Table 1 Strategies under consideration

Uniform distribution for P _UX

${\text{SM}}_{\mathcal{X},\overline{P_{\mathit{\text{UX}}}},\overline{P_X}}$

P _UX s.t. $\sum _{i,j}{p}_{i,j}=1$

Symbol locations: M-PAM

${\text{SM}}_{\overline{\mathcal{X}},P_{\mathit{\text{UX}}},P_X}$

${\text{SM}}_{\mathcal{X},P_{\mathit{\text{UX}}},P_X}$

P _UX s.t. $\sum _{i,j}{p}_{i,j}=1$

P _UX s.t. $\sum _i{p}_{i,j}=\frac{1}{M}$

Symbol locations: M-PAM

${\text{SC}}_{\overline{\mathcal{X}},P_{\mathit{\text{UX}}},\overline{P_X}}$

Uniform distribution for P _X

Uniform distribution for P _X

${\text{SC}}_{\mathcal{X},P_{\mathit{\text{UX}}},\overline{P_X}}$

P _UX s.t. $\sum _i{p}_{i,j}=\frac{1}{M}$

P _UX s.t. $\sum _{i,j}{p}_{i,j}=1$

Symbol locations: M-PAM

${\text{SC}}_{\overline{\mathcal{X}},P_{\mathit{\text{UX}}},P_X}$

${\text{SC}}_{\mathcal{X},P_{\mathit{\text{UX}}},P_X}$

P _UX s.t. $\sum _{i,j}{p}_{i,j}=1$