Question $3$

$($a$)$ Briefly discuss the main difference between Frequency Domain Multiple Access

$($FDMA$)$ and the Code Division Multiple Access $($CDMA$)$ as used in cellular

telephony.

$($b$)$ An $802\mathrm{.}11$ ax wireless router is using multiple antennas:

$($i$)$ What is the space diversity gain?

$($ii$)$ Explain why multiple input multiple output $($MIMO$)$ systems can potentially

increase the throughput compared to single input single output $($SISO$)$

systems.

$($iii$)$ Assuming a system employing $t=8$ transmitters and $r=8$ receivers, what is

the maximum achievable increase in channel capacity compared to the

respective SISO system?

$($c$)$ With the aid of examples and diagrams, describe the three main Automatic Repeat

reQuest $($ARQ$)$ protocols.