VSAT systems use small satellite dishes to provide internet access to remote locations. A VSAT consists of an outdoor unit with a reflector dish and indoor unit. VSATs use DVB-S2 and FD-TDMA technologies to share satellite bandwidth efficiently. They provide ubiquitous connectivity across wide areas and offer reliable service as an alternative or backup to terrestrial networks. While satellite connections have higher latency than terrestrial options, technologies like TCP spoofing can accelerate data transfer speeds. VSATs are commonly used to provide internet access for homes, businesses, mobile applications, and high availability networks where terrestrial options are limited.

1. VSAT Basics
Presenter: Dave Rehbehn

2. What Is A VSAT
Very Small Aperture
Terminal
• Refers to the size of the antenna
reflector
• VSAT is generally .74 meter up to 2.4
meter
VSAT (remote station) consists of:
Outdoor Unit (ODU):
• Reflector
• Transceiver (BUC and LNB)
IFL Cable
• Coax cable to connect IDU to ODU
Indoor Unit (IDU)
• Ethernet interface to LAN

3. VSAT Access Technologies
SCPC
(Single Channel Per Carrier)
F1
F2
DVB-S2(TDM)/FD-TDMA
DVB-S2
Forward
FD-TDMA
Return
Circuit Based Access Scheme
Mesh Topology (point to point)
Dedicated Bandwidth
Well Suited To High Capacity Links
Packet Based Access Scheme
Star Topology (point to multipoint)
Shared Bandwidth
Well Suited To Last Mile IP Access
DVBS2/FD-TDMA VSATs
Are The Biggest Part Of
The Market

4. VSAT Are IP Devices
Typical VSAT Is ActuallyA Hybrid Device:
Satellite Modem
Receives DVB-S2/ACM Forward Channel
Transmit FD-TDMA Return Channel
IP Router
Network/Port Address Translation
DHCP Server/Relay
DNS Caching
Routing Protocols
IP Header Compression
IP Payload Compression

5. Internet
Model
VSATs Generate Bandwidth Efficiencies
Satellite Bandwidth Is
Limited Resource
VSAT Systems
Maximize Efficiencies
Higher Layer Acceleration and Optimization through…
HTTP Prefetch
Application
Transport
Network
Data Link
Physical
TCP Spoofing, ACK Reduction, Selective
Retransmission
IP Header and Payload Compression
Lower Layer Efficiency through…
DVB-S2 with Adaptive Coding and Modulation
(Forward Channel)
Frequency Division/Time Division Multiple
Access (Return Channel)

6. Key Components For a VSAT Network
Satellite
Remotes
Hub or Gateway
Internet or
Corporate Network

7. Why VSAT
Ubiquitous
Uniform SLA and QoS Across Footprint
Simple Network Architecture
Independent of Terrestrial
Reliable
and Consistent
Scalable
and Manageable
Diverse
VSAT Complements Terrestrial Solutions To Enable
Services To Un-Served And Under-Served Areas

8. VSAT For Home
In North America, as of 2011, there are
over 1 million households using VSAT to
access the internet

9. VSAT For Business
Retail Banking
VSATs Used By
Enterprises For
Remote Connectivity
Oil Exploration
Primarily Used For
Locations Which Are
Underserved By
Terrestrial
Lottery

10. DSL
VSAT For High Availability
Remote Branch
VSAT
Satellite to Back Up Terrestrial
Satellite to Load Share Terrestrial
VRRP
with PBR
Corp HQ
MPLS
etc
Terrestrial
Satellite Enables True Path Diversity

11. VSAT For Mobility
Fly-a-way VSAT
Man Pack VSAT
On The Pause VSAT
Maritime VSAT
Aeronautical VSAT

12. Considerations To Satellite: Latency
Satellite Orbit ~ 35,000 km Above Earth
Physical Delay Is About 250 ms roundtrip
Protocol Processing Adds ~300-500 ms
Protocols Such As TCP Can Be
“Spoofed” or “Accelerated”
“spoofing”
Link Is Terminated At The VSAT
Enables Fast Startup and Fast
Transfer
HTTP Object Pre-Fetch Enables
Fast Delivery of HTTP Objects

13. Satellite Frequencies
Size of
Antenna
Impact of
Rain
Ka band 26.5 to 40 GHz
K band 18 to 26.5 GHz
Ku band 12 to 18 GHz
X band 8 to 12 GHz
C band 4 to 8 GHz
S band 2 to 4 GHz
L band 1 to 2 GHz

14. Considerations To Satellite: Rain Fade
Atmospheric Moisture Attenuates Satellite Signal
Effect Is Greater At Higher Frequencies (eg, Ku and Ka)
Rain Fade Mitigation Techniques:
Forward Channel
• DVB-S2 with Adaptive Coding and Modulation
• Uplink Power Control
Return Channel
• Adaptive Coding
• Symbol Rate Change
• Uplink Power Control

15. Future Of VSATs
1-5 Mbps
Significant increase
in throughput and
performance
9.6 kbps
1990 2000 2010
$$$$
Significant decrease
in cost of service
and hardware
$
1990 2000 2010
New Ka-Band Systems Promise To Provide More Bandwidth At Less Cost

16. VSAT Basics
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