Tuesday 5 July 2011

How does a VSAT work?

---------------------
A VSAT network has three components:
A central hub (also called a master earth station)
---------------------------------------------------
The satellite
------------------------------
A virtually unlimited number of VSAT earth stations in various locations - across a country or continent

Content originates at the hub, which features a very large -15 to 36-foot (4,5 -11m)- antenna.
The hub controls the network through a network management system (NMS) server,
which allows a network operator to monitor and control all components of the network.
The NMS operator can view, modify and download individual configuration information to the individual VSATs.

Outbound information (from the hub to the VSATs) is sent up to the communications satellite's transponder,
which receives it, amplifies it and beams it back to earth for reception by the remote VSATs.
The VSATs at the remote locations send information inbound (from the VSATs to the hub) via the same satellite transponder to the hub station.

This arrangement, where all network communication passes through the network's hub processor, is called a "star" configuration, with the hub station at the center of the star.
One major advantage of this configuration is that there is virtually no limit on the number
of remote VSATs that can be connected the hub. "Mesh" configurations also allow for direct communication between VSATs.

For satellites to gain a foothold in the delivery of advanced broadband services,
seamless interconnectivity with terrestrial networks is imperative.
For best results, the network should be designed to exploit the unique
virtue of satellite in geostationary orbit, namely that it can be a shared
resource available, as needed, to many users spread over a very large
proportion of the Earth's surface. This is the concept of bandwidth-on-demand.
In an ideal network, each terminal communicates with all others (full-mesh connectivity),
but utilises satellite capacity only on an as-needed basis. Such an architecture can be
implemented if the terminals operate in a Time Division Multiple Access (TDMA) mode (transmit in bursts)
and are capable of doing this at a variety of different frequencies
(FDMA and TDMA).
-----------------------------------------------------------------------------------
The DAMA System (Demand Assigned Multiple Access)
-----------------------------------------------------------------------------------
A DAMA system is typically a mesh network that allows direct connection between any two nodes in the network,
sharing the bandwidth of a satellite transponder space which can be allocated to each remote terminal as required.
DAMA supports full mesh, point-to-point or point-to-multipoint communications
 - any user can connect directly to any other user anywhere within the network
- and the most superior systems achieve this with TDMA.

The result is economical and flexible bandwidth sharing with any mix of voice, fax, video and data traffic.
The key point is that DAMA optimises the use of satellite capacity by allocating satellite resources to each
active node upon demand. By using a DAMA system, satellite resources can support a very much larger number of
users than a Single Channel Per Carrier (SCPC) system.
=====================================================


















Your Ad Here





No comments:

Post a Comment