Data transmission

Question 1

Odd parity check

Answer 1

The number of 1 s/0 s are counted
A parity bit is added to each byte/7 bits before transmission to make the sum of the bits/1 or 0 s in each byte odd
After transmission, if the number is odd no error is detected
After transmission, if the number is even an error is detected

Question 2

ARQ

Answer 2

Timer is started when sending device transmits a data packet to receiver
Receiving device checks the data packet for errors
Once the receiving device knows the packet is error free it sends an acknowledgement back to the sending device, and the next packet is sent

If the sending device does not receive an acknowledgement before the timer ends and a timeout occurs
So the data packet is resent until acknowledgement is recieved or max attempts reached