I would like to prove that this lower bound of exists a code with parameters n,M,d} (where n is the length of the block code, M the number of words of the code, and d, the minimal distance of the code), holds:
For trying to see this, I have tried to connect this inequality with the cardinal of the ball of radius , that is , so for sure, that quantity is less than . But I don't see if this is or not helping me at all... I would appreciate some guidance, help, hint,... Thanks!