What should be the transfer speed in N standard?

hi.
I would like to know what should be the speed when I transfer files through my wireless network.

I've noticed that when I copy files, the speed is about 8MB/s and sometimes drops below.
Does it have something to do with the reception percentage? Can I improve the transfer rate?

There are many factors, signal strength being only one. The data throughput rate of the wireless router, the link speed to the other device (or internet), the capability of the server you are getting data from, etc. You could be operating at maximum speed on the link between your PC and the wireless router but that is only the wireless link, it's not the "total picture".

Another example is the link speed of your ISP link. You may have, for example a fast 30Mb/sec downlink speed but that is ONLY the speed from the ISP to the modem, nothing else.

I think I'm right in saying also that distance can also play a big part in the speed difference between G and N - the greater signal strength (in distance covered) provided by N can sometimes mean a lower speed compared to that of G. It's a trade off - sometimes.

My computers are 7 meters apart. I'm talking about copying a file in WLAN, i don't care about internet speed, simply the file speed between two computers in the same wireless network.

fair enough, I thought the same rules would apply over wireless. Apologies.

As someone else said, many many factors come into play. One I have seen make a huge impact is encryption. Some devices don't play well on one type of encryption. A while back I had a router that worked best on WEP, and a machine that wanted WPA2, so they never played nicely together. Shutting off encryption entirely made it 3 times faster.