Cyclic redundancy checks T=M2+R How do we computer the check bits)? Choose a generator string G of length [+1 bits Choose R such that T is a multiple ofG (T=AG, for some A Now when T is divided by g there will be no remainder = no errors All done using mod 2 arithmetic T=M2+R=AG=>M2=AG+r(mod 2 arithmetic) Let r= remainder of m 2/g and t will be a multiple of g Choice of G is a critical parameter for the performance of a crcCyclic redundancy checks T = M 2 r + R • How do we compute R (the check bits)? – Choose a generator string G of length r+1 bits – Choose R such that T is a multiple of G (T = A*G, for some A) – Now when T is divided by G there will be no remainder => no errors – All done using mod 2 arithmetic T = M 2r + R = A*G => M 2r = A*G + R (mod 2 arithmetic) Let R = remainder of M 2r/G and T will be a multiple of G • Choice of G is a critical parameter for the performance of a CRC