  The impact of successive interference cancellation (SIC) in non-orthogonal
multiple access integrated sensing and communications (NOMA-ISAC) is analyzed.
A two-stage SIC-based framework is proposed to deal with the
inter-communication user and inter-functionality interferences. The performance
of sensing and communications (S\&C) is analyzed for two SIC orders, i.e., the
communications-centric SIC and the sensing-centric SIC. For each design,
diversity orders, high signal-to-noise ratio (SNR) slopes, and high-SNR power
offsets of the sensing rate (SR) and communication rate (CR) are derived as
insights. Analytical results indicate that i) the main influence of SIC order
on the SR and CR lies in the high-SNR power offsets; ii) ISAC provides more
degrees of freedom than frequency-division S\&C (FDSAC). Numerical results show
that the SR-CR region of ISAC entirely covers that of FDSAC.
