Received Signal (Zfar) near user Znear Znear Sfar Snear Received Signal (Znear Demodulator Demodulator Remodulate FIGURE 5.6 PD-NOMA receiver. heat = (5.5) Where h and g represent Rayleigh channel vector which is zero mean complex circular Gaussian with co-variance matrix R for ie{far,near}. 5.4.1.3 Simulation Results The BER performance of the near user Snear near and the far user S of the system is shown in Figure 5.7, with power allocated of P1=0.8 and P2=0.2. Note that each user uses binary phase shift keying modulation (BPSK), and the signals go through AWGN and Rayleigh fading channels. The PD-NOMA performance decreases with the increasing of number of users because the inter-user interference and the residual interference will increase due to the increasing of the SIC error. The simulation result in Figure 5.7 shows the bit error rate for a PD-NOMA down- link system under a Rayleigh fading channel. The simulation result in Figure 5.8 shows the performance of turbo coding in a NOMA system under a Rayleigh fading channel and saves 20 dB compared to the uncoded NOMA system. 5.4.2 CODE-DOMAIN NOMA Figure 5.9 illustrates the overall schematic diagram of the CD-NOMA that will be tested. Each block is further explained below. 5.4.2.1 Sparse Code Multiple Access (SCMA) SCMA [20], which is known as sparse code multiple access is one of the main methods of CD NOMA. The SCMA is a multi-dimensional code book non orthog- onal spreading method. Likewise, the bits are immediately mapped by the SCMA encoder to multi-dimensional complicated code-words that have already been defined in a code-book set. An SCMA encoder is defined as a k-dimensional complicated codebook of size M that maps "log, (M)" bits into it. The factor graph matrix is used to represent the collection of codebooks in the SCMA system. The message passing 5G Wireless Communication System in Healthcare Informatics Far user Ray-ZF Near user Ray-ZF Far user AWGN Near user AWGN Eb/No (dB) FIGURE 5.7 BER performance of PD-NOMA. BER of NOMA under Rayleigh Channe