Help! Sudden poor performance

[IIfx]

Hello,

Recently I have experienced a massive drop in performance on my WLAN. Performance is fine on the Gigabit LAN.

After performing basic troubleshooting on my Netgear WNR3500L (different computers, settings) I had decided that it had burnt out after 2 years. So, I bought another one since it had been great.

Well...the performance woes continue. Bandwith is pathetic - 300kbit/sec or less, with full signal right next to the router. My suspicion is that there is heavy interference suddenly as I live in a townhouse.

I even tried different operating systems on the routers (Stock, DD-WRT, and Tomato) to no avail. All my PCs and smartphones have the same issue. I also changed every setting possible - no change.

Here is a screenshot showing all the networks in my area (C&P Telephone is mine)
http://i.imgur.com/FWsGl9N.png

Any help would be greatly appreciated.

 

[stevech]

We assume that you tested to prove the fault does not lie with the client device!

-16dBm is super strong, as if the AP/Router is 3 ft away.
-51 is very good too.
the 3rd one is apparently quite weak, or is transmitting infrequently. Is this the one in question?

Remember too, your survey tool is showing you only the signal strengths FROM APs/routers. It isn't showing the signal strength at the router, FROM client devices.

 

[IIfx]

I can confirm that the fault does not lie with the devices tested. I tried my ThinkPad x230 (Intel Wireless N 2200), my iPhone 4, a ThinkPad T400 with Intel Wireless N, a Macbook Pro with AirPort Extreme, and an HP laptop with Wireless N. The testing was performed right next to the router, or a few feet away.

There were no issues with bandwidth until recently, when my last WNR3500L died. The new one seems to not be as good as the old one although the situation has improved since my first post the wireless connection is still slow. It seems the clients are not syncing at the full Wireless N speed, instead locking on at 54mbps. Only 1/2 of the bandwidth provided by my ISP is available over Wireless (10mbit instead of the full 25mbit which I can get over Ethernet)

 

[stevech]

tried changing channels among 1, 6 or 11?
Do you know about the issue of mixing 11g and 11n WiFi on the same channel, even if the 11g system isn't yours?

 

[IIfx]

I have already tried channels 1, 6, and 11 with no change.

The issue of foreign G devices not on my network is known but it was not an issue in the past, my previous WNR3500L did not have any issues until its wireless radio died.