Post on 02-Sep-2015
description
Satellite Communication
Course Instructor: Dr. Safdar Ali
VSAT
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
INTRODUCTION
The first earth station antennas used in commercial
satellite communications systems were very large
and expensive, with typical aperture diameters of
30m.
These antennas operated in C band (6/4 GHz).
With the rapid expansion of satellite
telecommunication world, there was a need to
make access to the satellite more affordable.
INTRODUCTION
This came about in two ways:
A significant increase in the transmit power
capabilities of satellites and the move to
frequency band above C band.
Both led to a rapid decrease in size and cost of
the earth station.
Most VSAT systems operate in Ku band, with earth
station antenna diameters of 1 to 2 m and
transmitter powers of 1 or 2 W.
INTRODUCTION
VSAT systems are used to link businesses and
stores to a central computer system so that sales
transactions can be completed more rapidly than by
using a telephone line and modem, and so that a
central office can rapidly distribute and collect
information from a large number of locations in a
region or country.
The earth stations are usually organized in a star
network, in which the earth stations connect to a
central HUB station via a GEO satellite.
VSAT
The underlying concept
behind most VSAT systems
is to bring
telecommunication service
directly to the end user
without any intermediate
distribution hierarchy.
VSAT are small, software-
driven earth stations.
It is used for the reliable
transmission of data, video,
or voice via satellite.
VSAT FOR MOBILITY
Fly-a-way VSAT
Man Pack VSAT
On The Pause VSAT
Maritime VSAT
Aeronautical VSAT
VSAT FOR HOME
In North America, as of 2011, there are
over 1 million households using VSAT to
access the internet
VSAT FOR BUSINESS
Retail Banking
Oil ExplorationLottery
VSATs Used By
Enterprises For
Remote Connectivity
Primarily Used For
Locations Which Are
Underserved By
Terrestrial
VSAT FOR HIGH AVAILABILITY
Terrestrial
VSAT
Remote Branch
Corp HQ
Satellite to Back Up Terrestrial
Satellite to Load Share Terrestrial
Satellite Enables True Path Diversity
VSAT RELIABILITY
VSAT technology often
high availability &
reliability it is accuracy
reaches to 99.6 to
99.7percentage
For the total VSAT
network. BER(bit error
rate) is better than
1error in 10 million
transmitted bits
BLOCK DIAGRAM OF VSAT
BLOCK DIAGRAM OF VSAT
ODU & antenna provide RF conversion and amplification for the satellite downlink &uplink
ODU called transceiver
In up link we use(up converter)
In down link we use (LNA & down converter)
IDU provide modulation & demodulation
From IDU we can obtain service we need (data-telephone-fax)
IDU AND ODU
VSAT HUB NETWORK
HUB
Information is produced at the hub having a very large 15to 36 foot antenna. The hub controls and monitors thenetwork through a network management system (NMS).Information is sent up to the communication satellite whichreceives, amplifies and beams it back to earth for receptionby the remote VSATs.
17
MULTIPLE ACCESS TECHNIQUES
PAMA (Pre Assigned Multiple Access)
PAMA is an access scheme where in when twoVSATs want to communicate with each other abandwidth is pre-assigned to them exclusively.This assigned bandwidth will be available to theVSAT's on a permanently basis.
MULTIPLE ACCESS TECHNIQUES
DAMA (Demand Assigned Multiple Access) This scheme is very similar to a telephone connection. Therole of the telephone exchange is to connect you to thedesired number. Remotes request a time slot or afrequency to transmit their traffic. The Hub plays therole of a telephone exchange, between any two VSAT's.
NMS allocates each remote a time slot or a frequency totransmit this traffic.
The attributed frequency or time slot will not be releaseduntil the end of the transmission. The hub plays the role ofa telephone exchange, between any two VSAT's.
The DAMA service addresses point to point voice, fax, anddata communication requirements of remote sites.
NETWORK ARCHITECTURES
One Way Implementation
Split Two Way (Split IP) Implementation
Two Way Implementation
ONE WAY IMPLEMENTATION
This is the mode of a satellite used in the broadcast
satellite services (BSS).
By means of proprietary software in the user
terminals, different parts of the downlink can be
accessed by different subscribers according to the
programs ordered from the supplier.
ONE WAY IMPLEMENTATION
This form of channel selection is called narrowcasting.
There can be many narrowcasting groups within a larger
broadcasting area.
SPLIT TWO WAY (SPLIT IP) IMPLEMENTATION
This implementation is used when there is no
normal return channel as with Ku band broadcast
satellite service systems that carry Internet traffic.
The relatively high capacity downlink stream is not
complemented by an uplink capability from the user
terminal.
If the BSS downlink is used as the download
channel from an internet service provider, the only
option the user has for a return link is via another
telecommunications channel, such as standard
telephone line.
SPLIT TWO WAY (SPLIT IP) IMPLEMENTATION
Terrestrial
VSAT
Remote Branch
Corp HQ
SPLIT TWO WAY (SPLIT IP) IMPLEMENTATION
The Internet Protocol (IP) is therefore split between
a satellite downlink (outbound) channel and a
terrestrial telephone (inbound, or return) channel;
hence the term split IP for this implementation.
The advantage of this approach is that the VSAT
terminal does not require a transmit capability,
which significantly reduces its cost and complexity.
The disadvantage is that the telephone line
connection bit rate is (56 kbps Modem)
TWO WAY IMPLEMENTATION
In this case, a return link is designed into the
service so that two way communications can be set
up over the same satellite, from the hub to the user
and from the user back to the hub.
Two way implementation can be:
Star
Mesh
TWO WAY IMPLEMENTATION
TWO WAY IMPLEMENTATION
Initially, the most common VSAT architectures were
Star networks since the very low receive G/T (gain
to noise temperature ratio) of the VSATs, coupled
with their limited transmit EIRP, was compensated
for by using a large hub with high G/T and EIRP.
TWO WAY IMPLEMENTATION
TWO WAY IMPLEMENTATION
The cost of the hub was quite high and, at least for the smaller VSAT networks, somewhat prohibitive. This led to the concept of a shared hub, where several networks operate through one main hub.
The difficulty with this approach for large countries with widely dispersed communities is that the host computers for the small VSAT networks are rarely close to the hub.
A high speed terrestrial data link is required between the host computers of the networks and the hub, which increases the cost of the network.
TWO WAY IMPLEMENTATION
Another star topology limitation is the delay for
VSAT to VSAT communication as we take two hops
In mesh topology allow terminals to communicate
each other directly.
The VSAT terminals is equipped with the network
management and control equipment, each VSAT
must have sufficient power and receive sensivity
(G/T) to communicate with every other VSAT .
Mesh topology requires larger antennas than star
topology
SATELLITE FREQUENCIES
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
Size of
Antenna
Impact of
Rain
VSAT BANDS
Currently we use two frequency bands: C-band and
Ku-Band.
For C-band operations, the antennas transmit at 6
GHz and receive at 4 GHz.
Ku-band requires transmission at 14 GHz and
reception at 11-12 GHz
KU-BAND VS. C-BAND
OBTAINING SATELLITE DETAILS
HTTP://WWW.LYNGSAT.COM
OBTAINING SATELLITE DETAILS
HTTP://WWW.LYNGSAT.COM
SATELLITE DETAILS AMOS 1HTTP://WWW.SPACECOM.CO.IL/
Middle East Beam
SATELLITE DETAILS AMOS 1HTTP://WWW.SPACECOM.CO.IL/
European Beam