Vislink Strata RX Technical Reference Manual page 180

error correction. In effect, 7/8 of the packets are payload.
This has a much higher data transfer rate, but has far less
capacity to correct errors than a setting of 1/2 - so it is the
least robust FEC setting.
D.4.3 GI
Another error-correcting technique used in digital transmission
makes use of a Guard Interval (GI). The GI sets how much time
the transmitter allows between one symbol and the next. On the
receiving end, GI sets how long the receiver waits after one
symbol before it begins to process the next.
The GI enables the receiver to correct for time-based errors.
These errors typically arise from echoes and reflections as the
signal bounces off buildings and terrain along its path. In effect,
the transmitted signal travels along multiple paths to arrive at the
receiver. Each of these reflected signals arrives at a slightly
different time depending on the length of its path.
By waiting (for one GI) before attempting to process the next
symbol, the receiver allows time for any echoes of the first
symbol to arrive and thus not contribute errors to the next
symbol.
This length of time is controlled by the transmitter's GI setting.
A GI setting of 1/32 would allow a short time for echoes to
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arrive. (On an 8 MHz signal, this delay is 7 uS.)
This delay would be used in a situation where the
reflecting objects are very near, such as inside a sports
stadium. Any echoes would arrive at the receiver with
very short delay times.
This has the highest data transfer rate, but is the least
Strata RX Technical Reference Manual
robust GI setting.
A GI setting of 1/8 would allow more time for echoes to
•
arrive. (On an 8 MHz signal, this delay is 28 uS.)
This setting would be useful for city environments, where
the objects reflecting the signal are relatively close by and
the echo delays are relatively short.
A GI setting of 1/4 would allow a longer time for echoes to
•
arrive. (On an 8 MHz signal, this delay is 56 uS.)
This setting would be useful for more remote settings,
where the objects reflecting the signal are farther apart
and the echo delays are longer.
This setting has the lowest data transfer rate, but is the
most robust GI setting.
D.4.4 BW
When the transmitter applies the COFDM modulation to the
video and audio signals, it creates a signal of a certain
Bandwidth (BW). This Bandwidth is controlled by the
transmitter's BW setting.
• A BW setting of 6 MHz would mean the modulated signal
occupies 6 MHz of RF spectrum.
This setting is the most robust, but has the lowest data
transfer rate.
• A BW setting of 8 MHz would occupy more of the RF
spectrum.
This setting has the highest data transfer rate, but is the
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