1. Location Based Services
CE Software Development
13/04/2017
Location Based Services
What is a Location Based Service?
How is a LBS useful?
Components
What’s special about it?
Context
Adoption
Privacy
How does it work?
Services request processing
Mobile positioning
Architectural requirements
Lot to get through
Lecture 1 - Introduction

2. Introduction to LBS
A certain service that is offered to the users based on their location
An information service provided by a device that knows where it is and modifies the information it provides accordingly
Mobile services that utilise user location information to add value to the service
Usually require modifications in either the networks or the mobile device or both
It was first developed for the military and emergency services

3. LBS: Then
For how many years have we used these signs as the ONLY source for LBS?
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4. LBS: Now Location-based traffic reports:
Range query: How many cars on the motorway?
Shortest path query: What is the estimated time travel to reach my destination?
Location-based store finder:
Range query: What are the restaurants within five miles of my location?
Nearest-neighbor query: Where is my nearest fast food restaurant?
Location-based advertisement:
Range query: Send E-coupons to all customers within five miles of my store

5. It’s 4:30pm and Mum is stuck in traffic
inTouch checks her calendar and sees she’s supposed to pick up Cindy from ballet
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6. Mum’s phone senses that she is in a traffic jam, and automatically prepares a status message
Mum hits “send”, and Cindy sees that Mum is running late. Cindy decides to wait inside.

7. LBS: Why Now ? GIS/ Spatial Database Mobile GIS Web GIS LBS
Internet
Mobile Devices
GIS/ Spatial Database
Web GIS
LBS
Mobile Internet
Mobile GIS
LBS is a Convergence of Technologies
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8. LBS Applications
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9. LBS Components (1) Mobile Devices Communication Network
A tool for the user to request the needed information
The results can be given by speech, using pictures, text...
PDAs, Mobile Phones, Laptops, a car navigation unit, a toll box for road pricing in a truck
Communication Network
The mobile network
Transfers the user data and service request from the mobile terminal to the service provider
Transfers the requested information back to the user
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10. LBS Components (2) Positioning Component
For the processing of a service usually the user position has to be determined
The user position can be obtained either by using the mobile communication network or by using the Global Positioning System (GPS)
Further possibilities to determine the position are WLAN stations, active badges or radio beacons (indoor navigation)
If the position is not determined automatically it can be also specified manually by the user
Service and Application Provider
Responsible for the service request processing
Calculation of the position, finding a route, searching yellow pages with respect to position or searching specific information on objects of user interest
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11. LBS Components (3) Data and Content Provider
Service providers will usually not store and maintain all the information which can be requested by users
Geographic base data and location information is requested from the maintaining authority (e.g. mapping agencies) or business and industry partners (e.g. yellow pages, traffic companies)
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12. LBS- Context (1) Mobile user identity
Age and gender - children are unlikely to be interested in knowing about bars and pubs
Personal preferences – Language, style, imagery, colours
Location - the most commonly considered element of context
It allows information and services to be localized
Time - An entertainment’s active time might be used to determine if an event was still valid, for example a concert or a venue is open
Orientation - the direction a user is heading in and thus what is in front, behind and to either side of them
In a tourist guide this might be used to determine what historical building the user is facing
In a navigation service it is important to check the user is heading in the right direction
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13. LBS- Context (2) Navigation history Purpose of use
allows the users to see where they have been and what they have seen and done
orientate a user while they're are moving and allow them to backtrack if they get lost
help to build up a profile of the what the user is interested in, enhancing the provision of relevant information
Purpose of use
Defined by the activities, goals, tasks and roles of users. Different types of usage require different
Types of information
Types of presentation, for example maps, text or speech, and
Modes of interaction
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14. LBS- Context (3) Social and cultural situation Physical Surroundings
proximity to others
social relationships
collaborative tasks
Physical Surroundings
lighting level or how much ambient noise there
For example direct sunlight will make screens more difficult to read requiring the contrast to be adjusted
System Properties
to the computer infrastructure the user is employing
What type of device they are using and what are its capabilities
a continuous internet connection or it is only intermittent, bandwidth, the quality of the positioning information, e.g. the GPS coverage.
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15. LBS- Context How do services respond to context? Information level
Technology level
User interface level
Presentation level
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16. LBS- Privacy
Like many technologies, LBS have an enormous potential for good but they can also be misused.
The potential for misuse doesn’t invalidate the technology, but it does mean that we must be thoughtful about how we apply it, especially during its developmental stages.
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17. Major Privacy Threats YOU ARE TRACKED…!!!!
“New technologies can pinpoint your location at any time and place. They promise safety and convenience but threaten privacy and security”
Cover story, IEEE Spectrum, July 2003
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18. Major Privacy Threats

19. How does it Work?
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20. Positioning Methods
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21. Location Technologies
GPS - Global Positioning System
AGPS - Assisted GPS
Cell ID
Cell ID + Timing Advance
Signal Strength Based
AOA - Angle Of Arrival
TOA - Time Of Arrival
TDOA - Time Difference of Arrival
EOTD - Enhanced Observed Time Difference
Keypad based (click the address yourself)
Hybrid solutions
RF Fingerprinting (on phones that will support WLAN)
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22. GPS
With the launch of Sputnik in 1957, radio-based global positioning became a (theoretical) possibility
TRANSIT
This was a very crude form of GPS using only one satellite (1960s)
Submarines used it
Could only be used every minutes
Submarine had to be still
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23. Components of GPS and how it works
Space (e.g. satellites)
Control (i.e. a ground station at a known geographic location)
User
The GPS receiver precisely measures the time it takes a signal to travel from a satellite to the receiver
There are lots of satellites
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24. CE51600-1 Software Development
13/04/2017
Details
6 orbital planes, included at 55 degrees to the equator, each with 4 satellites
21 active satellites, 3 backups
Orbit the earth at 12,541 miles and have an orbital period of 11 hrs. 56 min.
Lecture 1 - Introduction

25. Satellite Triangulation
GPS receiver links to the handset
As reference to the nearest 3 satellites the receiver calculates the exact position

26. Selective Acquisition
The US military was concerned about the possibility of terrorists or other unfriendly people using GPS to precisely guide a missile (or other unfriendly device)
The deliberately introduced errors in the time embedded in the signal
This caused locations to be up to 100m off
Turned off on 2 May 2000
GPS III system will launch in 2014
GPSIII.pdf
Should be even more accurate than the 8m accuracy limit currently in place
Galileo is a European Union Equivalent
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27. Assisted GPS
Conventional GPS has difficulty providing reliable positions in poor signal conditions
When first turned on in these conditions, some non- assisted GPS units may not be able to download the information from the GPS satellites
GPS has a slow time to fix unless it is permanently tracking satellites
To solve the inherent restrictions with GPS, Assisted GPS was proposed
Assisted GPS is based upon providing GPS satellite information to the handset, via the cellular network
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28. A-GPS Assisted GPS gives improvements in Assistance Data
Time to First Fix
Battery Life
Sensitivity
Cost
Assistance Data
Satellite Position
Time information
Visible GPS List
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29. Cell ID (Cell of Origin)
Cell based positioning
No calculation
Least accurate than others
Accuracy is dependent on cell density
Compatible with all handset and GSM network
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30. Timing Advance (TA)
Power level or time taken at phone logged at Base Station
Calculation based on signal loss or time taken for signal travel
Compatible with all handset and GSM network
Resolution is 500 meters
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31. Signal Strength Based
Measure signal strength from the control channels of several Base Stations
If signal levels from 3 different BSs are known, it’s possible to calculate the location
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32. Time of Arrival (TOA) Location Measurement Units (LMU) at Base Station
Measure access requests from handset
Triangulation calculated from combined information
Compatible with all handset and GSM network
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33. AOA - Angle Of Arrival
Measure the angle of arrived signal between base station and mobile station
Location error increases as mobile is far from BSs
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34. Time Difference Of Arrival
Measure the time difference of arrived signal between base station and mobile station : Minimum three base stations
Mobile station locates at the intersection point which will be made by more than 3 hyperbolas
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35. Enhanced Observed Time Difference
Added device, LMU (Location Measurement Unit), whose location is known
LMU and mobile station measure the time difference of arrived signal from base station at the same time
Mobile station locates at the intersection point which will be made by more than 3 hyperbolas
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36. EOTD – Enhanced Observed Time Difference
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37. Keyboard Based You set your location! Example: Navigation Software:
Manually set origin
Manually set destination
Approve when each step is completed to get the next step instructions
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38. Lampposts Based
Last Mile company plans to offer Internet & LBS using street lampposts
A flash memory will be installed inside the lampposts and store info about local pubs, shops.
Cost: about £500 per lamppost
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39. Hybrid Solutions Based
Improve effectiveness
Extends the coverage of a solution e.g. AGPS
Common Hybrids
EOTD / AGPS
Cell ID / AGPS
Benefits of both systems realized increasing the accuracy and availability of any single method
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40. RF Fingerprint Based
Pinpointing wireless clients makes it easier to secure and manage wireless LANs
WLANs typically have used closest access point (closest AP) or triangulation technologies to track location
RF fingerprinting improves by taking into account the effects that a building or people will have on an RF signal - characteristics such as reflection, attenuation and multi-path
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41. RF Fingerprint Based
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42. Range Of Coverage AGPS,GPS, GPS Hybrids 5 m 100 m EOTD 300 m TDOA, AOA
Cell ID + TA
500 m
Cell ID
1000+m
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43. Major Technologies Table
Technology
Handset impact
Accuracy
Cell ID
none
Depends on the size of the cell
100m-3km
Cell ID + TA
500m
TDOA m
AOA
EOTD
yes
20-200m
GPS/AGPS
5-30m

44. Code of practice
Regulation play a major role in the shape and success LBS.
Regulation is likely to have an impact on the accuracy operators will provide and the use of handling user information
This will affect both technology choice and the availability and usability of user location information for different players
Location based service providers that use location data as part of their services must comply with the Industry Code of Practice For the Use of Mobile Phone Technology to Provide Passive Services in the UK
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ce.pdf
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