Transcript satellite-final

VSAT– the only viable solution for
Rural Pakistan
1
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), multipointto-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 & Applications
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
Direct-To-Consumer
• Broadband IP
• DTH/DBS Television
• Digital Audio Radio
• Interactive Entertainment & Games
• Video & Data to handhelds
GPS/Navigation
• Position Location
• Timing
• Search and Rescue
• Mapping
• Fleet Management
• Security & Database Access
• Emergency Services
Remote Sensing
• Pipeline Monitoring
• Infrastructure Planning
• Forest Fire Prevention
• Urban Planning
• Flood and Storm watches
• Air Pollution Management
• Geo-spatial Services
Infrastructure / Support Services
Launch Vehicles Ground Equipment Insurance Manufacturing
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VSAT 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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VSAT Characteristic and Advantage
 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.
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Satellite-Fiber Comparison
Comparing Satellite and Fiber Characteristics
Capability
Transmission
Speed
Quality of
Service
Transmission
latency
System
Availability w/o
Backup
Broadcasting
Capabilities
Multi-casting
Capabilities
Trunking
Capabilities
Mobile Services
Fiber Optic
Cable
Systems
10 Gbps-3.2
Terabits/second*
-11
-12
10 10
Geo Satellite in a
Global System
Meo Satellite in a
Global System
Leo Satellite in a
Constellation
Single Sat
1 Gbps-10 Gbps
-6
-11
10 10
Single Sat
0.5 Gbps- 5 Gbps
-6
-11
10 10
Single Sat
.01 Gbps-2Gbps
-2
91
10 10
25 to 50 ms
250 ms
100-150 ms
25-75 ms
93 to 99.5%
99.98% (C- Ku band)
99% (Ka ban d)
99.9% (C- Ku band)
99% (Ka band)
99.5% (L-C- Ku band)
99% (Ka band))
Low to Nil
High
Low
Low
Low
High
High
Medium
Very High
High
Medium
Low
Nil
Medium-to-High
High
High
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“Typical” Fixed Satellite Network
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
Network HUB
Apartment
Buildings
Internet
Gas Stations
Branch Offices
Corporate Offices
Residential
Corporate Data
Center/HQ
Some large scale corporate networks have as many as 10,000 nodes
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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 – 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 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)
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 Today
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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)
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 lowergain, quasi-omni antennas.
• Increased exposure to Van Allen Belt radiation
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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
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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.
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World Satellite Industry Revenues
$91.0
$86.1
$78.6
$73.7
$60.4
$55.0
$49.1
$38.0
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World Satellite Services Revenue
$55.9
$49.1
$ 46.5
$ 39.2
$ 29.7
$ 21.1
$ 24.4
$15.8
FSS $
MSS $
DBS $
6.1
0.7
9.0
$ 6.8
$ 0.8
$ 13.5
$ 7.3
$ 1.0
$ 16.1
$ 8.6
$ 1.3
$ 19.8
$ 9.2
$ 2.1
$ 27.9
$
$
$
8.9
1.4
36.2
$
$
$
8.7
1.3
39.1
$
$
$
9.6
1.7
44.7
FSS=VSAT services, remote sensing, and transponder leasing
MSS=Mobile telephone and mobile data
DBS/DARS=DTH TV, DARS, and Broadband
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World Ground Equipment Revenues
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. Demand
GEO Communications Satellites and Launches
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Number of Satellites/Launches
60
50
40
30
20
10
0
1995
1996
1997
1998
Launches
Satellite Capacity
1999
2000
2001
Satellites Ordered
Launch Capacity
2002
2003
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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
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Critical to Flow of Information
• Newsgathering – First choice
for live coverage, providing
high-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 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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VSAT: A Consistent Performer
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
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VSAT Vs. Leased Line
 VSAT
 Footprint across the country
 High initial investment
 High reliability – Uptime of 99.5%
 No recurring b/w costs
 Leased Line
 Option available only at areas with an
existing VSAT hub
 Low initial investment
 Dependant on the Local Hub
 Recurring Bandwidth costs
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DVB - RCS
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DVB-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-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 Options
TDM/TDMA
Traditional data VSAT
systems
Low cost remotes,
expensive hub
Star network topology
Transactional data
 Credit card validation/POS
 Internet …
Frequency
Low user data rate
Time
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Fixed Satellite Technology Options
SCPC/MCPC (FDMA, Frequency divided
multiple access)
Frequency
Point-to-Point
IDR –
DCME(compression)
Gateways
Uplinks
Fixed bandwidth
Broadcast
Audio/Video
Static traffic patterns
Time
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SCPC / 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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Fixed Satellite Technology Options
SCPC/DAMA
Frequency
Centralized Net Mgmt
Star and Mesh
Low cost remotes
One modem/Interface
per channel
Large gateways
required
Time
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SCPC / 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 Options
TDMA/DAMA
Star/Mesh/Hybrid
networks
Multimedia,
multiservice
Efficient space
segment utilization
Easily expand
network and site
capability
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SCPC
Frequency
Satellite Technology Options
DAMA
Frequency
Time
Time
Sample when a SCPC system is cost-effective
Sample when a DAMA system is cost-effective
If is a number of sites in a VSAT Network
One block = 64 Kbps
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Summary
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.
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Type 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 technology
TDMA
Time-division
Multiple Access
VSAT
TECHNOLOGY
SCDC
Single-carrier
per Channel
FDMA
Frequency Division
Multiple Access
PAMA
Pre-Assigned
Multiple Access
FDMA
DAMA
Demand Assigned
Multiple Access
CDMA
Code Division
Multiple Access
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VSAT 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)
 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)
Copyright Maxis
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.
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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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SCPC (single-carrier per channel)
Copyright Maxis
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.
43
SCPC (single-carrier per channel)
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.
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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)
 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)
 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)
 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 technology
 Voice over IP (VoIP) via satellite
 Frame Relay via satellite
 ATM via satellite
 Video-on-demand via satellite
 Multimedia application
 Internet/e-mail connection
 Telemedicine
 Distance learning
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VSAT: A Consistent Performer
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
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Users of Satellite
Communications
 Banking Sector
 Data Networks
 Telecommunications (Cellular)
 Power Production
 Infrastructure
 Oil & Gas
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Motivation to use VSAT
VS






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.)
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VSAT IMPLEMENTATION - 2
 There are basically two ways to implement
a VSAT Architecture
 STAR
 VSATs are linked via a HUB
 MESH
 VSATs are linked together without going
through a large hub
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VSAT IMPLEMENTATION - 3
Higher Propagation delay
Used by TDMA VSATs
High central hub investment
Smaller VSAT antenna sizes (1.8 m typically)
Lower VSAT costs
Ideally suited for interactive data applications
Large organizations, like banks, with centralized
data processing requirements
Source: www.bhartibt.com
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 highspeed links
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Basic Topologies
Point to Point (SCPC)
Earth station
with terrestrial
tail or
customer
located
antenna
Point to Multipoint (TDMA)
Customer
located
antenna
Earth Station
with terrestrial
tail to customer
premises
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VSAT 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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VSAT STAR ARCHITECTURE - 2
All communications to and
from each VSAT is via the
Master Control Station or
Hub
Master Control Station
(The Hub)
VSAT
Community
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VSAT STAR ARCHITECTURE - 3
VSAT
VSAT
Satellite
HUB
VSAT
VSAT
VSAT
Topology of a STAR VSAT network viewed from the satellite’s perspective
Note how the VSAT communications links are routed via the satellite to the
Hub in all cases.
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VSAT 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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VSAT MESH ARCHITECTURE - 3
VSAT
VSAT
VSAT
VSAT
Satellite
VSAT
VSAT
VSAT
VSAT
VSAT
VSAT
Topology of a MESH VSAT network from the satellite’s perspective
Note 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 MESH ARCHITECTURE - 2
VSAT
Community
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ADVANTAGES OF STAR
 Small uplink EIRP of VSAT (which can be a handheld 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 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 MESH
 Users can communicate directly with each
other without being routed via a Hub earth
station
 VSAT-to-VSAT communications are singlehop.
 GEO MESH networks can be made to meet
user requirements from a delay
perspective.
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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
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Delay Considerations
Satellite Scenario:
• Typical slant path range for GEO satellite: 36,000 km
• One way transmission: ESSatelliteES: 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 Configurations
VSAT
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Frequency-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 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..
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