Localization - uni

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Transcript Localization - uni

Radu Poenaru
Cosmin Catanoaie
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Safety: identify a location of a person or
object
Entertainment: discovering the nearest
restaurant
Business: whereabouts of a logistic fleet
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Emergency medical services (EMS) In 1487, the first
recorded use of ambulance was by the Spanish army
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Yellow Pages First produced in 1886 by Reuben Donnely
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Local weather and traffic broadcast Since 1960s, radio
traffic report has been very popular in US and on May 2nd
1982 the weather channel (TWC) went on the air.
Emergency phone services
◦ In 1968, AT&T and FCC came up with this nation-wide emergency
phone number - 911 (112 across EU and 999 in UK
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Position :spatial coordinates, single point in the Cartesian
coordinate.
Location is associated with a certain place in the real world.
LoCation Service (LCS) - exclusively deals with the localization of
target, and also makes the resulting location data available to
external actors.
Location Based Service (LBS) is the service that ads value to target
locations provided by LCS. It uses knowledge of a mobile device's
location to offer value to the mobile subscriber or to a third party.
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Satellite positioning systems
◦ GPS
◦ aGPS
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Positioning in mobile networks
◦ Mobile based solutions
◦ Network based solutions
◦ Mobile-assisted solutions
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Oldest one from the frameworks presented
It isn't the first positioning system,
But the one with the most success and longevity,
started as a military project in 1957.
Needs for its functioning:
 you need three satellites to get your precise
position in the device line of sight, unobstructed
for entire period of measurement,
 four if you want also the elevation.
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Data loggers – log data as it arrives and here we
can include almost all devices with user interface
Data pushers – the kind of devices using for
tracking logistic fleet in real-time
Data pullers – almost the same as the pushers,
but instead of sending by their own at specific
intervals data to the central location, these ones
can be queried as needed
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aGPS, the short form of Assisted Global Positioning System
uses triangulation to augment traditional GPS location
tracking.
when GPS receivers power on, they can take minutes to
acquire the proper satellites for triangulation.
aGPS speeds up the process by using another method of
triangulation, typically cell phone towers or WiFi hotspots,
to cut down the time from two or three minutes to 10-20
seconds maximum.
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GPS system has difficulty providing reliable positions
in poor signal conditions - tall buildings (resulting in
multipath), indoors or under trees
In addition, when first turned on in these conditions,
some non-assisted GPS units may not be able to
download the almanac and ephemeris information
from the GPS satellites, rendering them unable to
function until a clear signal can be received
continuously for up to 40 seconds.
aGPS receiver can address these problems in several ways:
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The assistance server can locate the phone roughly by which cell site it is
connected to on the cellular network.
The assistance server has a good satellite signal, and lots of computation
power, so it can compare fragmentary signals relayed to it by cell phones,
with the satellite signal it receives directly, and then inform the cell phone
or emergency services of the cell phone's position.
It can supply orbital data and/or almanac for the GPS satellites to the cell
phone, enabling the cell phone to lock to the satellites faster in some cases.
The network can provide atomic time (Accurate Time Assistance)
Simply capturing a brief snapshot of the GPS signal, with approximate time,
for the server to later process into a position.
By having accurate, surveyed coordinates for the cell site towers, it has
better knowledge of ionosphere conditions and other errors affecting the
GPS signal than the cell phone alone, enabling more precise calculation of
position.
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Positioning is carried out in mobile device and sent
back to the network
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Requires the installation of client software on the
handset to determine its location.
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Requires the active cooperation of the mobile
subscriber as well as software that must be able to
handle the different operating systems of the handsets
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Difficulty of convincing different manufacturers to
cooperate on a common mechanism
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Issue of foreign handsets that are roaming in the
network
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Uses network infrastructure to identify the
location of the handset
Accuracy varies, with cell identification as the
least accurate
Requirement to work closely with the service
provider
Positioning methods
 Cell identity and timing advance
 Uplink time of arrival (TOA)
 Enhanced observed time difference (E-OTD)
 Assisted GPS
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Estimating position using WLAN access point
radio propagation
Requires a plurality of Wi-Fi access points in a
target area.
The Wi-Fi access points are positioned at
geographic locations and have signal coverage
areas.
Geographically known location of the Wi-Fi
access point, dividing the signal coverage area of
the Wi-Fi access point into at least one section
Requires the determination of radio propagation
characteristics for each section.
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Nearest sensor
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Triangulation/trilateration
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RF fingerprinting
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Supplier approaches
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First of all: each method presented has its
strengths and weaknesses.
None of these is the perfect positioning
system
yet they all can collaborate in order to give
the estimated but not the precise position of
a user
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Has a plethora of satellites at its disposal,
offering almost anywhere in the world a precision in
meters.
Devices are small enough to be inserted even in phones;
smart enough to do their job or even more by tracking
many satellites in the same time and eating less power,
affording the usage of this service for hours in a row.
But it needs clear sight to the sky in order to see at least
3 satellites and needs quite a long time in this busy era
to get a clear position and be able to pinpoint the
location on a map.
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helps by relying not only on satellites but also on
GSM towers, locating and triangulating them too.
Knowing their location, the power of the emitted
signal, the user can be easily triangulated.
Especially useful in crowded cities, where many GSM
antennas are installed removes the need for a clear
sky.
Thus, it allows even in places surrounded by tall
buildings to have a good enough precision while
locating the position on the map.
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Continues the movement from the sky to ground bases by
replacing completely the satellites from the picture.
In developed countries there are a lot of GSM towers in urban
areas
doesn’t eat more power in phones- knows by default how to
measure and get the tower’s id,
there is just a software issue to get the associated geographical
positions
Triangulate the user’s position based on the strength of signal.
But if you’re in a remote area, like in mountains, where there
are few emitters the quality of location falls dramatically.
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Newborn technology created out of the people
need to communicate.
For some business a nice feature to offer,
especially for the large fast foods
Ithe big cities these hotspots are countless, thus
some smart guys invented a positioning system
based on tracking these hotspots location
It offers sometimes a comparable precision in
comparison with the classic – the GPS system.
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No method is perfect
GPS needs clear sky,
aGPS improves this but still needs some satellites to be
seen,
GSM works like a charm if you have lots of antennas but
falls dramatically if you’re in a remote place
WiFi positioning is good in cities, but absolutely lacks in
remote zones.
Only the composition of all can cover all the situations
encountered in a normal life – crowded city when going
to work and big, empty spaces when going to
mountains to relax.
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Questions ?