I think it is not normal when access point shows me data rates 54 mbs tx and 72 mbx rx.
Does that mean that my smartphone download conects in 802.11g and upload in 802.11n ?
How is that posible ?
802.11g and n are similar enough that radios will just as happily select a G rate as an N rate. Nothing is weird about that; for some reason the AP determined it has less packet loss at 54 Mbps than other rates, while the station settled on 72 Mbps. You can manually disable G rates if you want in the advanced wireless settings (but leave 6 Mbps as a basic rate for broadcasts; at least, I've had trouble since I think some clients expect it).
Also, depending on channel width, there are some N and AC rates that are 54 Mbps. You can tell the difference in the registration table because the N and AC rates include the channel width and number of streams; G (and B) rates do not.