Transmit SNR Fig. 5.7 Outage probability for various q (Scenario-I) [37]. (a) For q = 0.1. (b) For q = 0.5. (c) For q = 0.8 P. Swami and V. Bhatia outage probability at the offloaded user, whether it is served as CU or EU, is nearly the same. This contributes to yet another important aspect of NOMA which is user fairness. It can be noticed that the difference in outage performance between the offloaded macroU as CU and EU is lowest for q = 0.5 as compared to the other two selected values of q, i.e., for q = 0.1 and q = 0.8. This is due to the fact that we have assumed constant power allocation factors for CU and EU. Therefore, although the channel difference gets lower between the CU and EU, the power allocation remains the same. This leads to nearly similar performance between the CU and EU leading to user fairness which is desirable in NOMA application. Lastly, Fig. 5.7c reveals that the outage probability for q = 0.8. It can be noticed that for high values of q, the difference between the CU and EU becomes very low. Therefore, in such case, the best performance is achieved when the offloaded macroU is served as EU at the femtoBS. This is again attributed to the fact that although the channel difference is lowered, the power allocation factors remain constant. Further, it must be noted that whether the offloaded macroU is served as CU or EU, the outage performance achieved is better as compared to when offloading is done to femtoBS tier without NOMA. Figure 5.8 reveals plots for outage probability under Scenario-II when it is assumed that the femtoBS tier first searched for an appropriate pairing user for the offloaded macroU. It is evident from the figure that the outage probability achieved at the offloaded macroU for Scenario-II is degraded as compared to Scenario- I. The explanation for this degradation is straightforward. Under Scenario-I, the availability of pairing user for the offloaded macroU is guaranteed. However, for Scenario-II, the femtoBS may or may not find corresponding pairing user for the - M