lead to severe multi-meter Wi-Fi positioning errors.The results show that fingerprint-based localization accuracy quickly deteriorates as GT errors increase towards 0.4 wavelength (5 cm for 2.4 GHz). Beyond that threshold, system's accuracy saturates to about one-third of its original level achievable with precise GT. This effect challenges the impact of the already known accuracy-limiting factors (such as cross-user tests, receiver diversity, device orientation and temporal variations), as they can be partially explained by minor GT errors. Moreover, for smartphone-in-a-hand experiments, this effect directly associates the evaluation outcomes with experimenters' diligence.

This study investigates the impact of small ground truth (GT) errors on indoor positioning systems based on Wi-Fi fingerprinting. The results demonstrate that even centimeter-scale GT deviations cause severe degradation of measured localization accuracy.

Despite the decades of efforts, indoor positioning remains an open research challenge. While existing solutions already demonstrate high accuracy, their inbuilding infrastructure — such as Wi-Fi access points or Bluetooth beacons — provides only a limited coverage. This paper investigates feasibility of accurate indoor positioning using broadcast digital TV signals, readily available in populated areas worldwide. We experiment with the classic received signal strength (RSS) fingerprinting, and introduce a novel approach based on channel state information (CSI), which leverages frequency-selective multipath fading of wideband TV signals. The proposed methods are experimentally evaluated on an extensive dataset of DVB-T signals, systematically collected in two large buildings over the course of 8 months. The results show that the proposed approach consistently outperforms RSS fingerprinting and achieves 92–98% localization accuracy. While this study is based on the European DVB-T signals, the proposed method is directly generalizable to other TV standards (such as ATSC, ISDB, DTMB and DMB) and wide-area TV white space (TVWS) networks.

While indoor positioning systems aspire for higher accuracy, their coverage is typically limited to buildings with dedicated hardware. A possible alternative is offered by infrastructure-free positioning methods. In particular, several studies have demonstrated feasibility of indoor positioning using broadcast FM radio signals, which are available in most populated areas worldwide. However, previous work provides little information about long-term performance of FM-based indoor localization.This paper presents a longitudinal study of FM indoor positioning based on received signal strength (RSS) fingerprinting. We evaluate system's performance on a large dataset of real-world FM signals, systematically collected in several large-scale multi-floor testbeds over the course of 9 months. We also investigate the impact of different classifiers, training schedules and fingerprint sizes on localization accuracy. The results demonstrate that well-trained FM-based system can provide reliable indoor positioning even several months after deployment.

This paper presents an ongoing long-term study exploring indoor positioning systems based on ambient radio signals (such as FM, TV and GSM). We introduce an open-source platform designed to facilitate data acquisition in indoor localization experiments. The platform is currently employed for the creation of a public dataset of geo referenced ambient radio signal samples. The paper discusses the system design as well as the challenges and current lessons of the year-long experiment.

Homo sapiens is a common, even if often uncredited, component of indoor positioning research. Despite the increasing number of automatic benchmarking platforms, performance of a positioning system is still typically evaluated by a graduate student with a smartphone in their hand. Powered by the varying levels of motivation, attention and spatial awareness, research assistants gather data while walking along predefined paths or visiting predefined locations. More importantly, however, these people are in charge of establishing the ground truth which has a direct impact on the final evaluation results.In this paper, we look into the widespread tacit assumption that human-based ground truth errors are negligibly small. Using a custom laser-based positioning method with centimeter-level accuracy, we experimentally invalidate the hypothesis of human localization infallibility in a series of 378 measurements with 7 volunteers. In static tests with three types of visual references, we observed human localization errors reaching values of 22 cm (with floor and ceiling markers) and up to 36 cm (with environmental landmarks). Such displacements can easily be the difference between the line-of-sight and radio-shadow locations and thus strongly affect the measured performance of a wireless positioning system.The results of this work outline the limits of human-based indoor positioning performance and highlight the importance of correct implementation and reporting of ground truth methodology in indoor localization research.

This paper presents an unconventional application of digital compass sensors for localization and activity monitoring in ambient assisted living scenarios. Benefits and limitations of the proposed approach are reviewed and compared to these of traditional tracking methods, such as wearable devices, surveillance cameras and device-free localization.

This paper presents a comparative pilot usability study of Dasher and an on-screen keyboard on a head-mounted display. Interaction logging data was captured along with subjective responses (via the SUS questionnaire). The results indicate that there is a strong need to develop text entry systems for smart glasses rather to simply adopt those that are already available. However, both approaches are useful when there is a need to enter private or sensitive data.

Two methods of object position and movement estimation in relation to the user of smart glasses were investigated. An active infrared and ultrasonic methods of the obstacle detection were presented and compared. Application of these methods depend on active transducers type (physical medium used), geometry and surface properties of detected objects and their movement direction and speed. In the article properties of both detectors were compared and applicability of both methods in mobile, battery operated environment such as eGlasses platform were compared.

This paper presents a comparative pilot usability study of Dasher and an on-screen keyboard on a head-mounted display. Interaction logging data was captured along with subjective responses (via the SUS questionnaire). The results indicate that there is a strong need to develop text entry systems for smart glasses rather to simply adopt those that are already available. However, both approaches are useful when there is a need to enter private or sensitive data.

We present a smart glasses application for helping colorblind people to distinguish problematic colors in daily life. The prototype processes a live video stream from the mobile camera, remaps colors according to the user needs, and displays the augmented result. Color transformation ensures high contrast between colors which are otherwise indistinguishable for the user.

This paper presents the concept of device-free indoor localization using only a passive receiver and ambient FM radio signals. Experimental results based on empirical measurements demonstrate the feasibility of the proposed approach. The authors also evaluate fine-grained localization performance of the system, its temporal stability, and highlight the role of frequency diversity for passive localization.

This work-in-progress paper presents a study of interaction techniques for mobile devices, with a focus on gaming scenarios. We introduce and explore usability and performance aspects of a novel compass-based control for tangible around-device interaction, and compare it with traditional mobile gaming controls, such as touchscreen thumbstick, swiping and tilt-based approaches.

Based upon the core concept of the LiveCity Project we focus on the specific City Cultural Experiences v2v Pilot, designed to allow for visitors at two defined locations to interact with one another in a joint experience and to get educational/entertainment benefits, originating directly from the museum content delivery. We discuss a set of semi-pervasive games (the so-called “Twin Cities” games) which are designed to bring people together at remotely twinned locations through the use of video-to-video communication and multi-touch interaction. We also present an early classification of video-to-video (v2v) interaction games that is designed to inform designers about the potential of such technologies. We classify them as: using video for awareness and communication, interacting with video and video as a game.

This paper investigates feasibility of device-free indoor localization using single passive receiver. Instead of local wireless nodes sharing one frequency channel, this work leverages multiple ambient FM radio stations. Experimental results demonstrate feasibility of the proposed approach and highlight the role of frequency diversity for passive localization.

This paper presents a work in progress focused on facilitation of cross-cultural awareness between citizens of two European cities. We aim to engage visitors of telecom museums in Athens and Luxembourg to learn more about both cities by means of collaborative games played on multitouch tables. We also explore how live video-to-video streaming influences players' behaviour and collaboration with remote players.

Localization plays an essential role in many ubiquitous computing applications. While the outdoor location-aware services based on GPS are becoming increasingly popular, their proliferation to indoor environments is limited due to the lack of widely available indoor localization systems. The de-facto standard for indoor positioning is based on Wi-Fi and while other localization alternatives exist, they either require expensive hardware or provide a low accuracy. This paper presents an investigation into localization system that leverages signals of broadcasting FM radio stations. The FM stations provide a worldwide coverage, while FM tuners are readily available in many mobile devices. The experimental results show that FM radio can be used for indoor localization, while providing longer battery life than Wi-Fi, making FM an alternative to consider for positioning.