Async Packet Transmission with Unmodulated Carrier

I am attempting to transmit asynchronous packets in a precise manor
time tags, and at the same time transmit an unmodulated carrier while
are no packets being sent. I am considering disconnecting the USRP sink
from the packet path and connecting it to a signal source, however there
are questions of timing involved with knowing when to do this
reconnection. This design is to digitally phase modulate the carrier of
AM signal and therefore cannot have gaps in the carrier signal. I am
wondering how this all would work with time tagged data and the
carrier, or would these two processes interfere with one another? Also,
it could work, does anybody have any suggestions as to how it should be

Thank you in advance for any assistance,

Michael B.

What I am attempting to do is build a transmitter and receiver unit for
what the BBC is using for sending broadcast information in association
their AM broadcasts. This is called Amplitude Modulation System
(AMSS). I would like to be a bit more generic than the BBC standards
(allow for dynamic bit rates, allowing unmodulated an carrier, etc.).
anybody know if this has been done using GNURadio? Is there any
for the community to want a module to perform this task if I implement

Thank you very much,

Michael B.