I am in desperate need of help to improve the abysmal performance of my 802.11n wireless network. At best I get 30Mbs (this is an internet download) from a technology that boasts 300Mbs, even worse is the LAN where to date the best I have ever gotten is 1Mbs. It is literally quicker to copy the file to a USB drive and walk it to the other computer.

Infrastructure is this

• AP 802.11n only broadcasting at both 2.4GHz and 5GHz
• Mac with 802.11a/b/g/n card is connected to the AP via 5GHz
• Linux with 802.11a/b/g/n card is connected to AP via 2.4GHz

I have conducted the following tests (results at end of post)

• Internet based speed test wired and wireless
• LAN file copy wired and wireless

I have read:

• Wireless Diagnostics & Troubleshooting: Handheld And PC-Based Tools For RF And Wi-Fi Diagnostics
• 5 Ways To Fix Slow 802.11n Speed
• 7 Tips to Increase Wi-Fi Performance
• Slow file transfer on network between two 802.11n laptops (connected directly together via access point)
• Wireless Network Performance Issues
• Slower than expected 802.11n wireless network speeds

I have made the following optimizations

• AP broadcasts only 802.11n on both 2.4GHz and 5GHz frequencies
• 2.4GHz is on a channel with least interference (live in an apartment with lots of APs), this did make a 10Mb/sec improvement
• Our AP is the only one transmitting on the 5GHz freq.
• Security: WPA Personal WPA2 AES encryption
• Bandwidth: 20MHz / 40MHz (I assume this to be channel bonding)

I have tried the following with 0 improvement

• Dropped the Fragment Threshold to 512
• Dropped the Request To Send (RTS) Threshold to 512 and 1
• Even thought of buying a frequency spectrum analyzer, until I saw the cost of them!!!

Speed test results

Linux Wired:

• DOWNLOAD 128.40Mb/s
• UPLOAD 10.62Mb/s
• http://www.speedtest.net/my-result/2948381853

Mac Wired:

• DOWNLOAD 118.02Mb/s
• UPLOAD 10.56Mb/s
• http://www.speedtest.net/my-result/2948384406

Linux Wireless:

• DOWNLOAD 23.99Mb/s
• UPLOAD 10.31Mb/s
• http://www.speedtest.net/my-result/2948394990

Mac Wireless:

• DOWNLOAD 22.55Mb/s
• UPLOAD 10.36Mb/s
• http://www.speedtest.net/my-result/2948396489

LAN NFS 53,345,087 bytes (51MB) file

• Linux Mac NFS Wired: 65.6959 Mb/sec
• Linux Mac NFS Wireless: .9443 Mb/sec

All help is appreciated, even testing methods will be accepted.

Sometimes you may have other devices using 2.4Ghz causing interference. Not sure if you have tried using a scanner to see if some other device is interfering. I've found this to be the case at my job where I had a similar situation and there was a telephone using 2.4Ghz that caused slowdowns.