1. Presented By:
HITESH KUMAWAT
E.I.C 4th year

2. Emergency service for subscriber safety.
Location sensitive billing.
Cellular Fraud detection.
Intelligent transport system services.
Efficient and effective network performance
and management.

4.  Whole service area is divided into several coverage areas known as
a “cell”. Each area has a separate base station(BS).
 Every BS is provided with a frequency of range 450 to 900 Mhz.
 The MTSO controls the BSS so that the subscriber can continue
his call without interruption.
 Tracking the location within the boundary of a cell in a
telecommunication network is known as “location based services”.

5.  A geolocation service provider provides
location information and location aware
sevices to subscribers.
 The service provider will contact the
location control center about the coordinates
of the mobile system (MS).
 The location control center will gather
information required to compute the MS’s
location.
GEOLOCATION SYSTEM
ARCHITECTURE [K0S00]

6. 1.HANDSET BASED MOBILE POSITIONING AND TRACKING
1.1 GLOBAL POSITIONING SYSTEM (GPS)
2. DIRECTION BASED GEOLOCATION
2.1 ANGLE OF ARRIVAL METHOD
3. DISTANCE BASED POSITIONING
3.1 TIME OF ARRIVAL(TOA)
3.2 TIME DIFFERENCE OF ARRIVAL(TDOA)
4. LOCATION TRACKING CURVE METHOD

7.  To locate the mobile telephone by
itself, the mobile telephone is provided
with a GPS receiver to calculate its
location.
 There should be an unobstructed line
of sight to four or more GPS satellites.
 GPS satellites broadcast signals from
space, which each GPS receiver uses
to calculate its three-dimensional
location (latitude, longitude, and
altitude) plus the current time
 GPS receivers are used in mobile
phones, vehicles, marine navigation
devices and military applications.

8.  The navigational signals transmitted by GPS satellites encode a variety of
information including satellite positions, the state of the internal clocks, and the
health of the network. Message is send at a rate of 50 bits per second.
 The first part of the message encodes the week number and the time within the
week, as well as the data about the health of the satellite. The second part of the
message, the ephemeris, provides the precise orbit for the satellite. The last part
of the message, the almanac, contains coarse orbit and status information for all
satellites in the network as well as data related to error correction.
 These signals are transmitted on two separate carrier frequencies 1.57542 GHz
(L1 signal) and 1.2276 GHz (L2 signal),that are common to all satellites in the
network.
 The satellite network uses a CDMA spread-spectrum technique where the low-
bitrate message data is encoded with a high-rate pseudorandom(PRN) sequence
that is different for each satellite.

9.  Since all of the satellite signals are modulated onto the same L1 carrier frequency,
there is a need to separate the signals after demodulation. Demodulating and
Decoding of GPS Satellite Signals takes place using the Gold codes.
 This is done by assigning each satellite a unique binary sequence known as a Gold
code. The signals are decoded, after demodulation, using addition of the Gold codes
corresponding to the satellites monitored by the receiver.

10.  Using messages received from a minimum of four visible satellites, a GPS
receiver is able to determine the times sent and then the satellite positions.
 The x, y, and z components of position, and the time sent, are designated
as where the subscript i is the satellite number and has the value 1, 2, 3, or
4.
 The GPS receiver can compute the transit time of the message as (tr-ti)
.The distance traveled or pseudorange, can be computed as (tr-ti)*c .
 A satellite's position and pseudorange define a sphere, centered on the
satellite with radius equal to the pseudorange.
 The position of the receiver is somewhere on the surface of this sphere.
 Thus with four satellites, the indicated position of the GPS receiver is at or
near the intersection of the surfaces of four spheres.

12.  This method calculates the angle of
arrival of signal receiving at the BS.
 When a mobile user switches the
system ON it receives the signal from
different base stations, may be 3 or 4
or more. The angle of arrival method
requires two or more base station for
the determination.
 It measures the direction of signal
falling on the base station and
measures the angle of incidence with
respect to a normal and determines
the position of the system.

13.  The TOA method calculates the distance
of a mobile telephone and a BS based
on the TOA of a signal transmitted from
the mobile telephone at the BS.
 It is assumed that the mobile telephone
is located at the intersection point of
three circles having the radius of the
distances between the BSs and the
mobile telephone.
 The distance is calculated by the
following equation,
Ri = C τi = sqrt ( (xi – X ) 2 + (yi – Y) 2 ) where,
C – Propagation speed of electromagnetic
wave,
τi – propagation of time from the mobile
telephone to ith base station,
Xi, yi -- location of ith base station,
X, Y – mobile position

15.  The location data processor draws two circles C1 and C2 with their respective
centers set at BSs T1 and T2 based on the TOAs of a signal transmitted from
the corresponding mobile telephone M1 or M2 to the two BSs T1 and T2
located near the mobile telephone M1 or M2. The two circles C1 and C2 define
a common chord L1.
 Therefore, we use location tracking curves TR1 and TR2 connecting the same
two intersection points P1 and P2 of the two circles C1 and C2, instead of the
common chord L1.
 The two curves TR1 and TR2 have their middle points intersecting the line ST,
which connects the positions of the two BSs T1 and T2 and the parts of two
circles C1 and C2 drawn to connect the two intersection points P1 and P2.
 This method prevents the location error caused by the multi-path fading or the
NLOS path characteristics.

16.  When curves are selected for all selected
BS pairs, the location data processor
obtains the intersection points among the
selected curves.
 As the selected curves do not intersect at
one point due to the multi-path fading or the
NLOS effects, the midpoint of these
intersection points is determined as the
location of the mobile telephone.
 The location data processor represents the
intersection points in the latitude and the
longitude coordinates and transmits the
position coordinates to the network and the
mobile telephone.

17.  Our proposal is advantageous in that the location of a mobile telephone can be
accurately tracked even in the multi-path fading and the NLOS environment, by
using more accurate tracking curves connecting the intersection points among
circles.
 We have described about accurate positioning of mobile telephones, which can
be used for several applications.
 The important considerations to be undertaken while selecting a location based
technology are location accuracy, implementation cost, reliability, increasing
functionality.