[PPT]No Slide Title - IARC | Welcome...4z1pf/articles/VSAT Presentation.ppt · Web viewVSAT Technology and Applications Prepared for the Israel Amateur Radio Club By: 4X1DA – Rich

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VSAT Technology and Applications

Prepared for the Israel Amateur Radio ClubBy: 4X1DA – Rich HarelNovember 14, 2002

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Agenda

Introduction to Gilat Satellite NetworksWhat is a VSAT ?Typical VSAT ApplicationsSatellite Communication FundamentalsVSAT Network ArchitecturesAccess SchemesNetwork ComponentsNetwork ManagementVSATs Applications in Amateur RadioDemonstration of EquipmentSummary

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Gilat Satellite Networks Ltd.

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Gilat Satellite Networks Ltd.

Founded in 1987Over 950 employees worldwideCore technology: End-to-end two-way satellite broadband platformSales, service and support offices worldwideTraded on NASDAQ (GILTF) since 1993Revenues in 2001: $389MHeadquartered in Petech Tikva, IsraelThree Regional Headquarters:

Spacenet (North America) Mclean, VAGilat Latin America – Sunrise, FLGilat Asia, Pacific Rim and Africa – Petach Tikva, Israel

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What is a VSAT ?

VSAT = Very Small Aperture TerminalSatellite-based Wide Area Network (WAN), with centrally managed hubRemote site: less than 1.2m dish antennaMulti-service platform: Data, telephony and multimedia communicationsOptimal for continent-wide networks of hundreds or thousands of units

Small networks integrated in shared hub serviceLarge networks, in the tens of thousands, for Internet access

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VSAT Advantages

Full or partial independence from terrestrial infrastructure Cost savings over terrestrial linesNationwide reach, distance-independentNetwork management from a single pointQuick deployment, network flexibilityConsistent and rapid response timeIncreased network availability and reliabilityInherent broadcast / multicast platform

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Unicast, Multicast, Broadcast

Each Unicast Packet is Numbered and Acknowledged

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Unicast, Multicast, Broadcast

Multicasts Packets are Not AcknowledgedDifferent Data Steams can be sent simultaneously to many users

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Unicast, Multicast, Broadcast

Broadcast Packets are sent to all users in the Network SimultaneouslyBroadcasts are Not AcknowledgedVSAT Networks can use Reliable Broadcast Protocols and applications that are based on NACK’s, not ACK’s

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VSAT SpeedsCompared to Dialup Modem

The name of the game is THROUGHPUT !A 56K Modem will typically connect at speeds of only 43Kbps

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VSAT Markets

EnterpriseRetail; Oil & Gas; Banking; GovernmentPOS; Back Office; Browsing; Telemetry

TelephonyPublic: Public Call Offices, small businesses, farmers, private linesCorporate: Telephony/Data infrastructure

Internet (IP)High-speed, always-on, Internet-access for consumers, small businesses and schoolsIntranet and IP infrastructure for the enterpriseIP multicast-based services

BTVContent delivery

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Characteristics of GEO Satellites

35,680 Km above the Earth~24 Hour PeriodAverage 14-17 Year LifespanSingle Satellite theoretically can provide up to 42% Earth CoverageLarge, expensive, difficult to launchLocated approximately every 2o above the equator

Several Satellites may operate at the same azimuth on different frequencies/polarization

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The Clarke Belt

xx

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GEO/LEO Comparison Geosychronous (GEO) Low Earth Orbit (LEO) Example Eurosat Hot-Bird Series Iridium Referred to as:

“Fleet” “Constellation”

Suitable For:

TV/Radio Broadcasts; VSAT/Data Communications Networks; Telephony Networks; Data Multicast

Handheld Global Telephony Networks; Remote Sensing; Reconnaissance; Weather

Altitude 35,680 km 200-1400 km Orbit Geosynchronous (Inclination 00) Polar (Inclination 900) Period 24 Hours AOS-LOS Depends on Altitude

(Period Typically 90 Minutes) Cost 200-300m $US Relatively Cheap Stand-Alone

Yes (“Bent-Pipe”) No (Works in a Constellation) (*Single LEO Satellites must be constantly tracked and suffer from ‘Doppler Effect’)

Size 20-30 meter span As small as 13m Bands C; X-C; KU; Ka Primarily VHF/UHF; L-Band Delay Minimum 240ms Minimal Bitrate DVB 2.5-52 Mbps Low Bit Rates EIRP 30-54 dBW Depends on Satellite Frequency Re-Use

No (Only on Orthogonal Polarization)

Yes (On Non-Adjacent Spot Beams)

Launch Single Payload (>4000 kg Lift Capability)

Multiple; Can be “Piggybacked”

Life Span 14-17 Years 4-8 Years

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Geosynchronous Orbit Fleet

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LEO Orbit ConstellationGlobalstar

Loral initiativeSubsidiary of Airtouch (Cellular)

Aimed at global cellular phone coverage Qualcomm based CDMA

48 satellite constellation (8 planes x 6 ea. + 4 spares)

52 now in orbit ! 8 orbital planes of 6 satellites each 80% Earth coverage (+/- 68 degrees)

LEO orbit (1414 km)Ground Operations Control Centers (GOCCs) and Satellite Operations Control Centers (SOCCs) control gateway and control functions

Qualcomm GSP1600

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Obtaining Satellite Detailshttp://www.lyngsat.com

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Obtaining Satellite Detailshttp://www.lyngsat.com

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Satellite Details – Amos 1http://www.spacecom.co.il/

Middle East Beam

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Satellite Details – Amos 1http://www.spacecom.co.il/

European Beam

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VSAT Network ArchitecturesOne Way

One-Way – Receive OnlyHigh Bit-Rate DVB Compliant OutboundInbound Return Channel via Dial-Up ModemCan be used with existing infrastructure

Example: Harmonic’s CyberStreamTM

Satellite

Router

Internet

RFTIP Encapsulator

DVB Modulator

VSAT TVRO Antenna

DVB Receiver

LAN

Modem/ISDN Return

Baseband Equipment

TCP/IP ACK’s NACK’s

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VSAT Network ArchitecturesTwo-Way Star Topology

All VSATs Communicate via a Single HubNetwork is Independent of Existing InfrastructureVSAT Antenna Size dependent upon Power and Gain of Hub Antenna

Also Upon Inbound Bitrate, ODU Power and Satellite FootprintContention Based Access – Usually TDMA or FTDMATypical Ping Times Approximately 650-700ms

Hub

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

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VSAT Network ArchitecturesTwo-Way Star Topology – Double Hop

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VSAT Network ArchitecturesTwo-Way Mesh Topology

VSATs communicate directly with each otherSome systems require initial signaling via the HubLarger Antennas, Higher Power required at the VSATSmaller Antenna, Lower Power required at the HubUsed extensively in Telephony NetworksDelay minimized on VSAT to VSAT Calls

VSAT

VSAT

VSATVSAT

VSAT

VSAT

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Network Components

IntranetIntranet

InternetInternet

Firewall/Content Filtering

Application Servers/Acceleration ServersFarm (Optional)

PCsPCs

SkyBlaster 360EVSAT

RFT

Satellite

DVB VideoReceiver

NMS

Two WayBaseband

DVB Outbound

Router

OptionalVideo/AudioBroadcastProgramming

Skystar 360E

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Typical Hub Configuration

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Network Management

Entire Network Controlled, Configured and Monitored from a Single Location called the NOC (Network Operations Center)

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Typical VSAT Indoor Unit(Skystar 360E)

(Front) (Rear)

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Typical VSAT Outdoor Unit/Antenna

LNB

Reflector

LNB-F (Optional)

(Front) (Rear)

Feed-Assembly

SSPA (HPC)

LNB-F (Optional)

LNB

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VSAT Communication Bands

VSAT Networks use Geostationary Satellites (GEO) All located directly above the equator, at an altitude of ~36,000 km and spaced approximately every 2 degrees

BandUp-Link (GHz)

Down-Link (GHz)

Notes

L.9-1.6.9-1.6Shared with terrestrial

S1.610-1.6252.483-2.5Shared with ISM Band

C3.7-4.25.925-6.425Shared with terrestrial

Ku11.7-12.214-14.5Attenuation due to rain

Ka17.7-21.727.5-30.5High Equipment cost; attenuation due to rain

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Space Segment

VSAT Networks lease space segment from the Fixed Satellite Service (FSS) ProviderPrice is mainly determined by Bandwidth and PowerGeosynchronous Satellites frequencies consist of an Uplink and Dowlink, each covering a 500 MHz bandwidthThe many transponders operating within this range typically extend from 36-72 MHz each

Each Transponder has a finite power level that is shared amongst the usersExcessive Power levels can cause distortion to all users on the transponder

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Bit Rate/Symbol Rate

Symbol Rate =Bit Rate

# of bits transmitted with each symbol

If more bits can be sent with each symbol, then the same amount of data can be sent in a narrower spectrumFor example, for a bitstream of 80 kbps using BPSK (1 bit per symbol), the symbol rate is the same. For QPSK (2 bits per symbols), the symbol rate is ½ the bit rate or, 40 kbps. For 8PSK (3 bits per symbol) is would be 1/3 the bit rate, or 26.66 kbps

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0 1

0deg "0"180deg "1"

45deg “00”

135deg “10”

315deg “01”

225deg “11”

45o 11 State

135o 10 State

315o 00 State

225o 00 State

Q

I

1 State0 State

Q

I

Q

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Modulation Types

BPSK – Binary Phase Shift KeyingUse alternative sine wave phase to encode bitsSimple to implementInefficient use of BandwidthVery RobustOne bit per symbol (2 States)

QPSK – Quadrature (Quarternary) Phase Shift Keying

Efficient use of BandwidthRequires more complex receiver for demodulationTwo bits per symbol (4 States)

MSK – Minimal Shift KeyingEasy to Generate – More Complex ReceiverSpecial form of FSKSpectrally efficient, better noise performance at receiver

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Forward Error Correction (FEC)

FEC provides the ability for transmitted data to be ‘self-correcting’ without the need for re-transmission (As in ARQ)

Thus, we can transmit with LESS POWER - The price is Overhead and Bandwidth !

FEC ½ means that for every bit sent, an additional bit of overhead is sent; ¾ means for every 3 bits, one bit of overhead, and so on…

BER

10E-1

10E-2

10E-3

10E-4

10E-5

10E-6

3 4 5 6 7 8 9 Eb/N0

Un coded

Coded

Coding

Gain

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Forward Error Correction (FEC)

Two classes of Forward Error Correction codesConvolutional Codes and Block Codes

Convolutional Coding (Viterbi Decoding) Based on minimum hamming distance “code words” feed through a shift register

Reed Solomon Code (RS) is a form of Block Code that breaks the data stream up into fixed size blocks and adds redundancy symbols

On the other side of the link, the data is decoded using linear algebraic algorithms . This type of code adds considerable overhead

Concatenated Viterbi – refers to an error correction technique which uses Viterbi in conjunction with Reed Solomon coding. Adds approximately 2dB to the link budgetTurbo Codes with an even stronger coding gain will eventually replace Convolutional and RS coding

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Bit Error Rate (BER) & Eb/N0

Bit error rate is Directly Proportional to the Eb/N0 ThresholdTypical BER in some VSAT Systems can be <1.00E -08 (Less than one error in every 100,000,000 bits) for an Eb/No of only 4.8dB“Robust” in the digital worlds describes a system that can be (near) error-free in a noisy signal path

Place Picture of C/N Here Place MSK Signal Here

CW DPSK Modulation

C

N

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Link Budget (Margin)

The process of correctly sizing uplink and downlink paths for:

SatelliteHubRemotes

Takes into account:Satellite performancePath LossAtmospheric effectsFrequency bandsUplink antenna and amplifier performanceDownload antenna size and receiver noise figure

Path Loss at 12 GHz over 36,000 km can exceed –205 dB !

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Access SchemesThe Need for Bandwidth Efficiency

Bandwidth (and power) = $Better bandwidth efficiency translates into Cost Savings

Outbound and Inbound BW proportional to:

Number of UsersBit RatePower/Modulation & Error Correction Coding Type of trafficQoS (Quality of Service)

Outbound Transmission: Constant, Single FrequencyInbound Transmission: Bursty, Frequency HoppingAll VSATs must share the allocated inbound BW

OB IB

F1 F2 F3 F4 F5 F6 F7 Fn

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Access SchemesTime Division Multiple Access (TDMA)

Transmissions occur on the same frequency from multiple sourcesWhen a collision occurs, each source waits a random amount of time before re-transmittingTime slots are allowed to pass unusedIn a loaded network, more collisions will occur, increasing the random wait time

Frequency 1

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1119121711 17

18Ti

me

Collision Recognized

11 Retransmits after 3 slots delay time

Retransmits after 5 slots delay time17

Collision Occurs

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Access SchemesTime Division Multiple Access (TDMA)

Transmissions occur on the same frequency from multiple sourcesWhen a collision occurs, each source waits a random amount of time before re-transmittingTime slots are allowed to pass unusedIn a loaded network, more collisions will occur, increasing the random wait time

Frequency 1

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1119121711 17

18Ti

me

Collision Recognized

11 Retransmits after 3 slots delay time

Retransmits after 5 slots delay time17

Collision Occurs

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TimeSlots

Time

Frequency

Allocated Bandwidth

120kHz

1.2MHz

053102 006021

Inbound Frequencies

F1 F2 F3 F4 F5 F6 F7 F8 F9 F10

102 053 021006

102021 006

Retransmission102 006

VSAT 006 VSAT 021 VSAT 053 VSAT 102

Collision102006

Access SchemesFrequency/Time Division Multiple Access – Random Access (RA)

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Access SchemesAutomatic Dedicated Access

A “private” frequency is allocated to a single VSATCollision free, high throughput channel for batch applications and file transferWhen a DA is required by a VSAT, initiate request is sent in RA mode, triggered

According to IP-socket or IP addressAccording X.25 destination addressThroughput based

Then, a DA frequency is allocated

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25

21

21

14

14

14

f

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17

17

17

17

17

17

17

17

34 DA DARA

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t

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Access SchemesAutomatic Partial Dedicated Access

Partial allocation for better utilization of DA channelOptimal for Constant Bit Rate (CBR) applications, such as voiceGuarantees fixed response timeDA can be flexibly divide into PDAs 11

25

t

21

21

14

14

14

f

31

25

15

32

15

32

15

32

17

17

17

17

17

17

17

17

RA

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Access SchemesDual Bit Rate

Support of dual bit rate improves space segments utilizationAny 2 bit rates can be supportedEach VSAT supports two bit rates with multiple access modes

Lower bit rate for RA and higher bit rate for DA

Each Receiver Cage at the hub can handle two bit rates

t

f

17

17

17

17

17

17

17

17

15

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15

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DA PDA

76.876.8 153.6

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11

25

21

21

14

14

14

RA

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Acknowledgments over SatelliteSpoofing

The Problem: TCP/IP requires acknowledgment of each and every packet

The Satellite delay [(36,000/300000)2]2 in addition to all the routers along the way adds significant latency

Spoofing Concept:Acknowledge TCP packets locally at the VSAT/Hub – Send ‘Acknowledge Summary’ periodically

No Spoofing With Spoofing

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Acknowledgments over SatelliteInternet Page Acceleration (IPA)

On Terrestrial Based Networks, each HTML object is requested and acknowledgedIPA requests all the objects on a specific URLAll objects on an HTML Page are sent to the VSATs at once

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Amateur Radio ApplicationsInternet-to-Radio Link

Typical Node

VSAT Antenna

PC + Sound Card + VoIP Application

VSAT

Radio/PC Interface

VHF/UHF Conventional or Trunked Repeater

VHF or UHFOmni

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Amateur Radio ApplicationsInternet-to-Radio Link

New York Repeater/VSAT

Boston Repeater/VSAT

London Repeater/Direct

Hub

VoIPServers

Internet

VoIP Internet Direct

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Amateur Radio ApplicationsInternet-to-Radio Link - eQSO

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Amateur Radio ApplicationsInternet-to-Radio Link - Echolink

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Amateur Radio ApplicationsHF Remote Base/Diversity Reception

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FAQs (1)

What are the Largest VSAT Networks in the World ?Starband ~44,000 (US ISP); US Postal Service ~33,000

How many VSATs are operation World-Wide ?>400K installed by Gilat alone

Can a Star VSAT communicate with another VSAT without a Hub ?Star Topology – No. Mesh Topology VSATs can operate Point-to-Point.

Can a VSAT work Mobile ?No, due to the associated delay is some systems and antenna pointing issues. Mobile systems are under development.

Can a VSAT be used anywhere ?No. It can not be used at the extreme North and South latitudes due to coverage of Geostationary satellites. You must have line-of-site coverage towards the satellite your network is working on.

What are typical upsteam and downsteam speeds that can be achieved with a VSAT ?

Depends on the VSAT ISP. Btopenworld in the UK is offering 500/120 kbps (Upstream/Downstream) service. Theoretically, much higher speeds can be achieved.

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FAQs (2)

Can I view DVB-S video stream from the same antenna/LNB ?Yes. (So long as it is on the same satellite). Elliptical antennas allow adding two additional LNBs with switchable polarization.

How many PC’s can I connect to a VSAT ?Theoretically, as many as you want. The limiting factor is that they will be sharing the Inbound/Outbound Bandwidths. The other limiting factor is the total number of TCP/IP sockets and whether or not the VSAT ISP set up the VSATs to assign an IP address to connected PC. Up to 4 is recommended.

What applications are NOT suitable for VSATs ?VSAT traffic has an inherent latency due to the distance. Real-Time Internet Gamming other time-critical applications will not work as well as terrestrial lines.

What changes can we expect to see in the future concerning VSAT technology, markets ?

When Ka-Band Satellite service begins, we can expect to see much smaller dishes. 8PSK instead of the current QPSK on the Outbound, Internal Caching on VSAT, plus much more.The Rural Telephony market is booming and when mobile VSAT equipment becomes available, the industry is expected to change entirely.

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Probing Further…

Gilat Satellite NetworksSpacenet (Gilat Subsidiary in US)FAQ’s (Btopenworld Satellite Service)Lyngsat (Geostationary Satellite Database)Phase Modulation TutorialsDigital Modulation BasicsMPEG TutorialDVB Standards TutorialFEC TutorialSpectrum Analysis BasicsSpectrum Analysis AM-FM Measurementswww.satil.com (Israeli TVRO Information in Hebrew)AFRTS TVRO Satellite HandbookChannel Master VSAT AntennasTelecommutations Glossary