## Appendix B  
1. Case 1 of Tx1: Tx1 is located to the left of the center axis of the PD  
The geometrical relationship in Figure 4 shows that \(I_{V_{1}-M,1,case1}=\frac{L_{w}-2L_{b_{1}}}{2\left(L_{w}-L_{b_{1}}\right)}I_{V_{ 1}-PD}\). Therefore, the angle of incidence and reflection \(\delta=\arctan\frac{I_{V_{1}-M,1,case1}}{L_{w}-2L_{b_{1}}}\) can be expressed as \(\delta=\arctan\frac{I_{V_{1}-PD}}{L_{w}-L_{b_{1}}}\). It is known that \(L_{b_{1}}\sim u\left(0,\frac{L_{w}}{2}\right)\), so the distribution of \(\delta\) can be obtained according to the variable transformation method:  
\[\delta\sim f_{\Delta}(\delta)=\frac{4I_{V_{1}-PD}}{L_{w}(1-\cos 2\delta)}, \tag{14}\]  
where \(\arctan\frac{I_{V_{1}-PD}}{L_{w}}\leq\delta<\arctan\frac{2I_{V_{1}-PD}}{L_{w}}\). \(D_{NLOS,case1}^{V_{1}-M}\) and \(D_{NLOS,case1}^{M-PD}\) can also be denoted by \(\delta\), i.e., \(D_{NLOS,case1}^{V_{1}-M}=\frac{I_{V_{1}-M,1,case1}}{\sin\delta}\) and \(D_{NLOS,case1}^{M-PD}=\frac{I_{M-PD,case1}}{\sin\delta}\). Case 2 of Tx1: Tx1 is located to the right of the center axis of the PD Similarly, the geometric relation \(I_{V_{1}-M,1,case2}=\frac{L_{w}+2L_{b_{1}}}{2\left(L_{w}+L_{b_{1}}\right)}I_{V_{1} -PD}\) is obtained in this case. At this point, \(\delta=\arctan\frac{I_{V_{1}-PD}}{L_{w}+L_{b_{1}}}\). For the sake of distinction, when Tx1 is located to the right of the center axis of PD, \(\delta\) is denoted as \(\theta\), i.e., \(\theta=\arctan\frac{I_{V_{1}-PD}}{L_{w}+L_{b_{1}}}\). From \(L_{b_{1}}\sim u\left(0,\frac{L_{w}}{2}-v_{w}\right)\), the distribution of \(\theta\) can be obtained according to the variable transformation method:  
\[\theta\sim f_{\Theta}(\theta)=\frac{2I_{V_{1}-PD}}{(L_{w}-2v_{w})\sin^{2} \theta},\] (A9)  
where \(\arctan\frac{2I_{V_{1}-PD}}{3L_{w}-2v_{w}}\leq\theta\leq\arctan\frac{I_{V_{1}- PD}}{L_{w}}\). In addition, it can also be obtained that \(D_{NLOS,1,case2}^{V_{1}-M}=\frac{I_{V_{1}-M,1,case1}}{\sin\theta}\) and \(D_{NLOS,1,case2}^{M-PD}=\frac{I_{M-PD,1,case2}}{\sin\theta}\). According to (10), (A8), and (A9), the average path loss of the NLOS link formed by \(M\) from Tx1, consists of two components, respectively:  
\[ \begin{array}{ll}I_{1}&=p_{\textit{case1}}\int_{\delta_{1}}^{ \delta_{2}}\Bigg{\{}\Bigg{[}\frac{{A_{M}}^{2}\left(I_{V_{1}-M,1,case1}\right) ^{2/\varepsilon}}{\zeta^{2}\left(D_{NLOS,1,case1}^{V_{1}-M}\right)^{2+2/ \varepsilon}}\Bigg{]}\Bigg{[}\frac{{D_{R}}^{2}\left(I_{M-PD,1,case1}\right)^{ 2/\varepsilon}}{\zeta^{2}\left(D_{NLOS,1,case1}^{M-PD}\right)^{2+2/ \varepsilon}}\Bigg{]}\\ &\times e\end{array} \Bigg{.}\Bigg{. }f_{\Delta}(\delta)d\delta,\] (A10)  
and  
\[ \begin{array}{ll}I_{2}&=p_{\textit{case2}}\int_{\theta_{1}}^{ \theta_{2}}\Bigg{\{}\Bigg{[}\frac{{A_{M}}^{2}\left(I_{V_{1}-M,1,case2}\right) ^{2/\varepsilon}}{\zeta^{2}\left(D_{NLOS,1,case2}^{V_{1}-M}\right)^{2+2/ \varepsilon}}\Bigg{]}\Bigg{[}\frac{{D_{R}}^{2}\left(I_{M-PD,1,case2}\right)^{2 /\varepsilon}}{\zeta^{2}\left(D_{NLOS,1,case2}^{M-PD}\right)^{2+2/ \varepsilon}}\Bigg{]}\\ &\times e\end{array} \Bigg{. }-c_{\varepsilon}(D_{NLOS,1,case2}^{V_{1}-M}+D_{ NLOS,1,case2}^{M-PD})^{2}\Bigg{.}\Bigg{.}\Bigg{.}\Bigg{. }f_{\Theta}(\theta)d\theta,\] (A11)  
where \(p_{\textit{case1}}\) and \(p_{\textit{case2}}\) denotes the probability that Tx1 located to the left or right of the center axis of PD. Since the value of \(\varepsilon\) is small enough, assuming that \(\Bigg{(}\frac{{D_{R}}}{\xi\left(D_{NLOS,1,case}^{V_{1}-M}+D_{NLOS,1,case}^{M- PD}\right)}\Bigg{)}^{\varepsilon/2}\approx\frac{{D_{R}}}{\xi\left(D_{NLOS,1, case}^{V_{1}-M}+D_{NLOS,1,case}^{M-PD}\right)}\). Then, simplify and integrate Equations (A10) and (A11) as follows:  
\[