Vsat Training

VSAT–viable solution for remote sites connectivity

BY:

Syed Khurram Iqbal NaqviSystem Architect O3B Networks

For Pakistan and Central Asia

VSAT (Very Small Aperture Terminal)

A Very Small Aperture Terminal (VSAT), is a two-way satellite ground station with a dish antenna that is smaller than 3 meters.

VSATs access satellites to relay data from small remote earth stations (terminals) to other terminals (in mesh configurations) or master earth station "hubs" (in star configurations).

Motivation to use VSAT

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

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

Emergency Situations

VS

Satellite Services & Applications

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

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

Direct-To-Consumer • Broadband IP • Digital Audio Radio• Interactive Entertainment• 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

Occasional Use Services• Newsgathering – First choice

for live coverage, providinghigh-bandwidth video links from remote locations to capture “breaking news”

• Program Delivery – Broadcasts from television networks and relayed via satellite

Users of Satellite Communications

Banking SectorData NetworksTelecommunications (Cellular) Power Production InfrastructureOil & Gas

Advantages Availability: anywhere—no limitations

Fast Deployment: Within hours!

Homogeneity: Same speed and SLA regardless of location

Multicast: broadcast schemes which allows broadcast at no additional cost

Few Points of Failure: just two on the earth!

Advantages (contd.)Reliability: reliable satellite transmission of data

between an unlimited number of geographically dispersed sites

Flexibility: expansion capabilities, unrestricted and unlimited reach.

Network Management: end-to-end monitoring and configuration control for all network subsystems.

A low mean-time to repair - lesser elements imply lower MTTR.

Disadvantages

Latency: round trip delay of 500ms or even more!

Cost of Bandwidth: high as compared to others!

Environmental concerns: “fading” due to rain/snow (frequency band dependent)

LOS dependency: outdoor antenna installation requires clear LOS.

Interference: common to all wireless media!

Comparison between Transmission Media

Optical Fiber

Microwave

Copper

VSAT

Satellite-Fiber ComparisonComparing 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

VSAT Vs. Leased Line VSAT

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

Leased LineOption not available in all areasLow initial investment Dependent on the capacity of the local

systemRecurring Bandwidth costs

“Typical” 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 nodes

Satellite Network ConfigurationsVSAT

Satellite Frequencies There are specific frequency ranges used by commercial satellites.

L-band (Mobile Satellite Services) 1.0 – 2.0 GHz

S-band (MSS, DARS ) 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

VSAT 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

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

Orbital 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.

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

Geostationary Orbit Today

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

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, complex antennas.

• Increased exposure to Van Allen Belt radiation

Transponders

• 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

Frequency 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.

Fixed Satellite Technology Options

TDM/TDMATraditional data VSAT

systemsLow cost remotes,

expensive hubStar network topologyTransactional data

Credit card validation/POS Internet …

Low user data rate

Freq

uenc

yTime

Satellite Technology Options

TDMA/DAMAStar/Mesh/Hybrid

networksMultimedia,

multiserviceEfficient space

segment utilizationEasily expand

network and site capability

Satellite Technology Options

Freq

uenc

y

Time

SCPC

DAMA Freq

uenc

y

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

Type of VSAT technology

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.

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

SCPC (single-carrier per channel)

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

Normally dedicated bandwidth of up to 2 Mbps

More than 2 Mbps can be acommodated with the use of different IDU/IDU.


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


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

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 RF 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).

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.

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 proportion 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.

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.

VSAT IMPLEMENTATION 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

VSAT Topologies 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.

VSAT STAR ARCHITECTURE

• 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.

VSAT STAR ARCHITECTURE (contd.)

Master Control Station (The Hub)

VSAT Community

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

STAR ARCHITECTURE (satellite’s perspective)

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.

VSAT MESH ARCHITECTURE

• 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.

VSAT MESH ARCHITECTURE

VSAT Community

MESH ARCHITECTURE (satellite’s perspective)

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).

VSAT Topologies--comparison

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 VSATsLower central hub investmentlarger VSAT antenna sizes (3.8 m typically)Higher VSAT costsSuited for high data trafficTelephony applications and point-to-point high-

speed links

Source: www.bhartibt.com

ADVANTAGES 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

DISADVANTAGES 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

ADVANTAGES 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.

DISADVANTAGES 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

Delay 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.

Value 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..

World Satellite Industry Revenues

$0

$20

$40

$60

$80

$100

1996 1997 1998 1999 2000 2001 2002 2003

Rev

enue

(in

billi

ons)

$38.0

$49.1$55.0

$60.4

$73.7$78.6

$86.1$91.0

Global Supply vs. DemandGEO Communications Satellites and Launches

0

10

20

30

40

50

60

70

1995 1996 1997 1998 1999 2000 2001 2002 2003

Num

ber o

f Sat

ellit

es/L

aunc

hes

Launches Satellites OrderedSatellite Capacity Launch Capacity

-

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01

VSAT: A Consistent Performer

Opportunities 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

Summary (of previous discussion)

Satellite 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.

Implementation

Requirement

Customers

Locations

Time Lines

Solution Details

Frequency Band

Outdoor Equipment

Indoor Equipment

Interfacing

Ground 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

Steps in Installation of a VSAT site

Technical Site Survey

Civil Work

Antenna Mounting

Pointing of Antenna

Configuration of ODU

Steps in Installation of a VSAT site

Configuration of Indoor Unit

Testing on RF level

Interfacing

BER testing

Integration (with the BTS/BSC)

Quality Assurance Tests

BER testing

Spectrum Analysis

Carrier to Noise Ratio measurement

Common Faults/Problems

Fading (due to rain etc.)

LOS obstructions

ODU/IDU malfunctions

De-pointing of Antenna

Interference

O & M Procedures

Carrier Monitoring

Spectrum Analysis

Fault Diagnosis/Localization

RF Power adjustment

etc. etc.

Thank You!