## 2 System Model
### Cooperative jamming Model  
We consider an AF-based cooperative communication system, which consists of a source node (\(S\)), a destination node (\(D\)), an untrusted relay node (\(R\)), \(N\) number of cooperative jammer nodes (\(C\)\(I_{i}\)) and \(N\) number of CJ's destination nodes (\(D\)\(I_{i}\)), where \(i=\{1,\ldots,N\}\)[55]. It is assumed that each node has a single antenna. Our suggested system is divided into three phases depending on time slots. In more detail, the phases are as follows: the source information transmission denoted as the first phase in this paper, the relaying and jamming signal transmission denoted as the second phase, while in the end, the cooperative jammer will transmit its own information/message denoted as the third phase, as is depicted in Figure 2. During the first phase, the CJs will also transmit a jamming signal in addition to the source data transmission.  
The information symbols conveyed by the PU, cooperative jammers, and untrusted relay are denoted by the symbols \(X\)\(\{.\}\), \(Y\)\(\{.\}\) and \(Z\)\(\{.\}\), respectively. The first phase, second phase, and third phase transmissions are denoted by the subscripts \(t_{1}\), \(t_{2}\), and \(t_{3}\), respectively. The eavesdropper is an outside entity as was presented in the two-phase model provided in [48]. In this paper, we consider the eavesdropper as an untrusted relay, which is not an outside entity and hence poses a different challenge. The time slot \(T\) of the overall transmission is scaled to unity. The primary transmission is kept as a time slot fraction \(\alpha\leq 1\). That time slot will be equally divided into the first and second phase, i.e., we have a \(\frac{\pi}{2}\) duration for each of the two phases.  
In the third phase, the CJs will receive a reward, with the remaining \((1-\alpha)\) period being devoted to their non-altruistic jamming contribution. As a reward, we take into account two transmission strategies for the SUs throughout their designated third slot. These are the UR-MCJST scenario described in Section 3.1 and the UR-MCJTDT scenario described in Section 3.2. In the UR-MCJST scenario, all jammers simultaneously access the allocated bandwidth during the third phase time slot of duration \((1-\alpha)\). However, for the  
Figure 1: Classification structure for secure communication networks based on Table 1.  
URE:S2.F2][ENDFIGURE]  
The wireless channel considered between different transceiver pairs represented as a pair \((k,r)\) is denoted by \(h_{kr}=\sqrt{G_{kr}}.\overline{h}_{kr}\), where \(\overline{h}_{kr}\) is the Rayleigh fading coefficient, \(G_{kr}=(\frac{d_{SD}}{d_{kr}})^{\rho}\) is the reduced distance related path gain [17; 56], and \(\rho\) is the pathloss exponent, while the distance between the two transceivers is represented as \(d_{kr}\). The received SNR at node \(r\) will be defined as \(\gamma_{kr}=\frac{|h_{kr}|^{2}}{N_{0}}\), where \(N_{0}/2\) is the noise variance per dimension. Furthermore, \(P_{\delta}\) is the source's power, and \(P_{CJ_{i}}\) is the \(i\)th jammer's power. The ratio of the power invested for transmitting jamming signals to that invested for the CJ's secondary transmission is given by \(\beta\).