paired carrier
This technique allows the transponder bandwidth to be reused by superimposing carriers on top of each other. This has the potential for major savings in space segment rental costs. It is possible when, in the system design, the fractional transponder bandwidth resource is being used up first, before the power resource is fully utilised. This can occur in networks where not all earth stations are of the minimum possible size, from the point of view of receive G/T. In such cases, with modern high sensitivity/high power satellites, it is difficult to simultaneously and efficiently exploit the satellite power and bandwidth resources. The tendency is to run out of bandwidth and resort to abnormally high power spectral density carriers such as 8 PSK or 16 QAM or similar. In PCMA, an earth station knows what it is transmitting and by suitably delaying and then subtracting a weak version of the transmitted signal from the received signal the 'interference' arising from carrier superimposition is eliminated.
And see the attached file also.
**broken link removed**