Introduction
Dr. Miguel A. Labrador
Department of Computer Science & Engineering
labrador@csee.usf.edu
http://www.csee.usf.edu/~labrador
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Outline
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Location Based Information Systems (LBIS)
LBIS challenges
Location-Based Services (LBS) applications
Location provider architectures
Software architecture
A complete LBS example
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Location Based Information Systems
• Systems that integrate advances in mobile phones, software
development platforms, databases, positioning technology,
Geographic Information Systems (GIS), and communications
• All combined make possible the creation of Location-Based
Information Systems (LBIS) and Location-Based Services (LBS)
– Promise to change the way we live
• 3.25 billion mobile phone users in 2007
– Half the world’s population
• LBS subscribers using GPS-enabled cell phones expected to
grow from 12 M in 2006 to 315 M in 2011
– 20 M from 500 K in North America
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LBIS Challenges
• Many players and technologies involved, and many issues
unsolved
– Databases, GIS systems, positioning, applications
• Erroneous and variable information
– Accuracy of GPS fixes depend on positioning system, user location,
weather conditions, interferences, etc.
• Cellular communication networks
– Wireless transmission problems, such as fading, interferences,
disconnections, low bandwidth, etc.
• Cell phones
– Very resource-constrained device in terms of processing power,
storage, and energy capabilities
• Operating systems and interoperability
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Location-Based Services (LBS)
• An application that provides users with information based on the
geographical position of the mobile device
• Main difference from other applications/systems
– Availability of the user’s position in real-time
– This single difference makes a BIG difference
• Initial LBS systems were subscription-based
– Traffic congestion notifications based on roads selected from a
Web site
– Received congestion updates about I-75 when on travel in NYC!
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Types of LBS Applications
• LBS can be either Reactive (“pull”) or Proactive (“push”)
• A Reactive LBS application is triggered by the user who, based
on his current location, queries the system in search of
information
• Many examples
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Finding restaurants or places of interest
Obtaining directions
Locating people
Obtaining weather information
Sending emergency notifications to police, insurance companies,
roadside assistance companies, etc.
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Types of LBS Applications
• In Proactive LBS applications, on the other hand, queries or
actions are automatically generated by the LBIS once a
predefined set of conditions are met
• System needs to continuously know where you are and evaluate
the predefined conditions
• Many examples as well
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Geofencing, e.g., children outside predefined boundary
Fleet management
Real-time traffic congestion notifications
Location-based advertisement
Real-time friend finding
Proximity-based actuation
Travel assistant device for riding public transportation, tourism,
museum guided visits, etc
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Location
• In LBIS and LBS applications everything is about LOCATION
• Important to know about different players and techniques used
in the provision of location information
• A location provider may or may not be the same entity providing
the location-based service to the user
• According to who provides the location information, the system
can be categorized as network-based, mobile-based, and
location provider-based
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Network-Based Location Provider
• Usually the same cellular network carrier
• Carrier locates the user and stores his location in a database
within its network
• LBS provider needs to obtain permission and/or pay for
obtaining user location information
• LBS application needs mechanisms to query the DB
• Preferred way of cellular carriers
– Maintain ownership and control of the location information
– Additional revenues
• Have not accelerated the development of LBS
– Cellular networks need to install costly positioning technologies
– Carriers may limit the number and frequency of queries
• Limiting the developing of some applications, mostly real-time ones
– Applications need to be aware of which carrier the user belongs to
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Network-Based Location Provider
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Mobile-Based Location Provider
• Mobile device has the capability of obtaining the location
– GPS, cell network, both
• Location is sent to the LBS service provider and stored in its
database for future reference or processing
• Server application may or may not send information back to user
– Depends on application and predefined parameters
• Clients are not limited to cellular phones
– Any GPS-enabled device with communication capability
• Accelerated rapid development of LBS application
– Neither financial nor technical barriers
• Main disadvantage of this method is that it has the potential to
flood the network with location updates
– Different LBS providers may or may not share the locations
– A user may be sending same location to more than one LBS provider
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Mobile-Based Location Provider
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Location Provider-Based
• Meant to solve the flooding problem of mobile-based method
• Independent entity collects locations using different methods
and make them available to LBS providers
• Only business is to provide location information
• Scalable architecture; perhaps the best architecture for wide
deployment of LBS
– Provisions needed to guarantee fair price and include competition
• There are a few companies that provide location information
– Skyhook, Where, Veriplace, Loc-Aid Technologies, others
– In this class, we will use the mobile-based method
• GPS-enabled cell phones and network-based technologies
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Location Provider-Based
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A Complete LBIS Tracking Example
• General real-time tracking application with visualization
– Tracking devices, people, etc.
• Uses the mobile-based location provider architecture
• Proactive LBS application consisting of the following
components:
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Positioning system
Client device
Transport network
Main control station
Servers
• Standard and free software and standard protocols as much as
possible
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Hardware
• Positioning system
– GPS and Assisted GPS (A-GPS)
• Client device
– GPS-enabled cell phone or any device with GPS or embedded
positioning system
• Transport network
– Cellular network with data plan (GPRS or similar) or network
connectivity using Wi-Fi or any other IP-based networking
technology
• Main control station
– PC connected to the system to control service and visualize data,
e.g., set up geofence and Google maps
• Servers
– Database, GIS for geocoding and reverse geocoding, application
server for processing
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Software
• Java platform
– Java SE for clients and Java ME for resource-constrained devices
• Sun’s Glassfish as the application server
• Google ‘s Web Toolkit for visualization
– Google Maps and Google Earth
• Postgres, and object-oriented relational database
• PostGIS, Postgres’s add on to support geographic objects
• Standard communication protocols
– HTTP, TCP, UDP
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A Complete Tracking System Example
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Software Architecture
• Software architecture is needed in order to
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Have an organized system
Know who does what in the system
Understand data flow
Know about relationships between components
Know protocols and interfaces used
• Software architecture for the client and for the server
– An example follows
– Used in proactive, mobile-based location provider applications
related to transportation
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Software Architecture - Client
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Software Architecture - Server
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A Brief Look into the Future
• LBS, Human-Centric Sensing, Participatory Sensing
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Participatory Sensing
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