Comtech EF Data CDM-625 - Manual (Page 336)

CDM-625 Advanced Satellite Modem Revision 15
DoubleTalk Carrier-in-Carrier Option MN-CDM625
10–6
Figure 10-3. Same Link Using CDM-625 and DoubleTalk Carrier-in-Carrier
Figure 10-4. Duplex Link Optimization
The CDM-625 CnC module operates on the near-zero signal before the demodulator, and is
waveform agnostic. This means that no prior knowledge of the underlying modulation, FEC, or
any other waveform specific parameter is required in order to perform the signal suppression
operation. The only caveat to this is that the waveform must be sufficiently random.
Because acquiring the delay and frequency offset of the interfering carrier is fundamentally a
correlation operation, anything deterministic in the interfering carrier (within the correlation
window of the algorithm) will potentially produce false correlation peaks and result in incorrect
delays and/or frequency. Normally, this is not a problem, since energy dispersal techniques are
utilized in the vast majority of commercial and military modems. However, it is something that