For Project 3, there are matlab examples on old class web pages. Error Detection Powers. Used when the character length is 6 bits.
Receiver receives frames and detects frame transmission errors.
If an error is detected, the receiver requests another copy of the frame. If the transmitter receives an ACK it sends the next frame. If the transmitter receives a retransmission request it re-sends the previous frame. Generally being phased out for Continuous RQ protocols. Sender waits for an ACK from the receiver.