$A^T$, $A^{-1}$, $A^H$	the transpose, inverse and conjugate transpose of $A$, respectively.
$\Vert A\Vert$	$l_2$ norm of matrix $A$
$\left|a\right|$	the absolute value of $a$
$\mathrm{Re}\left\{a\right\}$	the real part of $a$
$\mathrm{Im}\left\{a\right\}$	the imaginary part of $a$