| Knowledge Base - VSAT Terms and Acronyms |
Industry professionals use many technical terms and acronyms to describe the various components of VSAT hardware. Some commonly used terms follow.
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Hardware
| Term | Meaning |
| VSAT | Very Small Aperture Terminal, a satellite unit with a small antenna size, typically used to describe consumer-grade satellite hardware. |
| IDU | InDoor Unit, the VSAT component that is kept inside the customer's building. |
| CPE | Customer Premises Equipment, a term used by Tachyon Networks to refer to all hardware installed on a customer site, both indoor and outdoor. |
| IRU | Indoor Receive Unit, the top third of the DW4020 IDU. It receives the satellite signal. |
| ITU | Indoor Transmit Unit, the middle third of the DW4020 IDU. It transmits signal to the satellite. |
| Gateway | Part of the IDU that accepts IP traffic and converts it to the radio signal the satellite uses. The bottom third of the DW4020 IDU is a Gateway. Some VSAT units, such as the DW6000, have an gateway integrated into the IDU. Others, including most dedicated equipment, requires an external gateway router to perform this function. |
| ODU | OutDoor Unit, the VSAT component that is connected to the antenna, and does the actual work of receiving and transmitting ratio data from and to the satellite in orbit. See the following diagram:
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| LNB | Low-Noise Block down-converter, the receiver part of the ODU. |
| BUC | Block Up-Converter, the transmitter part of the ODU. |
| OMT | Ortho-Mode Transducer, part of the ODU that filters the Rx and Tx signals to ensure they are kept 90 degrees out of phase and therefore preventing interference between the two radio waves. |
| TRF | Transmit Reject Filter, part of the ODU that prevents the signal transmitted by the BUC from being detected by the LNB adjacent to it, which would degrade the received signal. |
| H-plane Bend | Bends the wave from the top of the TRF into the LNB. |
| IFL | Inter-Facility Link, the coaxial cable between the ODU and IDU. Two IFL cables are used - one for transmit (Tx) and one for receive (Rx). |
| Antenna | The round-angle reflector used to reflect and focus radio waves onto a point, where the ODU sits. Commonly called a "dish". |
| Feed Horn | A cone-shaped device which faces the antenna and directs signal into the ODU. It usually has a thick plastic layer on the large end, which prevents dust from entering the ODU. |
| Feed Support | A piece of metal which support the ODU and suspend it in front of the antenna. It connects from the bottom of the ODU to the bottom edge of the antenna. |
| Support Arms | Two metal supports which stabilize the feed support and ODU. They connect from the end of the feed support (where the ODU sits), to the sides of the antenna. |
| Az/El Head | Azimuth-Elevation Positioner Head, a device which attaches to the back side of the antenna and sits atop the dish stand. It adjusts left-right (azimuth) and up-down (elevation) of the dish. |
| Dish Stand | A metal pole with stabilizing legs that holds up the antenna. Consists of a kingpost (the main shaft) and legs. Also called a mount. |
| NPM | Non-Penetrating Mount, a dish stand designed to not require mounting on a flat service. Usually secured by sandbags or other weights. Advisable in situations when the mounting surface should not be damaged, but susceptible to high winds and other disturbances. |
Statistics
| Term | Meaning |
| SQF | Signal Quality Factor, a measure of received signal strength, measured between 0 and 99. This is a measure of radio quality, and does not affect network speed or bandwidth. |
| EbN0 | Receive signal-to-noise ratio, a measure of received signal quality and interference. This is a measure of radio quality, and does not affect network speed or bandwidth. |
| EsN0 | Transmit signal-to-noise ratio, a measure of transmitter signal quality and interference as measured at the Network Operations Center. This is a measure of radio quality, and does not affect network speed or bandwidth. |
Technology
| Term | Meaning |
| SCPC | Single Channel Per Carrier, another term for dedicated capacity, meaning a channel reserved entirely for one customer. |
| TDMA | Time Division Multiple Access, a digital transmission technology that allows a number of users to access a single radio-frequency channel without interference by allocating unique time slots to each user within each channel. This is the technology that makes shared-bandwidth satellite systems possible. |
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