local network speed on wrt54gl

Question

I have a bit of a problem that needs some explanation or advice on how to improve if possible.

My setup is the following:

[Interwebz]==cable==[CABLE MODEM]==cat5==[WRT54GL]==2 PCs

Linksys WRT54GL Firmware Version: 4.30.14 build 5, Oct. 26, 2009
PC1 - desktop Windows XP connected to ethernet
PC2 - laptop Windows 7 Ultimate 64bit connected to Wi-Fi

Internet speed is 16 mbit/s (2 MBytes/s) and both PCs are capable of achieving the max download speed.

Problem: Move/Copy files from PC1 to PC2 or vice versa cannot go over 2.5 - 3 MBytes/s

Is there something I can do to increase the speed between PCs on local network or am I limited with something that I cannot see/understand?

Answer 1

You're just hitting the limit of 802.11g. It's a standard from almost a decade ago that maxes out at 54 megabits/sec signaling rate, which, after overhead and conversion from megabits to MebiBytes, translates into a little over 3 MebiBytes/sec.

The rule of thumb for Wi-Fi overhead is that you should be able to get TCP throughput at about 50% of your Wi-Fi signaling rate. This assumes a tool that uses TCP efficiently, such as IPerf. The file sharing protocol and client and server implementations you're using (Microsoft's SMB implementations?) might not use TCP terribly efficiently.

Anyway, if you were reliably getting the 54 megabit/sec signaling rate, you should see TCP throughput of about 27 megabits/sec. Translating that from megabits (1,000,000's of bits; the way we measure network speeds) to MebiBytes (1,048,576's of 8-bit Bytes; the way we measure disk/file copy speeds), yields a little over 3 MebiBytes/sec, which is approximately what you're seeing.

Modern 3-stream 802.11n equipment (which started shipping in 2009), has a maximum signaling rate of 450 megabits/sec, which is over 8x the speed of 802.11g. Time to modernize.

Or maybe if you've waited this long, you can hold out another year and get good 802.11ac equipment (early/immature/bleeding-edge 802.11ac equipment just started shipping in May 2012), with signaling rates up to 1300 megabits/sec.