Effectiveness of error detection technique Effectiveness of a code for error detection is usually measured by three parameters 1)minimum distance of code(d(min bit errors undetected) The minimum distance of a code is the smallest number of errors that can map one codeword onto another. If fewer than d errors occur they will always detected. Even more than d errors will often be detected (but not always! 2)burst detecting ability B)(max burst length always detected) 3 probability of random bit pattern mistaken as error free(good estimate if errors in a frame >>d or bl Useful when framing is lost K info bits =>2 valid codewords ith r check bits the probability that a random string of length k+r maps onto one of the 2k valid codewords is 2/2K+T= 2-Effectiveness of error detection technique • Effectiveness of a code for error detection is usually measured by three parameters: 1) minimum distance of code (d) (min # bit errors undetected) The minimum distance of a code is the smallest number of errors that can map one codeword onto another. If fewer than d errors occur they will always detected. Even more than d errors will often be detected (but not always!) 2) burst detecting ability (B) (max burst length always detected) 3) probability of random bit pattern mistaken as error free (good estimate if # errors in a frame >> d or B) – Useful when framing is lost – K info bits => 2 k valid codewords – With r check bits the probability that a random string of length k+r maps onto one of the 2 k valid codewords is 2 k/2k+r = 2-r