7/28/2019 Complete Project Report
1/92
CHAPTER --1
GSM INTRODUCTION
7/28/2019 Complete Project Report
2/92
GSM INTRODUCTION -----
1. Global System for Mobile communications (GSM: originally from Groupe Spcial
Mobile) is the most popular standard formobile phones in the world.
2. GSM is used by over 2billion people across more than 212 countries and territories.
3. GSM uses a variation of time division multiple access (TDMA) and is the most
widely used of the three digital wireless telephony technologies (TDMA, GSM, and
CDMA). 4. GSM digitizes and compresses data, then sends it down a channel with
two other streams of user data, each in its own time slot. It operates at either the 900
MHz or 1800 MHz frequency band.
4. GSM differs from its predecessors in that both signaling and speech channels are
digital call quality, and so is considered asecond generation (2G) mobile phone
system.
5. GSM standard is advantageous to both consumers (who benefit from the ability to
roam and switch carriers without switching phones) and also to network operators
(who can choose equipment from any of the many vendors implementing GSM).6. Newer version of GSM is Release97 which has packet data capabilities , by means
of GPRS (General Packet Radio Services ). Release 97 introduced higher speed
data transmission using Enhanced Data Rates for GSM Evolution (EDGE).
7. GSM, together with other technologies, is part of the evolution of wireless mobile
telemmunications that includes High-Speed Circuit-Switched Data (HCSD), GeneralPacket Radio System (GPRS), Enhanced Data GSM Environment (EDGE), and
Universal Mobile Telecommunications Service (UMTS).
http://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/1000000000_(number)http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214175,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213380,00.htmlhttp://searchtelecom.techtarget.com/sDefinition/0,,sid103_gci213842,00.htmlhttp://en.wikipedia.org/wiki/Digital_call_qualityhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolutionhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213689,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213691,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213688,00.htmlhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/1000000000_(number)http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214175,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213380,00.htmlhttp://searchtelecom.techtarget.com/sDefinition/0,,sid103_gci213842,00.htmlhttp://en.wikipedia.org/wiki/Digital_call_qualityhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolutionhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213689,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213691,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213688,00.html7/28/2019 Complete Project Report
3/92
GSM OBJECTIVES---------
In June 1982, the European Conference of Postal and Telecommunications
Administrations (CEPT), created the Groupe Spcial Mobile (GSM) to develop a
standard for a mobile telephone system that could be used across Europe.Developing
the GSM has mainly two objectives ----
1. Pan -European roaming ,which offers compatibility throughout the European
continent &
2. Interaction with the integrated service digital network (ISDN), which offers the
capability to extend the single subscriber-line system to a multiservice system
with various services which are currently offered only through diverse
telecommunications networks.
http://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrations7/28/2019 Complete Project Report
4/92
CHAPTER ---- 2
Comparison of mobile phone standards
7/28/2019 Complete Project Report
5/92
Comparison of mobile phone standards
Global System for Mobile Communications (AKA GSM, around 8085 % market share)
and IS-95 (AKA cdmaOne, around 1015 % market share
[1]
) are the two most prevalent
mobile communication technologies. Both technologies have to solve the same problem:
to divide the finite RF spectrum among multiple users.
TDMA (Time Division Multiple Accessunderlying technology used in GSM's 2G)
does it by chopping up the channel into sequential time slices. Each user of the channel
takes turns to transmit and receive signals. In reality, only one person is actually using the
channel at a specific moment. This is analogous to time-sharing on a large computer
server.
CDMA (Code Division Multiple Accessunderlying technology used in GSM's 3G and
IS-95's 2G) on the other hand, uses a special type ofdigital modulation called
spread spectrum which spreads the voice data over a very wide channel in pseudorandom
fashion. The receiver undoes the randomization to collect the bits together and produce
the sound.
For comparison, imagine a cocktail party, where couples are talking to each other in a
single room. The room represents the available bandwidth. In GSM, a speaker takes turns
http://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/IS-95http://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standards#_note-0http://en.wikipedia.org/wiki/RF_spectrumhttp://en.wikipedia.org/wiki/TDMAhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Time-sharinghttp://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/Digital_modulationhttp://en.wikipedia.org/wiki/Pseudorandom_numberhttp://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/IS-95http://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standards#_note-0http://en.wikipedia.org/wiki/RF_spectrumhttp://en.wikipedia.org/wiki/TDMAhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Time-sharinghttp://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/Digital_modulationhttp://en.wikipedia.org/wiki/Pseudorandom_number7/28/2019 Complete Project Report
6/92
talking to a listener. The speaker talks for a short time and then stops to let another pair
talk. There is never more than one speaker talking in the room, no one has to worry about
two conversations mixing. In CDMA, any speaker can talk at any time; however each
uses a different language. Each listener can only understand the language of their partner.
As more and more couples talk, the background noise (representing the noise floor) gets
louder, but because of the difference in languages, conversations do not mix.
Comparison table
Feature NMT GSM UMTS IS-95 CDMA2000
Technology FDMA TDMA W-CDMA CDMA CDMA
Generation 1G 2G 3G 2G 3G
Digital No Yes Yes Yes Yes
Age 1981 1991 2001 1995 2000
Worldwide market
share[2]0% 80% 4% 0.6% 12%
Roaming Scandinavia Worldwide,200+countries
Worldwide Limited Limited
Handset
interoperabilityNone SIM card SIM card None
RUIM (notcommonly
implemented)
Common
InterferenceNone
Interfereswith someelectronics,
such as
amplifiers
None None None
Signal
quality/coverage
area
Goodcoverage
due to lowfrequencies
Goodcoverage
indoors on850/900MHz.
Repeaterspossible. 35
Smaller cellsand lowerindoors
coverage dueto 2100 MHz
frequency
Unlimitedcell size,
lowtransmitter
powerpermits
large cells
Unlimitedcell size, lowtransmitter
powerpermits large
cells
http://en.wikipedia.org/wiki/NMThttp://en.wikipedia.org/wiki/GSMhttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/IS-95http://en.wikipedia.org/wiki/CDMA2000http://en.wikipedia.org/wiki/FDMAhttp://en.wikipedia.org/wiki/TDMAhttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/1Ghttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standards#_note-1http://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/Removable_User_Identity_Modulehttp://en.wikipedia.org/wiki/NMThttp://en.wikipedia.org/wiki/GSMhttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/IS-95http://en.wikipedia.org/wiki/CDMA2000http://en.wikipedia.org/wiki/FDMAhttp://en.wikipedia.org/wiki/TDMAhttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/1Ghttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standards#_note-1http://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/Removable_User_Identity_Module7/28/2019 Complete Project Report
7/92
km hardlimit.
Frequencyutilization/Call
density
Very lowdensity
0.2 MHz = 8timeslots.
Eachtimeslot canhold up to 2calls throughinterleaving.
5 MHz = 2Mbps. Eachcall uses 1.8-
12 kbit/sdepending on
chosenquality and
audiocomplexity.
?Comparable
to UMTS
?Comparable
to UMTS
Battery life
Low, due tohigh
transmitter
power (1watt)
Very gooddue to simple
protocol,good
coverage and
mature,power-efficientchipsets.
Lower due tohigh
demands ofWCDMApower
control andyoung
chipsets.
Lower dueto high
demands ofCDMApowercontrol.
Lower due tohigh demands
of CDMApower control
and youngchipsets.
Handoff Hard Hard Soft Soft Soft
Breathing No No Yes Yes Yes
Intellectual property ?
Concentratedamong a few
industryparticipants
Concentratedamong a few
industryparticipants
Qualcomm Qualcomm
http://en.wikipedia.org/wiki/Qualcommhttp://en.wikipedia.org/wiki/Qualcommhttp://en.wikipedia.org/wiki/Qualcommhttp://en.wikipedia.org/wiki/Qualcomm7/28/2019 Complete Project Report
8/92
CHAPTER ----3
AdvantagesAnd
Disadvantages of 2G GSM
7/28/2019 Complete Project Report
9/92
Advantages of 2G GSM GSM is mature; this maturity means a more stable network with robust features.
Less signal deterioration inside buildings.
Ability to use repeaters.
Talktime is generally higher in GSM phones due to the pulse nature of
transmission.
The availability ofSubscriber Identity Modules allows users to switch networks
and handsets at will, aside from a subsidy lock.
GSM covers virtually all parts of the world so international roaming is not a
problem.
The much bigger number ofsubscribers globally creates a betternetwork effect
for GSM handset makers, carriers and end users.
Disadvantages of 2G GSM Pulse nature of TDMA transmission used in 2G interferes with some electronics,
especially certain audio amplifiers. 3G uses W-CDMA now.
Intellectual property is concentrated among a few industry participants, creating
barriers to entry for new entrants and limiting competition among phone
manufacturers.[citation needed]
GSM has a fixed maximum cell site range of 35 km, which is imposed by
technical limitations.
http://en.wikipedia.org/wiki/Cell_phone_repeaterhttp://en.wikipedia.org/wiki/Subscriber_Identity_Modulehttp://en.wikipedia.org/wiki/Subsidy_lock_(cellular)http://en.wikipedia.org/wiki/List_of_mobile_network_operatorshttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/List_of_mobile_network_operatorshttp://en.wikipedia.org/wiki/Network_effecthttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Timing_advancehttp://en.wikipedia.org/wiki/Cell_phone_repeaterhttp://en.wikipedia.org/wiki/Subscriber_Identity_Modulehttp://en.wikipedia.org/wiki/Subsidy_lock_(cellular)http://en.wikipedia.org/wiki/List_of_mobile_network_operatorshttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/List_of_mobile_network_operatorshttp://en.wikipedia.org/wiki/Network_effecthttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Timing_advance7/28/2019 Complete Project Report
10/92
CHAPTER------4
GSM ARCHITECTURE
7/28/2019 Complete Project Report
11/92
GSM ARCHITECTURE ------------GSM consists of many subsystems which are as follows ---
1. The Mobile Station(MS)
2. Base Station subsystem(BSS)
3. Network and Swiching subsystem(NSS)
.
4 Operation subsystem(OSS) GSM
MS BSS NSS OSS
7/28/2019 Complete Project Report
12/92
Fig: Architecher of global system for mobilecommunications
1.The Mobile Station(MS)---- It may be a stand alone piece of equipment for certain services or support the
connection of external terminals.
7/28/2019 Complete Project Report
13/92
MS includes mobile equipment(ME) and a subscriber identity module (SIM) .
SIM a subscriber module which stores all subscriber related information.
ME can not be personali assigned to one subscriber .
When a subscribers SIM is inserted in ME of an MS , that MS belongs to subscriber
and call is deliver to that MS .
.2. Base Station Subsystem(BSS) -------------
The Base Station Subsystem (BSS) is the section of a traditional cellulartelephone networkwhich is responsible for handling traffic and signaling between a
mobile phone and theNetwork Switching Subsystem.
The BSS carries out transcoding The BSS carries out transcoding of speech channels,
allocation of radio channels to mobile phones, paging, quality management of
transmission and reception over the Air interface and many other tasks related to the
radio network.
BSS consists of a base transceiver station (BTS)and a base station controller (BSC)
which may cotrol several BTSs .
BTS contains an equipment of transmitting and receiving radio signals similar to ME
of an MS.
3. Network and Swiching subsystem(NSS)---------
http://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Network_Switching_Subsystemhttp://en.wikipedia.org/wiki/Paging_(telecommunications)http://en.wikipedia.org/wiki/Transmissionhttp://en.wikipedia.org/wiki/Receptionhttp://en.wikipedia.org/wiki/Air_interfacehttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Network_Switching_Subsystemhttp://en.wikipedia.org/wiki/Paging_(telecommunications)http://en.wikipedia.org/wiki/Transmissionhttp://en.wikipedia.org/wiki/Receptionhttp://en.wikipedia.org/wiki/Air_interface7/28/2019 Complete Project Report
14/92
NSS includes main swiching of GSM.
It manages the communication between GSM users and other telecommunications
users.
It is owned and deployed by mobile phone operators and allows mobile phones to
communicate with each other and telephones in the widertelecommunications
network.
The architecture closely resembles a telephone exchange
The Network Switching Subsystem, also referred to as the GSM core network,
usually refers to the circuit-switched core network, used for traditional GSM services
such as voice calls, SMS, and Circuit Switched Data calls.
NSS management consists of ----
i) Mobile Service Switching Centre(MSC)
ii)Interworking Function(IWF)
iii)Home Location Register(HLR)----
The 'Home Location Register'or HLR is a central database that contains details
of each mobile phone subscriber that is authorized to use the GSM core network.
The HLR stores details of everySIM card issued by the mobile phone operator
http://en.wikipedia.org/wiki/Mobile_phone_operatorhttp://en.wikipedia.org/wiki/Telephonehttp://en.wikipedia.org/wiki/Telecommunications_networkhttp://en.wikipedia.org/wiki/Telecommunications_networkhttp://en.wikipedia.org/wiki/Telephone_exchangehttp://en.wikipedia.org/wiki/GSM_serviceshttp://en.wikipedia.org/wiki/Short_message_servicehttp://en.wikipedia.org/wiki/Circuit_Switched_Datahttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/Mobile_phone_operatorhttp://en.wikipedia.org/wiki/Mobile_phone_operatorhttp://en.wikipedia.org/wiki/Telephonehttp://en.wikipedia.org/wiki/Telecommunications_networkhttp://en.wikipedia.org/wiki/Telecommunications_networkhttp://en.wikipedia.org/wiki/Telephone_exchangehttp://en.wikipedia.org/wiki/GSM_serviceshttp://en.wikipedia.org/wiki/Short_message_servicehttp://en.wikipedia.org/wiki/Circuit_Switched_Datahttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/SIM_cardhttp://en.wikipedia.org/wiki/Mobile_phone_operator7/28/2019 Complete Project Report
15/92
iv) Visitor Location Register (VLR)-----
The Visitor Location Register or VLR is a temporary database of the subscribers
who have roamed into the particular area which it serves.
Each Base Station in the network is served by exactly one VLR, hence a
subscriber cannot be present in more than one VLR at a time.
v)Gateway MSC(GMSC)
vi)Signaling Transfer Point(STP)
4.Operation subsystem--------
There are areas of OSS
i)Network operation and maintance functions
ii)Subscription management, including charging and billing
iii)Mobile equipment management
http://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/Base_Transceiver_Stationhttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/Base_Transceiver_Station7/28/2019 Complete Project Report
16/92
A-Interface A-bis interfaceRadio
Air -interface
MSC
OAM
BTSBSC
MS
HLR
VLR
7/28/2019 Complete Project Report
17/92
fig: Functional Architecture and principal interfaces
CHAPTER-----5
Layer modeling (OSI model )
7/28/2019 Complete Project Report
18/92
Layer modeling (OSI model)---
The Open system Interconnection(OSI) of GSM consists of five layers---
Transmisson(TR)
Radio recorce management(RR)
Mobility management(MM)
Communition management(CM) and
Opertion, administration, and maintenance(OAM)
Users
Operators
7/28/2019 Complete Project Report
19/92
fig: The functional planes of GSM
The lower layers corresponds the short-time-scale function, the upper layers are long-
time-scale-functions.
The transmission layer set up a connection between MS and BTS .
The RR layer refers to the protocol for the management of the transmission over the radio
interface and provides a stable link between the MS and BSC
The BSS performs the most of RR functions.
The management layer
1. manages the subscriber databases , including location data, and
2. manages the authentication activities , SIM,HLR, and AUC,
Transmission
RR
MMOAM
CM
7/28/2019 Complete Project Report
20/92
the NSS is the significant element in the CM layer. The following are the functions are
the parts of the CM layer ----
1. Call controlthe CM layer sets up calls , maintains calls, and releases calls. The
CM layer interacts among MSC/VLR, GMSC, IWF , AND HLR for managing
circuit-oriented services, including speech and circuit data.
2. Supplementary services management-- Allows users to have some control of
their calls in the network, and has specific variations from the basic services .
3. Short message service(SMS)---- related to the point-to point SMS .A SMS
service center (SMS -SC) may connect to several GSM networks. Short message
transmission requires setting up a signaling connection between the mobile station
and the MSC . The two functions of SMS are ----
i) Mobile-originated short message
ii) Mobile-terminated short message
CHAPTER ----6
Transmission
7/28/2019 Complete Project Report
21/92
Transmission ----
A 4-kHz analog speech signal converts to a 64 kbps digital signal , then down
converts to 13 kbps before modulation. Using a rate of 13-kbps instead of 64 kbps
allows the 13-kbps data rate transmission to occur over a narrowband channel . Since the
radio spectrum is a precious and li8mited resource, using less bandwidth per channel
provides more channels within a given radio spectrum.
Digital speech uses.
1. regular pulse excitation (RPE)---Generates the impulse noise to simulate the
nature of speech.
2. Linear prediction coding(LPC)----- Generates speech waveform by using a filter
with eight transmitted coefficients with a speech frame of 20 ms ; 260 bits
represent a 20ms speech frame .
7/28/2019 Complete Project Report
22/92
There are two modes of transmission in GSM , continuous (normal mode ) and
discontinuous .
The discontinuous transmission decreases the effective radio transmission encoding
of speech at 13 kbps from a bit rate around 500 bps without speech.
CHAPTER ---7
7/28/2019 Complete Project Report
23/92
GSM Channels and channel modes
GSM Channels and channel modes-------
Channel structure---- The services offered to users have four different modes,three data modes, and one speech mode. The radio transmission uses the physicalchannels.
7/28/2019 Complete Project Report
24/92
Fig:(b)
Fig: Interconnection with ISDN
(a)PSTN user to ISDN user, (b) GSM user to ISDN user
Physical Channels-----There are three kinds of physical channels , also called
traffic channels (TCHs):
1. TCH/F(Full rate)Transmits a speech code of 13 kbps or three data-mode rates,
12, 6, and 3.6 kbps.
2. TCH/H(half rate) --- Transmits speech code of 7 kbps or two data modes, 6 and
3.6 kbps .
Personal
computerPSTN ISDN
Personal
computer
Personalcomputer
GSM ISDNPersonalcomputer
Fig:(a)
7/28/2019 Complete Project Report
25/92
3. TCH/(one-eighth rate)Used for low-rate signaling channels, common channels,
and data channels.
Logical channels ----
Common channels. all the common channels are embedded in different traffic
channels They are grouped by the same cycles(51.8 BP) where BP is burst period i.e.
time slot which is 577micro sec.
Downlink common channels ----There are five downlink unidirectional channels,
shared or grouped by a TCH.
Frequency correction channels (FCCH)
Synchronization channels (SCH)
Broadcast control channels (BCCH
Paging and access grant channel(PAGCH)
Call broadcast channel (CBCH)
Uplink common channels -----The random access channel (RACH) is the only common
uplink channel RACH is the channel that the mobile station chooses to access the calls .
Signaling channels
Slow associated control channel (SACCH)
7/28/2019 Complete Project Report
26/92
CHAPTER ----8
TECHNICAL VIEW
7/28/2019 Complete Project Report
27/92
TECHNICAL VIEW--------
GSM is a cellular network, which means that mobile phones connect to it by
searching for cells in the immediate vicinity. GSM networks operate in four different frequency ranges.
Most GSM networks operate in the 900 MHz or 1800 MHz bands.
There are two types of frequency bands used in GSM.
In the 900 MHz band the uplinkfrequency band is 890915 MHz, and the
downlinkfrequency band is 935960 MHz.
This 25 MHz bandwidth is subdivided into 124 carrier frequency channels, each
spaced 200 kHz apart.
Time division multiplexing is used to allow eight full-rate or sixteen half-rate
speech channels perradio frequency channel.
There are eight radio timeslots (giving eightburstperiods) grouped into what iscalled a TDMA frame.
Half rate channels use alternate frames in the same timeslot. The channel data
rate is 270.833 kbit/s, and the frame duration is 4.615 ms.
The transmission power in the handset is limited to a maximum of 2 watts in
GSM850/900 and 1 watt in GSM1800/1900.
GSM has used a variety of voice codices to squeeze 3.1 kHz audio into between
5.6 and 13 kbit/s.
http://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/GSM_frequency_rangeshttp://en.wikipedia.org/wiki/Uplinkhttp://en.wikipedia.org/wiki/Downlinkhttp://en.wikipedia.org/wiki/Time_division_multiplexinghttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Burst_transmissionhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Codechttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/GSM_frequency_rangeshttp://en.wikipedia.org/wiki/Uplinkhttp://en.wikipedia.org/wiki/Downlinkhttp://en.wikipedia.org/wiki/Time_division_multiplexinghttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Burst_transmissionhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Codec7/28/2019 Complete Project Report
28/92
Originally, two codecs, named after the types of data channel they were allocated,
were used, called Half Rate (5.6 kbit/s) and Full Rate (13 kbit/s). These used a
system based upon linear predictive coding (LPC).
In addition to being efficient with bitrates, these codecs also made it easier to
identify more important parts of the audio, allowing the air interface layer to
prioritize and better protect these parts of the signal
GSM was further enhanced in 1997 with the Enhanced Full Rate (EFR) codec, a
12.2 kbit/s codec that uses a full rate channel.
Finally, with the development ofUMTS, EFR was refactored into a variable-rate
codec called AMR-Narrowband, which is high quality and robust against interference
when used on full rate channels, and less robust but still relatively high quality when
used in good radio conditions on half-rate channels.
Modulation Scheme----------
The modulationused in GSM is Gaussian minimum-shift keying(GMSK), a kind of
continuous-phase frequency shift keying. In GMSK, the signal to be modulated onto the
carrier is first smoothed with a Gaussianlow-pass filterprior to being fed to a frequency
modulator, which greatly reduces the interference to neighboring channels (adjacent
channel interference).
Bandwidth time product BT= 0.3
http://en.wikipedia.org/wiki/Half_Ratehttp://en.wikipedia.org/wiki/Full_Ratehttp://en.wikipedia.org/wiki/Linear_predictive_codinghttp://en.wikipedia.org/wiki/Enhanced_Full_Ratehttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/Adaptive_Multi-Ratehttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Gaussian_minimum-shift_keyinghttp://en.wikipedia.org/wiki/Gaussian_minimum-shift_keyinghttp://en.wikipedia.org/wiki/Frequency_shift_keyinghttp://en.wikipedia.org/wiki/Gaussian_functionhttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Interferencehttp://en.wikipedia.org/wiki/Half_Ratehttp://en.wikipedia.org/wiki/Full_Ratehttp://en.wikipedia.org/wiki/Linear_predictive_codinghttp://en.wikipedia.org/wiki/Enhanced_Full_Ratehttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/Adaptive_Multi-Ratehttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Gaussian_minimum-shift_keyinghttp://en.wikipedia.org/wiki/Frequency_shift_keyinghttp://en.wikipedia.org/wiki/Gaussian_functionhttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Interference7/28/2019 Complete Project Report
29/92
Minimum means the minimum tone separation. GMSK utilizes
A small spectrum bandwidth to send a GSM carrier channel. The modulation rate of a
GSM carrier channel is 270 kbps.
Generating a GMSK
Waveform
GMSK as implemented by quadrature signal processing at baseband followquadrature modulator
7/28/2019 Complete Project Report
30/92
GMSK is based on MSK
Minimum Shift Keying Linear phase changes Spectrally efficient
At baseband, bit transitions are represented by
cycle sinusoid
MSK
7/28/2019 Complete Project Report
31/92
Frequency Hopping
In frequency hopping systems, the transmitter changes the carrier frequency according to
a certain "hopping" pattern . The advantage is that the signal sees a different channel and
a different set of interfering signals during each hop. This avoids the problem of failing
communication at a particular frequency, because of a fade or a particular interferer.
Slow and Fast Hopping
There are two kinds of frequency hopping Slow Frequency Hopping (SFH)
In this case one or more data bits are transmitted within one hop. An advantage is
that coherent data detection is possible. Often, systems using slow hopping also
employ (burst) error control coding to restore loss of (multiple) bits in one hop.
http://wireless.per.nl/reference/chaptr05/spreadsp/fhseq.htmhttp://wireless.per.nl/reference/chaptr05/spreadsp/fhseq.htm7/28/2019 Complete Project Report
32/92
Fast Frequency Hopping (FFH)
One data bit is divided over multiple hops. In fast hopping, coherent signal
detection is difficult, and seldom used. Mostly, FSK or MFSK modulation is used.
Slow frequency hopping is a popular technique forwireless LANs.
In GSM telephony, slow frequency hopping can be used, at the discretion of the network
control software. It avoids that a stationary terminal that happens to be located in a fade
looses its link to the base station.
As nearby hopping interferers are unlikely to continuously transmit in the same frequency
slot as the reference user, the near-far problem is less severe than in direct sequence(DS)
CDMA. Particularly for wireless LANs, where terminals can be located anywhere, this
advantage made SFH popular.
http://wireless.per.nl/reference/chaptr01/wrlslans/wlan.htmhttp://wireless.per.nl/reference/chaptr01/telephon/gsm/gsm.htmhttp://wireless.per.nl/reference/chaptr05/cdma/dscdma.htmhttp://wireless.per.nl/reference/chaptr05/cdma/dscdma.htmhttp://wireless.per.nl/reference/chaptr01/wrlslans/wlan.htmhttp://wireless.per.nl/reference/chaptr01/telephon/gsm/gsm.htmhttp://wireless.per.nl/reference/chaptr05/cdma/dscdma.htm7/28/2019 Complete Project Report
33/92
7/28/2019 Complete Project Report
34/92
Time division multiple access--------
Time division multiple access (TDMA) is a channel access method for shared
medium (usually radio) networks.
It allows several users to share the same frequency channel by dividing the signal
into different timeslots. The users transmit in rapid succession, one after the
other, each using his own timeslot. This allows multiple stations to share the same
transmission medium (e.g. radio frequency channel) while using only the part of
itsbandwidth they require.
TDMA is used in the digital 2Gcellular systems such asGlobal System for
Mobile Communications (GSM), IS-136,Personal Digital Cellular(PDC) and
iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT)standard forportable phones.
It is also used extensively in satellite systems, and combat-net radio systems.
TDMA frame structure showing a data stream divided into frames and those
frames divided into timeslots.
TDMA is a type ofTime-division multiplexing, with the special point that instead
of having one transmitterconnected to one receiver, there are multiple
transmitters. In the case of theuplinkfrom a mobile phone to abase station thisbecomes particularly difficult because the mobile phone can move around and
vary the timing advance required to make its transmission match the gap in
transmission from its peers.
http://en.wikipedia.org/wiki/Channel_access_methodhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/w/index.php?title=Frequency_channel&action=edithttp://en.wikipedia.org/wiki/Bandwidthhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Cellular_systemhttp://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/IS-136http://en.wikipedia.org/wiki/Personal_Digital_Cellularhttp://en.wikipedia.org/wiki/Personal_Digital_Cellularhttp://en.wikipedia.org/wiki/IDENhttp://en.wikipedia.org/wiki/Digital_Enhanced_Cordless_Telecommunicationshttp://en.wikipedia.org/wiki/Portable_phonehttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Combat-net_radiohttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Uplinkhttp://en.wikipedia.org/wiki/Uplinkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Base_stationhttp://en.wikipedia.org/wiki/Base_stationhttp://en.wikipedia.org/wiki/Channel_access_methodhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/w/index.php?title=Frequency_channel&action=edithttp://en.wikipedia.org/wiki/Bandwidthhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Cellular_systemhttp://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/Global_System_for_Mobile_Communicationshttp://en.wikipedia.org/wiki/IS-136http://en.wikipedia.org/wiki/Personal_Digital_Cellularhttp://en.wikipedia.org/wiki/IDENhttp://en.wikipedia.org/wiki/Digital_Enhanced_Cordless_Telecommunicationshttp://en.wikipedia.org/wiki/Portable_phonehttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Combat-net_radiohttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Uplinkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Base_station7/28/2019 Complete Project Report
35/92
TDMA features
Shares single carrier frequency with multiple users
Non-continuous transmission makes handoff simpler
Slots can be assigned on demand in dynamic TDMA Less stringent power control than CDMA due to reduced intra cell interference
Higher synchronization overhead than CDMA
Advanced equalization is necessary for high data rates
Cell breathing (borrowing resources from adjacent cells) is more complicated than
in CDMA
Frequency/slot allocation complexity
Pulsating power envelop: Interference with other devices
http://en.wikipedia.org/wiki/CDMAhttp://en.wikipedia.org/wiki/CDMA7/28/2019 Complete Project Report
36/92
Burst and training sequences--------
In TDMA signal transmits in bursts. The time interval of the burst brings the
amplitude of a transmitted signal up from a starting value of 0 to its normal value . Then a
packet of bits is transmitted by a modulated signal Afterward, the amplitude decreases to
zero .
These burst occur only at the mobile station transmission or at the base station if the
adjacent burst is not transmitted.
There are trail bits and training sequence bits within a burst. The tail bits are three 0 bits
added at the beginning and at the end of each burst ,which provide the guard time.
The training sequence is a sequence known by the receiver which trains an equalizer, a
device which reduces the intersymbol interference.
The training sequence bits are inserted in the middle of a time slot some time is called a
midamble , for the same purpose as a preamble , so that the equalizer can minimize its
maximum distance with any useful bit.
There are eight different training sequences , with little between any two sequences to
distinguish the received signal from the interference signal .
There are several kinds of bursts :
1. Normal bursts
2. Access bursts
3. F and S bursts
7/28/2019 Complete Project Report
37/92
1.The normal burst used in TCH:
3. The F and S bursts ,used in FCCH and has the simplest format
3 57 1 26 1 57 3
7 41 1 35 3
3 38 1 64 1 38 3
2. Access bursts used in RACH
7/28/2019 Complete Project Report
38/92
Handover----
The GSM handover is not specified as a standard . It is a feature of mobile
assistance handover (MAHO) and is carried out within the unit.The mobile stationscans for another radio carrier under direction of a base station .It moniters those
time slots which are not its own assigned time slots for receiving the signal .
In this case , on the request of a base station, the signal strength of a
specified radio carrier is measured in one time frame , and on request , the
measurements are forwarded to the base station to asset in the handover process. This
is called MAHO .
fig : Handover in GSM
7/28/2019 Complete Project Report
39/92
The MSC uses two sets of information to decide whether a handover should be initiated
and which BTS is the candidate BTS for the handover . The two sets are ----
1. the signal strengths of the MS as received at the neighboring BTSs and
2. the strengths of neighboring BTSs received at the MS . The latter information is
from MAHO.
GSM provides handover processes for the following:
Quality (uplink/downlink).
Interference (uplink/downlink).
RF level (uplink/downlink).
MS distance.
Power budget.
More handover algorithms have been developed for specific applications, such as
microcellular, and are currently being implemented.
Mobile and wireless Communication
- Support for voice and data services
Total mobility
International access, chip-card enables use of access points of different
providers
Worldwide connectivity
One number, the network handles localization
High capacity
7/28/2019 Complete Project Report
40/92
Better frequency efficiency, smaller cells, more customers per cell
High transmission quality
High audio quality and reliability for wireless, uninterrupted phone calls at higher
speeds (e.g., from cars, trains)
Security functions
- Access control, authentication via chip-card and PIN
7/28/2019 Complete Project Report
41/92
CHAPTER----9
Cell Size in GSM
7/28/2019 Complete Project Report
42/92
Cell Size in GSM -------
There are four different cell sizes in a GSM networkmacro, micro, pico and
umbrella cells
The coverage area of each cell varies according to the implementation
environment.
Macro cells can be regarded as cells where thebase stationantenna is installed on
a mast or a building above average roof top level.
Micro cells are cells whose antenna height is under average roof top level; they
are typically used in urban areas.
Picocells are small cells whose coverage diameter is a few dozen meters; they are
mainly used indoors.
Umbrella cells are used to cover shadowed regions of smaller cells and fill in
gaps in coverage between those cells.
Cell horizontal radius varies depending on antenna height, antenna gain and
propagation conditions from a couple of hundred meters to several tens of
kilometers. The longest distance the GSM specification supports in practical use
is 35 kilometres (22 mi).
There are also several implementations of the concept of an extended cell, where the
cell radius could be double or even more, depending on the antenna system, the type
of terrain and the timing advance.
http://en.wikipedia.org/wiki/Base_stationhttp://en.wikipedia.org/wiki/Antenna_(electronics)http://en.wikipedia.org/wiki/Antenna_(electronics)http://en.wikipedia.org/wiki/Kilometrehttp://en.wikipedia.org/wiki/Milehttp://en.wikipedia.org/wiki/Timing_advancehttp://en.wikipedia.org/wiki/Base_stationhttp://en.wikipedia.org/wiki/Antenna_(electronics)http://en.wikipedia.org/wiki/Kilometrehttp://en.wikipedia.org/wiki/Milehttp://en.wikipedia.org/wiki/Timing_advance7/28/2019 Complete Project Report
43/92
Indoor coverage is also supported by GSM and may be achieved by using an indoor
picocell base station, or an indoor repeaterwith distributed indoor antennas fed
through power splitters, to deliver the radio signals from an antenna outdoors to the
separate indoor distributed antenna system.
These are typically deployed when a lot of call capacity is needed indoors, for
example in shopping centers or airports. However, this is not a prerequisite, since
indoor coverage is also provided by in-building penetration of the radio signals from
nearby cells.
CHAPTER ------10
Services Provided by GSM
http://en.wikipedia.org/wiki/Cellular_repeaterhttp://en.wikipedia.org/wiki/Cellular_repeater7/28/2019 Complete Project Report
44/92
Services Provided by GSM:
GSM services are a standard collection of applications and features available to mobile
phone subscribers all over the world.
The design of the service is moderately complex because it must be able to locate a
moving phone anywhere in the world, and accommodate the relatively small battery
capacity, limited input/output capabilities, and weak radio transmitters on mobile devices.
1. General Packet Radio Service (GPRS)
Apacket-switched connection chops data into distinct chunks, known as
packets, which may arrive at their destination via different routes, at different
times, out of sequence, or (hopefully only occasionally) not at all. An
intermediate protocol, like TCP, might be used to ensure the original datastream is reassembled at the destination (by putting packets in order and
retransmitting missing ones, if necessary).
The advantage of packet-switched connections is that bandwidth is only used
when there is actually data to transmit
Telecommunication services can be classified into
1. Bearer Services,
2. Teleservices, and
3. Supplementary Services.
http://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Packet-switchedhttp://en.wikipedia.org/wiki/Transmission_Control_Protocolhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Packet-switchedhttp://en.wikipedia.org/wiki/Transmission_Control_Protocol7/28/2019 Complete Project Report
45/92
7/28/2019 Complete Project Report
46/92
When a call is made from a GSM Mobile Station, the type of service requested is
indicated in the set-up message. This means that the GSM operator has the option to treat
emergency calls differently by allowing mobile equipment without a SIM card to make
them.
4. Bearer Services:
A bearer service provides the capacity necessary to transmit
appropriate signals between two access points providing an interface to the network. In
GSM asynchronous and synchronous data transmission rates upto 9.6 kbps are supported.
5.Supplementary Services:
The supplementary services basically consist of call forwarding and call barring.
5.1 Call Forwarding:
The Call Forwarding Supplementary Service is used to divert calls from the
original recipient to another number, and is normally set up by the subscriber himself. It
can be used by the subscriber to divert calls from the Mobile Station when the subscriberis not available, and so to ensure that calls are not lost. A typical scenario would be a
salesperson turns off his mobile phone during a meeting with customers, but does not
with to lose potential sales leads while he is unavailable.
5.2 Call Barring:
The concept of barring certain types of calls might seem to be a supplementary
disservice rather than service. However, there are times when the subscriber is not the
actual user of the Mobile Station, and as a consequence may wish to limit its
functionality, so as to limit the charges incurred. Alternatively, if the subscriber and user
are one and the same, the Call Barring may be useful to stop calls being routed to
international destinations when they are routed. The reason for this is because it is
7/28/2019 Complete Project Report
47/92
expected that the roaming subscriber will pay the charges incurred for international re-
routing of calls. So, GSM devised some flexible services that enable the subscriber to
conditionally bar calls.
Newer GSM Services:
1. Number Identification:
Calling Line Identification Presentation: This service deals with the
presentation of the calling party's telephone number. The concept is for thisnumber to be presented, at the start of the phone ringing, so that the called
person can determine who is ringing prior to answering. The person
subscribing to the service receives the telephone number of the calling party.
Calling Line Identification Restriction: A person not wishing their
number to be presented to others subscribes to this service. In the normal
course of event, the restriction service overrides the presentation service.
Connected Line Identification Presentation: This service is provided to
give the calling party the telephone number of the person to whom they are
connected. This may seem strange since the person making the call should
know the number they dialled, but there are situations (such as forwardings)
where the number
2 .Multi-Party:
Multi-Party Service: This service is similar to a conference type service, in
that several calls may be connected with all parties talking to each other.
7/28/2019 Complete Project Report
48/92
7/28/2019 Complete Project Report
49/92
CHAPTER---11
Conclusion
7/28/2019 Complete Project Report
50/92
Conclusion:
Thus it seems that probably the potential of GSM is not fully realized
till date. The real power of its capabilities is yet to be harnessed and will
influence the human life in a big way in the future. The future has a lot to
see in terms of the new generation state-of-the -art cellular phones and other
devices being used in common.
7/28/2019 Complete Project Report
51/92
CHAPTER----12
Overview of GSM
7/28/2019 Complete Project Report
52/92
Overview of GSM-----------
Summary of physical layer parameters----TDMA Structure 8 time slots per radio carrier
Time slots .577 ms
Frame interval 8 time slots =4.615ms
Radio carrier no. 124 radio carrier (935-960mhz uplink
890-915mhz downlink)
Modulation Scheme Gaussian MSK BT=.3
Frequency hopping Slow frequency hopping 217hops/s)
GSMs Strenth--------
GSM is first to apply the TDMA scheme developed for mobile radio
systems . It has several features ----
1. Roaming in European countries
2. Use of SIM cards
3. Control of transmission power
4. Discontinuous transmission
5. Mobile assisted handover
7/28/2019 Complete Project Report
53/92
Convolution coding
7/28/2019 Complete Project Report
54/92
CHAPTER--- 1
Abstract
Abstract
7/28/2019 Complete Project Report
55/92
Channel coding refers to the class of signal transformations designed toimprove communication performance by enabling the transmitted signals to betterwithstand the effects of various channel impairments, such as noise , interference, and
fading. These signal processing techniques can be thought of as vehicles foraccomplishing desirable system trade offs (e.g., error performance vs. bandwidth, powervs. bandwidth).
The primary objective of spectrally efficient modulation techniques is tomaximize bandwidth efficiency. The increasing demand for digital transmission channelshas led to the investigation of spectrally efficient modulation technique to maximizebandwidth efficiency and thus help to ameliorate the spectral congestion problem.
The channel coding techniques viz. Linear Block Code, Convolutional Codeetc. have generally not been associated with voice grade telephone channels. Recently,
however, there has been considerable interest in techniques that can provide coding gainfor bandlimited channels. The motivation is to enable the reliable transmission of higherdata rate over voice grade channels.
In this design, various aspects of information theory are studied and aConvolutional encoder is implemented
CHAPTER----2
7/28/2019 Complete Project Report
56/92
INFORMATION THEORY ANDCODING
INFORMATION THEORY AND
CODING
7/28/2019 Complete Project Report
57/92
For its efficient and reliable operation a digital communication system dependsupon different types of encoders and decoders along with some other equipment.Decoders are used to decode the original bit stream from the encoded bit stream. Theencoders are used for two purposes:
Source coding
Channel coding
In this section I will discuss about these two types of coding used in digitalcommunication system, so that we can get a clear concept of coding. Source coding andchannel coding play a very important role in design of an efficient and a reliablecommunication system.
In the present section, first I will discuss some information theoretic terms (in detail),
which are frequently used in the coding theoy, then I will discuss about the coding
CHAPTER ----3
7/28/2019 Complete Project Report
58/92
Coding theory
Coding theory------
7/28/2019 Complete Project Report
59/92
Coding theory is a branch ofmathematics and computer science dealing with the error-
prone process of transmitting data across noisy channels, via clever means, so that a large
number of errors that occur can be corrected. It also deals with the properties of codes,
and thus with their fitness for a specific application.
There are two classes of codes.
1. Source coding (Data compression)
2. Channel coding (Forward error correction)
The first, source encoding, attempts to compress the data from a source in order to
transmit it more efficiently. We see this practice every day on the Internet where the
common "Zip" data compression is used to reduce the network load and make files
smaller. The second, channel encoding adds extra data bits, commonly called redundancy
bits, to make the transmission of data more robust to disturbances present on the
transmission channel. The ordinary user may not be aware of many applications using
channel coding. A typical music CD uses a powerful Reed-Solomon code to correct for
scratches and dust. In this application the transmission channel is the CD itself. Cell
phones also use powerful coding techniques to correct for the fading and noise of high
frequency radio transmission. Data modems, telephone transmissions, and of courseNASA all employ powerful channel coding techniques to get the bits through.
CHANNEL ENCODING-----
Channel encoding theory is to find codes which transmit quickly, contain many
valid code words and can correct or at least detect many errors. While not
http://en.wikipedia.org/wiki/Mathematicshttp://en.wikipedia.org/wiki/Computer_sciencehttp://en.wikipedia.org/wiki/Noisy_channelhttp://en.wikipedia.org/wiki/Codehttp://en.wikipedia.org/wiki/Data_compressionhttp://en.wikipedia.org/wiki/Forward_error_correctionhttp://en.wikipedia.org/wiki/Reed-Solomon_error_correction#Data_storagehttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Code_wordhttp://en.wikipedia.org/wiki/Error_detectionhttp://en.wikipedia.org/wiki/Mathematicshttp://en.wikipedia.org/wiki/Computer_sciencehttp://en.wikipedia.org/wiki/Noisy_channelhttp://en.wikipedia.org/wiki/Codehttp://en.wikipedia.org/wiki/Data_compressionhttp://en.wikipedia.org/wiki/Forward_error_correctionhttp://en.wikipedia.org/wiki/Reed-Solomon_error_correction#Data_storagehttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Code_wordhttp://en.wikipedia.org/wiki/Error_detection7/28/2019 Complete Project Report
60/92
mutually exclusive, performance in these areas is a trade off. So, different codes
are optimal for different applications.
The needed properties of this code mainly depend on the probability of errors
happening during transmission. In a typical CD, the impairment is mainly dust or
scratches. Thus codes are used in an interleaved manner. The data is spread out
over the disk. Although not a very good code, a simple repeat code can serve as
an understandable example. Suppose we take a block of data bits (representing
sound) and send it three times. At the receiver we will examine the three
repetitions bit by bit and take a majority vote. The twist on this is that we don't
merely send the bits in order. We interleave them. The block of data bits is first
divided into 4 smaller blocks. Then we cycle through the block and send one bit
from the first, then the second, etc. This is done three times to spread the data out
over the surface of the disk. In the context of the simple repeat code, this may not
appear effective. However, there are more powerful codes known which are very
effective at correcting the "burst" error of a scratch or a dust spot when this
interleaving technique is used.
The term algebraic coding theory denotes the sub-field of coding theory where the
properties of codes are expressed in algebraic terms and then further researched.
Algebraic Coding theory, is basically divided into two major types of codes
1. Linear block codes
2. Convolutional codes
It analyzes the following three properties of a code -- mainly:
code word length total number of valid code words
7/28/2019 Complete Project Report
61/92
Channel Coding Theorem:
The channel coding theorem for a DMC is stated as follows:
Given a DMS X with entropy H (X) bits/symbol and a DMC with a capacity Cs
bits/symbol, if H (X) C, there exist a coding scheme for which the source output can be
transmitted over the channel with an arbitrarily small probability error.
Conversely, if H (X) > Cs, it is not possible to transmit information over the channel with
an arbitrarily small probability error. Note that the channel-coding theorem only asserts
the existence of code but it does not tell us how to construct these codes.
The block diagram the communication channel is shown in the fig at next page.
Applications of coding theory
Another concern of coding theory is designing codes that help synchronization. A code
may be designed so that a phase shift can be easily detected and corrected and that
multiple signals can be sent on the same channel. There is an interesting class of codes
we see every day on our cell phones. These are the Code Division Multiple Access
(CDMA) codes.
7/28/2019 Complete Project Report
62/92
CONVOLUTIONAL
ENCODING
In telecommunication, a convolutional code is a type oferror-correcting
code in which (a) each m-bitinformation symbol (each m-bit string) to be
encoded is transformed into an n-bit symbol, where m/n is the code rate (n
m) and (b) the transformation is a function of the last kinformation symbols,
where kis the constraint length of the code.
Where convolutional codes are used
Convolutional codes are often used to improve the performance of digital
radio, mobile phones, satellite links, and Bluetooth implementations.
http://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Error-correcting_codehttp://en.wikipedia.org/wiki/Error-correcting_codehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Binary_stringhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Error-correcting_codehttp://en.wikipedia.org/wiki/Error-correcting_codehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Binary_stringhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Bluetooth7/28/2019 Complete Project Report
63/92
CHAPTER----4
Convolution codes
Convolution codes ----
To convolutionally encode data, start with kmemory registers, each holding 1 input bit.Unless otherwise specified, all memory registers start with a value of 0. The encoder has
http://en.wikipedia.org/wiki/Memory_registerhttp://en.wikipedia.org/wiki/Memory_register7/28/2019 Complete Project Report
64/92
n modulo-2 adders, and ngenerator polynomials one for each adder (see figurebelow). An input bit m1 is fed into the leftmost register. Using the generator polynomialsand the existing values in the remaining registers, the encoder outputs n bits. Now bitshift all register values to the right (m1 moves to m0, m0 moves to m-1) and wait for thenext input bit. If there are no remaining input bits, the encoder continues output until all
registers have returned to the zero state.
The figure below is a rate 1/3 (m/n) encoder with constraint length (k) of 3. Generatorpolynomials are G1 = (1,1,1), G2 = (0,1,1), and G3 = (1,0,1). Therefore, output bits arecalculated (modulo 2) as follows:
n1 = m1 + m0 + m-1n2 = m0 + m-1
n3 = m1 + m-1.
mk stage shift registeri/p seq. shifted k bit at a time
1 -----------
n mod-2 adders
1 2 3 ------ n
Encoded Output Sequence
The integer m is a parameter known as the constraint length of the convolution code. Inpractice , n and k are small integers and m is varied to control redundancy. The constraintlength represents the no. of k bit shifts over which a single information bit can influencethe encoder output. Since there are n code bits for each input group of k message bits, thecode rate is k/n message bit per code bit, where k
7/28/2019 Complete Project Report
65/92
In present case convolution encoder is for 1/3 rate .the four outputs of shift registerare s1,s2 , s3 and s4 .
These outputs are inputted in a combinations of ex-or gates to produce a three bitconvolved output u1, u2, and u3 as according to the following generator polynomial.
U1=s1;
U2=s1+s2+s3+s4;
U3=s1+s4+s3.
Application of Convolution codes
Convolutional codes are used in voice band modems (V.32, V.17, and V.34) and in GSMmobile phones, as well as satellite and military communication devices.
Here the idea is to make every codeword symbol be the weighted sum of the various
input message symbols. This is like convolution used in LTI systems to find the output ofa system, when you know the input and impulse response.
So we generally find the output of the system [convolutional encoder] , which is theconvolution of the input bit, against the states of the convolution encoder, registers.
Fundamentally, convolutional codes do not offer more protection against noise than anequivalent block code. In many cases, they generally offer greater simplicity ofimplementation over a block code of equal power. The encoder is usually a simple circuitwhich has state memory and some feedback logic, normally XOR gates. The decoder canbe implemented in software or firmware.
7/28/2019 Complete Project Report
66/92
CHAPTER ---5
IMPLEMENTATION AND CIRCUIT DESIGN
7/28/2019 Complete Project Report
67/92
IMPLEMENTATION AND CIRCUIT DESIGNThe encoder circuits are usually constructed with a number of adders
(mod2) and memory devices. For digital circuits mod2 adders can be constructed
with XOR logic and memory device by Shift Registers.
Encoder for 1/3Rate:A convolutional encoder transforms k bits of data into n bit codes, but the
coder output depends on the earlier blocks of data that have been processed by
the coder. The general block diagram for an encoder of1/3 rate which is
implemented through hardware is shown in figure 1, where the parameters are:
R = 1/3, n = 3, and constraint length k = 1.
The circuit for this encoder is shown in figure 2. In this circuit an eight bit
serial in parallel out shift register and eight XOR gates are used. Manual clock
has been used to simplify and observe the working of the circuit.
7/28/2019 Complete Project Report
68/92
Hardware Description:For the design of encoder n =3, k =1, K = 3, we need
data source
shift register
mod 2 adders
Different blocks and components are described as follows:
Data Source:For this I have used
5V power supply
1 SPDT switch
In this
5V Logic State 1
0V Logic State 0
SPDT is such type of switch in which when one pole is one side the ground
is connected and logic state 0 is obtained. While when pole is at the other side,
supply voltage is connected and logic state 1 is obtained.
Shift Registers: A group of cascaded flip-flops used to store related bits of
information is known as a register. A register that is used to assemble and store
information arriving from a serial source is called a shift register. Each flip flop
output of a shift register is connected to the input of the following flip flop and a
7/28/2019 Complete Project Report
69/92
7/28/2019 Complete Project Report
70/92
Mod 2 Adder:For this XOR IC 7486 is used. This is a quad 2 input XOR gate.
7/28/2019 Complete Project Report
71/92
Clock:For controlling the operation of the flip flop in the shift register we need
clock cycles which have been generated by 555timer.
For generation of clock f on time 0.5 secs, we want:
Components: Unit
555timer IC 1
10 k resistance 2
100K resistance 1
0.1 F capacitance 2
1000 F capacitance 1
At the pin 3 of timer IC we can obtain clock.
7486 Quadruple 2-Input Exclusive ORGate
These devices contain four independent 2-input exclusive
OR-Gates. They perform the Boolean function Y = A B
= AB + A B in positive logic.
A common application is as a true/ complement 2-input
element. If one of the inputs is low, the other input will be
reproduced in true form at the output. If one of the inputs is
high, the signal on the other input will be reproduced
7/28/2019 Complete Project Report
72/92
inverted at the output. Our component SN7486 is
characterized for operation from 0 0C to 70 0C.
Every IC s characterized by its own
pin architecture,
The architecture for our IC is given as
adjacent showing the top view of the
IC
7/28/2019 Complete Project Report
73/92
Application of Exclusive OR logic:
An exclusive-OR gate has many applications, some of
which can be represented better by alternative logic
symbols.
These are five equivalent Exclusive-OR symbols valid for
an 86 or LS86A gate in positive logic; negation may be
shown at any two ports.
7/28/2019 Complete Project Report
74/92
POWER SUPPLY UNIT
A necessary part of the electronic system is Power
supply . we oftenly use +5volt supply ,all the linear ICs
(OPMP) Requires +15volt supply.
For our work +5 volt supply is enough .
. A d.c. power supply which maintain the output voltage
constant irrespective of a.c. mains fluctuation or load
variation is known as regulated d.c.power supply.
A regulated power supply consists of an ordinary power
supply and voltage regulating devices. The output of
ordinary power supply is fed to the voltage regulator
which produces the final output. The output voltage
remains constant whether the load current changes or
there are fluctuations in the input dc voltages.
COMPONENT USED:
A 12-0-12step down transformer-200ma
Electrolytic capacitor of 1000F
Regulator IC 7805
4 diode IN 4007
LM 7805
Features
Output Current up to 1A
Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
Thermal Overload Protection
Short Circuit Protection
Output Transistor Safe Operating Area Protection
7/28/2019 Complete Project Report
75/92
CHAPTER----6
ABOUT THE CIRCUIT
7/28/2019 Complete Project Report
76/92
ABOUT THE CIRCUIT
The output from the transformer secondary is applied to the
full wave rectifier circuit, which converts the sinusoidal
into full wave rectified output. The filter capacitor at the
out put of the full wave rectifier is charged to the peak
value of the rectified output voltage whenever diodes are
forward biased.
For the filter circuit V(t)=V0(1-exp(-t/RC) for RC circuit
charging V(t)=V0exp(-t/rc) for RC circuit discharging
R= Very small Since the diodes are not forward biased
during the entire positive and negative half cycles of he
input waveform, the voltage across the filter capacitor is a
pulsating dc that is a combination of dc and a ripple
voltage. From the pulsating dc voltage, a regulated +5 dc
voltage is obtained by a regulator IC 7805.The output of IC
7805 is taken through a capacitor of 1 F
7/28/2019 Complete Project Report
77/92
CIRCUIT DIAGRAM
7/28/2019 Complete Project Report
78/92
PCB LAUOUT
7/28/2019 Complete Project Report
79/92
GENERATION OF CLOCK
Here IC 7555 is used for generating the clock pulses.Its IC
configuration is same as that of IC 555.The circuit diagram
for generating he clock pulses is given below
Vcc
GND
LM555/NE555/SA555
7/28/2019 Complete Project Report
80/92
Single Timer
Features :
High Current Drive Capability (200mA)
Adjustable Duty Cycle
Temperature Stability of 0.005%/C
Timing From Sec to Hours
Turn off Time Less Than 2Sec
Applications :
Precision Timing
Pulse Generation
Time Delay Generation
Sequential Timing
Internal Block Diagram :
GND
Trigger
Output
Reset
Description :
7/28/2019 Complete Project Report
81/92
The LM555/NE555/SA555 is a highly stable controller
capable of producing accurate timing pulses. With
monostable operation, the time delay is controlled by one
external resistor and one capacitor. With astable operation,
the frequency and duty cycle are accurately controlled with
two external resistors and one capacitor
COMPONENT USED
POWER SUPPLY UNIT
A 9-0-9 step down transformer-200ma
Electrolytic capacitor of 1000F
Regulator IC 7805
4 diode IN 4007
ASTABLE PULSE GENERATOR
CIRCUIT
2 , 10 K resistor
1 M resistor
Capacitor of .01 F
Capacitor of .1 FCapacitor of 1000 F
diode IN 4007
IC 7555
7/28/2019 Complete Project Report
82/92
CHAPTER ----7
PCB Designing
7/28/2019 Complete Project Report
83/92
PCB Designing
The heart of any electronic project is the PCB.
Without a proper PCB the design may end up in total
failure. A perfect PCB gives a facelift to the appearance
and performance of the circuit and what is of great
importance is its neatness. An easy way to make the PCB is
described below:
Materials Required:
Copper clay boardEnamel Paint or Marker
Hand Drill
Ferric Chloride Solution
In design of PCB, firstly we design the circuit with actual
size of components on graph in design of PCB; firstly we
design the circuit with actual size of components on a graph
paper. Then we make the PCB layout by using the PCB
Designing/Express PCB software. This finally designed
7/28/2019 Complete Project Report
84/92
layout is now screen printed or drawn by hand using
marker on the Copper clay board and is required to remove
extra copper from the clay board. The screen-printed plate
is dipped in the solution of FeCl3 +HCl. The plate is stirred
for 1 or 2 hour or till the unpainted copper area is totally
dissolved. The unwanted copper is dissolved and finally we
get PCB fabricated. This is popularly known as
ETCHING. The etched plate is washed with water and
soap to remove marker ink.
PCB Testing:
The tracks made are checked to be continuous. It is carried
with the help of multimeter to get zero resistance.
Circuit Testing:
1. All individual components should be checked previously
with multimeter.
2. IC base continuity should be checked after soldering.
3. All the components are soldered and check for the
continuity.
7/28/2019 Complete Project Report
85/92
Precautions:
1-While using the PCB designer/Express PCB software we
must be careful about the proper track selection and also try
to reduce the size as much as we can.
2-While etching we must be very careful otherwise the.
Tracks can also be etched. The HCL should be used for
reducing the speed of etching if needed.
3-While soldering we should avoid dry soldering.
4-After soldering the continuity should be checked.
7/28/2019 Complete Project Report
86/92
EXPERIMENT
OBJECT:
To design a convolutional encoder 1\3rate when data bit is 101
OBSERVATION:
Let us assume the generator polynomials :
U1(x)=
U2(x)=
U3(x)=
We assume that initial contents of the shift register zero. By pressing
the clear switch the contents of all flip flops becomes zero. The input data
stream is applied tat serial input port. The clock switch is pressed at
different timings and the register contents shifts one block to right
direction. The output encoded message is obtained as-
7/28/2019 Complete Project Report
87/92
Timing
message
Register contents
Encoded output
S1 S2 S3 S4 U1 U2 U3
T0
T1
T2
T3
T4
T5
T6
T7
T8
7/28/2019 Complete Project Report
88/92
CHAPTER----8
DISCUSSION
7/28/2019 Complete Project Report
89/92
DISCUSSION
During commencement of any work A man has to face many
problems and if he has faced these problems patiently then it is true he will
be successful in his object. In my design I have faced many problems and
tried to remove them, the result of that is now before us.
For hardware implementation of convolutional encoder we have
used shift registers. In shift register, the contents of flip flops are shifted to
the next flip flop when a clock is applied. The shifting in contents of flip
flops is observed when negative edge of clock begins. At a particular instant
the output of flip flops are X-ORed and encoded message is displayed by
LEDs.
If there is any discrepancy in results then this may be due to
presence of noise.
7/28/2019 Complete Project Report
90/92
CHAPTER----9
References
7/28/2019 Complete Project Report
91/92
References
[1] Simon Haykin,Digital Communications (Wiley, 2000)
[2] Bernard Sklar,Digital Communications :
Fundamentals and Applications (Pearson Education Asia,
2001)
[3] John G. Proakis,Digital Communications (McGraw-
Hill, Inc., 1995)
[4] Hwei Hsu,Schaums Outlines : Analog and Digital
Communications (Tata Mc Graw-Hill Publishing
Company Limited, 2004)
[5]William C. Y. Lee Mobile Cellular Telecommunications
,analog and digital systems
7/28/2019 Complete Project Report
92/92
APPENDIX