MULTIPLE ACCESS PROTOCOLS: COLLISIONS

Consider the figure below, which shows the arrival of $5$ messages for transmission at different multiple access wireless nodes at times

and each transmission requires exactly one time unit.

QUESTION LIST

Suppose all nodes are implementing Carrier Sense Multiple Access $($CSMA$),$ but without collision detection. Suppose that the time from when a

message transmission begins until it is beginning to be received at other nodes is $0\mathrm{.}4$ time units. $($Thus if a node begins transmitting a message at

$t=2\mathrm{.}0$ and transmits that message until $t=3\mathrm{.}0,$ then any node performing carrier sensing in the interval $[2\mathrm{.}4,3\mathrm{.}4]$ will sense the channel busy.$)$ For

each message, indicate the time at which each message transmission begins, or indicate that message transmission does not begin due to a

channel that is sensed busy when that message arrives. Separate each value with a comma and no spaces, and if the channel is sensed busy,

substitute it with $\text{'}$s$\text{'}$

Which messages transmitted successfully? Write your answer as a comma seperated list with no spaces using the messages' numbers

SOLUTION

The list of times for frame transmissions is: $0\mathrm{.}2,s,2\mathrm{.}4,s,4\mathrm{.}2$

The list of successful frames is: $1,3,5$

Can I get explantion of how to do this type of problem. Thank you.