I would like to evaluate the asymptotic value of the following sum:
$$\frac{1}{2^N}\sum_{n=0}^{N} \binom{N}{n} \log_{2} \binom{N}{n}$$$$f(N)=\frac{1}{2^N}\sum_{n=0}^{N} \binom{N}{n} \log_{2} \binom{N}{n}$$
This is related to the computation of the Shannon entropy. Any help would be greatly appreciated!