How to change wifi type in OpenWrt?

Question

WiFi

There is a tpl-wr842nd router. Installed OpenWrt 14.07 on it. Everything works fine, on the desktop connected to the router via a cable, honest 50 Mbps come from the rights provider. But on a laptop, via wifi - no more than 20Mbps. The laptop is 1m away from the router. I got into the settings to understand, but I noticed a strange feature. Among the available wifi operating modes, there is only one: "2.4 GHz (802.11g + n)". The laptop is fresh, n-standard supports. Please tell me how to make the router work only in the "-n" standard?

Answer 1

40 megahertz must be forced to set, then you can get 40 megabits. Probably, the laptop has 1 antenna and a maximum speed of 150 megabits?

Answer 2

20 megabits is not even half the g standard. Even the first draft n should draw at least 100. And then there are 2 antennas, i.e. in theory up to 300. And then, I say, everything was ok with another router, i.e. The laptop can run at normal speed. According to this - the bottleneck is a router.
You can raise the channel width, but the question is not how to increase the speed. And how to change wifi technology from g to n in OpenWrt 14.07 firmware.