Improved sphere bounds on the covering radius of codes
G.J.M. van Wee · IEEE Transactions on Information Theory · 1988
The sphere bound is a trivial lower bound on K(n,R), the minimal cardinality of any binary code of length n and with covering radius R. By simple arguments it is considerably improved, to K(n,1)>or=2/sup n//n for n even. A table of lower and upper bounds on K(n,R) for n>