TSAT 3000 - Telemetry and data transfer via SATellite
TSAT 3000 Configuration Parameter Description, January 2013 Page 53 of 124
3.7.3 GAIN_TX_END2END_TARGET
Default 0.0, Range 0.0 + 6.0…20.0
Control the “End-to-End Tx-Gain” facility.
Value Description
0.0 Disable “End-to-End Tx-Gain” facility.
6.0 … 20.0 Enable “End-to-End Tx-Gain” facility.
When enabled, the Tx-Gain DAC is adjusted in small steps until the measured Receive-Level
(E
b
/N
0
) at the remote side is equal GAIN_TX_END2END_TARGET [dB]. However, the Tx-Gain DAC
setting is limited to a value in the range defined by
GAIN_TX_DAC_{MIN | MAX}.
• Incremented – When the signal level received at the other side of the
link is <
GAIN_TX_END2END_TARGET – DELTA [dB].
• Decremented – When the signal level received at the other side of the
link is >
GAIN_TX_END2END_TARGET + DELTA [dB].
Ver <= 30.2.0: DELTA = 0.5 dB.
Ver == 30.3.0:
DELTA = 0.3 dB.
Ver >= 30.3.1:
DELTA = 0.2 dB.
Ver >= 31.1.0: Gain regulation is temporary stopped when Tx-Gain DAC has been changed more
than 500 units, and the measured (average) receive signal on remote side has changed less
than expected (500 units = approx 3.3 dB).
The CCU is detecting the signal level, received at the other side of the link:
• The signal levels at which the HUB is receiving RTs are signalled back to RTs in
SYNC
packets.
• The signal level at which the RT is receiving HUB is signalled back to HUB in
POLL_ACK
packets. The HUB will then adjust its Tx-Gain DAC so that the average
receive level at RTs is
equal
GAIN_TX_END2END_TARGET [dB].
The function to detect received signal level is different on the various CCU versions:
HUB + RT Ver <= 30.2.0: Sliding average of last 16
received OK packets.
RT Ver >= 30.3.0: Sliding average of last 32
received OK packets.
HUB Ver == 30.3.0: Sliding average of last 32 received OK packets.
Collided packets (detected by PPR) are discarded from measurements.
OK packets with E
b
/N
0
< 0.9 x average E
b
/N
0
are also discarded (because this could
be collided packets), except packets received in slot-zero (normally
POLL_ACK).
HUB Ver == 30.3.1: Sliding average of last 32 received OK packets, except when the
received E
b
/N
0
is more than 1.5 dB different to average E
b
/N
0
. In the latter case, this
measurement will be used immediately (to avoid problems with End-to-End Gain
Control).
Collided packets (detected by PPR) are discarded from measurements.
OK packets with E
b
/N
0
< 0.9 x average E
b
/N
0
are also discarded (because this could
be collided packets), except packets received in slot-zero (normally
POLL_ACK).
HUB Ver >= 30.4.0: Same behaviour as version 30.3.1, except when the received E
b
/N
0
is
more than 1.5 dB different to average E
b
/N
0
in two following slot-zero packets. In the
latter case, this measurement will be used immediately (to avoid problems with End-
to-End Gain Control).
Note: A Slave-HUB in “Multi Inbound Link” (MIL) network (see PHL_TX_RT_FREQUENCY_2)
cannot transmit. CCU Ver >= 30.8.0 will then always set
GAIN_TX_END2END_TARGET = 0
(disable this facility) when it’s booting.
See also GAIN_TX_REF.
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