$($a$)$ Define each of the following terms with respect to multiplexing:

$($i$)$ guard bands; $$ bands which quard data during multiplexing

$($ii$)$ channel; $$ is the Path where data pasres

$($iii$)$ pulse stuffing. $=>$

$(3$ marks$)$

$($b$)$ With the aid of a diagram, describe the principle of Wavelength Division Multiplexing $($W$.$D$.$M$).$

$(6$ marks$)$

$($c$)$ Ten data terminals, each transmitting at $9600bps$ are multiplexed using time division multiplexing $($TDM$).$

$($i$)$ determine the total capacity required for synchronous TDM;

$9600bp10=96000b$ s

$($ii$)$ if the link utilization is $0\mathrm{.}8,$ using statistical TDM determine the:

I. data rate that can be supported; $0\mathrm{.}89600=7680bps$

II$.$ number of terminals that can be supported.

$(6$ marks$)$

$0\mathrm{.}810=8$ terminals

$($d$)($i$)$ Define flow control in data communication.

Requiation of data frorement

$($ii$)$ Describe stop and wait flow control protocol as used in data communication.

$(5$ marks$)$