B
Backhaul
The communications system connecting the hub of
a star network to the user's data centre
Backup
A copy of a critical set of data taken as a precaution
against the loss of the original. Also the act of making the copy.
Bandwidth
The range of frequencies over which a system operates or is capable of
operating.
Baseband
The information signal, prior to modulation onto
a carrier frequency.
Baud
Every time a transmission changes from one state
to another one baud is sent. The band rate is the number of times per
second this occurs. The baud rate represents the information carrying
capacity of the system.
Beacon
An un-modulated signal transmitted by the satellite
to facilitate frequency control, tracking, pointing and identification.
Beamwidth
The angle at which radiation spreads out from an
antenna as it propagates. The power from the signal smoothly tapers at
the edges of the beam, for beam width calculations the points where the
radiation is at half its peak value, or its peak value -3dB is taken as
the edge of the beam of radiation.
BER Bit Error Rate.
The proportion of bits that are received in error. Usually expressed exponentially,
for example, 1 in 106.
BERT
Bit Error Rate Test, the act of measuring the BER.
This is normally performed by suspending normal operation and sending
a reference signal. In satellite communication the BER can be calculated
by measuring the received signal:noise ratio which allows the quality
of the satellite link to be measures non-intrusively.
BPSK
Binary Phase Shift Keying, cf: QPSK, a system of
modifying a carrier frequency such that its phase changes in response
to a binary signal. One baud equates to one bit.
Bitrate
The number of bits a system conveys each second in bits per second (bps).
Broadcast
A transmission sent to a number of receives simultaneously.
BTV
Business television. A private corporate communications
system that allows the user to broadcast live or pre-recorded video to
a closed user group.
Bursty data
Information that must be sent sporadically.
Byte
Eight Bits in succession.