1,182 research outputs found
A survey on Human Mobility and its applications
Human Mobility has attracted attentions from different fields of studies such
as epidemic modeling, traffic engineering, traffic prediction and urban
planning. In this survey we review major characteristics of human mobility
studies including from trajectory-based studies to studies using graph and
network theory. In trajectory-based studies statistical measures such as jump
length distribution and radius of gyration are analyzed in order to investigate
how people move in their daily life, and if it is possible to model this
individual movements and make prediction based on them. Using graph in mobility
studies, helps to investigate the dynamic behavior of the system, such as
diffusion and flow in the network and makes it easier to estimate how much one
part of the network influences another by using metrics like centrality
measures. We aim to study population flow in transportation networks using
mobility data to derive models and patterns, and to develop new applications in
predicting phenomena such as congestion. Human Mobility studies with the new
generation of mobility data provided by cellular phone networks, arise new
challenges such as data storing, data representation, data analysis and
computation complexity. A comparative review of different data types used in
current tools and applications of Human Mobility studies leads us to new
approaches for dealing with mentioned challenges
CT-Mapper: Mapping Sparse Multimodal Cellular Trajectories using a Multilayer Transportation Network
Mobile phone data have recently become an attractive source of information
about mobility behavior. Since cell phone data can be captured in a passive way
for a large user population, they can be harnessed to collect well-sampled
mobility information. In this paper, we propose CT-Mapper, an unsupervised
algorithm that enables the mapping of mobile phone traces over a multimodal
transport network. One of the main strengths of CT-Mapper is its capability to
map noisy sparse cellular multimodal trajectories over a multilayer
transportation network where the layers have different physical properties and
not only to map trajectories associated with a single layer. Such a network is
modeled by a large multilayer graph in which the nodes correspond to
metro/train stations or road intersections and edges correspond to connections
between them. The mapping problem is modeled by an unsupervised HMM where the
observations correspond to sparse user mobile trajectories and the hidden
states to the multilayer graph nodes. The HMM is unsupervised as the transition
and emission probabilities are inferred using respectively the physical
transportation properties and the information on the spatial coverage of
antenna base stations. To evaluate CT-Mapper we collected cellular traces with
their corresponding GPS trajectories for a group of volunteer users in Paris
and vicinity (France). We show that CT-Mapper is able to accurately retrieve
the real cell phone user paths despite the sparsity of the observed trace
trajectories. Furthermore our transition probability model is up to 20% more
accurate than other naive models.Comment: Under revision in Computer Communication Journa
Estimating Movement from Mobile Telephony Data
Mobile enabled devices are ubiquitous in modern society. The information gathered by
their normal service operations has become one of the primary data sources used in the
understanding of human mobility, social connection and information transfer. This thesis
investigates techniques that can extract useful information from anonymised call detail records
(CDR). CDR consist of mobile subscriber data related to people in connection with the network
operators, the nature of their communication activity (voice, SMS, data, etc.), duration of the
activity and starting time of the activity and servicing cell identification numbers of both the
sender and the receiver when available.
The main contributions of the research are a methodology for distance measurements
which enables the identification of mobile subscriber travel paths and a methodology for
population density estimation based on significant mobile subscriber regions of interest. In
addition, insights are given into how a mobile network operator may use geographically located
subscriber data to create new revenue streams and improved network performance. A range of
novel algorithms and techniques underpin the development of these methodologies. These
include, among others, techniques for CDR feature extraction, data visualisation and CDR data
cleansing.
The primary data source used in this body of work was the CDR of Meteor, a mobile
network operator in the Republic of Ireland. The Meteor network under investigation has just
over 1 million customers, which represents approximately a quarter of the country’s 4.6 million
inhabitants, and operates using both 2G and 3G cellular telephony technologies.
Results show that the steady state vector analysis of modified Markov chain mobility
models can return population density estimates comparable to population estimates obtained
through a census. Evaluated using a test dataset, results of travel path identification showed
that developed distance measurements achieved greater accuracy when classifying the routes
CDR journey trajectories took compared to traditional trajectory distance measurements.
Results from subscriber segmentation indicate that subscribers who have perceived similar
relationships to geographical features can be grouped based on weighted steady state mobility
vectors. Overall, this thesis proposes novel algorithms and techniques for the estimation of
movement from mobile telephony data addressing practical issues related to sampling, privacy
and spatial uncertainty
Estimating Attendance From Cellular Network Data
We present a methodology to estimate the number of attendees to events
happening in the city from cellular network data. In this work we used
anonymized Call Detail Records (CDRs) comprising data on where and when users
access the cellular network. Our approach is based on two key ideas: (1) we
identify the network cells associated to the event location. (2) We verify the
attendance of each user, as a measure of whether (s)he generates CDRs during
the event, but not during other times. We evaluate our approach to estimate the
number of attendees to a number of events ranging from football matches in
stadiums to concerts and festivals in open squares. Comparing our results with
the best groundtruth data available, our estimates provide a median error of
less than 15% of the actual number of attendees
How much data is enough to track tourists? The tradeoff between data granularity and storage costs
Dissertation presented as the partial requirement for obtaining a Master's degree in Information Management, specialization in Knowledge Management and Business IntelligenceIn the increasingly technology-dependent world, data is one of the key strategic resources for organizations. Often, the challenge that many decision-makers face is to determine which data and how much to collect, and what needs to be kept in their data storage. The challenge is to preserve enough information to inform decisions but doing so without overly high costs of storage and data processing cost. In this thesis, this challenge is studied in the context of a collection of mobile signaling data for studying tourists’ behavioral patterns. Given the number of mobile phones in use, and frequency of their interaction with network infrastructure and location reporting, mobile data sets represent a rich source of information for mobility studies. The objective of this research is to analyze to what extent can individual trajectories be reconstructed if only a fraction of the original location data is preserved, providing insights about the tradeoff between the volume of data available and the accuracy of reconstructed paths. To achieve this, a signaling data of 277,093 anonymized foreign travelers is sampled with different sampling rates, and the full trajectories are reconstructed, using the last seen, linear, and cubic interpolations completion methods. The results of the comparison are discussed from the perspective of data management and implications on the research, especially the results of research with lower time-density mobile phone data
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