ce 450 spring 09 lec1
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Lecture 1
Introduction & Background
Government College University Faisalabad 1
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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
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Figure 1.1 The growth of mobile telephony as compared with other popular inventions of the 20th century.
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Mobile Describes any radio terminal attached to a high
speed mobile platform (e.g., A cellular phone in a fast
moving vehicle).
Portable Describes a radio terminal that can be hand-held and used by someone at walking speed (e.g., cordless
telephone).
Subscriber Mobile or portable user.
Subscribers Unit each users communication device. Base stations Link mobiles through a backbone network.
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Simplex Communication is possible only in onedirection, (e.g., paging systems, CB radio etc).
Half Duplex Two way communication, but usesthe same radio channel for both transmission andreception.User can only transmit or receive information
(e.g., push-to-talk, release-to-listen etc)
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Full Duplex Allows 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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Provides simultaneous radio transmission channels for subscriber andbase 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 frequency
separation is used Forward channel: used to convey traffic to mobile user from base
station Reverse channel: used to carry traffic from mobile user to base
station
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Share a single radio channel in time i.e., some portion oftime for transmission and remaining time for reception
Can store information bursts and appear as full duplex ifusers transmission rate is slower than that of channel.
Only possible with digital transmission formats anddigital modulation and is very sensitive to timing.
Used only for indoors and small area wireless
applications
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Paging systems are communication systems that send briefmessages 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 or withinindividual buildings
Wide area paging systems can provide worldwide coverage
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Wide area paging systems consists of a
network of telephone lines, many base
station transmitters, and large radio towersthat simultaneously broadcast a page from
each 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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Satellite linkSatellite linkSatellite linkSatellite link
Landline linkLandline linkLandline linkLandline link
Landline linkLandline linkLandline linkLandline link
City 1:City 1:PagingPagingterminalterminal
City 1:City 1:PagingPagingterminalterminal
City 2:City 2:
PagingPagingterminalterminal
City 2:City 2:
PagingPagingterminalterminal
City N:City N:PagingPaging
terminalterminal
City N:City N:PagingPaging
terminalterminal
PagingPagingcontrolcontrolcentercenterPagingPagingcontrolcontrolcentercenter
PSTNPSTNPSTNPSTN
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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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 telephonenumber on PSTN
Limited range and mobility: few hundredmeters
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FixedFixedPortPort
(Base(BaseStation)Station)
FixedFixedPortPort
(Base(BaseStation)Station)
wirelesswireless
linklink
wirelesswireless
linklinkPublicPublicSwitchedSwitchedTelephoneTelephoneNetworkNetwork(PSTN)(PSTN)
PublicPublicSwitchedSwitchedTelephoneTelephoneNetworkNetwork(PSTN)(PSTN)
cordlesscordlesshandsethandsetcordlesscordlesshandsethandset
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Provides wireless connection to PSTN for any userlocation 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 somedistance away
Handoff: enables a call to proceed uninterrupted whenthe 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, anantenna & control circuitry
Base station: consists of several transmittersand 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 basestation
Two channels responsible for initiatingmobile calls are forward control channel
(FCC) and reverse control channel (RCC)
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