Introduction

VSAT (Very Small Aperture Terminal) consists of a terminal with very small dimensions which is able to provide bi-directional communication connectivity. The VSAT technology provides value added satellite connectivity able to transport data for Internet/Intranet applications, Video and Voice over IP, and in general public or private networks.

Thanks to the flexibility, rapid deployment and low costs of set up and operations, the VSAT technology is used more and more in the deployment of networks for private, public/governmental, and corporate applications.

In all market sectors with crucial tasks and a highly reliable communication system is required, VSAT technology is used. The technology has been on the market for more than 20 years with millions of sites in operation worldwide. This makes the technology extremely reliable, and “beyond tested:” In addition, the Sat-com standard is extremely easy to integrate with other technologies based on wireless and wired systems.

The networks based on VSAT technology are of two main areas: the dedicated services and the shared ones. The shared services (TDMA) allow several remote stations to share the same network in time division. The dedicated services communicate within each other without the need of a hub and on single carrier per channel. Hereafter we have some examples on the typical dedicated and shared services and what the state of the art technology has developed further: Hubless and Star-Mesh topology networks.

Point-to-Point links (SCPC)

SCPC (Single Channel Per Carrier) is a satellite network topology which allows the connection of a specific single point to another specific single point without going through any other earth station. This technology is used when bulk data transfer is required, for example for data, voice and/or video transfer.

In this case the bandwidth is dedicated and not shared, and dedicated exclusively between the two stations which are connected in SCPC mode; the satellite link dimension can vary from a few Kbps to several Mbps, depending on the link budget specifications of the customer’s needs.

This network topology uses a Multiplexer standard, with a single SCPC Modem in each of the two locations. Thanks to multiplexing, there is a significant advantage in high throughput efficiency and reduced latency (unlike STAR hub-based networks). In addition, these types of links can be deployed in geographic areas regardless of the existence of an already present network or not.

Star Networks (TDMA)

TDMA (Time Division Multiple Access) is a satellite network topology that allows the implementation of a STAR network where all the remote stations are dynamically connected (in time division) via satellite to a central hub. Two (or several) remotes can still communicate with each other but it would be via the central hub with double the round trip delay.

This network topology is extremely flexible and cost effective, being the ideal choice for the type of networks that, like the SCADA networks, need to transmit real-time low bitrate information and/or bites of information which do not need to have real time features. Star Networks are also ideal when a group of remotes of different clients wish to share a dedicated chunk of capacity and/or when back up services for terrestrial lines are requested.

Point to Multi-Point (Mesh)

TDMA (Time Division Multiple Access) is a satellite network topology that allows several remote terminals to inter-communicate in a single hop and without having to pass via the central hub, reducing in half, the delay when compared to TDMA Star topology.

In the past, Mesh topology networks were only possible at a high price, however due to the lower efficiency (when compared to Star topology networks) of bandwidth, now new and more efficient modulation schemes and higher compression rates have drastically reduced the costs of such network topologies making them significantly more affordable.

The Mesh topology is mainly used for a group of multiple VSAT remote terminals which require real time (voice and video) applications across multiple sites, and the direct connectivity without double hop and thus minimizing delay time.

Multi-Point with Multi-Point and Star

This Network topology allows all the remotes to access internet/Intranet via the main Hub (in Star topology mode) and to communicate within (or with?) each other in single hop (In mesh topology mode) without having to pass by the main Hub (and therefore with the delay of a single hop), depending on the different IP classes pre-assigned to the single sub-networks.

This technology, exclusively developed by UHP Networks, allows different remote terminals to talk with each other or to the main hub seamlessly. Such an example would be a corporate network that needs several remotes to talk to each other for internal purposes and the same remotes accessing internet via the main hub.