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CEENET Workshop 2001
Satellite communications
Krzysztof Muchorowski
NetSat Express
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Introductory remarks
The purpose of this lecture is to give you a very general
overview of satellite communication, it is not meant to be acomplete description of the world of satellite
communication
I will often mention applications and business services
I will try not to deviate from the main course, but pleasestop me if I do.
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A few reasons of satellite revolution:
A single satellite can provide coverage to over 30% of
Earths surface.
It is often the only solution for developing areas.
It is ideal for broadcast applications.
It can be rapidly deployed.
It is scalable.
Depending on application, there is no need for the local
loop. Transmission cost is independent on distance.
One hop from the backbone, wherever you are.
Wide bandwidths (155 Mbps) are available now.
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What is a satellite?
Isaac Newton noticed first, that if we throw an object on Earth horizontally
with big enough velocity, it will not fall down, but will circulate around Earth
indefinitely.
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R=6400 km T=84 minutes
R=7100 km T=99 minutes (LEO)
R=11400 km T=201 minutes (MEO)
R=42350 km T=24 hrs (GEO)
So, an object placed at the orbit approx. 36 000 km
above the equator will be seen at the same position in
the sky from Earth.But roundtrip time will be more than half a second!
Is this position actually stable?
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PublicPublicLibrary/SchoolLibrary/School
TelemedicineTelemedicine
DistanceDistanceLearningLearning VideoVideoConferencingConferencing
VoiceVoice
LANLANExtensionExtension
Business AccessBusiness Access
PSTN GatewayPSTN Gateway
InternetInternetBackboneBackboneAccessAccess
CollaborativeCollaborativeComputingComputing
CellularCellularBackhaulBackhaul
AviationAviation MaritimeMaritime
Corporate EnterpriseCorporate Enterprise
TerrestrialNetworks
TerrestrialNetworks
Teledesic: Internet-in-the-Sky
Teledesic P roprietary Slide 2 of 91
a few remarks about LEO and MEO satellites(Teledesic, Iridium)
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but ...
omnidirectional antenna vs directional one
what does it mean in terms of available frequency spectrum?
There are (in general) three bands of spectrum available for GEOsatellite communication: C, Ku, Ka.
C - 4-7 GHz (5 cm wavelength)
Ku - 10-14 GHz (2.3 cm wavelength)
Ka - 18-30 GHz (1 cm wavelength)
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Properties of spectrum bands
C band:
large beams
The actual footprint of Intersputnik Express 3A
little rain fade (but sand storms affect it as well!)
large antennas expensive amplifiers
lots of noise on the ground!
also circular polarization
Rx: 3625 to 4200 MHz
Tx: 5850 to 6435 MHz
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Properties of spectrum bands (contd)
Ku-band
most widely used today
smaller beams (even spot beams)
smaller antennas
stronger rain fade cheaper amplifiers
suitable for home users as well
noise on the ground is already often a problem
steerable spot beams Rx: 10.95 to 12.75 GHz
Tx: 14 to 14.5 GHz
Ka band (still at development phase)
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OK, so now lets take a look at how a satellite is built andlaunched.
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India's GSAT Hits Problems
Following its successful launch last week, ISRO's GSAT experimental satellite a series of in orbit
manoeuvres have used most, if not all, of the available fuel on the spacecraft.
Unfortunately, the GSLV launcher did not place GSAT in exactly the right orbit - the apogee achieved was32,051 km instead of the 35,975 km expected. Also, the inclination of the orbit was 19.2 instead of the
intended 19. The reason for this slight difference has not yet been determined.
It was originally believed that the intended orbit could be achieved by a series of short thruster burns
using the satellite's attitude control
thrusters at the expense of the on board fuel and hence satellite lifetime.
Unfortunately, the satellite carries two different propellant tanks, which resulted in an unequal flow of
fuel. The resulting imbalance created an impulse that made the spacecraft tilt. All the remaining fuel was
then used in order to stabilise the satellite. Two different tanks were used because they were available.
The designers were aware of the imbalance in flow rates but did not adequately compensate for its effects.
GSAT is now in a 23 hour 2 minute orbit and is reported to be out of fuel. It is not yet known what, if anyuse can be made of the spacecraft.
[press release, excerpts, April 2001]
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Ariane 5 Satellites in Wrong Orbit
Following a perfect lift off from its launch site at Kourou, French Guiana, on Thursday Ariane 5 failed to put two
comsats in the correct transfer orbit. Initial indications are that the second stage of the rocket shut down prematurely.
The two satellites were intended to be placed in a 35,853 km x 858 km transfer orbit with an inclination of 2.0. They
were actually left in a 17,528 km x 592 km orbit with an inclination of 2.9.
Early reports are that the second stage, the Astrium manufactured Storable Propellant Stage (EPS), only generated
80% of the intended thrust and cut out 80 seconds early. It should have fired for 16 minutes 20 seconds, but this
should have automatically been extended to compensate for the reduced thrust. Telemetry indicated that an anomaly
occurred three seconds after ignition. Speculation is that the problem was caused by a propellant leak. The upper stage
uses monomethyl hydrazine fuel and nitrogen tetroxide oxidiser, which are fed from pressurised tanks to a single
Aestus motor.
In spite of these problems the second stage managed to orient itself correctly and successfully deployed the two
satellites, leaving at least the possibility of recovery.
The satellites left in limbo by Ariane 510 are Artemis, an experimental European Space Agency telecommunications
satellite, and BSAT-2b, a Japanese TV broadcast satellite.
Artemis, with a price tag of US$ 850 million, is ESA's most expensive satellite ever. It may carry enough fuel to
allow it to reach geostationary orbit where it should be able to use ion propulsion thrusters for station keeping.
Japanese Broadcasting Satellite System's BSAT-2b may be a different story - it probably has enough fuel to reach
geostationary orbit, but would be left without fuel for station keeping.
This was the tenth launch of an Ariane 5 and the third failure. Ariane 4, by comparison, which is due to be replaced
by Ariane 5 in 2003 when the remaining stock of 12 launchers is used up, has had a series of 62 consecutive
successful launches.
Before Thursday's launch failure, Arianespace was expecting to have three further Ariane 5 launches and three moreAriane 4 launches before the end of the year. The next Ariane 5 was scheduled to launch Atlantic Bird 2 and Insat 3C
in September and the next Ariane 4 was to launch Intelsat 902 on 23 August.
An inquiry board has been appointed to investigate the cause of the launch failure. Preliminary conclusions are due at
the beginning of August.
[press release from July 2001]
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How much does a satellite cost?
How much does it cost to launch it?
How many transponders does it carry?
How long does it work?
What happens at the end of life?
Inclined orbit satellites.
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Business Models
GEO 15+ yrs $2B
MEO 10 yrs $2-3B
LEO 5 yrs $1.5-3B
Lease 1 yr $
Own 5-15+ yrs $$
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Does Size Matter?
Large satellite >1000kg
Medium satellite 500-1000kg
Mini satellite 100-500kg
Micro satellite 10-100kg
Nano satellite 1-10kg
Pico satellite
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Other satellite issues (to close the topic)
Rights to orbital slots, landing rights.
SATMEX PROPRIETARY INFORMATION
Canada
United States
Guatemala
Costa Rica
Peru
El Salvador
Bolivia
Uruguay
Paraguay
Brazil
Chile
Venezuela
Colombia
Ecuador
BelizeHondurasNicaragua
PanamaArgentina
Jamaica
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Other satellite issues (contd)
EIRP, G/T
Effective Isotropic Radiation Power - EIRP - often expressed in decibels
relative to 1W - dBW. Ku-band satellites typically about 50 dBW, C-band
satellites typically about 35 dbW
G/T - gain by temperature - parameter of satellite antennas and position onEarth.
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Other satellite issues (contd)
spring and autumn equinox twice a year, around March 21 and September 23, satellite, earth station
and sun are positioned along one line
C band signal are affected more than Ku band signals
Stronger carriers are obviously less affected
Smaller antennas are less affected because their beamwidth is widerrelative to the perceived radiation beamwidth of the sun (there are fewer
days of outage, with shorter durations each day).
In the Fall, the farther north from the equator the station is, the later the
effect occurs (in the Northern Hemisphere, the fall effect occurs after the
Equinox). In the Southern Hemisphere, the reverse is true; the Fall effectoccurs before the Equinox, and the further south a station is located the
earlier it occurs. Satellites in locations east of the ground station have sun
outage periods in the morning, and conversely, satellites located west of
the station experience sun outages in the afternoon.
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(contd from previous page)
No action usually required unless:
You have an antenna tracking system, which should be put instandby or manual mode.
You want to reroute traffic for the several minutes of outage eachday (worst case).
For those customers with duplex service, it is important toremember that the outage for your inbound and outboundlinks may occur at different days and at different times duringthe day.
http://www.ips.gov.au/papers/richard/calc_inter.html
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Pro-s and con-s of inclined orbit satellites
Con-s:
One probably only has about a year of service left before the
satellite finally dies.
One will suffer a large Doppler shift
One will need to add tracking to the antenna (typically +$20k for a2.4m)
Pro-s:
Price!!!
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Hardware: ground segment
Antenna
Receiving/transmitting chain
Types of connection
Link budget
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Antenna
Parabolic or offset
diameter - gain (as a function of frequency)
noise - temperature (as a function of elevation)
cross-polarisation isolation
de-icing (if required)
wind resistance
temperature variations tolerance
tracking...
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Antenna (contd)
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Antenna (contd)
Various kinds of antennas
(what if we used two to transmit)
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Antenna (contd)
Flat antennas (e.g. for Inmarsat phones)
(A short break from the main course of the lecture :)
Inmarsat M/B Global Coverage map
= Existing LES throughout the Global Map.
LES - Land Earth Station
60
180 160 140 120 100 80 60 40 20 0 20 40 60 80 100 120 140 160 180
30
0
30
60
60
30
0
30
60
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High Performance Outdoor UnitAntenna & RF
Flat panel antenna
RF Unit on rear
Single cable - no rf
All digital & DC
Self leveling tripod Fixed mount available
Audio tone for antennapointing
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Compact Indoor Unit
5 phone / fax jacks
9.6 Kb. Data
56 / 64 Kb HSD
Plug in Interfaces for
RS-232,-449, V.35,X.21, and S0 ISDN
Menu in 5 languages
Speakerphone
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Go Anywhere Package
Entire system packs ina soft carry case
Case contains:
Antenna
RF Unit
Indoor Unit
Power Unit
Cables
Manual
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Great Accessories fora Great Product
The VIDEO EXPLORER Briefcase video conferencing
TOKO BROADCAST VIDEO
Store & forward video at up to 2 Mb anywhere
STU-III Secure Phones at 9.6 Kb.
Datacom Accessories & Routers
Muxes, PBXs, Cordless Phones
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The Video ExplorerH.320 Video Conferencing in a Briefcase
2 way, live video
Camera with 12X zoom &autofocus
6 color display
supports 56-384Kb.ISDN Network
weighs approx 18 lbs.
Internal Phone
End of break - back to maincourse
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Receiving/transmitting devices
LNA (Low Noise Amplifier) orLNB (Low Noise Block)
LNA - amplifies RF signal from
the antenna and feeds it into
frequency converter (typically
IF of 70/140 MHz)
LNB - amplifies RF signal from
the antenna and converts it to an
L-band signal (950-2100 MHz)
LNA is more precise and stable
but more expensive than LNB(LO stability).
Transmit power amplifiersprovide amplification of signals
to be transmitted to the satellite
Transceiver takes 70/140 MHz
signal and amplifies it to either
C or Ku-band final frequency.
Block UpConverter takes L-
band signal and amplifies it to
either C or Ku-band final
frequency.
What is better?
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LNB properties (example)
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Ku-band transceiver (example)
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Amplifiers
How much power is necessary? Answer requires link budget
typically, a few Watts for Ku-band, a few tens of Watts for C-
band.
SSPA (Solid State Power Amplifiers) will be enough in almostevery case.
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Modems
Satellite modem: modulates input digital signal into analog signal and vice versa:
demodulates input analog signal to digital data.
Typical parameters
supported modulations FEC, Reed-Solomon
maximum speed
interfaces (on both sides)
compatibility (this you never know until you try)
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Modem parameters
Modulations/coding How many bits per symbol (cycle, 1 Hz)?
1 - BPSK
2 - QPSK
3 - 8PSK 4 - 16QAM
(cable modems have typically 64QAM or perhaps even better now)
FEC - forward error correction
QPSK 3/4, 7/8
8PSK 2/3, 5/6 16QAM 3/4, 7/8
Turbo coding
Reed-Solomon - additional performance improvement, but extra
188/204 factor
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Modem parameters (contd)
Interfaces: on IDU side:
V.35 (up to a few Mbps)
EIA-422, 449, 530 (up to 8 and 18 Mbps)
HSSI (up to 52 Mbps) G.703 (as above)
OC-3c (exactly 155.52 Mbps)
on ODU side:
70/140 MHz (to transceiver)
L-band (to BUC)
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Modem parameters (example)
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IRD instead of a modem
Integrated receiver decoder (IRD) performs same functionsas demodulator except that it typically provides as its
interfaces:
Ethernet
Video/audio outputs Audio outputs
Dont assume any compatibility between IRDs until you
experimentally verify it.
IRDs are children of DVB era, direct-to-home andbroadcast applications.
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Redundancy
What is redundancy?
When is it required?
How is it done?
What remains a single point of failure?
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Bit Error Rate
A demods BER performance is specified as a function of(signal energy per bit)-to-(noise power density per hertz)
ratio - Eb/N0
The Eb/N0 ratio is so important because the bit error rate
for digital data is a decreasing function of this ratio. To ensure that a specified BER is met, a link budget
analysis must be performed in order to ensure that the
required Eb/N0 ratio is provided to the demodulator.
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Bit Error Rate
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Link budget
Satellite transponders have two resources: bandwidth (Hz)
and power (dbW). A proportional amount of transponder
power is allocated across the transponder BW.
Power Equivalent Bandwidth (PEB) is the greater of twovariables:
allocated bandwidth (a function of the data rate, modulation/coding
scheme, carrier spacing)
allocated power (minimal power assignment which is sufficient toproduce desired Eb/N0 ratio at the demodulator in the receiving
station).
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Link budget (contd)
What is needed as an input to link budget? Satellite, its performance (EIRP, G/T)
location of both ground stations (elevation, rain zone)
data rate
required Eb/N0 ratio any other limitations (e.g. maximum antenna diameter)
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Link Budget (example)
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Link budget (contd)
Therefore, link budget calculations tell us what is theoptimum modulation/coding scheme used to maximize
bandwidth utilisation, how much power we need to
transmit certain amount of bandwidth (i.e. how powerful
BUC should we buy), how big our antenna should be etc.etc.
Example calculation of allocated bandwidth:
2 Mbps data stream, QPSK 3/4, Reed-Solomon coding, standard
carrier spacing:
BW = 2048*10^3 /2 *4/3 *204/188 *1.5 = 2.2 MHz
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Link budget (final)
Transponder efficiency usage: an example: two SCPC carriers per transponder, each receivable
with 4.5m antenna or one MCPC carrier per transponder,
receivable with 2.4m antenna.
Single/Multiple Channel Per Carrier - SCPC or MCPC
Same applies to transmitting:
if two carriers need to be transmitted through the same BUC, it is
necessary to reserve more power i.e. two carriers each requiring
2W will need at least 8W BUC if sent through the same
transmitting system. Multiplexer makes sense in such case Reed-Solomon is so useful as it allows to decrease antenna
size (Eb/N0 ratio) while still maintaining very low BER.
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Moving up one layer to layer 2...
OK, so we have a connection, both modems are locked totheir carriers, the same stream of 0s and 1s is received as
it is transmitted, what next?
Clear channel or link encapsulation:
HDLC PPP
ATM
Frame Relay
or DVB
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To DVB or not to DVB?
What is Digital Video Broadcast?
World-wide standard for transmission of digital TV via satellite (S),
cable (C) or terrestrial (T).
Utilizes MPEG-2 compression and packet standard Supports data as well as video transmissions.
Supports multiple program streams, each of which can be encrypted
Supports sub-multiplexing within a program stream
Provides for high degree of forward error correction
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DVB Delivers Multiple IP Services Over a Shared Satellite
Link
In A Shared Link:
The satellite carrier is sharedby multiple users;
User packets are interleaved;
Each site filters out its ownpackets.
There are many ways to do this,but DVB has several advantages.
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Multicast Is Expected To Be A Major Growth
Area
SOME MULTICAST APPLICATIONS
Radio & TV Networks-distribute commercials, audio & video objects to
affiliates
Financial Data Feeds
Distance learning Corporate Training Video
Catalog & Product Information Distribution
Caching Feeds for ISPs and Corporate Intranets
Remote Publishing and Printing (example!)
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Multiplexed, Multicast Technology
Needs Supported/Facilitated By DVB
High speed multiplexed (shared) satellite uplink
Secure delivery of services to entitled users
Low cost, one and two-way customer terminals
Quality of Service (QoS) management Servers to receive, store and reliably play out streaming data, and data
packages
Network management, billing, accounting, and customer support services
b Content Delivery Site hosts
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An Content Delivery Network Incorporating DVB
1 - Client requests document
The Net
Content Providers
Content Delivery
Site
Edge Site
End Site
c - Content Delivery SiteMulticasts Documents toEdge Sites and End Sites
d - Edge Sites storedocuments in ServersEdge Site
ClientLocalISP
2 - ISP requests
document fromclosest Edge
Site
3 - ES returnsdocument
4 - ISP returns document
Edge Sites (ES) include:
ISPs, Web HostFacilities, Cable Head
Ends etc.
End Sites includecorporate locations and
SOHO sites
e - End Sites storedocuments in localServers or in requestingPC
a - Content Providers send webdocuments to Content Delivery Site
b - Content Delivery Site hostsdata for eventual playout toedge and end sites
54
News Feed
Caching Feed
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A Closer Look at DVB Features
DVB uses a 188 byte packet format for transmission of all services
DVB can multiplex multiple services on the same carrier
DVB provides conditional access for security, privacy, and program selectivity
For satellites, DVB provides:
QPSK Modulation (typically)
Reed-Solomon coding
Forward error correction rates: 1/2;2/3;3/4;5/6;7/8
potential to saturate the carrier, leading to more efficient bandwidth utilization and
smaller receive antennas
avoids a very annoying problem with interface speed, encountered in SCPC links (!)
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DVB Packet Format
MPEG
184bytes
PayloadOverhead
(4 bytes)
188 bytes
IP Encapsulation
16 byte header IP Packet MPEG
Packets
Padded orpacked area
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DVB Uplink Data Flow
R
O
U
T
E
R
IP
Encapsulator
MPEG
Multiplexer
DVB
Mod.
Modulates RF
carrier; applies Reed-
Solomon coding and
FEC
Conditional
Access System
Muxes MPEG program streams;
encodes bit stream
Encapsulates IPPackets within
MPEG Transport
Stream
IP Packets
MPEG Video
Transport Stream and
other multimedia
Internet
Private
lines
Controls program
entitlements; key words
for encryption
Satellite dish
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DVB Integrated Receiver
Decoder (IRD) Structure
IRD Localrouter
LNB
demodulates transport stream
filters by PID number
provides Conditional Access processing
reassembles IP packetcould filter on IP or MAC address
Common Interface
Serial Port
100 Base T Port
Local PIDs Only
carrier with multiple streams andsubstreams
All PIDs
NOTE: IRD in this slide isdepicted as set top box:
could also be card that fits in PC
Note: IRD shown in
this slide is set top
box; could also be PC
card.
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An Example Multiplexed Carrier
PID 1 Internet Access - in the clear, submultiplexed by MAC addresses
PID 2 News feed multicast - shared by all ISPs on the carrier (encrypted)
PID 3 Caching feed for selected ISPs (encrypted)
PID 4 Intranet for Corporation A (encrypted)
PID 5 Intranet for Corporation B (encrypted) PID n Intranet for Corporation C (encrypted)
NOTE: Each PID has guaranteed bandwidth, but could burst for more, if bandwidth is
available
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Summary Of DVB Benefits
Low-cost receivers ($100-300 cards; $1000 set top boxes)
Tightly controlled filtering/encryption
Can mix services on large carriers
statistical multiplexing reduces bandwidth costs
saturated transponder operation leads to small antennas and more efficient
bandwidth utilization
Standards base encourages application and enhancement development
just please be careful with compatibility issues!
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Applications
Already mentioned Internet, this is why we are here after all!
VSAT networks: full-mesh, star topology
not-so-quite POTS: Inmarsat system
p-to-p:
voice
Internet
content delivery
broadcast: TV, digital radio
multicasting: natural advantage cache'ing: passive, active, pushing content to the edge of the
network
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Satellite Internet
It is not enough to say, that whatever comes in, comesout, so IP packets are fed from one side and leave on the
other.
There are certain specific features of satellite Internet like
dynamical bandwidth allocation which are very useful. There are also certain drawbacks of satellite Internet,
mostly due to the long propagation delay and its effect on
TCP (maximum session speed and slow start).
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Early DARPA experiment 64 kb/s links
10-3 BER
Demonstrated IP by interconnecting with ARPANET in
1977
Department of Energy:
Supercomputer star networks
UMd - SDSC
Arizona - JVNC
SATNET and MFNET (some history)
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USAN
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ACTS
NASA satellite launched 9/93, ended 6/2000 20 - 30 GHz (so it was Ka-band)
Steerable and spot beams
Up to OC-12 speeds
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Effect of propagation delay on TCP networks
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p p g y
(very pessimistic)
Geostationary satellites (GEOs) have a minimum round-trip latency (i.e., delay)of 500 msec, and take 700 msec or more with framing delays
GEO latency can significantly degrade performance on client/server applicationssuch as Oracle and Exchange Server resulting in slow downs of 10 times ormore
Small transaction-oriented queries get queued up by GEOs high delay
GEOs do not work well with fundamental Internet protocols like TCP/IP
Most implementations of TCP today provide unacceptable performance
(e.g., wasting 93% of bandwidth on a 2 Mbps connection) because theylack large window support
TCPs essential congestion control mechanisms degrade performance overGEOs. These mechanisms cannot be removed without potentially causingthe "congestive collapse" of the Internet.
One proposed solution, ACK spoofing, is incompatible with Internet Protocol
security (IPsec) and will not work at all with the next generation protocol,IPv6.
Transaction-oriented Internet protocols also suffer from GEO delays becausesignaling exchange is necessarily sequential
HTTP/1.0 and HTTP/1.1, POP3, IMAP4, NNTP
Hand-shaking portions of real-time protocols such as H.323 also suffer
Effect of propagation delay on TCP networks
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ect o p opagat o de ay o C etwo s
(more realistic)
TCP transport layer protocol guarantees delivery of data between hosts by requiring that each host
acknowledge the receipt of data from any other host. If a host sends data and does not receive an
acknowledgement from the receiving host it must retransmit the unacknowledged data. TCP will onlytransmit as much data as the receiving end can store before it must acknowledge the receipt of the
data. The amount of data that can be stored is known as the advertised Window Size. After sending
the maximum number of bytes, the transmitting end must wait for an acknowledgement before
sending more data. Here is where satellite latency becomes an issue. With a round trip satellite
latency of 500ms, no data will be sent for 500ms after the last bit of the previous message is
transmitted. Actually the satellite latency is not the only latency involved. There will typically be 100
ms or more added due to the terrestrial links between the hosts and the satellite earth stations. Thetotal latency is known as the Round Trip Propagation Delay (RTPD). The RTPD = 250 ms * 2 +
terrestrial latency. Assuming 100 ms for the terrestrial latency the RTPD = 600 ms. The maximum
throughput of a TCP connection is given as:
Maximum Throughput Rate = Advertised Window Size/ RTPD
With a 32,672-byte Advertised Window size the maximum throughput of a satellite link with a 100
ms terrestrial latency would be:
Max Throughput Rate = Window Buffer size / RTPD = 32,672 / .600
= 54,453 Bytes/Sec
= 435,627 bits/ Sec
Slow start is another problem...
Effect of propagation delay on TCP networks
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p p g y
(a bit of relief)
This effects only a single TCP session! A large number ofusers, even a single user with Web browser will have
numerous TCP sessions, each will have its limit, so
bandwidth utilisation is actually not a problem!
But it is true, that there is a number of protocols, which arevery uncomfortable with such large delay: Oracle,
Exchange, telnet, NNTP, voice
What? Did I say voice? Voice-over-IP? Has someone
rang me?
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Effect of propagation delay on TCP networks (contd)
Technical issues with Long Fat Networks - no longer just asatellite problem
Approaches include SACK (RFC 1072, 2018), TCP
spoofing, Transaction TCP (T/TCP),
and LEO
TCP/IP Accelerator
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TCP/IP Accelerator
TCP/IP spoofing improves TCP/IP throughput over satellite. Resides on a proxy server at both ends of the link.
Interfaces with the user and the host via TCP uses UDP overthe satellite. UDP does not require acknowledgements.
Large receive window Selective NAKs to provide guaranteed delivery
Data compression.
The end result is a higher speed TCP/IP connections(upto T1 rates) in high latency environments such as satellitecommunications. Results in higher speed and reducedbandwidth utilization.
This is usually a premium service. It will not work with IPv6.
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VoIP on satellite networks
Excellent application, widely used: 10 kbps per phone call instead of 64 kbps
simple setup for both termination and origination
some legal problems might be on the way
(but it may only increase possible profits :-) satellite delay is a little bit of a problem, one must get used to it.
but this satellite delay is constant so there is no jitter!
end-to-end bandwidth is fully guaranteed!
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IP Voice Network
INTERNET
Satellite
Satellite
dish
Satellite
Demod
QoS Router
Hub
Satellite
dish
Satellite
Modem
U.S.InternetCSU/DSU
HubIP Voice Serve r
U.S.
PSTN
E1/T1/ISDN
AnalogTelephone
Telephone
IP Voice Serve r
LocalInternet CSU/DSU
LocalPSTN
E1/T1/ISDN
AnalogTelephone
Telephone
RouterRouter
Mainframe Router
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IP Voice Network
Satellite
Satellite
dish
Satellite
Modem
Hub
Satellitedish
Satellite
Modem
U.S.Internet
CSU/DSU
U.S.PSTN
E1/T1/ISDN
AnalogTelephone
Telephone
Local
PSTN
E1/T1/ISDN
AnalogTelephone
Telephone
Cisco VoIPRouter
NSX RouterIP Network
Cisco VoIPRouter
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Back to satellite Internet
Types of connections: bi-directional:
symmetric
asymmetric (typically 1:4)
uni-directional (receive-only)
Routing issues:
on bi-directional links
on receive-only links;
Burstability
Bi di i l lli I i
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Bi-directional satellite Internet connections
capacity may be symmetric or asymmetric, depending on
needs, applications etc.
typically, for asymmetric setup, 1:4 of outgoing/incomingbandwidth is assumed.
one needs to assume about $10-20k for such hardware
Receive only satellite Internet connections
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Receive-only satellite Internet connections
Simple to use and set up
usually no problems with licensing
cheap hardware ($1k-$3k)
but performance is difficult to guarantee!
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Burstability
This is a unique feature of satellite networks. It works bestin case of wide C-band beams, which span several
timezones.
It allows users to get their guaranteed capacity (CIR or
CBR), but if bandwidth in carrier is available, it can beused at little or no charge.
This is often a selling point so be careful!
Surely, DVB is ideal for large, powerful carriers where
burst is likely to give you most benefit.
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Routing (if we also have 2nd connection)
BGP4 Ideal case. Works for both bi-directional and receive-only links.
Load-balancing remains an issue, but may be managed.
Static routing:
Option 1: static BGP announcement by the satellite provider (whenwe own at least a C-class), but BGP announcements must be
similar!
Option 2: Using IP addresses and cooperative upstream ISP
Option 3: Using IP addresses and non-cooperative upstream ISP
NAT and proxy (uses IP addresses from the satellite provider)
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More about routing for RO links.
Option 1: Both satellite provider and your local ISP announce your routes. Thesmallest block which can advertised to the Internet is a full Class C block.
Option 2: Satellite provider alone announces your routes. In this option you must have
addresses that no on else is advertising. Again, it must be at least Class C. With this
option, your local ISP will be seeing traffic originate from within your network that does
not have a source address that he has assigned to you. This option will require that your
local ISP pass this traffic.
Option 3: Satellite provider alone announces your routes and your local ISP is non-
cooperative and will block this traffic. Some ISPs will not allow you to obtain address
space from other sources and will block traffic that originates with a foreign source
address. The solution is to encapsulate this traffic in a GRE tunnel. Traffic will leave
your network encapsulated with a source address that your local ISP will pass. This
traffic will be de-encapsulated at satellite providers NOC and will then be forwarded to
the proper site on the Internet. This has two disadvantages. First, traffic will have totransverse the Internet twice. Traffic destined for Microsoft.com will first arrive at
satellite providers NOC and only then will it be redirected to Microsoft.com. Second,
the encapsulation /de-encapsulation process takes time and is CPU intensive as every
packet must be processed.
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What is Multicast ?
Multicast is the transmission of information (a lot of information, usually) that
should be transmitted to various (but usually not all) hosts over an internet.
One common situation in which it is used is when distributing real time audio
and video to the set of hosts which have joined a distributed conference.
Multicast is much like radio or TV in the sense that only those who have tuned
their receivers (by selecting a particular frequency they are interested on)
receive the information. That is: you hear the channel you are interested in, butnot the others.
The Problem with Unicast
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When you send a packet and there is only one sender and one recipient then
this is unicast. TCP is, by its own nature, unicast oriented.
If you are to send audio and video, which needs a huge amount of bandwidthcompared to web applications, you had, until multicast came into scene- two
options:to establish a separate unicast connection with each of the recipients,
or use broadcast.
The first solution is not affordable: if we said that a single connection sending
audio/video consumes a huge bandwidth, imagine having to establish hundreds
or, may be, thousands of those connections. Both the sending computer andyour network would collapse.
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What about Broadcast ?
Broadcast seems to be a solution, but it's not certainly the solution. If you wantall the hosts in your LAN to attend the conference, you may use broadcast.
Packets will be sent only once and every host will receive them as they are
sent to the broadcast address. The problem is that perhaps only a few of the
hosts and not all are interested in those packets. Furthermore: perhaps some
hosts are really interested in your conference, but they are outside of your
LAN, a few routers away. And you know that broadcast works fine inside aLAN, but problems arise when you want broadcast packets to be routed across
different LANs.
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Multicast the Best Solution !
The best solution seems to be one in which you send packets to a certainspecial address(like a certain frequency in radio/TV transmissions). Then, all
hosts which have decided to join the conference will be aware of packets with
that destination address, read them when they traverse the network. This is
similar to broadcasting in that you send only one broadcast packet and all the
hosts in the network recognize and read it; it differs, however, in that not all
multicast packets are read and processed, but only those that were previouslyregistered as being "of interest".
S lli i h l i i !
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Satellite is the answer to multicasting!(at least partly :-)
Leverage off of Broadcast Nature of Satellite Take advantage of Low Cost DVB Receivers, security not an issue!
IP Multicast
News - Usenet is a perfect example!
Stock Quotes, other financial data
Multimedia
Web Casting, active and passive cacheing
Distance Learning Applications
Business Applications
Pushing the content to the edge of the network.
I wanted to add a few adds about Cisco Content Delivery Networks
(CDN), but there is another talk tomorrow...
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Some advices...
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How to select a satellite Internet service provider?
Which satellite: band, footprint, elevation... require link budget. Internet is already a commodity, like water, gas, electricity (almost).
So, does it matter where it comes from?
But (local) support quality is not a commodity!
Choose inclined orbit satellites only if you know very well what you
are doing. This could be well a second or third link, should not be amain one!
Do not sign longer commitment than 12 months, unless you have to or
receive a bonus in pricing.
Look for warranty of service in the contract.
What pricing you may expect?
There are Mazdas, Porsches, Ladas, Skodas, and Daewoos. Each may carry you to
your destination.
There are no free lunches - you get (at most) what you pay for!
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How to configure a network for satellite RO service?
If you use one of SOHO offerings (like Europeonline,Demos Internet):
install Linux (if drivers for the card are available)
run either NAT or proxy for LAN
if you use a fixed capacity service offering, structure yournetwork so that all incoming/outgoing traffic is handled by
one router
access lists are easier to manage
How to point an antenna at a given satellite?
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How to point an antenna at a given satellite?
Go to www.satcodx.com and find the satellite of your choice.
Write down all analog TV stations on this satellite, see if you can findone which is in the same band range as your LNB
Use elevation calculator to find roughly position of the satellite in the
sky (e.g. http://www.comsym.com/IESS412.htm)
Pre-program TV tuner for analog TV stations and connect a TV.
Find this bird! You may want to start from another satellite, with a
stronger signal. Remember about polarisation!
If there are no analog TV stations on this satellite, find them on
adjacent one - then fine tune with your digital receiver.
When you have your antenna pointed, ground it and program your
receiver to the carriers data and see if you get a lock.
Sure, spectrum analyzer tuned to beacon frequency is much more
professional, but for RO systems this works fine as well.
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Satellite positions in the sky in Budapest
AimSat 1.1
Satellite data for: Budapest
Latitude: 4800'00" N
Longitude: 1900'00" E
Satellite Slot Azimuth Elev. Skew
-------------------------------------------------------------
Statsionsat 13 80.00 E 112.39 10.43 49.21
Gals 1/2 71.00 E 120.14 16.02 39.54
PanamSat 4 68.50 E 122.40 17.51 37.20
Intelsat 602 63.00 E 127.58 20.69 32.42
Intelsat 604 60.00 E 130.53 22.34 29.99
Intelsat 507/510 57.00 E 133.57 23.92 27.65
Statsionsat 5 54.00 E 136.70 25.43 25.41
Turksat 1B 42.00 E 150.27 30.58 17.01
Arabsat 2B 30.50 E 164.69 33.79 9.16
Kopernicus DSF2 28.50 E 167.31 34.15 7.72Arabsat 2A&3A 26.00 E 170.62 34.50 5.85
Eutelsat I F4 25.50 E 171.28 34.56 5.47
Kopernicus DSF3 23.50 E 173.95 34.74 3.89
Astra 1/x 19.20 E 179.73 34.92 0.18
Eutelsat II F3 16.00 E 184.03 34.84 -2.65
Eutelsat II F1 13.00 E 188.05 34.61 -5.08
Hot Bird 13.00 E 188.05 34.61 -5.08
Eutelsat II F2 10.00 E 192.03 34.23 -7.35
Eutelsat II F4 7.00 E 195.96 33.70 -9.51
Sirius 1A 5.20 E 198.29 33.31 -10.77
Tele-X 5.00 E 198.55 33.26 -10.91
Telecom 2C 3.00 E 201.10 32.77 -12.28
Tv-Sat 2 0.60 W 205.60 31.73 -14.72
Thor 0.80 W 205.85 31.67 -14.85
Intelsat 702 1.00 W 206.09 31.60 -14.99
Telecom 2B 5.00 W 210.93 30.22 -17.69
Telecom 2A 8.00 W 214.44 29.04 -19.73
Statsionsat 11 11.00 W 217.84 27.77 -21.82
Orion 2 14.80 W 222.01 26.02 -24.53
Tdf 1-2 19.00 W 226.43 23.92 -27.65
New Skies 803 21.45 W 228.92 22.63 -29.55
Intelsat 601 27.50 W 234.81 19.27 -34.54
Hispasat 30.00 W 237.14 17.81 -36.75
Intelsat 603 34.50 W 241.19 15.11 -41.01Orion F1 37.50 W 243.81 13.26 -44.09
PanamSat 3R 43.00 W 248.44 9.79 -50.45
PanamSat 1 45.00 W 250.08 8.51 -53.06
SatMex 5 116.80 W ------ Below Horizont ----
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Antenna pointing (contd.)
Here is what I have chosen:Program No Satellite Pos Freq Pol Name
(MHz)
500 Hotbird 13E 13E 11727 V RTP
499 Hotbird 13E 13E 11489 V RTL 7
498 Eutelsat W2 16E 11095 V Algeria TV
497 Eutelsat W2 16E 11569 H Syrian TV
496 Eutelsat W1 10E 10987 H NTV
495 Eutelsat W1 10E 11621 V Samanyolu
494 Astra 19E 11494 H ARD
493 Astra 19E 11421 H MTV
492 Turksat 42E 10965 H ATV491 Turksat 42E 11093 V TRT
490 Telecom 2C 5W 12585 H TV5
489 Telecom 2C 5W 12690 V TF1
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What will be in the future?
We will use satellites mostly for moving large amounts ofdata, pushing content to the edges of Internet, sending
Internet TV and radio programs.
We will use stronger satellites, more efficient codings into
small antennas. There is and will be a market niche for DTH satellite
Internet, but p-to-p significance will not grow as it did in
the past.
With Ka-band we will be able to set up OC-12 links andbeyond.
Will LEO constellations change the way we think of
satellite communication?
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Conclusions?
Life will deliver its verdict, but one should not view the
whole topic as satellite vs fibre war. Satellite is great at
some applications, where fibre will never outperformsatellites. There will be numerous applications, which will
be realised over satellites for the years to come.
Thank you for your time.
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