Quantum and Evolution Series Installation and Operating Handbook
8-59
Channel Per Carrier (SCPC) and Demand Assigned Multiple Access (DAMA) voice and
data networks.
Paired Carrier
helps in the case of bandwidth-limited links. However, if a link is instead
power limited then its design can be changed to turn it into a bandwidth-limited link and
then
Paired Carrier
can be used to increase the bandwidth utilisation.
It should be noted that
Paired Carrier
operation is waveform agnostic and will work with
all
modulation and FEC schemes. It is used in addition to, not instead of, other bandwidth
saving techniques.
Paired Carrier
and DVB-S2 represent the two most bandwidth-efficient
technologies available today and can uniquely be used together in the Quantum modem.
Some frequently asked questions about
Paired Carrier
operation along with answers are
provided below.
Q. Does
Paired Carrier
require a particular modulation or FEC configuration?
A. No,
Paired Carrier
imposes no special parameter limitations on the carriers involved.
However, sometimes it is advantageous to use the bandwidth savings to switch to a more
robust modulation and coding scheme - but this is application dependent.
Q. Can
Paired Carrier
handle multiple transmit and receive carriers?
A. No, the separate Paradise PCMA-70 Satellite Bandwidth Extender should be used if
you require to cancel multiple carriers appearing within the cancellation bandwidth.
Q. Can
Paired Carrier
handle asymmetric carriers, that is, carriers with different data
rates and/or different symbol rates on transmit and receive?
A. Yes, the
Paired Carrier
can handle asymmetric carriers. The transmit and receive
parameters are totally independent.
Q. My transmit and receive carrier levels off satellite are different, can I still use the
Paired Carrier
satellite signal canceller?
A. Yes, the wanted and unwanted signals off satellite can be of different levels, however,
the wanted and unwanted signal levels (power spectral density) should normally be within
10dB of each other. Symbol rate asymmetry of up to 5:1 is supported. It is sometimes
possible to relax these conditions subject to the constraints of an overall detailed link
budget analysis.
Q. Does the modem redundancy configuration affect
Paired Carrier
operation?
A. No,
Paired Carrier
works equally as well in 1:1 and 1:n modem redundancy systems.
Paired Carrier
requires the modem to see its own transmission and also the composite Rx
signal. Both of these are available to the Standby modem, which mutes its Tx output but
not before this has been sampled by the internal
Paired Carrier
function, allowing
Paired
Carrier
to be actively working on the Standby modem in tandem with the on-line modem.
When a switchover occurs therefore, there is no
Paired Carrier
reacquisition process in
the modem that was on Standby as it has already acquired the satellite signal.
