1 of 36

Very Small Aperture Terminal (VSAT)

Shouvik Chakraborty

Lecturer in Computer Science & Technology

Women’s Polytechnic, Chandernagore, Govt. of West Bengal, India

shouvikchakraborty51@gmail.com / sccseku17@klyuniv.ac.in / shouvikchakraborty@ieee.org https://sites.google.com/site/shouvikchakrabortycse/

2 of 36

3 of 36

4 of 36

5 of 36

Introduction

  • The old earth stations and antennas were large sizes.
  • The Satellite was suffering from weak transmission and the impact of higher noise on the ground stations.
  • So the receiving stations must be large size and complex installation.
  • These satellites have developed

and become a high transmitter.

  • So the ground stations changed

to small size Stations with less

expensive and less complex and

called VSAT.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

6 of 36

What is a VSAT?

  • A very small aperture terminal (VSAT) is a small telecommunication earth station that receives and transmits data, video or voice via satellite.
  • The "very small" component of the VSAT acronym refers to the size of the VSAT dish antenna-typically about 60 cm to 3.8 m.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

7 of 36

Components of VSAT

It has two basic components:

  • Ground Segment (earth segment), which is divided into:

- Outdoor Unit (ODU), which contains the antenna.

    • Indoor Unit (IDU), which contains the interface between the VSAT and the customer’s

Equipment (PCs, TVs,

Telephones).

​

  • Space Segment namely

satellite.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

8 of 36

Uplink & Downlink

VSAT uses different frequencies:

    • Ku-band frequency: is usually used in North America and Europe by using small VSAT antenna with uplink frequency about 18 GHz and downlink around 12 GHz.

​

    • C-band frequency: is usually used in Asia, Africa and South America and operating with much larger antenna, with uplink frequency around 6 GHz as for downlink frequency around 4 GHz.

​

    • The new Ka-band frequency: is typically in the downlink frequencies up to 22 GHz and uplink frequencies up to 31 GHz.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

9 of 36

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

​

​

​

Band

Up-Link (GHz)

Down-Link (GHz)

Notes

L

.9-1.6

.9-1.6

Shared with terrestrial

S

1.610-1.625

2.483-2.5

Shared with ISM Band

C

3.7-4.2

5.925-6.425

Shared with terrestrial

Ku

11.7-12.2

14-14.5

Attenuation due to rain

Ka

17.7-21.7

27.5-30.5

High Equipment cost; attenuation due to rain

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

10 of 36

Bit Rate/Symbol Rate�

  • If more bits can be sent with each symbol, then the same amount of data can be sent in a narrower spectrum
  • For 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

​

Symbol Rate =

Bit Rate

# of bits transmitted with each symbol

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

11 of 36

VSAT Bandwidth�

  • The bandwidth of VSAT is referred as total frequency allocation allocated to any VSAT at RF center frequency by RF engineers. For example, if IF frequency allocated to VSAT is 71.02 MHz and there are 1 voice and 1 data channels operating at 19.2 Kbps and 9.6 kbps respectively are used.

​

  • Here total VSAT Bandwidth is (19.2 + 9.6) = 27.8 KHz provided 1 bit is used per carrier (i.e. BPSK modulation is employed).

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

12 of 36

Technology used by VSAT services

  • Time Division Multiple Access (TDMA)
  • Single Carrier Per Channel (SCPC)
  • Frequency Division Multiple Access (FDMA)
    • Pre-Assigned Multiple Access (PAMA)
    • Demand Assigned Multiple Access (DAMA)
    • Code Division Multiple Access (CDMA)

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

13 of 36

The satellites that are used in the VSAT system?

  • VSAT system used geostationary earth orbit (GEO) satellites that revolve around the equator at almost the equivalent rotational speed as the earth.

​

  • Appearing as though they are not moving at all, GEOs are always in the same place above the earth. They also cover a large geographic area.

​

  • Distance from earth: 36,000 km (22,282 miles).

​

  • Speed: 11,300 Km/h.

​

  • Located approximately every

2o above the equator

​

  • Average 14-17 Year Lifespan

​

  • Single Satellite theoretically can

provide up to 42% Earth Coverage

​

​

​

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

14 of 36

The satellites that are used in the VSAT system?

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

15 of 36

Indian Geo Satellites

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

  • The Indian National Satellite System or INSAT, is a series of multipurpose geostationary satellites launched by ISRO to satisfy the telecommunications, broadcasting, meteorology, and search and rescue operations.

​

  • Commissioned in 1983, INSAT is the largest domestic communication system in the Indo-Pacific Region.

​

  • It is a joint venture of the Department of Space, Department of Telecommunications, India Meteorological Department, All India Radio and Doordarshan.

​

  • The overall coordination and management of INSAT system rests with the Secretary-level INSAT Coordination Committee.

​

​

​

INSAT 1B

16 of 36

The Clarke Belt

  • An orbit 22,245 miles (35,800 kilometers) above the equator in which a satellite travels at the same speed that the earth rotates.

​

​

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

17 of 36

VSAT Advantages:

  • High flexibility to increase the size of the network in the future.
  • Able to integrate large number of the networks.
  • Cover distant geographical locations.
  • Ability to handle Voice, Video and Data.

VSAT Disadvantages:

  • Requires clear line of sight between dish and satellite.
  • Outages in some cases, because of the weather. These outages normally last for a few minutes.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

18 of 36

VSAT Network Topologies

  • The connection between Terminal and Terminal called (Point to Point).
  • The connection between Hub and Terminals called (Point to Multipoint).

​

​

​

​

  • The most important types of link are:
    • Star Topology.
    • Mesh Topology.

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

19 of 36

VSAT Point to Point

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

20 of 36

VSAT Point to Multipoint

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

21 of 36

VSAT Point to Multipoint

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

22 of 36

Star Topology

  • VSAT terminals cannot communicate directly with each other, they have to go through the hub.
  • It is commonly used for internet connection purpose.
  • Smaller VSAT antenna sizes (1.8 m typically).
  • The performance of the network is directly dependent on the performance of the hub.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

23 of 36

Mesh Topology

  • This network enables direct communication from one point to another.
  • Its usually found in telephone and data lines.
  • larger VSAT antenna sizes (3.8 m typically).
  • If one of the components fails there is another line.

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

24 of 36

VSAT Advantages

  • Full or partial independence from terrestrial infrastructure
  • Cost savings over terrestrial lines
  • Nationwide reach, distance-independent
  • Network management from a single point
  • Quick deployment, network flexibility
  • Consistent and rapid response time
  • Increased network availability �and reliability
  • Inherent broadcast / multicast platform

​

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

25 of 36

Unicast, Multicast, Broadcast

  • Each Unicast Packet is Numbered and Acknowledged

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

26 of 36

Unicast, Multicast, Broadcast

  • Multicasts Packets are Not Acknowledged
  • Different Data Steams can be sent simultaneously to many users

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

27 of 36

Unicast, Multicast, Broadcast

  • Broadcast Packets are sent to all users in the Network Simultaneously
  • Broadcasts are Not Acknowledged
  • VSAT Networks can use Reliable Broadcast Protocols and applications

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

28 of 36

VSAT Network Architectures�One Way

  • One-Way – Receive Only
    • High Bit-Rate DVB Compliant Outbound
    • Inbound Return Channel via Dial-Up Modem
    • Can be used with existing infrastructure
  • Example: Harmonic’s CyberStreamTM

​

​

Satellite

Router

Internet

RFT

IP Encapsulator

DVB Modulator

VSAT TVRO Antenna

DVB Receiver

LAN

Modem/ISDN Return

Baseband Equipment

TCP/IP ACK’s NACK’s

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

29 of 36

VSAT Network Architectures�Two-Way Star Topology

  • All VSATs Communicate via a Single Hub
  • Network is Independent of Existing Infrastructure
  • VSAT Antenna Size dependent upon Power and Gain of Hub Antenna
    • Also Upon Inbound Bitrate, ODU Power and Satellite Footprint
  • Contention Based Access – Usually TDMA or FTDMA
  • Typical Ping Times Approximately 650-700ms

​

​

​

Hub

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

30 of 36

VSAT Network Architectures�Two-Way Star Topology – Double Hop

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

31 of 36

VSAT Network Architectures�Two-Way Mesh Topology

  • VSATs communicate directly with each other
  • Some systems require initial signaling via the Hub
  • Larger Antennas, Higher Power required at the VSAT
  • Smaller Antenna, Lower Power required at the Hub
  • Used extensively in Telephony Networks
  • Delay minimized on VSAT to VSAT Calls

​

​

​

VSAT

VSAT

VSAT

VSAT

VSAT

VSAT

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

32 of 36

Typical VSAT Indoor Unit�(Skystar 360E)

(Front)

(Rear)

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

33 of 36

Typical VSAT Outdoor Unit/Antenna

LNB

Reflector

LNB-F (Optional)

(Front)

(Rear)

Feed-Assembly

SSPA (HPC)

LNB-F (Optional)

LNB

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

A low-noise block downconverter (LNB) is the receiving device mounted on satellite dishes, which collects the radio waves from the dish and converts them to a signal which is sent through a cable to the receiver inside the building. Also called a low-noise block, low-noise converter (LNC), or even low-noise downconverter (LND), the device is sometimes inaccurately called a low-noise amplifier (LNA).

Low-noise block feedhorns (LNBFs): In particular, the feedhorn (which gathers the signal and directs it to the LNB) and the polarizer (which selects between differently polarized signals) were combined with the LNB itself into a single unit, called an LNB-feed or LNB-feedhorn (LNBF), or even an "Astra type" LNB. The prevalence of these combined units has meant that today the term LNB is commonly used to refer to all antenna units that provide the block-down conversion function, with or without a feedhorn.

SSPA stands for Solid State Power Amplifier. Amplifiers, irrespective of their types, are used to enhance the amplitude of the radio frequency received by the satellite antennas. Specifically used in satellite communication technology, it is an active device that drives the transmitter.

34 of 36

VSAT Markets

  • Enterprise
    • Retail; Oil & Gas; Banking; Government
    • POS; Back Office; Browsing; Telemetry
  • Telephony
    • Public: Public Call Offices, small businesses, farmers, private lines
    • Corporate: Telephony/Data infrastructure
  • Internet (IP)
    • High-speed, always-on, Internet-access for consumers, small businesses and schools
    • Intranet and IP infrastructure for the enterprise
    • IP multicast-based services
      • Content delivery

​

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

35 of 36

  • Summary
  • VSAT is a perfect solution in answering voice, data and video, especially in the absence of terrestrial transmission coverage.

​

​

  • Utilizing VSAT offers maximum benefit, which enables company to expand very fast without affected by lack of local telecommunication network infrastructure.

​

​

  • VSAT is available anywhere in the Kingdom with the ability to connect remote areas.

​

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT

36 of 36

Thank You

S. CHAKRABORTY, Lecturer in CST

WPC

VSAT