This document is a seminar report on GSM architecture submitted by a student, G. Koteswararao, to partially fulfill requirements for a Bachelor of Technology degree in Electronics and Communication Engineering. It includes an abstract, introduction, and sections on the history of GSM technology, GSM system architecture including mobile stations, base station subsystems, network and switching subsystems, and operating subsystems. It also discusses mobility management, traffic and control channels, cell selection, authentication, and call control in GSM networks.

1. Dept., of ECE, LBRCE 1
A
SEMINAR REPORT
ON
GSM ARCHITECTURE
Submitted in partial fulfilment of
The requirements for the award of the degree
Of
BACHELOR OF TECHNOLOGY
IN
ELECTRONICS & COMMUNICATION ENGINEERING
By
G.KOTESWARARAO
(15765A0415)
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
LAKIREDDY BALI REDDY COLLEGE OF ENGINEERING
(Autonomous &Affiliated to JNTUK, Kakinada & Approved by AICTE, New Delhi)
(Accredited by NBA of AICTE & Certified by ISO 9001:2000)
L B REDDY NAGAR, MYLAVARAM-521 230
Krishna District, Andhra Pradesh 2014-2015

2. Dept., of ECE, LBRCE 2
LAKIREDDY BALI REDDY COLLEGE OF ENGINEERING
(Autonomous &Affiliated to JNTUK, Kakinada & Approved by AICTE, New Delhi)
(Accredited by NBA of AICTE & Certified by ISO 9001:2000)
L B REDDY NAGAR, MYLAVARAM-521 230
Krishna District, Andhra Pradesh
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
CERTIFICATE
This is certify that G.KOTESWARARAO (15765A0415), student of B. tech, III semester (ELECTRONICS
AND COMMUNICATION ENGINEERING) have successfully completed his Seminar titled “GSM
ARCHITECTURE” at Lakireddy Bali Reddy College of Engineering during the academic year 2016-
2017. This seminar Report is submitted in partial fulfilment for the award of degree B. Tech (Electronics
And Communication Engineering).
Date:
Place:
SEMINAR CO-ORDINATOR HEAD OF THE DEPARTMENT
Prof. B. RAMESH REDDY

3. Dept., of ECE, LBRCE 3
ACKNOWLEDGEMENTS
First and foremost we sincerely thank our institution Lakireddy Bali Reddy College of
Engineering for giving this opportunity for fulfilling our dreams of becoming engineers. We express
our special gratitude to our Director Dr. E.V.Prasad who made this endeavour possible.
We have the immense pleasure in expressing our thanks and deep sense of gratitude of Prof B.
Ramesh Reddy, Head of the Department of Electronics & Communication Engineering for
extending necessary facilities for the completion of project.
We are highly thankful to our seminar coordinators Mr. Ch. V. Naga Bhaskar, Asst. Prof of
ECE Smt.K. Lakshmi., and Asst. Prof of ECE for providing the knowledge to deal with the problem
at every phase of our seminar in a systematic manner.
We would like to extend our deepest gratitude to the support rendering by the Teaching and
Non-Teaching staff of Electronics and Communication Engineering department during the course of
this work. Finally we thank each and every one who indirectly contributed his or her help to complete
this project.
G.KOTESWARARAO
(15765A0415)

4. Dept., of ECE, LBRCE 4
GSM ARCHITECTURE

5. Dept., of ECE, LBRCE 5
TOPICS
ABSTRACT
1.INTRODUCTION
2.History of GSM Technology
3.SYSTEM ARCHITECTURE
4.MOBILITY MANAGEMENT
5.ADVANTAGES & DISADVANTAGES
6.APPLICATIONS & FUTURE SCOPE
7.CONCLUSION

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FIGURES & TABULATIONS
FIGURES:
FIGURE 1: SYSTEM ARCHITECTURE……………………………………………..11
FIGURE 2:STRUCTURE OF GSM NETWORK……………………………………..14

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Abstract
GSM, the Global System for Mobile communications, is a digital cellular communications system which has
rapidly gained acceptance and market share worldwide, although it was initially developed in a European
context. In addition to digital transmission, GSM incorporates many advanced services and features,
including ISDN compatibility and worldwide roaming in other GSM networks. The advanced services and
architecture of GSM have made it a model for future third-generation cellular systems, such as UMTS. This
paper will give an overview of the services offered by GSM, the system architecture, the radio transmission
structure, and the signaling functional architecture.
Services provided by GSM
GSM was designed having interoperability with ISDN in mind, and the services provided by GSM are a
subset of the standard ISDN services. Speech is the most basic, and most important, teleservice provided by
GSM.
In addition, various data services are supported, with user bit rates up to 9600 bps. Specially equipped GSM
terminals can connect with PSTN, ISDN, Packet Switched and Circuit Switched Public Data Networks,
through several possible methods, using synchronous or asynchronous transmission. Also supported are
Group 3 facsimile service, videotext, and teletex. Other GSM services include a cell broadcast service, where
messages such as traffic reports, are broadcast to users in particular cells

8. Dept., of ECE, LBRCE 8
1 INTRODUCTION
The development of GSM started in 1982 when a study group „Group
Special Mobile‟ was formed during Conference of European Posts and
Telegraphs (CEPT) this group was to develop a Pan-European public cellular system in the 900 MHz
range. Some of the basic criteria for their proposed system were:
Good subjective speech quality
ISDN compatibility
Spectral efficiency
Support for international roaming
Support for range of new services and facilities
In 1989, GSM responsibility was transferred to European Telecommunication Standards Institute (ETSI)
and commercial service was started in mid 1991. Although GSM was standardized in Europe, now it is
operational in other continents also. The acronym GSM now aptly stands for Global System for Mobile
Communication.
CELLULAR CONCEPT
Cellular radio was devised in order to make better use of limited resource of Radio Spectrum. Each Megahertz
of spectrum will only support a comparatively a small number of simultaneous conversations and the same
frequency must be reused many times in order to meet the capacity needed for national or regional service.
Cellular radio achieves this by creating a honeycomb of cells over the region and assigning frequencies

9. Dept., of ECE, LBRCE 9
2.History of GSM Technology
Europeans quickly realized the disadvantages of each European country operating on their mobile network. It
prevents cell phone use from country to country within Europe. With the emerging European Union and high
travel volume between countries in Europe this was seen as a problem. Rectifying the situation the
Conference of European Posts and Telegraphs (CEPT) assembled a research group with intentions of
researching the mobile phone system in Europe. This group was called Group Special Mobile (GSM).
For the next ten years the GSM group outlined standards, researched technology and designed a way to
implement a pan-European mobile phone network. In 1989 work done by the GSM group was transferred to
the European Telecommunication Standards Institute (ETSI). The name GSM was transposed to name the
type of service invented. The acronym GSM had been changed from Group Special Mobile to Global
Systems Mobile Telecommunications.
By April of 1991 commercial service of the GSM network had begun. Just a year and half later in 1993 there
were already 36 GSM networks in over 22 countries. Several other countries were on the rise to adopt this
new mobile phone network and participate in what was becoming a worldwide standard. At the same time,
GSM also became widely used in the Middle East, South Africa and Australia.
There are five major GSM frequencies that have become standard worldwide. They include GSM-900,
GSM-1800, GSM-850, GSM-1900 and GSM-400.
GSM-900 and GSM-1800
GSM-900 and GSM-1800 are standards used mostly worldwide. It is the frequency European phones operate
on as well as most of Asia and Australia.
GSM-850 and GSM-1900
GSM-850 and GSM-1900 are primarily United States frequencies. They are also the standard for Canada
GSM service and countries in Latin and South America. Most of the Cingular network operates on GSM 850,
while much of T-Mobile operates at GSM-1900. T-Mobile however, has roaming agreements with Cingular.
Meaning in the case of no service at GSM-1900, the phone will switch to GSM-850 and operate on
Cingular’s network.
GSM-400
GSM-400 is the least popular of the bunch and is rarely used. It is an older frequency that was used in Russia
and Europe before GSM-900 and GSM-1800 became available. There is not many networks currently
operating at this frequency.

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3 SYSTEM ARCHITECTURE
The functional architecture of a GSM system can be broadly classified into
Mobile Station (MS)
Base Station Subsystem (BSS)
Network and Switching Subsystem (NSS)
OperationSubsystem (OSS)
The MS and the BSS communicate via the Um interface or radio link. The BSS communicates
with Mobile Service Switching Center across the A interface.
MOBILE STATION
This may be a standalone piece of equipment for certain services or support the connection of
external terminals. The MS consists of the Mobile Equipment (ME) and a Subscriber Identity
Module (SIM).
The ME is uniquely identified by the International Mobile Equipment Identity (IMEI), but it need
not be personally assigned to one subscriber, The SIM which is a smart card provides personal
mobility and the user can access the subscriber services. The subscriber can operate on any terminal
just by inserting the SIM card in that GSM terminal. SIM card contains the International Mobile
Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key for
authentication and other security information’s. SIM card may be protectedagainst unauthorized use
by a password.
BASE STATIONSUBSYSTEM
The BSS is composed of three parts, Base Transceiver Station (BTS) and U3ase Station
Controller (BSC). These two communicate across the standardized Abius interface. The third part
is Transcoder and Rate Adaptation Unit (TRAU).

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Base Transceiver Station:
This provides the GSM radio coverage within a cell. It comprises of radio transmitting and
receiving equipment and associated signal processing units. This complements the radio features
of ME.
Base Station Controller
This manages the radio resourcesfor one or more BTS‟s. It handles radio channel set-up, Handovers
and frequency hopping. Handovers between BTS‟s belonging to different BSC‟s however can
involve MSC‟s but are still managed by the original serving BSC. It controls the transmission of
information about Local Area Codes (LAC), signaling channel configuration and information’s
about neighboring cells.
FIGURE 1:SYSTEM ARCHITECTURE

12. Dept., of ECE, LBRCE 12
Transcoder and Rate Adaptation Unit.
This is responsible for transcoding between GSM encoded speech at I 3KPS and fixed
network speech at 64KPS. Similarly it performs rate adaptation of GSM data services. Although it
is a part of BSS, it is located at MSC Sites. This is to benefit from the lower rate coding and
consequent saving in transmission costs.
NETWORKAND SWITCHING SUBSYSTEM
NSS in GSM uses an Intelligent Network (The central component of NSS is the Mobile Service
Switching Center (MSC). It is supported by Interworking functions (JWF), Home Location Register
(HLR), Visitor Location Register (VLR), Gateway MSC (GMSC) and Signal Transfer Point (STP).
Mobile Service Switching Center
It acts like a switching node and additionally provides all the functionality needed to handle a mobile
subscriber such as registration, authentication, location updating. Handovers and call routing to a
roaming subscribe. These functions are provided in conjunction with several functional entities. An
MSC controls several BSC‟s.
Inter Working Function, (IWF)
A gateway for MSC to interface with external networks for communications with users outside
GSM. The role of IWF depends upon the type of user data and the network to which it interfaces.
Home Location Register (HLR,)
It consists of a computer without switching capabilities. It is a database, which contains subscriber
information related to the subscriber’s current locations but not the actual location. HLR has two
divisions Authentication Center (AuC) and Equipment Identity Register (EIR). The AuC manages
the security data for subscriber authentication. The EIR database carrying information about certain
ME‟s. The security procedure is discussed later.
Visitor Location Register VLR,).

13. Dept., of ECE, LBRCE 13
It links to one or more MSC‟s, temporarily storing subscription data currently served by its
corresponding MSC. VLR holds more current subscriber location than l—ILR. Although VLR is
an independent unit, it is always implemented together with the MSC.
Gateway MSC GMSC)
In order to set-up a requested call, the call is initially routed to a GMSC which finds the correct
HLR.GMSC has an interface with external network for gatewaying and the network operates the full
signaling system 7 (SS7) between NSS Machines.
Signaling Transfer Point
It acts as a standalone node to optimize the cost of the signaling transport among MSC/VLR,
GMSC and HLR>
OPERATING SUBSYSTEM
There are three area of OSS
Network operation and maintenance function. •
Subscription management including charging and billing.
Mobile Equipment and Management.
LAYER MODELLING
Transmission
Radio resource management
Mobility management
Communicationmanagement

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FIG2:
ASPECTS
The International Telecommunication Union (ITU) which manages Allocation of radio
spectrum has allocated the bands 890-915MHz for the uplink (MS To BS) and 960MHz for the
downlink (BS To MS) for mobile networks.
MULTIPLE ACCESS AND CHANNEL STRUCTURE
Due to the scarcityof radio spectrum, a method must be devised to divide bandwidth among
as many users as possible. GSM uses a combination of FDMA TDMA. FDMA part involves the
division by frequency of the 25M1-lz bandwidth into carrier frequencies of 200KHz bandwidth.
One or more carrier frequencies is then divided in time using TDMA scheme.

15. Dept., of ECE, LBRCE 15
TRAFFIC CHANNELS
This is also called physical channel. This is used to carry speech and
data traffic: They are of Three kinds
TCH/F (full rate): Transmits the speech code of 13 KBPS or Three data mode 12,6 and 3.6
1KBPS.
TCIH/H(half rate):Transmits the speech code of 7 1KBPS or Two
data modes 6 3.6 1KBPS
TCI-118( 1/8th
rate): Used for low rate signaling channels, Common channels and channels.
They are also called Stand Alone Dedicated Control Channel(SDCCH)
CELL SELECTION
Using the best cell from an MS depends on three factors
The level of signal received by the MS.
The maximum transmission power of the MS.
Two parameters P1 and P2 specified by the cell
C1 = A-max (B, 0)
A = received level average-P 1
B = P2-Max RF power of the MS.
P1 = A value between —110 and —48dBm
P2 = A value between 13 and 43dBm

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4 MOBILITY MANAGEMENT
This layer handles the functions that arise from the mobility of the subscribers as well as the
authentication and security aspects.
LOCATION UPDATING
The mobile phone receives constantly information send by the network. This information includes
identification of the area where the mobile is currently located. In order to keep track of its location,
the mobile stores the ID of the area in which it is currently registered. Every time the network
broadcasts the ID of the area, the mobile compares this, information to the area ID stored in its
memory. When the two ID‟s are no longer the same, the mobile sends the network a request, i.e.
Registration inquiry to the area it has entered. The network receives the request and registers the
mobile in the new area, a new VLR. Simultaneously, a subscriber HLR is informed about the new
location and the data of the subscriber is cleared from the previous VLR.
AUTHENTICATION AND SECURITY
Authentication involves two functional entities: -SIM and AuC.Each subscriber is given a secretkey,
one copy of which is stored in SIM card and the other in AuC. During Authentication, the AUC, a
128 bit random number RANI) thatxs is send o lie Mobile. Both mobile and the AuC then uses the
RAND in conjunction with the subscribers secret key and a ciphering algorithm call lcd A3, to
generate a 32 bit long signal response (SRES) that is send back to AuC.lf both numbers match the
subscriber is authenticated.
COMMUNICATION MANAGEMENT
This layer is responsible for call control, supplementary service management and short message
service management.
CALL CONTROL
Call control functions set up calls, maintain calls and release calls.

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CALL ROUTING
The directory number dialed to reach a mobile subscriber is called the mobile subscriber
ISDN (MSISDN) which is defined by E.164 numbering plan. This number includes country code
and national destination code, which identifies the subscriber’s operator. The first few digits of the
remaining subscriber number may identify the subscriber’s HLR.
An incoming mobile terminating call is directed to the GMSC. GMSC contains table linking
MSISDN to their corresponding HLR. The GMSC queries the called subscriber’s HLR for a
Mobile Station Roaming
Number (MSRN). The HLR typically stores only the SS7 address of the subscriber’s current VLR
and so HLR queries the current VLR, which will temporarily allocate an MSRN from its pool for
the call. This MSRN is returned to the HLR and back to GMSE, which can then route the call to
the new MSC. At the new MSC the IMISI corresponding to the MSRN is looked up and the mobile
is paged in its current location area. SUPPLEMENTARY
SERVICE MANAGEMENT
GSM provides services like call waiting, call forwarding and automatic canceling. SSM is a
point to point management service.
SHORT MESSAGE SERVICE
SMS allows alphanumeric text messages to be sent to and from a mobile phone via a service
center using SACCH. The size of the single short message is limited to 160 characters. The
received short messages are normally stored in SIM.

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STRENGTHS OF GSM
Compatibility with ISDN using rate adaptation box.
Use of SIM cards.
Control of transmission power.
Frequency hopping.
Discontinuous transmission.
Mobile assisted handover.
GSM Services
 GSM was designed to do 3 things:
– 1. Bearer data services: Faxes, text messages, web pages.
 Basic GSM had a basic data rate that is limited to 9.6 kbps
– Extended by GMRS and EDGE to around 384 Kbps
– 2. Voice traffic
 But, at a lower quality than analog.
– 3. Other features:
 Call forwarding, caller id, etc.…
– Meaning, we need to connect to the SS7 network
–

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5.ADVANTAGES & DISADVANTAGES
Advantages
• There are numerous handsets and service providers available in the market. Hence the buyers can choose
from a variety of options.
• They come with a variety of plans with cheaper call rates, free messaging facility, and limited free calls and
so on.
• The quality of calling in GSM is better and also better secured than CDMA.
• A number of value-added services such as GPRS are making GSM a perfect choice.
• The consumption of power is less in GSM mobiles.
• With the tri-band GSM, one can use the phone anywhere around the world.
Disadvantages
• The per-unit charge on roaming calls is higher in GSM than in CDMA.
• Calls made through GSM mobiles can be tampered.
• If the SIM gets lost, one can lose all the data, if the same is not saved in the phone.

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21. Dept., of ECE, LBRCE 21
FUTURE SCOPE
The market for mobiles communications has grown up explosively since the introduction of 2nd generation
of digital system 3rd generation is the technology for the future the need for higher speed & capacity, much
more services like multimedia internet is growing gsm has to upgrade for 3g the most imp steps involved in
the evolution of gsm to increase the data

22. Dept., of ECE, LBRCE 22
CONCLUSION
This report has given a overview of GSM is the first approach at the true Personal Communication
„Systems (PCS). The SIM card is a novel approach that implements the personal and terminal
mobility. Together with international roaming and support for various services GSM comes close to
fulfilling the requirements of PCS. GSM is being used for the next generation of mobile
telecommunication technology the Universal Mobile Telecommunication Systems (UMTS). The
GSM network functions system architecture and protocols are spread over a large number of GSM
documents.

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REFERENCES
William C.Y.Lee, “Mobile Cellular Telecommunications” 2nd
Edition, Mc Graw Hill
Publication
R.C.V.Macario, “Modern Personal Radio Systems” IEEE Telecommunication Series
John Scourious, “Overview of USM Cellular Systems” University of
Waterloo
Electronics and Communication Engineering Journal Jan/Feb 1989 Vol.1, No: 1, pp7-13
IEEE Communication Magazine April 1993 Vol.3 1, No: 4,
pp92-100