csma/ca

[jonk34567]

1 half-duplex systems

2 Full-duplex systems

3 Wireless system 

what collison avoidance mechanism are they using ? csma/cd  oe csma/ca

[DaSt-1986]

Half duplex uses CSMA/CD

Full duplex doesn't use any collision avoidance or detection mechanism

Wireless uses CSMA/CA

[syrehan]

1. CSMA/CD is utilized in half-duplex systems to avoid collisions.

2. Full duplex systems don't need CSMA/CD because data can be sent and received at the same time by the communicating entities.

3. Wireless systems utilize CSMA/CA unlike CSMA/CD.

You can read about both CSMA/CD and CSMA/CA by following the below mentioned URLs:

https://en.wikipedia.org/wiki/Carrier-sense_multiple_access_with_collision_detection

https://en.wikipedia.org/wiki/Carrier-sense_multiple_access_with_collision_avoidance

I would however recommend you to keep the CCNA course book with you at all times. It helps a lot for references.
Hope to help!

[Joseph W. Doherty]

As the other posters have already noted, you wouldn't have collisions on full-duplex, so you don't need a CD or CA protocol. However, on some full-duplex systems there are protocols to indicate congestion, such as Ethernet full-duplex flow control.