The probability that the offloaded macroU is treated as CU at the femtoBS with respect to the available pairing user is given as Pcomp P where q (satisfying 0    1 ) represents the ratio of channel gain of the PU and the OmacroU. The probability density function for the same is given as [63] 5 NOMA for 5G and Beyond Wireless Networks (n-1) (-n+k-1) (5.3) (z +1 + 2 2 2 j1=0 j2=0 where t1 = j1 - j2 + k - n, andt2=Mf-k+1+j2.Hence, the probability can be calculated using Pcomp (9) [37]. NC probability helps us differentiate whether the OmacroU is a CU or EU with respect to the available PU. 5.6.2.3 Corresponding PU Probability Unlike Scenario-I, where the pairing user is always available, in Scenario-II, the femtoBS is required to search for a corresponding pairing user. When the offloaded macroU is a CU, the femtoBS searched for an EU and when the offloaded macroU is an EU, the femtoBS searches for a CU. Therefore, we derive probability of finding an appropriate pairing user at the FSB tier which is given as follows. Hence, the probability of at least one user lying in the CU region is given as [37] Similarly, the probability of presence of a pairing user in EU region can be written as [37] (5.4) For more details on the derivation, readers may refer to [37]. 5.6.3 Total Outage Probability Total outage probability indicates the outage probability at the macroU after the decision of offloading is made. If the decision is in favor of offloading, then the macroU is served by the femtoBS tier; else is served using the macroBS tier which is highlighted in the total outage probability expressions. Furthermore, whether the P. Swami and V. Bhatia offloaded macroU is served as a cell edge user of cell center user at the femtoBS tier is also reflected in the total outage probability. For Scenario-I, it assumed that the pairing user is always available, while for Scenario-II, pairing user is searched by the femtoBS tier; hence, the total outage probability also contains the corresponding PU probability. 5.6.3.1 Total Outage Pro