[0,\pi/M] $ for which $d^2_{\mathcal{C}_{k_i}}(\gamma, \theta) \leq d^2_{\mathcal{C}_{k_j}}(\gamma, \theta) $ where $1\leq j\neq i \leq N_W$, and $d^2_{\mathcal{C}_{k_i}}(\gamma, \theta) \leq d^2_{min}(\mathcal{S})$. The curves $d^2_{\mathcal{C}_{k_i}}(\gamma, \theta)=d^2_{\mathcal{C}_{k_j}}(\gamma, \theta)$, $1\leq i \neq j\leq N_W$, form the pairwise boundary between the regions corresponding to the two distance classes $ \mathcal{C}_{k_i} $ and $ \mathcal{C}_{k_j} $. The curves $ d^2_{\mathcal{C}_{k_i}}(\gamma ,\theta) = d^2_{min}(\mathcal{S})$ form the pairwise boundary between the regions corresponding to distance classes $ \mathcal{C}_{k_i} $ and $ \mathcal{C}_{d_{min}(\mathcal{S})} $. The region $\mathcal{R}_W(\mathcal{C}_{k_i})$ is that region in the wedge $ [0,\pi/M] $ excluding the complex point $ (\gamma_i, \theta_i) $, which is the innermost region bounded by these pairwise boundaries, enclosing the singular fade state $ (\gamma_i,\theta_i) $. For example, Fig. \[fig:8pskregion\] depicts the region corresponding to the singular fade state at $(1,0)$ when both users use 8-PSK signal sets. In the figure, the curve $d_1^2=d_j^2$ refers to the curve $d_{\mathcal{C}_{k_1}}^2(\gamma,\theta)=d_{\mathcal{C}_{k_k}}^2(\gamma,\theta)$, and $d_1^2= 2-\sqrt{2}$ refers to the curve $d_{\mathcal{C}_{k_1}}^2(\gamma ,\theta) = 2-\sqrt{2}$. It is the innermost region (shaded in the figure) in the wedge $ [0, \pi/8] $ bounded by the pair-wise boundaries $d_{\mathcal{C}_{k_1}}^2(\gamma, \theta)=d_{\mathcal{C}_{k_2}}^2(\gamma, \theta),\, d_{\mathcal{C}_{k_1}}^2(\gamma, \theta)=d_{\mathcal{C}_{k_4}}^2(\gamma, \theta),\, d_{\mathcal{C}_{k_1}}^2(\gamma, \theta)=d_{\mathcal{C}_{k_5}}^2(\gamma, \theta)$ and $ d_{\mathcal{C}_{k_1}}^2(\gamma, \theta)=d_{\mathcal{C}_{k_6}}^2(\gamma, \theta) $ surrounding the singular fade state $ 