Very Small Apeture Terminal (VSAT) Technical Brief

Comment: Several years ago, I was the leader of an operationalized telecommunication cell. The purpose of the cell was to monitor the effectiveness and readiness of the telecommunications in support of the ongoing operations. The staff regularly turned over due to the operational tempo and I had to train new staff quickly. I did so by preparing a series of technical briefs on topics the cell dealt with. This brief was dealing with VSAT which was used as independent telemetry feeding network performance back to the monitoring systems. Independent telemetry is important if operational bandwidth is unstable or unavailable. Over the VSAT we could assess if there was failing hardware or if an attack was underway affecting the operational bandwidth. 

Very Small Apeture Terminal (VSAT)
by 
JT Bogden, PMP

VSAT services have been growing in use. Numerous vendors offer services and equipment that make use of the VSAT in one way or another. Many nation-states have initiatives to place VSAT services into rural areas to improve communications and quality of life. The VSAT system data throughput ranges generally between 4 kbps up to 16 mbps and consist of several components; the satellite, a remote earth station, and a master earth station. The system extends a network's existing infrastructure through the satellite, Figure 1.

Figure 1: VSAT Architecture

This station has an outdoor unit (ODU) and an indoor unit (IDU). The ODU, Figure 2, includes the antenna and transceiver while the IDU, Figure 3, is configurable and supports integration with telephone systems, computer networks, and cellular networks. These components may be solar powered increasing the usefulness of the system in most any location.

Figure 2:  Outdoor Unit

Figure 3:  Indoor Unit

The Master Earth Station is the network control hub and is often co-located with major telephone network switches and the star network configuration is the most common associated topology.  At least three satellites are located in geosynchronous earth orbit about 35,400 KM above the equator spaced 120^o apart. Each satellite has coverage of about 40% of the Earth Surface. VSAT service is a lightweight and a relatively portable communication suite that may be powered by solar units or batteries. The ‘star’ network configuration has all traffic passing through a single point, a Master Earth Station which posses a few challenges:

• Satellite dishes can be flooded with electromagnetic energy overwhelming the signal.
• The network accounts can be hacked and tracked. 

Overall, the VSAT system provides low bandwidth and a reach into areas not possible without extreme costs.