VERY SHORT APERTURE TERMINAL (VSAT)
VERY SHORT APERTURE TERMINAL (VSAT)
- VSAT is an earthbound software-driven station used in satellite communications of data, voice and video signals, excluding broadcast television.
- It consists of two parts, a transceiver/outdoor unit (ODU) that is placed outdoors in direct line of sight to the satellite and a device that is placed indoors to interface the transceiver with the end user’s communications device, such as a PC.
- The transceiver receives or sends a signal to a satellite transponder in the sky. The satellite sends and receives signals from a ground station computer that acts as a hub for the system.
- Each end user is interconnected with the hub station via the satellite, forming a star topology. The hub controls the entire operation of the network.
- For one end user to communicate with another, each transmission has to first go to the hub station that then retransmits it via the satellite to the – other end user’s VSAT.
- The majority of VSAT antennas’ diameter range from 75 cm to 1.2 m. The data rates typically range from 56 kbit/s up to 4 Mbit/s. VERY SHORT APERTURE TERMINAL (VSAT)
- With its star configuration network architecture, interactive VSAT technology is appropriate for any organization with centralized management and data processing.
- This configuration has been developed to minimize overall lifetime costs for the complete network including satellite transmission costs.
- The use of a single high performance hub allows the use of low cost remote VSAT terminals and optimizes use of satellite capacity.
- Even so, in most VSAT networks, the cost of the VSAT terminals usually far exceeds the cost of the hub (typically a VSAT terminal is 0.1 to 0.2% of the price of the hub).
ADVANTAGES / BENEFITS OF VSAT SATELLITE NETWORKS:
Access in Remote Locations:
- A Satellite in the Geo Synchronous orbit can cover around 33% of the earth’s surface and can provide connectivity to any region covered by it.
- This is very useful for remote locations (rural areas, ships and coastal regions, hills, etc) where there is limited or no terrestrial connectivity.
- Remote locations can be provided health services (telemedicine), educational facilities (distance education), etc. using VSAT.
- A VSAT Network can provide Internet access in addition to the point to point WAN links.
- It’s all set to create a next major wave in the consumer broadband industry with the launch of satellites operating in the Ka band offering very high throughput, especially in the non metro regions.
- ‘Always ON’ broadband Internet services are possible with VSAT networks.
- Once the Satellite is put in to its orbit, the deployment at the customer premises can be done (usually in hours) if the equipment is available, with minimum training. And the deployment can be done in any region, irrespective of where it is located.
- Satellites support encryption of all data transmitted between two sites or multiple sites, which make the creation of Virtual Private Networks (VPN) possible.
- Thus VSAT networks could find more acceptance in the corporate and Government/ Defence connectivity requirements.
Quality of Service (QoS):
- VERY SHORT APERTURE TERMINAL (VSAT) Networks support QoS and Layer 2 prioritization policies to be applied across the WAN link which enables real time applications to be deployed across the network.
- This makes TV broadcasters make broadcasts from anywhere — even when they are on the move.
- Another possible application could be mobile Internet access, while on the move.
- VSAT networks can be easily and cost effectively be scaled to accommodate multiple locations across the globe.
Cost: [VERY SHORT APERTURE TERMINAL (VSAT)]
- Though the initial investment (service provider perspective) might be high in terms of the cost of satellites and putting them in the orbit, the running cost (end point terminals and ongoing subscription) is coming down rapidly — That’s why applications like Direct To Home (Cable TV) are broadcasted directly from satellites to homes at a reasonable cost to the subscriber.
- Satellite Networks are very reliable (having up-times in the magnitude of 99.5% and above) and have been field tested for many years now.
- Mission critical applications like Bank ATM’s. Navy and Point of Sale appliances use VSAT.
Back-up to Terrestrial Networks:
- VSAT networks have always found applications in this area — they make a good back up network to the terrestrial networks (Leased Lines, MPLS circuits, Broadband DSL Connectivity, Internet Leased Lines, etc) and there are certain customized plans available for backup exclusively with satellite service providers that charge for only 5% of the monthly capacity when the VSAT connection is used exclusively for backup.
- VSAT networks are not affected by natural calamities like earthquakes, storms etc.
- Satellite transmissions are single hop (mostly) when compared to the multiple hops that the communications based on terrestrial networks need to take to reach to their destination.
- Some factors like router performance etc, depends on multiple service providers and hence end to end QoS may not be possible with terrestrial public networks.
Bandwidth on Demand:[VERY SHORT APERTURE TERMINAL (VSAT)]
- VSAT networks support and are better suited for Bandwidth on Demand services than their terrestrial counterparts.
Cost per connection is independent of the location/ distance:
- With a VSAT network, the cost per node is independent on the number of nodes and also distance between the various nodes.
- Compare that with Leased Lines, where the cost increases with more nodes and distance between the two locations.
LIMITATIONS [ VERY SHORT APERTURE TERMINAL (VSAT)]
- extremely high initial cost needed for building and launching satellites in the Geo-Synchronous orbit
- Bit Error Rate is common for satellite based technologies
- Rain Attenuation might affect the performance of VSAT communications under rainy conditions
- latencies (>200 ms) are still higher than their terrestrial equivalent technologies (<100 ms)
- careful direction of subscriber side terminals and dish antennas are critical for proper working
- trained man power is required for installation and maintenance
- other competitive technologies (Internet Leased Lines, 3G/HSDPA/4G – Cellular technologies etc) offer much higher bandwidth at a lower cost than
what is possible by VSAT based networks
- the antennas need to be fixed outside the offices or homes hence making them susceptible to damage or theft. [VERY SHORT APERTURE TERMINAL (VSAT)]