Single Parity Check Code The check bit is 1 if frame contains odd number of 1s otherwise it is o 1011011->10110111 1100110->11001100 Thus, encoded frame contains even number of 1's Receiver counts number of ones in frame An even number of 1s is interpreted as no errors An odd number of 1's means that an error must have occured a single error ( or an odd number of errors)can be detected An even number of errors cannot be detected Nothing can be corrected Probability of undetected error(independent errors) N acket size i even p=error probSingle Parity Check Code • The check bit is 1 if frame contains odd number of 1's; otherwise it is 0 1011011 -> 1011011 1 1100110 -> 1100110 0 • Thus, encoded frame contains even number of 1's • Receiver counts number of ones in frame – An even number of 1’s is interpreted as no errors – An odd number of 1’s means that an error must have occured A single error (or an odd number of errors) can be detected An even number of errors cannot be detected Nothing can be corrected • Probability of undetected error (independent errors) P u ndet ected) = ∑   N  pi (1 − p ) N −i N = packet size ( i even  i  p = error prob