1 VSAT– the only viable solution for Rural Pakistan.

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VSAT– the only viable solution for VSAT– the only viable solution for Rural PakistanRural Pakistan

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Why VSAT? Why VSAT? VSAT networks provides: Reliability in transmission of data (data, voice, video) Allocation of resources to different users

(bandwidth, amplification power) Fixed network solutions at reasonable price Provide point-to-multipoint (broadcast), multipoint-

to-point (data collection), point-to-point communications and broadband multimedia services.

Serviced in land area which are difficult to install (remote locations ,desert areas).

An ability to have direct access to users and user premises.

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Satellite Services & ApplicationsSatellite Services & Applications

Launch Vehicles Ground Equipment Insurance Manufacturing

Infrastructure / Support Services

Remote Sensing• Pipeline Monitoring• Infrastructure Planning• Forest Fire Prevention• Urban Planning• Flood and Storm watches• Air Pollution Management• Geo-spatial Services

GPS/Navigation• Position Location• Timing• Search and Rescue• Mapping• Fleet Management• Security & Database Access• Emergency Services

Direct-To-Consumer • Broadband IP • DTH/DBS Television• Digital Audio Radio• Interactive Entertainment & Games• Video & Data to handhelds

Voice/Video/Data Communications• Mobile Telephony•Rural Telephony• News Gathering/Distribution• Internet Trunking• Corporate VSAT Networks• Distance-Learning• Videoconferencing• Business Television• Broadcast and Cable Relay• VOIP & Multi-media over IP

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VSAT Characteristic and AdvantageVSAT Characteristic and Advantage

Reliability: reliable satellite transmission of data, voice and video between an unlimited number of geographically dispersed sites or from these sites to headquarters

Flexibility: The VSAT networks offer enormous expansion capabilities; On the other hand, VSATs offer unrestricted and unlimited reach. Additional VSATs can be rapidly installed to support the network expansion to any site, no matter however remote.

Network Management: Network monitoring and control of the entire VSAT network is much simpler than a network of leased lines, easily integrates end-to-end monitoring and configuration control for all network subsystems.

A low mean-time to repair - few hours, compare to leased lines which extends up to a few days. Essentially, lesser elements imply lower MTTR. Uptime of up to 99.5 percent is achievable on a VSAT network. This is significantly higher than the typical leased line uptime of approximately 80-85%.

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Cost: VSAT network offers significant savings over 2-3 years timeframe. The service charges depend on the bandwidth which is allocated to the network in line with customer requirements. In Pakistan’s scenario, The cost of bandwidth on optical fibre is comparably high than the satellite bandwidth when the distance increases a distance of 500 km. (Satellite communication is totally distance-sensitive.)

Link Budgets: RF equipment would cater to the requirements of the network topology and satellite modems in use. The link Budget estimates the ground station and satellite EIRP (Effective Isotropic Radiated Power) required. Calculations of signal levels through the system to ensure the quality of service should normally be done, prior to the establishment of a satellite link.

VSAT Characteristic and AdvantageVSAT Characteristic and Advantage

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Satellite-Fiber ComparisonSatellite-Fiber Comparison

Comparing Satellite and Fiber Characteristics

Capability Fiber Optic Cable

Systems

Geo Satellite in a Global System

Meo Satellite in a Global System

Leo Satellite in a Constellation

Transmission Speed

10 Gbps-3.2 Terabits/second*

Single Sat 1 Gbps-10 Gbps

Single Sat 0.5 Gbps- 5 Gbps

Single Sat .01 Gbps-2Gbps

Quality of Service

10-11 10 -12 10-6 10 -11 10-6 10 -11 10-210 91

Transmission latency

25 to 50 ms 250 ms 100-150 ms 25-75 ms

System Availability w/o

Backup

93 to 99.5% 99.98% (C-Ku band) 99% (Ka band)

99.9% (C-Ku band) 99% (Ka band)

99.5% (L-C-Ku band) 99% (Ka band))

Broadcasting Capabilities

Low to Nil High Low Low

Multi-casting Capabilities

Low High High Medium

Trunking Capabilities

Very High High Medium Low

Mobile Services Nil Medium-to-High High High

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““Typical” Fixed Satellite NetworkTypical” Fixed Satellite Network

Branch Offices

Corporate Data Center/HQ

Network HUB

Corporate Offices

Gas Stations

Apartment Buildings

Residential

Internet

Applications• Credit Card Validation• ATM/Pay at the Pump• Inventory Control• Store Monitoring• Electronic Pricing• Training Videos• In-Store Audio• Broadband Internet Access• Distance Learning

Some large scale corporate networks have as many as 10,000 nodesSome large scale corporate networks have as many as 10,000 nodes

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Satellite FrequenciesSatellite Frequencies

There are specific frequency ranges used by commercial satellites.

L-band (Mobile Satellite Services)

1.0 – 2.0 GHz

S-band (MSS, DARS – XM, Sirius) 1.55 – 3.9 GHz

C-band (FSS, VSAT) 3.7 – 6.2 GHz

X-Band (Military/Satellite Imagery) 8.0 – 12.0 GHz

Ku-band (FSS, DBS, VSAT) 11.7–14.5 GHz

Ka-band (FSS “broadband” and inter-satellite links) 17.7 - 21.2GHz and 27.5 – 31 GHz

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Orbital OptionsOrbital Options

A Geosynchronous satellite (GEO) completes one revolution around the world every 23 hrs and 56 minutes in order to maintain continuous positioning above the earth’s sub-satellite point on the equator.

A medium earth orbit satellite (MEO) requires a constellation of 10 to 18 satellites in order to maintain constant coverage of the earth.

A low earth orbit satellite (LEO) offers reduced signal loss since these satellites are 20 to 40 times closer to the earth in their orbits thus allowing for smaller user terminals/antennas.

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Geostationary Orbit (GEO)Geostationary Orbit (GEO)

Characteristics of Geostationary (GEO) Orbit Systems• User terminals do not have to track the satellite• Only a few satellites can provide global coverage• Maximum life-time (15 years or more)• Above Van Allen Belt Radiation• Often the lowest cost system and simplest in terms of tracking and high

speed switching

Challenges of Geostationary (GEO) Orbit• Transmission latency or delay of 250 millisecond to complete up/down link • Satellite antennas must be of larger aperture size to concentrate power

and to create narrower beams for frequency reuse• Poor look angle elevations at higher latitudes

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Geostationary Orbit TodayGeostationary Orbit Today

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Low Earth Orbit (LEO)Low Earth Orbit (LEO)

Characteristics of Low-Earth Orbit (LEO) Systems - Low latency or transmission delay - Higher look angle (especially in high-latitude regions) - Less path loss or beam spreading - Easier to achieve high levels of frequency re-use - Easier to operate to low-power/low-gain ground antennas

Challenges of Low-Earth Orbit (LEO) Systems - Larger number of satellites (50 to 70 satellites). Thus higher

launch costs to deploy, build, and operate. - Harder to deploy, track and operate. There is higher

TTC&M costs even with cross links. - Shorter in-orbit lifetime due to orbital degradation

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Medium Earth Orbit (MEO)Medium Earth Orbit (MEO)

Characteristics of Medium-Earth Orbit (MEO) Systems • Less latency and delay than GEO (but greater than LEO)• Improved look angle to ground receivers in higher latitudes• Fewer satellites to deploy and operate and cheaper TTC&M

systems than LEO (but more expensive than with GEO) • Longer in-orbit lifetime than LEO systems (but less than GEO)

Challenges of Medium-Earth Orbit (MEO) Systems • More satellites to deploy than GEO (10 to 18 vs. 3 to 4)• Ground antennas are generally more expensive and complex

because of the need to track satellites. Or, one must use lower-gain, quasi-omni antennas.

• Increased exposure to Van Allen Belt radiation

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TranspondersTransponders

• The transponder is the “brain” of the satellite - provides the connection between the satellite’s receive and transmit antennas.

• Satellites can have 12 to 96 transponders plus spares, depending on the size of the satellite.

• A transponder bandwidth can frequently be 36 MHz, 54 MHz, or 72 MHz or it can be even wider.

• A transponders function is to • Receive the signal, (Signal is one trillion times weaker then when transmitted)

• Filter out noise, • Shift the frequency to a down link frequency (to avoid interference w/uplink)• Amplify for retransmission to ground

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Frequency EfficiencyFrequency Efficiency

• The vital resource in satellite communications is spectrum. • As the demand for satellite services has grown, the solution

has been; • To space satellites closer together, • Allocate new spectrum in higher bands, • Make satellite transmissions more efficient so that more

bits/Hz can be transmitted, and • To find ways to re-use allocated spectrum such as through

geographic separation into separated cells or beams or through polarization separation

• Today the satellites systems transmit more efficiently than ever before but interference is now a bigger problem - there is a basic trade off; • The higher the frequency the more spectrum that is available • But, the higher the frequency the more problems with

interference from other users terrestrial, unlicensed, etc.

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World Satellite Industry RevenuesWorld Satellite Industry Revenues

$0

$20

$40

$60

$80

$100

1996 1997 1998 1999 2000 2001 2002 2003

Re

ve

nu

e (

in b

illi

on

s)

$38.0

$49.1$55.0

$60.4

$73.7$78.6

$86.1$91.0

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$0.0

$10.0

$20.0

$30.0

$40.0

$50.0

$60.0

1996 1997 1998 1999 2000 2001 2002 2003

Reven

ue (

in B

illio

ns)

FSS MSS DBS

World Satellite Services RevenueWorld Satellite Services Revenue

FSS=VSAT services, remote sensing, and transponder leasing MSS=Mobile telephone and mobile dataDBS/DARS=DTH TV, DARS, and Broadband

$15.8

$ 21.1$ 24.4

$ 29.7

$ 39.2

$ 46.5$49.1

$55.9

FSS 6.1$ 6.8$ 7.3$ 8.6$ 9.2$ 8.9$ 8.7$ 9.6$ MSS 0.7$ 0.8$ 1.0$ 1.3$ 2.1$ 1.4$ 1.3$ 1.7$ DBS 9.0$ 13.5$ 16.1$ 19.8$ 27.9$ 36.2$ 39.1$ 44.7$

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World Ground Equipment RevenuesWorld Ground Equipment Revenues

$22.1$21.2$19.6

$13.9$12.5

$17.7

$9.7

$16.0

$0

$5

$10

$15

$20

$25

1996 1997 1998 1999 2000 2001 2002 2003

Rev

enue

(in

billi

ons)

Includes: Gateways, NOCs, Satellite News Gathering equipment, flyaways, VSATs, DBS Dishes, DARS equipment, satellite phone booths, satellite phones

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Global Supply vs. DemandGlobal Supply vs. DemandGEO Communications Satellites and LaunchesGEO Communications Satellites and Launches

0

10

20

30

40

50

60

70

1995 1996 1997 1998 1999 2000 2001 2002 2003

Nu

mb

er

of

Sa

tell

ite

s/L

au

nc

he

s

Launches Satellites Ordered

Satellite Capacity Launch Capacity

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Ground AntennasGround Antennas

The size of the antenna depends on the satellite frequency band used, the data rate, and whether the service is bidirectional or receive only Higher data rates require larger antennas and/or higher

power Higher transmit capability (EIRP) of the satellite allows

the antenna size to be reduced The use of spot beams instead of global beams improves

VSAT link performance Receive-only antennas can be substantially smaller

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Critical to Flow of InformationCritical to Flow of Information

• Newsgathering – First choicefor live coverage, providinghigh-bandwidth video links from remote locations to capture “breaking news”

• Program Delivery – National broadcasts from four major television networks and more than 180 cable channels are relayed to over 10,000 local cable systems via satellite

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VSAT TechnologyVSAT Technology

Bands C-band (4-6 GHz), Ku-band (10-20 GHz) and Ka-band (20-30 GHz) that require different licensing approaches.

Entities a) the Space Segment operator; b) the satellite

network operator, who operates one or more Gateway Stations or Network Control Stations (HUBs) or other ground stations; c) the Satellite Service Provider; d) the subscriber who uses individual VSAT equipment

Types – Oneway – DTH and Two-way Connectivity – Point to Point (Mesh),

Point to Multipoint (star, hub at centre), Multipoint to multipoint (hybrid)

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-

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120,000

140,000

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VSAT: A Consistent VSAT: A Consistent PerformerPerformer

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VSAT Vs. Leased LineVSAT Vs. Leased Line VSAT

Footprint across the countryHigh initial investmentHigh reliability – Uptime of 99.5%No recurring b/w costs

Leased LineOption available only at areas with an

existing VSAT hub Low initial investment Dependant on the Local HubRecurring Bandwidth costs

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DVB - RCSDVB - RCS

InternetInternet

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DVB-RCSDVB-RCS

Standardisation:DVB-RCS compliant terminals can speak to

all DVB-RCS compliant Gateways.

The terminal is primarily a slave and the Gateway is in charge of efficient resource utilisation, fair sharing of resources and optimising performance.

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DBV-RCSDBV-RCS• A DVB/RCS user will typically require Internet access on best effort basis.

• He will not run a time critical application (i.e.video).

• This customer must accept limited/occasional accessibility due to the shared usage of the capacity.

• He has no need for dedicated channel, and his applications are not time critical.

• He must accept shared use of common infrastructure with other users.

• If there is a need for crypto, the crypto equipment will need to synchronies each time the remote terminal make a connection.

• A good solution if Internet & Data is the most important services and a best effort service is what the users require. VoIP can be used as a additional service and with limited usage of voice service DVB-RCS can still be a type of service that a very small office.

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Fixed Satellite Technology OptionsFixed Satellite Technology Options

TDM/TDMATraditional data VSAT

systemsLow cost remotes,

expensive hubStar network topologyTransactional data

Credit card validation/POS Internet …

Low user data rate

Fre

qu

en

cy

Time

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SCPC/MCPC (FDMA, Frequency divided multiple access)

Point-to-Point IDR –

DCME(compression)GatewaysUplinksFixed bandwidthBroadcast

Audio/VideoStatic traffic patterns

Fre

qu

en

cy

Time

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SCPC / MCPCSCPC / MCPC

A typical SCPC customer runs business critical real time applications. This customer has high requirements to QoS. He also typically runs a wide range of services such as voice, video,

Internet, ERP systems. Crypto equipment will have no difficulties in this environment, as there

are dedicated channels that are always on. This customer demands a fixed Star network, which will fulfil the

requirements he operates in that might be difficult to predict in advance (especially geographically diversity).

Technology typically used as a Star VSAT Network or as Point to Point connection, (SCPC duplex)

This customer dos not have the need for occasional “bursting” or accept to pay for the bandwidth required.

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SCPC/DAMACentralized Net MgmtStar and MeshLow cost remotesOne modem/Interface

per channelLarge gateways

required

Fre

qu

en

cy

Time

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SCPC / DAMASCPC / DAMA

A typical SCPC / DAMA user, runs business critical real time applications, but has to make sure that the application allows the DAMA system to burst (increase or decrease the bandwidth). Or use dedicated bandwidth for the RTA when required (When the application is in use).

This customer has high requirements to QoS. He also typically runs a wide range of services such as voice, video,

Internet, ERP systems. Crypto equipment will have no difficulties in this environment. This customer demands a flexible network, which will fulfil the

requirements he operates in that might be difficult to predict in advance (especially geographically diversity) and have a demand / need of bursting (higher data rate if available).

Technology typically used for a VSAT Network as Star or/and Mesh, with a number of remote terminals that cheers the total allocated bandwidth pool (Inbound).

In cases where there is time diversity between the remote terminals, the DAMA functionality improves the efficiency and utilisation of space segment.

He also wants a dedicated network/bandwidth with no sharing of resources with other customers.

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Satellite Technology OptionsSatellite Technology Options

TDMA/DAMAStar/Mesh/Hybrid

networksMultimedia,

multiserviceEfficient space

segment utilizationEasily expand

network and site capability

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Satellite Technology OptionsSatellite Technology Options

Fre

qu

en

cy

Time

SCPC

DAMA Fre

qu

en

cy

Time

One block = 64 Kbps

Sample when a DAMA system is cost-effectiveIf is a number of sites in a VSAT Network

Sample when a SCPC system is cost-effective

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SummarySummarySatellite technology is the fastest way to get a

reliable connection from A to B in an emergency situation.

Both a SCPC and a DAMA solution can be used in an emergency situation as a VSAT connection. Both technologies can be used as a FlyAway (Quick deploy) system. Both systems can run the same services.

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Type of satellite serviceType of satellite service

International Telephony – using Public Switched Telephone Network (PSTN) Intermediate Data Rate (IDR) Time Division Multiple Access (TDMA)

Broadcasting TV Uplink Television Receive Only (TVRO) Digital Satellite News Gathering (DSNG)

VSAT Personal Earth Station (PES-TDMA) Telephony Earth Station (TES-TDMA) Domestic IDR/Single Channel Per Carrier (SCPC) FDMA (Frequency Division Multiple Access)

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Type of VSAT technologyType of VSAT technology

TDMATime-division

Multiple Access

TDMATime-division

Multiple Access

FDMAFrequency Division Frequency Division

Multiple AccessMultiple Access

FDMAFrequency Division Frequency Division


SCDCSingle-carrier Single-carrier per Channelper Channel

SCDCSingle-carrier Single-carrier per Channelper Channel

VSAT TECHNOLOGY

VSAT TECHNOLOGY

DAMADAMA Demand Assigned Demand Assigned


CDMACDMA Code Division Code Division Multiple AccessMultiple Access

PAMAPAMA Pre-Assigned Pre-Assigned


FDMA

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VSAT TopologyVSAT Topology STAR - the hub station controls and monitors can

communicates with a large number of dispersed VSATs. Generally, the Data Terminal Equipment and 3 hub antenna is in the range of 6-11m in diameter. Since all VSATs communicate with the central hub station only, this network is more suitable for centralized data applications.

MESH - a group of VSATs communicate directly with any other VSAT in the network without going through a central hub. A hub station in a mesh network performs only the monitoring and control functions. These networks are more suitable for telephony applications.

HYBRID Network - In practice usually using hybrid networks,

where a part of the network operates on a star topology while some sites operate on a mesh topology, thereby accruing benefits of both topologies.

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TDMA (time-division multiple access)TDMA (time-division multiple access)

When numerous remote sites communicate with one central hub, this design is similar to packet-switched networks.

Because of competition with one another for access to the central hub, it restrict the maximum bandwidth in most cases to about 19.2 kbps.

all VSATs share satellite resource on a time-slot basis.

Usually used in STAR topology as a transmission technique.

Offered to domestic needs.

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TDMA (time-division multiple access)TDMA (time-division multiple access)

The VSAT Hub communicates with all dispersed VSATs (typically a 1.8-meter diameter parabolic-shaped dish) on an outgoing channel of up to 512kbps based on the TDM scheme. The incoming or return channel from the dispersed VSATs uses the TDMA channel technology that enables a large number of the respective VSATs to share this single return channel. The incoming routes typically operate at 128kbps, and can go up to a maximum bandwidth of 256kbps.

Copyright Maxis

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SCPC (single-carrier per channel)SCPC (single-carrier per channel)

SCPC-based design provides a point-to-point technology, making VSAT equivalent to conventional leased lines.

dedicated bandwidth of up to 2 Mbps Usually use in an international VSAT

services in Asia-Pacific.

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In the Hub-to-Remote configuration, one end of the VSAT link (normally the customer's HQ) is connected to the 11-meter VSAT Hub (Earth Station) via a terrestrial leased line. A VSAT antenna at the remote end or the distant end (normally the branch office) of the VSAT link is then interconnected to the VSAT hub via the satellite.

Copyright Maxis

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VSAT links with a Remote-to-Remote configuration bypass the VSAT Hub and has a stand-alone VSAT antenna at both ends of the link. Typical VSAT antenna size ranges from 1.8m to 2.4m.

Copyright Maxis

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FDMA (Frequency Division Multiple Access)FDMA (Frequency Division Multiple Access)

oldest method for channel allocation the satellite channel bandwidth is broken into

frequency bands for different earth stations the earth stations must be carefully power-controlled

to prevent the microwave power spilling into the bands for the other channels. Here, all VSATs share the satellite resource on the frequency domain only.

3 type: PAMA (Pre-Assigned Multiple Access); DAMA (Demand Assigned Multiple Access); and CDMA (Code Division Multiple Access).

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PAMA (Pre-Assigned Multiple Access)PAMA (Pre-Assigned Multiple Access)

The VSATs are pre-allocated a designated frequency. Equivalent of the terrestrial (land based) leased line solutions.

PAMA solutions use the satellite resources constantly. Therefore, no call-up delay in the interactive data applications or high traffic volumes.

PAMA connects high data traffic sites within an organization.

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DAMA (Demand Assigned Multiple Access)DAMA (Demand Assigned Multiple Access)

The network uses a pool of satellite channels, which are available for use by any station in that network.

On demand, a pair of available channels is assigned, so that a call can be established. Once the call is completed, the channels are returned to the pool for an assignment to another call.

Since the satellite resource is used only in pro-portion to the active circuits and their holding times, this is ideally suited for voice traffic and data traffic in batch mode.

DAMA offers point-to-point voice, fax, data requirements and supports video-conferencing. Satellite connections are established and dropped only when traffic demands them.

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CDMA (Code Division Multiple Access)CDMA (Code Division Multiple Access) Under this, a central network monitoring system allocates a

unique code to each of the VSATs. Enabling multiple VSATs to transmit simultaneously and share a common frequency band.

The data signal is combined with a high bit rate code signal which is independent of the data.

Reception at the end of the link is accomplished by mixing the incoming composite data/code signal with a locally generated and correctly synchronized replica of the code.

Since this network requires that the central network management system co-ordinates code management and clock synchronization of all remote VSATs, STAR topology is the best one.

Mainly used for interference rejection or for security reasons in military systems.

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Opportunities in VSAT technologyOpportunities in VSAT technology

Voice over IP (VoIP) via satellite Frame Relay via satellite ATM via satellite Video-on-demand via satellite Multimedia application

Internet/e-mail connectionTelemedicineDistance learning

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VSAT: A Consistent VSAT: A Consistent PerformerPerformer

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Users of Satellite Communications

Banking SectorData NetworksTelecommunications (Cellular) Power Production InfrastructureOil & Gas

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Motivation to use VSATMotivation to use VSAT

The last mile problem Hard to reach areas Reliability Time to deploy (4-6 months vs. 1-2 weeks) Flexibility Cost ( If distance is more than 500 km then the

VSAT solution is more cost-effective as compared to the optical fiber.)

VS

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VSAT IMPLEMENTATION - 2VSAT IMPLEMENTATION - 2

There are basically two ways to implement a VSAT Architecture

STARVSATs are linked via a HUB

MESHVSATs are linked together without going

through a large hub

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VSAT IMPLEMENTATION - 3VSAT IMPLEMENTATION - 3

Higher Propagation delayUsed by TDMA VSATsHigh central hub investmentSmaller VSAT antenna sizes (1.8 m typically)Lower VSAT costsIdeally suited for interactive data applicationsLarge organizations, like banks, with centralized

data processing requirements

Lower Propagation delay (250 ms)

Used by PAMA/DAMA VSATs

Lower central hub investment

larger VSAT antenna sizes (3.8 m typically)

Higher VSAT costs

Suited for high data traffic

Telephony applications and point-to-point high-speed links

Source: www.bhartibt.com

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Basic TopologiesPoint to Point (SCPC)

Customer located antenna

Earth station with terrestrial tail or customer located antenna

Earth Station with terrestrial tail to customer premises

Point to Multipoint (TDMA)

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VSAT STAR ARCHITECTURE - 2VSAT STAR ARCHITECTURE - 2

• In this network architecture, all of the traffic is routed via the master control station, or Hub.• If a VSAT wishes to communicate with another VSAT, they have to go via the hub, thus necessitating a “double hop” link via the satellite.• Since all of the traffic radiates at one time or another from the Hub, this architecture is referred to as a STAR network.

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Master Control Station (The Hub)

VSAT Community

All communications to and from each VSAT is via the Master Control Station or Hub

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Satellite HUB

VSAT

VSAT

VSAT

VSAT

VSAT

Topology of a STAR VSAT network viewed from the satellite’s perspectiveNote how the VSAT communications links are routed via the satellite to the Hub in all cases.

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VSAT MESH ARCHITECTURE - 1VSAT MESH ARCHITECTURE - 1

• In this network architecture, each of the VSATs has the ability to communicate directly with any of the other VSATs.• Since the traffic can go to or from any VSAT, this architecture is referred to as a MESH network.• It will still be necessary to have network control and the duties of the hub can either be handled by one of the VSATs or the master control station functions can be shared amongst the VSATs.

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Satellite

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

Topology of a MESH VSAT network from the satellite’s perspectiveNote how all of the VSATs communicate directly to each other via the satellite without passing through a larger master control station (Hub).

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VSAT Community

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ADVANTAGES OF STARADVANTAGES OF STAR

Small uplink EIRP of VSAT (which can be a hand-held telephone unit) compensated for by large G/T of the Hub earth station

Small downlink G/T of user terminal compensated for by large EIRP of Hub earth station

Can be very efficient when user occupancy is low on a per-unit-time basis

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DISADVANTAGES OF STARDISADVANTAGES OF STAR

VSAT terminals cannot communicate directly with each other; they have to go through the hub

VSAT-to-VSAT communications are necessarily double-hop

GEO STAR networks requiring double-hops may not meet user requirements from a delay perspective

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ADVANTAGES OF MESHADVANTAGES OF MESH

Users can communicate directly with each other without being routed via a Hub earth station

VSAT-to-VSAT communications are single-hop.

GEO MESH networks can be made to meet user requirements from a delay perspective.

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DISADVANTAGES OF MESHDISADVANTAGES OF MESH

Low EIRP and G/T of user terminals causes relatively low transponder occupancy

With many potential user-to-user connections required, the switching requirements in the transponder will almost certainly require On-Board Processing (OBP) to be employed

OBP is expensive in terms of payload mass and power requirements

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Delay ConsiderationsDelay Considerations

Satellite Scenario:• Typical slant path range for GEO satellite: 36,000 km• One way transmission: ESSatelliteES: 2 x Range• One way delay: 2 x (range/velocity) = 260 ms

Fiber Optic Transcontinental Link: • 4000 km has about 13 ms delay

Additionally to either case: Processing delay.• Several tens to over a hundred ms.

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Satellite Network ConfigurationsSatellite Network ConfigurationsVSATVSAT

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Frequency-Division MultiplexingFrequency-Division Multiplexing

Alternative uses of channels in point-to-point configuration 1200 voice-frequency (VF) voice channels One 50-Mbps data stream 16 channels of 1.544 Mbps each 400 channels of 64 kbps each 600 channels of 40 kbps each One analog video signal Six to nine digital video signals

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Value of Satellite SystemsValue of Satellite Systems

• Value of satellite systems grows with widely distributed networks and mobility of users

• Satellite systems perform most effectively when: • interconnecting wide distributed networks,

• providing broadcasting services over very wide areas such as a country, region, or entire hemisphere

• providing connectivity for the “last mile” in cases where fiber networks are simply not available for interactive services.

• providing mobile wideband and narrow band communications

• satellites are best and most reliable form of communications in the case of natural disasters or terrorist attacks - fiber networks or even terrestrial

wireless can be disrupted by tsunamis, earthquakes, etc..

1 VSAT– the only viable solution for Rural Pakistan.

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Transcript of 1 VSAT– the only viable solution for Rural Pakistan.