  For a d-dimensional cellular automaton with d $\ge$ 1 we introduce a rescaled
entropy which estimates the growth rate of the entropy at small scales by
generalizing previous approaches [1, 9]. We also define a notion of Lyapunov
exponent and proves a Ruelle inequality as already established for d = 1 in
[16, 15]. Finally we generalize the entropy formula for 1-dimensional
permutative cellular automata [18] to the rescaled entropy in higher
dimensions. This last result extends recent works [17] of Shinoda and Tsukamoto
dealing with the metric mean dimensions of two-dimensional symbolic dynamics.
