how can I wifi change to g (54 Mb/s)?

Hi,

got the newest Oleg firmware, but the wifi speed is poor (1,2-1,3MB/s, using locally FTP, same from the Internet), where can I check and change to G mode, via console? (got lighttpd running at port 80, when I stop it, the 192.168.1.1 is empty, and can't do it via www).

Thanks in advance for help!