Please clearly answer the following problem in a systematic way.

$($a$)$ In OFDM design, explain the relationship and tradeoff between number of carriers, multipath, and

mobility. Clarift it over time and frequency domains,

$($b$)$ What is two main source of the inter symbol interferences$($ISI$)$ of wireless channels?

$($c$)$ The IEEE $802\mathrm{.}3$ standard$($Ethernet$)$ uses CSMA$/$CD for media access control, whereas the $802\mathrm{.}11$ uses

CSMA$/$CA$.$ It is possible to use CSMA$/$CA on wired medium also. If you use your LAN mostly for

transferring streaming media such as video, audio, and real$-$time data such as multi$-$player game data,

which media access control protocol tou use? and Why?