The problems of maximum number of codewords for binary constant weight codes are studied by employing the theory of Johnson Schemes.In Delsarte's association schemes theory
Q-transform were introduced to study the distance distributions of binary constant weight codes.First
we study the Q-transforms of distance distributions of binary constant weight codes. Then
by using the properties of Q-transforms
we obtain a new upper bound of number of codewords for binary constant weight codes.This bound is similar to Grey-Rankin bound in error-correcting codes theory in form and improves previously known results in certain cases.