budapest ceenet 2001 - satellite communications

8/3/2019 Budapest Ceenet 2001 - Satellite Communications

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August 26, 2001 1

CEENET Workshop 2001

Satellite communications

Krzysztof Muchorowski

NetSat Express

[email protected]


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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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August 26, 2001 9

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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August 26, 2001 16

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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August 26, 2001 32

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



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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...



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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


74/93

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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August 26, 2001 75

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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August 26, 2001 76

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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August 26, 2001 77

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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August 26, 2001 78

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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August 26, 2001 79

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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August 26, 2001 80

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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August 26, 2001 81

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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August 26, 2001 82

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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August 26, 2001 83

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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August 26, 2001 84

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 !


85/93

August 26, 2001 85

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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August 26, 2001 86

Some advices...


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August 26, 2001 87

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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August 26, 2001 88

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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August 26, 2001 89

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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August 26, 2001 90

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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August 26, 2001 91

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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August 26, 2001 92

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?


93/93

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.