Cellular phones allow users to make calls from mobile devices by connecting to nearby transmitter towers through radio signals. The document discusses the history and evolution of cellular phones from early analog models weighing 2 pounds that offered 30 minutes of talk time to modern digital cellular networks that support data services in addition to calls. It also describes key components of cellular networks like base stations, switching centers, and databases that help cellular providers manage subscriber identities and locations to route calls and support roaming.

1. Topic “cellular phone”
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Group Members
Muhammad Azam Sohu
Makhno Shar
Syed Muhammad Raghib Shah
Abdul Razique
Bilal jatt

2. Cellular Phone
 Cellular telephone, sometimes called mobile
telephone, is a type of short-wave analog or
digital telecommunication in which a subscriber
has a wireless connection from a mobile phone to
a relatively nearby transmitter. The transmitter's
span of coverage is called a cell. As the cellular
telephone user moves from one cell or area of
coverage to another, the telephone is effectively
passed on to the local cell transmitter.
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3. Cellular Phone
 The first cellular telephone for commercial use
was approved by the Federal Communications
Commission (FCC) in 1983. The phone, a
Motorola DynaTAC 8000X, weighed 2 pounds,
offered just a half-hour of talk time for every
recharging and sold for $3,995
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4. Cellular Phone-Use
 Cellular phone is used by any person to
communicate with each other and this is
mostly used device which is easy to keep
track of about the people and also used to
communicate the important messages and
also mostly used by business people even
during the journey.So it makes life easy
for people as they can communicate even
though they are traveling.
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5.  Cellular refers to communications systems,
especially the Advance Mobile Phone Service
(AMPS), that divide a geographic region into
sections, called cells.The purpose of this division is
to make the most use out of a limited number of
transmission frequencies.
 Each connection, or conversation, requires its own
dedicated frequency, and the total number of
available frequencies is about 1,000. To support
more than 1,000 simultaneous conversations,
cellular systems allocate a set number of
frequencies for each cell. Two cells can use the
same frequency for different conversations so long
as the cells are not adjacent to each other.
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6. Evolution to cellular networks
communication anytime, anywhere
 radio communication was invented by Nikola
Tesla and Guglielmo Marconi: in 1893, Nikola
Tesla made the first public demonstration of
wireless (radio) telegraphy; Guglielmo Marconi
conducted long ditance (over see) telegraphy
1897
 in 1940 the first walkie-talkie was used by the
US military
 in 1947, John Bardeen and Walter Brattain
from AT&T’s Bell Labs invented the transistor
(semiconductor device used to amplify and
switch electronic signals) 6

7. In 1979 the first commercial cellular phone
service was launched by the Nordic Mobile
Telephone (in Finland, Sweden, Norway,
Denmark).
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8. Cellular Systems Generations
 1G (first generation) – voice-oriented systems
based on analog technology; ex.: Advanced
Mobile Phone Systems (AMPS) and cordless
systems
 2G (second generation) - voice-oriented systems
based on digital technology; more efficient and
used less spectrum than 1G; ex.: Global System
for Mobile (GSM) and US Time Division Multiple
Access (US-TDMA)
 3G (third generation) – high-speed voice-
oriented systems integrated with data services;
ex.: General Packet Radio Service (GPRS), Code
Division Multiple Access (CDMA)
 4G (fourth generation) – still experimental, not
deployed yet; based on Internet protocol
networks and will provide voice, data and
multimedia service to subscribers. 8

9. Frequency Reuse
 Is a method used by service providers to
improve the efficiency of a cellular network
and to serve millions of subscribers using a
limited radio spectrum.
 Is based on the fact that after a distance a
radio wave gets attenuated and the signal falls
bellow a point where it can no longer be used
or cause any interference.
 A transmitter transmitting in a specific
frequency range will have only a limited
coverage area.
 Beyond this coverage area, that frequency can
be reused by another transmitter. 9

10. Network Cells
 The entire network coverage area is divided into
cells based on the principle of frequency reuse.
 A cell = basic geographical unit of a cellular
network; is the area around an antenna where a
specific frequency range is used; is represented
graphically as a hexagonal shape, but in reality it
is irregular in shape.
 When a subscriber moves to another cell, the
antenna of the new cell takes over the signal
transmission.
 A cluster is a group of adiacent cells, usually 7
cells; no frequency reuse is done within a cluster.
 The frequency spectrum is divided into sub bands
and each sub band is used within one cell of the
cluster.
 In heavy traffic zones cells are smaller, while in
isolated zones cells are larger.
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11. Network cells
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12. Types of cells
 Macro cell – their coverage is large used in
remote areas, high-power transmitters
and receivers are used
 Micro cell – their coverage is small (half a
mile in diameter) and are used in urban
zones; low-powered transmitters and
receivers are used to avoid interference
with cells in another clusters
 Pico cell – covers areas such as building or
a tunnel
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13. Other cellular concepts
 Handover = moving a call from one zone
(from the transmitter-receiver from one
zone) to another zone due to subscriber’s
mobility
 Roaming = allowing the subscriber to
send/receive calls outside the service
provider’s coverage area
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14. The control channel
 This channel is used by a cellular phone to
indicate its presence before a
frequency/time slot/code is allocated to
him
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15. Cellular services
 voice communication
 Short Messaging Service (SMS)
 Multimedia Messaging Service (MMS)
 Global Positioning System (GPS)
 Wireless Application Protocol (WAP) – to
access the Internet
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16. Components of a cellular phone
(MSU – Mobile Subscriber Unit)
 Radio transceiver – low power radio
transmitter and receiver
 Antenna, usually located inside the phone
 Control circuitry – formats the data sent to
and from the BTS; controls signal
transmission and reception
 man-machine interface – consists from a
keypad and a display; is managed by the
control circuitry
 Subscriber Identity Module (SIM) –
integrated circuit card that stores the
identity information of subscriber
 Battery, usually Li-ion, the power unit of
the phone.
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17. Multiple access schemes
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Frequency Division Multiple
Access
- when the subscriber enters
another cell a unique frequency is
assigned to him; used in analog
systems
Time Division Multiple Access
- each subscriber is assigned a time
slot to send/receive a data burst; is
used in digital systems
Code Division Multiple Access
- each subscriber is assigned a
code which is used to multiply the
signal sent or received by the
subscriber

18. Global System for Mobile
Communication (GSM)
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GSM (Global System for Mobile communications)
is an open, digital cellular technology used for
transmitting mobile voice and data services.

19. Cellular network
components
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20. GSM system architecture
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21.  The base station sub system(BSS) is the
section of a GSM network which is
responsible for handling the traffic and
signaling between a mobile phone and a
network Switching sub system
 The BSS carries out allocation of radio
channels to mobile Phone paging quality
management of transmissions and
Receptions over the air interface
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Base station sub system

22.  The BSS consist of following elements one or more
BTS (base transceiver station)in one BSC(base station
controller)
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Base station sub system

23.  The base transceiver station or BTS contains
the equipment for transmission and receiving
of radio signals Transceiver antennas and
equipment for encrypting and decrypting
communications with the base station
controller BSC
 BTS is a plan transceiver which receive
information from the MS (mobile
station)through the air interface and send it
towards the BSC
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Base transceiver station

24.  BSC has 10s or even 100s of BTS under its control.
The BSC handles allocation of radio channels
receive measurements from the mobile phone BTS to
BTS and BTS to BSC
 A key function of the BSC is connection towards the
Mobile switching center (MSC) overall this means
that networks are often structured to have many BSC
distributed into regions near there BTS which are
then connected to large centralized MSC sites
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Base station controller

25.  The mobile switching center or MSC is a sophisticated
Telephone exchange which provide circuit switching
calling ,mobility management and GSM services to the
mobile phones roaming within the area that is serves
That means voice data and fax services as well as SMS
And call divert
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Mobile switching center

26. home location register
 The home location register or HLR is a central database
has contains the details of each phone subscriber that is
authorized to use the GSM core network.
 There is one HLR in one public land mobile network ,HLR
is a single database but can be maintained as separate
database when the data to be stored is more then
capacity.
 HLR stores details of every SIM card issued by the mobile
phone operator
 Each SIM has a unique identity ,IMSI (International
Mobile Subscriber Identity)which is one of the primary
key to each HLR
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27.  The VLR is a database contains temporary information
about subscribers that is needed by the MSC in order
to service visiting subscribers.
 The VLR is always integrated with the MSC when a
mobile stations roams into a new MSC area the VLR
connected to the MSC will request data about the
mobile station from HLR later if mobile station makes
a call the VLR have the information needed for call
setup without having to interrogate the HLR each time
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VISITOR LOCATION REGISTER

28. AUTHENTICATION CENTER(AUC)
 A unit call AUC provide authentication and encryption
and encryption parameters that verify the user
identity and ensure the confidentiality of each call.
 The AUC protected network operator from
different type of fraud found in Today’s cellular
world.
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29. EQUIPEMENT IDENTITY REGISTER
 The EIR is a database that contains information
about the identity of mobile equipment that
prevents calls from stolen, unauthorized
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30. GSM Call Processing
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31. Initializing a call
1. when the cell phone is turned on it scans all
the available frequencies for the control
channel
2. All the BTS in the area transmit the FCCH, SCH
and BCCH that contain the BTS identification
and location
3. Out of available beacon frequencies from the
neighboring BTSs, the cell phone chooses the
strongest signal
4. Based on the FCCH of the strongest signal, the
cell phone tunes itself to the frequency of
the network
5. The phone send a registration request to the
BTS
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6. The BTS sends this registration request to
the MSC via the BSC
7. The MSC queries the AUC and EIR
databases and based on the reply it
authenticates the cell phone
8. The MSC also queries the HLR and VLR
databases to check whether the cell is in its
home area or outside
9. If the cell phone is in its home area the MSC
gets all the necessary information from the
HLR if it is not in its home area, the VLR
gets the information from the corresponding
HLR via MSCs then the cell phone is ready
to receive or make calls.

33. Initializing a call
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34. Making a call
1. when the phone needs to make a call it sends an access
request (containing phone identification, number) using
RACH to the BTS; if another cell phone tries to send an
access request at the same time the messages might get
corrupted, in this case both cell phones wait a random time
interval before trying to send again
2. then the BTS authenticates the cell phone and sends an
acknowledgement to the cell phone
3. the BTS assigns a specific voice channel and time slot to the
cell phone and transmits the cell phone request to the MSC
via BSC
4. the MSC queries HLR and VLR and based on the information
obtained it routes the call to the receiver’s BSC and BTS
5. the cell phone uses the voice channel and time slot assigned
to it by the BTS to communicate with the receiver
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35. Making a call
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36. Receiving a call
1. When a request to deliver a call is made in the network,
the MSC or the receiver’s home area queries the HLR; if
the cell phone is located in its home area the call is
transferred to the receiver; if the cell phone is located
outside its home area, the HLR maintains a record of the
VLR attached to the cell phone
2. Based on this record, the MSC notes the location of the
VLR and indicated the corresponding BSC about the
incoming call
3. The BSC routes the call to the particular BTS which uses
the paging channel to alert the phone
4. The receiver cell phone monitors the paging channel
periodically and once it receives the call alert from the
BTS it responds to the BTS
5. The BTS communicates a channel and a time slot for the
cell phone to communicate now the call is established36

37. Receiving a call
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38. GSM Security
 Personal Identification Number (PIN)
 User Authentication
 TMSI-based Security
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39. Personal Identification Number
(PIN)
 The PIN is stored on the SIM card of the cell phone
 When the cell phone is turned on, the SIM checks
the PIN; in case of 3 consecutive faulty PIN inputs
a PUK (Personal Unblocking Key) is asked for in
case of 10 faulty PUK inputs, the SIM is locked and
the subscriber must ask a new SIM.
 This security measure is within the cell phone and
the service provider is not involved.
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40. User Authentication
 A mechanism for encrypting messages in a GSM
network
 The network sends random data to the cell phone
(RAND)
 Each cell phone is allocated a secret key (KI)
 Using RAND and KI and the A3 encryption algorithm the
cell phone generates a signed result (SRES) which is
then sent to the network
 A similar process takes place in the network which
generates a signed result specific to the cell phone
 The network compares its SRES with the SRES
generated by the phone and in case of a match the
cell phone is connected to the network
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41. TMSI-Key Based Security
 Is most used in a GSM cellular network
 A TMSI key provides a temporary identification
to a cell phone and is provided by the network
upon authentication
 A TMSI key keeps changing according to the
location of the cell phone this way preventing
unauthorized access to a channel and
preventing intruder from tracing location
 The mapping between IMSI and TMSI keys is
handled by the VLR
 ISMI are used only when the SIM is used for the
first time 41

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