For wireless networks answer the following

$($a$)$ What does it mean for a wireless network to be operating in infrastructure mode?

$($b$)$ What is the difference between path loss and interference on a wireless channel

$($c$)$ What are the $802\mathrm{.}11$ based interframe spacing variables and what are they used for?

$($d$)$ What is the difference between an ESS and a BSS in the IEEE $802\mathrm{.}11?$

$($e$)$ What is the difference between a probe and a beacon signal in $802\mathrm{.}11?$