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1.3
Global Positioning System (GPS) Section
The U.S. Department of Defense (DoD) operates a constellation of 24-satellites, employed for
location and/or navigational purposes, on earth. These satellite vehicles (SV) operate in circular
orbits, round the earth every 12 hours, at an altitude of 20,200 km. The SVs transmit earth-bound
radio signals at a 1575.42 MHz fixed carrier frequency—an L1 band for non-military applications.
Since the SVs utilize one carrier frequency, by employing a Spread Spectrum modulation technique,
each SV can be uniquely identified from an assigned Pseudo-random Noise (PN) Code.
To determine a location on earth, a receiver must be built that can receive the simultaneous signals from
the satellites that are in view of the receiver and use that information to calculate the location of the
receiver. The receiver must pick up the signals from 4 satellites. Once the 4 satellites are located, the
receiver measures the time it took for the satellite signals to arrive. From this timing information, the
distance between the receiver and each satellite can be calculated. The four satellites' ephemeris data
provide the satellite's X, Y, and Z positions. The range, R, is the receiver measurement made by
calculating the time it took for the signal to reach the receiver. The user's position, (Ux, Uy, Uz), and the
clock bias, Cb, is then calculated.
To use the GPS, a receiver that can receive the spread-spectrum signals must be built. The detected
signals are then converted from RF signals into appropriate digital input formats. These digital inputs are
processed and converted into position information. Once the position coordinates are determined, they
are communicated to the handset microprocessor and displayed on the screen or transmitted to the base
station as required.
1.4
SIM Cards
The i265 unit is designed to work with a mini Subscriber Identity Module (SIM). The SIM card
contains all of the personal data required to access iDEN services. Data held by the SIM card
includes:
Temporary Mobile Subscriber Identity
•
Services to which the user subscribes
•
PIN and unblocking codes
•
Call barring codes
•
The SIM card is also capable of storing phone numbers and names.
Available SIM cards for the i265 are 64 kB and prepaid.
1.4.1
Removing and Inserting a SIM Card
NOTE: When a SIM card is defective and must be replaced with a new one, the following
information will be erased:
The recent calls list
•
Call forwarding settings
•
Net alerts
•
MMS messages
•
Options set using the MMS Setup menu
•
Information stored in Memo
•
3 most recent GPS Enabled locations
•
68P80400P84-O
OVERVIEW: Global Positioning System (GPS) Section
1-5
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Table of Contents
Troubleshooting
