Lec1 Mobile Communication

8/13/2019 Lec1 Mobile Communication

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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

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