Modem
Reference Manual for EL470 IP Satellite Modem
Command
MoNonLinPredMode
Nonlinear predistortion Nonlinear pred
Location
/Modem/Control/Modulation/PHY
This predistortion feature is optional and password upgradeable.
Description
Configuration command to enable or disable the non-linear pre-distortion
function. Non-linear pre-distortion can substantially improve the overall
performance of the satellite link. The pre-distortion function compensates
for the am/am and am/pm effects caused by driving the satellite
transponder close to saturation. Hence it is clear that the pre-distortion
itself depends on the actual transponder being used and the operating
point (= nominal transmit level).
The pre-distortion data must be calculated off-line and requires
transponder m/am and am/pm characteristics and operating level as input.
Remark: Pre-distortion data also depends on the modulation format
(QPSK,8PSK,16APSK,32APSK) and on the actual constellation; i.e.
different APSK modcods having different amplitude ring-ratios. Therefore,
for handling ACM operation with dynamically varying modcods, the off-line
calculation tool will calculate a set of data-tables which can be uploaded to
the modulator and stored in internal flash.For each symbol to be
transmitted, the modulator performs an amplitude and phase correction on
the symbol.The value "L" specifies the length of the symbol history
(number of symbols)
taken into account for correcting each transmit symbol :
•
L = 1: Static pre-distortion, uses only the current symbol.
•
L = 3: Dynamic pre-distortion using the current, previous and next
symbols.
•
L = 5: Dynamic pre-distortion using the current, two previous and two
next symbols.The Modulator implementation can handle
CCM/VCM/ACM modes with the following L-values :
•
L = 5 for QPSK and 8PSK modulation formats.
•
L = 3 for 16APSK and 32APSK modulation formats.
RMCP
Command
NPm
Access
Normal user : no access
Expert user : RW
SNMP
Table
ntcDevsMod01ModulatorEntry
Command
ntcDevsMod01MoNonLinPredMode
OID
1.3.6.1.4.1.5835.3.1.3.1.102.1.1
Values
Factory Default
disable
Enumeration
Value
Disabled
Enabled
0
1
version 3.1
90
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