## 2 System Model  
Here, a DL-MU scenario with a SWIPT-enabled mmWave-MIMO-NOMA network is depicted within Figure 1 and is taken into consideration for the performance assessment. In this case, the base station (BS) has \(N_{T}\) transmit antennas. Here, the performance evaluation focuses primarily on the SC structure. As in Figure 1, \(N_{RF}\) chains of RF have been utilized for extending the backing to \(K\) single antenna UEs [3,4] (\(N_{RF}\leq K<N_{T}\)). As far as the SC structure is concerned, every RF chain has been coupled to \(M\) (\(=N_{T}/N_{RF}\)) antennas. Additionally, Ref. [3] states that the number of beams (\(D\)) created cannot be greater than \(N_{RF}\). For the purpose of simplicity, it is presumed that \(D=N_{RF}\). Under the proposed system model, the core concept of NOMA is exploited to support UEs through each beam. Thus, in other words, the \(K\) UEs can be supported through \(D\) clusters corresponding to each beam. As in this proposed model, all UEs data streams have been coded by utilizing baseband DP \(\mathsf{F}_{d}^{BB}[N_{RF}\times 1]\), \(d\in[1,D]\) regarding the \(d^{th}\) beam and \([N_{T}\times N_{RF}]\) RF AP \(\mathsf{F}^{RF}\) exploiting the analogue phase shifter. In the case of AP, all of its components must be present to meet \(\left(\left[\mathsf{F}^{RF}\right]_{:j}\left[\mathsf{F}^{RF}\right]_{:j}^{H} \right)_{IL}=N_{T}^{-1}\) with \(\left|\left[\mathsf{F}^{RF}\right]_{:j}\right|=N_{T}^{-1/2},1\leq i\leq N_{T}, 1\leq j\leq N_{RF}\)and quantized phases: \(\big{[}\mathbf{F}^{RF}\big{]}_{i,j}=(N_{T})^{-1/2}exp\Big{(}j[\Phi]_{i,j}\Big{)}\), and \(\big{[}\Phi]_{i,j}\) can be quantized as \(\big{[}\Phi]_{i,j}\in\ :=\Big{\{}\frac{2\pi H}{2^{B}}:n=0,\ldots,2^{B}-1\Big{\}}\). In addition to the aforementioned constraints, the overall power constraint has been enforced via normalising DP \(\mathbf{\epsilon}_{d}^{BB},d=1,\ldots,D\) for the \(d^{th}\) beam so that \(\big{\|}\mathbf{F}^{RF}f_{d}^{BB}\big{\|}_{2}=1\) for \(d=1,\ldots,D\). No other constraints are imposed on DP. Let \(\Xi_{d}\) for \(d=1,\ldots,D\) represents the user set corresponding to the \(d^{th}\) beam with \(|\Xi_{d}|\geq 1\), and \(\Xi_{i}\cap\Xi_{j}=\ \text{for}\ i\
eq j\); thus, \(\sum_{d=1}^{D}|\Xi_{d}|=K\). In the case of a fully hybrid precoder, the AP matrix can be defined as  
\[\mathbf{F}^{RF(full)}=\bigg{[}\overline{f}_{1}^{RF(full)},\overline{f}_{2}^{ RF(full)}\ldots\ \overline{f}_{N_{RF}}^{RF\ (full)}\bigg{]}, \tag{1}\]  
where \(\overline{f}_{m}^{RF(full)}\in\mathbb{C}^{N_{T}\times 1}\ \forall\ m=1,2,\ldots,N_{RF}\) is the steering vector, having identical amplitude \(1/\sqrt{N_{T}}\), nevertheless with distinct phases [43]. For SC architecture, the AP matrix can be defined as  
\[\mathbf{F}^{RF(sub)}=\left[ \begin{matrix}\overline{f}_{1}^{RF(sub)}&0&\ldots &0\\ 0&\overline{f}_{2}^{RF(sub)}&0\\ \vdots&\vdots&\vdots\\ 0&0&\ldots&\overline{f}_{N_{RF}}^{RF\ (sub)}\end{matrix} \right], \tag{2}\]  
wherein \(\overline{f}_{m}^{RF(sub)}\in\mathbb{C}^{M\times 1}\ \forall\ m=1,2,\ldots,N_{RF}\) is the steering vector, having identical amplitude \(1/\sqrt{M}\), nevertheless with distinct phases [44]. Let \(x_{d,k}\) (\(\mathbb{E}[\big{|}x_{d,k}\big{|}^{2}]=1\)) represent the signal delivered to the \(k^{th}\) UE i the \(d^{th}\) beam. Although the system exploits the NOMA scheme, the BS utilizes superposition code to support multiple UEs simultaneously. Additionally, the entire power (\(P\)) has been divided evenly among all \(K\) UEs. At the receiver side, every UE exploits successive interference cancellation (SIC) to retrieve the desired information signal. The \(k^{th}\) UE within the \(d^{th}\) beam receives the baseband signal \(y_{d,k}\)\([k=1,\ldots,|\Xi_{d}|]\), which can be expressed as  
\[y_{d,k}=\mathbf{h}_{d,k}^{H}\mathbf{F}^{RF}\sum_{i=1}^{D}\sum_{j=1}^{|\Xi_{i} |}\mathbf{f}_{i}^{BB}\sqrt{p_{i,j}}x_{i,j}+n_{d,k}. \tag{3}\]  
Figure 1: HP-aided mmWave mMIMO-NOMA-SWIPT system with SC architecture.