2015-02-01

WiFi speeds or why I don't get 300Mbps from my router

I have a linksys E900 (802.11n) router .For many years before that I have used WRT54GL(802.11g).
Usually on all router boxes you see that:

802.11g - is limited to 54Mbit/s
802.11n - 300Mbit/s (sometimes 150, or 600 it depends)

On the other hand I bought an expensive HP ENVY 15-j105en laptop, which is equipped with 802.11ac, which 802.11ac according to the many ads is capable of speeds over 1200Mbit/s.

Of course I thought that the speed between my router and the laptop will be 300Mbit/s.
Well it was only 72Mbit/s

WHY?

I don't want to explain all the story and everything I went through to understand the simple truth.
Wikipedia saved me after a lot of hours and chatting with Linksys support.
This table explains it all - http://en.wikipedia.org/wiki/IEEE_802.11n-2009#Comparison

The big difference is that 802.11g is not able to use the so called MIMO streams. So usually it transmits through one antenna, and receives through one antenna.
If you keep the same set-up -> one-one and switch to 802.11n actually the speed won't go much higher - only 72Mbit/s.

BUT

There are two ways 802.11n reaches higher speeds - the router uses 2 (or more) antennas , and if the laptop has 2 antennas you get double speed - 150Mbit/s (300Mbit/s for 4 antennas).
The second way is that the router tries to use 40Mhz channel width to communicate with the laptop, which in case of one-one antennas doubles the speed.
So my router, having 2 antennas AND utilizing 40Mhz channel can reach 300Mbit/s.

According to the specifications, my laptop HAS 2 antennas, and of course is able to communicate on 40Mhz wide channel. Then why am I getting only 72Mbit/s?

FURTHER

40Mhz kill - actually 40Mhz wide channel can be used if there is a clean wi-fi spectrum. Since I am living in a block I see more than 15 other routers around. So when I start my router it gets 40Mhz channel for a few seconds, meanwhile the laptop is connected on double speed 150Mbit/s. But after that it switches back to 20Mhz channel width, and the laptop back to 72Mbit/s.
2 antennas kill - OK but what about the 2 antennas? I still should be able to get 150Mbit/s because of the antennas. According to the ENVY specifications on HP website, and my local dealer website it has 2x2 antennas. Taking a closer look in the device manager, I saw that my laptop is equipped with AC 3160, which has only 1 antenna.
And that folks, describes why I have only 72Mbit/s having a fine router and a good laptop!

So watch carefully, choose an ENVY with AC 7260 or similar which has 2x2 antennas.
I will upgrade it soon.

Regards



P.S.
I recommend reading THIS






-=Update 20.Aug.2016=-

I successfully upgraded my laptop with AC7260. It was 20 GBP from ebay. It worked like a charm on WIndows 10, even didn't ask for drivers.

You have to be careful though,  read the seller review, not all boards are HP laptops compatible.
The speed is really good and stable. Here is the result: