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Co-location epidemic tracking on London public transports using low power mobile magnetometer

Khuong An Nguyen, Chris Watkins, Zhiyuan Luo
Conference Paper International Conference on Indoor Positioning and Indoor Navigation (IPIN 2017).


The public transports provide an ideal means to enable contagious diseases transmission.

This paper introduces a novel idea to detect co-location of people in such environment using just the ubiquitous geomagnetic field sensor on the smart phone. Essentially, given that all passengers must share the same journey between at least two consecutive stations, we have a long window to match the user trajectory.

Our idea was assessed by a painstakingly survey of over 150 kilometres of travelling distance, covering different parts of London, using the overground trains, the underground tubes and the buses.

On assessing the positioning accuracy of Google Tango in challenging indoor environments

Khuong An Nguyen, Zhiyuan Luo
Conference PaperInternational Conference on Indoor Positioning and Indoor Navigation (IPIN 2017).


The major challenges for optical based tracking are the lighting condition, the similarity of the scene, and the position of the camera.

This paper demonstrates that under such conditions, the positioning accuracy of Google's Tango platform may deteriorate from fine-grained centimetre level to metre level.

The paper proposes a particle filter based approach to fuse the WiFi signal and the magnetic field, which are not considered by Tango, and outlines a dynamic positioning selection module to deliver seamless tracking service in these challenging environments.

A performance guaranteed indoor positioning system using conformal prediction and the WiFi signal strength

Khuong An Nguyen
Journal Paper Journal of Information and Telecommunication (2017) | Volume 1, Issue 1 | Print ISSN: 2475-1839 | Taylor & Francis.


Indoor navigation provides the positioning service to the indoor users, where the GPS coverage is not available. The challenges for most signal-based indoor positioning systems are the unpredictable signal propagation caused by the complex building interiors, and the dynamic of the environment caused by the peoples' movements. However, most existing systems made no assumption about the quality of their predictions, which is crucial in such noisy indoor environment.

To address this challenge, this article proposes a confidence measure to reflect the uncertainty of the positioning prediction. More importantly, the users may control the size of the prediction set by setting the confidence level tailoring to their personal requirement. The proposed approach in this article has been validated in three real office buildings with challenging indoor environments, which indicated that it performed up to 20% more accurate than traditional Naïve Bayes and Weighted K-nearest neighbours (W-KNN) algorithms.

Dynamic route prediction with the magnetic field strength for indoor positioning

Khuong An Nguyen, Zhiyuan Luo
Journal Paper International Journal of Wireless and Mobile Computing (2017) | Volume 12, Issue 1 | Print ISSN: 1741-1084.


WiFi fingerprinting has been a popular approach for indoor positioning in the past decade. However, most existing fingerprint-based systems were designed as an on demand service to guide the user to his wanted destination.

This article introduces a novel feature that allows the positioning system to predict in advance which walking route the user may use, and the potential destination. To achieve this goal, a new so-called routine database will be used to maintain the magnetic field strength in the form of the training sequences to represent the walking trajectories. The benefit of the system is that it does not adhere to a certain predicted trajectory. Instead, the system dynamically adjusts the prediction as more data are exposed through-out the user's journey. The proposed system was tested in a real indoor environment to demonstrate that the system did not only successfully estimate the route and the destination, but also improved the single positioning prediction.

Reliable indoor location prediction using conformal prediction

Khuong An Nguyen, Zhiyuan Luo
Journal Paper Annals of Mathematics and Artificial Intelligence (2013) | Volume 74, Issue 1 | Print ISSN: 1012-2443.


Indoor localisation is the state-of-the-art to identify and observe a moving human or an object inside a building. However, because of the harsh indoor conditions, current indoor localisation systems remain either too expensive or not accurate enough.

In this paper, we tackle the latter issue in a different direction, with a new conformal prediction algorithm to enhance the accuracy of the prediction. We handle the common indoor signal attenuation issue, which introduces errors into the training database, with a reliability measurement for our prediction. We show why our approach performs better than other solutions through empirical studies with two testbeds. To the best of our knowledge, we are the first to apply conformal prediction for the localisation purpose in general, and for the indoor localisation in particular.

On the feasibility of using two mobile phones and WLAN signal to detect co-location of two users for epidemic prediction

Khuong An Nguyen, Zhiyuan Luo, Chris Watkins
Book ChapterProgress in Location-Based Services (2014) | Springer | Pages 63-78 | ISBN: 978-3-319-11878-9


An epidemic may be controlled or predicted if we can monitor the history of physical human contacts. As most people have a smart phone, a contact between two persons can be regarded as a handshake between the two phones. Our task becomes how to detect the moment the two mobile phones are close.

In this paper, we investigate the possibility of using the outdoor WLAN signals, provided by public Access Points, for off-line mobile phones collision detection. Our method does not require GPS coverage, or real-time monitoring. We designed an Android app running in the phone’s background to periodically collect the outdoor WLAN signals. This data are then analysed to detect the potential contacts. We also discuss several approaches to handle the mobile phone diversity, and the WLAN scanning latency issue. Based on our measurement campaign in the real world, we conclude that it is feasible to detect the co-location of two phones with the WLAN signals only.

Evaluation of Bluetooth properties for indoor localisation

Khuong An Nguyen, Zhiyuan Luo
Book ChapterProgress in Location-Based Services (2013) | Springer | Pages 127-149 | ISBN: 978-3-642-34202-8


Current indoor localisation systems make use of common wireless signals such as Bluetooth, WiFi to track the users inside a building. Amongst those, Bluetooth has been widely known for its low-power consumption, small maintenance cost, as well as its wide-spread amongst the commodity devices. Understanding the properties of such wireless signal definitely aids the tracking system design. However, little research has been done to understand the properties of Bluetooth wireless signal amongst the current Bluetooth-based tracking systems.

In this chapter, the most important Bluetooth properties related to indoor localisation are experimentally investigated from a statistical perspective. A Bluetooth-based tracking system is proposed and evaluated with the location fingerprinting technique to incorporate the Bluetooth properties described in the chapter.

Selective mixture of Gaussians clustering for location fingerprinting

Khuong An Nguyen, Zhiyuan Luo
Conference Paper 11th International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MobiQuitous 2014).


One of the challenges of location fingerprinting to be deployed in the real offices is the training database handling process, which does not scale well with increasing amount of tracking space to be covered. However, little attention was paid to tackle such issue, where the majority of previous work rather focused on improving the tracking accuracy.

In this paper, we propose a novel idea to enhance fingerprinting's processing speed and positioning accuracy with mixture of Gaussians clustering. We realised the key difference between fingerprinting and other un-supervised problems, that is we do know the label (the Cartesian co-ordinate) of the signal data in advance. This key information was largely ignored in previous work, where the fingerprinting clustering was based solely on the signal data information. By exploiting this information, we tackle the indoor signal multipath and shadowing with two-level signal data clustering and Cartesian co-ordinate clustering.

We tested our approach in a real office environment with harsh indoor condition, and concluded that our clustering scheme does not only reduce the fingerprinting processing time, but also improves the positioning accuracy.

Enhanced Conformal Predictors for indoor localisation based on fingerprinting method

Khuong An Nguyen, Zhiyuan Luo
Conference Paper 9th IFIP International Conference on Artificial Intelligence Applications & Innovations (AIAI 2013).


We proposed the first Conformal Prediction (CP) algorithm for indoor localisation with a classification approach. The algorithm can provide a region of predicted locations, and a reliability measurement for each prediction. However, one of the shortcomings of the former approach was the individual treatment of each dimension. In reality, the training database usually contains multiple signal readings at each location, which can be used to improve the prediction accuracy.

In this paper, we enhance our former CP with the Kullback-Leibler divergence, and propose two new classification CPs. The empirical studies show that our new CPs performed slightly better than the previous CP when the resolution and density of the training database are high. However, the new CPs performs much better than the old CP when the resolution and density are low.

Conformal Prediction for indoor localisation with fingerprinting method

Khuong An Nguyen, Zhiyuan Luo
Conference Paper 8th IFIP International Conference on Artificial Intelligence Applications & Innovations (AIAI 2012).


Indoor localisation is the state-of-the-art to identify and observe a moving human or object inside a building. Location Fingerprinting is a cost-effective software-based solution utilising the built-in wireless signal of the building to estimate the most probable position of a real-time signal data. In this paper, we apply the Conformal Prediction (CP) algorithm to further enhance the Fingerprinting method. We design a new nonconformity measure with the Weighted K-nearest neighbours (W-KNN) as the underlying algorithm. Empirical results show good performance of the CP algorithm.

A case study on the usability of NXT-G programming language

Khuong An Nguyen
Conference Paper 23rd Annual Workshop on Psychology of Programming (2011).


The release of the Lego Mindstorms kit has carried the flexibility and creativity of Lego into the world of robotics, whilst targeting a variety of children and adults audiences. To achieve this goal, a programming language called NXT-G was developed to provide everyone full control of the Lego Mindstorms kit, regardless of their programming experience.

In this project, the programming language ambition is tested through practical experiments. In a controlled experiment, twelve participants carry out four tasks using the NXT-G software and a Lego robot. Their performances are then analysed to confirm the stated claim.

Machine learning based WiFi location fingerprinting

Khuong An Nguyen
Thesis Ph.D Thesis, University of London.


Indoor localisation provides the positioning service to the indoor users, where the GPS coverage is not available. Much research effort has been invested into 'Location Fingerprinting', which is considered one of the most effective indoor tracking methods to date. Fingerprint-based approaches piggyback on top of the existing indoor communication layers such as the WiFi network to provide the location-based service. However, the challenges of fingerprinting are the huge training database, the dynamic indoor environment, and the WiFi fingerprints may struggle to provide fine-grained positioning accuracy at certain indoor positions. This thesis addresses the mentioned problems using several machine learning algorithms and additional information observed from the users and the indoor environment.

The proposed approaches in this thesis have been validated in the real offices with challenging indoor environments. One test bed has multiple buildings and floors, and has been previously used in the EvAAL 2015 indoor positioning competition, which provides a relative baseline for the proposed techniques. In particular, the regression and classification algorithms in this thesis were ranked second and third out of the 5 contestants, under the same competition's test domain. In addition, they performed up to 20% more accurate than traditional Naive Bayes and W-KNN algorithms.

Robot-based evaluation of Bluetooth fingerprinting

Khuong An Nguyen
Thesis M.Phil Thesis, University of Cambridge.


This thesis proposed and implemented a new affordable indoor tracking system. The Bluetooth signal was found to be very stable and is reliable for any indoor positioning system. The Fingerprinting method was employed to manipulate the Bluetooth signal at many positions in the office room. In addition, a robot was created to perform the complex and time-consuming data collection process.

An EMV (Chip & PIN) survey

Khuong An Nguyen
Thesis B.Sc Thesis, University of London.


The thesis was one of the first to investigate the structure of the UK Chip & PIN debit and credit cards. Particularly, we looked into CAMs (Card Authentication Methods) implemented by different banks to understand their policies.

A Java-based reader was developed to exchange information with all UK Debit/Credit cards, some overseas cards were also tested. The software can simulate an ATM machine to perform off-line PIN verification.

Semi-Automatic indoor fingerprinting database crowdsourcing with continuous movements and the social contacts

Khuong An Nguyen


Indoor localisation helps monitoring the positions of a person inside a building, without GPS coverage. In the past decade, much research effort have been invested into Indoor Fingerprinting, which is considered one of the most effective indoor tracking methods to date.

In recent years, some researches started looking at crowdsourcing the fingerprinting database with the contributions from indoor users via mobile phones or laptop PCs. However, the crowdsourcing process was greatly limited due to the lack of indoor reference, in contrast to the widespread use of GPS reference for outdoor crowdsourcing.

In this paper, we propose a novel idea to crowdsource the fingerprinting database without any preset infrastructure, landmarks, nor using any advanced sensors. Our idea is based on the observations that the users often carry a mobile phone with them, and there are multiple social contacts amongst those users indoor. First, we exploit the user's continuous movement indoor to refine the location prediction set. Our approach can be applied to enhance other systems. Second, we use a unique concept to detect the indoor social contacts with NFC by tapping the back of the two phones together. Third, we propose a novel idea to combine this social contact and the user's continuous movements to identify the exact entries with confidence in the fingerprinting database that need updating for crowdsourcing. Finally, we share our thoughts on automating the crowdsourcing process without any user input.

Spam filtering with Naive Bayes classification and the Porter stemming algorithm

Khuong An Nguyen
Technical report Natural Language Processing project, University of Cambridge.


Spam (junk-email) identification is a well-documented research area. A good spam filter is not only judged by its accuracy in identifying spam, but also by its performance.

This project aims to replicate a Naive Bayesian spam filter, as described in the "SpamCop: A Spam Classification & Organization Program" paper. The accuracy and performance of the filter are examined with the GenSpam corpus. In addition, the project investigates the actual effect of the Porter Stemming algorithm on such filter.