Sim Cards - Motorola iDEN i930 Field Service Manual

OVERVIEW: SIM Cards
The radio telephones themselves are capable of operation on any channel in the system. This
enables them to operate in any cell. Due to the low power requirements for communications
between radio telephones in a particular cell and the cell site, operating channels may be repeated in
cells which are outside the coverage area of each other.
The implementation of frequency re-use increases the call handling capability of the system without
increasing the number of available channels. When re-using identical frequencies in a small area,
co-channel interference can be a problem.
The GSM system can tolerate higher levels of co-channel interference than analog systems by
incorporating digital modulation, forward error correction and equalization. This means that cells
using identical frequencies can be physically closer than similar cells in analog systems. Therefore,
the advantage of frequency re-use can be further enhanced in a GSM system, enabling greater traffic
handling in high-use areas.
Due to TDMA, several calls can share the same carrier. The carrier is divided into a continuous
stream of TDMA frames, each of which is split into eight time slots. When a connection is required,
the system allocates the subscriber a dedicated time slot within each TDMA frame. User data
(speech/data) for transmission is digitized and sectioned into blocks. The user data blocks are sent
as information bursts in the allocated time slot of each TDMA frame. The data blocks are modulated
onto the carrier via Gaussian Minimum Shift Keying (GMSK), a very efficient method of phase
modulation.
Each time an information burst is transmitted, it can be transmitted on a different frequency. This
process is known as frequency hopping. Frequency hopping reduces the effects of fading, and
enhances the security and confidentiality of the link. A GSM radio telephone is only required to
transmit for one burst in each frame, not continually. This enables the unit to be more power
efficient.
Each unit must be able to move from one cell to another with minimal inconvenience to the user.
The unit itself carries out signal strength measurements on adjacent cells, and the quality of the
traffic channel is measured by both the unit and the base station. The handover criteria can thus be
much more accurately determined, and the handover made before the channel quality deteriorates to
a level that the subscriber can notice.
When an i930 unit is well within a cell, the signal strength measured will be high. As the radio
telephone moves toward the edge of the cell, the signal strength and quality measurement decreases.
Signal information provides an indication of the subscriber's distance from the base station. As the
i930 unit moves from cell to cell, its control is handed from one base station to another in the new
cell.
The change is handled by the i930 unit and the base station, and is completely transparent to the
user.
1.5

SIM Cards

This 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:
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68P80401P03-O