# Performance of Cooperative Relay NOMA with Large Antenna Transmitters
## 4 Numerical Results and Analyses
### Outage Probability (OP) Performance  
The analysis cannot be complete without examining the outage probability. Employing 3D GBSM URA and CA channel models in (12) and (15), we demonstrate the outage probability of mMIMO CR-NOMA as a function of transmitting SNR in Figure 9. The performance disparity between the two users, UE\({}_{1}\) and UE\({}_{2}\), spreads across the whole range of SNR. This is demonstrated in the OP outcome of the 3D URA system. It is important to note that modifying the transmitter array arrangement and expanding the TX's antenna elements while keeping a single antenna at the relay node can dramatically increase system outage performance. Furthermore, it demonstrates that UE\({}_{2}\)'s outage performance is poorer than UE\({}_{1}\). This means that using less transmit power at the relays lowers the hop's outage performance, which in turn affects the total outage performance. This is because signal \(x_{1}\), which is regarded as noise, causes interference in the communication link between the RS and UE\({}_{2}\). UE\({}_{1}\) signal \(x_{1}\) is amplified when the UE\({}_{2}\)'s signal (\(x_{2}\)) is amplified by RS with AF coding  
Figure 8: BER comparison of AF and DF schemes with (**a**) DF and (**b**) AF coding schemes. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Ref.** & **Relay Schemes** & **Channel Model \& Antenna Type** & **No. of Users** & **SNR (dB)** & **BER** \\ \hline \multirow{3}{*}{Proposed model} & AF & GBSM, multiple antenna TX, & & & 5 & \(10^{-2.50}\) \\  & DF & single antenna RS and UE & & & 20 & \(10^{-2.85}\) \\  & & & single antenna RS and UE & & 5 & \(10^{-2.05}\) \\  & & & & & 20 & \(10^{-2.40}\) \\ \hline \multirow{3}{*}{[15]} & CpF & & & & 5 & \(10^{-3.80}\) \\  & AF & CBSM, single antenna TX, RS and UE & & & 20 & \(10^{-5.00}\) \\  & DF & & & & 5 & \(10^{-2.80}\) \\  & & & and UE & & 20 & \(10^{-3.00}\) \\  & DF & & & & 5 & \(10^{-1.80}\) \\  & & & & & 20 & \(10^{-2.10}\) \\ \hline \multirow{3}{*}{[43]} & AF & & & & 5 & \(10^{-1.50}\) \\  & DF & & & & 20 & \(10^{-2.70}\) \\  & & & and UE & & 5 & \(10^{-1.00}\) \\  & & & & & 20 & \(10^{-2.70}\) \\ \hline \multirow{3}{*}{[115]} & AF & CBSM, single antenna TX, RS and UE & & & 5 & \(10^{-2.00}\) \\  & & & and UE & & 20 & \(10^{-2.70}\) \\ \hline \multirow{3}{*}{[116]} & \multirow{3}{*}{DF} & CBSM, multiple antenna TX, RS and UE & & & 5 & \(10^{-1.95}\) \\  & & & and UE & & 20 & \(10^{-4.96}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of average BER with prior works. scheme. The interference impacts the decoding performance of the RS when using the AF coding scheme for the connection between RS\(-\)UE\({}_{2}\). Again, Figure 9 shows outage probabilities of two users with AF and DF relay coding schemes. It can be seen that under the 3D URA channel model, the OP of the DF coding scheme achieves higher performances than the AF coding scheme. We further perform analysis using the CA channel model. Here, the OP of UE\({}_{1}\) using AF coding scheme performs better than that of the DF coding scheme, unlike that of the OP of the URA channel model. Generally, the performance of the system using the CA is better than URA for both AF and DF coding schemes. In Table 4, we compare OP performance at SNR of 15 dB of the proposed 3D GBSM channel models with prior works that use CBSM models.