CEENET Workshop 2001 Satellite communications Krzysztof Muchorowski NetSat Express muchorids'pl

1
CEENET Workshop 2001Satellite
communicationsKrzysztof MuchorowskiNetSat
Expressmuchor_at_ids.pl
2
Introductory remarks

• The purpose of this lecture is to give you a very
  general overview of satellite communication, it
  is not meant to be a complete 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 please stop me if I do.

3
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.

4
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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• R6400 km T84 minutes
• R7100 km T99 minutes (LEO)
• R11400 km T201 minutes (MEO)
• R42350 km T24 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?

6
a few remarks about LEO and MEO
satellites(Teledesic, Iridium)
7
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 GEO satellite 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)

8
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

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 and launched.

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(No Transcript)
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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 was 32,051
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 any use 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 more Ariane 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
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Does Size Matter?
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Other satellite issues (to close the topic)

• Rights to orbital slots, landing rights.

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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 on Earth.

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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 wider relative 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 effect occurs
  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 in standby or manual mode.
• You want to reroute traffic for the several
  minutes of outage each day (worst case).
• For those customers with duplex service, it is
  important to remember that the outage for your
  inbound and outbound links may occur at different
  days and at different times during the day.
• http//www.ips.gov.au/papers/richard/calc_inter.ht
  ml

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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 a 2.4m)
• 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 )

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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 antenna pointing

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Compact Indoor Unit

• 5 phone / fax jacks
• 9.6 Kb. Data
• 56 / 64 Kb HSD
• Plug in Interfaces forRS-232,-449, V.35,X.21,
  and S0 ISDN
• Menu in 5 languages
• Speakerphone

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Go Anywhere Package

• Entire system packs in a soft carry case
• Case contains
• Antenna
• RF Unit
• Indoor Unit
• Power Unit
• Cables
• Manual

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Great Accessories for a 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 main course

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Receiving/transmitting devices

• LNA (Low Noise Amplifier) or LNB (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 amplifiers provide 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)
34
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 almost every 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)
40
IRD instead of a modem

• Integrated receiver decoder (IRD) performs same
  functions as 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 and
  broadcast applications.

41
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.

43
Bit Error Rate
44
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 two variables
• allocated bandwidth (a function of the data rate,
  modulation/coding scheme, carrier spacing)
• allocated power (minimal power assignment which
  is sufficient to produce 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)
47
Link budget (contd)

• Therefore, link budget calculations tell us what
  is the optimum 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 2048103 /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.

49
Moving up one layer to layer 2...

• OK, so we have a connection, both modems are
  locked to their 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 shared
by multiple users User packets are
interleaved Each site filters out its own
packets. 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!)

53
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

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An Content Delivery Network Incorporating DVB
b - Content Delivery Site hosts data for eventual
playout to edge and end sites
News Feed
Edge Sites (ES) include ISPs, Web Host
Facilities, Cable Head Ends etc. End Sites
include corporate locations and SOHO sites
Caching Feed
Content Delivery Site
c - Content Delivery Site Multicasts Documents to
Edge Sites and End Sites
Edge Site
d - Edge Sites store documents in Servers
The Net
End Site
e - End Sites store documents in local Servers or
in requesting PC
3 - ES returns document
2 - ISP requests document from closest Edge
Site
Content Providers
1 - Client requests document
4 - ISP returns document
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a - Content Providers send web documents to
Content Delivery Site
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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
  1/22/33/45/67/8
• 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 (!)

56
DVB Packet Format

• MPEG

Payload
Overhead (4 bytes)
184 bytes
188 bytes
IP Encapsulation
Padded or packed area
IP Packet
16 byte header
MPEG Packets
57
DVB Uplink Data Flow
Modulates RF carrier applies Reed-Solomon coding
and FEC
MPEG Video Transport Stream and other multimedia
Internet
IP Packets
R O U T E R
DVB Mod.
MPEG Multiplexer
IP Encapsulator
Private lines
Encapsulates IP Packets within MPEG Transport
Stream
Muxes MPEG program streams encodes bit stream
Conditional Access System
Controls program entitlements key words for
encryption
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DVB Integrated ReceiverDecoder (IRD) Structure
Note IRD shown in this slide is set top box
could also be PC card.
carrier with multiple streams and substreams
NOTE IRD in this slide is depicted as set top
box could also be card that fits in PC
LNB
Local PIDs Only
All PIDs
IRD
100 Base T Port
Local router
Serial Port
Common Interface

• demodulates transport stream
• filters by PID number
• provides Conditional Access processing
• reassembles IP packet
• could filter on IP or MAC address

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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!

61
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,
  comes out, 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).

63
SATNET and MFNET (some history)

• 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

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USAN
65
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

66
(No Transcript)
67
Effect of propagation delay on TCP networks(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 applications such as Oracle and
  Exchange Server resulting in slow downs of 10
  times or more
• 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 they
  lack large window support
• TCPs essential congestion control mechanisms
  degrade performance over GEOs. These mechanisms
  cannot be removed without potentially causing the
  "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 because signaling 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

68
Effect of propagation delay on TCP networks
(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
  only transmit 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. The total 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...

69
Effect of propagation delay on TCP networks (a
bit of relief)

• This effects only a single TCP session! A large
  number of users, 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 are very uncomfortable with such
  large delay Oracle, Exchange, telnet, NNTP,
  voice
• What? Did I say voice? Voice-over-IP? Has
  someone rang me?

70
Effect of propagation delay on TCP networks
(contd)

• Technical issues with Long Fat Networks - no
  longer just a satellite problem
• Approaches include SACK (RFC 1072, 2018), TCP
  spoofing, Transaction TCP (T/TCP),
• and LEO

71
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 over
• the 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 satellite communications. Results in higher
  speed and reduced bandwidth utilization.
• This is usually a premium service. It will not
  work with IPv6.

72
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!

73
IP Voice Network
74
IP Voice Network
75
Back to satellite Internet

• Types of connections
• bi-directional
• symmetric
• asymmetric (typically 14)
• uni-directional (receive-only)
• Routing issues
• on bi-directional links
• on receive-only links
• Burstability

76
Bi-directional satellite Internet connections

• capacity may be symmetric or asymmetric,
  depending on needs, applications etc.
• typically, for asymmetric setup, 14 of
  outgoing/incoming bandwidth is assumed.
• one needs to assume about 10-20k for such
  hardware

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!

78
Burstability

• This is a unique feature of satellite networks.
  It works best in 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 be used 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.

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 (when we 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)

80
More about routing for RO links.

• Option 1 Both satellite provider and your local
  ISP announce your routes. The smallest 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 to
  transverse 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.

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, but
  not the others.

82
The Problem with Unicast

• 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 bandwidth compared to web
  applications, you had, until multicast came into
  scene- two optionsto 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 and your
  network would collapse.

83
What about Broadcast ?

• Broadcast seems to be a solution, but it's not
  certainly the solution. If you want all 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 a LAN, but problems arise when
  you want broadcast packets to be routed across
  different LANs.

84
Multicast the Best Solution !

• The best solution seems to be one in which you
  send packets to a certain special 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 previously registered as being "of
  interest".

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...

86
Some advices...
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 a main 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!

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 your network so that all
  incoming/outgoing traffic is handled by one
  router
• access lists are easier to manage

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 find one 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.

90
Satellite positions in the sky in Budapest

• AimSat 1.1
• Satellite data for Budapest
• Latitude 48r00'00" N
• Longitude 19r00'00" 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
  7.72

• 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 -41.01

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 ATV
• 491 Turksat 42E 11093 V TRT
• 490 Telecom 2C 5W 12585 H TV5
• 489 Telecom 2C 5W 12690 V TF1

92
What will be in the future?

• We will use satellites mostly for moving large
  amounts of data, 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 and beyond.
• Will LEO constellations change the way we think
  of satellite communication?

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 outperform satellites.
  There will be numerous applications, which will
  be realised over satellites for the years to
  come.
• Thank you for your time.