2 KEY FEATURES .......................................................................................................................................6
The cellular systems are made up of numerous transmitting and receiving sites, whose
individual coverage areas partially overlap. The concept of frequency re-use, same
frequency is used by several sites, allows a high traffic density in a wide area. Due to the
limited transmission range of the terminals, cellular systems are based on a large number of
base stations on the infrastructure side, scattered over the area to cover, with each covering
a fairly small geographical zone called cell. Cells are often represented by hexagons (see
figure 1.1.).
FIGURE 1.1 CELLULAR COVERAGE REPRESENTATION.
GSM Network Architecture.
GSM network can be broadly divided into three broad parts, namely:
1. Mobile Station(MS) carried by the subscriber,
2. Base Station Sub-system (BSS) which controls the radio link with the mobile station.
3. Mobile Switching Centre (MSC) which performs the switching of calls between the mobile
users, and between mobile and fixed network users.
Each mobile station is given a unique identity. As soon as the mobile phone is turned on, it
registers with the network and is authenticated; as such the network could always find the mobile
phone.
Larger amount of data is being exchanged to and from the following functional blocks in the MSC:
Visitor Location Register, VLR
Stores information about mobile subscribers that enter it coverage area, which is associated with
the geographical area where the mobile is currently roaming. When there is an incoming call for
the mobile, the HLR is interrogated about the present address of the VLR.
Home Location Register, HLR
A database that contains all data concerning the subscription of the mobile subscriber, i.e. their
access capabilities, subscribed services, and supplementary services. It also contains information
about the VLR that is handling the mobile station currently. When the mobile changes location,
the HLR is updated accordingly. It also provides the MSC with information about the MSC area
where the mobile is actually located to allow incoming calls to be routed immediately to the called
party.
Authentication Center, AUC
Stored information that is necessary to protect communication through the air interface against
any intrusions. The legitimacy of the subscriber is established through authentication and
ciphering, which protects the user information against unwanted disclosure.
Equipment Identity Register, EIR
An option the network operator can use to enforce security. With this feature the network can
identify defective or stolen mobile that may not be used in the network.
SIM is a smart card, which has a computer, and memory chip that is permanently installed in the
mobile equipment. It comes in either the size of a credit card or smaller version known as the
plug-in SIM.
The subscriber information, which includes a unique number called the International Mobile
Subscriber Identity (IMSI), is stored in the SIM card. SIM card identifies the subscriber to the
network.
To protect the SIM card from improper use, a security feature, a four digits personal identification
number (PIN), is built in. The PIN is stored in the SIM card and can be changed by the subscriber.
PIN2 is required for additional functions available with a special SIM card (Consult the operator for
more information about the PIN 2).
A code (PUK) is provided for unlocking the SIM card if the SIM card is blocked.
This is a new GSM feature that has been integrated into the GSM standards in Release 96, with
further enhancements added as part of the Release 97 feature set. This feature came about
because of a desire by Network Operators to offer differentiated services, without the need for the
Mobile Manufacturers having to build different variant for different customers. The unique service
offered by the Operator is placed as an application on the SIM and that could work on any mobile
that supports the Toolkit feature.
There is a distinct set of commands between the mobile and the SIM specifically for the Toolkit
that allows the SIM application and the mobile to communicate independently of the GSM
communication between the SIM and the mobile. Henceforth, the SIM Application Toolkit and
GSM functionality on the SIM are separated logically. The Toolkit can interact directly with the
mobile itself and adding itself to the mobile menu.
“Proactive SIM” is a mechanism whereby the SIM can initiate actions to be taken by the mobile.
These actions include:
• Send short message
• Set up a voice call to a number held by the SIM
• Send a Supplementary Service (SS) control or Unstructured Supplementary Services
Data (USSD) string
• Play a tone in the mobile’s ear piece or ringer
• Initiate a dialogue with the user
• Provide local information from the mobile to the SIM
• Data download to the SIM from network
SIM Applications Toolkit (SAT) allows the flexibility to update the SIM, to change the services and
download new services over the air. In the SAT specification, the short message service is a key
mechanism for personalizing the SIM in each user’s GSM phone. It is designed as a client-server
application. The X6 supports the SAT specification.
Extended GSM 900, E-GSM
This is a new standard that allows Network Operators to increase their capacity through an
extended frequency. The frequency range of E-GSM is as follows:
• Mobile Transmit: 880,2 - 914,8 MHz
• Mobile Receive: 925,2 - 959,8 MHz
Xelibri X6 is a GSM Phase 2 / Phase 2+ Dualband E-GSM 900 / GSM 1800 mobile phone.
The following is the link to the support information regarding the mobile phone.
The only available accessory is the standard charger:
Is designed by Siemens according to specification "charger for L55 series - version 03" Spec Ref/
DIS 10506; Date : 17/04/02 from Siemens AG ICM MP PO2 KLF32.
The Standard Charger is only available in 3 country versions : UK, EU, China.