  The aim of this letter is to develop a new design of cognitive radio inspired
non-orthogonal multiple access (CR-NOMA), which ensures that multiple new users
can be supported without causing disruption to the legacy network. Analytical
results are developed to characterize the statistical properties of the number
of supported new users. The developed CRNOMA scheme is compatible to various
communication networks, because it can be implemented as a simple add-on. An
example of using CR-NOMA as an add-on in time-division multiple access networks
for age of information (AoI) reduction is illustrated, where analytical results
are developed to demonstrate
