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802.11n wireless

There is no end of tekkie stuff to burn your time on. It amazes me how complicated our industry make it for average shmoes and even tekkies like me to get the most out of their products. To this end I submit this blog post on 802.11n. 802.11n existed in draft mode for a very long time. A number of companies jumped aboard the draft standards early. This lead to some not so compatible devices. At this point in time the standard has been ratified for quite a while. I last reviewed my LinkSys E3000 back in March of 2011. Now I have to admit I did not spend a lot of time focussing on use with N. At the time my laptop didn’t support N, nor did my tablet or phone.

Fast forward to now and I have a new laptop My Asus X202 as well as my HTC one and lastly my Q10 all of which support 802.11N. So I decided to take some time and look into why I was not getting much of a speed boost out of my wireless network (compared to G). Using some wireless analysers such as Android Network Signal Info as well as Android WIFI Analyzer, not to mention Windows network status I was able to confirm a link speed no better than 72Mb/s, well below what N ought to be capable of. And so the research began. As usual Wikipedia had a good article describing N. I also found another excellent article on DDWRT. Armed with this information I began to look into my router’s settings.

Frequencies
So let’s start out with some simple stuff, and I will try to keep it as simple as I can. More technical stuff can be found in the above two articles if you so choose. First and foremost 802.11n can be implemented in two different bands 2.5GHZ and 5GHZ. Not all 802.11N adapters (as well as routers) support both frequencies (some only support 2.5GHZ). My Asus has a broadcom and it only support 2.5GHZ while the HTC One and Q10 both support 2.5 as well as 5 GHZ. I changed the SSID on the router for the 2.5 and 5 GHZ so I could easily see who had what bands. If yours don’t have the 5 GHZ band then you might as well turn it off on the router and save the radiation :). 5GHZ is MUCH more limited in range. You will see this in lower signal strength from the same router. Both 5GHZ as well as 2.5GHZ have older legacy 802.11 standards in the same frequency band. 2.5GHZ covers B/G/N and 5GHZ supported both A/N (although very little 802.11A was shipped IMHO). In both cases the presence of legacy devices can impact the speed you will get from your network. To the point that you may want to setup a separate router for those legacy devices. You do not have to have 5GHZ to get the max speed out of 802.11N

Channel width
One of the tricks 802.11N uses to bump the network speeds is to use two channels. One of the first places to check is to see if your router is set to use 1 channel (20MHZ) or two (40MHZ). For my router you could set it separately for 2.5 and 5GHZ.
80211n-1
When I checked the wireless status screen on the router I saw that it was only doing single channel which explained the 72Mb/s speed.
80211n-2
Other routers in the area (as well as Bluetooth, DECT cordless phones) can all make 2 channel mode impossible. To get the router to stay in two channel mode I had to take it off auto channel and choose a channel where there was 2 free channels. I played with the channels until I found one where the router stayed in 2 channel (40MHZ mode). The router’s wireless status screen was helpful to see that I finally got it right.
80211n-3

Next up you need to focus on the wireless security you have chosen. From the DDWRT site I quote:
“You MUST use WPA2 authentication with AES encryption only, or use no security at all if you wish to achieve N rates. Anything else is against the N spec and typically results in the client falling back to G rates.”

Even with all this right I was unable to get more than 72 Mb/s or a single channel out of the 2.5GHZ band. I worked this with a Linksys E3000 as well as a DLINK DIR 501 router. From a client point of view I was using the wireless Broadcom card in my ASUS X202, my HTC One phone and my Samsung Galaxy Tab 2 7 plus. In the 5 GHZ band using my HTC one I was able to get link speeds up to 150Mb/s standing right beside the router. I was also able to confirm doubling of the bandwidth when I got the 150 Mb/s. Using AND FTP connected to an FTP server in my home (don’t use an SFTP protocol, the processors in Android phones really does not do SSL well) I got 9MB/s when I got double channel 150 Mb/s link (big B means byte, little b means bit, multiple b x8 to get B) and around 4.5 MB/s when I got a link of 72 Mb/s link. I max out at 72 Mb/s link on SFTP at around 1.5 MB/s. See what I mean about SFTP being super slow on Android. So translating on a 150 Mb/s link I got 72 Mb/s actual data rate.

So I was about to give up when in comes my girl friend with her laptop a Lenovo Flex 15 which has an Intel N 7260 wirelss N card. Without changing a thing on her laptop it linked up at 2.5GHZ, dual channel 144 Mb/s. And I was able to clock out 100 Mb/s data rate. Wow. So all in all it seems to be a combination of sender and receiver. And when the stars line up and the moon aligns with venus you get a decent wireless rate. Grrrrr….

With my S4 I was able to measure a 9% increase in standby power when connected to 5G Vs 2.5G. So there is some price to pay for the potentially faster speeds of 5G.

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April 2, 2014 - Posted by | Android, Blackberry 10, Electronic gadget reviews

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