Broadband Communication System

7/26/2019 Broadband Communication System

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BROADBAND

COMMUNICATION SYSTEM

Reporter:Cleider Rey B. Mujeres


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COMMUNICATION


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WHAT IS BROADBAND COMMUNICATION

The broadband communication works on theprinciple of wide band frequencies ,itoffers much greater bandwidth than theolder narrow band technologies.

Broadband refers to a signaling wide bandof frequencies, which be divide intochannels of frequency bins.


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Does !i"!er #$%d&idt! "i'e you ($ster speed

Imagine that you're driving on a road with 4

lanes in a car that can go at a maimum of!""km#hr. $o matter the amount of lanes on theroad, your car can only go at a maimum of!""km#hr and no faster. %owever, this same roadwith four lanes comes in handy when your familymembers having their own cars share the sameroad and reach the same destination at ashorter time as opposed to having a single laneroad where they will have to queue up. &ikewise

for our broadband service, with a higherbandwidth you can actually do more at the sametime or share the connection with your familymembers using a bigger pipe.


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Mutiple)i%"

- Frequency-division Multiplex

- Time-division MulitplexS!ort*$%d Mediu+*H$ul Syste+

- Coaxial Cables- Fiber Optic Links

- Microwave Links- Tropospheric Scatter Links

,o%"*H$ul Syste+- Submarine Cables

- Satellite Communications


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WHAT IS BROADBAND COMMUNICATION

The broadband communication works on theprinciple of wide band frequencies ,itoffers much greater bandwidth than theolder narrow band technologies.

Broadband refers to a signaling wide bandof frequencies, which be divide intochannels of frequency bins.


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Multiple)i%"

Multiplexin is the set o! techniques that allowsthe simultaneous transmission o! multiplesinals across a sinle data link"

# Multiple)er$M%&' is a device that combinesseveral sinals into a sinle sinal"

# De+ultiple)er$()M%&' is a device thatper!orms the inverse operation"


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C$te"ories o(Multiple)i%"


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-reue%/y*di'isio% Multiple)i%"

0-DM1 F(M is an analo technique that can be applied when

the bandwidth o! a link is reater than the combinedbandwidths o! the sinals to be transmitted"


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-reue%/y*di'isio%

Multiple)i%" 0-DM1 *n F(M sinalsenerated by eachdevice modulatedi+erent carrier

!requencies" Thesemodulated sinalsare combined into asinle compositesinal that can be

transported by thelink"

FDM is an analog multiplexing technique

that combines signals.


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-reue%/y*di'isio% Multiple)i%" 0-DM1

*n F(M sinals enerated by each devicemodulate di+erent carrier !requencies" Thesemodulated sinals are combined into a sinlecomposite sinal that can be transported by

the link" Carrier !requencies are separated by enouh

bandwidth to accommodate the modulatedsinal"

These bandwidth ranes arte the channelsthrouh which various sinals travel"

Channels must separated by strips o! unusedbandwidth $uard bands' to prevent sinal

overlappin"


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-reue%/y*di'isio% Multiple)i%" 0-DM1

*n F(M, sinals are modulated onto separatecarrier !requencies usin either #M or FMmodulation"


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Ti+e*di'isio% Multiple)i%"

0TDM1 Time-division multiplexin $T(M' is a diital process

that can be applied when the data rate capacity o!the transmission medium is reater than the data

rate required by the sendin and receivin devices"


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TDM

TDM is a digital multiplexing technique to

combine data.


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Ti+e*di'isio% Multiple)i%" 0TDM1

T(M can be implemented in two wayssynchronous T(M and asynchronous T(M"

*n synchronous time-division multiplexin, theterm synchronous means that the multiplexerallocates exactly the same time slot to eachdevice at all times, whether or not a device hasanythin to transmit"

Frames

Time slots are rouped into !rames" # !rameconsists o! a one complete cycle o! time slots,includin one or more slots dedicated to eachsendin device"


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Interleaving


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Asy%/!ro%ous TDM Synchronous T(M does not uarantee that the !ull

capacity o! a link is used" .ecause the time slotsare

preassined and /xed, whenever a connected deviceis not transmittin, the correspondin slot isempty"

#synchronous time-division multiplexin, orstatistical time-division multiplexin, is desinedto avoid this type o! waste"

Like synchronous T(M, asynchronous T(M allows

a number o! lower-speed input lines to bemultiplexed to a sinle hiher-speed line" 0owever,in asynchronous T(M the total speed o! the input

lines can be reater than the capacity o! the link"


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Asy%/!ro%ous TDM

#ddressin and Overhead

*n asynchronous T(M each time slot must carryan address tellin the demultiplexer how directthe data" This address, !or local use only, isattached by the multiplexer and discarded bythe demultiplexer once it has been read"

#synchronous T(M is e1cient only when the

si2e o! the time slots kept relatively lare"


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S!ort*2 Mediu+*H$ul Syste+

To provide the required number o! telephone andother channels in national trunk routes, broadbandsystem are universally employed consistin o!

coaxial cables

/ber-optic cables

microwave links

domestic satellites or occasionally tropospheric scatter

links"


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Co$)i$l C$#le

Co$)i$l /$#leis a type o! /$#lethat hasan inner conductor surrounded by atubular insulatin layer, surrounded by a

tubular conductin shield" Many /o$)i$l/$#lesalso have an insulatin outersheath or 4acket"


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Ad'$%t$"es

Su1cient !requency rane to support multiplechannel, which allows !or much reaterthrouhput $ .andwidth up to 5 iahert2, insome cases'"

Lower error rates" because the inner conductor isin a Faraday shield, noise immunity is improved,and coax has a lower error rates and there!oreslihtly better per!ormance than twisted pair"

6reater spacin between ampli/ers coax7s cableshieldin reduces noise and crosstalk, whichmeans ampli/ers can be spaced !arther apartthan with twisted pair"


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Dis$d'$%t$"e

More expensive to install compare to twistedpair cable"

The thicker the cable, the more di1cult to workwith"


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-i#er Opti/s

T!e +ediu+ o( tr$%s+issio% is li"!t. ,i"!t&$'es !$'e $% e)tre+ely !i"! (reue%/y$%d tr$'el $t 4567888*+iles 09887888+1per se/o%d.

A si%"le O- /$#le /$% t!eoreti/$lly /$rrytrillio%s o( #its o( i%(or+$tio% e'ery se/o%d$(ata rates up to 48 ;#pswith a bandwidth

o!


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Co+p$red to $ /o$)i$l /$#le7 opti/$l>#er !$s te% $d'$%t$"es:

Much greater capacity. Low and very uniform attenuation (signal

loss) over a wide frequency range. T!is"re$tly si+pli>es $+pli>/$tio% o( t!e

si"%$l. Virtual immunity to all types of

interference No problems with leakageor causing

interference with other signals Insensitivity to temperature variations !tremely small si"e


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#ill not short out in bad weather or evenin water

Low cost

$igh reliability T!e >#ers do %ot /orrode or#re$? do&% i% +oisture or s$lt $ir t!e &$y/opper &ires do.

Light weightSi%/e t!ey $re %ot #$sed o%+et$l /o%du/tors7 O- /$#les $re li"!ter$%d +u/! e$sier to tr$%sport $%d i%st$ll.


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Mi/ro&$'e ,i%?s

# microwave link is a communicationssystem that uses a beam o! radiowaves in the microwave !requency rane

to transmit in!ormation between two/xed locations on the earth"


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Mi/ro&$'e Ad'$%t$"es $%dDis$d'$%t$"es

#dvantaes 8o cables needed

Multiple channels available

9ide bandwidth $!requencies o! rouhly

5": iahert2 $602' to ;:: 602"'

(isadvantaes Line-o!-siht will be disrupted i! any obstacle, such as

new buildins, are in the way Sinal absorption by the atmosphere" Microwaves

su+er !rom attenuation due to atmospheric conditions"

Towers are expensive to build


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Troposp!eri/ S/$tter ,i%?s

*s a method o! communicatin with microwaveradio sinals over considerable distances < o!tenup to ;:: km, and !urther dependin on terrainand climate !actors"

8ormally, sinals in the microwave !requency

rane travel in straiht lines, and so are limitedto line of sightapplications, in which thereceiver can be 7seen7 by the transmitter" Socommunication distances are limited by

the visual hori2on to around ;:


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,o%"*H$ul Syste+

Lon-haul communications are characteri2edby a hiher level o! users, more riorousper!ormance requirements, loner distancesbetween users, includin world widedistances, hiher tra1c volumes anddensities, larer switches and trunk crosssections, and /xed and recoverable assets"


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Su#+$ri%e C$#le

# submarine communications cable isa cable laid on the sea bed between land-based stations to carry

telecommunication sinals acrossstretches o! ocean"The/rst submarine communications cables,

laid in the 5>?:s, carried teleraphytra1c"


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Su#+$ri%e C$#le

These cables are 4ust three inches thick,carry 4ust a !ew optic /bers, and have totalcapacities o! between =:6bps and 5:Tbps,and latencies that are close to the speed o!liht and 4ust a !ew milliseconds in duration"


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-$/ts A#out t!e I%ter%et@sU%derse$ C$#les

Cable installation is slow, tedious,expensive work"

Sharks are tryin to eat the internet"

The internet is as vulnerable underwateras it is underround"

Spies love underwater cables"

Submarine communication cables are!aster and cheaper than satellites


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The ood news is that it@s hard to cutthrouh a submarine communicationscable

The bad news is that it ispossible, asseen in )ypt in A:5;"

The internet@s undersea backbone is builtto last !or A? years"

%nderwater cables are not easy to repair"


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I%ter%$tio%$l Su#+$ri%e C$#le Net&or?


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=:

9ireless 9#8s Satellite 8etworks

Copyright The McGraw-Hill Companies, Inc. Permission required or reproduction or display.


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=5

.rie! history o! satellite communication

N$+e D$te o(l$u%/!

%ote

SB%T8* * October =,5D?E

the world7s /rst orbital spacecra!t" 8ov 5D?E,Sputnik A and a do escape earth and enterouterspace

SCO) (ecember 5>,5D?>

The /rst communication satellite whichbroadcasted a Christmas messae !or 5A daysuntil the batteries !ailed

)cho 5 #uust 5A,5DG:

a passive reHector satellite, the technoloy wassoon abandoned

#pril 5A, 5DG5 First man in space

Telstar 5DGA First telecommunication satellite, /rst real-time

active*ntelsat 5DG=-5DED eosynchronous earth orbit ,open to use by all

nations

*nmarsat 5DED used in international shippin

#CTS 5DD; spot beams, on-board storae and processin, andall diital transmission

(irecTI 5DD= beins (irect .roadcast to 0ome


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=A

16-2 SATELLITE NETWORKS

! satellite networ" is a com#ination o nodes, some o

which are satellites, that pro$ides communication rom one

point on the %arth to another. ! node in the networ" can #e

a satellite, an %arth station, or an end-user terminal ortelephone.


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=;

&igure Satellite orbits


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==

Ta#le ' Satellite frequency bands

Example !"


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=?

What is the period of the Moon, according to Keplers law?

#ere $ is a constant approximately equal to %&&" 'he

period is in seconds and the distance in (ilometers" 'heMoon is located approximately )*+,&&& (m aboe the

Earth" 'he radius of the Earth is !)-* (m" .pplying the

formula, we get"

Example !"0


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=G

.ccording to Keplers law, what is the period of a satellite

that is located at an orbit approximately )/,-*! (m aboethe Earth?

Solution

'his means that a satellite located at )/,-*! (m has a

period of 0+ h, which is the same as the rotation period ofthe Earth" . satellite li(e this is said to be stationary to the

Earth" 'he orbit, as we will see, is called ageosynchronous

orbit"


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5G"=E

&igure '(.') Satellite categories

Low )arth Orbit $L)O'

Medium )arth Orbit $M)O'

6eosynchronous Orbit $6)O'

GEO:EXACTLY

22 238 miles

MEO: typically around 8000 miles

HEO:var.

LEO: typically between 00 and !000 miles


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=>

&igure '(.'* Satellite orbit altitudes

G h + #i G +


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Geosynchronous +r#it G%+

atellite ystems.dantages1

lare area coverae, stay where they are at ;?,E>Gkm$AA,:::miles' above the )arth

satellite rotation is synchronous to earth three satellites can cover the whole lobe

low system complexity

isadantages1

lon propaation delay $J5A? msec' hih transmission power is required


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?:

&igure '(.'( Satellites in geostationary orbit


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Medium %arth +r#it M%+ atellite

ystems.dantages1

slihtly loner propaation delays $J=: msec' slihtly hiher transmission power required more expensive than L)Os but cheaper than 6)Os

2isadantages1

coverae spot reater than a L)O, but still less than a 6)O still the need to be in rotation to preserve their low altitude G->

hours to circle the earth" multiple M)O satellites are still needed to cover a reion

continuously handovers and satellite trackin are still needed, hence, hih

complexity

;lo#$l ositio% Syste+


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5G"?A

;lo#$l ositio% Syste+0;S16BS pro4ect was started !rom 5DE; by the %S (epartment o! (e!ence

Orbitin at an altitude about 5>,:::km Consists o! A= satellites in G orbitsK ;A by une

A:5= #t any time, =satellites are visible !rom any

point on )arthThe 6BS system concept is based on time

The satellites carry very stable atomic clocksthat are synchroni2ed to each other and toround clocks"

# 6BS receiver monitors multiple satellites andsolves e uations to determine the exact


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?;

*! we now our distance !rom three points, weknow exactly where we are" $three circlesmeet at one sinal point'


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Appli/$tio% o( ;S

?=

Military !orces

8aviation Clock synchroni2ation, C(M#

cellular system

/ % th + #it /%+ t llit


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/ow %arth +r#it /%+ atellite

ystems

.dantages1 short propaation delays $5:-5? msec' low transmission power required low price !or satellite and equipment

isadantages1 small coverae spot they have to be in rotation to preserve their low altitude $D: mins

period' a network o! at least G L)O satellites is required to cover a reion

continuously hih system complexity due the need !or handovers and satellite

trackin


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Low Earth Orbit (LEO) Satellite Systems

5G"?G

L)O satellites have polar orbits

#ltitude is between ?::-A::: km otation period o! D:-5A: min" #n L)O system has a cellular type o! access Footprint has a diameter o! >::: km" (elay N A: ms, accept !or telephony 9ork toether as a network, connected throuh intersatellite

links $*SLs'


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?E

&igure 3E4 satellite system


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?>

Little L)O, under 5602, !or low daterate messae"

.i L)O between 5-; 602, 6lobalstarand *ridium system"

.roadband L)O providecommunication similar to /bre opticnetwork"

T!ree /$te"ories o( ,EO


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(ownlink%plin

k


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e%dless lo'e
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