GSM networks consist of thee major systems: SS,
which is known to be The Switching System; BSS,
which is also called The Base Station; and the
Operation and Support System for GSM networks.
Below all three systems are defined in details with
sub systems of each system.
The Switching System
The Switching system is very operative system in
which many crucial operations are conducted, SS
systems holds five databases with in it which
performs different functions. If we talk about major
tasks of SS system it performs call processing and
subscriber related functions. These five databases
from SS systems are HLR, MSC, VLR, AUC and EIR.
Let’s study each database in detail and learn what
functions this little systems performs.
HLR- Home Location Register:
HLR is database, which holds very important
information of subscribers. It is mostly known for
storing and managing information of subscribers. It
contains subscriber service profile, status of
activities, information about locations and
permanent data of all sorts. When new connections
are purchased, these subscribers are registered in
HLR of mobile phone companies.
MSC- Mobile Services Switching Center:
MSC is also important part of SS, it handles
technical end of telephony.It is build to perform
switching functionality of the entire system. It’s
most important task is to control the calls to and
from other telephones, which means it controls
calls from same networks and calls from other
networks. Toll ticketing, common channel
signaling, network interfacing etc are other tasks
which MSC is responsible for.
VLR- Visitor Location Register:
VLR performs very dynamic tasks; it is database
which stores temporary data regarding subscribers
which is needed by Mobile Services Switching
Center-MSC VLR is directly connected to MSC,
when subscribe moves to different MSC location,
Visitor location register – VLR integrates to MSC of
current location and requests the data about
subscriber or Mobile station ( MS ) from the Home
Location Register –HLR. When subscriber makes a
call the Visitor location register-VLR will have
required information for making call already and it
will not required to connect to Home Register
Location – HRL again.
AUC- Authentication Center:
AUC is small unit which handles the security end
of the system. Its major task is to authenticate and
encrypt those parameters which verify user’s
identification and hence enables the confidentiality
of each call made by subscriber. Authentication
center – AUC makes sure mobile operators are
safe from different frauds most likely to happen
when hackers are looking for even smallest loop
wholes in systems.
EIR – Equipment Identity Register:
EIR is another important database which holds
crucial information regarding mobile equipments.
EIR helps in restricting for calls been stolen,
malfunctioning of any MS, or unauthorized access.
AUC – Authentication center and EIR- Equipment
Identity registers are either Stand-alone nodes or
some times work together as combined AUC/EIR
nodes for optimum performance.
The Base Station System (BSS)
The base station system have very important role
in mobile communication. BSS are basically out
door units which consist of iron rods and are
usually of high length. BSS are responsible for
connecting subscribers (MS) to mobile
networks.All the communication is made in Radio
transmission.The Base station System is further
divided in two systems. These two systems, they
are BSC, and BTS. Let’s study these two systems
BTS – The Base Transceiver Station:
Subscriber, MS (Mobile Station) or mobile phone
connects to mobile network through BTS; it
handles communication using radio transmission
with mobile station. As name suggests, Base
transceiver Station is the radio equipment which
receive and transmit voice data at the same time.
BSC control group of BTSs.
BSC – The Base Station Controller:
The Base Station normally controls many cells, it
registers subscribers, responsible for MS
handovers etc. It creates physical link between
subscriber (MS) and BTS , then manage and
controls functions of it. It performs the function of
high quality switch by handover over the MS to
next BSC when MS goes out of the current range
of BTS, it helps in connecting to next in range BTS
to keep the connection alive within the network. It
also performs functions like cell configuration data,
control radio frequency in BTS. Data moves to
MSC-Mobile switching center after BSC done
processing it. MSC is switching center which acts
as bridge between different mobile networks.
Architecture and Working of GSM Networks
The Operation and Support System (OSS)
OMC- Operations and maintenance center is
designed to connect to equipment of MSC- Mobile
Switching Center and BSC-Base Station Controller.
The implementation of OMC is called OSS-The
Operations and Support System.OSS helps in
mobile networks to monitor and control the
complex systems.The basic reason for developing
operation and support system is to provide
customers a cost effective support and solutions. It
helps in managing, centralizing, local and regional
operational activities required for GMS networks.
Maintaining mobile network organization, provide
overview of network, support and maintenance
activities are other important aspects of Operation
and Support System
The Penalty for Ignorance is Lack