450mbps wifi speed

hello,

i would like to know, how fast SGS3 can connect to my cisco e4200 n router that advertise 450mbps throughput ..

i'm trying to get 450mbps connection to my router..
on my router i setup wireless n and wireless bg network..
when i connect to 2.4g network i get 75mbps connection 1m away from router.
the same speed i get when i connect SGS3 to 5ghz network..

what i'm doing wrong?

thx
by
kikan