Introduction to Networking

CSMA With Collision Avoidance (CSMA/CA)

CSMA/CA is used in wireless (Wi-Fi) networks. CSMA/CA is similar to CSMA/CD, but the difference is that the CSMA/CA detects collision instead of detection. So, CSMA/CA is just used for collision avoidance.

Working with CSMA/CA

In CSMA CA, whenever a station sends a frame to a channel

  • First, it checks the status of the medium (idle or busy). If the medium is busy, the station waits until the medium becomes idle.
  • Second, if the channel is idle, then the station waits for an Inter-frame gap (IFG) amount of time and then sends the frame.
  • Third, after sending the data frame, CSMA/CA sets a timer.
  • In the end, the station waits for positive acknowledgment from the receiver. If positive ACK is received before the expiry of the timer, then it is a successful transmission. Otherwise, the station waits for a back-off time period and restarts the transmission.

Flow Chart

A descriptive flow chart of CSMA/CA is given below

Difference Between CSMA/CD and CSMA/CA

S. No CSMA/CD CSMA/CA
1.  It detects the collision on a shared medium. CSMA CA is used to avoid collision on a shared channel.
2. It is the collision detection protocol. It is the collision avoidance protocol.
4. It works in wired networks, i.e. (802.3 Ethernet network cable) It works in wireless networks (i.e., Wi-fi).
6. It uses the collision signals to resend the data. It uses the timer to resend the data.
7. It minimizes the recovery time. It minimizes the risk of collision.
8. The efficiency of CSMA/CD is higher than CSMA. The efficiency of CSMA/CA is similar to CSMA but less than CSMA/CD.
9. It is more popular than CSMA/CA. It is less popular than CSMA/CD.