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MobileCommunications
Lecture 1
Introduction & Background
Government College University Faisalabad Pakistan
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Why Mobile Communication?
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Challenges of mobility
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A little history and evolution
of mobile radio
1897:Marconi invented wireless concept
1960s & 1970s:
Bell laboratories developed the cellularconcept
1970s:
Development of highly reliable, miniaturesolid state radio frequency hardware
Wireless communication era was born in1970.
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Historical Background
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The current status of Wireless Communication
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Institute of Space Technology 11
Examples of Mobile Radio
Communication Systems
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Examples of Wireless
Communication Systems
MobileDescribes any radio terminal attached to a
high speed mobile platform (e.g., A cellular phone in a
fast moving vehicle).
PortableDescribes a radio terminal that can behand-held and used by someone at walking speed
(e.g., cordless telephone).
SubscriberMobile or portable user.
Subscribers Uniteach users communication device. Base stationsLink mobiles through a backbone
network.
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Full DuplexAllows simultaneous
two-way radio transmission and reception
between subscriber and base station.
Two simultaneous but separate channels
(FDD) or
Two adjacent timeslots on a single radio
channel (TDD)
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Frequency Division Duplexing
(FDD)
Provides simultaneous radio transmission channels forsubscriber and base station
Separate transmit and receive antennas at base station used toaccommodate two separate channels
Single antenna at subscriber unit with duplexeris used. Duplexer enables same antenna to be used for simultaneous
transmission and reception
A pair of simplex channels with a fixed and known frequencyseparation is used
Forward channel: used to convey traffic to mobile user from basestation
Reverse channel: used to carry traffic from mobile user to basestation
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Time Division Duplexing (TDD)
Share a single radio channel in time i.e., some
portion of time for transmission and remaining time
for reception
Can store information bursts and appear as fullduplex if users transmission rate is slower than that
of channel.
Only possible with digital transmission formats and
digital modulation and is very sensitive to timing.
Used only for indoors and small area wireless
applications
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Paging Systems Paging systems are communication systems that send
brief messages to a subscriber
Depending on the type of service the message may be: Numeric messages
Alpha-numeric message Voice message
News headlines
Stock quotes
Faxes
Coverage area of simple paging systems: 2 to 5 km orwithin individual buildings
Wide area paging systems can provide worldwidecoverage
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Wide area paging systems consists of a
network of telephone lines, many base
station transmitters, and large radio towers
that simultaneously broadcast a page fromeach base station - Simulcasting
Designed to provide reliable communication
to subscriber wherever they are. This requires large transmitter powers & low
data rates for maximum coverage.
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Wide Area Paging System
Satellite link
Landline link
Landline link
City 1:Pagingterminal
City 2:
Pagingterminal
City N:Paging
terminal
Paging
controlcenter
PSTN
Figure 1.3 A wide area paging system. The paging control center dispatches pages received from the PSTN throughout
several cities at the same time
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Cordless Telephone Systems
Full duplex communication
Uses radio to connect a portable handset to a
dedicated BS
which is then connected to a dedicated
telephone line with a specific telephone
number on PSTN
Limited range and mobility: few hundred
meters
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FixedPort
(BaseStation)
wirelesslink
PublicSwitchedTelephoneNetwork(PSTN)
cordlesshandset
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A Typical Cellular System
Provides wireless connection to PSTN for any user
location within the range of the system.
Accommodate large number of users over a large
geographic area within a limited frequency spectrum Coverage area divided into cells for same radio
channels to be reused by another base station
located some distance away
Handoff: enables a call to proceed uninterrupted
when the user moves from one cell to another
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Mobile Switching Center (MSC): responsible
for connecting all mobiles to the PSTN
Mobile station: contains a transceiver, an
antenna & control circuitry
Base station: consists of several transmitters
and receivers. Serves as a bridge between
mobile users in a cell and connects mobilecalls to MSC
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Forward voice channels (FVC): for voice
transmission from the base station to the
mobiles
Reverse voice channels (RVC): for voice
transmission from the mobiles to the base
station
Two channels responsible for initiating mobilecalls are forward control channel (FCC) and
reverse control channel (RCC)
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Wireless networks in
comparison to fixed networks