Presentation Mobile & Communication

7/30/2019 Presentation Mobile & Communication

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BRANCH: E.C.E.(ELECTRONICS & COMM. ENGG.)

SECTION: A

ROLL NO: 247UNIV. ROLL NO: 7270407414

COLLEGE:G.G.S.C.E.T.,TALWANDI SABO

BATHINDA(PUNJAB)


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Mobile communication

RF planning, map info

Transmission

OMCRSwitching center


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TYPES OF COMMUNICATION

SIMPLEXER:

Simplexer is a type of

communication in

which informationflows in one direction

only from transmitter

to receiver .example:

radio


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Half duplexer

In half duplexer communication is

bidirectional but transmission and

reception takes place through different

communication channels. Eg . Wirelesscommunication


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Full duplexer

Full duplexer : In full duplexer,

communication is bidirectional but it takes

place through the same channel. Eg.

mobile phone


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Relation between frequency and

distance

F 1/d

So if frequency is more distance is less it

means we have to build more cell sites

and vice versa


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Some abbreviations

BSC: Base Station Controller

BTS: Base Transceiver Station

MSC: Mobile Switching Center


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Mobile station

Mobile station includes mobile equipment

and subscriber identity module SIM SIM

stores all information of subscriber


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BTS

BTS facilitates communication between

User equipment and network.
http://en.wikipedia.org/wiki/File:BTS_Vodafone.jpg


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BSC

The BSC handles allocation of radio

channels, receives measurements from

the mobile phones, and controls

handovers from BTS to BTS


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MSC

The mobile switching center(MSC) is

the primary service delivery node for

GSM/CDMA, responsible for routing voice

calls and SMS as well as other services(such as conference calls, FAX and circuit

switched data).


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Mobile call

Call from mobile travels in the following

manner:


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Communication channels

Communication channels are of 2 types:

Forward link channel: It helps in

communication from mobile phone to BTS

Reverse link channel: It helps in

communication from BTS to mobile phone


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Forward link channel

It is further of four types:

Pilot channel helps in accessing the

network, call control, call transfer


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Synchronous channel

Sync channel identifies BTS

Transfers call to BSC


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Paging channel

Paging channel transfers text, picture and

data

Traffic channel

Traffic channel as the name suggests it

allows the call traffic to pass


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Reverse link channels

Access channel facilitates call transfer

Traffic channel allows call traffic to pass


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Uplink and downlink frequency

When call is traveling from mobile to BTS

the frequency is called uplink frequency

When call is traveling from BTS to mobile

the frequency of communication is called

downlink frequency

Uplink frequency(890-915 MHz)

Downlink frequency(935-960 MHz)


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Handoff

When we are traveling from one cell site to

another we are leaving the coverage area

of one site and entering the coverage area

of other our call will get disconnected butin a millisecond it is connected to next cell

site and we do not come to know. This is

called handoff


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Handoff types

Soft handoff : Make before break (CDMA)

Hard handoff: Break before make (GSM)


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Inter cell handoff

Handoff while leaving one cell site and

entering other is called inter cell handoff


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Intra cell handoff

One cell site is divided into three sectors

when we leave one sector and enter

another the handoff is called intra cell

handoff


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VLR

Visitor location register gives information

about subscriber in a particular MSC


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HLR

Home location register gives information

about all the subscribers


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Grade of service

Percentage of subscribers dissatisfied with

our service determine the grade of service

We should listen to customer complaints

very carefully and solve their problems to

achieve best grade of service


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Fading of signal

In wireless communication, fading is

deviation of the attenuation that a carrier-

modulated telecommunication signal

experiences over certain propagationmedia. The fading may vary with time,

geographical position and/or radio

frequency


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http://en.wikipedia.org/wiki/File:Rayleigh_fading_doppler_100Hz.svg


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Reducing signal fading

In order to reduce signal fading, repeaters

are used where signal strength is weak

repeaters regenerate the signal

Also diversity receivers are used at

receiver end which increase signal

strength


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GPS

GPS stands for Global Positioning System

Arrangement of cell sites is shown in

figure

Neighbouring channels are called adjacent

channels (A,B,C,D,E,F,G)

Channels operating at same frequency are

called co channels (A,A)


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Interference

Super positioning of two signals is called

interference

Adjacent channel interference can be

reduced by keeping 5 or 8 difference in

frequencies of adjacent channels

Co channel interference can be reduced

by maintaining distance between cochannels


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Differences between GSM and

CDMA

GSM

Different frequency

for every user

Hard handoff

CDMA

Same frequency for

every user

Soft handoff


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Antenna height

Antenna angle is 30 for highways

Antenna angle is 65 for city

Antenna angle is 90 for village


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Antenna angle


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Cell splitting

When traffic density starts to build up and

frequency channels in each cell cannot

provide enough mobile calls original cell

can be split into smaller cells

Two types of splitting:

Original cell is not used

Original cell is used


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Original cell not used


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Original cell is used


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Multiple access techniques

FDMA (frequency division multiple access

): frequency slots are assigned to user as

long as the call continues

TDMA (time division multiple access):

time slots are assigned to user as long as

the call continues


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Frequency slots


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Time slots


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Switching

It makes connection between desired inlet

to desired outlet


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Drive testing

Rx level voice clarity

Level 5:excellent

Level 4:good

Level 3:fair

Level 2:very poor

Level 1: unsatisfactory


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Voice clarity


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Coverage

Documents

Presentation Mobile & Communication