Promax PROLINK-4C, Manual

Page: 164 / 334

USER’S MANUAL. PROLINK-4C
Page 44 02/2003
Figure 14.- BER measuring screen for COFDM-modulated signals
Two measures are shown :
1) CSI: Channel status information
2)
BER after Viterbi
The CSI measure (Channel Status Information) is a qualitative measure about
channel state, between 0 and 100%. The optimum value corresponds to 0%. This
measure permits to look for the best situation even in those measuring conditions where
the measured BER is best than the minimum readout (in this way, in the example of the
previous figure, the measured BER is lower that the minimum readout, 1.0x10
-7
, but the
CSI measurement, 27%, still can be improved).
Next it is shown the BER after Viterbi measurement both in numeric and
graphic bar format.
In a reception system of terrestrial digital signal, after the COFDM decoder two
error correction methods are applied. Obviously, each time we apply an error corrector
to the digital signal, the error rate changes, therefore if we measure the error rate at the
output of the COFDM demodulator, at the output of the Viterbi decoder, and at the
output of the Reed-Solomon decoder, we obtain nothing more than different error rates.
The PROLINK-4C provides the BER after Viterbi and the number of Wrong packets
received after Reed- Solomon.
Figure 15.- COFDM reception system.