CSMA/CA

Question 1

What does CSMA/CA stand for?

Answer 1

Carrier sense multiple access / collision avoidance

Question 2

What does RTS/CTS stand for?

Answer 2

Request to send / clear to send

Question 3

How is data broadcast using wifi?

Answer 3

It’s broadcast over a number of channels which each uses a different frequency.

Question 4

What is the implication/limitations of using channels over wifi?

Answer 4

• They have certain size or range, each channel is 22 MHz in size
• The range can also overlap or bleed through into the next channels range, this is mostly coped with by filtering

Question 5

What are the steps for CSMA/CA with RTS/CTS?

Answer 5

1) First it checks if the channel is idle
2) If a signal is detected it waits a random amount of time and checks again
3) If it is, it sends a Request to Send
4) It waits for a Clear to Send from the WAP
5) If received, it sends it’s message

Question 6

What is the hidden node problem and how is it solved?

Answer 6

• When 2 nodes can be heard by the WAP but not each other

- the clear to send message solves this