Glossary of Terms and acronyms

Backhaul:
A terrestrial communications channel linking an earth station to a local switching network or population Center. Sometimes used to describe a point to point satellite link taking a TV signal to a studio or to an uplink station for transmission as a broadcast channel.

Bandwidth:
A measure of spectrum (frequency) use or capacity. For instance, a voice transmission by telephone requires a bandwidth of about 3000 cycles per second (3 KHz). A TV channel occupies a bandwidth of 6 million cycles per second (6 MHz) in terrestrial Systems. In satellite based systems a larger bandwidth of 17.5 to 72 MHz is used to spread or "dither" the television signal in order to prevent interference.

Baseband:
The basic direct output signal in an intermediate frequency based obtained directly from satellite receiver.

Baud:
The rate of data transmission based on the number of signal elements or symbols transmitted per second. Today most digital signals are characterised in bits per second.

Beacon:
Low-power carrier transmitted by a satellite which supplies the controlling engineers on the ground with a means of monitoring telemetry data, tracking the satellite, or conducting propagation experiments. This tracking beacon is usually a horn or omni antenna.

Beamwidth:
The angle or conical shape of the beam the antenna projects. Large antennas have narrower beamwidths and can pinpoint satellites in space or dense traffic areas on the earth more precisely. Tighter beamwidths thus deliver higher levels of power and thus greater communications performance.

Bent Pipe:
In the satellite communications environment this refers to a telecommunications link without any on-board signal switching or processing. In effect transmission path is a bent pipe going from point A on the ground up to the satellite before being bend downwards for reception at point B.

Big LEOs:
Low Earth orbiting satellite systems using spectrum above 1 GHz for mobile communications. Such systems include Iridium and Globalstar.

Bit:
A single digital unit of information.

Bit Error Rate:
The fraction of a sequence of message bits that are in error. A bit error rate of 10-6 means that there is an average of one error per million bits.

Bit Rate:
The speed of a digital transmission, measured in bits per second.

Block Down Converter:
A device used to convert the 3.7 to 4.2 KHz signal down to UHF or lower frequencies (1 GHz and lower).

Broadband:
Loosely used term intended to distinguish transmission of services that include a lot of information (high speed data, TV channels) from services that have very little information (individual voice telephony circuits).

Business Television (BTV):
Closed user group television network primarily used internally within a company or an organisation. Typically such a TV station will use satellite capacity to broadcast for a few hours per week to a limited number of sites.