A Tutorial on VSATs – Topic-3

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Advantages of VSATs

If by now you believe that VSATs provide an edge over terrestrial lines only in where the land lines are difficult to install, say in the case of remote locations, and then consider this. Close to 50 percent of the total VSAT population is installed in the US which also boasts of world’s best terrestrial communications.

Networking of business activities, processes and divisions is essential to gain a competitive edge in any industry. VSATs are an ideal option for networking because they enable Enterprise Wide Networking with high reliability and a wide reach which extends even to remote sites.

Last Mile Problem

Let us begin with the situation where you have reliable high-speed links between city exchanges for meeting your communication requirements. But before you begin to feel comfortable, connections from the nearest exchange to your company‘s office often comfortable, connections from the nearest exchange to your company’s office often fail. Consequently, stretching what is technically called the last mile problem into much longer distances. VASTs located at your premises guarantee seamless communication even across the last mile.

Reach

You must be well aware of the limitation faced by terrestrial lines in reaching remote and other difficult locations. VASTs on the other hand, offer you unrestricted and unlimited reach .

Reliability

Uptime of up to 99.5 percent is achievable on a VSAT network. This is significantly higher than the typical leased line uptime of approximately 80 to 85 percent.

Time

VSAT deployment takes no more than 4-6 weeks as compared to months for leased lines.

Network Management

Network monitoring and control of the entire VSAT network is much simpler then a network of leased lines, involving multiple carriers at multiple locations. A much smaller number of elements needs to be monitored incase of a VSAT network and also the number of vendors and carriers involved in between any two user terminals in a VSAT network is typically one. This results in a single point of contact for resolving all your VSAT networking issues. A VSAT NMS easily integrates end-to-end monitoring and configuration control for all network subsystems.

Maintenance

A single point contact for operation, maintenance, rapid fault isolation and trouble shooting makes things very simple for a client, using VSAT services. VSATs also enjoy a low mean time to repair (MTTR) of a few hours, which extends up to a few days in the case of leased lines. Essentially, lesser elements imply lower MTTR.

Flexibility

VSAT networks offer enormous expansion capabilities. This feature factors in changes in the business environment and traffic loads that can be easily accommodated on a technology migration path. Additional VSATs can be rapidly installed to support the network expansion to any site, no matter however remote.

Cost

A comparison of costs between a VSAT network and a leased line network reveals that a VSAT network offers significant savings over a two to three years timeframe. This dose not take into account the cost of downtime, inclusion of which would result in the VSAT network being much more cost- effective. Pay-by-mile concept in case of leased line sends the costs spiraling upwards. More so if the locations to be linked are dispersed all over the country. Compare this to VSAT s where the distance has nothing to do with the cost. Additionally, in case of VSATs, the service charges depend on the bandwidth which is allocated to your network in line with your requirements. Whereas with a leased line you get a dedicated circuit multiples of 64Kbps whether you need that amount of bandwidth or not.

VSAT System Architecture

A VSAT system consists of a satellite transponder, central hub or a master earth station, and remote VSATs. The VSAT terminal has the capability to receive as well as transmit signals via the satellite to other VSATs in the network. Depending on the access technology used the signals are either sent via satellite to a central hub, which is also a monitoring centre, or the signals are sent directly to VSATs with the hub being used for monitoring and control.

Topologies

The network of VSATs at different locations adopts different topologies depending on the end applications traffic flow requirements. These topologies could be star of Mesh. The most popular of these is star topology. Here we have a big, central earthstation known a s the hub. Generally the hub antenna is in the range of 6-11metre in diameter. This hub station controls, monitors and communicates with a large number of dispersed VSATs. Since all VSAT s communicate with the central hub station only, this network is more suitable for centralized data applications. Large organizations, like banks, with centralized data processing requirements is a case in point.

In a mesh topology a group of VSATs communicate directly with any other VSAT in the network without going through a central hub. A hub station in a mesh network performs only the monitoring and control functions. These networks are more suitable for telephony applications. These have also been adopted to deploy point to point high speed links.

However, in actual practice a number of requirements are catered to by a hybrid network topology. Under hybrid networks a part of the network operates on a star topology while some sites operate on a mesh topology.

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