3. GSM History
1981 Analogue cellular introduced
Franco-German study of digital pan-
European cellular system
1987 MoU signed by over 18
countries
1989 GSM was moved into the ETSI
organization
GSM name changed to Global
System for Mobile communications.
1990 DCS1800 (edited GSM900)
specification
developed
4. Description
In 1981 analogue cellular was introduced and at about the same
time there was a joint Franco-German study looking at digital
cellular technology and the possibility of making a pan-
European
system.
In 1982 a special working committee, Groupe Spécial Mobile
(GSM), was formed within the CEPT to look at and continue
the
Franco-German study.
5. In 1989 GSM was moved into the ETSI (European
Telecommunications Standards Institute) organization.
Once
under the control of ETSI, the GSM system had it's name
changed to Global System for Mobile communications.
The
committees working on the system changed from GSM
to SMG
(Special Mobile Group). These changes avoided
confusion
between the system name (GSM), and the people
working on the
6. GSM (Global System for Mobile
Communications
Originally Groupe Spécial Mobile), is a
standard developed by the European
Telecommunications Standards Institute (ETSI)
to describe protocols for second generation (2G)
digital cellular networks used by mobile
phones.
It is the default global standard for mobile
communications with over 90% market share,
and is available in over 219 countries and
territories
9. FULL FORMS USED IN DIAGRAM
SIM: Subscriber identify module.
ME: Mobile equipment.
BTS: Base transceiver station.
BSC: Base station controller.
HLR: Home location register.
VLR: Visitor location register.
MSC: Mobile services switching center.
EIR: Equipment identity register.
AuC: Authentication Center.
UM: Represents the radio link.
Abis: Represents the interface between the
base stations and base station controllers.
"A": The interface between the base station
subsystem and the network subsystem.
PSTN and PSPDN: Public switched telephone network and
packet switched public data network.
11. Above is a table that shows the relative
frequency plans of the three GSM
networks: GSM900, DCS1800 and PCS1900.
The frequency range of the Uplink and
Downlink show how the two bands
are split into the two directions, rather than an
uplink being followed by a
downlink 200kHz later.
12. EWSD INTRODUCTION
EWSD ( Electronic Digital Switching
System/Electronic World Switch Digital) is one of
the most widely installed telephone exchange
systems in the world.
EWSD can work as a local or tandem switch or
combined local/tandem, and for landline or mobile
phones.
It is manufactured by Siemens AG, who claims
that EWSD switches perform switching for over
160 million subscriber lines in more than 100
countries.
Bosch built its first EWSD as a local exchange in
1986.
13. Hardware
Main subsystems are:
CP (Central Processor)
MB (Message Buffer)
CCNC (Common Channel Network Control)
LINE (Analog Line Group)
LTG (Line Trunk Group)
DLU (Digital Line Unit)
SN (Switching Network)
PA (ISDN Primary Access)
PDC (Primary Digital Carrier)
14. Software
The software of EWSD is called APS (Automatic
Program System). The APS is on a hard drive and includes
the operating system, developed by Siemens in
cooperation with Bosch.
It is predominantly written in the CHILL language.
Application software is switch specific and serves among
other things traffic management, path search, and call
charging.
Support software serves translating programs, binding
modules as well as administration of libraries for
generating data. Operating and data communication
software serve for co-operation of maintenance centers
and switching centers
15. Technical data
Number of access lines: to 250,000
Number of feeder lines: 240,000
Traffic connection: 25,200
Call attempts in busy hour: 10 million
Operating voltages: -48V -60V -90V
Rate zones: 127, for each zone of 6 tariffs
Tariff change-over at 15 minute intervals
Space requirement with 10,000 access lines: 35 square meters
