Why is the file copy speed over wireless so slow?

First of all, most desktop computers aren't capable of copying files faster than 15-20 MB/s (mega bytes, big B) or 120-160 Mb/s (mega bits, little b). The upper limit is due to a combination of hard disk speed, I/O bus bandwidth, available memory, and most importantly, processor usage and disk activity from other programs. In particular, if you have a virus scanner that has a "scan on access" feature (on either end), that will kill throughput.

Secondly, and most obviously, your router configuration and wireless signal quality can have a significant impact on throughput.

Thirdly, what you are transferring makes a difference too. One big file will generally transfer faster than a zillion small files (of equivalent size).

Possible reasons:

• Your router might be operating in mixed mode, and not actually operating in 802.11n mode.

• There might be interference from another nearby wireless router. Try adjusting the channel.

• You might not be close enough to the wireless router to get a good signal.

• Other traffic might be competing on your LAN or WLAN. If you are running Bittorrent, for example, it can slow down local transfers.

• Remember that 300Mbps (megabits per second) is equivalent to 37.5MBps (megabytes per second). Make sure you are not confusing these measurements.