I have built a file server for my home network. It has a 3TB Sata 3Gb/s HDD on a Dual Celeron Mini ITX mobo with 2GB DDR3 RAM. I have installed Ubuntu minimal runing off a flashdrive. I installed samba and configured it with webmin.
I bought a D-Link DSL-2730R router, the specs says it is 10/100 and b/g. I connected the router to the server via ethernet, and configured samba via webmin.
My laptop is in a room next to my router. When transfering files from/to my Ubuntu laptop, I get about 1,5MB/s on Nautilus. If I place my laptop in the same room, 30cm of the router, I get about 2,5MB/s.
I used an android app to check for the wifi channel with less interference and set it to a channel with no other SSIDs on it, and I disabled WPA2PSK and left the wifi open (for a few minutes, just for testing). The speed increased to a peak of 2,8MB/s.
If I disable wifi and connect via ethernet I get speeds aroun 6,6~7,9 MB/s. (All the teste were performed with the same file, a 300MB file).
Then I tried an android app to test local wifi LAN transfer speed and it says my link speed is 54Mbps, signal is -59 dBm, download is 6967Kbit/s and upload is 3545Kbit/s.
According to this answer the top theoretical speed on 802.11g is 6.7MB/s, but I'm getting less than 25% of it.