Tuesday, June 7, 2011

Wireless N issues


Recently I bought a new wireless N router, the Linksys E1500 to improve my home wireless network.  In this blog I talk about my experiences with it and things I learned to maximize its use.

My previous network consisted of a wireless router+modem provided by ATT ar part of the U-verse upgrade.  The ATT router supported "G" speeds.  It was working fine but I have been observing some throughput issues occasionally while viewing videos from the internet.  Couple this with the fact that I want to move to the next speed tier (12 Mbps from 6 Mbps), I thought it would be a good idea to do the upgrade.  I was also encouraged by the fact that my last upgrade from B to G was very pleasant - I could visibly see the difference while connecting to the internet.  So here is a summary of why I wanted to do the upgrade:
* IP telephony (need for QoS)
* Upgrade to higher speed tier (12 Mbps) internet connection
* Expected improvement in browsing and video streaming
* Expected improvement in internal network performance (PC-to-laptop, etc).
* Added a video camera for surveylence - uses QoS

The upgrade procedure was trivial, and immediately I saw significant improvement while loading pages - Yahoo portal loaded in one second vs several.  The prior bottleneck could have been in the wireless side of the ATT router, or the G channel itself.  Anyways, I am now past it.

Then I ran into one minor and one major problem.  The minor one was that on my laptops (Lenovo T400 and MacBook Air) I would only see link speeds of 144Mbps or so - not 300 as claimed by the advertizing literature.  I considered it minor because link speed of 144M itself is good enough for me.

The bigger problem was my desktop, which has the ASUS PCE-N13 PCI express card capable of N speeds (up to 30 Mbps), sitting on floor with antenna at the back.  Between the antenna and the router are about three walls and a door, and the PC's metal case.

I found that after switching to N, the PC became very slow - stuttering mouse, extremely slow page loads - maybe worse than dial-up.  Something was obviously wrong from the PC side.  So I tried to scan for viruses, tweaked some network parameter (See my other blog) and played around with wireless setting on both ends.  Nothing really helped.  I upgraded the drivers and that fixed the stuttering, but the speeds were still dismal.  I ran internet speed tests from my Lenovo and the PC from the same spot and saw download speeds of 5.7 Mbps from the PC and bets case of around 3 Mbps from the PC - consistently.  Restricting the channel width to 20MHz (as apposed to allowing 20 and 40) from the router helped in stability of the PC-router link (otherwise the link was also very unstable - kept disconnecting).

Finally I moved the PC around a bit, as well as the router.  Things seem to change favorably.  I proceeded down the signal strength path and finally got the PC to work.  Here are the exact things I did to make it work:

* Moved the router into the same room
* Turned the PC box such that the two ends are in line-of-sight - only air in between (or occasionally my body)
* Changed the PC card's setting to enable "CAM".  Don't know what it is my somewhere on the web I was this in relation to ralink/PCE-N13 settings.

I got the download speeds (from PC) to be back to 5.7 Mpps again!  Hooray!  I then re-enabled 40 MHz b/w on the router.  Lo and behold!  I saw 300 Mbps link speed on my laptop.  Alas, the PC peaked at 150Mbps.  Of course internet access is superb.

I can now look forward to upgrading my internet speed to 12 Mbps.  You may say "even with G it makes sense for 12Mbps to work".  Theoretically yes, but my experience in moving from G to N says otherwise.  Ideally I should not have seen any difference in browsing, but that is not the case.  While running a speed test may not show a difference, random browsing displays a different behavior.

I found this article to contain material that explains why the above approach worked:

http://www.smallnetbuilder.com/wireless/wireless-basics/30664-5-ways-to-fix-slow-80211n-speed

I will next try out the WMM trick and see if that helps the PC case.  Will update this blog later...

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