## 5 Dimensional Transformation Residual Network (DTRN)  
Before introducing the structure of DTRN, it is necessary to analyze the SRSs and feature vectors extracted from them. These vectors serve as the input vectors for the DTRN network and are crucial for understanding the network's operation principles. First, the SRS signal, in NR standard, the maximum number of SRS layers supported is 4, and it is mapped to the antennas through spatial filters. In terms of resource grid configuration, the frequency-domain structure of SRS exhibits a comb structure. In sequence design, the base sequence of SRS is based on the extended Zadoff-Chu sequence [31]. The base sequence is used to generate the SRS signal and this generation process occurs continuously during the network access procedure. For multi-port SRS, NR standard specifies the use of cyclic shift to process the SRS signal. Cyclic shift in the time domain is equivalent to the phase rotation in the frequency domain. In this way, the different logic ports can be effectively distinguished. Table 1 shows the phase rotation method for SRS at \(N_{p_{i}}=4\). Based on the characteristics of the extended Zadoff-Chu sequence, continuous cyclic rotation of the phase does not change the orthogonality between two signals. However, in the time domain, it introduces cyclic fluctuations in the amplitude [32]. These fluctuations do not have a substantial impact on the processing of the sequence. The sequence still maintains perfect autocorrelation properties in frequency domain. In addition, FPLA can operate policy adjustments based on the number of elements in the feature vector, denoted as E. FPLA works in the 5G n78 frequency band, with a supported channel bandwidth of 20 MHz and a Sub-Carrier Spacing (SCS) of 15 kHz. According to the NR standard, the maximum number of resource blocks \(N_{rb}\) supported by the above configuration is 106. The number of elements \(E_{i}\) of the feature \(\mathbf{V_{i}}\) extracted from UE \(i\) can be obtained from Equation (7) as:  
\[E_{i}=N_{p_{i}}\cdot N_{rb}\cdot N_{a}. \tag{8}\]  
Therefore, when the band allocation is completed, the size of \(E_{i}\) depends solely on \(N_{p_{i}}\) and \(N_{a}\). The diversity of UEs in the MU-MIMO system leads to the uncertainty of Ei, requiring Alice to handle it in a special manner to accommodate the DTRN network. Based on Equations (2), (3) and (8), once the number of antenna ports \(N_{a}\) is determined at Alice's end, the feature dimension extracted from UEs will exhibit three distinct \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \(\mathbf{x_{0}}\) & \(\mathbf{x_{1}}\) & \(\mathbf{x_{2}}\) & \(\mathbf{x_{3}}\) & \(\ldots\) \\ \hline Port 1 & \(e^{0}\) & \(e^{0}\) & \(e^{0}\) & \(e^{0}\) & \\ Port 2 & \(e^{0}\) & \(e^{\pi\pi}\) & \(e^{2\pi\pi}\) & \(e^{3\pi}\) & \\ Port 3 & \(e^{0}\) & \(e^{\frac{\pi}{2}}\) & \(e^{\frac{\pi}{2\pi}}\) & \(e^{\frac{\pi}{2\pi}}\) & \\ Port 4 & \(e^{0}\) & \(e^{i\frac{\pi}{2\pi}}\) & \(e^{i\frac{\pi}{2\pi}}\) & \(e^{i\frac{\pi}{2\pi}}\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Phase rotation method for SRS at \(N_{p_{i}}=4\). Different phase shifts of the frequency domain base sequence (\(\mathbf{x_{0}},\mathbf{x_{1}},\mathbf{x_{2}},\mathbf{x_{3}},\ldots\)) are used for the different antenna ports. The SRS transmitted by each port is differentiated from each other by a continuous phase rotation process of the base sequence. forms. The third dimension is determined by the inherent attributes of the UEs and takes values from the set \(\{1,2,4\}\). In other words, vector \(\mathbf{V_{i}}\) can assume three forms: \(\mathbb{C}^{1\times 106\times 32},\mathbb{C}^{2\times 106\times 32},\mathbb{C}^{4 \times 106\times 32}\). Furthermore, the three forms of features exhibit significant differences in the number of elements, with a ratio of 1:2:4. Figure 3 illustrates these modulus graphs, intuitively demonstrating the differences in shapes of the vectors. A common approach to handle feature vectors is to establish CSI image [24].