. Recently, NOMA has been proposed for the 3GPP long-term evolution (LTE) [13, 14]. It must be noted that in long-term evolution-Advanced (LTE-A), a two-user case of NOMA is implemented [15]. The NOMA technique can be categorized as power domain (PD)-NOMA and code domain (CD)-NOMA (generally referred to as sparse code multiple access). The CD-NOMA technique includes multi-user shared access [16], multiple access solutions relying on low- density spreading [17], successive interference cancellation amenable multiple access [18], sparse code multiple access [19, 20], etc. 5 NOMA for 5G and Beyond Wireless Networks The basic and prime difference in the application of PD-NOMA and CD-NOMA is that PD-NOMA exploits power domain while CD-NOMA exploits CODE domain for non-orthogonal resource allocation. This chapter discusses about PD-NOMA owing to its popularity and easier implementation [4]. For employing PD-NOMA, only little or no hardware changes are required in the existing transmitter and receiver operating using orthogonal multiple access technology. In PD-NOMA, multiple users are served in the same resource block, i.e., the same frequency is used at the same time to serve multiple users. This is achieved by having variation in their allocated power. The technique used to make implementation of NOMA successful is, namely, superposition coding and successive interference cancellation (SIC). The messages of multiple users are superimposed using superposition coding and transmitted as shown in Fig. 5.1. One thing to be noted here is that for NOMA, users with different channel conditions are paired together. Application of NOMA considering two users, termed as User 1 (referred to as near user or cell center user) and User 2 (referred to as far user or cell edge user), is illustrated in Fig. 5.1. The messages of User 1 and User 2 are combined using superposition coding. Later, as per the order of users' channel gain conditions, SIC is applied to decode users' messages [7]. Let us assume that the base station (BS) alloca