Table 4 Best relay selection criterion for AF scheme

${\gamma }_{S_j{R}_l}<\frac{{\gamma }_{R_{l}D}}{2}<{\gamma }_{R_{l}D}$

$\underset{l}{\text{max}}\left({\gamma }_{S_j{R}_l}\right)$

$\underset{l}{\text{max}}\left({\gamma }_{S_j{R}_l}\right)$

Same

$\frac{{\gamma }_{R_{l}D}}{2}<{\gamma }_{S_j{R}_l}<{\gamma }_{R_{l}D}$

$\underset{l}{\text{max}}\left(\frac{{\gamma }_{R_{l}D}}{2}\right)$

$\underset{l}{\text{max}}\left({\gamma }_{S_j{R}_l}\right)$

Different

$\frac{{\gamma }_{R_{l}D}}{2}<{\gamma }_{R_{l}D}<{\gamma }_{S_j{R}_l}$

$\underset{l}{\text{max}}\left(\frac{{\gamma }_{R_{l}D}}{2}\right)$

$\underset{l}{\text{max}}\left({\gamma }_{R_{l}D}\right)$

Different