Download - 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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