Prn-Ber Computation; Ber On Separate I & Q Channels; Ber On Merged I & Q Channels - Safran CORTEX Series User Manual

3.3.8

PRN-BER Computation

Depending on the mission, BER measurement in PRN mode can be done either on separate or
merged I and Q channels (see 4.2.9.2.3 ).
3.3.8.1 BER on Separate I & Q Channels
This method is based on PRN codes property: The splitting of a PRN data flow into I and Q provides
two PRN data flows (same PRN).
When restarting BER measurement (see 4.5.4.4 ), each ambiguity is tested (~1s), before selecting the
ambiguity which provides with the lower BER. The BER is then measured applying this ambiguity. This
method is particularly interesting when the ambiguity is not resolved by the demodulation (example:
Metop satellite configuration).
Example 1: QPSK, NRZ-L demodulation. Demodulation remaining ambiguities:
If natural QPSK de-mapping is used: IQ, /QI, Q/I,/I/Q.
If inverse QPSK de-mapping is used: QI, I/Q, /IQ,/Q/I.
Even with these ambiguities, BER measure can be done in this mode.
Using this method, BER I and BER Q can be separately displayed (see 4.2.9.2.3 , value 1), or
averaged (see 4.2.9.2.3 , value 0).
Example 2: 8PSK, NRZ-L demodulation, using a PRN code for each 3 8PSK data flows.
Demodulation remaining ambiguities:
If natural 8PSK de-mapping is used: 8 phase ambiguities.
If inverse 8PSK de-mapping is used: 8 other phase ambiguities.
Providing that the right 8PSK de-mapping (normal or inverse, natural or Gray) has been selected, BER
measure can be done in this mode.
3.3.8.2 BER on Merged I & Q Channels
This method applies to merged I and Q data in QPSK or OQPSK mode, or single I data in BPSK mode,
or single I + Single Q in UQPSK mode, or single1 + single2 + single3 in 8PSK mode.
In this mode, no ambiguity tests are done. Data which are used for BER measure are an image of
output data (channel A for Demodulation Unit # 1, channel B for Demodulation Unit # 2, see 2.2.2 ).
Ambiguities can then be manually tested, using the 8 first values of OUTPUT MODE parameter (see
4.5.4.1 ).
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Date: June 1, 2021
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